Fabrication methods for matrices of solar cell submodule

Yasui, R. K.

English

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NATIONAL AERONAUTICS AND SPACE A D M I N I ~ ~ R A T ~ O N  
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REPLY TO 
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USI/Scientffic & Technical nfomation 
Attention: Miss Winnie M e  Morgan 
G P / O f f i c e  of AssiFtagt General Counsel for 
Patent Matters 
Annouicement of NASA-Owned 
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I n  accordance w i t h  the procedures agreed upon by Code  GP 
and Code  USI, the attached NASA-owned U. S. Patent is being 
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me follcwfng information is providedt 
U. S .  Patent No. .- t 3,493,437 
Government or  
Corporate Employee California Institute of Technology 
Supplementary Corporate 
Source (if applicable) Jet Propulsion Laboratory 
NASA Patent C a s e  No, 
NOTE - If  this  patent covers an invention made by a corporate 
employee of a NASA Contractor, the following is applfcables 
Pursuant t o  Section 305(a) of the National Aeronautics and 
Space A c t ,  the name of the Administrator of NASA appears on 
the first page of Ehe patent: however, the name of the actual  
inventor  (author) appears a t  the heading of Columra No. 1 of 
the Specification, following the words e e w i t h  respect to  
Yes No 
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Enc losure 
Copy of Patent arited &ova 
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(NASA CR OR TMX OR AD NUMBER) 
(CATEGORY) 
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https://ntrs.nasa.gov/search.jsp?R=19710001581 2020-03-17T02:35:34+00:00Z
3, 
Patented Feb. 3, 197 
3,493,437 
SOLAR CELL ~ ~ ~ M ~ ~ ~ L E  
6 
us. CI. 13-9 
10 
A multicell submodule is provided, in which a first bus- 
bar has portions thereof electrically connected to a first 
terminal of each of the cells in the submodule, with raised 
portions of the first busbar being present between the por- 
tions thereof which are in contact with the cell’s first 
terminals. A second busbar, which is electrically con- 
nected to the second terminals of the various cells in the 
submodule, includes a plurality of tabs which extend from 2O 
the second busbar. These tabs are adapted to be connected 
to the raised portions of a first busbar of another sub- 
module in order to form a rnultisubmodule cell matrix. 
of with the tabs extending therefrom. Thus, after the cells 
forming each submodule are safely connected to the two 
busbars, the submodule includes the two bars as an inte- 
gral part thereof. 
The submodule may then be calibrated to determine its 
energy conversion characteristics. When the submodule is 
to form a part of a larger cell module, the tabs thereof are 
bent down over the raised portions of the undulative bat 
of an adjacent submodule to form a mechanical contact 
therebetween. The electrical contact is provided by elec- 
trical soldering. Howeber, since the soldering is done on 
the raised portions of the busbar, the heat produced dur- 
ing the soldering is small enough not to  affect the contact 
of the undulative busbar with the actual cell’s contacts. 
Thus, submodules may be conveniently matched and then 
interconnected without the danger that during the inter- 
connections any of the cells may be adversely affected 
and thereby effect the completed module. 
The novel features that are considered characteristic Of 
this invention are set forth with particularity in the ap- 
pended claims. The invention itself both as to its organi- 
zation and method of operation, as well as additioaal 
objects and advantages thereof, will best be understood 
from the following description when read in connection 
The invention described herein was made in the per- FIGURES l (a)  and l ( b )  are side and top views re- 
formance of work under a NASA contract and is subject spectively of the novel busbars used in the present in- 
to the provisions of Section 305 of the National Aero- vention; 
nautics and Space Act of 1958, Public Law 85-568 (72 FIGURES 2 ( a )  and 2 ( b )  are top and bottom views of 
Stat, 435; 42 USC 2457). 30 a solar cell; 
This invention relates to matrix construction and more FIGURE 3 is an isometric view of a solar submodule 
particularly to the construction of submodules and mod- constructed in accordance with the teachings of the inven- 
ules of cells such as solar cells. tion; and 
Different energy sensitive devices are extensively used FIGURE 4 is an isometric view of a solar module of 
to convert energy from one form to another, such as .for 35 the present invention. 
example solar sells used to convert light into electrical Attention is now directed to FIGURES l (a)  and 
current. Since the amount Of electrical energy produced l ( b )  which are side and top views of an undulative 
by one cell is quite small, they are arranged in matrices. busbar 11 and a tab incorporating busbar 12, respective- 
generally formed by arranging the cells in rows and ly. The busbars shown have been utilized in the actual 
columns. Each cell is interconnected by means of busbars 4 0  reduction of the invention to practice by forming a cell 
running along each row and column. The cell contacts submodule of commercially available cells, one of which 
are quite delicate and therefore extreme cafe must be ex- is shown in FIGURES 2 ( a )  and 2 ( b )  to which refer- 
ercised when connecting it to the busbars to Produce the ence is made herein. FIGURES 2(a)  and 2(6) are top 
matrix and in particular when replacing a defective fell and bottom views respectively of a solar cell 15. In re- 
in an already existing matrix. 45 ducing the invention to practice, the cell was of a silicon 
When a large cell matrix or module is desired, it has p on N type, with thre grids 16 connected to  a con- 
been the practice to first construct cell submodules which tact 18 formed of a P type conducting material to form 
after proper matching were combined to form the module. the p contact of the cell. P contact 18 is along one end of 
However, when connecting the submodules to one an- the cell while the entire bottom surface of the ceII is 
other such as by electrical soldering, the heat often ad- 60 covered with an N type conducting material 20 to form 
versely affected some of the already Connected cells, re- the N contact of the cell. 
sulting in a defective module. In accordance with the teachings of the present in- 
It is accordingly an object of the invention to provide a vention, cells 15 are interconnected by means of bus- 
new cell modular construction. bars 11 and 12 [FIGURES l (a)  and l ( h ) ] .  Undulative 
&other object is the provision of a simple arrangement 65 busbar 11 includes substantially fidt contact partions XIp 
whereby Cells are combined to form submodules which in between raised portions 1 l r .  Busbar 12 on the other 
are then interconnected to form an overall module with- hand comp&es a flat strip 12s having a plurality of 
out affecting any of the already connected cells. tabs bat extend therefrom. 
A further object is the provision of a new busbar ar- Referring to FlGURE 3 there is shown an isometric 
rangement for connecting cells to form a cell submodule. BO view of a cell submodule 25, constructed in accordance 
The arrangement lends itself to interconnecting cell sub- with the teaching9 of the invention. The submodule 
modules to form a matrix by electrical soldering of the comprises seven cells 15, although it i s  appreciated that 
various submodules without the heat generated during the any number of cells may used. As s e n ,  the cells 15 
electrical soldering affecting the already connected cells are arranged in parallel so that contacts 1-8 thereof are 
in the various submodules. 65 in a straight line. The undulative busbar 11 is aligned 
These and other objects of the invention are achieved with the contacts 18, with each flat portion 1fp being 
by arranging, within each submodule, cells in parallel and electrically connected, such as by soldering, to contact 18 
connecting one terminal of each cell near one end thereof of another cell. Busbar 11 is soldered that portions 
with an undulative busbar having raised portions between t l r  are raised from above the top of contacts 18 or 
the points of Contact Of the busbar with each of the cells. 70 the top surfaces of the cells. TO the N contacts 20 of 
A second busbar which includes a plurality of protrud- the various cells opposite the side where contacts 18 are 
ing tabs is connected to each cell near the other end there- located, is solder& the flat strip 12s af busbar 12, with 
25 with the accompanying drawings, in which: 
3,493,437 
3 
the tabs 1Et extending from the cells' ends. The busbar 
12 is soldered so that tabs 12t are aligned with respect to 
the raised portions Ilr of husbar 11. 
1%: two husbars mounted in parallel across the cells 
plnccd in p;trallel provide common P and N teiminals. 
Alw due to their thicknew, they also provide for a de- 
gree of mechanical strength and support for the other- 
wise sensitive cells. In addition, since busbar 11 is not 
soldered to the cells along its entire length but rather 
only along in flat portions Ilp, the raised portions 1 P r  
provide a measure of stress relief to further minimize 
stress forces from damaging the submodule. 
I n  addition, when the submodule 25 is to form part of 
a larger cell module, the raised portions serve as the 
means to which tabs, such as tabs 12t from a preceding 
submodule, are connected while the tabs 12t of sub- 
module 25 are connectable to the raised portions l l r  
of a succeeding submodule. The tabs are bendable over the 
raised portions so that they form a mechanical as well 
as an electrical bond therewith. When a permanent bond 
is desired, the tabs can be soldered to the raised por- 
tions. However, since the raised portions are not in con- 
tact with the cells' contacts 18, the soldering operation 
does not affect the cells. Any heat transmitted through 
bus 11 may be minimized by selecting the bus material 
to be of a low heat conductivity. Thus once a submodule 
is constructed and tested, it may be safely soldered to 
other submodules with a minimum of danger to the cells 
thereof from the subsequertt soldering operation. This is 
most significant, since each submodule may be xepa- 
rately constructed, testpd, and matched to other cell sub- 
modules. Then the ~ubmodiiles may be safely soldered 
together by soldering tabs of one submodule to raised 
portions of another submodule with all the soldering 
being done on the busbars a t  points removed from the 
cell contacts which are generally the most damage-prone 
parts of the cells. 
Referring to FIGURE 4, there is shown a cell module 
30 of three submodules 30a, 30b and 30c, each com- 
prising of six cells 15. As becomes apparent from FIG- 
URE 4, the tabs 12t of submodule 306 are bent or 
wrapped around the raised portions l l r  or submodule 
30c while the tabs 12t of submodule 3Qa are bent around 
raised portions 11r of 30b. Thus the three submodules 
are coupled to form module 30. After testing the module, 
the tabs may be soldered to  their respective raised por- 
tions to form a soldered joint or bond, the soldering not 
affecting adjacent cells since soldering is done away from 
their sensitive contacts. If during testing or thereafter 
a submodule is found to be faulty, it can be easily re- 
placed by unbending the tabs connecting the submodule 
to adjacent units and replacing it with a new unit. 
From the foregoing, it should be appreciated that by 
utilizing the modular construction herebefore described, 
each submodule may be separately constructed as an 
integral unit with all its related components or elements 
such as cover plates, light filters and the like. Then as 
an integral tested unit, it may be couplable by means of 
the busbar tabs and the busbar raised portions to other 
units to form a larger module or matrix. The use of such 
an arrangement greatly minimizes the danger that cells 
may be affected during the submodular interconnections. 
Thus the problem of producing large cell modules is 
areatlv simulified. In addition, since each submodule is 
4 
module with the necessary submodular interconnections 
not having any damaging affect on the sensitive cells. It 
is appreciated that those familiar with the art may make 
modifications ih the arrangements as shown without de- 
parting from the true spirit of the invention. Therefore, 
all such modificitticms and equivalents are deemed to fall 
within the scope of the invention as claimed in the ap- 
pended claims. 
What is claimed is: 
1. In a cell matrix comprising a plurality of sub- '' modules each submodule including a plurality of cells 
with each having first and second electrical terminals, the 
improvement comprising: 
a first busbar having portions thereof electrically con- 
nected to the first terminals of each of the cells in a 
submodule, said fitst busbar having raised portions 
between the points in contact with said first terminal; 
and 
a second busbar electrically couplable to  the second 
terminals of the cells in each submodule said second 
busbar including a plurality of tabs extending there- 
from whereby said tabs are aligned to be couplable 
to the raised portions of a first busbar of another 
submodule to electrically couple the two modules in 
series and thereby form a cell matrix therefrom. 
2. The cell matrix defined in claim 1 wherein said first 
busbar is characterized by low heat conducting properties 
to minimize the effect of coupling the tabs of a second 
busbar of another submodule to the raised portion thereof 
80 on the points of contact thereof with the first terminals 
of said cells. 
3. The cell matrix defined in claim 2 wherein the tabs 
of the second busbar of a first submodule are bendable 
over the raised portion of the first busbar o f  another 
35 submodule to mechanically be coupled thereto by encir- 
cling a portion thereof, whereby said submodules are 
mechanically coupled to one another. 
4. The cell matrix defined in claim 3 wherein each of 
said cells comprises a plurality of parallel grids and a P 
40 type conducting terminal perpendicular to  said grid across 
one end of said cell and an N type conducting material 
forming the rear surface of said cell, said first busbar 
being electrically coupled to the P type conducting ter- 
minal of each of said cells and the second busbar being 
4.5 coupled to the N type conducting rear surface of said cell. 
5. A cell modular construction comprising: 
a plurality of cells arranged in groups of parallel cells; 
a plurality of undulative busbars each being coupled 
to the parallel cells in another of said groups, said 
busbar having raised portions between the points of 
contact thereof with said cells; and 
a plurality of undulative busbars each being coupled 
to the cells in another group opposite the end where 
said undulative busbar is coupled thereto, said tabs 
being aligned with respect to said raised portions 
whereby the tabs of one submodule are couplable to  
the raised portions of the undulative busbar of an- 
other submodule to form a series of submodules. 
6. In combination with a plurality of cells each defining 
60 a flat surface having a plurality of parallel grids mounted 
on one side of said surface and a contact coupled to  said 
grids across one end of said surface, the arrangement 
comorisine: 
15 
20 
25 
50 
55 
an  undilative busbar having points thereof electrically 
coupled to the contacts across said one end of said 
cells, said busbar having raised portions between 
said points of contact; and 
a second busbar electrically coupled to  each of said 
said one ends, said second busbar having a plurality 
of tabs extending therefrom, said tabs being adapted 
to be coupled to raised portions of another undulative 
busbar coupled to another plurality of cells for form- 
ing a cell matrix therewith. 
Eonst;ucted- as an integral unit prior to being incor- 65 
porated in a larger matrix semi-automated soldering tech- 
niques may be employed for soldering the biisbars 11 
and 12 to each set of parallel cells which therafter may 
be covered with the necessary filters and cover plates. 
novel cell modular construction particularly adapted t o  
the formation of multicell modules, in which groups of 
cells are first interconnected t o  form complete cell sub- 
modules. Once each submodule is completed as a unit, 
it is couplable to other identical subunits to produce the 75 
There has accordingly &en shown and described a 70 cells at the Other side of the flat surfaces opposite 
3,493,437 
6 
7. The arrangement defined in claim 6 wherein at least References Cited 
type conducting materiaf, said first and second bars being 
electrically coupled to the P and N type conducting mate- 
rials respectively. 
A* 
M. J .  ANDREWS, Assistant Examiner 
JAMES E. W&3B 3,493,437 
MINISTRATOR OF THE NATIONAL. 
AERONAUTICS AND SPACE 
ADMINISTRATION 
SOLAR CELL SUBMODULE 
Filed April 20, 1966 
25  
G. 2 ( b )  FIG. 2 ( a )  FI 
I 
FIG. 
12t  
INVENTOR. 
R Q  
FIG. 


Solar cell submodule Patent

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