A photovoltaic cell array consisting of parallel columns of silicon filaments is described. Each fiber is doped to produce an inner region of one polarity type and an outer region of an opposite polarity type to thereby form a continuous radial semi conductor junction. Spaced rows of electrical contacts alternately connect to the inner and outer regions to provide a plurality of electrical outputs which may be combined in parallel or in series

Eliason, J. T.

English

NASA Technical Reports Server

United States Patent WI 
Fletcher et al. 
1 ;I I I 3,984,256 
[451 Oct. 5, 1976 
[541 PHOTOVOLTAIC CELL ARRAY 
[761 Inventors: James C. Fletcher, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of; Jon T. Eliason, 
Huntsville, Ala. 
I221 Filed: Apr. 25; 1975 
[ 2 1 1 Appl. No.: 571,458 
1521 U.S. CI ...................................... 136/89; 29/572 
15 1 1 Int. CI .2 .......................................... HOlL 31/04 
1581 Field of Search .......................... 136/89; 357/30 
1561 References Cited 
UNITED STATES PATENTS 
2,402,662 6/1946 Oh1 ....................................... 136/89 
3.069,487 12/1962 Strother ................................ 136/89 
3.1 34.006 VI964 Henker ................................. 136/8Y 
3.1 7 1 ,068 Denkewalter et al ............. 136/89 X 2/1965 
3,206,832 9/1Y65 Strother ............................ 136189 X 
3,453.352 1/196Y Goundry ............................... 264193 
3,483,038 12/1Y69 Hui et a1 ............................... 136189 
Primary Examiner-John H. Mack 
Assistant Examiner-Aaron Weisstuch 
Attorney, Agent, or Firm-L. D. Wofford, Jr.; G .  J. 
Porter; John R. Manning 
1571 ABSTRACT 
A photovoltaic cell array consisting of parallel col- 
umns of silicon filaments, each being doped to pro- 
duce an inner region of one polarity type and an outer 
region of an opposite polarity type to thereby form a 
continuous radial semi-conductor junction. Spaced 
rows of electrical contacts alternately connect to thc 
inner and outer regions to provide a plurality of elec- 
trical outputs which may be combined in parallel or in 
series. 
6 Claims, 4 Drawing Figures 
24 
https://ntrs.nasa.gov/search.jsp?R=19770003692 2020-03-20T07:11:24+00:00Z
U.S. Patent oct. 5,1976 3,984,256 
LL 
3,984,256 
PHOTOVOLTAIC CELL ARRAY 
ORIGIN OF 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). 
2 
and the outer portion doped P-type instead of the 
above manner, chosen for illustration. The P doping is 
conveniently achieved by means of boron, and the N 
doping is achieved by means of phosphorus. A portion 
5 of the N-type layer is removed at spaced points, as for 
example by etching, to expose P material regions 16. 
An ohmic contact is then made to the P material region 
by P contact member 18, as by diffusing bonding or 
welding. 
N contact member 20 is welded to filament 10 at a 10 
spacing typically of 0.020 to 0.200 inch from the near- 
est contact member 18 to thereby provide one photo- 
voltaic cell unit with an output available between a 
contact member 18 and contalct member 20. U.S. Pat. 
ticularly to a matrix connected arrangement of such 1s No. 3,453,352 generally describes the method of con- 
cells and electrical output leads. struction of lengths of small cross section semi-conduc- 
2. General Description of the Prior Art tor material. 
The use of photovoltaic cells for the production of As shown in FIG. 1, the photocell units thus con- 
power is clearly in its infancy. While the general princi- nected are connected in parallel, with contact members 
ples are well known and have been for many years, the 20 18 being connected to P bus 22 and N contact mem- 
fact remains that there is still not available an economi- bers 20 connected to N bus 24. The structure is sup- 
cal form of photovoltaic device capable of competi- ported by insulating fibers 26, which enable the con- 
tively providing power for household or industrial use. struction of large area arrays consisting of series and 
The difficulty has been that thousands or hundreds of parallel electrical interconnected units of the above 
thousands of cells are necessary to produce sufficient 2s type, as represented by solar ccll blanket 28, shown in 
power, and the cost per unit has simply been prohibi- FIG. 3. By this technique, photlovoltaic cell densities of 
tive. 100 to 1,000 per square inch may be achieved. 
It is, accordingly, the object and purpose of this in- In operation, array 28 would be positioned so that 
vention to overcome this handicap and to enable the radiation 32 from the sun would strike the underside 34 
production in a single unitary structure of an almost 30 of the array, and each filament would produce multiple 
limitless number of photovoltaic cells at a small frac- outputs to buses 22 and 24. 
tion of the cost of manufacture heretofore experienced. FIG. 4 illustrates an alternate form of the invention 
wherein instead of there being radially formed junc- 
tions in the filaments of silicon, filament 36 is formed SUMMARY OF THE INVENTION 
In accordance with the invention, a photovoltaic ccll 35 with alternately doped P and N regions 38 and 40 along 
array is constructed of a combination of parallel col- the length of each filament. In such case, ohmic con- 
umns of P and N doped semi-conductor fibers and nections 42 and 44 are made to electrical output 
parallel rows of positive and negative electrical contact contact members 46 and 48 which may be made by 
members extending across and making contact with the surface welding of the contact members to each fila- 
respective P and N doped regions of the semi conduc- 40 ment 36. 
tor fiber columns. There is thus formed an array of From the foregoing, it will be appreciated that this 
photovoltaic cells and electrical outputs from the cells invention provides a solution to the problem of the high 
may be combined in series or parallel arrangements by costs of making solar cells, by weaving or otherwise 
appropriate connection to the contact members to positioning in a parallel, planar fashion filaments made 
provide a desired voltage-current output. 45 of doped silicon fibers with diffused radial or axial 
BACKGROUND OF THE INVENTION 
1.  Field of the Invention 
This invention relates to photovoltaic cells, and par- 
BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a pictoral view of an embodiment of the 
invention. 
FIG. 2 is an enlarged pictoral view of a portion of 
FIG. 1 illustrating certain details of construction. 
FIG. 3 is a schematic illustration of the arrangement 
of the components of the invention in the form of a 
fiber blanket. 
FIG. 4 is a pictoral view and alternate embodiment of 
the invention. 
DETAILED DESCRIPTION OF THE DRAWINGS 
Referring initially to FIGS. 1 and 2, the present in- 
vention contemplates the construction of photovoltaic 
units from filaments 10 of silicon having a diameter 
typically of 0.001 to 0.010 inch. Each filament 10 is 
initially doped to produce a P-type conductivity inter- 
nal region 12, and therafter an opposite conductivity 
type doping is applied, as by diffusion, to the outer 
surface 14 of the filament to produce an N-type con- 
ductivity layer. It will be apparent to those skilled in the 
art that the body of the filament may be doped N-type 
junctions. Each solar cell unit may be connected in 
series with others by means of interconnection wires or 
attached wire mesh screens. Cells may be made larger 
or smaller by making the grid electrodes in different 
50 ways, “weaving” suitable wires among the silicon fila- 
ments to act as buses, and by varying the dimension of 
the structure. The silicon filamlents are flexible and of 
high strength, hence can be wound on drums for stor- 
age in either filament or “blanket” form. Because of 
55 the high strength of and small size of the fiber, an array 
will provide a high redundancy factor. By using resis- 
tance heating, or lasers for heating, or RF induction 
heating, the formation of arrays in flexible blanket form 
can be automated. Individual c’ells may be electrically 
60 isolated in the blanket through the use of fibers woven 
in the flanket (as shown) or by means of insulating 
coatings or by the relative high resistance inherent 
along the length of a silicon filament. Because of the 
small diameter of a filament, and with localized laser 
65 processing and heating, the time of contact between a 
hot filament and any supporting structure, such as a 
processing fixture, can be quite effectively reduced 
with a consequent minimization of contamination. 
I 
3,984,256 
3 4 
Where junctions are exposed by virtue of the removal 
of material, they would be subsequently treated to 
prevent exposure by a technique usually referred to as 
passivation. 
internal doped region of one polarity and an outer 
doped region of an opposite polarity. 
5. A photovoltaic cell array comprising: 
a plurality of elongated, spaced filaments, each fila- 
ment comprising a semi-conductor material having 
impurities fused therein to form a diffused radial 
P-N junction wherein the interior region of each 
said filament is of one polarity and the outer region 
of each said filament is of an opposite polarity, a 
along each said filament, thereby exposing said 
interior region; 
a first set of spaced contact members, said members 
overlying said filaments, and each said lead being 
an ohmic electrical contact with a row of said ex- 
posed inner regions of said plurality of filaments; 
a second set of spaced contact members overlying 
said filaments and disposed intermediate first set of 
contact members, each of said second set of 
with a row of said outer regions of said filaments; 
5 What is claimed is: 
1. A photovoltaic cell array comprising: 
a plurality of elongated, spaced filaments of semi- 
conductor material, each filament being doped to 
a first plurality of spaced rows of electrical conduc- 
tors overlying said semi-conductor filaments, and 
each row being in electriclal contact with one 
polarity region of each said filament; 
a second plurality of spaced rows of electrical con- 15 
ductors overlying said filaments and disposed inter- 
mediate to said first-named row and being in elec- 
trical contact with opposite polarity regions of said 
filaments; and 
have 'paced regions Of Opposite polarity 10 portion of surface being removed at spaced points 
a first polarity current collecting means connected to 20 contact IMXtIbers being in chmic electrica1 contact 
said first plurality of electrical conductors, and -.-A 
aliu second current collectipg means connected to said 
second plurality of electrical conductors. 
2. A photovoltaic cell array as set forth-in claim 1 is 
a first current collector bus connected to said first set 
of contact members, and a second current collect- 
ing bus connected to said second set of contact 
members, whereby the power output of said array wherein said semiconductor material is silicon. 
3. A photovoltaic cell array as set forth in claim 2 
wherein the doping of a said filament is axially spaced 
to provide alternate P and N regions along the filament. 
4. a photovoltaic cell array as set forth in claim 2 
wherein the doping is radially spaced to provide an 
is available from said current collector buses. 
6. A photovqltaic cell array as set forth in claim § 
wherein said interior region is of a P polarity and said 
30 outer region is of an N polarity. * * * * *  
35 
40 
45 
50 
55 
60 
65 


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