U.S. patent application number 10/723554 was filed with the patent office on 2004-09-30 for photovoltaic cell with mesh electrode.
Invention is credited to Gaudiana, Russell, Montello, Alan.
Application Number | 20040187911 10/723554 |
Document ID | / |
Family ID | 32988660 |
Filed Date | 2004-09-30 |
United States Patent
Application |
20040187911 |
Kind Code |
A1 |
Gaudiana, Russell ; et
al. |
September 30, 2004 |
Photovoltaic cell with mesh electrode
Abstract
Photovoltaic cells that have a mesh electrode, as well as
related systems, methods and components, are disclosed.
Inventors: |
Gaudiana, Russell;
(Merrimack, NH) ; Montello, Alan; (West Newbury,
MA) |
Correspondence
Address: |
FISH & RICHARDSON PC
225 FRANKLIN ST
BOSTON
MA
02110
US
|
Family ID: |
32988660 |
Appl. No.: |
10/723554 |
Filed: |
November 26, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10723554 |
Nov 26, 2003 |
|
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10395823 |
Mar 24, 2003 |
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Current U.S.
Class: |
136/252 ;
136/243; 136/256 |
Current CPC
Class: |
Y02E 10/549 20130101;
H01G 9/2013 20130101; H01L 27/301 20130101; H01G 9/2059 20130101;
Y02E 10/542 20130101; H01L 51/4253 20130101; H01G 9/2081 20130101;
Y02P 70/50 20151101; H01G 9/2031 20130101; H01L 51/441 20130101;
H01G 9/2068 20130101; H01L 51/445 20130101 |
Class at
Publication: |
136/252 ;
136/243; 136/256 |
International
Class: |
H01L 031/00 |
Claims
What is claimed is:
1. A photovoltaic cell, comprising: a first electrode; a mesh
electrode; and an active layer between the first and mesh
electrodes, the active layer comprising: an electron acceptor
material; and an electron donor material.
2. The photovoltaic cell of claim 1, wherein the mesh electrode is
a cathode.
3. The photovoltaic cell of claim 1, wherein the mesh electrode is
an anode.
4. The photovoltaic cell of claim 1, wherein the mesh comprises an
electrically conductive material.
5. The photovoltaic cell of claim 4, wherein the electrically
conductive material is selected from the group consisting of
metals, alloys, polymers and combinations thereof.
6. The photovoltaic cell of claim 1, wherein the mesh electrode
comprises wires.
7. The photovoltaic cell of claim 6, wherein the wires comprise an
electrically conductive material.
8. The photovoltaic cell of claim 7, wherein the electrically
conductive material is selected from the group consisting of
metals, alloys, polymers and combinations thereof.
9. The photovoltaic cell of claim 6, wherein the wires comprise a
coating including an electrically conductive material.
10. The photovoltaic cell of claim 9, wherein the electrically
conductive material is selected from the group consisting of
metals, alloys, polymers and combinations thereof.
11. The photovoltaic cell of claim 1, wherein the mesh electrode
comprises an expanded mesh.
12. The photovoltaic cell of claim 1, wherein the mesh electrode
comprises a woven mesh.
13. The photovoltaic cell of claim 1, wherein the electron acceptor
material comprises a material selected from the group consisting of
fullerenes, inorganic nanoparticles, oxadiazoles, discotic liquid
crystals, carbon nanorods, inorganic nanorods, polymers containing
CN groups, polymers containing CF.sub.3 groups and combinations
thereof.
14. The photovoltaic cell of claim 1, wherein the electron acceptor
material comprises a substituted fullerene.
15. The photovoltaic cell of claim 1, wherein the electron donor
material comprises a material selected from the group consisting of
discotic liquid crystals, polythiophenes, polyphenylenes,
polyphenylvinylenes, polysilanes, polythienylvinylenes and
polyisothianaphthalenes.
16. The photovoltaic cell of claim 1, wherein the electron donor
material comprises poly(3-hexylthiophene).
17. The photovoltaic cell of claim 1, further comprising a hole
blocking layer between the active layer and the first
electrode.
18. The photovoltaic cell of claim 17, wherein the hole blocking
layer comprises a material selected from the group consisting of
LiF, metal oxides and combinations thereof.
19. The photovoltaic cell of claim 1, further comprising a hole
blocking layer between the active layer and the mesh electrode.
20. The photovoltaic cell of claim 19, wherein the hole blocking
layer comprises a material selected from the group consisting of
LiF, metal oxides and combinations thereof.
21. The photovoltaic cell of claim 1, further comprising a hole
carrier layer between the active layer and the mesh electrode.
22. The photovoltaic cell of claim 21, wherein the hole carrier
layer comprises a material selected from the group consisting of
polythiophenes, polyanilines, polyvinylcarbazoles, polyphenylenes,
polyphenylvinylenes, polysilanes, polythienylenevinylenes,
polyisothianaphthanenes and combinations thereof.
23. The photovoltaic cell of claim 1, further comprising a hole
carrier layer between the active layer and the first electrode.
24. The photovoltaic cell of claim 23, wherein the hole carrier
layer comprises a material selected from the group consisting of
polythiophenes, polyanilines, polyvinylcarbazoles, polyphenylenes,
polyphenylvinylenes, polysilanes, polythienylenevinylenes,
polyisothianaphthanenes and combinations thereof.
25. The photovoltaic cell of claim 1, wherein the first electrode
comprises a mesh electrode.
26. A photovoltaic cell, comprising: a first electrode; a mesh
electrode; an active layer between the first and mesh electrodes,
the active layer comprising: an electron acceptor material; and an
electron donor material; a hole blocking layer between the first
electrode and the active layer; and a hole carrier layer between
the mesh electrode and the active layer.
27. The photovoltaic cell of claim 26, wherein the mesh comprises
an electrically conductive material.
28. The photovoltaic cell of claim 27, wherein the electrically
conductive material is selected from the group consisting of
metals, alloys, polymers and combinations thereof.
29. The photovoltaic cell of claim 26, wherein the hole carrier
layer comprises a material selected from the group consisting of
polythiophenes, polyanilines, polyvinylcarbazoles, polyphenylenes,
polyphenylvinylenes, polysilanes, polythienylenevinylenes,
polyisothianaphthanenes and combinations thereof.
30. The photovoltaic cell of claim 29, wherein the hole blocking
layer comprises a material selected from the group consisting of
LiF, metal oxides and combinations thereof.
31. The photovoltaic cell of claim 26, wherein the hole blocking
layer comprises a material selected from the group consisting of
LiF, metal oxides and combinations thereof.
32. The photovoltaic cell of claim 26, wherein the mesh electrode
comprises wires.
33. The photovoltaic cell of claim 32, wherein the wires comprise
an electrically conductive material.
34. The photovoltaic cell of claim 33, wherein the electrically
conductive material is selected from the group consisting of
metals, alloys, polymers and combinations thereof.
35. The photovoltaic cell of claim 32, wherein the wires comprise a
coating including an electrically conductive material.
36. The photovoltaic cell of claim 35, wherein the electrically
conductive material is selected from the group consisting of
metals, alloys, polymers and combinations thereof.
37. The photovoltaic cell of claim 26, wherein the mesh electrode
comprises an expanded mesh.
38. The photovoltaic cell of claim 26, wherein the mesh electrode
comprises a woven mesh.
39. The photovoltaic cell of claim 26, wherein the first electrode
comprises a mesh electrode.
40. The photovoltaic cell of claim 26, further comprising a
substrate supporting the mesh electrode.
41. The photovoltaic cell of claim 40, further comprising an
adhesive material between the substrate and the hole carrier
layer.
42. The photovoltaic cell of claim 40, wherein the hole carrier
layer is in contact with the substrate.
43. A photovoltaic system comprising a plurality of photovoltaic
cells of claim 1, at least some of the plurality of photovoltaic
cells being electrically connected.
44. The photovoltaic system of claim 43, wherein all of the
plurality of photovoltaic cells are electrically connected.
45. The photovoltaic system of claim 43, wherein at least some of
the electrically connected photovoltaic cells are electrically
connected in parallel.
46. The photovoltaic system of claim 43, wherein at least some of
the electrically connected photovoltaic cells are electrically
connected in series.
47. The photovoltaic system of claim 43, wherein the photovoltaic
system is wherein at least some of the electrically connected
photovoltaic cells are electrically connected in to a load.
48. A photovoltaic system comprising a plurality of photovoltaic
cells of claim 24, at least some of the plurality of photovoltaic
cells being wherein at least some of the electrically connected
photovoltaic cells are electrically connected.
49. The photovoltaic system of claim 48, wherein all of the
plurality of photovoltaic cells are electrically connected.
50. The photovoltaic system of claim 48, wherein at least some of
the electrically connected photovoltaic cells are electrically
connected in parallel.
51. The photovoltaic system of claim 48, wherein at least some of
the electrically connected photovoltaic cells are electrically
connected in series.
52. The photovoltaic system of claim 48, wherein the photovoltaic
system is wherein at least some of the electrically connected
photovoltaic cells are electrically connected in parallel to a
load.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of, and claims
priority under 35 U.S.C. .sctn.120 to, U.S. patent application Ser.
No. 10/395,823, filed Mar. 24, 2003, and entitled "Photovoltaic
Cells Utilizing Mesh Electrodes," the entire contents of which are
herby incorporated by reference.
TECHNICAL FIELD
[0002] The invention relates to photovoltaic cells that have a mesh
electrode, as well as related systems, methods and components.
BACKGROUND
[0003] Photovoltaic cells are commonly used to transfer energy in
the form of light into energy in the form of electricity. A typical
photovoltaic cell includes a photoactive material disposed between
two electrodes. Generally, light passes through one or both of the
electrodes to interact with the photoactive material. As a result,
the ability of one or both of the electrodes to transmit light
(e.g., light at one or more wavelengths absorbed by a photoactive
material) can limit the overall efficiency of a photovoltaic cell.
In many photovoltaic cells, a film of semiconductive material
(e.g., indium tin oxide) is used to form the electrode(s) through
which light passes because, although the semiconductive material
may have a lower electrical conductivity than electrically
conductive materials, the semiconductive material can transmit more
light than many electrically conductive materials.
[0004] There is an increasing interest in the development of
photovoltaic technology due primarily to a desire to reduce
consumption of and dependency on fossil fuel-based energy sources.
Photovoltaic technology is also viewed by many as being an
environmentally friendly energy technology. However, for
photovoltaic technology to be a commercially feasible energy
technology, the material and manufacturing costs of a photovoltaic
system (a system that uses one or more photovoltaic cells to
convert light to electrical energy) should be recoverable over some
reasonable time frame. But, in some instances the costs (e.g., due
to materials and/or manufacture) associated with practically
designed photovoltaic systems have restricted their availability
and use.
SUMMARY
[0005] The invention relates to photovoltaic cells that have a mesh
electrode, as well as related systems, methods and components. The
mesh electrode is formed of a material that provides good
electrical conductivity (typically an electrically conductive
material, but semiconductive materials may also be used), and the
mesh electrode has an open area that is large enough to transmit
enough light so that the photovoltaic cell is relatively efficient
at transferring the light to electrical energy.
[0006] In one aspect, the invention features a photovoltaic cell
that includes two electrodes and an active layer between the
electrodes. At least one of the electrodes is in the form of a
mesh. The active layer includes an electron acceptor material and
an electron donor material.
[0007] In another aspect, the invention features a system that
includes a plurality of photovoltaic cells, with each of the
photovoltaic cells including two electrodes and an active layer
between the electrodes. At least one of the electrodes is in the
form of a mesh. The active layer includes an electron acceptor
material and an electron donor material. In some embodiments, two
or more of the photovoltaic cells are electrically connected in
parallel. In certain embodiments, two or more of the photovoltaic
cells are electrically connected in series. In certain embodiments,
two or more of the photovoltaic cells are electrically connected in
parallel, and two or more different photovoltaic cells are
electrically connected in series.
[0008] In a further aspect, the invention features a photovoltaic
cell that includes first and second electrodes, an active layer
between the first and second electrodes, a hole blocking layer
between the first electrode and the active layer, and a hole
carrier layer between the mesh electrode and the active layer. At
least one of the electrodes is in the form of a mesh. The active
layer includes an electron acceptor material and an electron donor
material.
[0009] In another aspect, the invention features a system that
includes a plurality of photovoltaic cells, with each of the
photovoltaic cells including first and second electrodes, an active
layer between the first and second electrodes, a hole blocking
layer between the first electrode and the active layer, and a hole
carrier layer between the second electrode and the active layer. At
least one of the electrodes is in the form of a mesh. The active
layer includes an electron acceptor material and an electron donor
material. In some embodiments, two or more of the photovoltaic
cells are electrically connected in parallel. In certain
embodiments, two or more of the photovoltaic cells are electrically
connected in series. In certain embodiments, two or more of the
photovoltaic cells are electrically connected in parallel, and two
or more different photovoltaic cells are electrically connected in
series.
[0010] Embodiments can include one or more of the following
aspects.
[0011] The mesh electrode can be a cathode or an anode. In some
embodiments, a photovoltaic cell has a mesh cathode and a mesh
anode.
[0012] The mesh electrode can be formed of wires. The wires can be
formed of an electrically conductive material, such as an
electrically conductive metal, an electrically conductive alloy, or
an electrically conductive polymer. The wires can include a coating
of an electrically conductive material (an electrically conductive
metal, an electrically conductive alloy, or an electrically
conductive polymer).
[0013] The mesh electrode can be, for example, an expanded mesh or
a woven mesh. The mesh can be formed of an electrically conductive
material (an electrically conductive metal, an electrically
conductive alloy, or an electrically conductive polymer). The mesh
can include a coating of an electrically conductive material (an
electrically conductive metal, an electrically conductive alloy, or
an electrically conductive polymer).
[0014] The electron acceptor material can be, for example, formed
of fullerenes, inorganic nanoparticles, discotic liquid crystals,
carbon nanorods, inorganic nanorods, oxadiazoles, or polymers
containing moieties capable of accepting electrons or forming
stable anions (e.g., polymers containing CN groups, polymers
containing CF.sub.3 groups). In some embodiments, the electron
acceptor material is a substituted fullerene.
[0015] The electron donor material can be formed of discotic liquid
crystals, polythiophenes, polyphenylenes, polyphenylvinylenes,
polysilanes, polythienylvinylenes and/or polyisothianaphthalenes.
In some embodiments, the electron donor material is
poly(3-hexylthiophene).
[0016] A photovoltaic cell can further include a hole blocking
layer between the active layer and an anode (e.g., a mesh anode or
a non-mesh anode). The hole blocking layer can be formed of, for
example, LiF or metal oxides.
[0017] A photovoltaic cell can also include a hole carrier layer
between the active layer and the cathode (e.g., a mesh cathode or
non-mesh cathode). The hole carrier layer can be formed of, for
example, polythiophenes, polyanilines, and/or polyvinylcarbazoles,
or polyions of one or more of these polymers.
[0018] In some embodiments, the hole carrier layer is in contact
with a substrate that supports that cathode.
[0019] In certain embodiments, the photovoltaic cell further
includes an adhesive material between the substrate that supports
the cathode and the hole carrier layer. In general, an adhesive
material can adhere material layers in contact with the adhesive
during standard operating conditions of a photovoltaic cell. In
some embodiments, an adhesive includes one or more thermoplastics,
thermosets, or pressure sensitive adhesives.
[0020] In some embodiments, the photovoltaic cell or photovoltaic
system is electrically connected to an external load.
[0021] Embodiments can provide one or more of the following
advantages.
[0022] In some embodiments, a mesh electrode can provide good
electrical conductivity because it is formed of an electrically
conductive material (as opposed to a semiconductor material), while
at the same time having a structure (e.g., a mesh structure) that
allows a sufficient amount of light therethrough so that the
photovoltaic cell is more efficient at converting light into
electrical energy.
[0023] In certain embodiments, a mesh electrode can be sufficiently
flexible to allow the mesh electrode to be incorporated in the
photovoltaic cell using a continuous, roll-to-roll manufacturing
process, thereby allowing manufacture of the photovoltaic cell at
relatively high throughput.
[0024] Using one or more mesh electrodes can reduce the cost and/or
complexity associated with manufacturing a photovoltaic cell.
[0025] A photovoltaic cell having one or more mesh electrodes can
transfer energy in the form of light to energy in the form of
electricity in a more efficient manner compared to certain
semiconductive electrodes.
[0026] Other features and advantages will be apparent from the
description, drawings and from the claims.
DESCRIPTION OF DRAWINGS
[0027] FIG. 1 is a cross-sectional view of an embodiment of a
photovoltaic cell;
[0028] FIG. 2 is an elevational view of an embodiment of a mesh
electrode;
[0029] FIG. 3 is a cross-sectional view of the mesh electrode of
2;
[0030] FIG. 4 is a cross-sectional view of a portion of a mesh
electrode;
[0031] FIG. 5 is a cross-sectional view of another embodiment of a
photovoltaic cell;
[0032] FIG. 6 is a schematic of a system containing multiple
photovoltaic cells electrically connected in series; and
[0033] FIG. 7 is a schematic of a system containing multiple
photovoltaic cells electrically connected in parallel.
DETAILED DESCRIPTION
[0034] FIG. 1 shows a cross-sectional view of a photovoltaic cell
100 that includes a transparent substrate 110, a mesh cathode 120,
a hole carrier layer 130, a photoactive layer (containing an
electron acceptor material and an electron donor material) 140, a
hole blocking layer 150, an anode 160, and a substrate 170.
[0035] In general, during use, light impinges on the surface of
substrate 110, and passes through substrate 110, the openings in
cathode 120 and hole carrier layer 130. The light then interacts
with photoactive layer 140, causing electrons to be transferred
from the electron donor material in layer 140 to the electron
acceptor material in layer 140. The electron acceptor material then
transmits the electrons through hole blocking layer 150 to anode
160, and the electron donor material transfers holes through hole
carrier layer 130 to mesh cathode 120. Anode 160 and mesh cathode
120 are in electrical connection via an external load so that
electrons pass from anode 160, through the load, and to cathode
120.
[0036] As shown in FIGS. 2 and 3, mesh cathode 120 includes solid
regions 122 and open regions 124. In general, regions 122 are
formed of electrically conducting material so that mesh cathode 120
can allow light to pass therethrough via regions 124 and conduct
electrons via regions 122.
[0037] The area of mesh cathode 120 occupied by open regions 124
(the open area of mesh cathode 120) can be selected as desired.
Generally, the open area of mesh cathode 120 is at least about 10%
(e.g., at least about 20%, at least about 30%, at least about 40%,
at least about 50%, at least about 60%, at least about 70%, at
least about 80%) and/or at most about 99% (e.g., at most about 95%,
at most about 90%, at most about 85%) of the total area of mesh
cathode 120.
[0038] Mesh cathode 120 can be prepared in various ways. In some
embodiments, mesh cathode 120 is a woven mesh formed by weaving
wires of material that form solid regions 122. The wires can be
woven using, for example, a plain weave, a Dutch, weave, a twill
weave, a Dutch twill weave, or combinations thereof. In certain
embodiments, mesh cathode 120 is formed of a welded wire mesh. In
some embodiments, mesh cathode 120 is an expanded mesh formed. An
expanded metal mesh can be prepared, for example, by removing
regions 124 (e.g., via laser removal, via chemical etching, via
puncturing) from a sheet of material (e.g., an electrically
conductive material, such as a metal), followed by stretching the
sheet (e.g., stretching the sheet in two dimensions). In certain
embodiments, mesh cathode 120 is a metal sheet formed by removing
regions 124 (e.g., via laser removal, via chemical etching, via
puncturing) without subsequently stretching the sheet.
[0039] In certain embodiments, solid regions 122 are formed
entirely of an electrically conductive material (e.g., regions 122
are formed of a substantially homogeneous material that is
electrically conductive). Examples of electrically conductive
materials that can be used in regions 122 include electrically
conductive metals, electrically conductive alloys and electrically
conductive polymers. Exemplary electrically conductive metals
include gold, silver, copper, nickel, palladium, platinum and
titanium. Exemplary electrically conductive alloys include
stainless steel (e.g., 332 stainless steel, 316 stainless steel),
alloys of gold, alloys of silver, alloys of copper, alloys of
nickel, alloys of palladium, alloys of platinum and alloys of
titanium. Exemplary electrically conducting polymers include
polythiophenes (e.g., poly(3,4-ethelynedioxythiophene) (PEDOT)),
polyanilines (e.g., doped polyanilines), polypyrroles (e.g., doped
polypyrroles). In some embodiments, combinations of electrically
conductive materials are used.
[0040] As shown in FIG. 4, in some embodiments, solid regions 122
are formed of a material 302 that is coated with a different
material 304 (e.g., using metallization, using vapor deposition).
In general, material 302 can be formed of any desired material
(e.g., an electrically insulative material, an electrically
conductive material, or a semiconductive material), and material
304 is an electrically conductive material. Examples of
electrically insulative material from which material 302 can be
formed include textiles, optical fiber materials, polymeric
materials (e.g., a nylon) and natural materials (e.g., flax,
cotton, wool, silk). Examples of electrically conductive materials
from which material 302 can be formed include the electrically
conductive materials disclosed above. Examples of semiconductive
materials from which material 302 can be formed include indium tin
oxide, fluorinated tin oxide, tin oxide and zinc oxide. In some
embodiments, material 302 is in the form of a fiber, and material
304 is an electrically conductive material that is coated on
material 302. In certain embodiments, material 302 is in the form
of a mesh (see discussion above) that, after being formed into a
mesh, is coated with material 304. As an example, material 302 can
be an expanded metal mesh, and material 304 can be PEDOT that is
coated on the expanded metal mesh.
[0041] Generally, the maximum thickness of mesh cathode 120 (i.e.,
the maximum thickness of mesh cathode 120 in a direction
substantially perpendicular to the surface of substrate 110 in
contact with mesh cathode 120) should be less than the total
thickness of hole carrier layer 130. Typically, the maximum
thickness of mesh cathode 120 is at least 0.1 micron (e.g., at
least about 0.2 micron, at least about 0.3 micron, at least about
0.4 micron, at least about 0.5 micron, at least about 0.6 micron,
at least about 0.7 micron, at least about 0.8 micron, at least
about 0.9 micron, bat least about one micron) and/or at most about
10 microns (e.g., at most about nine microns, at most about eight
microns, at most about seven microns, at most about six microns, at
most about five microns, at most about four microns, at most about
three microns, at most about two microns).
[0042] While shown in FIG. 2 as having a rectangular shape, open
regions 124 can generally have any desired shape (e.g., square,
circle, semicircle, triangle, diamond, ellipse, trapezoid,
irregular shape). In some embodiments, different open regions 124
in mesh cathode 120 can have different shapes.
[0043] Although shown in FIG. 3 as having square cross-sectional
shape, solid regions 122 can generally have any desired shape
(e.g., rectangle, circle, semicircle, triangle, diamond, ellipse,
trapezoid, irregular shape). In some embodiments, different solid
regions 122 in mesh cathode 120 can have different shapes.
[0044] In some embodiments, mesh cathode 120 is flexible (e.g.,
sufficiently flexible to be incorporated in photovoltaic cell 100
using a continuous, roll-to-roll manufacturing process). In certain
embodiments, mesh cathode 120 is semi-rigid or inflexible. In some
embodiments, different regions of mesh cathode 120 can be flexible,
semi-rigid or inflexible (e.g., one or more regions flexible and
one or more different regions semi-rigid, one or more regions
flexible and one or more different regions inflexible).
[0045] Substrate 110 is generally formed of a transparent material.
As referred to herein, a transparent material is a material which,
at the thickness used in a photovoltaic cell 100, transmits at
least about 60% (e.g., at least about 70%, at least about 75%, at
least about 80%, at least about 85%) of incident light at a
wavelength or a range of wavelengths used during operation of the
photovoltaic cell. Exemplary materials from which substrate 110 can
be formed include polyethylene terephthalates, polyimides,
polyethylene naphthalates, polymeric hydrocarbons, cellulosic
polymers, polycarbonates, polyamides, polyethers and polyether
ketones. In certain embodiments, the polymer can be a fluorinated
polymer. In some embodiments, combinations of polymeric materials
are used. In certain embodiments, different regions of substrate
110 can be formed of different materials.
[0046] In general, substrate 110 can be flexible, semi-rigid or
rigid (e.g., glass). In some embodiments, substrate 110 has a
flexural modulus of less than about 5,000 megaPascals. In certain
embodiments, different regions of substrate 110 can be flexible,
semi-rigid or inflexible (e.g., one or more regions flexible and
one or more different regions semi-rigid, one or more regions
flexible and one or more different regions inflexible).
[0047] Typically, substrate 110 is at least about one micron (e.g.,
at least about five microns, at least about 10 microns) thick
and/or at most about 1,000 microns (e.g., at most about 500 microns
thick, at most about 300 microns thick, at most about 200 microns
thick, at most about 100 microns, at most about 50 microns)
thick.
[0048] Generally, substrate 110 can be colored or non-colored. In
some embodiments, one or more portions of substrate 110 is/are
colored while one or more different portions of substrate 110
is/are non-colored.
[0049] Substrate 110 can have one planar surface (e.g., the surface
on which light impinges), two planar surfaces (e.g., the surface on
which light impinges and the opposite surface), or no planar
surfaces. A non-planar surface of substrate 110 can, for example,
be curved or stepped. In some embodiments, a non-planar surface of
substrate 110 is patterned (e.g., having patterned steps to form a
Fresnel lens, a lenticular lens or a lenticular prism).
[0050] Hole carrier layer 130 is generally formed of a material
that, at the thickness used in photovoltaic cell 100, transports
holes to mesh cathode 120 and substantially blocks the transport of
electrons to mesh cathode 120. Examples of materials from which
layer 130 can be formed include polythiophenes (e.g., PEDOT),
polyanilines, polyvinylcarbazoles, polyphenylenes,
polyphenylvinylenes, polysilanes, polythienylenevinylenes and/or
polyisothianaphthanenes. In some embodiments, hole carrier layer
130 can include combinations of hole carrier materials.
[0051] In general, the distance between the upper surface of hole
carrier layer 130 (i.e., the surface of hole carrier layer 130 in
contact with active layer 140) and the upper surface of substrate
110 (i.e., the surface of substrate 110 in contact with mesh
electrode 120) can be varied as desired. Typically, the distance
between the upper surface of hole carrier layer 130 and the upper
surface of mesh cathode 120 is at least 0.01 micron (e.g., at least
about 0.05 micron, at least about 0.1 micron, at least about 0.2
micron, at least about 0.3 micron, at least about 0.5 micron)
and/or at most about five microns (e.g., at most about three
microns, at most about two microns, at most about one micron). In
some embodiments, the distance between the upper surface of hole
carrier layer 130 and the upper surface of mesh cathode 120 is from
about 0.01 micron to about 0.5 micron.
[0052] Active layer 140 generally contains an electron acceptor
material and an electron donor material.
[0053] Examples of electron acceptor materials include formed of
fullerenes, oxadiazoles, carbon nanorods, discotic liquid crystals,
inorganic nanoparticles (e.g., nanoparticles formed of zinc oxide,
tungsten oxide, indium phosphide, cadmium selenide and/or lead
sulphide), inorganic nanorods (e.g., nanorods formed of zinc oxide,
tungsten oxide, indium phosphide, cadmium selenide and/or lead
sulphide), or polymers containing moieties capable of accepting
electrons or forming stable anions (e.g., polymers containing CN
groups, polymers containing CF.sub.3 groups). In some embodiments,
the electron acceptor material is a substituted fullerene (e.g.,
PCBM). In some embodiments, active layer 140 can include a
combination of electron acceptor materials.
[0054] Examples of electron donor materials include discotic liquid
crystals, polythiophenes, polyphenylenes, polyphenylvinylenes,
polysilanes, polythienylvinylenes, and polyisothianaphthalenes. In
some embodiments, the electron donor material is
poly(3-hexylthiophene). In certain embodiments, active layer 140
can include a combination of electron donor materials.
[0055] Generally, active layer 140 is sufficiently thick to be
relatively efficient at absorbing photons impinging thereon to form
corresponding electrons and holes, and sufficiently thin to be
relatively efficient at transporting the holes and electrons to
layers 130 and 150, respectively. In certain embodiments, layer 140
is at least 0.05 micron (e.g., at least about 0.1 micron, at least
about 0.2 micron, at least about 0.3 micron) thick and/or at most
about one micron (e.g., at most about 0.5 micron, at most about 0.4
micron) thick. In some embodiments, layer 140 is from about 0.1
micron to about 0.2 micron thick.
[0056] Hole blocking layer 150 is general formed of a material
that, at the thickness used in photovoltaic cell 100, transports
electrons to anode 160 and substantially blocks the transport of
holes to anode 160. Examples of materials from which layer 150 can
be formed include LiF and metal oxides (e.g., zinc oxide, titanium
oxide).
[0057] Typically, hole blocking layer 150 is at least 0.02 micron
(e.g., at least about 0.03 micron, at least about 0.04 micron, at
least about 0.05 micron) thick and/or at most about 0.5 micron
(e.g., at most about 0.4 micron, at most about 0.3 micron, at most
about 0.2 micron, at most about 0.1 micron) thick.
[0058] Anode 160 is generally formed of an electrically conductive
material, such as one or more of the electrically conductive
materials noted above. In some embodiments, anode 160 is formed of
a combination of electrically conductive materials.
[0059] Substrate 170 can be formed of a transparent material or a
non-transparent material. For example, in embodiments in which
photovoltaic cell uses light that passes through anode 160 during
use, substrate 170 is desirably formed of a transparent
material.
[0060] Exemplary materials from which substrate 170 can be formed
include polyethylene terephthalates, polyimides, polyethylene
naphthalates, polymeric hydrocarbons, cellulosic polymers,
polycarbonates, polyamides, polyethers and polyether ketones. In
certain embodiments, the polymer can be a fluorinated polymer. In
some embodiments, combinations of polymeric materials are used. In
certain embodiments, different regions of substrate 110 can be
formed of different materials.
[0061] In general, substrate 170 can be flexible, semi-rigid or
rigid. In some embodiments, substrate 170 has a flexural modulus of
less than about 5,000 megaPascals. In certain embodiments,
different regions of substrate 170 can be flexible, semi-rigid or
inflexible (e.g., one or more regions flexible and one or more
different regions semi-rigid, one or more regions flexible and one
or more different regions inflexible). Generally, substrate 170 is
substantially non-scattering.
[0062] Typically, substrate 170 is at least about one micron (e.g.,
at least about five microns, at least about 10 microns) thick
and/or at most about 200 microns (e.g., at most about 100 microns,
at most about 50 microns) thick.
[0063] Generally, substrate 170 can be colored or non-colored. In
some embodiments, one or more portions of substrate 170 is/are
colored while one or more different portions of substrate 170
is/are non-colored.
[0064] Substrate 170 can have one planar surface (e.g., the surface
of substrate 170 on which light impinges in embodiments in which
during use photovoltaic cell 100 uses light that passes through
anode 160), two planar surfaces (e.g., the surface of substrate 170
on which light impinges in embodiments in which during use
photovoltaic cell 100 uses light that passes through anode 160 and
the opposite surface of substrate 170), or no planar surfaces. A
non-planar surface of substrate 170 can, for example, be curved or
stepped. In some embodiments, a non-planar surface of substrate 170
is patterned (e.g., having patterned steps to form a Fresnel lens,
a lenticular lens or a lenticular prism).
[0065] FIG. 5 shows a cross-sectional view of a photovoltaic cell
400 that includes an adhesive layer 410 between substrate 110 and
hole carrier layer 130.
[0066] Generally, any material capable of holding mesh cathode 130
in place can be used in adhesive layer 410. In general, adhesive
layer 410 is formed of a material that is transparent at the
thickness used in photovoltaic cell 400. Examples of adhesives
include epoxies and urethanes. Examples of commercially available
materials that can be used in adhesive layer 410 include Bynel.TM.
adhesive (DuPont) and 615 adhesive (3M). In some embodiments, layer
410 can include a fluorinated adhesive. In certain embodiments,
layer 410 contains an electrically conductive adhesive. An
electrically conductive adhesive can be formed of, for example, an
inherently electrically conductive polymer, such as the
electrically conductive polymers disclosed above (e.g., PEDOT). An
electrically conductive adhesive can be also formed of a polymer
(e.g., a polymer that is not inherently electrically conductive)
that contains one or more electrically conductive materials (e.g.,
electrically conductive particles). In some embodiments, layer 410
contains an inherently electrically conductive polymer that
contains one or more electrically conductive materials.
[0067] In some embodiments, the thickness of layer 410 (i.e., the
thickness of layer 410 in a direction substantially perpendicular
to the surface of substrate 110 in contact with layer 410) is less
thick than the maximum thickness of mesh cathode 120. In some
embodiments, the thickness of layer 410 is at most about 90% (e.g.,
at most about 80%, at most about 70%, at most about 60%, at most
about 50%, at most about 40%, at most about 30%, at most about 20%)
of the maximum thickness of mesh cathode 120. In certain
embodiments, however, the thickness of layer 410 is about the same
as, or greater than, the maximum thickness of mesh cathode 130.
[0068] In general, a photovoltaic cell having a mesh cathode can be
manufactured as desired.
[0069] In some embodiments, a photovoltaic cell can be prepared as
follows. Electrode 160 is formed on substrate 170 using
conventional techniques, and hole-blocking layer 150 is formed on
electrode 160 (e.g., using a vacuum deposition process or a
solution coating process). Active layer 140 is formed on
hole-blocking layer 150 (e.g., using a solution coating process,
such as slot coating, spin coating or gravure coating). Hole
carrier layer 130 is formed on active layer 140 (e.g., using a
solution coating process, such as slot coating, spin coating or
gravure coating). Mesh cathode 120 is partially disposed in hole
carrier layer 130 (e.g., by disposing mesh cathode 120 on the
surface of hole carrier layer 130, and pressing mesh cathode 120).
Substrate 110 is then formed on mesh cathode 120 and hole carrier
layer 130 using conventional methods.
[0070] In certain embodiments, a photovoltaic cell can be prepared
as follows. Electrode 160 is formed on substrate 170 using
conventional techniques, and hole-blocking layer 150 is formed on
electrode 160 (e.g., using a vacuum deposition or a solution
coating process). Active layer 140 is formed on hole-blocking layer
150 (e.g., using a solution coating process, such as slot coating,
spin coating or gravure coating). Hole carrier layer 130 is formed
on active layer 140 (e.g., using a solution coating process, such
as slot coating, spin coating or gravure coating). Adhesive layer
410 is disposed on hole carrier layer 130 using conventional
methods. Mesh cathode 120 is partially disposed in adhesive layer
410 and hole carrier layer 130 (e.g., by disposing mesh cathode 120
on the surface of adhesive layer 410, and pressing mesh cathode
120). Substrate 110 is then formed on mesh cathode 120 and adhesive
layer 410 using conventional methods.
[0071] While the foregoing processes involve partially disposing
mesh cathode 120 in hole carrier layer 130, in some embodiments,
mesh cathode 120 is formed by printing the cathode material on the
surface of carrier layer 130 or adhesive layer 410 to provide an
electrode having the open structure shown in the figures. For
example, mesh cathode 120 can be printed using an inkjet printer, a
screen printer, or gravure printer. The cathode material can be
disposed in a paste which solidifies upon heating or radiation
(e.g., UV radiation, visible radiation, IR radiation, electron beam
radiation). The cathode material can be, for example, vacuum
deposited in a mesh pattern through a screen or after deposition it
may be patterned by photolithography.
[0072] Multiple photovoltaic cells can be electrically connected to
form a photovoltaic system. As an example, FIG. 6 is a schematic of
a photovoltaic system 500 having a module 510 containing
photovoltaic cells 520. Cells 520 are electrically connected in
series, and system 500 is electrically connected to a load. As
another example, FIG. 7 is a schematic of a photovoltaic system 600
having a module 610 that contains photovoltaic cells 620. Cells 620
are electrically connected in parallel, and system 600 is
electrically connected to a load. In some embodiments, some (e.g.,
all) of the photovoltaic cells in a photovoltaic system can have
one or more common substrates. In certain embodiments, some
photovoltaic cells in a photovoltaic system are electrically
connected in series, and some of the photovoltaic cells in the
photovoltaic system are electrically connected in parallel.
[0073] While certain embodiments have been disclosed, other
embodiments are also possible.
[0074] As another example, while cathodes formed of mesh have been
described, in some embodiments a mesh anode can be used. This can
be desirable, for example, when light transmitted by the anode is
used. In certain embodiments, both a mesh cathode and a mesh anode
are used. This can be desirable, for example, when light
transmitted by both the cathode and the anode is used.
[0075] As an example, while embodiments have generally been
described in which light that is transmitted via the cathode side
of the cell is used, in certain embodiments light transmitted by
the anode side of the cell is used (e.g., when a mesh anode is
used). In some embodiments, light transmitted by both the cathode
and anode sides of the cell is used (when a mesh cathode and a mesh
anode are used).
[0076] As a further example, while electrodes (e.g., mesh
electrodes, non-mesh electrodes) have been described as being
formed of electrically conductive materials, in some embodiments a
photovoltaic cell may include one or more electrodes (e.g., one or
more mesh electrodes, one or more non-mesh electrodes) formed of a
semiconductive material. Examples of semiconductive materials
include indium tin oxide, fluorinated tin oxide, tin oxide and zinc
oxide.
[0077] As an additional example, in some embodiments, one or more
semiconductive materials can be disposed in the open regions of a
mesh electrode (e.g., in the open regions of a mesh cathode, in the
open regions of a mesh anode, in the open regions of a mesh cathode
and the open regions of a mesh anode). Examples of semiconductive
materials include tin oxide, fluorinated tin oxide, tin oxide and
zinc oxide. Typically, the semiconductive material disposed in an
open region of a mesh electrode is transparent at the thickness
used in the photovoltaic cell.
[0078] As another example, in certain embodiments, a protective
layer can be applied to one or both of the substrates. A protective
layer can be used to, for example, keep contaminants (e.g., dirt,
water, oxygen, chemicals) out of a photovoltaic cell and/or to
ruggedize the cell. In certain embodiments, a protective layer can
be formed of a polymer (e.g., a fluorinated polymer).
[0079] As a further example, while certain types of photovoltaic
cells have been described that have one or more mesh electrodes,
one or more mesh electrodes (mesh cathode, mesh anode, mesh cathode
and mesh anode) can be used in other types of photovoltaic cells as
well. Examples of such photovoltaic cells include photoactive cells
with an active material formed of amorphous silicon, cadmium
selenide, cadmium telluride, copper indium sulfide, and copper
indium gallium arsenide.
[0080] As an additional example, while described as being formed of
different materials, in some embodiments materials 302 and 304 are
formed of the same material.
[0081] As another example, although shown in FIG. 4 as being formed
of one material coated on a different material, in some embodiments
solid regions 122 can be formed of more than two coated materials
(e.g., three coated materials, four coated materials, five coated
materials, six coated materials.
[0082] Other embodiments are in the claims.
* * * * *