Substrate structures for integrated series connected photovoltaic arrays and process of manufacture of such arrays

A substrate structure for manufacturing series interconnected photovoltaic cells comprises repetitive sheets of electrically conductive polymer resin joined by first narrow strips of insulating material. A second narrow dividing strip of insulating material is positioned on the top surface of each electrically conductive sheet extending essentially parallel with but slightly displaced from the joining strips. The second strip divides the top surface of each conductive sheet into a connector area and a collector area. The connector area is positioned between the first and second insulating strips. After deposition of a thin film photovoltaic cell onto the collector area, series interconnection is made by establishing electrical communication between the top surface of the photovoltaic film and the connector area of an adjacent sheet. Electrodeposits on surface portions of the electrically conductive sheets assist in current distribution with minimum power losses.

BACKGROUND OF THE INVENTION 
Photovoltaic cells have developed according to two distinct methods. The 
initial operational cells employed a matrix of single crystal silicon 
appropriately doped to produce a planar p-n junction. An intrinsic 
electric field established at the p-n junction produces a voltage by 
directing photon produced holes and free electrons in opposite directions. 
Despite good conversion efficiencies and long-term reliability, widespread 
energy collection using single-crystal silicon cells is thwarted by the 
exceptionally high cost of single crystal silicon material. 
A second approach to produce photovoltaic cells is by depositing thin 
photovoltaic semiconductor films on a supporting substrate. Material 
requirements are minimized and technologies can be proposed for mass 
production. The thin film structures can be designed according to doped 
homojunction technology such as that involving silicon films, or can 
employ heterojunction approaches such as those using CdTe or chalcopyrite 
materials. 
Despite significant improvements in individual cell conversion efficiencies 
for both single crystal and thin film approaches, photovoltaic energy 
collection has been generally restricted to applications having low power 
requirements. One factor impeding development of bulk power systems is the 
problem of economically collecting the energy from an extensive collection 
surface. Photovoltaic cells can be described as high current, low voltage 
devices. Typically, individual cell voltage is less than one volt. The 
current component is a substantial characteristic of the power generated. 
Efficient energy collection from an expansive surface must minimize 
resistive losses associated with the high current characteristic. A way to 
minimize resistive losses is to reduce the size of individual cells and 
connect them in series. Thus, voltage is stepped through each cell while 
current and associated resistive losses are minimized. 
It is readily recognized that making effective, durable series connections 
among multiple small cells can be laborious, difficult,and expensive. In 
order to approach economical mass production of series connected arrays of 
individual cells, a number of factors must be considered in addition to 
the type of photovoltaic materials chosen. These include the substrate 
employed and the process envisioned. Since thin films can be deposited 
over expansive areas, thin film technologies offer additional 
opportunities for mass production of interconnected arrays compared to 
inherently small, discrete single crystal silicon cells. Thus a number of 
U.S. Patents have issued proposing designs and processes to achieve series 
interconnections among the thin film photovoltaic cells. Many of these 
technologies comprise deposition of photovoltaic thin films on glass 
substrates followed by scribing to form smaller area individual cells. 
Multiple steps then follow to electrically connect the individual cells in 
series array. Examples of these proposed processes are presented in U.S. 
Pat. Nos. 4,443,651, 4,724,011, and 4,769,086 to Swartz, Turner et al, and 
Tanner et al., respectively. While expanding the opportunities for mass 
production of interconnected cell arrays compared with single crystal 
silicon approaches, glass substrates must inherently be processed on an 
individual batch basis. 
More recently, developers have explored depositing wide area films using 
continuous roll-to-roll processing. This technology generally involves 
depositing thin films of photovoltaic material onto a continuously moving 
web. However, a challenge still remains regarding subdividing the 
expansive films into individual cells followed by interconnecting into a 
series connected array. U.S. Pat. No. 4,746,618 to Nath et al. teaches a 
design and process to achieve interconnected arrays using roll-to-roll 
processing of a web substrate such as thin stainless steel. The process 
includes multiple operations of cutting, selective deposition, and 
riveting. These operations, combined with the high cost of stainless steel 
sheet, add considerably to the final interconnected array cost. Similar 
concerns exist with the teachings of U.S. Pat. Nos. 4,965,655 to Grimmer 
et. al. and U.S. Pat. No. 4,697,041 to Okaniwa. These references teach 
processes requiring expensive laser scribing and interconnections achieved 
with laser heat staking. In addition, the two latter references teach a 
substrate of thin vacuum deposited metal back contact on films of 
relatively expensive polymers. The high electrical resistance and fragile 
nature of thin vacuum metallized layers significantly limits the 
permissible active area of the individual interconnected cells. 
Therefore, there remains a need for improved structures and processes to 
permit economical production of large area interconnected arrays of 
photovoltaic cells. 
In a somewhat removed segment of technology, a number of electrically 
conductive fillers have been used to produce electrically conductive 
thermoplastic materials. This technology generally involves mixing of the 
conductive filler into the thermoplastic prior to fabrication of the 
material into its final shape. Conductive fillers typically consist of 
high aspect ratio particles such as metal fibers, metal flakes, or highly 
structured carbon blacks, with the choice based on a number of 
cost/performance considerations. 
Electrically conductive plastics have been used as bulk thermoplastic 
compositions or formulated into paints. Their development has been spurred 
in large part by electromagnetic radiation shielding and static discharge 
requirements for plastic components used in the electronics industry. 
Other known applications include resistive heating fibers and battery 
components. 
In yet another separate technological segment, electroplating on plastic 
substrates has been employed to achieve decorative effects on items such 
as knobs, cosmetic closures, faucets, and automotive trim. ABS 
(acrylonitrile-butadiene-styrene) plastic dominates as the substrate of 
choice for most applications because of a blend of mechanical and process 
properties and ability to be uniformly etched. The overall plating process 
comprises many steps. First, the plastic substrate is chemically etched to 
microscopically roughen the surface. This is followed by depositing an 
initial metal layer by chemical reduction. This initial metal layer is 
normally copper or nickel of thickness typically one-half micrometer. The 
object is then electroplated with metals such as bright nickel and 
chromium to achieve the desired thickness and decorative effects. The 
process is very sensitive to processing variables used to fabricate the 
plastic substrate, limiting applications to carefully molded parts and 
designs. In addition, the many steps employing harsh chemicals make the 
process intrinsically costly and environmentally difficult. Finally, the 
sensitivity of ABS plastic to liquid hydrocarbons has prevented certain 
applications. The conventional technology for electroplating on plastic 
(etching, chemical reduction, electroplating) has been extensively 
documented and discussed in the public and commercial literature. See, for 
example, Saubestre, Transactions of the Institute of Metal Finishing, 
1969, Vol. 47., or Arcilesi et al., Products Finishing, March 1984. 
Many attempts have been made to simplify the process of electroplating on 
plastic substrates. Some involve special chemical techniques to produce an 
electrically conductive film on the surface. Typical examples of this 
approach are taught by U.S. Pat. No. 3,523,875 to Minklei, U.S. Pat. No. 
3,682,786 to Brown et. al., and U.S. Pat. No. 3,619,382 to Lupinski. The 
electrically conductive film produced was then electroplated. 
Another approach proposed to simplify electroplating of plastic substrates 
is incorporation of electrically conductive fillers into the resin to 
produce an electrically conductive plastic. The electrically conductive 
resin is then electroplated. Examples of this approach are the teachings 
of Adelman in U.S. Pat. No. 4,038,042 and Luch in U.S. Pat. No. 3,865,699. 
Adelman taught incorporation of conductive carbon black into a polymeric 
matrix to achieve electrical conductivity required for electroplating. The 
substrate was pre-etched to achieve adhesion of the subsequently 
electrodeposited metal. Luch taught incorporation of small amounts of 
sulfur into polymer-based compounds filled with conductive carbon black. 
The sulfur was shown to have two advantages. First, it participated in 
formation of a chemical bond between the polymer-based substrate and an 
initial Group VIII based metal electrodeposit. Second, the sulfur 
increased lateral growth of the Group VIII based metal electrodeposit over 
the surface of the substrate. 
Since the polymer-based compositions taught by Luch could be electroplated 
directly without any pretreatments, they could be accurately defined as 
directly electroplateable resins (DER). Directly electroplateable resins, 
(DER), are characterized by the following features: 
(a) having a polymer matrix; 
(b) presence of carbon black in amounts sufficient for the overall 
composition to have a an electrical volume resistivity of less than 1000 
ohm-cm., e.g., 100 ohm-cm., 10 ohm-cm., 1 ohm-cm.; 
(c) presence of sulfur (including any sulfur provided by sulfur donors) in 
amounts greater than about 0.1% by weight of the overall 
polymer-carbon-sulfur composition; and 
(d) presence of the polymer, carbon, and sulfur in said directly 
electroplateable composition of matter in cooperative amounts required to 
achieve direct, uniform, rapid,and adherent coverage of said composition 
of matter with an electrodeposited Group VIII -based metal or Group VIII 
metal-based alloy. 
The minimum workable level of carbon black required to achieve electrical 
resistivities less than 1000 ohm-cm. appears to be about 8 weight percent 
based on the weight of polymer plus carbon black. 
Polymers such as polyvinyls, polyolefins, polystyrenes, elastomers, 
polyamides, and polyesters are suitable for a DER matrix, the choice 
generally being dictated by the physical properties required. 
In order to eliminate ambiguity in terminology of the present specification 
and claims, the following definitions are supplied. 
"Metal-based" refers to a substance having metallic properties and being 
composed of two or more elements of which at least one is an elemental 
metal. 
"Polymer-based" refers to a substance composed, by volume, of 50 percent or 
more hydrocarbon polymer. 
"Group VIII-based" refers to a metal (including alloys) containing, by 
weight, 50% to 100% metal from Group VIII of the Periodic Table of 
Elements. 
It is important to note that electrical conductivity alone is insufficient 
to permit a plastic substrate to be directly electroplated. The plastic 
surface must be electrically conductive on a microscopic scale. For 
example, simply loading a small volume percentage of metal fibers may 
impart conductivity on a scale suitable for electromagnetic radiation 
shielding, but the fiber separation would likely prevent uniform direct 
electroplating. In addition, many conductive thermoplastic materials form 
a non-conductive surface skin during fabrication, effectively eliminating 
the surface conductivity required for direct electroplating. 
OBJECTS OF THE INVENTION 
An object of the present invention is to eliminate the deficiencies in the 
prior art. Another object of the present invention is to provide an 
improved substrate to achieve series interconnections among wide area thin 
film photovoltaic cells. Another object of the present invention is to 
provide improved interconnected photovoltaic arrays. A further object of 
the present invention is to provide an improved process whereby wide area 
series interconnected photovoltaic arrays can be economically mass 
produced by well-known techniques. 
Other objects and advantages will become apparent in light of the following 
description taken in conjunction with the drawings and embodiments. 
SUMMARY OF THE INVENTION 
A structure is provided comprising repetitive thin electrically conductive 
sheets held together by thin joining strips of insulating material. 
Additional thin dividing strips of insulating material are provided on the 
top surface of the electrically conductive sheets. The dividing strips 
extend essentially parallel to but are slightly displaced from the 
insulating joining strips. The top surface of each electrically conductive 
sheet consists of two portions. A first contact portion has a relatively 
small width and is positioned between the two slightly displaced strips of 
insulating material. The second collector area portion is of substantially 
wider extent than the first contact portion and is positioned on the 
opposite side of the insulating dividing strips. A portion of the surface 
of the electrically conductive sheets comprises a metal-based 
electrodeposit to facilitate current distribution while minimizing 
resistive power losses. To complete the interconnected photovoltaic array, 
an active thin film photovoltaic laminate is deposited on the top 
collector area surface of the substrate. Thereafter, series connections 
are completed by electrically connecting the top collector surface of each 
cell with the contact surface portion of the adjacent cell across the 
insulating joining strips. The latter electrical connecting can be simply 
accomplished by any of a number of selective deposition procedures. 
As will be shown, the substrate structure and integrated arrays of the 
invention can be produced by simple, well-known, and inexpensive mass 
production technologies using inexpensive common materials.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Reference will now be made in detail to the preferred embodiments of the 
invention, examples of which are illustrated in the accompanying drawings. 
A single unit of polymeric substrate for the series interconnected 
photovoltaic array is generally indicated by 10 as shown in FIGS. 1 and 2. 
Unit substrate 10 comprises electrically conductive polymer based sheet 
13, electrically insulating dividing strip 15 and electrically insulating 
joining portion 17. Electrically conductive sheet 13 has a top collector 
surface 18, top contact surface 19, and bottom surface 20. Sheet 13 is 
characterized by having a width X, length Y, and thickness Z as shown in 
FIG. 1 and 2. Dimensions X and Y are much larger than thickness Z. Typical 
dimensions for the structure are as follows: 
X-0.5 cm-15 cm 
Y-Greater than 0.20 cm 
Z-5 micrometers-500 micrometers 
Width X defines a first terminal edge 12 and a second terminal edge 14. 
Sheet 13 typically comprises material having bulk resistivity of less than 
1000 ohm-cm. Resistivities less than 1000-ohm-cm can be readily achieved 
by compounding well-known conductive fillers into a polymer matrix binder. 
Electrically insulating dividing strip 15 extends in the direction of 
length Y and separates the top surface of sheet 13 into two areas 18 and 
19. This special and electrical separation allows for selectivity in 
subsequent deposition of functional films. The material chosen for strip 
15 varies depending on desired overall function. For example, if strip 15 
is envisioned to remain as pad of the final interconnected array, strip 15 
would typically comprise a material capable of achieving good bonding to 
sheet 13. In this case, strip 15 may simply be an adhesive, a material 
bonded to surface 18 with an adhesive, a polymer compatible with that 
forming the matrix of sheet 13 at surface 18, or even mechanically bonded 
strips such as an embedded fiber. 
On the other hand, it may be desirable to remove a portion or all of strip 
15 material at some point during manufacture of the completed array. In 
this case, strip 15 may comprise a material which dissolves in a liquid 
which is not a solvent for the other array materials, or a material which 
is only weakly bonded to the sheet 13, enabling easy removal. 
In order to minimize shading resulting from strip 15, width S (FIG. 2) is 
kept small. Typical values for width S are 10-1000 micrometers. 
FIG. 3 shows one embodiment for joining the repetitive units 10 and 11 of 
starting substrate. Joining portion 17 comprises an insulating material 
having good adhesive or mechanical attachment to the electrically 
conductive sheets 13. Attachment of portion 17 to conductive sheets 13 is 
made close to or at terminal edges 12, 14 and extends in the direction of 
length Y. Such a structure can be achieved inexpensively and in high 
volume using thermoplastic extrusion of alternating portions 17-13-17-13 
etc. In this process, alternating dies form the alternating portions 
17-13- 17-13 etc. and the portions are quickly adhesively bonded while 
still in their molten state. Additional dies can be used to apply strip 
15. In order to maximize the photovoltaic surface area, width T of joining 
portion 17 is kept small. The minimum width T of joining portion 17 is 
normally dictated by the precision of the fabrication process for the 
substrate structure. Typical values for T are from 250-5000 micrometers. 
FIG. 4 illustrates an alternative way to join adjacent units 10 and 11. 
Prior to joining of units 10 and 11, insulating portions 22 and 23 are 
bonded to opposite edges of sheet 13a of unit 10. Similarly, insulating 
portion 24 is attached to sheet 13b of unit 11. Units 10 and 11 are joined 
by welding or adhesive bonding of portions 23 and 24. 
FIG. 5 illustrates yet another alternative design for joining adjacent 
units 10 and 11. Thin insulating strip 26 is attached at surface areas 27 
and 28 of adjacent units 10 and 11 respectively. Attachment at surfaces 27 
and 28 can be mechanical or adhesive in nature. Strip 26 is advantageously 
a compound of a material selected to impart good mechanical strength and 
dimensional stability to the final interconnected array. For example, 
polymers heavily loaded with glass fibers would be good candidates for 
strip 26. 
FIG. 6 illustrates an embodiment in which the conductive sheet 13 is 
composed of multiple layers in laminated form. Three distinct conductive 
layers, 30, 31, and 32 form the composite conductive sheet 13. The 
invention contemplates using multiple layers for manipulating the 
functional, mechanical, or fabrication characteristics of the array. 
A number of factors must be considered when choosing the laminated 
structure illustrated by FIG. 6. Normally the bottom surface 20 presented 
by layer 32 is chosen to be electroplateable for reasons presented later. 
The laminated layer must be bonded with sufficient integrity to avoid 
excessive resistive power losses at the interfacial surfaces between 
layers. Finally, while the actual intrinsic resistivities of the 
individual layers may differ among themselves, no layer should 
significantly resist electrical current flow. 
The structures depicted by FIGS. 1 to 6 can be achieved using thermoplastic 
materials and processing such as extrusion and thermal adhesive bonding. 
This attribute is a primary advantage of the invention in that high 
volume, inexpensive fabrication techniques are employed to produce the 
starting polymeric substrate. 
FIGS. 7 through 9 show alternative constructions of individual units at an 
intermediate stage in the manufacture of the integrated photovoltaic 
array. FIG. 7 shows a metal-based electrodeposit 35 adherent to bottom 
surface 20 of conductive sheet 13. Surfaces 18 and 19 have been masked or 
otherwise prevented from being coated with electrodeposit. The 
electroplated metal adherent to the bottom surface of the conductive sheet 
13 is an important feature of the present invention. Resistivities for 
typical conductive plastics can be orders of magnitude greater than 
metals. Since the thickness "Z" of the conductive sheet is small, power 
losses from current transport over distance "Z" will be small despite the 
relatively high resistivity of the conductive resin layer. However, the 
width "X" of the individual units is relatively large in comparison to 
"Z". Current transport exclusively through the conductive polymer in the 
"X" direction would involve significant resistive power losses. 
Electrodeposition of the bottom surface of the conductive sheet supplies a 
mechanically robust, highly conductive current distribution mechanism to 
allow a more expansive top collector surface 18. 
An alternative to electrodeposit 35 would be to employ extremely high 
loadings of conductive filler in conductive sheet 13. High filler loadings 
are generally costly and negatively impact the mechanical properties and 
processing characteristics of polymers. However, using laminate structures 
such as illustrated in FIG. 6, high filler loadings could be employed in 
one of the resin layers with the remaining layer chosen for processing and 
mechanical characteristics. 
FIG. 8 shows metal-based electrodeposits 36 and 37 adherent to surfaces 20 
and 19 respectively. FIG. 9 shows metal-based electrodeposits 38, 39, and 
40 adherent to surfaces 20, 19, and 18, respectively. 
A broad variety of metal-based electrodeposits and electrochemical 
processes can be considered for the substrate of the present invention. 
Selectivity is readily achieved through masking or otherwise isolating the 
surface from the electrochemical solution. It is noted that because of the 
selective characteristic achievable with electrodeposition, the 
electrodeposits adherent to surfaces 20, 19, and 18 in FIGS. 7-9 can 
differ among themselves to achieve desired effects. For example, using the 
embodiment of FIG. 9, electrodeposit 38 may comprise copper for excellent 
conductivity and solderability while electrodeposit 39 may comprise a 
metal such as zinc which could be chromated to enhance adhesion of a 
subsequently applied film. Further, the exterior surface of electrodeposit 
40 would be material compatible with a subsequently applied photovoltaic 
film. 
It is further noted that the electrodeposits 35-40 of FIGS. 7-9 may consist 
of a single electrodeposited layer or may be a laminated structure of 
sequentially deposited layers. 
Many of the embodiments of the present invention comprise metal-based 
electrodeposits adherent to portions of the top or bottom surfaces of the 
electrically conductive polymer-based sheets. In these embodiments it is 
often advantageous to employ a directly electroplateable resin (DER) at 
the surface of the electrically conductive polymer sheet intended to be 
electroplated. DERs provide adequate electrical conductivity for the 
application as well as ensuring rapid lateral growth of adherent 
electrodeposit over the expansive surface envisioned. 
Turning now to FIGS. 10 and 11, an alternative embodiment for the starting 
polymer-based substrate is generally indicated by arrow 50. Embodiment 50 
comprises adjacent units 52 and 54. Units 52 and 54 form two of any 
desired number of units connected in similar fashion. Units 52 and 54 
comprise electrically conductive polymer-based sheets 56, electrically 
insulating dividing strips 58, and electrically insulating joining 
portions 60. Sheets 56 have three distinct surface portions 62, 64, and 66 
as best shown in FIG. 11. Top contact surfaces 64 are positioned between 
dividing and joining strip portions 58 and 60, respectively. Contact 
surfaces 64 and bottom surfaces 66 are capable of being electroplated with 
an adherent metal-based electrodeposit. Top collector surface 62 defines 
the area to be used to eventually deposit the photovoltaic cell. 
Electroplating of surface 62 is optional, as will be explained below. 
Holes 68 through sheet 56 are positioned respectively along the length Y of 
embodiment 50 to allow communication between surfaces 64 and 66 of units 
52 and 54. Holes 68 can be readily and precisely formed by mechanical 
punching or laser drilling. 
Having started with the embodiment of FIGS. 10 and 11, FIG. 12 illustrates 
a further stage in the manufacturing of the integrated series connected 
array. As shown in FIG. 12, a metal-based electrodeposit 70 has been 
applied to surfaces 64 and 66. Continuous electrodeposit communication is 
achieved from top contact surface 64 to bottom surface 66 by way of the 
electrodeposit 70 extending through holes 68. The electrically conductive 
sides 71 of holes 68 permit the through-hole electrodeposition. 
One skilled in the art readily recognizes that the conductivity associated 
with the metal electrodeposit is orders of magnitude greater than can be 
achieved with electrically conducting polymer sheets 56. Forcing all the 
photogenerated current to traverse the relatively restricted 
cross-sectional area defined by surface 64 could lead to significant 
resistive losses if the conductive polymer were the sole conductive 
medium. The through-hole electroplating avoids these resistive losses and 
permits the width "u" (FIG. 12) of surface 64 to be minimized. 
Electrodeposit 72 is shown in FIG. 12 adherent to surface 62. As will be 
explained below, electrodeposit 72 is optional. However, if electrodeposit 
72 is employed as shown in FIG. 12, it is not required to be the same or 
equivalent to electrodeposit 70. Electrodeposit 72 should be chosen to 
have good ohmic compatibility with the subsequently applied photovoltaic 
films as will be shown. 
FIGS. 13 through 16 suggest a form of the final integrated series connected 
photovoltaic array resulting from further processing of the embodiment of 
FIG. 12. Semiconductor layers 86 and 84 are deposited onto electrodeposit 
72 to form photovoltaic junction 88. Conductive, optically transparent 
window electrode 82 covers semiconductor layer 84. Electrically conductive 
collector grid fingers 80 are deposited onto electrode 82. 
It will be noted by those skilled in the art that the unique substrate 
structure taught in the embodiments of FIGS. 1-12 is suitable for use with 
a multiplicity of thin film photovoltaic cells. The exact nature and 
composition of the films 84, 86 and junction 88 in FIGS. 13 through 16 can 
be chosen in consideration of other criteria such as environmental 
stability and cell efficiency. However, it is noted that certain 
photovoltaic semiconductor films that can be electroplated, such as copper 
indium diselenide or cadmium telluride, may be uniquely suitable for the 
substrate of the present invention. Furthermore, composition and processes 
for forming top electrode 82 and collector grid 80 are well known in the 
an and do not form the subject matter of the present invention. 
Additional embodiments of the present invention are illustrated in FIGS. 17 
through 20. In FIGS. 17 and 18, 96 represents an insulating joining 
portion, similar to 17 and 60 of previous embodiments. 92 indicates the 
insulating dividing strip. Electrodeposit 94 is adherent to bottom surface 
93 and top contact surface 97. Electrically conductive polymer sheet 90 
comprises electroplateable bottom surface 93 and top collector surface 95. 
Surface 95 comprises a polymer matrix functioning as a binder for an 
electrically conductive filler. Suitable dopants are incorporated into the 
conductive polymer forming surface 95. The dopants participate in 
formation of a subsequently grown, adherent semiconductor thin film. 
One possible construction is shown in FIG. 18. In FIG. 18, thin 
semiconductor film 98 is a reaction product of a dopant present at surface 
95 of conductive polymer sheet 90 and additional species brought into 
contact with the surface. Contact with the additional species may be 
brought about by immersion in either liquid or vapor, and the reaction may 
be electrochemical and entirely chemical in nature. Photovoltaic junction 
104 is formed between the electrically conductive polymer base 90 and the 
semiconductor film 98. Transparent top window electrode 100 and collector 
grid 102 are subsequently applied to complete the integrated photovoltaic 
array. 
An example of the embodiment of FIG. 18 was prepared as follows. A thin 
piece of directly electroplateable plastic (DER) containing conductive 
carbon black, dissolved sulfur, and polypropylene matrix was chosen to 
constitute conductive sheet 90. This thin piece of directly 
electroplateable plastic was placed in an aqueous solution of nickel salt 
at a low cathodic potential of approximately 0.1 volt. An adherent uniform 
thin film of semiconductor, identified as nickel sulfide, formed over the 
surface. A potential photovoltaic junction was thus formed between the 
directly electroplateable polymer and the cathodically grown sulfide 
semiconductor. Similar semiconductor film growth was observed using copper 
containing electrolytes. 
FIGS. 19 and 20 illustrate a further embodiment produced using a reactive 
dopant to grow an adherent semiconductor film onto the surface of an 
electrically conductive polymer. In FIGS. 19 and 20, semiconductor layer 
110 is grown using the reactive dopant technology described in conjunction 
with FIG. 18. A suitable complementary semiconductor layer 112 is 
subsequently applied to form photovoltaic junction 114. Electrically 
conductive transparent top electrode 100 and collector grid 102 are than 
applied to complete the interconnected array. 
The reactive doping techniques taught in conjunction with FIGS. 17 through 
20 offer an inexpensive, simple method for forming adherent photoactive 
semiconductor films onto a fully series connected integrated array. 
FIG. 21 illustrates yet another embodiment of the substrate structure of 
the invention. Here surface 128 of electrically conductive polymer sheet 
122 is electroplateable to permit electrodeposition of adherent 
metal-based electrodeposit 120. Joining strips of insulating material 124 
allow selective electrodeposition of metal-based layers 120. After 
electrodeposition of metal-based layers 120, insulating dividing strips 
126 are applied to the surface of layers 120. Dividing strips 126 
facilitate selective deposition of photovoltaic semiconductor laminate 118 
and window collector electrode 116. It is to be understood that, while not 
shown, laminate 118 comprises at least two semiconductor layers forming 
the photovoltaic junction. Similarly, electrode 116 may comprise 
transparent window and grid structures as shown in previous embodiments. 
Although the present invention has been described in conjunction with 
preferred embodiments, it is to be understood that modifications, 
alternatives and equivalents may be included without departing from the 
spirit and scope of the inventions, as those skilled in the art will 
readily understand. Such modifications, alternatives and equivalents are 
considered to be within the purview and scope of the invention and 
appended claims.