A method characterized by the steps of positioning a plurality of uniformly dimensioned photovoltaic cells in registered relation with a plurality of openings formed in a planar tool is disclosed. The method allows acess to the P contact surface of each of the cells. The steps of the method are: (1) connecting the N contact surface of alternate cells to the P contact surface of the cells interposed therebetween, (2) removing therefrom residue of solder flux, (3) applying to the N contact surfaces of the cells a transparent adhesive, (4) placing a common transparent cover plate in engaged relation with the adhesive, (5) placing a film over the circular openings for hermetically sealing the openings, and (6) establishing a vacuum between the film and the cover plate

Dillard, P. A.

Fritz, W. M.

Lott, D. R.

English

NASA Technical Reports Server

United States Patent [I91 
Dillard et al. 
[54] METHOD OF FABRICATING A 
PHOTOVOLTAIC MODULE OF A 
SUBSTANTIALLY TRANSPARENT 
CONSTRUCTION 
[ 751 Inventors: Alan M. Lovelace, Acting 
Administrator of the National 
Aeronautics and Space 
Administration, with respect to an 
invention of Paul A. Dillard, 
Sunnyvale; Walter M. Fritz, 
Santa Clara; Dan R. Lott, San 
Jose, all of Calif. 
[ 731 Assignee: The United States of America, 
represented by the Administrator of 
the National Aeronautics and Space 
Administration, Washington, D.C. 
[21] Appl. No.: 928,133 
[22] Filed: Jul. 26, 1978 
[51] Int. ( 3 . 2  ........................ B32B 31/20; B25B 11/00 
[52] U.S. CI. .................................... 156/104; 156/278; 
156/285; 156/300; 156/303; 156/312 
[58] Field of Search ............... 156/299, 300, 303, 305, 
156/295, 312, 285, 104, 278 
~561 References Cited 
U.S. PATENT DOCUMENTS 
3,600,246 8/1971 Breen ................................... 156/299 
3,804,692 4/1974 Sly ........................................ 156/300 
D11. 4,184,903 
[45] Jan. 22, 1980 
3,963,556 6/1976 Patterson et al. ................ 156/285 X 
3,994,760 11/1976 Park ..................................... 156/104 
4,132,218 1/1979 Bennett ............................ 156/104 X 
Primary Examiner-Harold Ansher 
Attorney, Agent, or Firm-Monte F. Mott; John R. 
Manning; Wilfred Grifka 
[571 ABSTRACT 
A method characterized by the steps of positioning a 
plurality of uniformly dimensioned photovoltaic cells in 
registered relation with a plurality of openings formed 
in a planar tool for affording access to the P contact 
surface of each of the cells, connecting the N contact 
surface of alternate cells to the P contact surface of the 
cells interposed therebetween, removing therefrom 
residue of solder flux, applying to the N contact sur- 
faces of the cells a transparent adhesive, placing a com- 
mon transparent cover plate in engaged relation with 
the adhesive, placing a film over the circular openings 
for hermetically sealing the openings, and establishing a 
vacuum between the film and the cover plate for thus 
simultaneously forcing the cells into vacuum bonded 
relation with the cover plate. 
9 Claims, 17 Drawing Figures 
39\ (39' /34 
https://ntrs.nasa.gov/search.jsp?R=19800010276 2020-03-21T02:26:55+00:00Z
U.S. Patent ~ m .  22,1980 Sheet 1 of 3 4,184,903 
U.S. Patent ~ m .  zz,i980 Sheet 2 of 3 4,184,903 
U.S. Patent J~W. 22,1980 Sheet 3 of 3 
FIG.  12 14 
12 
20 40 
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FIG.  I3 
F I G .  /4 
FIG. I5 
22 
FIG. 16 
4,184,903 
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4,184,903 
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METHOD OF FABRICATING A PHOTOVOLTAIC 
MODULE OF A SUBSTANTIALLY TRANSPARENT 
CONSTRUCTION 
ORIGIN O F  THE INVENTION 
The invention described herein was made in the per- 
formance of work under a NASA contract and is sub- 
ject to the provisions of Section 305 of the National 
Aeronautics and Space Act of 1958, Public Law 85-568 
(72 Stat. 435; 42 U.S.C. 2457). 
BACKGROUND OF THE INVENTION 
5 
1. Field of the Invention 
The invention generally relates to a method of fabri- 
cating photovoltaic modules, and more particularly to a 
method of fabricating a photovoltaic module substan- 
tially transparent to all energy not used by the cell to 
produce electricity whereby the overall efficiency of 20 
15 
the module is enhanced. 
2. Description of the Prior Art 
The prior art, of course, is replete with devices and 
techniques employed in the production of solar cells. 
Most photovoltaic modules have been designed with a 
view toward reduction in initial costs of materials. This, 
of course, results in penalties in performance, of effi- 
ciency as well as production costs. However, as pointed 
out in U.S. application Ser. No. 918,869, now aban- 
doned, it is possible to fabricate a photovoltaic module 
which is substantially transparent to substantially all 
solar energy not used to produce electricity. Because of 
such transparency, the temperature of the module is 
substantially minimized with an attendant increase in 
the overall efficiency of the module. For example, it has 
been found that where cell temperature has been re- 
duced because of module transparency, an improve- 
ment in electrical output has been experienced. 
Additionally, as can be appreciated by those familiar 
with the fabrication of photovoltaic modules, it is 
highly desirable to fabricate photovoltaic or solar mod- 
ules employing techniques which readily can be 
adapted for a production-line assembly thereof. 
It is, therefore, the general purpose of the instant 
invention to provide an improved method of fabricating 
an improved photovoltaic module, said method being 
adaptable for use in production-line assembly opera- 
tions. 
OBJECTS AND SUMMARY OF THE 
INVENTION 
It is, therefore, an object of the instant invention to 
provide an improved method of fabricating photovol- 
taic modules. 
Another object is to provide a method of fabricating 
a photovoltaic module including a plurality of photo- 
voltaic cells substantially transparent to all solar energy 
not used by the cells in the production of photovoltaic 
electricity. 
These and other objects and advantages are achieved 
25 
30 
35 
40 
45 
50 
55 
60 
through the practice of a method wherein a plurality of 
uniformly dimensioned photovoltaic cells are posi- 
tioned relative to a tool, characterized by a plurality of 
openings disposed in uniform positional relationship for 65 
affording access to the P contact of each of the cells, 
and thereafter vacuum bonding the cells to a transpar- 
ent cover plate, as will become more readily apparent 
Y 
by reference to the following description and claims in 
light of the accompanying drawings. 
DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a perspective view of a photovoltaic module 
fabricated employing the method of the instant inven- 
tion. 
FIG. 2 is a perspective view of a planar tool em- 
ployed fabricating the module shown in FIG. 1. 
FIGS. 3 through 11 are perspective views illustrating 
sequential steps performed in a method resulting in the 
photovoltaic module shown in FIG. 1. 
FIG. 12 is a fragmented, sectional view of the module 
shown in FIG. 1. 
FIG. 13 is a fragmented top plan view of a portion of 
the partially completed module shown in FIG. 3, but on 
an enlarged scale. 
FIG. 14 is a fragmented bottom plan view of a por- 
tion of the partially completed module shown in FIG. 6, 
but also on an enlarged scale. 
FIG. 15 is a fragmented, cross sectional view of the 
module in its completed form. 
FIG. 16 is a cross sectional view of a vacuum fixture 
employed in the fabrication of the module. 
FIG. 17 is a diagrammatic view illustrating a circuit 
for the module. 
DESCRIPTION O F  THE PREFERRED 
EMBODIMENT 
Referring now to the drawings with more particular- 
ity, wherein like reference characters designate like or 
corresponding parts throughout the several views, 
there is shown in FIG. 1 a photovoltaic module, gener- 
ally designated 10, fabricated in accordance with a 
method embodying the principles of the instant inven- 
tion. 
As shown in FIG. 1, the module 10 includes a plural- 
ity of individual solar cells 12 of circular configurations 
and of common diameters. The solar cells 12, as shown, 
comprise N on P cells having an N surface 14, FIG. 13, 
and a P surface 16, FIG. 14. To the N surface 14 of each 
of the cells 12 there is connected N contacts 18, of 
known design, while to the P surface 16 there is con- 
nected P contacts 20, FIG. 14. Since photovoltaic cells 
are well known, a more detailed description thereof is 
omitted in the interest of brevity. 
In fabricating the module 10, a plurality of solar cells 
12 are connected in series. To achieve this, the cells are 
positioned on the surface of a tool designated 22, FIG. 
2. The tool 22 is provided with a plurality of uniformly 
spaced, circular openings 24 about which there is ar- 
ranged stop pins 26, of uniform height. The purpose of 
these pins is to support the solar cells 12 in a registered 
relationship with the openings 24 and to maintain sepa- 
ration of the cells and adhesive from the cover plate 
during initial vacuum application, therefore, it will be 
appreciated that the pins 26 are similarly positioned 
about each of the openings. 
As illustrated in FIG. 3, the solar cells 12 are depos- 
ited on the tool 22 in registration with the openings 24, 
and suitable interconnects 28 are positioned to be 
soldered to the N contacts 18 as well as to the P 
contacts 20. The interconnects 28 are now soldered to 
the N contacts 18 employing a suitable soldering gun 
29. The interconnects 28, as best illustrated ia E - S S .  13, 
14 and 15 are provided to connect the P contx t  of one 
cell 12 with the N contact of an adjacent cell 12. 
4,184,903 
3 4 
Following the soldering of the interconnect 21 to the In view of the foregoing, it should readily be appar- 
N contact, as shown in FIG. 4, the solder is removed <nt that the method which embodies the principles of 
through the use of a suitable cleaning gun 30. Subse- the instant invention provides a practical and economic 
quent to a removal of debris, such as solder flux and the method readily adaptable to assembly line production 
like, a tool cover 32, FIG. 5, comprising a planar mem- 5 techniques, whereby automation of fabrication of trans- 
ber is positioned over the N contact surfaces of the solar parent photovoltaic modules is faciliated. 
cells 12. The cover 32 serves to hold the cells 82 in place We claim: 
for facilitating an inversion of the cells 13, to an orienta- 8. In a method of fabricating a transparent photovol- 
tion as shown in FIG. 6. With the cover 32 in place, taic module wherein a plurality of electrically intercon- 
soldering Of the iIlterCOnneCtS 28 to the P Contacts 20 Of 10 nected solar cells are bonded to a rigid transparent 
the cells is initiated employing the gun 29. Of course, support panel, the step of: 
once the interconnects 28 have been soldered to the P depositing on one face of each solar cell o fa  plurality 
contacts 20 of the solar cells 12, solder flux is removed of electrically interconnected solar cells a film of 
therefrom employing the cleaning gun 30. It is to be substantially transparent adhesive, positioning said 
understood that the opposite surface contacts for the 15 one face of each cell in contiguous relation with a 
cells 12, at the opposite ends of the thus connected common surface of a substantially transparent sup- 
array, are provided with leads, not shown, necessary to port panel and simultaneously vacuum-bonding 
said plurality of cells to the panel. establish a series circuit as depicted in FIG. 17. 
The tool 22 now is inverted for a second time and %. A method of fabricating a photovol~aic module, 
thereafter the ‘Over 32 is removed‘ To the ‘Ontact 2o including a plurality of photovoltaic cells substantially 
surface for each Of the is a Of transparent to substantially all solar energy not used by clear adhesive 33, as illustrated in FIG. 8. A suitable the cells to produce electricity energy comprising the adhesive applicator A is employed for this purpose. steps of: Following the deposit of the adhesive on the N surface A. forming a uniform, planar array of a plurality of of the solar cells 112, a glass cover plate 34 is deposited 25 
in contiguous relation with the cells, as the cells are 
cover plate 34 preferably comprises a sheet of glass 
highly pervious to solar radiation. Such is obtainable 
ASG and comprises a low-iron, high transparent glass 
sheet. 
Next, the cells 12 are vacuum bonded to the cover 
plate 34. To effect a vacuum bonding of the cells 12 to 
the cover glass a thin film 36 of substantially impervious 35 
material, such as a film of PVC, now is deposited on the 3* The method Of claim wherein the step of forming 
surface of the tool 22, opposite the surface on which the array the Of: 
rests the cells 12, FIGS. BO and 11, forming an assembly Positioning a Plurality of uniformly dimensioned solar 
37. Thereafter, the resulting assembly designated 37 is cells in an abutted relationship and electrically 
inserted into a vacuum fixture 38 and supported as 40 interconnecting the Cells in a common circuit. 
shown in FIG. 16. ?’he fixture includes an impervious 4. The method of claim 3 wherein the step of position- 
cover 39 forming vacuum chamber 39‘ and 3yt, FIG. ing the solar Cells in a uniform array COmpriSeS the step 
16, adapted to be connected with separate Sources of of arranging the Plurality of cells in a coplanar relation 
vacuum, not shown. on a common surface of a panel having defined therein 
It should be apparent that the chamber 39’ includes an 45 a Plurality of uniformly spaced openings for affording 
hermetic seal established about the periphery of the aCCeSS to the opposite faces Of each Of said cells Of said 
assembly 37 whereby a vacuum may, as desired, be array. 
established between the assembly 37 and the cover 39. 5. The method of claim 3 wherein the step of electri- 
A vacuum now is introduced into the chambers 39‘ and Cally interconnecting the cells in a common circuit 
39“, about the solar cells 12, as they are supported in the 50 includes the steps of electricd1Y interconnecting the 
fixture 38. Then the diaphragm 36 is subjected to atmo- plurality of cells in circuit series. 
spheric pressure by venting chamber 39” while main- 6.  The method of claim 5 wherein the first face of 
taining 39” under vacuum. Atmospheric pressure acting each solar cell of the plurality is provided with an N 
against the diaphragm 36 forces the solar cells 12 into a contact and the opposite face thereof is provided with a 
vacuum bonding engagement with the cover plate 34. 55 P contact, and the step of interconnecting the cells in a 
The vacuum is held until the adhesive spreads uni- common circuit includes the step of attaching an inter- 
formly, whereupon the assembly 37 is removed from connect to the N contact of one cell of the array and to 
the fixture 38 and the diaphragm 36 and tool 22 are now the P contact of an adjacent cell of the array. 
separated. 7. The method of claim 5 wherein the step of vacuum- 
The cover plate 34 having the solar cells mounted 60 bonding the first face of each cell of the plurality of cells 
thereon now is placed in a suitable structural frame 
member 40 and inverted preparatory to receiving on the A. placing a film in occluding relation with the circu- 
surface of the solar cells 12 a layer 42 of transparent lar openings; 
adhesive. The layer 42 is now permitted to cure. Upon B. placing the cover plate in supported relation with 
completion of the curing process of the layer 42 of 65 the first face of each of the cells of the plurality to 
adhesive, the module 110 is ready for operation simply form an assembly; 
by making necessary circuit connections employing the C .  evacuating the assembly by applying vacuum to 
leads aforementioned, but not shown. both sides of the film; and 
interconnected solar cells; 
adhesives on a first face of each of the cells of the 
plurality; 
each of the plurality of cells to a common, substan- 
tially transparent cover plate comprising a support 
panel for the module; and 
depositing on the opposite face of each of the cells 
an 
supported on the tool 22, as indicated in FIG. 9. The ’’ depositing a quantity Of substantially transparent 
from the Sunadex Corporation under the designation 30 ‘* simultaneously vacuum-bonding Ihe face Of 
layer Of transparent adhesive. 
to the cover plate includes the steps of: 
4,184,903 
5 6 
D. introducing atmospheric pressure to the film while 
maintaining vacuum between the f i b  and the 
cover, for thus establishing a pressure differential 
across said film, whereby the cells are forceably 
pressed against said plate in response to ap- 
plied atmospheric pressure for thus vacuum-bond- 
ing the cells to the cover plate. 
8. The method of claim 7 further comprising the steps 
of relieving the vacuum and depositing thereon an en- 
capsulating cover layer of transparent adhesive. 
9. A method of fabricating a substantially transparent 
solar module comprising the steps of: 
A. positioning a plurality of uniformly dimensioned 
tionship with the pins for affording access to the P 
contact surface of each of the cells; 
B. connecting to the N contact surface of alternate 
cells the P contact surface of the cells interposed 
therebetween and removing therefrom the residue 
of solder flux; 
C. applying to the N contact surface of each cell a 
transparent adhesive; 
D. placing a common transparent cover plate in en- 
gaged relation with the adhesive; 
E. placing a diaphragm film over said cell openings; 
and 
photovo]taic cells of circular configurations F. establishing a vacuum between the film and the 
against a plurality of alignment pins provided in a 15 cover plate for simultaneously forcing the cells into 
planar tool characterized by a plurality of circular vacuum-bonded relation with the cover plate. 
cells openings disposed in uniform positional rela- * * * * *  
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Method of fabricating a photovoltaic module of a substantially transparent construction

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