An improved solar cell module for use in terrestrial environments is disclosed. It is characterized by: (1) an internally reflective plate having a planar surface of incidence and an opposed textured surface (2) a plurality of uniformly spaced silicon solar cells having the active surfaces thereof bonded to portions of the textured surface, and (3) a layer of diffusely reflective matter applied to the textured surface in surrounding relation with the solar cells for reflecting solar energy. The solar energy then strikes the surface of incidence at such angles as to be internally re-reflected and caused to progress toward the active surfaces of the solar cells, whereby concentration of incident flux on the solar cell is achieved without increased module depth

Shepard, N. F., Jr.

English

NASA Technical Reports Server

United States Patent [191 11 11 4,162,928 
Shepard, Jr. [45] Jul. 31, 1979 
[54] SOLAR CELL MODULE 
[76] Inventor: Robert A. Fkwch, Administrator of 
the National Aeronautics and Space 
Administration, with respect to an 
invention of Ned F. Shepard, Jr., 
King of Prussia, Pa. 
[21] Appl. No.: 946,994 
[22] Filed: Sep. 29,1978 
[51] 
[52] 
[561 References Cited 
Int. CI.2 ............................................. HOlL 31/04 
U.S. Cl. ................................................ l36/89 PC 
[58] Field of Search .................................... 136/89 PC 
U.S. PATENT DOCUMENTS 
3,487,223 12/1969 St. John ............................... 250/216 
3,973,994 8/1976 Redfield ................................. 136/89 
4,116,718 9/1978 Yerkes et al. ................... 136/89 PC 
Primary Examiner-Aaron Weisstuch 
Attorney, Agent, or Firm-Monte F. Mott; John R. 
Manning; Paul F. McCaul 
An improved solar cell module for use in terrestrial 
environments, characterized by an internally reflective 
plate having a planar surface of incidence and an op- 
posed textured surface, a plurality of uniformly spaced 
silicon solar cells having the active surfaces thereof 
bonded to portions of the textured surface, and a layer 
of diffusely reflective matter applied to the textured 
surface in surrounding relation with the solar cells for 
reflecting solar energy to strike the surface of incidence 
at such angles as to be internally re-reflected and caused 
to progress toward the active surfaces of the solar cells, 
whereby concentration of incident flux on the solar cell 
is achieved without increased module depth. 
PI ABSTRACT 
1 Claim, 3 Drawing Figures 
https://ntrs.nasa.gov/search.jsp?R=19790023582 2020-03-20T19:30:52+00:00Z
U.S. Patent Jul. 31, 1979 4,162,928 
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4,162,928 
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OBJECTS AND SUMMARY OF THE 
INVENTION SOLAR CELL MODULE 
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 USC 2457). 
BACKGROUND OF THE INVENTION 
It is an object of the instant invention to provide an 
It is another object to provide in with a 
planar silicon solar cell module a zero-depth concentra- 
tor. 
It is another object to provide an improved solar cell 
10 module characterized by a transparent cover plate hav- 
ing a coated textured surface for establishing internal 
re-reflection of solar flux whereby solar energy is con- 
centrated on the active surface of solar cells bonded to 
the textured surfam 
These together with other objects and advantages are 
achieved through the use Of an reflective 
transparent cover plate for a solar cell module, charac- 
terized by a planar surface of incidence and a diffusively 
20 con solar cell bonded at its active surface to a portion of 
2. Description of the Prior Art the textured surface, whereby incident solar flux strik- 
Photovoltaic devices have long been employed for ing the surface of incidence is re-reflected internally of 
converting solar energy to electrical energy. T O  en- the cover plate until incident upon the active surface of 
hance the efficiency of such devices various schemes, the solar cell, as will hereinafter become more readily 
techniques and devices have been proposed and em- 25 apparent by reference to the following description and 
ployed for directing solar radiation to strike the active claims in light of the accompanying drawings. 
5 improved solar cell module. 
1. Field of the Invention 
The invention generally relates to a solar cell module 
for terrestrial use and more particularly to a concentra- 15 
tor for a solar cell module adapted to employ repeated 
internal reflection for effectively concentrating solar 
module. 
energy Onto the active surfaces Of Of the reflective textured surface and having at least one sili- 
DESCRIPTION OF THE DRAWINGS surfaces of semi-conductive devices, often referred to as 
solar cells. For example, U.S. Pat. No. 3,973,994 dis- 
material backed by a transparent substrate. The side of 30 cell affixed to the reflectively coated textured surface of 
a transparent cover plate comprising a zero-depth solar 
voltaic concentrator embodying the principles of the the substrate opposite the active layer is formed in a 
sawtooth configuration and is reflectively coated so instant invention. 
that unabsorbed radiation is reflected back to the active PIG. 2 is a fragmented, c ross~sec~on~ view taken 
layer at an angle resulting in total internal reflection. 35 generally along line 2-2 schematically illustrating a 
Consequently, incident radiation is caused to Pass progression of solar flux to the active surface of the cell 
through the solar cell for a finite number of times until depicted in FIG. 2. 
it is absorbed by the active layer. The teachings of this FIG. 3 is a fragmented, top plan view of a solar cell 
patent are incorporated herein by reference thereto. module employing the solar cell depicted in FIG. 1. 
DESCRIPTION OF THE PREFERRED 
through which light is focused onto a photo-electric EMBODIMENT 
element. The surface of the screen disposed toward the 
element is covered by a reflective surface between the with more particular- ity, wherein like reference characters designate like or 
45 corresponding parts throughout the several views, slots and repeatedly reflects solar radiation until sub- 
U.S. Pat. No. 2,001,672 discloses a light sensitive cell ule which embodies the principles of the instant inven- 
in which light passing through and not absorbed by an tion. 
active layer thereof is reflected back to the layer by a As shown, the module, not designated, includes a 
reflecting surface. 50 silicon solar cell 10 mounted on a flux concentrator 12. 
US. Pat. Nos. 3,179,861 and 4,055,761 were discov- The details of the solar cell 10, of course, form no spe- 
ered in the course of a search, however, the teachings cific part of the instant invention, therefore, an in-depth 
thereof are not deemed to be more pertinent than the description of the solar cell 10 is omitted in the interest 
disclosures of the patents aforediscussed. of brevity. However, it is to be understood that the solar 
AS can be appreciated by those familiar with the 55 Cell 10 COmpriSeS a photovoltaic device Of Well known 
design and operation of solar cell modules, devices design. The Cell includes an active surface 14, FIG. 2, to 
having a capability of concentrating solar flux on the which is attached contacts 16, FIG. 1, and a back sur- 
active surface of a planar solar cell tend to be bulky, face to which is connected contacts 18. The contacts are affued to the cell 10 in a conventional manner and, of 
60 course, serve to connect the cell 10 to adjacent cells complex, and in many instances impractical when em- 
provided for the module, all in a manner well under- ployed in an operational environment. 
vention to provide in combination with a solar cell an of solar cell modules. H ~ ~ ~ ~ ,  it is to be understood the 
improved concentrator having a capability of achieving cells 10 are of known design and are interconnected in 
significant concentration of incident Solar flux for Sig- 65 a known manner for purposes of converting solar flux to 
nificantly enhancing short-circuit current for the cell, electrical energy. 
without resorting to a use of ancillary concentration Turning again to FIG. 2, it can be seen that the con- 
devices which tend to increase module depth. centrator 12 comprises a plate 20 formed of a highly 
closes a photovoltaic device having thin layem of active k a fragmented, top Plan view of a single solar 
U.S. Pat. No. 2,888,007 discloses a screen having slots 40 
Referring now to the 
stantially ' Of it has been absorbed by the there is shown in FIG. 1 a fragment o fa  solar cell mod- 
It is therefore the general purpose Of the instant in- stood by those familiar with the design and fabrication 
4,162,928 
3 4 
transparent material. One such material is available as centrator 12 serves to trap incident solar radiation 
ASG Sunadex glass. The plate 20, as best illustrated in which exits the concentrator, after repeated internal 
FIG. 2, includes a relatively flat and smooth surface 22, reflection to fall, on the active surface of the cell 18. 
herein referred to as a surface of incidence for solar flux. In view of the foregoing, it should be apparent that 
That is to say9 the surface 22 comprises the surface of 5 the concentrator 12 is particularly adapted to effec- 
the concentrator on which solar energy falls and tively concentrate otherwise wasted solar flux onto the 
through which solar energy is admitted to the concen- active surface of solar ccells of the module for thus 
trator. enhancing the electrical power output from the module, 
The surface of the plate 20, opposite the surface of without resorting to the use of awriliary concentration 
incidence 22, comprises a textured surface designated 10 devices which tend to increase module depth. 
24. The textured surface 24, in Practice, is deliberately Moreover, since solar cells constitute the bulk of the 
embossed to provide a regu1ar pattern Of uniform inden- costs for terrestrial modules, it should be apparent that 
tations. To this surface there is bonded a uniform array the overall cost per unit of electrical power output can 
Of are bonded to the plate 2o be reduced through the use of the instant invention due 
25 Of transparent adhesive’ such as l5 to the fact that the cells are sparsely concentrated for 
Saflex PT-lOy for is coated thus making extensive use of less expensive glass, in lieu by a layer 26 of diffusely reflective material such as 
RTv ll. Hence, there is provided between the cells of heavy concentrations of silicon solar cells, to achieve 
a desired electrical output. a substantially white surface. The purpose of the white 
surface of the layer 26 is to establish internal reflection 20 
of solar energy within the plate 20 for thus causing the 
angles of incidence greater than the critical angle there- 
for, whereby the solar energy is progressively reflected 
internally of the plate 20 until it is permitted to pass 25 
from the plate 20 to strike the active surface 14 of a solar 
cell 10. uniformly configured indentations; 
The critical angle, of course, can readily be computed 
according to Snell’s law, as more fully discussed in the 
aforementioned U.S. Pat. No. 3,913,994. 
It suffices to understand that the solar flux reflected 
from the textured surface of the plate 20 is reflected 
back and forth between the textured surface 24 and the 
surface 22 until the rays of flux exit the plate 20 to strike 
the active surface 14 of the solar cell 10. 
As shown in FIG. 3, the solar cells 10 are attached to 
the concentrator 12 with voids, or interspaces, desig- 
nated 30, located between the individual cells 10 being 
backed by the reflective layers 26. Thus the layer 26 
surrounds each of the cells 10. Consequently, the con- 40 
lo’ The 
a 
The surface 24 
What is claimed is: 
An improved 
having a pair of opposed surfaces including a sub- 
stantially smooth planar surface of incidence for 
accepting incident and a uniformly 
textured surface characterized by a plurality of 
B. a plurality Of silicon solar cells adhesively bonded 
at the active surfaces thereof to mutually spaced 
portions of said textured surface and defining 
therebetween interspaces; and 
c. means comprising a layer of diffusely reflective 
material deposited on said textured surface in the 
interspaces defined between said cells for internally 
reflecting solar energy to strike said surface of 
incidence at such angles as.to be internally re- 
reflected, whereby the energy is caused to progress 
toward the active surfaces of the solar cells of said 
plurality. 
comprising: 
rays thereof to strike the surface of incidence 22 at A. an reflective* transparent cover plate 
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