U.S. patent application number 13/767860 was filed with the patent office on 2013-10-31 for elongated photovoltaic devices, methods of making same, and systems for making same.
The applicant listed for this patent is Benyamin Buller, Erel Milshtein. Invention is credited to Benyamin Buller, Erel Milshtein.
Application Number | 20130284240 13/767860 |
Document ID | / |
Family ID | 41429445 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130284240 |
Kind Code |
A1 |
Milshtein; Erel ; et
al. |
October 31, 2013 |
Elongated Photovoltaic Devices, Methods of Making Same, and Systems
for Making Same
Abstract
Under one aspect, a nonplanar photovoltaic module having a
length includes: (a) an elongated nonplanar substrate; and (b) a
plurality of solar cells disposed on the elongated nonplanar
substrate, wherein each solar cell in the plurality of solar cells
is defined by (i) a plurality of grooves around the nonplanar
photovoltaic module and (ii) a groove along the length of the
photovoltaic module. In some embodiments, each groove of the
plurality of grooves about the photovoltaic module, independently,
has a repeating pattern, a non-repeating pattern, or is helical. In
some embodiments, the module further includes a patterned conductor
providing serial electrical communication between adjacent solar
cells. In some embodiments, portions of the patterned conductor
providing serial electrical communication between adjacent solar
cells are within a groove of the plurality of grooves about the
photovoltaic module.
Inventors: |
Milshtein; Erel; (Cupertino,
CA) ; Buller; Benyamin; (Sylvania, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Milshtein; Erel
Buller; Benyamin |
Cupertino
Sylvania |
CA
OH |
US
US |
|
|
Family ID: |
41429445 |
Appl. No.: |
13/767860 |
Filed: |
February 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12502978 |
Jul 14, 2009 |
8383929 |
|
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13767860 |
|
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61082152 |
Jul 18, 2008 |
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Current U.S.
Class: |
136/251 ;
136/244; 438/73 |
Current CPC
Class: |
H01L 31/035281 20130101;
H01L 31/0392 20130101; H01L 31/022425 20130101; H01L 31/0516
20130101; Y02E 10/50 20130101; H01L 31/0463 20141201; H01L 31/046
20141201; H01L 31/03926 20130101 |
Class at
Publication: |
136/251 ;
136/244; 438/73 |
International
Class: |
H01L 31/05 20060101
H01L031/05 |
Claims
1-21. (canceled)
22. A nonplanar photovoltaic module having a length, comprising: a.
an elongated nonplanar substrate; and b. a plurality of solar cells
disposed on the elongated nonplanar substrate, wherein each solar
cell in the plurality of solar cells is defined by (i) a plurality
of grooves around the nonplanar photovoltaic module and (ii) a
groove along the length of the photovoltaic module.
23. The photovoltaic module of claim 22, wherein each groove of the
plurality of grooves about the photovoltaic module, independently
has a repeating pattern, a non-repeating pattern, or is
helical.
24. The photovoltaic module of claim 22, further comprising a
patterned conductor providing serial electrical communication
between adjacent solar cells in the plurality of solar cells.
25. The photovoltaic module of claim 24, wherein portions of the
patterned conductor providing serial electrical communication
between adjacent solar cells are within a groove of the plurality
of grooves about the photovoltaic module.
26. The photovoltaic module of claim 22, wherein a solar cell in
the plurality of solar cells comprises a back-electrode layer
disposed on the substrate, wherein portions of the back-electrode
layer are defined by a first groove of the plurality of grooves
about the photovoltaic module and the groove along the length of
the photovoltaic module.
27. The photovoltaic module of claim 26, wherein a solar cell in
the plurality of solar cells further comprises a semiconductor
junction disposed on the back-electrode layer, wherein portions of
the semiconductor junction are defined by a second groove of the
plurality of grooves about the photovoltaic module and the groove
along the length of the photovoltaic module.
28. The photovoltaic module of claim 27, wherein a solar cell in
the plurality of solar cells further comprises a transparent
conductor layer disposed on the semiconductor junction, wherein
portions of the transparent conductor layer are defined by a third
groove of the plurality of grooves about the photovoltaic module
and the groove along the length of the photovoltaic module.
29. The photovoltaic module of claim 28, wherein a solar cell in
the plurality of solar cells comprises a portion of the
back-electrode layer, a portion of the semiconductor junction at
least partially overlying the portion of the back-electrode layer,
and a portion of the transparent conductor layer at least partially
overlying the portion of the semiconductor junction.
30. The photovoltaic module of claim 29, wherein portions of the
transparent conductor layer are in the second groove and provide
electrical communication between the portion of the back-electrode
layer of a first solar cell of the plurality of solar cells and the
portion of the transparent conductor layer of a second solar cell
of the plurality of solar cells, wherein the first solar cell is
adjacent to the second solar cell.
31. The photovoltaic module of claim 29, wherein the first, second,
and third grooves are laterally offset from each other.
32. The photovoltaic module of claim 22, further comprising a
substantially transparent casing circumferentially disposed on the
plurality of solar cells.
33. The photovoltaic module of claim 22, wherein the groove along
the length of the photovoltaic module is linear.
34. The photovoltaic module of claim 22, wherein the plurality of
solar cells comprises at least ten solar cells.
35-52. (canceled)
53. A method of creating a non-unifacial photovoltaic module around
an elongated substrate, the method comprising: a) disposing a first
material on the elongated substrate to form a back electrode; b)
disposing one or more photovoltaic materials on the back electrode
to form a photovoltaic layer; c) disposing a second material on the
photovoltaic layer to form a front electrode; d) patterning any of
the back electrode, the photovoltaic layer, and the front electrode
layer to form a cell boundary, the patterning comprising:
traversing a first path in the any of the back electrode, the
photovoltaic layer, and the front electrode layer in (i) a first
orientation directed along a width of the elongated substrate, and
(ii) a second orientation directed along a length of the elongated
substrate, the traversing in (i) the first orientation occurring
substantially concurrently with the traversing in (ii) the second
orientation so that the first path includes a component in the
first orientation and a component in the second orientation.
54. (canceled)
55. A photovoltaic module having a length dimension and a width
dimension, the photovoltaic module comprising: (A) an elongated
substrate; (B) a plurality of photovoltaic components comprising
(i) a first material disposed on the elongated substrate to form a
back electrode, (ii) one or more photovoltaic materials disposed on
the back electrode to form a photovoltaic layer, and (iii) a second
material disposed on the photovoltaic layer to form a front
electrode; (C) one or more solar cells formed from the plurality of
photovoltaic components such that the one or more solar cells are
operable to generate electricity from light impinging the one or
more solar cells from a range of directions spanning more than 180
degrees about the length dimension or the width dimension of the
photovoltaic module; and (D) an electrical boundary within at least
one photovoltaic component in the plurality of photovoltaic
components, wherein the electrical boundary is formed by a
patterning of the back electrode, the photovoltaic layer, the front
electrode, or any combination thereof, the patterning comprising a
forming of a filled or unfilled via following a path comprising a
first component and a second component, wherein: the first
component is a first orientation directed along a width of the
elongated substrate, and the second component is a second
orientation directed along a length of the elongated substrate; and
wherein the forming advances substantially concurrently (i) in the
first orientation at a first rate and (ii) in the second
orientation at a second rate.
56. The module of claim 55, wherein at least one of the first and
second rates is variable.
57. The module of claim 55, wherein the first rate is different
from the second rate.
58. The module of claim 55, wherein the electrical boundary is an
isolation boundary.
59. The module of claim 55, wherein the electrical boundary defines
a serial electrical connection between solar cells that share the
electrical boundary.
60. The module of claim 55, wherein the electrical boundary defines
a parallel electrical connection between solar cells that share the
electrical boundary.
61. (canceled)
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims benefit, under 35 U.S.C.
.sctn.119(e), of U.S. Provisional Patent Application No.
61/082,152, filed on Jul. 18, 2008, which is hereby incorporated by
reference herein in its entirety.
FIELD OF THE APPLICATION
[0002] This application relates to systems and methods for
monolithically integrated solar cells.
BACKGROUND OF THE APPLICATION
[0003] The solar cells of photovoltaic modules are typically
fabricated as separate physical entities with light gathering
surface areas on the order of 4-6 cm.sup.2 or larger. For this
reason, it is standard practice for power generating applications
to mount photovoltaic modules containing one or more solar cells in
a flat array on a supporting substrate or panel so that their light
gathering surfaces provide an approximation of a single large light
gathering surface. Also, since each solar cell itself generates
only a small amount of power, the required voltage and/or current
is realized by interconnecting the solar cells of the module in a
series and/or parallel matrix.
[0004] A conventional prior art photovoltaic module 10 is shown in
FIG. 6. A photovoltaic module 10 can typically have one or more
photovoltaic cells (solar cells) 12a-12b disposed within it.
Because of the large range in the thickness of the different layers
in a solar cell, the cells 12a, 12b, and other cells described
herein are depicted schematically. Moreover, FIG. 6 is highly
schematic so that it represents the features of both "thick-film"
solar cells and "thin-film" solar cells. Typically, solar cells
that use an indirect band gap material to absorb light are
typically configured as "thick-film" solar cells because a
relatively thick film of the absorber layer is required to absorb a
sufficient amount of light. Solar cells that use a direct band gap
material to absorb light are typically configured as "thin-film"
solar cells because only a thin layer of the direct band-gap
material is needed to absorb a sufficient amount of light.
[0005] The arrows at the top of FIG. 6 show the source of direct
solar illumination on the photovoltaic module 10. The layer 102 of
the solar cells 12a, 12b is the substrate. Glass or metal is a
common substrate. In some instances, there is an encapsulation
layer (not shown) coating the substrate 102. In some embodiments,
each solar cell 12a, 12b in the photovoltaic module 10 has its own
discrete substrate 102 as illustrated in FIG. 6. In other
embodiments, there is a substrate 102 that is common to all or many
of the solar cells 12a, 12b of the photovoltaic module 10.
[0006] The layer 104 is the back electrical contact for each of the
solar cells 12a, 12b in the photovoltaic module 10. The layer 106
is the semiconductor absorber layer of each of the solar cells 12a,
12b in the photovoltaic module 10. In a given solar cell 12a, 12b,
the back electrical contact 104 makes ohmic contact with the
absorber layer 106. In many but not all cases, the absorber layer
106 is a p-type semiconductor. The absorber layer 106 is thick
enough to absorb light. The layer 108 is the semiconductor junction
partner that, together with the semiconductor absorber layer 106,
completes the formation of a p-n junction of each solar cell 12a,
12b. A p-n junction is a common type of junction found in the solar
cells 12a, 12b. In p-n junction based solar cells 12a, 12b, when
the semiconductor absorber layer 106 is a p-type doped material,
the junction partner 108 is an n-type doped material. Conversely,
when the semiconductor absorber layer 106 is an n-type doped
material, the junction partner 108 is a p-type doped material.
Generally, the junction partner 108 is much thinner than the
absorber layer 106. The junction partner 108 is highly transparent
to solar radiation. The junction partner 108 is also known as the
junction partner layer, since it lets the light pass down to the
absorber layer 106.
[0007] In typical thick-film solar cells 12a, 12b, the absorber
layer 106 and the junction partner layer 108 can be made from the
same semiconductor material but have different carrier types
(dopants) and/or carrier concentrations in order to give the two
layers their distinct p-type and n-type properties. In thin-film
solar cells 12a, 12b in which copper-indium-gallium-diselenide
(CIGS) is the absorber layer 106, the use of CdS to form the
junction partner 108 has resulted in high efficiency photovoltaic
devices. The layer 110 is a counter electrode that is used to draw
current away from the junction since the junction partner 108 is
generally too resistive to serve this function. As such, the
counter electrode 110 is typically highly conductive and
substantially transparent to light. The counter electrode 110 can
be a comb-like structure of metal printed onto the junction partner
layer 108 rather than forming a discrete layer. The counter
electrode 110 is typically a transparent conductive oxide (TCO)
such as doped zinc oxide. However, even when a TCO layer is
present, a bus bar network 114 is typically needed in the
conventional photovoltaic module 10 to draw off current since the
TCO has too much resistance to efficiently perform this function in
larger photovoltaic modules. The network 114 shortens the distance
charge carriers must move in the TCO layer in order to reach the
metal contact, thereby reducing resistive losses. The metal bus
bars, also termed grid lines, can be made of any reasonably
conductive metal such as, for example, silver, steel or aluminum.
The metal bars are preferably configured in a comb-like arrangement
to permit light rays through the TCO layer 110. The bus bar network
layer 114 and the TCO layer 110, combined, act as a single
metallurgical unit, functionally interfacing with a first ohmic
contact to form a current collection circuit.
[0008] An optional antireflective coating 112 allows a significant
amount of extra light into the solar cells 12a, 12b. Depending on
the intended use of the photovoltaic module 10, it might be
deposited directly on the top conductor 110 as illustrated in FIG.
6. Alternatively or additionally, the antireflective coating 112
can be deposited on a separate cover glass that overlays the top
electrode 110. In some embodiments, the antireflective coating 112
reduces the reflection of the solar cells 12a, 12b to very near
zero over the spectral region in which photoelectric absorption
occurs, and at the same time increases the reflection in other
spectral regions to reduce heating. U.S. Pat. No. 6,107,564 to
Aguilera et al., hereby incorporated by reference herein in its
entirety, describes representative antireflective coatings that are
known in the art.
[0009] The solar cells 12a, 12b typically produce only a small
voltage. For example, silicon based solar cells produce a voltage
of about 0.6 volts (V). Thus, solar cells 12a, 12b are
interconnected in series or parallel in order to achieve greater
voltages. When connected in series, voltages of individual solar
cells add together while current remains the same. Thus, solar
cells arranged in series reduce the amount of current flow through
such cells, compared to analogous solar cells arranged in parallel,
thereby improving efficiency. As illustrated in FIG. 6, the
arrangement of the solar cells 12a, 12b in series is accomplished
using interconnects 116. In general, an interconnect 116 places the
first electrode of one solar cell 12a in electrical communication
with the counter-electrode of an adjoining solar cell 12b of a
photovoltaic module 10.
[0010] Various fabrication techniques (e.g., mechanical and laser
scribing) can be used to segment a photovoltaic module 10 into
individual solar cells (e.g., 12a, 12b) to generate high output
voltage through integration of such segmented solar cells. Grooves
that separate individual solar cells typically have low series
resistance and high shunt resistance to facilitate integration.
Such grooves are typically made as small as possible in order to
reduce dead area and enhance material usage.
[0011] Discussion or citation of a reference herein will not be
construed as an admission that such reference is prior art to the
present application.
SUMMARY
[0012] Under one aspect, a photovoltaic module includes a plurality
of solar cells that share a common, elongated substrate. Each solar
cell includes a back-electrode, a semiconductor junction disposed
on and at least partially overlapping the back-electrode, and a
transparent conductor disposed on and at least partially
overlapping the semiconductor junction. The back-electrodes of the
solar cells are physically separated and electrically isolated from
each other by a groove that wraps around the substrate a plurality
of times, as well as by a groove along the length of the substrate.
The semiconductor junctions of the solar cells are physically
separated and electrically isolated from each other by a groove
that wraps around the substrate a plurality of times, and by the
previously mentioned groove along the length of the substrate. The
transparent conductors of the solar cells are physically separated
and electrically isolated from each other by a groove that wraps
around the substrate a plurality of times, as well as by the
previously mentioned groove along the length of the substrate. The
grooves of the back-electrodes, semiconductor junctions, and
transparent conductors are laterally offset from each other. This
lateral offset forms a via between the transparent conductor of a
first solar cell and the back-electrode of a second solar cell that
is adjacent to the first solar cell. The via is filled with
transparent conductor or some other suitable conductive material.
The interconnection of the transparent conductor of a cell to the
back-electrode of its neighboring cell monolithically integrates
the cells along the length of the substrate, thus resulting in
improved performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1A illustrates a plan view of a non-planar
semiconductor device in accordance with some embodiments of the
present application.
[0014] FIG. 1B illustrates a cross-sectional view of a non-planar
semiconductor device in accordance with some embodiments of the
present application.
[0015] FIG. 1C illustrates a plan view of a plurality of non-planar
semiconductor devices in accordance with some embodiments of the
present application.
[0016] FIG. 1D illustrates a cross-sectional view of a plurality of
non-planar semiconductor devices in accordance with some
embodiments of the present application.
[0017] FIG. 2A illustrates a plan view of a monolithically
integrated, non-planar photovoltaic module in accordance with some
embodiments of the present application.
[0018] FIG. 2B illustrates a cross-sectional view of a
monolithically integrated, non-planar photovoltaic module in
accordance with some embodiments of the present application.
[0019] FIG. 2C illustrates a cross-sectional view of a
monolithically integrated, non-planar photovoltaic module in
accordance with some embodiments of the present application.
[0020] FIG. 2D illustrates a plan view of a non-planar solar cell
in accordance with some embodiments of the present application.
[0021] FIG. 2E illustrates a perspective view of an encased,
monolithically integrated, non-planar photovoltaic module in
accordance with some embodiments of the present application.
[0022] FIG. 2F illustrates a cross-sectional view of an encased,
monolithically integrated, non-planar photovoltaic module in
accordance with some embodiments of the present application.
[0023] FIG. 3 illustrates a method for forming a monolithically
integrated, non-planar solar cell module in accordance with some
embodiments of the present application.
[0024] FIGS. 4A-4I illustrate plan and cross-sectional views of
structures formed during a method for forming monolithically
integrated solar cells of a photovoltaic module in accordance with
some embodiments of the present application.
[0025] FIGS. 5A-5B illustrate exemplary semiconductor junctions in
accordance with some embodiments of the present application.
[0026] FIG. 6 illustrates interconnected solar cells of a
photovoltaic module in accordance with the prior art.
[0027] Dimensions are not drawn to scale.
DETAILED DESCRIPTION
[0028] Disclosed herein are non-planar conductive devices disposed
on a substrate and having boundaries defined by one or more grooves
that wrap around the substrate as well as a groove that extends
laterally along the substrate, methods of making same, and systems
for making same. Also disclosed herein are monolithically
integrated, non-planar solar cells disposed on a substrate and
having boundaries defined by grooves that wrap around the substrate
as well as a groove that extends laterally along the substrate,
methods of making same, and systems for making same.
Scribed Non-Planar Conductive Devices
[0029] Under one aspect of the present application, a plurality of
conductive devices is solar cells can be defined on an elongated
substrate by a groove or scribe, where the cell or cells have
boundaries that both radially wraps multiple times around the
substrate, and optionally a groove or scribe along while traversing
the length of the substrate.
[0030] FIG. 1A is a plan view of FIG. 1A is a plan view of an
exemplary semiconductor unit 60 that includes a plurality of
semiconductor devices 60a, 60b, 60c, 60d, and 60f. elongated
conductive device 50 that includes a non-planar substrate 52, a
nonplanar conductive layer 56, and a three-dimensional groove 58.
The groove 58 extends through the entire thickness of semiconductor
layer 56, and wraps multiple times around the substrate 52, along
the length of the substrate 52. FIG. 1B is a cross-sectional view
of device 50 along line 1A-1A'.
[0031] Without the groove 58, the nonplanar conductive layer 56
would conform to the entire outer surface of the substrate 52, and
a current applied to the layer 56 at the first end A of the layer
would simply flow straight to the other end B of the layer,
resulting in a path length that is as long as the distance directly
between A and B. However, the groove 58 transforms layer 56 into a
single long conductor that wraps multiple times around the
substrate 52. Accordingly, the groove 58 also modifies the
direction in which current flows through layer 56. As illustrated
in FIG. 1A, current flows from the first end A of the layer 56 to
the other end B of the layer 56 via a path that wraps multiple
times around the substrate. Thus, the groove 58 significantly
increases the path length for current flow, which is now based on
the lateral length of the layer 56 (which may be the same as the
length of the substrate) and the number of times that the groove 58
traverses the perimeter of the conductive layer 56, among other
things. The path length for the current flow can be modified by
changing the number of times that the groove 58 wraps around the
substrate.
[0032] The conductive layer 56 can include any type of conductor,
including metal, semiconductor, and/or conductive or semiconductive
polymer. The conductive layer need not be made of a single
material, but can have some regions formed of one type of material,
and other regions formed of one or more other types of material.
For example, some regions of layer 56 can be metal, while other
regions of layer 56 can be semiconductor or polymer. Some regions
of the conductive layer 56 can even be insulative, e.g., glass or
insulating polymer. The different material regions can be patterned
using conventional semiconductor patterning techniques.
[0033] The nonplanar substrate 52 can include any type of suitable
material, including metal, semiconductor, conductive or semi
conductive polymer, and/or an insulator.
[0034] The nonplanar substrate 52 can be "omnifacial," that is,
having a single surface around the perimeter of the substrate.
Cylindrical substrates are an example of an omnifacial substrate.
Hollow substrates (e.g., hollow tubes) are also considered to be
omnifacial because the exterior surface, which is the surface upon
which the semiconductor layer 56 is disposed, is omnifacial. The
nonplanar substrate 52 can alternatively be "multifacial," e.g.,
bifacial, trifacial, or having more than three faces. A multifacial
substrate has a plurality of faces that face in different
directions. An example of a bifacial substrate is one having two
opposing surfaces. In a multifacial configuration, the shape of the
cross section of the substrate can be described by any combination
of straight lines and curved features. Some examples of multifacial
substrates are provided below with reference to photovoltaic
devices. A "unifacial" substrate is one having only a single face
that faces a single direction.
[0035] FIG. 1C is a plan view of a conductive device 60 that
includes a substrate 62, a nonplanar conductive layer 64, a groove
68 that wraps multiple times around the substrate, and a groove 66
that extends along the length of the substrate. The grooves 68 and
66 both extend through the entire thickness of conductive layer 64.
The grooves 68 and 66 divide the semiconductor layer into a
plurality of discrete conductive devices 60a, 60b, 60c, 60d, and
60f. FIG. 1D is a cross-sectional view of device 60 along line
1C-1C'.
[0036] The size and number of conductive devices 60a, 60b, 60c, 60d
into which grooves 68 and 66 divide conductive layer 64 is based,
in part, on the lateral length of the layer 64 (which may be the
same as the length of the substrate) and the number of times that
the groove 58 traverses the perimeter of the conductive layer 64,
among other things. Optionally, the device 60 can include multiple
scribes 66 that extend along the length of the device, which can
further divide the conductive layer 64 into additional discrete
devices. The devices can be connected in series or in parallel
using additional conductive material (not shown in FIG. 1C or 1D).
See below for an example of connecting solar cells.
[0037] In the embodiments illustrated in FIGS. 1A-1D, a single
scribed conductive layer 54 or 64 is illustrated. However, it
should be noted that the devices can include multiple other layers
besides the conductive layer 54 or 64. These other layers can be
under the conductive layer 54 or 64, can be over the conductive
layer 54 or 64, and/or can even be within the grooves. The other
layers can themselves be scribed so as to have grooves. The grooves
in the conductive layer 54 or 64 and any other scribed layer need
not extend through the entire thickness of the layer(s), but can
extend only partially through the thickness of one or more of the
layer(s). The other layers can have any suitable composition (e.g.,
can be a conductor, insulator, or semiconductor) and can be
patterned.
[0038] Nonplanar solar cells are one example of conductive devices
that can be formed on nonplanar substrates. The descriptions below
of methods and systems for scribing nonplanar solar cells, as well
as materials and characteristics of the layers and substrates used
therein, apply equally to the formation of other types of
conductive devices such as those described above.
Scribed Non-Planar Solar Cells
[0039] One exemplary purpose of scribing a photovoltaic module is
to break a photovoltaic module up into discrete solar cells that
may, for example, be serially combined in a process known as
"monolithic integration." Monolithically integrated solar cells
have the useful feature of reducing current carrying requirements
of the integrated solar cells. Sufficient monolithic integration
can therefore substantially reduce electrode, transparent
conductor, and counter-electrode current carrying requirements,
thereby reducing material costs. Examples of monolithically
integrated, non-planar solar cells are found in U.S. Pat. No.
7,235,736 entitled "Monolithic integration of cylindrical solar
cells," which is hereby incorporated by reference herein in its
entirety. The present application provides various configurations
of monolithically integrated, non-planar solar cells, and systems
and methods for making same.
[0040] Disclosed herein is a photovoltaic module including an
elongated nonplanar substrate, and a plurality of solar cells
disposed on the elongated nonplanar substrate. The electrical
connections and electrical paths, and boundaries between the solar
cells disposed on the elongated substrate are defined by a
plurality of grooves or scribes around the module. The isolation
boundaries between solar cells disposed on the elongated substrate
can be defined by a groove along the length of the module. The
cells are monolithically integrated with each other, e.g., adjacent
cells are in serial or parallel electrical contact with each
other.
[0041] Also disclosed herein is a method of forming a photovoltaic
module having a nonplanar substrate that includes a non-planar
back-electrode layer. The back-electrode layer is scribed so as to
form a single groove that traverses a plurality of times about the
substrate. A semiconductor junction is then disposed on the
back-electrode layer, and is scribed so as to form a single groove
that traverses a plurality of times about the substrate. A
transparent conductor layer is then disposed on the semiconductor
junction, and is scribed so as to form single groove that traverses
a plurality of times about the substrate. The back-electrode layer,
semiconductor junction, and transparent conductor layer are then
scribed so as to form a single groove that traverses along the
length of the substrate. This forms a plurality of solar cells,
each of which includes an isolated portion of the back electrode
layer, and isolated portion of the semiconductor junction, and an
isolated portion of the conductor layer. The cells are
monolithically integrated with each other, e.g., adjacent cells are
in serial or parallel electrical contact with each other.
[0042] Also disclosed herein is a photovoltaic module including a
nonplanar substrate with a nonplanar back-electrode layer disposed
around the substrate, which is formed by scribing the
back-electrode so as to form a single groove that traverses a
plurality of times about the substrate. A semiconductor junction is
then disposed on the back-electrode layer, and scribed so as to
form a single groove that traverses a plurality of times about the
substrate. A transparent conductor layer is then disposed on the
semiconductor junction, and scribed so as to form a single groove
that traverses a plurality of times about the substrate. The
back-electrode layer, semiconductor junction, and transparent
conductor layer are then scribed so as to form a single groove
along the length of the substrate. This forms a plurality of solar
cells, each of which includes an isolated portion of the back
electrode layer, and isolated portion of the semiconductor
junction, and an isolated portion of the conductor layer. The cells
are monolithically integrated with each other, e.g., adjacent cells
are in serial or parallel electrical contact with each other.
Monolithically Integrated, Non-Planar Photovoltaic Modules
[0043] Under one aspect of the present application, a
monolithically integrated, non-planar photovoltaic module includes
an nonplanar, elongated substrate, and a plurality of solar cells
disposed on the elongated substrate, wherein boundaries between the
solar cells are defined by a plurality of grooves that wrap around
(or traverse) the substrate a plurality of times, a groove along
the length of the substrate.
[0044] FIG. 2A illustrates a plan view of an exemplary
monolithically integrated, non-planar photovoltaic module 402, with
portions of some layers cut away so that various underlying
features of the module can be seen more conveniently. The module
402 includes a nonplanar substrate 102, a nonplanar back-electrode
104, a nonplanar absorber layer 106 (not visible in this view), a
nonplanar junction partner layer 108, and a nonplanar transparent
conductor 110. Module 402 can also include one or more other layers
such as those described herein, e.g., a casing, filler layer,
intrinsic layer, antireflective layer, etc., but those layers are
omitted in FIG. 2A for clarity. Examples of materials that can be
used in module 402 are described in further detail below.
[0045] The nonplanar substrate 102 is elongated, i.e., has a length
that is substantially larger than its width. In some embodiments,
as illustrated in FIG. 2A, the substrate 102 is cylindrically
shaped, although other nonplanar shapes are possible, as described
in greater detail below. The nonplanar substrate 102 can have a
solid core, as in the embodiment illustrated in FIG. 2A, while in
other embodiments, the elongated substrate 102 can have a hollow
core.
[0046] The nonplanar back-electrode 104 is disposed on the
substrate 102, and is divided into discrete portions (e.g., the
portions 104A and 104B) by a groove 292 that wraps a plurality of
times about the substrate 102 and the groove 300 along the length
of the substrate 102. In the illustrated embodiment, groove 292 is
helical (i.e., is a straight line that wraps around the
circumference of substrate 102), and groove 300 is linear, although
other shapes are possible, as described in greater detail below.
The grooves 292 and 300 each extend through the entire thickness of
the back electrode layer 104, in defined regions. As described in
greater detail below, the linear groove 300 also extends through
the entire thicknesses of the absorber layer (not visible in this
view), the junction partner layer 108, and the overlying
transparent conductor layer 110.
[0047] The grooves 292, 300 physically separate and electrically
isolate the portions 104A, 104B of the back-electrode 104 from each
other. In some embodiments, a groove is considered to be
"electrically isolating" when the resistance across the groove
(e.g., from a first side of the groove to a second side of the
groove) is 10 ohms or more, 20 ohms or more, 50 ohms or more, 1000
ohms or more, 10,000 ohms or more, 100,000 ohms or more,
1.times.10.sup.6 ohms or more, 1.times.10.sup.7 ohms or more,
1.times.10.sup.8 ohms or more, 1.times.10.sup.9 ohms or more, or
1.times.10.sup.10 ohms or more. The electrical resistance between
adjacent portions of the back-electrode 104 (e.g., the portions
104A, 104B) is based, among other things, on the width, depth, and
quality of the grooves 292, 300. Note that although grooves may
electrically isolate portions of a given layer from each other, one
or more materials subsequently deposited within those grooves may
provide some electrical contact between those portions. Even if
other materials are present in a groove, the portions of a given
layer (e.g., the portions 104A, 104B) are still considered to be
physically separated and electrically isolated from each other by
that groove.
[0048] Although other portions of back-electrode 104 are not
visible in this view because they are obscured by overlying layers
(e.g., the layers 108 and 110), the grooves 292, 300 define
multiple discrete portions of the back-electrode 104 along the
length of the nonplanar substrate 102. In embodiments in which
groove 292 is helical, the number and size of portions into which
the back-electrode is divided is based on, among other things, the
length and cross-sectional dimensions of the nonplanar substrate
102, and the pitch of the helical groove 292. The "pitch" of a
helix is defined to be the width of one complete helix turn (e.g.,
about the substrate 102), measured along the helix axis (e.g.,
along the length of the substrate).
[0049] A nonplanar semiconductor junction that includes an absorber
layer 106 (not visible in this view) disposed on the back-electrode
104, and a junction partner layer 108 disposed on the absorber
layer 106, is divided into discrete portions (106A, 106B, 108A,
108B) by the groove 294 about the circumference along the length of
the substrate 102 and the groove 300 along the length of the
substrate 102. Although FIG. 2A illustrates groove 294 as helical,
other shapes are possible, as described below. The grooves 294 and
300 each extend through the entire thicknesses of the junction
partner layer 108 and the absorber layer 106.
[0050] The groove 294 of the absorber and the junction partner
layers 106, 108 is laterally offset from the groove 292 of the
back-electrode layer 104, and in some embodiments, has
substantially the same pitch as the groove 292. Although other
portions of the absorber layer 106 and the junction partner layer
108 are not visible in this view because they are obscured by
overlying layers, the grooves 294, 300 define multiple discrete
portions of the absorber layer 106 and the junction partner layer
108 along the length of the substrate 102. Additionally, although
the portions 104A and 104B of the back-electrode layer 104 are at
least partially visible in the view of FIG. 2A, in some embodiments
the portions 104A and 104B would be at least partially obscured by
overlying the absorber layer 106 and the junction partner layer
108, as well as other layers present in the photovoltaic module
402.
[0051] The grooves 294, 300 electrically isolate the portions 106A,
106B (not visible in this view) of absorber layer 106 from each
other, and electrically isolate the portions 108A, 108B of junction
partner layer 108 from each other. In embodiments where the groove
294 is helical, the number of portions into which the absorber and
junction partner layers are divided is based on, among other
things, the length and cross-sectional dimensions of the substrate
102, and the pitch of the helical groove 294. The electrical
resistance between adjacent portions of the absorber layer (e.g.,
portions 106A, 106B), and the electrical resistance between
adjacent portions of the junction partner layer (e.g., portions
108A, 108B) is based on, among other things, the width, depth, and
quality of the grooves 294, 300.
[0052] A nonplanar transparent conductor layer 110 is disposed on
the junction partner layer 108, and is divided into discrete
portions (110A, 110B) by a groove 296 about the substrate 102 and
the groove 300 along the length of the substrate. The groove 296 of
the transparent conductor layer 110 is laterally offset from the
groove 294 of the absorber and junction partner layers 106, 108,
and is also laterally offset from the groove 292 of the
back-electrode layer 104. In some embodiments, for example, in some
embodiments where grooves 292, 294, and 296 are helical, the groove
296 has substantially the same pitch as the grooves 292 and/or 294.
The grooves 296 and 300 each extend through the entire thickness of
the transparent conductor layer 110.
[0053] Although other portions of the nonplanar transparent
conductor layer 110 are not visible in this view because they are
obscured by overlying layers, the grooves 296, 300 define multiple
discrete portions of the transparent conductor layer 110 along the
length of the substrate 102. Additionally, although the portions
104A and 104B of the back-electrode layer 104 and the portions 108A
and 108B of the junction partner layer 108 are at least partially
visible in the view of FIG. 3A, in some embodiments the portions
104A, 104B, 108A, and 108B are at least partially obscured by the
transparent conductor layer 110, in combination with one or more
other layers present in the photovoltaic module 402. In the
embodiment illustrated in FIG. 3A, a small portion of the layer 108
can be seen through the helical gap 296 between the portions 110A,
110B of the transparent conductor layer 110.
[0054] The grooves 296, 300 electrically isolate the portions 110A,
110B of the transparent conductor layer 110 from each other. In
embodiments in which groove 296 is helical, the number of portions
into which the transparent conductor layer 110 divided is based on,
among other things, the length and cross-sectional dimensions of
the substrate 102, and the pitch of helical groove 296. The
electrical resistance between adjacent portions of the transparent
conductor layer (e.g., the portions 110A, 110B) is based on, among
other things, the width, depth, and quality of the grooves 296,
300.
[0055] FIG. 2B illustrates a cross-section of the non-planar
photovoltaic module 402 illustrated in FIG. 2A, taken along line
2B-2B'. The photovoltaic module 402 includes a first solar cell 12C
and a second solar cell 12D that is adjacent to, and shares
nonplanar substrate 102 with, a second solar cell 12D. As mentioned
above, although nonplanar substrate 102 is cylindrical in the
illustrated embodiment, the substrate can have alternate nonplanar
shapes, as described in greater detail below.
[0056] The solar cell 12C includes a back-electrode portion 104C,
an absorber layer portion 106C, a junction partner layer portion
108C, and a transparent conductor portion 110C. The solar cell 12D
includes a back-electrode portion 104D, an absorber layer portion
106D, a junction partner layer portion 108D, and a transparent
conductor portion 110D. The groove 292 separates the back-electrode
portion 104C of the first solar cell 12C from the back-electrode
portion 104D of the second solar cell 12D. The groove 294
respectively separates the absorber layer portion 106C and the
junction partner layer portion 108C of the first solar cell 12C
from the absorber layer portion 106D and the junction partner layer
portion 108D of the second solar cell 12D. The groove 296 separates
the transparent conductor portion 110C of the first solar cell 12C
from the transparent conductor portion 110D of the second solar
cell 12D. In some embodiments, the widths of solar cells 12C, 12D
is between about 1 millimeter (mm) and about 20 mm, e.g., about 6
mm.
[0057] The solar cells 12C and 12D are monolithically integrated
with each other, as well as with respective adjacent solar cells.
In the illustrated embodiment, the transparent conductor portion
110C of the first solar cell 12C is in serial electrical
communication with the back-electrode portion 104D of the second
solar cell 12D. In the embodiments illustrated in FIGS. 2A-2F, the
transparent conductor portion 110C of the first solar cell 12C
fills the groove 294 and contacts the back electrode portion 104D
of the second solar cell 12D, thus providing an electrical
communication pathway between the transparent conductor portion
110C and the back electrode portion 104D. In operation, current
flows between transparent conductor portion 110C and back electrode
portion 104D via the transparent conductor material within the
groove 294. Thus, the portion of transparent conductor within
groove 294 can be considered a "conductive via." In other
embodiments, a conductive material other than transparent conductor
is provided within groove 294 to provide electrical communication
between the transparent conductor portion 110C and the
back-electrode portion 104D, e.g., a metal or alloy. In some
embodiments, the solar cells 12C and 12D are in parallel electrical
contact with each other.
[0058] Note that although the transparent conductor material within
the groove 294 provides electrical communication between the
absorber layer portion 106C and the junction partner layer portion
108C of the first solar cell 12C, and the absorber layer portion
106D and the junction partner layer portion 108D of the second
solar cell 12D, in operation, there is a negligible potential
difference and thus negligible current flow between the absorber
layer portion 106C and the junction partner layer portion 108C of
the first solar cell 12C, and the absorber layer portion 106D and
the junction partner layer portion 108D of the solar cell 12D. The
predominant current flow between the first and second solar cells
12C and 12D is between the transparent conductor portion 110C and
the back-electrode portion 104D through the transparent conductor
(or other conductive material) within the groove 294.
[0059] FIG. 2C illustrates a cross-section of the photovoltaic
module 402 illustrated in FIG. 2A, taken along line 2C-2C'. As
described above with respect to FIGS. 2A and 2B, the photovoltaic
module 402 includes a substrate 102, a back-electrode 104, an
absorber layer 106, a junction partner layer 108, and a transparent
conductor layer 110. A groove 300 extends through the thicknesses
of each of the layers 104, 106, 108, and 110, and in combination
with the grooves 292, 294, and 296 (not visible in this view)
divides the layers 104, 106, 108, and 110 into discrete portions
that are respectively electrically isolated from each other. The
size and shape of the solar cells in the module 402 is based in
part on the diameter D of the substrate 102, as well as the widths
and pitches of the grooves 292, 294, and 296, and the width M of
the groove 300.
[0060] FIG. 2D illustrates a plan view of an individual transparent
conductor layer portion 110C of solar cell 12C of the nonplanar
photovoltaic module 402 illustrated in FIG. 2B, in a "planarized"
perspective representing what it would look like if the portion
110C was peeled from the solar cell 12C and laid flat on a planar
surface. The "planarized" transparent conductor layer portion 110C
has the shape of a parallelogram, where the top and bottom edges of
the parallelogram are defined by the groove 300, and the side edges
of the parallelogram are defined by the groove 296. In the
illustrated embodiment, groove 296 is helical, and the top and
bottom edges of the parallelogram have a width W that is based on
the pitch and width of the helical groove 296. The side edges of
the parallelogram have a length L that is based on the pitch of the
groove 296, the diameter D of the substrate, and the width W of the
groove 300.
[0061] If also "planarized," the back-conductor layer portion 104C
of the solar cell 12C (not shown in FIG. 2D) would also have the
shape of a parallelogram, where the top and bottom edges of the
parallelogram have a width W that is based on the pitch and width
of the groove 292, and where the side edges of the parallelogram
have a length L that is based on the pitch of the groove 292, the
diameter D of the substrate, and the width W of the groove 300.
[0062] If also "planarized," the absorber layer portion 106C and
the junction partner layer portion 108C of the solar cell 12C (not
shown in FIG. 2D) would also have the shape of a parallelogram,
where the top and bottom edges of the parallelogram have a width W
that is based on the pitch and width of the groove 294, and where
the side edges of the parallelogram have a length L that is based
on the pitch of the groove 294, the diameter D of the substrate,
and the width W of the groove 300.
[0063] In other embodiments, e.g., in which groove 296 is not
helical and/or groove 300 is not linear, the solar cells 12C and
12D may have the same or different shapes as each other, and will
have surface areas that are defined by the particular embodiments
of grooves 296 and 300.
[0064] As illustrated in the perspective view of FIG. 2E, the
photovoltaic module 420 can optionally include a substantially
transparent casing 310 and filler 330. The casing 310 can help to
protect the solar cells of the module from damage, and the filler
330 substantially fills the space between the casing 310 and the
solar cells 12. In FIG. 2E, portions of the filler 330 and the
casing 310 are "cut away" so that portions of the underlying
substrate 102 (visible through the groove 300), the junction
partner layer 108 (visible through the groove 296), and the
transparent conductor layer portions 110A, 110B can be seen.
[0065] FIG. 2F is a cross-sectional view of the embodiment of FIG.
2E taken along lines 2F-2F'. The filler 330 is disposed on the
transparent conductor layer 110, and the casing is disposed on the
filler 330. The filler also fills the groove 296 in the transparent
conductor layer 110, and contacts portions of the junction partner
layer 108. The casing 310 need not be cylindrical.
[0066] As noted above, the grooves 292, 294, and 296 need not be
helical (a line wrapped around the substrate). Instead, the grooves
292, 294, and 296 can take a variety of shapes. For example, the
grooves, independently of each other, can have a repeating pattern
(e.g., a curve, a wavy line, or a zig-zag) or can have a
non-repeating pattern. In some embodiments, one or more of the
grooves 292, 294, and 296 is a space curve, wherein the space curve
is formed by wrapping a two dimensional curve having a repeating
pattern about the photovoltaic module.
[0067] In some embodiments, the grooves 292, 294, and 296 have
approximately the same repeating or non-repeating pattern as each
other, so that adjacent solar cells will have approximately the
same shape as each other. The groove 300 need not be linear, but
can have a repeating pattern (e.g., a curve, a wavy line, or a
zig-zag), or can have a non-repeating pattern. Additionally,
adjacent solar cells need not have the same shape or surface area
as one another. For example, solar cells at the end of the
nonplanar photovoltaic module may have a truncated surface area
relative to solar cells central to the nonplanar photovoltaic
module. In other embodiments, some or all of the solar cells in the
nonplanar photovoltaic module will have the same surface area as
each other.
Methods of Forming Monolithically Integrated, Non-Planar
Photovoltaic Modules
[0068] FIG. 3 illustrates an overview of a method 300 of forming
monolithically integrated, non-planar photovoltaic modules, e.g.,
module 402 illustrated in FIGS. 2A-2F, according to some
embodiments of the present application. The individual steps in the
method, and structures formed during same, are described in greater
detail below with respect to FIGS. 4A-4I.
[0069] First, a back-electrode layer is disposed around an
elongated substrate (310). The substrate can be cylindrical, or
some other nonplanar shape (more below). The back-electrode layer
is deposited by any one of numerous methods, e.g., sputtering,
physical vapor deposition, or other suitable techniques, and as
described in greater detail below.
[0070] The back-electrode layer is then scribed about the substrate
(320). The scribing forms a single groove through the thickness of
the back electrode layer that traverses a perimeter of the back
electrode layer a plurality of times (wraps around the substrate a
plurality of times). In some embodiments, the back-electrode layer
is scribed with a laser scriber or with a mechanical scriber, e.g.,
a constant-force mechanical scriber such as that disclosed in U.S.
Patent Application No. 60/980,372, entitled "Constant Force
Mechanical Scribers and Methods for Using Same in Semiconductor
Processing Applications," the entire contents of which are
incorporated by reference herein. Further details of scribing are
described in greater detail below.
[0071] A semiconductor junction is then disposed on the
back-electrode layer (330). Some portions of the semiconductor
junction fill the groove that was previously scribed into the
back-electrode layer, thereby contacting the substrate. In some
embodiments, the semiconductor junction includes an absorber layer
and a junction partner layer, as described in greater detail
below.
[0072] The semiconductor junction is then scribed about the
substrate (340). The scribing forms a single groove through the
thickness of the semiconductor junction, along the length of the
substrate. The groove in the semiconductor junction is laterally
offset from the groove of the back-electrode formed at 320. In some
embodiments, the semiconductor junction is scribed with a laser
scriber or with a mechanical scriber.
[0073] A transparent conductor layer is then disposed on the
semiconductor junction (350). Some portions of the transparent
conductor layer fill the groove that was previously scribed into
the semiconductor junction, thereby contacting the
back-electrode.
[0074] The transparent conductor layer is then scribed about the
substrate (360). The scribing forms a single groove through the
thickness of the transparent conductor layer, along the length of
the substrate. The groove in the transparent conductor layer is
laterally offset from the groove of the back-electrode formed at
320 and the groove of the semiconductor junction formed at 340. In
some embodiments, the semiconductor junction is scribed with a
laser scriber or with a mechanical scriber.
[0075] The back-electrode layer, semiconductor junction, and
transparent conductor layer are then scribed along the length of
the substrate (370). The scribing defines a single groove
throughout the thicknesses of the back-electrode layer,
semiconductor junction, and transparent conductor layer along the
length of the substrate. The groove formed in 370, along with the
grooves formed at 320, 340, and 360, defines a plurality of solar
cells, each of which includes an isolated portion of the
back-electrode layer, an isolated portion of the semiconductor
junction, and an isolated portion of the transparent conductor
layer. In some embodiments, the groove is linear, while in other
embodiments the groove has a repeating or non-repeating pattern. In
some embodiments, the back-electrode layer, semiconductor junction,
and transparent conductor layer are scribed with a laser scriber or
with a mechanical scriber.
[0076] Optionally, the photovoltaic module is then encased in a
substantially transparent casing with filler (380).
[0077] The steps of method 300, and structures formed during same,
will now be discussed in greater detail with reference to FIGS.
4A-4I. However, the methods of forming a photovoltaic module 402
are not limited to the steps shown in FIGS. 3 and 4A to 4I.
Modifications and variations are contemplated.
[0078] Elongated, Nonplanar Substrate.
[0079] FIG. 4A illustrates a plan view and a cross-sectional view
along line 4A-4A' of an elongated, nonplanar substrate 102 upon
with a plurality of solar cells is to be formed, e.g., using the
method 300 illustrated in FIG. 3. The substrate 102 illustrated in
FIG. 4A has a cylindrical shape, but non-planar substrates are not
limited to being cylindrical in shape. In some embodiments, the
substrate 102 has a non-planar shape (more below). In some
embodiments, the substrate 102 is rigid.
[0080] In some embodiments, the elongated substrate 102 is made of
a plastic, metal, metal alloy, or glass, and can be solid (e.g., a
rod) or hollowed (e.g., a tube). As used herein, the term "tubular"
means objects having a tubular or approximately tubular shape. In
fact, tubular objects can have irregular shapes so long as the
object, taken as a whole, is roughly tubular.
[0081] In some embodiments, the substrate 102 is optically
transparent to wavelengths that are generally absorbed by the
semiconductor junction of a solar cell of the photovoltaic module,
while in other embodiments, the substrate 102 is not optically
transparent.
[0082] In some embodiments, the elongated substrate 102 of FIG. 2A
is made of a plastic, metal, metal alloy, glass, glass fibers,
glass tubing, or glass tubing. In some embodiments, the elongated
substrate 102 is made of a urethane polymer, an acrylic polymer, a
fluoropolymer, polybenzamidazole, polyimide,
polytetrafluoroethylene, polyetheretherketone, polyamide-imide,
glass-based phenolic, polystyrene, cross-linked polystyrene,
polyester, polycarbonate, polyethylene, polyethylene,
acrylonitrile-butadiene-styrene, polytetrafluoro-ethylene,
polymethacrylate, nylon 6,6, cellulose acetate butyrate, cellulose
acetate, rigid vinyl, plasticized vinyl, or polypropylene. In some
embodiments, substrate 102 is made of aluminosilicate glass,
borosilicate glass (e.g., PYREX, DURAN, SIMAX, etc.), dichroic
glass, germanium/semiconductor glass, glass ceramic, silicate/fused
silica glass, soda lime glass, quartz glass, chalcogenide/sulphide
glass, fluoride glass, pyrex glass, a glass-based phenolic,
cereated glass, or flint glass.
[0083] In some embodiments, the elongated substrate 102 is made of
a material such as polybenzamidazole (e.g., CELAZOLE.RTM.,
available from Boedeker Plastics, Inc., Shiner, Tex.). In some
embodiments, substrate 102 is made of polyimide (e.g., DUPONT.TM.
VESPEL.RTM., or DUPONT.TM. KAPTON.RTM., Wilmington, Del.). In some
embodiments, the elongated substrate 102 is made of
polytetrafluoroethylene (PTFE) or polyetheretherketone (PEEK), each
of which is available from Boedeker Plastics, Inc. In some
embodiments, the elongated substrate 102 is made of polyamide-imide
(e.g., TORLON.RTM. PAI, Solvay Advanced Polymers, Alpharetta,
Ga.).
[0084] In some embodiments, the elongated substrate 102 is made of
a glass-based phenolic. Phenolic laminates are made by applying
heat and pressure to layers of paper, canvas, linen or glass cloth
impregnated with synthetic thermosetting resins. When heat and
pressure are applied to the layers, a chemical reaction
(polymerization) transforms the separate layers into a single
laminated material with a "set" shape that cannot be softened
again. Therefore, these materials are called "thermosets." A
variety of resin types and cloth materials can be used to
manufacture thermoset laminates with a range of mechanical,
thermal, and electrical properties. In some embodiments, the
elongated substrate 102 is a phenoloic laminate having a NEMA grade
of G-3, G-5, G-7, G-9, G-10 or G-11. Exemplary phenolic laminates
are available from Boedeker Plastics, Inc.
[0085] In some embodiments, the substrate 102 is made of
polystyrene. Examples of polystyrene include general purpose
polystyrene and high impact polystyrene as detailed in Marks'
Standard Handbook for Mechanical Engineers, ninth edition, 1987,
McGraw-Hill, Inc., p. 6-174, which is hereby incorporated by
reference herein in its entirety. In still other embodiments, the
elongated substrate 102 is made of cross-linked polystyrene. One
example of cross-linked polystyrene is REXOLITE.degree. (C-Lec
Plastics, Inc). REXOLITE is a thermoset, in particular a rigid and
translucent plastic produced by cross linking polystyrene with
divinylbenzene.
[0086] In some embodiments, the elongated substrate 102 is a
polyester wire (e.g., a MYLAR.RTM. wire). MYLAR.RTM. is available
from DuPont Teijin Films (Wilmington, Del.). In still other
embodiments, the elongated substrate 102 is made of DURASTONE.RTM.,
which is made by using polyester, vinylester, epoxid and modified
epoxy resins combined with glass fibers (Roechling Engineering
Plastic Pte Ltd., Singapore).
[0087] In still other embodiments, the elongated substrate 102 is
made of polycarbonate. Such polycarbonates can have varying amounts
of glass fibers (e.g., 10% or more, 20% or more, 30% or more, or
40% or more) in order to adjust tensile strength, stiffness,
compressive strength, as well as the thermal expansion coefficient
of the material. Exemplary polycarbonates are ZELUX.RTM. M and
ZELUX.RTM. W, which are available from Boedeker Plastics, Inc.
[0088] In some embodiments, the elongated substrate 102 is made of
polyethylene. In some embodiments, the elongated substrate 102 is
made of low density polyethylene (LDPE), high density polyethylene
(HDPE), or ultra high molecular weight polyethylene (UHMW PE).
Chemical properties of HDPE are described in Marks' Standard
Handbook for Mechanical Engineers, ninth edition, 1987,
McGraw-Hill, Inc., p. 6-173, which is hereby incorporated by
reference herein in its entirety. In some embodiments, the
elongated substrate 102 is made of acrylonitrile-butadiene-styrene,
polytetrifluoroethylene (TEFLON), polymethacrylate (lucite or
plexiglass), nylon 6,6, cellulose acetate butyrate, cellulose
acetate, rigid vinyl, plasticized vinyl, or polypropylene. Chemical
properties of these materials are described in Marks' Standard
Handbook for Mechanical Engineers, ninth edition, 1987,
McGraw-Hill, Inc., pp. 6-172 through 6-175, which is hereby
incorporated by reference herein in its entirety.
[0089] Additional exemplary materials that can be used to form the
elongated substrate 102 are found in Modern Plastics Encyclopedia,
McGraw-Hill; Reinhold Plastics Applications Series, Reinhold Roff,
Fibres, Plastics and Rubbers, Butterworth; Lee and Neville, Epoxy
Resins, McGraw-Hill; Bilmetyer, Textbook of Polymer Science,
Interscience; Schmidt and Marlies, Principles of high polymer
theory and practice, McGraw-Hill; Beadle (ed.), Plastics,
Morgan-Grampiand, Ltd., 2 vols. 1970; Tobolsky and Mark (eds.),
Polymer Science and Materials, Wiley, 1971; Glanville, The
Plastics's Engineer's Data Book, Industrial Press, 1971; Mohr
(editor and senior author), Oleesky, Shook, and Meyers, SPI
Handbook of Technology and Engineering of Reinforced Plastics
Composites, Van Nostrand Reinhold, 1973, each of which is hereby
incorporated by reference herein in its entirety.
[0090] In some embodiments, a cross-section of the elongated
substrate 102 is cylindrical and has an outer diameter of between 3
mm and 100 mm, between 4 mm and 75 mm, between 5 mm and 50 mm,
between 10 mm and 40 mm, or between 14 mm and 17 mm. In some
embodiments, a cross-section of the elongated substrate 102 is
circumferential and has an outer diameter of between 1 mm and 1000
mm.
[0091] In some embodiments, the elongated substrate 102 is a tube
with a hollowed inner portion. In such embodiments, a cross-section
of the elongated substrate 102 is characterized by an inner radius
defining the hollowed interior and an outer radius. The difference
between the inner radius and the outer radius is the thickness of
the elongated substrate 102. In some embodiments, the thickness of
the elongated substrate 102 is between 0.1 mm and 20 mm, between
0.3 mm and 10 mm, between 0.5 mm and 5 mm, or between 1 mm and 2
mm. In some embodiments, the inner radius is between 1 mm and 100
mm, between 3 mm and 50 mm, or between 5 mm and 10 mm.
[0092] In some embodiments, the elongated substrate 102 has a
length (perpendicular to the plane defined by FIG. 3B) that is
between 5 mm and 10,000 mm, between 50 mm and 5,000 mm, between 100
mm and 3000 mm, or between 500 mm and 1500 mm. In one embodiment,
the elongated substrate 102 is a hollowed tube having an outer
diameter of 15 mm and a thickness of 1.2 mm, and a length of 1040
mm.
[0093] In some embodiments, the elongated substrate 102 has a width
dimension and a longitudinal dimension. In some embodiments, the
longitudinal dimension of the elongated substrate 102 is at least
four times greater than the width dimension. In other embodiments,
the longitudinal dimension of the elongated substrate 102 is at
least five times greater than the width dimension. In yet other
embodiments, the longitudinal dimension of the elongated substrate
102 is at least six times greater than the width dimension. In some
embodiments, the longitudinal dimension of the elongated substrate
102 is 10 cm or greater. In other embodiments, the longitudinal
dimension of the elongated substrate 102 is 50 cm or greater. In
some embodiments, the width dimension of the elongated substrate
102 is 1 cm or greater. In other embodiments, the width dimension
of the elongated substrate 102 is 5 cm or greater. In yet other
embodiments, the width dimension of the elongated substrate 102 is
10 cm or greater.
[0094] Disposing the Back-Electrode (310).
[0095] FIG. 4B illustrates a plan view and a cross-sectional view
along line 4B-4B' of a structure formed after disposing a
back-electrode 104 on an elongated non-planar substrate 102 (step
310 of FIG. 3). Techniques for disposing a back-electrode on a
substrate are known in the art and any such techniques can be
used.
[0096] In some embodiments, the back-electrode 104 is made out of
any material that can support the photovoltaic current generated by
a solar cell with negligible resistive losses. In some embodiments,
the back-electrode 104 is composed of any suitable conductive
material, such as aluminum, molybdenum, tungsten, vanadium,
rhodium, niobium, chromium, tantalum, titanium, steel, nickel,
platinum, silver, gold, an alloy thereof (e.g. Kovar), or any
combination thereof. In some embodiments, the back-electrode 104 is
composed of any suitable conductive material, such as indium tin
oxide, titanium nitride, tin oxide, fluorine doped tin oxide, doped
zinc oxide, aluminum doped zinc oxide, gallium doped zinc oxide,
boron dope zinc oxide indium-zinc oxide, a metal-carbon
black-filled oxide, a graphite-carbon black-filled oxide, a carbon
black-carbon black-filled oxide, a superconductive carbon
black-filled oxide, an epoxy, a conductive glass, or a conductive
plastic. A conductive plastic is one that, through compounding
techniques, contains conductive fillers which, in turn, impart
their conductive properties to the plastic. In some embodiments,
the conductive plastics used in the present application to form the
back-electrode 104 contain fillers that form sufficient conductive
current-carrying paths through the plastic matrix to support the
photovoltaic current generated by the solar cells with negligible
resistive losses. The plastic matrix of the conductive plastic is
typically insulating, but the composite produced exhibits the
conductive properties of the filler. In one embodiment, the
back-electrode 104 is made of molybdenum.
[0097] Scribing the Back-Electrode (320).
[0098] FIG. 4C illustrates a plan view and a cross-sectional view
along line 4C-4C' of a structure formed after scribing
back-electrode 104 about the substrate 102 (step 320 of FIG.
3).
[0099] FIG. 4C illustrates an embodiment having a single helical
groove 292 that has been cut into the back-electrode 104. In some
embodiments, the groove 292 is deep enough to expose a portion of
the surface of the substrate 102 underneath the back-electrode 104,
i.e., groove 292 extends throughout the thickness of the
back-electrode 104. The helical groove 292 need not be a "pure
helix," that is, there can be some variation (e.g., "wobble") in
the shape of the helix about the circumference of the substrate. As
noted above, the groove 292 need not be helical at all, but instead
can have a repeating or non-repeating pattern.
[0100] In some embodiments, the back-electrode groove 292 is cut
using laser scribing techniques. Methods of laser scribing a
photovoltaic module are known in the art, and in addition can be
found in U.S. patent application Ser. No. 11/499,608 filed Aug. 4,
2006, the entire contents of which are incorporated by reference
herein. In other embodiments, the back-electrode groove 292 is cut
using mechanical scribing techniques, e.g., constant-force
mechanical scribing, such as described in U.S. Patent Application
No. 60/980,372. A constant-force mechanical scriber can exert a
substantially constant force on the photovoltaic module during
scribing, regardless of the distance between the scriber and the
layer being scribed. Thus a constant-force mechanical scriber can
cut grooves such as back-electrode groove 292 with precision even
when non-symmetry exists in the substrate.
[0101] To scribe the back-electrode layer 104 with a scriber (e.g.,
a constant-force mechanical scriber), the scriber and the substrate
102 (with back-electrode 104 disposed thereon) are moved both
rotationally and translationally relative to each other. In some
embodiments only the substrate 102 is moved rotationally and
translationally, while in other embodiments only the scriber is
moved rotationally (moved about the substrate) and translationally
(laterally relative to the substrate), while in other embodiments
the scriber is moved translationally and the substrate 102 is moved
rotationally, while in other embodiments the substrate 102 is moved
translationally and the scriber is moved translationally, while in
still other embodiments both the substrate and the scriber are
moved both translationally and rotationally.
[0102] Suitable mechanisms for translating scribers and substrates
rotationally and/or translationally will be readily apparent to
those skilled in the art as well as in U.S. patent application Ser.
Nos. 60/922,290; 11/801,469; 11/801,723; 60/958,193 and 11/983,239,
each of which is hereby incorporated by reference herein in its
entirety.
[0103] In one example, the substrate is moved rotationally while
the scriber is moved translationally. In this example, the scriber
is engaged with the back-electrode layer at a first end of the
substrate. The scriber is translated laterally with at a constant
or nonconstant velocity and the substrate is rotated with a
velocity of between about 50 revolutions per minute (RPM) to about
3000 RPM, e.g., about 960 RPM. As the scriber moves laterally and
the substrate 102 moves rotationally, the scriber traces a groove
in the back-electrode layer 104 that traverses a plurality of times
about the substrate 102. In some embodiments, the groove thus
formed is helical, and the pitch of the helical groove is based on
the lateral velocity of the scriber and the rotational velocity of
the substrate, which in turn is based on the dimensions of the
substrate. In some embodiments, the width of the groove thus formed
in the back-electrode layer 104 is, on average, from about 10
microns to about 150 microns, e.g., about 90 microns. In some
embodiments, the width of the groove is determined by the
dimensions of the scriber (e.g., the shape of the laser or knife
used to scribe the groove). When the scriber reaches the second end
of the substrate, the scriber is disengaged from the back-electrode
layer. In some embodiments, the groove is cleaned after groove
formation. In some embodiments, the groove is not cleaned after
groove formation.
[0104] Disposing the Semiconductor Junction (330).
[0105] FIG. 4D illustrates a plan view and a cross-sectional view
along line 4D-4D' of a structure formed after disposing a nonplanar
semiconductor junction, e.g., absorber layer 106 and junction
partner layer 108, on the back-electrode 104 (step 330 of FIG. 3).
Portions of the semiconductor junction, e.g., portions of absorber
layer 106 and/or junction partner layer 108, fill in the
back-electrode groove 292 cut into the back-electrode.
[0106] In general, the semiconductor junction can be any
photovoltaic homojunction, heterojunction, heteroface junction,
buried homojunction, p-i-n junction or a tandem junction having an
absorber layer that is a direct band-gap absorber (e.g.,
crystalline silicon) or an indirect band-gap absorber (e.g.,
amorphous silicon). Such junctions are described in Chapter 1 of
Bube, Photovoltaic Materials, 1998, Imperial College Press, London,
as well as Lugue and Hegedus, 2003, Handbook of Photovoltaic
Science and Engineering, John Wiley & Sons, Ltd., West Sussex,
England, each of which is hereby incorporated by reference herein
in its entirety. Details of exemplary types of semiconductors
junctions in accordance with the present application are disclosed
below. In addition to the exemplary junctions disclosed below, such
semiconductor junctions can be multi junctions in which light
traverses into the core of the junction through multiple junctions
that, in some embodiments, have successfully smaller band gaps.
[0107] Optionally, the semiconductor junction includes an intrinsic
layer (i-layer) (not shown) disposed on junction partner layer 108.
The i-layer can be formed using, for example, any undoped
transparent oxide including, but not limited to, zinc oxide, metal
oxide, or any transparent material that is highly insulating. In
some embodiments, the i-layer is highly pure zinc oxide.
[0108] In some embodiments, the absorber layer 106 includes
copper-indium-gallium-diselenide (CIGS). Different examples of
suitable layers for use in the semiconductor junction, and methods
of making same, are described in greater detail below.
[0109] Scribing the Semiconductor Junction (340).
[0110] FIG. 4E illustrates a plan view and a cross-sectional view
along line 4E-4E' of a structure formed after scribing the
semiconductor junction, e.g., the junction partner layer 108 and
the absorber layer 106, a plurality of times about the substrate
102 (step 340 of FIG. 3).
[0111] FIG. 4E illustrates an embodiment in which a single helical
groove 294 has been cut into the junction partner layer 108 and the
absorber layer 106. In some embodiments, the groove 294 is deep
enough to expose a portion of the surface of the back-electrode 104
underneath the junction partner layer 108 and the absorber layer
106, i.e., the groove 294 extends throughout the thickness of the
junction partner layer 108 and the absorber layer 106. The helical
groove 294 need not be a "pure helix," that is, there can be some
variation (e.g., "wobble") in the shape of the helix about the
circumference of the substrate. As noted above, the groove 294 need
not be helical at all, but instead can have a repeating or
non-repeating pattern.
[0112] In some embodiments, mechanical scribing (e.g.,
constant-force mechanical scribing) is used to create the
semiconductor junction groove 294, in order to reduce
non-uniformities that can arise from non-symmetries in the solar
cell. As described above with respect to FIG. 4C, there are several
options for rotational and/or translational movement of the
substrate 102 and/or the scriber, the implementation of which will
be apparent to those skilled in the art.
[0113] In some embodiments, semiconductor junction groove 294 is
formed while rotating the substrate at a speed of about 50 RPM to
about 3000 RPM, e.g., 500 RPM, and translating the scriber at a
constant velocity or at variable velocities. In some embodiments,
the semiconductor junction groove 294 has an average width from
about 50 microns to about 150 microns, e.g., about 80 microns. The
pitch of the groove 294 can be substantially the same as the pitch
of the groove 292.
[0114] Disposing the Transparent Conductor Layer (350).
[0115] FIG. 4F illustrates a plan view and a cross-sectional view
along line 4F-4F' of a structure formed after disposing a nonplanar
transparent conductor layer 110 on the semiconductor layer, e.g.,
on the scribed junction partner layer 108 and scribed absorber
layer 106 (step 350 of FIG. 3). Portions of the transparent
conductor layer 110 fill the back-electrode groove 294, and enable
monolithic integration of solar cells in photovoltaic module 420 by
providing an electrical communication pathway between the
transparent conductor layer portion of one solar cell and the
back-electrode portion of an adjacent solar cell. Methods of
forming transparent conductor layers are known in the art.
[0116] In some embodiments, the transparent conductor 110 is made
of tin oxide SnO.sub.x (with or without fluorine doping),
indium-tin oxide (ITO), doped zinc oxide (e.g., aluminum doped zinc
oxide, gallium doped zinc oxide, boron doped zinc oxide),
indium-zinc oxide or any combination thereof. In some embodiments,
the transparent conductor 110 is either p-doped or n-doped. For
example, in embodiments where the outer layer of the junction 410
is p-doped, the transparent conductor 110 can be p-doped. Likewise,
in embodiments where the outer layer of junction 410 is n-doped,
the transparent conductor 110 can be n-doped. In general, the
transparent conductor 110 is preferably made of a material that has
very low resistance, suitable optical transmission properties
(e.g., transmits greater than 90% of the spectrum the semiconductor
junction uses to generate electricity), and a deposition
temperature that will not damage underlying layers 108, 106, 104,
or substrate 102.
[0117] In some embodiments, the transparent conductor 110 includes
carbon nanotubes. Carbon nanotubes are commercially available, for
example, from Eikos (Franklin, Mass.) and are described in U.S.
Pat. No. 6,988,925, which is hereby incorporated by reference
herein in its entirety. In some embodiments, the transparent
conductor 110 is an electrically conductive polymer material such
as a conductive polythiophene, a conductive polyaniline, a
conductive polypyrrole, a PSS-doped PEDOT (e.g., Bayrton), or a
derivative of any of the foregoing.
[0118] In some embodiments, the transparent conductor 110 includes
more than one layer, e.g., a first layer including tin oxide
SnO.sub.x (with or without fluorine doping), indium-tin oxide
(ITO), indium-zinc oxide, doped zinc oxide (e.g., aluminum doped
zinc oxide, gallium doped zinc oxide, boron doped zinc oxide) or a
combination thereof and a second layer including a conductive
polythiophene, a conductive polyaniline, a conductive polypyrrole,
a PSS-doped PEDOT (e.g., Bayrton), or a derivative of any of the
foregoing. Additional suitable materials that can be used to form
the transparent conductor 110 are disclosed in United States Patent
publication 2004/0187917A1 to Pichler, which is hereby incorporated
by reference herein in its entirety.
[0119] Scribing the Transparent Conductor Layer (370).
[0120] FIG. 4G illustrates a plan view and a cross-sectional view
along line 4G-4G' of a structure formed after scribing the
transparent conductor layer 110 about the substrate 102 (step 360
of FIG. 3).
[0121] FIG. 4G illustrates an embodiment having a single helical
groove 296 that has been cut into the transparent conductor layer
110. In some embodiments, the groove 296 is deep enough to expose a
portion of the surface of the junction partner layer 108 underneath
the transparent conductor layer 110, i.e., the groove 296 extends
throughout the thickness of the transparent conductor layer 110.
The helical groove 296 need not be a "pure helix," that is, there
can be some variation (e.g., "wobble") in the shape of the helix
about the circumference of the substrate. As noted above, the
groove 292 need not be helical at all, but instead can have a
repeating or non-repeating pattern.
[0122] In some embodiments, mechanical scribing (e.g.,
constant-force mechanical scribing) is used to create the
transparent conductor groove 296, in order to reduce
non-uniformities that can arise from non-symmetries in the solar
cell. As described above with respect to FIG. 4C, there are several
options for rotational and/or translational movement of the
substrate 102 and/or the scriber, the implementation of which will
be apparent to those skilled in the art.
[0123] In some embodiments, the substrate is rotated at a speed of
about 50 RPM to about 3000 RPM, e.g., 500 RPM, while scribing the
semiconductor junction groove 294. In some embodiments, the
semiconductor junction groove 294 has an average width from about
50 microns to about 300 microns, e.g., about 150 microns. In
embodiments in which the grooves 292 and 294 are helical, the pitch
of the groove 294 can be substantially the same as the pitch of the
groove 292.
[0124] Scribing the Back-Electrode Layer, Semiconductor Junction,
and Transparent Conductor Layer (370).
[0125] FIG. 4H illustrates a plan view and a cross-sectional view
along line 4H-4H' of a structure formed after scribing the
back-electrode layer 104, semiconductor junction (e.g., junction
partner layer 108 and absorber layer 106), and transparent
conductor layer 110 along the length of the substrate 102 (step 370
of FIG. 3).
[0126] FIG. 4H illustrates a single groove 300 that has been cut
into the back-electrode layer 104, absorber layer 106, junction
partner layer 108, and transparent conductor layer 110. In some
embodiments, the groove 300 is deep enough to expose a portion of
the surface of the substrate 102, i.e., the groove 300 extends
throughout the thickness of the back-electrode layer 104, absorber
layer 106, junction partner layer 108, and transparent conductor
layer 110. Although FIG. 4H illustrates a linear groove 300, the
groove 300 need not be linear. For example, the groove 300 can be
wavy, jagged, or have various regular or irregular features, so
long as groove 300 generally extends along the length of substrate
120, and that grooves 292, 294, 296, and 300 together divide layers
104, 106, 108, and 110 into separate respective portions.
[0127] In some embodiments, mechanical scribing (e.g.,
constant-force mechanical scribing) is used to create groove 300,
while in other embodiments, laser scribing is used to create groove
300. To form groove 300, the scriber and the substrate 102 are
laterally translated relative to each other, e.g., only the scriber
is laterally translated, only the substrate is laterally
translated, or both the scriber and the substrate are laterally
translated. The implementations of such translations will be
apparent to those skilled in the art.
[0128] Optionally Encasing the Module (380).
[0129] FIG. 4I illustrates a plan view and a cross-sectional view
along line 4I-4I' of a structure formed after optionally encasing
the substrate, scribed back-electrode layer 104, scribed
semiconductor junction (e.g., junction partner layer 108 and
absorber layer 106), and scribed transparent conductor layer 110,
in a nonplanar casing with filler (step 380 of FIG. 3).
[0130] In the embodiment illustrated in FIG. 4I, the transparent
casing 310 is disposed on top of the transparent conductor 110. In
some embodiments, an optional filler layer (not shown in FIG. 3H)
is disposed on the transparent conductor 110, and then, optionally,
a transparent casing is disposed on top of the filler layer. The
optional transparent casing 310 helps to protect the solar cells in
photovoltaic module 420 from the environment. In some embodiments,
the transparent casing 310 is circumferentially disposed on
transparent conductor 110 and/or optional filler layer 330. In some
embodiments, the transparent casing 310 is made of plastic or
glass. Methods, such as heat shrinking, injection molding, or
vacuum loading, can be used to construct transparent tubular casing
310 such that oxygen and water is excluded from the system. In some
embodiments, the transparent casing 310 has a cylindrical
shape.
[0131] In some embodiments, the transparent casing 310 is made of a
urethane polymer, an acrylic polymer, polymethylmethacrylate
(PMMA), a fluoropolymer, silicone, poly-dimethyl siloxane (PDMS),
silicone gel, epoxy, ethylene vinyl acetate (EVA), perfluoroalkoxy
fluorocarbon (PFA), nylon/polyamide, cross-linked polyethylene
(PEX), polyolefin, polypropylene (PP), polyethylene terephtalate
glycol (PETG), polytetrafluoroethylene (PTFE), thermoplastic
copolymer (for example, ETFE.RTM., which is a derived from the
polymerization of ethylene and tetrafluoroethylene: TEFLON.RTM.
monomers), polyurethane/urethane, polyvinyl chloride (PVC),
polyvinylidene fluoride (PVDF), TYGON.RTM., vinyl, VITON.RTM., or
any combination or variation thereof.
[0132] In some embodiments, the transparent casing 310 includes a
plurality of casing layers. In some embodiments, each casing layer
is composed of a different material. For example, in some
embodiments, the transparent casing 310 includes a first
transparent casing layer and a second transparent casing layer.
Depending on the exact configuration of the photovoltaic module,
the first transparent casing layer can be disposed on the
transparent conductor 110, optional filler layer 330 or a water
resistant layer. The second transparent casing layer can be
disposed on the first transparent casing layer.
[0133] In some embodiments, each transparent casing layer has
different properties. In one example, the outer transparent casing
layer has excellent UV shielding properties whereas the inner
transparent casing layer has good water proofing characteristics.
Moreover, the use of multiple transparent casing layers can be used
to reduce costs and/or improve the overall properties of the
transparent casing 310. For example, one transparent casing layer
may be made of an expensive material that has a desired physical
property. By using one or more additional transparent casing
layers, the thickness of the expensive transparent casing layer may
be reduced, thereby achieving a savings in material costs. In
another example, one transparent casing layer may have excellent
optical properties (e.g., index of refraction, etc.) but be very
heavy. By using one or more additional transparent casing layers,
the thickness of the heavy transparent casing layer may be reduced,
thereby reducing the overall weight of transparent casing 310. In
some embodiments, only one end of the photovoltaic module is
exposed by transparent casing 310 in order to form an electrical
connection with adjacent solar cells or other circuitry. In some
embodiments, both ends of the elongated photovoltaic module are
exposed by transparent casing 310 in order to form an electrical
connection with adjacent solar cells 12 or other circuitry. More
discussion of transparent casings 310 that can be used in some
embodiments of the present application is disclosed in U.S. patent
application Ser. No. 11/378,847, which is hereby incorporated by
reference herein in its entirety. Additional optional layers that
can be disposed on the transparent casing 310 or the optional
filler layer 330 are discussed below.
[0134] Although the casing 310 is referred to as "transparent," it
should be recognized that most materials are only partially
transparent, e.g., will reflect and/or absorb at least a small
fraction of the light impinging it. As used herein, "transparent"
means that at least a portion of impinging visible light transmits
through the material.
[0135] The filler layer 330 can also be used to protect the solar
cell 12 from physical or other damage, and can also be used to aid
the solar cell in collecting more light by its optical and chemical
properties.
[0136] The layer 330 can be made of sealant such as ethylene vinyl
acetate (EVA), silicone, silicone gel, epoxy, polydimethyl siloxane
(PDMS), RTV silicone rubber, polyvinyl butyral (PVB), thermoplastic
polyurethane (TPU), a polycarbonate, an acrylic, a fluoropolymer,
and/or a urethane, and can be coated over the transparent conductor
110 to seal out air and, optionally, to provide complementary
fitting to a transparent casing 310. In some embodiments, the
filler layer 330 is a Q-type silicone, a silsequioxane, a D-type
silicone, or an M-type silicone.
[0137] In one embodiment, the substance used to form a filler layer
330 includes a resin or resin-like substance, the resin potentially
being added as one component, or added as multiple components that
interact with one another to effect a change in viscosity. In
another embodiment, the resin can be diluted with a less viscous
material, such as a silicone-based oil or liquid acrylates. In
these cases, the viscosity of the initial substance can be far less
than that of the resin material itself.
[0138] In one example, a medium viscosity polydimethylsiloxane
mixed with an elastomer-type dielectric gel can be used to make the
filler layer 330. In one case, as an example, a mixture of 85% (by
weight) Dow Corning 200 fluid, 50 centistoke viscosity (PDMS,
polydimethylsiloxane); 7.5% Dow Corning 3-4207 Dielectric Tough
Gel, Part A--Resin; and 7.5% Dow Corning 3-4207 Dielectric Tough
Gel, Part B--Catalyst is used to form the filler layer 330. Other
oils, gels, or silicones can be used to produce much of what is
described in this disclosure and, accordingly, this disclosure
should be read to include those other oils, gels and silicones to
generate a filler layer 330. Such oils include silicone-based oils,
and the gels include many commercially available dielectric gels.
Curing of silicones can also extend beyond a gel like state.
Commercially available dielectric gels and silicones and the
various formulations are contemplated as being usable in this
disclosure.
[0139] In one example, the composition used to form the filler
layer 330 is 85%, by weight, polydimethylsiloxane polymer liquid,
where the polydimethylsiloxane has the chemical formula
(CH.sub.3).sub.3SiO[SiO(CH.sub.3).sub.2].sub.nSi(CH.sub.3).sub.3,
where n is a range of integers chosen such that the polymer liquid
has an average bulk viscosity that falls in the range between 50
centistokes and 100,000 centistokes (all viscosity values given
herein for compositions assume that the compositions are at room
temperature). Thus, there may be polydimethylsiloxane molecules in
the polydimethylsiloxane polymer liquid with varying values for n
provided that the bulk viscosity of the liquid falls in the range
between 50 centistokes and 100,000 centistokes. Bulk viscosity of
the polydimethylsiloxane polymer liquid may be determined by any of
a number of methods known to those of skill in the art, such as
using a capillary viscometer. Further, the composition includes
7.5%, by weight, of a silicone elastomer including at least sixty
percent, by weight, dimethylvinyl-terminated dimethyl siloxane (CAS
number 68083-19-2) and between 3 and 7 percent by weight silicate
(New Jersey TSRN 14962700-537 6P). Further, the composition
includes 7.5%, by weight, of a silicone elastomer including at
least sixty percent, by weight, dimethylvinyl-terminated dimethyl
siloxane (CAS number 68083-19-2), between ten and thirty percent by
weight hydrogen-terminated dimethyl siloxane (CAS 70900-21-9) and
between 3 and 7 percent by weight trimethylated silica (CAS number
68909-20-6).
[0140] In some embodiments, the filler layer 330 is formed by soft
and flexible optically suitable material such as silicone gel. For
example, in some embodiments, the filler layer 330 is formed by a
silicone gel such as a silicone-based adhesive or sealant. In some
embodiments, the filler layer 330 is formed by GE RTV 615 Silicone.
RTV 615 is an optically clear, two-part flowable silicone product
that requires SS4120 as primer for polymerization (RTV615-1P), both
available from General Electric (Fairfield, Conn.). Silicone-based
adhesives or sealants are based on tough silicone elastomeric
technology. The characteristics of silicone-based materials, such
as adhesives and sealants, are controlled by three factors: resin
mixing ratio, potting life and curing conditions.
[0141] Advantageously, silicone adhesives have a high degree of
flexibility and very high temperature resistance (up to 600.degree.
F.). Silicone-based adhesives and sealants have a high degree of
flexibility. Silicone-based adhesives and sealants are available in
a number of technologies (or cure systems). These technologies
include pressure sensitive, radiation cured, moisture cured,
thermo-set and room temperature vulcanizing (RTV). In some
embodiments, the silicone-based sealants use two-component addition
or condensation curing systems or single component (RTV) forms. RTV
forms cure easily through reaction with moisture in the air and
give off acid fumes or other by-product vapors during curing.
[0142] Pressure sensitive silicone adhesives adhere to most
surfaces with very slight pressure and retain their tackiness. This
type of material forms viscoelastic bonds that are aggressively and
permanently tacky, and adheres without the need of more than finger
or hand pressure. In some embodiments, radiation is used to cure
silicone-based adhesives. In some embodiments, ultraviolet light,
visible light or electron bean irradiation is used to initiate
curing of sealants, which allows a permanent bond without heating
or excessive heat generation. While UV-based curing requires one
substrate to be UV transparent, the electron beam can penetrate
through material that is opaque to UV light. Certain silicone
adhesives and cyanoacrylates based on a moisture or water curing
mechanism may need additional reagents properly attached to the
photovoltaic module 402 without affecting the proper functioning of
the solar cells 12 of the photovoltaic module. Thermo-set silicone
adhesives and silicone sealants are cross-linked polymeric resins
cured using heat or heat and pressure. Cured thermo-set resins do
not melt and flow when heated, but they may soften. Vulcanization
is a thermosetting reaction involving the use of heat and/or
pressure in conjunction with a vulcanizing agent, resulting in
greatly increased strength, stability and elasticity in rubber-like
materials. RTV silicone rubbers are room temperature vulcanizing
materials. The vulcanizing agent is a cross-linking compound or
catalyst. In some embodiments in accordance with the present
application, sulfur is added as the traditional vulcanizing
agent.
[0143] In one example, the composition used to form a filler layer
330 is silicone oil mixed with a dielectric gel. The silicone oil
is a polydimethylsiloxane polymer liquid, whereas the dielectric
gel is a mixture of a first silicone elastomer and a second
silicone elastomer. As such, the composition used to form the
filler layer 330 is X %, by weight, polydimethylsiloxane polymer
liquid, Y %, by weight, a first silicone elastomer, and Z %, by
weight, a second silicone elastomer, where X, Y, and Z sum to 100.
Here, the polydimethylsiloxane polymer liquid has the chemical
formula
(CH.sub.3).sub.3SiO[SiO(CH.sub.3).sub.2].sub.nSi(CH.sub.3).sub.3,
where n is a range of integers chosen such that the polymer liquid
has an average bulk viscosity that falls in the range between 50
centistokes and 100,000 centistokes. Thus, there may be
polydimethylsiloxane molecules in the polydimethylsiloxane polymer
liquid with varying values for n provided that the bulk viscosity
of the liquid falls in the range between 50 centistokes and 100,000
centistokes. The first silicone elastomer includes at least sixty
percent, by weight, dimethylvinyl-terminated dimethyl siloxane (CAS
number 68083-19-2) and between 3 and 7 percent by weight silicate
(New Jersey TSRN 14962700-537 6P). Further, the second silicone
elastomer includes at least sixty percent, by weight,
dimethylvinyl-terminated dimethyl siloxane (CAS number 68083-19-2),
between ten and thirty percent by weight hydrogen-terminated
dimethyl siloxane (CAS 70900-21-9) and between 3 and 7 percent by
weight trimethylated silica (CAS number 68909-20-6). In this
embodiment, X may range between 30 and 90, Y may range between 2
and 20, and Z may range between 2 and 20, provided that X, Y and Z
sum to 100 percent.
[0144] In another example, the composition used to form the filler
layer 330 is silicone oil mixed with a dielectric gel. The silicone
oil is a polydimethylsiloxane polymer liquid, whereas the
dielectric gel is a mixture of a first silicone elastomer and a
second silicone elastomer. As such, the composition used to form
the filler layer 330 is X %, by weight, polydimethylsiloxane
polymer liquid, Y %, by weight, a first silicone elastomer, and Z
%, by weight, a second silicone elastomer, where X, Y, and Z sum to
100. Here, the polydimethylsiloxane polymer liquid has the chemical
formula
(CH.sub.3).sub.3SiO[SiO(CH.sub.3).sub.2].sub.nSi(CH.sub.3).sub.3,
where n is a range of integers chosen such that the polymer liquid
has a volumetric thermal expansion coefficient of at least
500.times.10.sup.-6/.degree. C. Thus, there may be
polydimethylsiloxane molecules in the polydimethylsiloxane polymer
liquid with varying values for n provided that the polymer liquid
has a volumetric thermal expansion coefficient of at least
960.times.10.sup.-6/.degree. C. The first silicone elastomer
includes at least sixty percent, by weight,
dimethylvinyl-terminated dimethyl siloxane (CAS number 68083-19-2)
and between 3 and 7 percent by weight silicate (New Jersey TSRN
14962700-537 6P). Further, the second silicone elastomer includes
at least sixty percent, by weight, dimethylvinyl-terminated
dimethyl siloxane (CAS number 68083-19-2), between ten and thirty
percent by weight hydrogen-terminated dimethyl siloxane (CAS
70900-21-9) and between 3 and 7 percent by weight trimethylated
silica (CAS number 68909-20-6). In this embodiment, X may range
between 30 and 90, Y may range between 2 and 20, and Z may range
between 2 and 20, provided that X, Y and Z sum to 100 percent.
[0145] In some embodiments, the composition used to form the filler
layer 330 is a crystal clear silicone oil mixed with a dielectric
gel. In some embodiments, the filler layer has a volumetric thermal
coefficient of expansion of greater than
250.times.10.sup.-6/.degree. C., greater than
300.times.10.sup.-6/.degree. C., greater than
400.times.10.sup.-6/.degree. C., greater than
500.times.10.sup.-6/.degree. C., greater than
1000.times.10.sup.-6/.degree. C., greater than
2000.times.10.sup.-6/.degree. C., greater than
5000.times.10.sup.-6/.degree. C., or between
250.times.10.sup.-6/.degree. C. and 10000.times.10.sup.-6/.degree.
C.
[0146] In some embodiments, a silicone-based dielectric gel can be
used in-situ to form the filler layer 330. The dielectric gel can
also be mixed with a silicone based oil to reduce both beginning
and ending viscosities. The ratio of silicone-based oil by weight
in the mixture can be varied. The percentage of silicone-based oil
by weight in the mixture of silicone-based oil and silicone-based
dielectric gel can have values at or about (e.g. .+-.2.5%) 25%,
30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 85%. Ranges
of 20%-30%, 25%-35%, 30%-40%, 35%-45%, 40%-50%, 45%-55%, 50%-60%,
55%-65%, 60%-70%, 65%-75%, 70%-80%, 75%-85%, and 80%-90% (by
weight) are also contemplated. Further, these same ratios by weight
can be contemplated for the mixture when using other types of oils
or acrylates instead of or in addition to silicon-based oil to
lessen the beginning viscosity of the gel mixture alone.
[0147] The initial viscosity of the mixture of 85% Dow Corning 200
fluid, 50 centistoke viscosity (PDMS, polydimethylsiloxane); 7.5%
Dow Corning 3-4207 Dielectric Tough Gel, Part A--Resin 7.5% Dow
Corning 3 4207 Dielectric Tough Gel, Part B--Pt Catalyst is
approximately 100 centipoise (cP). Beginning viscosities of less
than 1, less than 5, less than 10, less than 25, less than 50, less
than 100, less than 250, less than 500, less than 750, less than
1000, less than 1200, less than 1500, less than 1800, and less than
2000 cP are imagined, and any beginning viscosity in the range
1-2000 cP is acceptable. Other ranges can include 1-10 cP, 10-50
cP, 50-100 cP, 100-250 cP, 250-500 cP, 500-750 cP, 750-1000 cP,
800-1200 cP, 1000-1500 cP, 1250-1750 cP, 1500-2000 cP, and
1800-2000 cP. In some cases an initial viscosity between 1000 cP
and 1500 cP can also be used.
[0148] A final viscosity for the filler layer 330 of well above the
initial viscosity is envisioned in some embodiments. In most cases,
a ratio of the final viscosity to the beginning viscosity is at
least 50:1. With lower beginning viscosities, the ratio of the
final viscosity to the beginning viscosity may be 20,000:1, or in
some cases, up to 50,000:1. In most cases, a ratio of the final
viscosity to the beginning viscosity of between 5,000:1 to
20,000:1, for beginning viscosities in the 10 cP range, may be
used. For beginning viscosities in the 1000 cP range, ratios of the
final viscosity to the beginning viscosity between 50:1 to 200:1
are imagined. In short order, ratios in the ranges of 200:1 to
1,000:1, 1,000:1 to 2,000:1, 2,000:1 to 5,000:1, 5,000:1 to
20,000:1, 20,000:1 to 50,000:1, 50,000:1 to 100,000:1, 100,000:1 to
150,000:1, and 150,000:1 to 200,000:1 are contemplated.
[0149] The final viscosity of the filler layer 330 is typically on
the order of 50,000 cP to 200,000 cP. In some cases, a final
viscosity of at least 1.times.10.sup.6 cP is envisioned. Final
viscosities of at least 50,000 cP, at least 60,000 cP, at least
75,000 cP, at least 100,000 cP, at least 150,000 cP, at least
200,000 cP, at least 250,000 cP, at least 300,000 cP, at least
500,000 cP, at least 750,000 cP, at least 800,000 cP, at least
900,000 cP, and at least 1.times.10.sup.6 cP are found in
alternative embodiments. Ranges of final viscosity for the filler
layer can include 50,000 cP to 75,000 cP, 60,000 cP to 100,000 cP,
75,000 cP to 150,000 cP, 100,000 cP to 200,000 cP, 100,000 cP to
250,000 cP, 150,000 cP to 300,000 cP, 200,000 cP to 500,000 cP,
250,000 cP to 600,000 cP, 300,000 cP to 750,000 cP, 500,000 cP to
800,000 cP, 600,000 cP to 900,000 cP, and 750,000 cP to
1.times.10.sup.6 cP.
[0150] Curing temperatures for the filler layer 330 can be
numerous, with a common curing temperature of room temperature. The
curing step need not involve adding thermal energy to the system.
Temperatures that can be used for curing can be envisioned (with
temperatures in degrees F.) at up to 60 degrees, up to 65 degrees,
up to 70 degrees, up to 75 degrees, up to 80 degrees, up to 85
degrees, up to 90 degrees, up to 95 degrees, up to 100 degrees, up
to 105 degrees, up to 110 degrees, up to 115 degrees, up to 120
degrees, up to 125 degrees, and up to 130 degrees, and temperatures
generally between 55 and 130 degrees. Other curing temperature
ranges can include 60-85 degrees, 70-95 degrees, 80-110 degrees,
90-120 degrees, and 100-130 degrees.
[0151] The working time of the substance of a mixture can be varied
as well. The working time of a mixture in this context means the
time for the substance (e.g., the substance used to form the filler
layer 330) to cure to a viscosity more than double the initial
viscosity when mixed. Working time for the layer can be varied. In
particular, working times of less than 5 minutes, on the order of
10 minutes, up to 30 minutes, up to 1 hour, up to 2 hours, up to 4
hours, up to 6 hours, up to 8 hours, up to 12 hours, up to 18
hours, and up to 24 hours are all contemplated. A working time of 1
day or less is found to be best in practice. Any working time
between 5 minutes and 1 day is acceptable.
[0152] In context of this disclosure, resin can mean both synthetic
and natural substances that have a viscosity prior to curing and a
greater viscosity after curing. The resin can be unitary in nature,
or may be derived from the mixture of two other substances to form
the resin.
[0153] In some embodiments, the filler layer 330 is a laminate
layer such as any of those disclosed in U.S. Provisional patent
application No. 60/906,901, filed Mar. 13, 2007, entitled "A
Photovoltaic Apparatus Having a Laminate Layer and Method for
Making the Same" which is hereby incorporated by reference herein
in its entirety. In some embodiments, the filler layer 330 has a
viscosity of less than 1.times.10.sup.6 cP. In some embodiments,
the filler layer 330 has a thermal coefficient of expansion of
greater than 500.times.10.sup.-6/.degree. C. or greater than
1000.times.10.sup.-6/.degree. C. In some embodiments, the filler
layer 330 includes epolydimethylsiloxane polymer. In some
embodiments, the filler layer 330 includes by weight: less than 50%
of a dielectric gel or components to form a dielectric gel; and at
least 30% of a transparent silicone oil, the transparent silicone
oil having a beginning viscosity of no more than half of the
beginning viscosity of the dielectric gel or components to form the
dielectric gel. In some embodiments, the filler layer 330 has a
thermal coefficient of expansion of greater than
500.times.10.sup.-6/.degree. C. and includes by weight: less than
50% of a dielectric gel or components to form a dielectric gel; and
at least 30% of a transparent silicone oil. In some embodiments,
the filler layer 330 is formed from silicone oil mixed with a
dielectric gel. In some embodiments, the silicone oil is a
polydimethylsiloxane polymer liquid and the dielectric gel is a
mixture of a first silicone elastomer and a second silicone
elastomer. In some embodiments, the filler layer 330 is formed from
X %, by weight, polydimethylsiloxane polymer liquid, Y %, by
weight, a first silicone elastomer, and Z %, by weight, a second
silicone elastomer, where X, Y, and Z sum to 100. In some
embodiments, the polydimethylsiloxane polymer liquid has the
chemical formula
(CH.sub.3).sub.3SiO[SiO(CH.sub.3).sub.2].sub.nSi(CH.sub.3).sub.3,
where n is a range of integers chosen such that the polymer liquid
has an average bulk viscosity that falls in the range between 50
centistokes and 100,000 centistokes. In some embodiments, first
silicone elastomer includes at least sixty percent, by weight,
dimethylvinyl-terminated dimethyl siloxane and between 3 and 7
percent by weight silicate. In some embodiments, the second
silicone elastomer includes: (i) at least sixty percent, by weight,
dimethylvinyl-terminated dimethyl siloxane; (ii) between ten and
thirty percent by weight hydrogen-terminated dimethyl siloxane; and
(iii) between 3 and 7 percent by weight trimethylated silica. In
some embodiments, X is between 30 and 90; Y is between 2 and 20;
and Z is between 2 and 20.
[0154] In some embodiments, the filler layer 330 includes a
silicone gel composition, including: (A) 100 parts by weight of a
first polydiorganosiloxanc containing an average of at least two
silicon-bonded alkenyl groups per molecule and having a viscosity
of from 0.2 to 10 Pas at 25.degree. C.; (B) at least about 0.5 part
by weight to about 10 parts by weight of a second
polydiorganosiloxane containing an average of at least two
silicon-bonded alkenyl groups per molecule, wherein the second
polydiorganosiloxane has a viscosity at 25.degree. C. of at least
four times the viscosity of the first polydiorganosiloxane at
25.degree. C.; (C) an organohydrogensiloxane having the average
formula R.sub.7Si(SiOR.sup.8.sub.2H).sub.3 where R.sup.7 is an
alkyl group having 1 to 18 carbon atoms or aryl, R.sup.8 is an
alkyl group having 1 to 4 carbon atoms, in an amount sufficient to
provide from 0.1 to 1.5 silicon-bonded hydrogen atoms per alkenyl
group in components (A) and (B) combined; and (D) a hydrosilylation
catalyst in an amount sufficient to cure the composition as
disclosed in U.S. Pat. No. 6,169,155, which is hereby incorporated
by reference herein in its entirety.
Exemplary Semiconductor Junctions
[0155] Some examples of semiconductor junctions suitable for use in
photovoltaic module 402 will now be described with reference to
FIGS. 5A and 5B.
[0156] Referring to FIG. 5A, in one embodiment, the semiconductor
junction 410 is a heterojunction between an absorber layer 502,
disposed on the back-electrode 104, and a junction partner layer
504, disposed on the absorber layer 502. Layers 502 and 504 include
different semiconductors with different band gaps and electron
affinities such that junction partner layer 504 has a larger band
gap than the absorber layer 502. In some embodiments, the absorber
layer 502 is p-doped and the junction partner layer 504 is n-doped.
In such embodiments, the transparent conductor 110 is n+-doped. In
alternative embodiments, the absorber layer 502 is n-doped and the
junction partner layer 504 is p-doped. In such embodiments, the
transparent conductor 110 is p+-doped. In some embodiments, the
semiconductors listed in Pandey, Handbook of Semiconductor
Electrodeposition, Marcel Dekker Inc., 1996, Appendix 5, which is
hereby incorporated by reference herein in its entirety, are used
to form the semiconductor junction 410.
[0157] Thin-Film Semiconductor Junctions Based on Copper Indium
Diselenide and Other Type Materials.
[0158] Continuing to refer to FIG. 5A, in some embodiments, the
absorber layer 502 is a group I-III-VI.sub.2 compound such as
copper indium di-selenide (CuInSe.sub.2; also known as CIS). In
some embodiments, the absorber layer 502 is a group I-II-VI.sub.2
ternary compound selected from the group consisting of
CdGeAs.sub.2, ZnSnAs.sub.2, CuInTe.sub.2, AgInTe.sub.2,
CuInSe.sub.2, CuGaTe.sub.2, ZnGeAs.sub.2, CdSnP.sub.2,
AgInSe.sub.2, AgGaTe.sub.2, CuInS.sub.2, CdSiAs.sub.2, ZnSnP.sub.2,
CdGeP.sub.2, ZnSnAs.sub.2, CuGaSe.sub.2, AgGaSe.sub.2, AgInS.sub.2,
ZnGeP.sub.2, ZnSiAs.sub.2, ZnSiP.sub.2, CdSiP.sub.2, or CuGaS.sub.2
of either the p-type or the n-type when such compound is known to
exist.
[0159] In some embodiments, the junction partner layer 504 is CdS,
ZnS, ZnSe, or CdZnS. In one embodiment, the absorber layer 502 is
p-type CIS and the junction partner layer 504 is n.sub.- type CdS,
ZnS, ZnSe, or CdZnS. Such semiconductor junctions 410 are described
in Chapter 6 of Bube, Photovoltaic Materials, 1998, Imperial
College Press, London, which is hereby incorporated by reference
herein in its entirety. Such semiconductor junctions 410 are
described in Chapter 6 of Bube, Photovoltaic Materials, 1998,
Imperial College Press, London, which is hereby incorporated by
reference herein in its entirety.
[0160] In some embodiments, the absorber layer 502 is
copper-indium-gallium-diselenide (CIGS). Such a layer is also known
as Cu(InGa)Se.sub.2. In some embodiments, the absorber layer 502 is
copper-indium-gallium-diselenide (CIGS) and the junction partner
layer 504 is CdS, ZnS, ZnSe, or CdZnS. In some embodiments, the
absorber layer 502 is p-type CIGS and the junction partner layer
504 is n-type CdS, ZnS, ZnSe, or CdZnS. Such semiconductor
junctions 410 are described in Chapter 13 of Handbook of
Photovoltaic Science and Engineering, 2003, Luque and Hegedus
(eds.), Wiley & Sons, West Sussex, England, Chapter 12, which
is hereby incorporated by reference herein in its entirety. In some
embodiments, CIGS is deposited using techniques disclosed in Beck
and Britt, Final Technical Report, January 2006, NREL/SR-520-39119;
and Delahoy and Chen, August 2005, "Advanced CIGS Photovoltaic
Technology," subcontract report; Kapur et al., January 2005
subcontract report, NREL/SR-520-37284, "Lab to Large Scale
Transition for Non-Vacuum Thin Film CIGS Solar Cells"; Simpson et
al., October 2005 subcontract report, "Trajectory-Oriented and
Fault-Tolerant-Based Intelligent Process Control for Flexible CIGS
PV Module Manufacturing," NREL/SR-520-38681; and Ramanathan et al.,
31.sup.st IEEE Photovoltaics Specialists Conference and Exhibition,
Lake Buena Vista, Fla., Jan. 3-7, 2005, each of which is hereby
incorporated by reference herein in its entirety.
[0161] In some embodiments the absorber layer 502 is CIGS grown on
a molybdenum back-electrode 104 by evaporation from elemental
sources in accordance with a three stage process described in
Ramanthan et al., 2003, "Properties of 19.2% Efficiency
ZnO/CdS/CuInGaSe.sub.2 Thin-film Solar Cells," Progress in
Photovoltaics: Research and Applications 11, 225, which is hereby
incorporated by reference herein in its entirety. In some
embodiments the layer 504 is a ZnS(O,OH) buffer layer as described,
for example, in Ramanathan et al., Conference Paper, "CIGS
Thin-Film Solar Research at NREL: FY04 Results and
Accomplishments," NREL/CP-520-37020, January 2005, which is hereby
incorporated by reference herein in its entirety.
[0162] In some embodiments, the layer 502 is between 0.5 .mu.m and
2.0 .mu.m thick. In some embodiments, the composition ratio of
Cu/(In +Ga) in the layer 502 is between 0.7 and 0.95. In some
embodiments, the composition ratio of Ga/(In +Ga) in the layer 502
is between 0.2 and 0.4. In some embodiments the CIGS absorber has a
<110> crystallographic orientation. In some embodiments the
CIGS absorber has a <112> crystallographic orientation. In
some embodiments the CIGS absorber is randomly oriented.
[0163] Semiconductor Junctions Based on Gallium Arsenide and Other
Type III-V Materials.
[0164] In some embodiments, the semiconductor junctions 410 are
based upon gallium arsenide (GaAs) or other III-V materials such as
InP, AlSb, and CdTe. GaAs is a direct-band gap material having a
band gap of 1.43 eV and can absorb 97% of AM1 radiation in a
thickness of about two microns. Suitable type III-V junctions that
can serve as semiconductor junctions 410 of the present application
are described in Chapter 4 of Bube, Photovoltaic Materials, 1998,
Imperial College Press, London, which is hereby incorporated by
reference in its entirety.
[0165] Furthermore, in some embodiments, the semiconductor junction
410 is a hybrid multijunction solar cell such as a GaAs/Si
mechanically stacked multijunction as described by Gee and Virshup,
1988, 20.sup.th IEEE Photovoltaic Specialist Conference, IEEE
Publishing, New York, p. 754, which is hereby incorporated by
reference herein in its entirety, a GaAs/CuInSe.sub.2 MSMJ
four-terminal device, consisting of a GaAs thin film top cell and a
ZnCdS/CuInSe.sub.2 thin bottom cell described by Stanbery et al.,
19.sup.th IEEE Photovoltaic Specialist Conference, IEEE Publishing,
New York, p. 280, and Kim et al., 20.sup.th IEEE Photovoltaic
Specialist Conference, IEEE Publishing, New York, p. 1487, each of
which is hereby incorporated by reference herein in its entirety.
Other hybrid multijunction solar cells are described in Bube,
Photovoltaic Materials, 1998, Imperial College Press, London, pp.
131-132, which is hereby incorporated by reference herein in its
entirety.
[0166] Semiconductor Junctions Based on Cadmium Telluride and Other
Type II-VI Materials.
[0167] In some embodiments, the semiconductor junctions 410 are
based upon II-VI compounds that can be prepared in either the
n-type or the p-type form. Accordingly, in some embodiments,
referring to FIG. 5B, the semiconductor junction 410 is a p-n
heterojunction in which the layers 520 and 540 are any combination
set forth in the following table or alloys thereof.
TABLE-US-00001 Layer 520 Layer 540 n-CdSe p-CdTe n-ZnCdS p-CdTe
n-ZnSSe p-CdTe p-ZnTe n-CdSe n-CdS p-CdTc n-CdS p-ZnTe p-ZnTe
n-CdTe n-ZnSe p-CdTe n-ZnSe p-ZnTe n-ZnS p-CdTe n-ZnS p-ZnTe
[0168] Methods for manufacturing semiconductor junctions 410 based
upon II-VI compounds are described in Chapter 4 of Bube,
Photovoltaic Materials, 1998, Imperial College Press, London, which
is hereby incorporated by reference herein in its entirety.
Additional Optional Layers and Components
[0169] As noted above, the nonplanar photovoltaic module 402 can
include layers other than those illustrated in FIGS. 2A-2F.
[0170] Optional Water Resistant Layer.
[0171] In some embodiments, one or more layers of water resistant
material are coated over the photovoltaic module to waterproof the
photovoltaic module. In some embodiments, this water resistant
layer is coated onto the transparent conductor 110, the optional
filler layer 330, the optional transparent casing 310, and/or an
optional antireflective coating described below. For example, in
some embodiments, such water resistant layers are circumferentially
disposed onto the optional filler layer 330 prior to encasing the
photovoltaic module 402 in optional transparent casing 310. In some
embodiments, such water resistant layers are circumferentially
disposed onto transparent casing 310 itself. In embodiments where a
water resistant layer is provided to waterproof the photovoltaic
module, the optical properties of the water resistant layer are
chosen so that they do not interfere with the absorption of
incident light by the photovoltaic module. In some embodiments, the
water resistant layer is made of clear silicone, SiN,
SiO.sub.xN.sub.y, SiO.sub.x, or Al.sub.2O.sub.3, where x and y are
integers. In some embodiments, the water resistant layer is made of
a Q-type silicone, a silsequioxane, a D-type silicone, or an M-type
silicone.
[0172] Optional Antireflective Coating.
[0173] In some embodiments, an optional antireflective coating is
also disposed onto the transparent conductor 110, the optional
filler layer 330, the optional transparent casing 310, and/or the
optional water resistant layer described above in order to maximize
solar cell efficiency. In some embodiments, there is a both a water
resistant layer and an antireflective coating deposited on the
transparent conductor 110, the optional filler layer 330, and/or
the optional transparent casing 310.
[0174] In some embodiments, a single layer serves the dual purpose
of a water resistant layer and an anti-reflective coating. In some
embodiments, the antireflective coating is made of MgF.sub.2,
silicone nitride, titanium nitride, silicon monoxide (SiO), or
silicon oxide nitride. In some embodiments, there is more than one
layer of antireflective coating. In some embodiments, there is more
than one layer of antireflective coating and each layer is made of
the same material. In some embodiments, there is more than one
layer of antireflective coating and each layer is made of a
different material.
[0175] Optional Fluorescent Material.
[0176] In some embodiments, a fluorescent material (e.g.,
luminescent material, phosphorescent material) is coated on a
surface of a layer of the photovoltaic module. In some embodiments,
the fluorescent material is coated on the luminal surface and/or
the exterior surface of the transparent conductor 110, the optional
filler layer 330, and/or the optional transparent casing 310. In
some embodiments, the photovoltaic module includes a water
resistant layer and the fluorescent material is coated on the water
resistant layer. In some embodiments, more than one surface of a
photovoltaic module is coated with optional fluorescent material.
In some embodiments, the fluorescent material absorbs blue and/or
ultraviolet light, which some semiconductor junctions of the
present application do not use to convert to electricity, and the
fluorescent material emits light in visible and/or infrared light
which is useful for electrical generation in some solar cells 300
of the present application.
[0177] Fluorescent, luminescent, or phosphorescent materials can
absorb light in the blue or UV range and emit visible light.
Phosphorescent materials, or phosphors, usually include a suitable
host material and an activator material. The host materials are
typically oxides, sulfides, selenides, halides or silicates of
zinc, cadmium, manganese, aluminum, silicon, or various rare earth
metals. The activators are added to prolong the emission time.
[0178] In some embodiments of the application, phosphorescent
materials are incorporated in the systems and methods of the
present application to enhance light absorption by the solar cells
of the nonplanar photovoltaic module 402. In some embodiments, the
phosphorescent material is directly added to the material used to
make the optional transparent casing 310. In some embodiments, the
phosphorescent materials are mixed with a binder for use as
transparent paints to coat various outer or inner layers of the
solar cells 12 of the photovoltaic module 402, as described
above.
[0179] Exemplary phosphors include, but are not limited to,
copper-activated zinc sulfide (ZnS:Cu) and silver-activated zinc
sulfide (ZnS:Ag). Other exemplary phosphorescent materials include,
but are not limited to, zinc sulfide and cadmium sulfide (ZnS:CdS),
strontium aluminate activated by europium (SrAlO.sub.3:Eu),
strontium titanium activated by praseodymium and aluminum
(SrTiO3:Pr, Al), calcium sulfide with strontium sulfide with
bismuth ((Ca,Sr)S:Bi), copper and magnesium activated zinc sulfide
(ZnS:Cu,Mg), or any combination thereof.
[0180] Methods for creating phosphor materials are known in the
art. For example, methods of making ZnS:Cu or other related
phosphorescent materials are described in U.S. Pat. Nos. 2,807,587
to Butler et al.; 3,031,415 to Morrison et al.; 3,031,416 to
Morrison et al.; 3,152,995 to Strock; 3,154,712 to Payne; 3,222,214
to Lagos et al.; 3,657,142 to Poss; 4,859,361 to Reilly et al., and
5,269,966 to Karam et al., each of which is hereby incorporated by
reference herein in its entirety. Methods for making ZnS:Ag or
related phosphorescent materials are described in U.S. Pat. Nos.
6,200,497 to Park et al., 6,025,675 to Ihara et al.; 4,804,882 to
Takahara et al., and 4,512,912 to Matsuda et al., each of which is
hereby incorporated by reference herein in its entirety. Generally,
the persistence of the phosphor increases as the wavelength
decreases. In some embodiments, quantum dots of CdSe or similar
phosphorescent material can be used to get the same effects. See
Dabbousi et al., 1995, "Electroluminescence from CdSc
quantum-dot/polymer composites," Applied Physics Letters 66 (11):
1316-1318; Dabbousi et al., 1997 "(CdSe)ZnS Core-Shell Quantum
Dots: Synthesis and Characterization of a Size Series of Highly
Luminescent Nanocrystallites," J. Phys. Chem. B, 101: 9463-9475;
Ebenstein et al., 2002, "Fluorescence quantum yield of CdSe:ZnS
nanocrystals investigated by correlated atomic-force and
single-particle fluorescence microscopy," Applied Physics Letters
80: 1023-1025; and Peng et al., 2000, "Shape control of CdSe
nanocrystals," Nature 404: 59-61; each of which is hereby
incorporated by reference herein in its entirety.
[0181] In some embodiments, optical brighteners are used in the
optional fluorescent layers of the present application. Optical
brighteners (also known as optical brightening agents, fluorescent
brightening agents or fluorescent whitening agents) are dyes that
absorb light in the ultraviolet and violet region of the
electromagnetic spectrum, and re-emit light in the blue region.
Such compounds include stilbenes (e.g., trans-1,2-diphenylethylene
or (E)-1,2-diphenylethene). Another exemplary optical brightener
that can be used in the optional fluorescent layers of the present
application is umbelliferone (7-hydroxycoumarin), which also
absorbs energy in the UV portion of the spectrum. This energy is
then re-emitted in the blue portion of the visible spectrum. More
information on optical brighteners is in Dean, 1963, Naturally
Occurring Oxygen Ring Compounds, Butterworths, London; Joule and
Mills, 2000, Heterocyclic Chemistry, 4.sup.th edition, Blackwell
Science, Oxford, United Kingdom; and Barton, 1999, Comprehensive
Natural Products Chemistry 2: 677, Nakanishi and Meth-Cohn eds.,
Elsevier, Oxford, United Kingdom, 1999, each of which is hereby
incorporated by reference herein in its entirety.
[0182] Layer Construction.
[0183] In some embodiments, some of the afore-mentioned layers are
constructed using cylindrical magnetron sputtering techniques,
conventional sputtering methods, or reactive sputtering methods on
long tubes or strips. Sputtering coating methods for long tubes and
strips are disclosed in for example, Hoshi et al., 1983, "Thin Film
Coating Techniques on Wires and Inner Walls of Small Tubes via
Cylindrical Magnetron Sputtering," Electrical Engineering in Japan
103:73-80; Lincoln and Blickensderfer, 1980, "Adapting Conventional
Sputtering Equipment for Coating Long Tubes and Strips," J. Vac.
Sci. Technol. 17:1252-1253; Harding, 1977, "Improvements in a dc
Reactive Sputtering System for Coating Tubes," J. Vac. Sci.
Technol. 14:1313-1315; Pearce, 1970, "A Thick Film Vacuum
Deposition System for Microwave Tube Component Coating," Conference
Records of 1970 Conference on Electron Device Techniques 208-211;
and Harding et al., 1979, "Production of Properties of Selective
Surfaces Coated onto Glass Tubes by a Magnetron Sputtering System,"
Proceedings of the International Solar Energy Society 1912-1916,
each of which is hereby incorporated by reference herein in its
entirety.
DEFINITIONS
[0184] About. In some embodiments, the term "about" as used in the
present invention means within .+-.5% of the given (nominal) value.
In other embodiments, the term "about" means within .+-.10% of the
given (nominal) value. In yet other embodiments, the term "about"
means within .+-.20% of the given (nominal) value.
[0185] Substantially. In some embodiments, the term "substantially"
as used in the present invention means within .+-.5% of the given
(nominal) value. In other embodiments, the term "substantially"
means within .+-.10% of the given (nominal) value. In yet other
embodiments, the term "substantially" means within .+-.20% of the
given (nominal) value.
[0186] Circumferentially disposed. In some embodiments of the
present application, layers of material are successively
circumferentially disposed on a non-planar elongated substrate in
order to form the solar cells 12 of a photovoltaic module 402 as
well as the encapsulating layers of the photovoltaic module such as
filler layer 330 and the casing 310. As used herein, the term
"circumferentially disposed" is not intended to imply that each
such layer of material is necessarily deposited on an underlying
layer or that the shape of the solar cell 12 and/or photovoltaic
module 402 and/or substrate is cylindrical. In fact, the present
application discloses methods by which such layers are molded or
otherwise formed on an underlying layer. Further, as discussed
above in conjunction with the discussion of the substrate 102, the
substrate and underlying layers may have any of several different
planar or nonplanar shapes. Nevertheless, the term
"circumferentially disposed" means that an overlying layer is
disposed on an underlying layer such that there is no space (e.g.,
no annular space) between the overlying layer and the underlying
layer. Furthermore, as used herein, the term "circumferentially
disposed" means that an overlying layer is disposed on at least
fifty percent of the perimeter of the underlying layer.
Furthermore, as used herein, the term "circumferentially disposed"
means that an overlying layer is disposed along at least half of
the length of the underlying layer. Furthermore, as used herein,
the term "disposed" means that one layer is disposed on an
underlying layer without any space between the two layers. So, if a
first layer is disposed on a second layer, there is no space
between the two layers. Furthermore, as used herein, the term
circumferentially disposed means that an overlying layer is
disposed on at least twenty percent, at least thirty percent, at
least forty, percent, at least fifty percent, at least sixty
percent, at least seventy percent, or at least eighty percent of
the perimeter of the underlying layer. Furthermore, as used herein,
the term circumferentially disposed means that an overlying layer
is disposed along at least half of the length, at least
seventy-five percent of the length, or at least ninety-percent of
the underlying layer.
[0187] Rigid. In some embodiments, the substrate 102 is rigid.
Rigidity of a material can be measured using several different
metrics including, but not limited to, Young's modulus. In solid
mechanics, Young's Modulus (E) (also known as the Young Modulus,
modulus of elasticity, elastic modulus or tensile modulus) is a
measure of the stiffness of a given material. It is defined as the
ratio, for small strains, of the rate of change of stress with
strain. This can be experimentally determined from the slope of a
stress-strain curve created during tensile tests conducted on a
sample of the material. Young's modulus for various materials is
given in the following table.
TABLE-US-00002 Young's modulus Young's modulus (E) in Material (E)
in GPa lbf/in.sup.2 (psi) Rubber (small strain) 0.01-0.1
1,500-15,000 Low density polyethylene 0.2 30,000 Polypropylene
1.5-2 217,000-290,000 Polyethylene terephthalate 2-2.5
290,000-360,000 Polystyrene 3-3.5 435,000-505,000 Nylon 3-7
290,000-580,000 Aluminum alloy 69 10,000,000 Glass (all types) 72
10,400,000 Brass and bronze 103-124 17,000,000 Titanium (Ti)
105-120 15,000,000-17,500,000 Carbon fiber reinforced plastic 150
21,800,000 (unidirectional, along grain) Wrought iron and steel
190-210 30,000,000 Tungsten (W) 400-410 58,000,000-59,500,000
Silicon carbide (SiC) 450 65,000,000 Tungsten carbide (WC) 450-650
65,000,000-94,000,000 Single Carbon nanotube 1,000+ 145,000,000
Diamond (C) 1,050-1,200 150,000,000-175,000,000
[0188] In some embodiments of the present application, a material
(e.g., substrate 102) is deemed to be rigid when it is made of a
material that has a Young's modulus of 20 GPa or greater, 30 GPa or
greater, 40 GPa or greater, 50 GPa or greater, 60 GPa or greater,
or 70 GPa or greater. In some embodiments of the present
application a material (e.g., the substrate 102) is deemed to be
rigid when the Young's modulus for the material is a constant over
a range of strains. Such materials are called linear, and are said
to obey Hooke's law. Thus, in some embodiments, the substrate 102
is made out of a linear material that obeys Hooke's law. Examples
of linear materials include, but are not limited to, steel, carbon
fiber, and glass. Rubber and soil (except at very low strains) are
non-linear materials. In some embodiments, a material is considered
rigid when it adheres to the small deformation theory of
elasticity, when subjected to any amount of force in a large range
of forces (e.g., between 1 dyne and 10.sup.5 dynes, between 1000
dynes and 10.sup.6 dynes, between 10,000 dynes and 10.sup.7 dynes),
such that the material only undergoes small elongations or
shortenings or other deformations when subject to such force. The
requirement that the deformations (or gradients of deformations) of
such exemplary materials are small means, mathematically, that the
square of either of these quantities is negligibly small when
compared to the first power of the quantities when exposed to such
a force. Another way of stating the requirement for a rigid
material is that such a material, over a large range of forces
(e.g., between 1 dyne and 10.sup.5 dynes, between 1000 dynes and
10.sup.6 dynes, between 10,000 dynes and 10.sup.7 dynes), is well
characterized by a strain tensor that only has linear terms. The
strain tensor for materials is described in Borg, 1962,
Fundamentals of Engineering Elasticity, Princeton, N.J., pp. 36-41,
which is hereby incorporated by reference herein in its entirety.
In some embodiments, a material is considered rigid when a sample
of the material of sufficient size and dimensions does not
substantially bend under a force of 9.8 m/sec.sup.2.
[0189] Non-planar. The present application is not limited to solar
cells and substrates that have rigid cylindrical shapes or are
solid rods. In some embodiments, all or a portion of the substrate
102 can be characterized by a cross-section bounded by any one of a
number of shapes other than the circular shape depicted in FIG. 2B.
The bounding shape can be any one of circular, ovoid, or any shape
characterized by one or more smooth curved surfaces, or any splice
of smooth curved surfaces. The bounding shape can be an n-gon,
where n is 3, 4, 5, or greater than 5. The bounding shape can also
be linear in nature, including triangular, rectangular,
pentangular, hexagonal, or having any number of linear segmented
surfaces. Or, the cross-section can be bounded by any combination
of linear surfaces, arcuate surfaces, or curved surfaces. As
described herein, for ease of discussion only, an omni-facial
circular cross-section is illustrated to represent non-planar
embodiments of the photovoltaic module. However, it should be noted
that any cross-sectional geometry may be used in a photovoltaic
module that is non-planar in practice.
[0190] In some embodiments, the elongated substrate 102 has a solid
core, as illustrated in FIGS. 2A-2F, while in other embodiments,
the elongated substrate 102 has a hollow core. In some embodiments,
the shape of the elongated substrate 102 is only approximately that
of a cylindrical object, meaning that a cross-section taken at a
right angle to the length of the elongated substrate 102 defines an
ellipse rather than a circle. As the term is used herein, such
approximately shaped objects are still considered cylindrically
shaped in the present application. In some embodiments, the
elongated substrate 102 is flat planar while in other embodiments
the elongated substrate 102 is nonplanar.
[0191] In some embodiments, a first portion of the substrate 102 is
characterized by a first cross-sectional shape and a second portion
of the substrate 102 is characterized by a second cross-sectional
shape, where the first and second cross-sectional shapes are the
same or different. In some embodiments, at least zero percent, at
least ten percent, at least twenty percent, at least thirty
percent, at least forty percent, at least fifty percent, at least
sixty percent, at least seventy percent, at least eighty percent,
at least ninety percent, or all of the length of the substrate 102
is characterized by the first cross-sectional shape, and some or
all of the remainder of the length of the substrate is
characterized by the second cross-sectional shape. In some
embodiments, the first cross-section shape is planar (e.g., has no
arcuate side), and the second cross-sectional shape has at least
one arcuate side.
Exemplary Embodiments
[0192] Under one aspect, a method of patterning a photovoltaic
module comprising a nonplanar back-electrode layer around a
nonplanar substrate includes: (a) scribing the nonplanar
back-electrode layer thereby forming a continuous first groove in
the back-electrode that traverses a perimeter of the back-electrode
a plurality of times; (b) disposing a semiconductor junction around
the back-electrode layer after the scribing step (a); (c) scribing
the semiconductor junction thereby forming a continuous second
groove in the semiconductor junction that traverses a perimeter of
the semiconductor junction a plurality of times; (d) disposing a
transparent conductor layer around the semiconductor junction after
the scribing step (c); (e) scribing the transparent conductor layer
thereby forming a continuous third groove in the transparent
conductor layer that traverses a perimeter of the transparent
conductor layer a plurality of times; and (f) scribing the
back-electrode layer, the semiconductor junction, and the
transparent conductor layer along a length of the photovoltaic
module thereby forming a fourth groove, wherein the fourth groove
and at least one of the first groove, the second groove, and the
third groove define a plurality of solar cells, wherein each solar
cell in the plurality of solar cells comprises a portion of the
back electrode layer bounded by the first groove and the fourth
groove, a portion of the semiconductor junction bounded by the
second groove and the fourth groove, and a portion of the
transparent conductor layer bounded by the third groove and the
fourth groove.
[0193] In some embodiments, at least one of the first, second, and
third grooves has a repeating pattern, a non-repeating pattern, or
is helical. In some embodiments, at least one of (a), (c), and (e)
is performed with one of a mechanical scriber and a laser scriber.
In some embodiments, the mechanical scriber is a constant force
mechanical scriber. In some embodiments, at least one of (a), (c),
and (e) comprises circumferentially rotating the substrate. In some
embodiments, at least one of (a), (c), and (e) comprises moving a
scribing mechanism around the photovoltaic module. In some
embodiments, (f) comprises longitudinally translating the
substrate. In some embodiments, (f) comprises longitudinally
translating a scribing mechanism.
[0194] In some embodiments, the first groove is a single groove in
the back-electrode layer; the second groove is a single groove in
the semiconductor junction; and the third groove is a single groove
in the transparent conductor layer. In some embodiments, (f)
comprises linearly scribing the back-electrode layer, the
semiconductor junction, and the transparent conductor layer along
the length of the photovoltaic module. In some embodiments, the
disposing step (b) comprises disposing an absorber layer on the
scribed back-electrode layer; and disposing a junction partner
layer on the absorber layer.
[0195] In some embodiments, at least one of the first groove, the
second groove, and the third groove is helical and is defined by:
[0196] x=r cos t [0197] y=r sin t [0198] z=ct
[0199] wherein
t.di-elect cons.[2,2.pi.),
where r is radius of a helix defined by the first groove, the
second groove, or the third groove, and 2.pi.c is a constant giving
a vertical separation of each loop in the helix defined by the at
least one of the first groove, the second groove, and the third
groove. In some embodiments, 1 r is between 10 mm and 10,000 mm,
and c is between 0.4 mm and 100 mm. In some embodiments, at least
one of the first groove, the second groove, and the third groove is
a space curve, wherein the space curve is formed by wrapping a two
dimensional curve having a repeating pattern about the photovoltaic
module.
[0200] In some embodiments, a first solar cell in the plurality of
solar cells is electrically connected in series to a second solar
cell in the plurality of solar cells. In some embodiments, a first
solar cell in the plurality of solar cells is electrically
connected in parallel to a second solar cell in the plurality of
solar cells.
[0201] In some embodiments, the photovoltaic module is cylindrical.
In some embodiments, the photovoltaic module is characterized by a
cross-section that is circular, ovoid, or an n-gon, wherein n is 3,
4, 5, or greater than 5. In some embodiments, the photovoltaic
module is characterized by a cross-section that comprises an
arcuate portion. In some embodiments, the photovoltaic module is
characterized by a first cross-section and a second cross-section,
wherein the first cross-section is bounded by a shape that is
different than a shape that bounds the second cross-section.
[0202] Under another aspect, a nonplanar photovoltaic module having
a length includes: (a) an elongated nonplanar substrate; and (b) a
plurality of solar cells disposed on the elongated nonplanar
substrate, wherein each solar cell in the plurality of solar cells
is defined by (i) a plurality of grooves around the nonplanar
photovoltaic module and (ii) a groove along the length of the
photovoltaic module.
[0203] In some embodiments, each groove of the plurality of grooves
about the photovoltaic module, independently, has a repeating
pattern, a non-repeating pattern, or is helical. In some
embodiments, the module further includes a patterned conductor
providing serial electrical communication between adjacent solar
cells. In some embodiments, portions of the patterned conductor
providing serial electrical communication between adjacent solar
cells are within a groove of the plurality of grooves about the
photovoltaic module. In some embodiments, each solar cell of the
plurality of solar cells comprises a back-electrode layer disposed
on the substrate, wherein portions of the back-electrode layer are
defined by a first groove of the plurality of grooves about the
photovoltaic module and the groove along the length of the
photovoltaic module. In some embodiments, each solar cell of the
plurality of solar cells further comprises a semiconductor junction
disposed on the back-electrode layer, wherein portions of the
semiconductor junction are defined by a second groove of the
plurality of grooves about the photovoltaic module and the groove
along the length of the photovoltaic module. In some embodiments,
each solar cell of the plurality of solar cells further comprises a
transparent conductor layer disposed on the semiconductor junction,
wherein portions of the transparent conductor layer defined by a
third groove of the plurality of grooves about the photovoltaic
module and the groove along the length of the photovoltaic module.
In some embodiments, each solar cell comprises a portion of the
back-electrode layer, a portion of the semiconductor junction at
least partially overlying the portion of the back-electrode layer,
and a portion of the transparent conductor layer at least partially
overlying the portion of the semiconductor junction. In some
embodiments, portions of the transparent conductor layer are in the
second groove and provide electrical communication between the
portion of the back-electrode layer of a first solar cell of the
plurality of solar cells and the portion of the transparent
conductor layer of a second solar cell of the plurality of solar
cells, wherein the first solar cell is adjacent to the second solar
cell. In some embodiments, the first, second, and third grooves are
laterally offset from each other.
[0204] In some embodiments, the module further includes a
substantially transparent casing circumferentially disposed on the
plurality of solar cells. In some embodiments, the groove along the
length of the photovoltaic module is linear. In some embodiments,
the plurality of solar cells comprises at least ten solar
cells.
[0205] Under another aspect, a photovoltaic module comprising a
nonplanar back-electrode around a nonplanar substrate is formed by:
(a) scribing the non-planar back-electrode layer thereby forming a
continuous first groove in the back-electrode that traverses a
perimeter of the back-electrode a plurality of time; (b) disposing
a semiconductor junction around the back-electrode layer after the
scribing step (a); (c) scribing the semiconductor junction thereby
forming a continuous second groove in the semiconductor junction
that traverses a perimeter of the semiconductor junction a
plurality of times; (d) disposing a transparent conductor layer on
the semiconductor junction after the scribing step (c); (e)
scribing the transparent conductor layer thereby forming a
continuous third groove in the transparent conductor layer that
traverses a perimeter of the transparent conductor layer a
plurality of times; and (f) scribing the back-electrode layer, the
semiconductor junction, and the transparent conductor layer a
length of the photovoltaic module thereby forming a fourth groove,
wherein the fourth groove and at least one of the first groove, the
second groove, and the third groove define a plurality of solar
cells, wherein each solar cell in the plurality of solar cells
comprises a portion of the back-electrode layer bounded by the
first groove and the fourth groove, a portion of the semiconductor
junction bounded by the second groove and the fourth groove, and a
portion of the transparent conductor layer bounded by the third
groove and the fourth groove.
[0206] In some embodiments, at least one of the first, second, and
third grooves has a repeating pattern, a non-repeating pattern, or
is helical. In some embodiments, at least one of (a), (c), and (e)
is performed with one of a mechanical scriber and a laser scriber.
In some embodiments, the mechanical scriber comprises a constant
force mechanical scriber. In some embodiments, at least one of (a),
(c), and (e) comprises circumferentially rotating the substrate. In
some embodiments, at least one of (a), (c), and (e) comprises
moving a scribing mechanism around the photovoltaic module. In some
embodiments, (f) comprises longitudinally translating the
substrate. In some embodiments, (f) comprises longitudinally
translating a scribing mechanism.
[0207] In some embodiments, the first groove is a single groove in
the back-electrode layer; the second groove is a single groove in
the semiconductor junction; and the third groove is a single groove
in the transparent conductor layer. In some embodiments, the single
groove in at least one of the back-electrode layer, semiconductor
junction, and transparent conductor layer has a width of between
about 10 microns and about 300 microns. In some embodiments, the
single groove in at least one of the back-electrode layer,
semiconductor junction, and transparent conductor layer has a width
of between about 50 microns and about 150 microns. In some
embodiments, the fourth groove is linear. In some embodiments, the
disposing step (b) comprises: disposing an absorber layer on the
back-electrode layer; and disposing a junction partner layer on the
absorber layer.
[0208] In some embodiments, at least one of the first groove, the
second groove, and the third groove is helical and is defined by:
[0209] x=r cos t [0210] y=r sin t [0211] z=ct
[0212] wherein
t.di-elect cons.[2,2.pi.),
where r is radius of a helix defined by the first groove, the
second groove, or the third groove, and 2.pi.c is a constant giving
a vertical separation of each loop in the helix defined by the at
least one of the first groove, the second groove, and the third
groove. In some embodiments, r is between 10 mm and 10,000 mm, and
c is between 0.4 mm and 100 mm. In some embodiments, at least one
of the first groove, the second groove, and the third groove is a
space curve, wherein the space curve is formed by wrapping a two
dimensional curve having a repeating pattern about the photovoltaic
module.
[0213] In some embodiments, the plurality of solar cells comprises
at least ten solar cells. In some embodiments, the plurality of
solar cells comprises at least fifty solar cells.
[0214] Under another aspect, a method of creating a non-unifacial
photovoltaic module around an elongated substrate includes: (a)
disposing a first material on the elongated substrate to form a
back electrode; (b) disposing one or more photovoltaic materials on
the back electrode to form a photovoltaic layer; (c) disposing a
second material on the photovoltaic layer to form a front
electrode; (d) patterning any of the back electrode, the
photovoltaic layer, and the front electrode layer to form a cell
boundary. The patterning includes: traversing a first path in the
any of the back electrode, the photovoltaic layer, and the front
electrode layer in (i) a first orientation directed along a width
of the elongated substrate, and (ii) a second orientation directed
along a length of the elongated substrate, the traversing in (i)
the first orientation occurring substantially concurrently with the
traversing in (ii) the second orientation so that the first path
includes a component in the first orientation and a component in
the second orientation.
[0215] In some embodiments, the first path traverses a perimeter of
the any of the back electrode, the photovoltaic layer, and the
front electrode layer a plurality of times.
[0216] Under another aspect, a photovoltaic module having a length
dimension and a width dimension includes an elongated substrate; a
plurality of photovoltaic components comprising: a first material
disposed on the elongated substrate to form a back electrode; one
or more photovoltaic materials disposed on the back electrode to
form a photovoltaic layer; and a second material disposed on the
photovoltaic layer to form a front electrode. The module also
includes one or more solar cells formed from the plurality of
photovoltaic components such that the one or more solar cells are
operable to generate electricity from light impinging the one or
more solar cells from a range of directions spanning more than 180
degrees about the length dimension or the width dimension of the
photovoltaic module. The module also includes an electrical
boundary within at least one photovoltaic component in the
plurality of photovoltaic components, the electrical boundary being
formed by patterning any of the first material, the photovoltaic
layer, and the second material, the patterning comprising forming a
filled or unfilled via following a path comprising a first
component and a second component, wherein: the first component is a
first orientation directed along a width of the elongated
substrate, and the second component is a second orientation
directed along a length of the elongated substrate. The forming
advances substantially concurrently (i) in the first orientation at
a first rate and (ii) in the second orientation at a second
rate.
[0217] In some embodiments, at least one of the first and second
rates is variable. In some embodiments, In some embodiments, the
first rate is different from the second rate. In some embodiments,
the electrical boundary is an isolation boundary. In some
embodiments, the electrical boundary defines a serial electrical
connection between solar cells that share the electrical boundary.
In some embodiments, the electrical boundary defines a parallel
electrical connection between solar cells that share the electrical
boundary. In some embodiments, the first path traverses a perimeter
of the any of the back electrode, the photovoltaic junction, and
the front electrode a plurality of times.
[0218] Under another aspect, a method of patterning a conductive
layer disposed around a nonplanar substrate includes scribing the
conductive layer thereby forming a continuous groove that traverses
a perimeter of the conductive layer a plurality of times.
[0219] In some embodiments, the conductive layer comprises at least
one of a metal, a semiconductor, a conductive polymer, and an
insulator. In some embodiments, the nonplanar substrate comprises
at least one of metal, a semiconductor, a conductive polymer, and
an insulator. In some embodiments, the nonplanar substrate is
unifacial. In some embodiments, the unifacial nonplanar substrate
is cylindrical. In some embodiments, the nonplanar substrate is
multifacial. In some embodiments, the nonplanar substrate is
bifacial. In some embodiments, the nonplanar substrate has a width
and a length that is at least three times larger than the width. In
some embodiments, the length is at least ten times larger than the
width. In some embodiments, the conductive layer has a thickness,
and scribing the conductive layer comprises forming a continuous
groove through the thickness of the conductive layer. In some
embodiments, the groove has a repeating pattern, a non-repeating
pattern, or is helical. In some embodiments, scribing the
conductive layer is performed with one of a mechanical scriber and
a laser scriber. In some embodiments, the mechanical scriber is a
constant force mechanical scriber. In some embodiments, scribing
the conductive layer comprises rotating the substrate about a long
axis of the substrate. In some embodiments, scribing the conductive
layer comprises moving a scribing mechanism around the substrate.
In some embodiments, scribing the conductive layer thereby forming
a continuous groove that extends along a length of the substrate.
In some embodiments, forming the continuous groove that extends
along the length of the substrate comprises longitudinally
translating the substrate. In some embodiments, forming the
continuous groove that extends along the length of the substrate
comprises longitudinally translating a scribing mechanism. In some
embodiments, the continuous groove that extends along the length of
the substrate is linear, has a repeating pattern, or has a
non-repeating pattern. Some embodiments further includes forming a
conductive layer overlying the scribed conductor layer.
[0220] Under another aspect, a patterned conductive layer is
disposed around a nonplanar substrate, wherein a boundary of the
conductive layer is defined by a single groove that traverses a
perimeter of the substrate a plurality of times.
[0221] Under another aspect, a patterned conductive layer is
disposed around a nonplanar substrate, wherein the patterned
conductive layer is divided into a plurality of conductive islands
by a groove that extends through a thickness of the conductive
layer and traverses a perimeter of the substrate a plurality of
times, and a groove extends through the thickness of the conductive
layer and traverses a length of the substrate.
RELATED APPLICATIONS
[0222] This application is related to the following applications,
the entire contents of each of which are incorporated by reference
herein: U.S. Pat. No. 7,235,736, filed on Mar. 18, 2006 and
entitled "Monolithic Integration of Cylindrical Solar Cells;" U.S.
Provisional Patent Application No. 60/976,401, filed on Sep. 28,
2007 and entitled "Scribing Methods for Photovoltaic Modules
Including a Mechanical Scribe;" U.S. Provisional Patent Application
No. 60/980,372, filed on Oct. 16, 2007 and entitled "Constant Force
Mechanical Scribers and Methods for Using Same In Semiconductor
Processing Applications;" and U.S. Provisional Patent Application
No. 61/082,148, filed on Jul. 18, 2008 and entitled "Elongated
Semiconductor Devices, Methods of Making Same, and Systems for
Making Same."
INCORPORATION BY REFERENCE
[0223] All references cited herein are incorporated herein by
reference in their entirety and for all purposes to the same extent
as if each individual publication or patent or patent application
was specifically and individually indicated to be incorporated by
reference in its entirety for all purposes.
[0224] Many modifications and variations of this application can be
made without departing from its spirit and scope, as will be
apparent to those skill in the art. The specific embodiments
described herein are offered by way of example only, and the
application is to be limited only by the terms of the appended
claims, along with the full scope of equivalents to which the
claims are entitled.
* * * * *