U.S. patent application number 14/462334 was filed with the patent office on 2014-12-04 for optoelectronic device with bypass diode.
The applicant listed for this patent is SUNPOWER CORPORATION. Invention is credited to Nicholas Boitnott, David B. DeGraaff, Keith Johnston, Ryan Linderman, Doug Rose.
Application Number | 20140352761 14/462334 |
Document ID | / |
Family ID | 44080816 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140352761 |
Kind Code |
A1 |
Linderman; Ryan ; et
al. |
December 4, 2014 |
OPTOELECTRONIC DEVICE WITH BYPASS DIODE
Abstract
Optoelectronic devices with bypass diodes are described. An
optoelectronic device includes a bypass diode, a heat spreader unit
disposed above, and extending over, the bypass diode, and a heat
sink disposed above the heat spreader unit. Another optoelectronic
device includes a bypass diode, a heat spreader unit disposed
above, but not extending over, the bypass diode, and a heat sink
disposed above the heat spreader unit.
Inventors: |
Linderman; Ryan; (Oakland,
CA) ; Rose; Doug; (San Jose, CA) ; Boitnott;
Nicholas; (Half Moon Bay, CA) ; Johnston; Keith;
(Palo Alto, CA) ; DeGraaff; David B.; (Mountain
View, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SUNPOWER CORPORATION |
San Jose |
CA |
US |
|
|
Family ID: |
44080816 |
Appl. No.: |
14/462334 |
Filed: |
August 18, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12844594 |
Jul 27, 2010 |
8809671 |
|
|
14462334 |
|
|
|
|
61267637 |
Dec 8, 2009 |
|
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|
Current U.S.
Class: |
136/246 |
Current CPC
Class: |
H02S 40/42 20141201;
H01L 31/02021 20130101; H01L 31/054 20141201; H01L 31/0504
20130101; H02S 40/22 20141201; H01L 27/1421 20130101; Y02E 10/52
20130101; H02S 40/345 20141201; H01L 31/052 20130101 |
Class at
Publication: |
136/246 |
International
Class: |
H01L 31/052 20060101
H01L031/052; H01L 31/05 20060101 H01L031/05 |
Claims
1-11. (canceled)
12. A solar cell, comprising: a bypass diode; a heat spreader unit
disposed above, but not extending over, the bypass diode; and a
heat sink disposed above the heat spreader unit.
13. The solar cell of claim 12, wherein the bypass diode is
disposed in a through-hole via disposed in the heat spreader
unit.
14. The solar cell of claim 12, wherein the bypass diode is coupled
with a pair of interconnects, the heat spreader unit disposed above
the pair of interconnects.
15. The solar cell of claim 14, wherein the bypass diode and the
pair of interconnects are disposed above a transparent superstrate,
wherein the bypass diode is coupled with the pair of interconnects
by one or more bond pads, and wherein the bypass diode is separated
from the transparent superstrate and the heat spreader unit by one
or more encapsulant layers.
16. The solar cell of claim 12, wherein the heat sink comprises a
folded fin separated from the heat spreader unit by one or more
thermal adhesive layers.
17. A solar system, comprising: a plurality of pairs of solar
cells; a plurality of bypass diodes, one or more bypass diodes
disposed between each of the pairs of solar cells; a plurality of
heat spreader units, one or more heat spreader units disposed
above, but not extending over, each of the bypass diodes; and a
plurality of heat sinks, one or more heat sinks disposed above each
of the heat spreader units.
18. The solar system of claim 17, further comprising: a solar
concentrating element disposed above the plurality of pairs of
solar cells, the solar concentrating element to concentrate
insolation on light-receiving surfaces of the pairs of solar cells,
wherein the plurality of bypass diodes is configured to bypass one
or more of the pairs of the solar cells when insolation is not
received by the one or more of the pairs of the solar cells.
19. The solar system of claim 18, wherein solar concentrating
element is an element selected from the group consisting of a
mirror, a grouping of minors, a lens, a grouping of lenses, and a
combination of one or more minors with one or more lenses.
20. The solar system of claim 17, wherein each bypass diode is
disposed in a through-hole via disposed in one of the heat spreader
units.
21. The solar system of claim 17, wherein each bypass diode is
coupled with a pair of interconnects, one of the heat spreader
units disposed above the pair of interconnects.
22. The solar system of claim 21, wherein each bypass diode and the
respective pair of interconnects are disposed above a transparent
superstrate, wherein each bypass diode is coupled with the
respective pair of interconnects by one or more bond pads, and
wherein each bypass diode is separated from the transparent
superstrate and the heat spreader unit by one or more encapsulant
layers.
23. The solar system of claim 17, wherein each heat sink comprises
a folded fin separated from the respective heat spreader unit by
one or more thermal adhesive layers.
24. The solar system of claim 17, wherein the plurality of heat
spreader units is provided to couple heat from plurality of pairs
of solar cells with the plurality of heat sinks.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/267,637, filed Dec. 8, 2009, the entire contents
of which are hereby incorporated by reference herein.
TECHNICAL FIELD
[0002] Embodiments of the present invention are in the field of
renewable energy and, in particular, optoelectronic devices and
systems with bypass diodes.
BACKGROUND
[0003] Light-emitting diode (LED) and photovoltaic (PV) devices are
two common types of optoelectronic devices. Thermal management and
assembly of optoelectronic systems, such as systems including LED
and PV devices, may be considered when evaluating such systems for
fabrication and deployment. For example, the area of systems of
devices with integrated bypass diodes is one area ripe for
improvements in thermal management and assembly. Challenges for the
fabrication and deployment of such systems include a possible need
for a low resistance thermal path between the bypass diode and a
heat sink, as well as a robust electrical isolation of operating
voltages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 illustrates a plan view of a conventional
optoelectronic system including a bypass circuit path and
externally mounted diode.
[0005] FIG. 2A illustrates a plan view of a portion of an
optoelectronic system with internal bypass diodes, in accordance
with an embodiment of the present invention.
[0006] FIG. 2B illustrates a plan view of a portion of an
optoelectronic system with internal bypass diodes, in accordance
with an embodiment of the present invention.
[0007] FIG. 3 illustrates an isometric view of a portion of an
optoelectronic system with internal bypass diodes, in accordance
with an embodiment of the present invention.
[0008] FIG. 4 illustrates a cross-sectional view of an
optoelectronic device with a bypass diode, in accordance with an
embodiment of the present invention.
[0009] FIG. 5 illustrates a cross-sectional view of an
optoelectronic device with a bypass diode, in accordance with an
embodiment of the present invention.
[0010] FIG. 6 illustrates a top-down view of an optoelectronic
device with a heat spreader unit, in accordance with an embodiment
of the present invention.
[0011] FIG. 7A illustrates a solar concentrator apparatus with a
summer solstice illumination pattern, in accordance with an
embodiment of the present invention.
[0012] FIG. 7B illustrates a solar concentrator apparatus with a
winter solstice illumination pattern, in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION
[0013] Optoelectronic devices with bypass diodes and optoelectronic
systems with bypass diodes are described herein. In the following
description, numerous specific details are set forth, such as
specific arrangements of heat spreader units relative to bypass
diodes, in order to provide a thorough understanding of embodiments
of the present invention. It will be apparent to one skilled in the
art that embodiments of the present invention may be practiced
without these specific details. In other instances, well-known
fabrication techniques, such as lamination techniques, are not
described in detail in order to not unnecessarily obscure
embodiments of the present invention. Furthermore, it is to be
understood that the various embodiments shown in the Figures are
illustrative representations and are not necessarily drawn to
scale.
[0014] Disclosed herein are optoelectronic devices with bypass
diodes. In one embodiment, an optoelectronic device includes a
bypass diode. A heat spreader unit is disposed above, and extending
over, the bypass diode. A heat sink is disposed above the heat
spreader unit. In one embodiment, an optoelectronic device includes
a bypass diode. A heat spreader unit is disposed above, but not
extending over, the bypass diode. A heat sink is disposed above the
heat spreader unit. In one embodiment, the optoelectronic device is
a photovoltaic cell.
[0015] Also disclosed herein are optoelectronic systems with bypass
diodes. In one embodiment, an optoelectronic system includes a
plurality of pairs of optoelectronic devices. The optoelectronic
system also includes a plurality of bypass diodes, one or more of
the bypass diodes disposed between each of the pairs of
optoelectronic devices. Also included is a plurality of heat
spreader units, one or more of the heat spreader units disposed
above, and extending over, each of the bypass diodes. The
optoelectronic system also includes a plurality of heat sinks, one
or more of the heat sinks disposed above each of the heat spreader
units. In one embodiment, an optoelectronic system includes a
plurality of pairs of optoelectronic devices. The optoelectronic
system also includes a plurality of bypass diodes, one or more of
the bypass diodes disposed between each of the pairs of
optoelectronic devices. Also included is a plurality of heat
spreader units, one or more of the heat spreader units disposed
above, but not extending over, each of the bypass diodes. The
optoelectronic system also includes a plurality of heat sinks, one
or more of the heat sinks disposed above each of the heat spreader
units. In one embodiment, the plurality of optoelectronic devices
is a plurality of photovoltaic cells.
[0016] Thermal management and assembly of optoelectronic systems,
such as light-emitting diode (LED) or photovoltaic (PV) systems,
may be addressed by integrating bypass diodes within a cell package
or laminate system. However, in accordance with an embodiment of
the present invention, due to a high density of dissipated power
within such a diode, a low thermal resistance path to ambient air
may be needed in order to ensure reliable operation of a
corresponding diode and cell enclosure. Furthermore, in order to
facilitate high volume manufacturing, design concepts and assembly
techniques that are based on continuous processing may also be
desirable. In an embodiment, a thermal resistance between a bypass
diode and an external heat sink is reduced, while a more uniform
and flat surface across a high heat flux region of a cell enclosure
or package is provided. In one embodiment, a flat surface along a
back side of a cell enclosure improves interface and bond quality
during attachment of the cell and a bypass diode enclosure to a
heat sink. In an embodiment, the improved thermal performance
allows devices to operate at lower temperatures thereby increasing
light to electrical conversion efficiency and reducing degradation
and failure of components. In addition, in one embodiment, a high
volume continuous manufacturing processes to be used to fabricate
arrays of optoelectronic die for LED lighting applications and
photovoltaic receivers for solar concentrators is enabled.
[0017] Conventional methods of integrating bypass diodes into
systems such as PV and LED systems have involved attaching the
bypass diodes externally to a cell laminate or package with
back-sheet penetrations to allow electrical connections. This
approach may require a significant number of additional assembly
steps and may limit the number of diodes that can be integrated
along a string of cells. In accordance with an embodiment of the
present invention, a flexible substrate is manufactured by
continuous roll processing of metal foils, dielectric layers and
polymer adhesive coatings. In one embodiment, bare optoelectronic
die and bypass diodes are then soldered to the leads of the
substrate or cell interconnects and then encapsulated between a
glass cover sheet and a metal heat spreader integrated within the
substrate at the region of highest heat flux into the die. In a
specific embodiment, shallow pockets or through-holes are punched
into the substrates to accommodate a diode that is thicker than the
cells, allowing for a thin, low resistance thermal coupling to the
heat spreader or substrate. The through-holes or shallow pockets
may allow fabrication of a flatter back surface of the cell package
or enclosure that improves thermal coupling of the heat sink and
cell. A heat spreader with area removed directly over a high heat
density may seem counter-intuitive. However, in a particular
embodiment, since the majority of the diode heat flows to the heat
sink via the interconnects and cell, any improvements in system
thermal management will also improve (e.g., reduce) the diode
temperatures. This may also result in a single thermal solution for
the both the cell and diode. In an aspect of the above particular
embodiment, extending the heat spreader beyond the cell and heat
sink footprint also allows thermal integration of diodes mounted in
a peripheral location to the cell.
[0018] As such, in an embodiment, a portion of an optoelectronic
system is manufactured in roll form to allow for high volume
continuous processing and subsequent assembly of such an
optoelectronic system. In an embodiment, this approach enables a
shift in the way photovoltaic systems are manufactured and
assembled while providing improved thermal and electrical
functionality.
[0019] As photovoltaic systems leverage concentrated optical
technologies to reduce cell size, the benefits of a robust bypass
circuit design may also increase. Since concentrator systems often
have smaller cell areas, a thermal load from back-driving a string
current through such a cell may increase the chance for damage and
permanent failure of the cell as a result of overheating. Perhaps
most significant, in an embodiment, system performance may be
significantly reduced by partial shading, mismatch and other
defects in a string and, thus, a more frequent integration of
bypass diodes (e.g., 1 bypass diode per cell, 1 bypass diode per 2
cells, etc.) may limit the impact of the non-uniformity while
capturing the maximum possible performance of the remaining high
performing cells. Further, in an embodiment, a higher frequency of
diodes limits the reverse voltage across the diode terminals,
reducing the electronic requirements of the device and the
likelihood of a reverse breakdown failure.
[0020] From an assembly and manufacturing perspective, the
integration of a bypass diode into a cell string without back-sheet
penetrations may reduce complexity and secondary manufacturing
steps, providing additional benefits beyond system performance. For
example, in conventional 1-sun photovoltaic modules, the
two-dimensional array of cells are often divided into series cell
strings (typically 3) with a bypass diode allowing electrical
current to bypass, by a parallel path, one or more strings if those
cells are shaded or inoperative. In such a configuration, the
diodes may be centrally located within the junction box which also
houses the cable connections to the module via penetrations from
the back-sheet of the laminated cell array. However, due to the
central location of the junction box, additional electrical leads
may need to be run between the cells at the end of the strings and
the junction box, adding additional cost, assembly steps and
potential failure points. In accordance with an embodiment of the
present invention, while a central junction box is appropriate for
a two-dimensional array of cells, it is not ideal for a
concentrator photovoltaic module with a linear cell array that
would favor connections at opposite ends of the cell string. For
example, creating electrical runs down the entire length of the
concentrator receiver may add significant cost and manufacturing
complexity.
[0021] One additional hurdle that may need to be overcome when
integrating diode systems within a cell laminate or package is the
thermal management requirements of the diodes when they dissipate
power in bypass operation. For example, in an embodiment, while the
power dissipated in the diode is small relative to the system power
(since it is dissipated within the small diode package [e.g., <1
cm.sup.2]), the thermal load density reaches values that may
require thermal coupling to a heat sink (ideally the same heat sink
used for the cells).
[0022] As such, in accordance with an embodiment of the present
invention, a bypass diode or multiple bypass diodes are included
internally within a laminated cell package and are thermally
coupled to a cell mounted heat sink via cell interconnects and, in
some embodiments, an additional integrated heat spreader. In one
embodiment, rather than running additional electrical leads to
bypass a set number of cells, each with back-sheet penetrations and
an externally mounted diode, bypass diodes are integrated between
the cell and interconnects on a diode-per-cell or
diode-per-two-cell basis, as described by comparing the structures
of FIG. 1 and FIGS. 2A and 2B. In an embodiment, an approach such
as the approach described in association with FIG. 2B allows for a
narrower receiver package with lower material costs and a reduced
form factor than the approach of FIG. 1 or FIG. 2A.
[0023] A conventional approach to bypass diodes may be to include
such diodes at a pitch of every 8 cells while utilizing a bypass
circuit path and externally mounted diode with laminate back-sheet
penetrations. For example, FIG. 1 illustrates a plan view of a
conventional optoelectronic system including a bypass circuit path
and externally mounted diode. Referring to FIG. 1, a conventional
photovoltaic system 100 includes a plurality of cells 102. At some
fixed period, an external diode 104 is included for every several
cells. Bypass circuit paths 106 are also included.
[0024] By contrast, in accordance with an embodiment of the present
invention, internal bypass diodes may be included at a pitch of
one-per-two-cells mounted directly to the cell interconnects. In
one embodiment, a cell string is then laminated between a
back-sheet and a glass superstrate to encapsulate diodes with the
cell string. For example, FIG. 2A illustrates a plan view of a
portion of an optoelectronic system with internal bypass diodes, in
accordance with an embodiment of the present invention. Referring
to FIG. 2A, a photovoltaic system 200 includes a plurality of cells
202. Bypass diodes 204 located between cell interconnects 206 on
the upper side of the cell are included, e.g., for every pair of
cells, as depicted in FIG. 2A. As depicted, bypass diodes located
between interconnects on the lower side of the cell may be included
as redundant diodes that allow increased reliability if there are
any failures in bypass diodes 204. Furthermore, these additional
bypass diodes may reduce cost and offer the highest performance for
known illumination irregularities that may occur. Cell
interconnects 206 run between the bypass diodes 204 and parallel to
the pairs of cells 202. In an additional embodiment, not depicted,
additional diodes are placed onto the lower interconnects allowing
the ability to bypass current on a paired cell basis, or even
possibly on a single cell basis. In an embodiment, the frequency of
diodes relative to cell pairs can be increased or decreased at
different locations within the receiver, e.g., at the ends or
central region of a receiver.
[0025] In accordance with an alternative embodiment, FIG. 2B
illustrates a plan view of a portion of an optoelectronic system
with internal bypass diodes, in accordance with an embodiment of
the present invention. Referring to FIG. 2B, a photovoltaic system
250 includes bypass diodes 252 on only one side of the array of
cells 254. In one embodiment, an optional bypass diode 256 is
included in photovoltaic system 250 and is also connected in
parallel to the bypass diodes 252, which are connected in series,
as depicted in FIG. 2B. In a specific embodiment, a voltage drop is
mitigated or avoided that may otherwise occur when several bypass
diodes are connected in series.
[0026] In accordance with an embodiment of the present invention,
by soldering a bypass diode between cell interconnects, the bypass
diode is available for attachment at the same time as the cell
string soldering operation, or may be pre-applied to the
interconnects before the cells are attached. In one embodiment,
this approach eliminates the needs for back-sheet penetrations and
the subsequent assembly steps normally used to attach potted
enclosures to the backside of a laminate to protect external
features of the cell string.
[0027] In accordance with an embodiment of the present invention,
thermal management of bypass diodes is accomplished by creating a
suitable thermal path from the diode to the receiver heat sink via
the cell interconnects. In one embodiment, this approach requires a
modified heat sink that extends beyond the cell to cover the
interconnect area, an interconnect design that maximizes area under
the heat sink and an increased interconnect thickness to allow
better heat spreading down the interconnect as, described in
association with FIG. 3, below.
[0028] Thermal coupling between a bypass diode and heat sink may be
provided via a cell interconnect or a pair of cell interconnects.
For example, FIG. 3 illustrates an isometric view of a portion of
an optoelectronic system with internal bypass diodes, in accordance
with an embodiment of the present invention. Referring to FIG. 3, a
photovoltaic system 300 includes a bypass diode 302 between cell
interconnects 304 and integrated with cells 306. In one embodiment,
cell interconnects 304 include interconnect extensions 308. In
accordance with an embodiment of the present invention, a heat sink
310 is included above the cells 306.
[0029] In an embodiment, enhanced thermal management can also be
accomplished by integrating a heat spreader within a laminate or
thermal package. In one embodiment, a heat spreader extends over a
cell and interconnects and provides a parallel thermal path from a
diode to the heat sink in addition to the cell interconnect. In a
specific embodiment, this approach reduces diode to ambient thermal
resistance and reduces the thermal requirements for the cell
interconnect. In an embodiment, a heat spreader can be designed
with a recessed region to accommodate the diode vertical height or
a through-via that traces the outer perimeter of the diode giving
more vertical flexibility in diode form factor as, described below
in association with FIGS. 4 and 5.
[0030] In an aspect of the present invention, an
interconnect-integrated diode may be included under a heat spreader
with a recessed cavity to accommodate the diode. For example, FIG.
4 illustrates a cross-sectional view of an optoelectronic device
with a bypass diode, in accordance with an embodiment of the
present invention.
[0031] Referring to FIG. 4, an optoelectronic device 400 includes a
bypass diode 402. Optoelectronic device 400 also includes a heat
spreader unit 404 disposed above, and extending over, bypass diode
402. In accordance with an embodiment of the present invention,
heat spreader unit 404 includes one or more dielectric layers 406
and one or more thermally conductive layers 408, as depicted in
FIG. 4. Optoelectronic device 400 also includes a heat sink 410
disposed above heat spreader unit 404.
[0032] Referring again to FIG. 4, in an embodiment, bypass diode
402 is disposed in a recessed cavity 412 under heat spreader unit
404. In an embodiment, bypass diode 402 is coupled with a pair of
interconnects 414, heat spreader unit 404 disposed above the pair
of interconnects 414, as depicted in FIG. 4. In one embodiment,
bypass diode 402 and the pair of interconnects 414 are disposed
above a transparent superstrate 416, bypass diode 402 is coupled
with the pair of interconnects 414 by one or more bond pads 418,
and bypass diode 402 is separated from transparent superstrate 416
and heat spreader unit 404 by one or more encapsulant layers 420.
In an embodiment, heat sink 410 includes a folded fin separated
from heat spreader unit 404 by one or more thermal adhesive layers
422, as depicted in FIG. 4. In an alternative embodiment, not
shown, heat sink 410 includes a plurality of stand-alone fins
coupled by a common base, the common base separated from heat
spreader unit 404 by one or more thermal adhesive layers. In an
embodiment, the S-shaped bend in the bottom lead of diode 402 aids
in reduction of coefficient of thermal expansion related stresses
that may develop during normal operating temperature ranges. In an
additional embodiment, the interconnects 414 are bent with a
similar S-shape and a bare diode die is mounted directly between
the interconnects, removing the need for additional bond pads
between the bare diode die and the diode leads.
[0033] In another embodiment, diode 402 is encapsulated prior to
assembly to form optoelectronic device 400. In one embodiment, this
approach allows for isolation of an elevated temperature of the
diode die, which can tolerate significantly higher temperatures as
compared with optoelectronic system encapsulant 420. In one
embodiment, the material surrounding such an initially encapsulated
diode 402 is itself encapsulated by a material different from
optoelectronic system encapsulant 420, as depicted by the different
shading within the box surrounding diode 402 in FIG. 4.
[0034] In association with the discussion of FIGS. 2-4 above, a
plurality of optoelectronic devices, such as the optoelectronic
device of FIG. 4, may be included in an optoelectronic system.
Thus, in accordance with an embodiment of the present invention, an
optoelectronic system includes a plurality of pairs of
optoelectronic devices. In one embodiment, each optoelectronic
device is a back-contact solar cell. The optoelectronic system also
includes a plurality of bypass diodes, one or more of the bypass
diodes disposed between each of the pairs of optoelectronic
devices. The optoelectronic system also includes a plurality of
heat spreader units, one or more of the heat spreader units
disposed above, and extending over, each of the bypass diodes. The
optoelectronic system also includes a plurality of heat sinks, one
or more of the heat sinks disposed above each of the heat spreader
units.
[0035] In an embodiment, each bypass diode of the above
optoelectronic system is disposed in a recessed cavity under one of
the heat spreader units. In an embodiment, each bypass diode is
coupled with a pair of interconnects, one of the heat spreader
units disposed above the pair of interconnects. In one embodiment,
each bypass diode and the respective pair of interconnects are
disposed above a transparent superstrate, each bypass diode is
coupled with the respective pair of interconnects by one or more
bond pads, and each bypass diode is separated from the substrate
and the heat spreader unit by one or more encapsulant layers. In an
embodiment, each heat sink includes a folded fin separated from the
respective heat spreader unit by one or more thermal adhesive
layers. In an alternative embodiment, each heat sink includes a
plurality of stand-alone fins coupled by a common base, each common
base separated from the respective heat spreader unit by one or
more thermal adhesive layers. In an embodiment, the plurality of
heat spreader units is provided to couple heat from plurality of
pairs of optoelectronic devices with the plurality of heat sinks.
This may differ from an approach where bypass diodes are vertically
integrated in-line with a heat sink and a cell.
[0036] In another aspect of the present invention, an
interconnect-integrated diode may be positioned relative to a heat
spreader with through-hole via to accommodate the diode. For
example, FIG. 5 illustrates a cross-sectional view of an
optoelectronic device with a bypass diode, in accordance with an
embodiment of the present invention.
[0037] Referring to FIG. 5, an optoelectronic device 500 includes a
bypass diode 502. Optoelectronic device 500 also includes a heat
spreader unit 504 disposed above, but not extending over, bypass
diode 502. In accordance with an embodiment of the present
invention, heat spreader unit 504 includes one or more dielectric
layers 506 and one or more thermally conductive layers 508, as
depicted in FIG. 5. Optoelectronic device 500 also includes a heat
sink 510 disposed above heat spreader unit 504.
[0038] Referring again to FIG. 5, in an embodiment, bypass diode
502 is disposed in a through-hole via 512 disposed in heat spreader
unit 504. In an embodiment, bypass diode 502 is coupled with a pair
of interconnects 514, heat spreader unit 504 disposed above the
pair of interconnects 514, as depicted in FIG. 5. In one
embodiment, bypass diode 502 and the pair of interconnects 514 are
disposed above a transparent superstrate 516, bypass diode 502 is
coupled with the pair of interconnects 514 by one or more bond pads
518, and bypass diode 502 is separated from transparent superstrate
516 and heat spreader unit 504 by one or more encapsulant layers
520. In an embodiment, heat sink 510 includes a folded fin
separated from heat spreader unit 504 by one or more thermal
adhesive layers 522, as depicted in FIG. 5. In an alternative
embodiment, not shown, heat sink 510 includes a plurality of
stand-alone fins coupled by a common base, the common base
separated from heat spreader unit 504 by one or more thermal
adhesive layers. In an embodiment, the S-shaped bend in the bottom
lead of diode 502 aids in reduction of coefficient of thermal
expansion related stresses that may develop during normal operating
temperature ranges. In an additional embodiment, the interconnects
514 are bent with a similar S-shape and a bare diode die is mounted
directly between the interconnects, removing the need for
additional bond pads between the bare diode die and the diode
leads.
[0039] In another embodiment, diode 502 is encapsulated prior to
assembly to form optoelectronic device 500. In one embodiment, this
approach allows for isolation of an elevated temperature of the
diode die, which can tolerate significantly higher temperatures as
compared with optoelectronic system encapsulant 520. In one
embodiment, the material surrounding such an initially encapsulated
diode 502 is itself encapsulated by a material different from
optoelectronic system encapsulant 520, as depicted by the different
shading within the box surrounding diode 502 in FIG. 5.
[0040] In association with the discussion of FIGS. 2, 3, and 5
above, a plurality of optoelectronic devices, such as the
optoelectronic device of FIG. 5, may be included in an
optoelectronic system. Thus, in accordance with an embodiment of
the present invention, an optoelectronic system includes a
plurality of pairs of optoelectronic devices. In one embodiment,
each optoelectronic device is a back-contact solar cell. The
optoelectronic system also includes a plurality of bypass diodes,
one or more of the bypass diodes disposed between each of the pairs
of optoelectronic devices. The optoelectronic system also includes
a plurality of heat spreader units, one or more of the heat
spreader units disposed above, but not extending over, each of the
bypass diodes. The optoelectronic system also includes a plurality
of heat sinks, one or more of the heat sinks disposed above each of
the heat spreader units.
[0041] In an embodiment, each bypass diode of the above
optoelectronic system is disposed in a through-hole via disposed in
one of the heat spreader units. In an embodiment, each bypass diode
is coupled with a pair of interconnects, one of the heat spreader
units disposed above the pair of interconnects. In one embodiment,
each bypass diode and the respective pair of interconnects are
disposed above a transparent superstrate, each bypass diode is
coupled with the respective pair of interconnects by one or more
bond pads, and each bypass diode is separated from the substrate
and the heat spreader unit by one or more encapsulant layers. In an
embodiment, each heat sink includes a folded fin separated from the
respective heat spreader unit by one or more thermal adhesive
layers. In an alternative embodiment, each heat sink includes a
plurality of stand-alone fins coupled by a common base, each common
base separated from the respective heat spreader unit by one or
more thermal adhesive layers. In an embodiment, the plurality of
heat spreader units is provided to couple heat from plurality of
pairs of optoelectronic devices with the plurality of heat sinks.
This may differ from an approach where bypass diodes are vertically
integrated in-line with a heat sink and a cell.
[0042] In an aspect of the present invention, the arrangements of
FIGS. 4 and 5 enables the outer surface of the enclosure of
optoelectronic devices 400 and 500, respectively, to be flat,
providing a uniform surface for bonding a heat sink with an
adhesive or other bonding material. FIG. 6 illustrates a top-down
view of an optoelectronic device with a heat spreader unit, in
accordance with an embodiment of the present invention. Referring
to FIG. 6, a system 600 includes two (or more) photovoltaic cells
602 and 604. A cell interconnect 606 is disposed above photovoltaic
cells 602 and 604. In a particular embodiment, photovoltaic cells
602 and 604 are serially connected. Also depicted is a bypass diode
612. In accordance with an embodiment of the present invention, at
least one cell interconnect of the optoelectronic system includes
one or more stress relief features. In one embodiment, partial
through vias 650 around bypass diode 612 and cell bond pad (also at
606) accommodate for potential increased thickness of these
features and ensure a low thermal resistance flat surface for
attaching a heat sink.
[0043] In another aspect of the present invention, bypass diodes
may be used to avoid shaded-cell losses. For example, FIGS. 7A-7B
illustrate a solar concentrator apparatus with a summer solstice
illumination pattern and a winter solstice illumination pattern,
respectively, in accordance with an embodiment of the present
invention.
[0044] Referring to FIG. 7A, a solar concentrator apparatus 700 can
be subjected to an illumination pattern consistent with the sun
being high above the horizon, such as at summer solstice. A solar
concentrating element or collector, such as a lens (as shown in
FIG. 7A), system of lenses, minor, or system of mirrors, is
positioned above an array of solar cells 702. The solar cells in
the array of solar cells 702 are coupled via bypass diodes 704 and
cell interconnects 706. The array of solar cells may also include
heat exchange fins (shown as 708) and a power output wire (not
shown).
[0045] In accordance with an embodiment of the present invention,
insolation 710A is received by the array of solar cells 702 at a
time when the sun is directly above the solar concentrating
element, or collector. In one embodiment, the solar concentrating
element, or collector provides illumination 712A to the entire
array of solar cells 702, as depicted in FIG. 7A.
[0046] Referring to FIG. 7B, the solar concentrator apparatus 700
can also be subjected to an illumination pattern consistent with
the sun being low above the horizon, such as at winter solstice. In
accordance with an embodiment of the present invention, insolation
710B is received by the array of solar cells 702 at a time when the
sun is not directly above the solar concentrating element, or
collector. In one embodiment, the solar concentrating element, or
collector provides illumination 712B to only a portion of the array
of solar cells 702, as depicted in FIG. 7B. In an embodiment, the
cells that are not illuminated cannot pass the required current and
would otherwise be forced into a power dissipation mode (e.g.,
reverse bias) to accommodate the current generated by the
illuminated cells. The cells may then sink some of the generated
power while heating significantly.
[0047] Accordingly, in an embodiment, bypass diodes such as the
bypass diodes described herein are used to remove groupings of
cells at the end or ends of a linear receiver such that little
power is lost due to the cells in the array which are not receiving
and incident insolation. In one embodiment, the bypass diodes on an
array of solar cells are arranged in a way consistent with
optimization of cost and performance. For example, in a specific
embodiment, an arrangement of solar cells and bypass diodes
provides bypassing the final 2, 4, 6, 8 or 10 cells in a linear
grouping of cells.
[0048] Thus, optoelectronic devices with bypass diodes have been
disclosed. In accordance with an embodiment of the present
invention, an optoelectronic device includes a bypass diode, a heat
spreader unit disposed above, and extending over, the bypass diode,
and a heat sink disposed above the heat spreader unit. In one
embodiment, the bypass diode is disposed in a recessed cavity under
the heat spreader unit. In accordance with another embodiment of
the present invention, an optoelectronic device includes a bypass
diode, a heat spreader unit disposed above, but not extending over,
the bypass diode, and a heat sink disposed above the heat spreader
unit. In one embodiment, the bypass diode is disposed in a
through-hole via disposed in the heat spreader unit.
* * * * *