JPH02213173A - Condensing-type solar cell - Google Patents

Abstract

PURPOSE:To enable incidence of light on both the surface and back sides of a semiconductor piece for generation of electricity and thereby to obtain a cell of a simple structure being approximate to a flat plate by a method wherein a light falling outside a region wherein the semiconductor piece exists is reflected by a reflecting film and further made to fall on the back of the semiconductor piece. CONSTITUTION:A condensing-type solar cell which condenses optically a light falling on a prescribed light irradiation plane and converts it into an electric energy is provided with a semiconductor piece 1 whereon a semiconductor junction which can receive the light from both the surface facing the light irradiation side and the back thereof and generate electricity is formed, and with a reflecting film 14 which is positioned on the back side of said semiconductor piece 1 and disposed with a gap from the semiconductor piece 1, and the reflecting film 14 is so disposed as to reflect the light entering from a region B of the light irradiation plane wherein the semiconductor piece 1 is not present and to make it fall on the back of the semiconductor piece 1. For instance, the reflecting film 14, which is a thin film of aluminum or the like, is formed on an indent 13 provided in the surface of a substrate 12 formed of a transparent material and shaped in a flat plate, on the opposite side of the main surface thereof whereon the semiconductor piece 1 is bonded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention focuses sunlight irradiated onto an area larger than the surface area of the active part of a solar cell, that is, a semiconductor piece that performs power generation, and converts it into electrical energy. This invention relates to a concentrating solar cell that converts light.

[Prior Art] A conventional concentrating solar cell has a three-dimensional structure as shown in FIGS. 9 and 10 (for example, rProc
eedings of 17thIEEE Ph
otovoltaic 5specialists
Conf,, May 1984, Or Iando,
p814-p819J).

A semiconductor piece 1 constituting the active part of the solar cell, that is, the part that performs power generation function, is adhered and supported on a support plate 2. As shown in FIG. 11(a), this semiconductor piece 1 has a conductive film on the upper and lower surfaces of a semiconductor P-N junction where a P-type silicon layer 8 and an N-type silicon layer 9 are joined.
0a and 10b are formed. conductive film 10a,
The conductive film 10a of the conductive film 10b on the side where sunlight is incident is made of a transparent conductive film. 119 As shown in (a), when sunlight enters from the side of the P-type silicon layer 8,
A voltage is generated between the conductive films 10a and 10b, and when a load is connected between them, a current flows. This is due to the following phenomenon. First, when light hits the P-type silicon layer 8, electron-hole pairs are created on the surface, and each diffuses to the junction between the P-type silicon layer 8 and the N-type 2932 layer 9. Electrons and holes that reach the junction become N due to the electrolysis there.
On the u silicon layer 9 side, holes are accelerated toward the p-type silicon layer 8 side. As a result, electrons are accumulated in the conductive film 10b serving as an electrode, and holes are accumulated in the conductive film 10a, resulting in an electromotive force.

The Fresnel lens 3 made of plastic shown in FIG. 9 has a flat plate shape and is capable of condensing parallel light rays in the same way as a convex lens without significantly changing the wall thickness, thereby directing sunlight onto the semiconductor chip 1. Focuses the light to a specified magnification. The distance between the Fresnel lens 3 and the support plate 2 is kept constant by a support 4, and they are connected as one body.

Each of the above elements is combined and integrated to constitute one concentrating solar cell unit 5. The light incident on the Fresnel lens 3 is focused on the surface of the semiconductor piece 1. The condensing magnification in this case is determined by the focal length of the Fresnel lens 3 and the length of the pillar 4. In other words, the length of the pillar 4 is determined so that the ratio of the area of the Fresnel lens 3 to the area of the semiconductor piece 1 corresponds to the light condensing magnification. As shown in FIG. 10, a plurality of such concentrating solar cell units 5 are integrated and combined on a plane to form a structure 7, which is installed in the solar tracking device 6. When adjusting the sun tracking device t6 manually, a manual lever 6a is used.

[Problems to be Solved by the Invention] In the conventional concentrating solar cell, the surface of the conductive film 10b, which is the back side of the semiconductor piece 1, is adhesively fixed on the support plate 2, and sunlight is exposed only from the surface conductive film 10a side. Electricity is generated by inputting light.

Therefore, in order to efficiently convert incident light into electrical energy, the positional relationship between the Fresnel lens 3 and the semiconductor piece 1 must be determined so that all the light focused by the Fresnel lens 3 is incident on the surface of the semiconductor piece 1. There must be.

As a result, in order to obtain a predetermined light condensing magnification, the distance between the Fresnel lens 3 and the semiconductor piece 1, that is, the length of the support column 4, becomes longer, and the entire concentrating solar cell unit 5 becomes a large one that expands three-dimensionally. Become. If a plurality of these structures are integrated into a planar structure to form the structure 7, the structure 7 will be heavy and thick, and the shape will be susceptible to wind pressure, etc., which is not preferable.

From the above, the structure of the conventional concentrating solar cell has the problem that the solar tracking device 6 must be a robust device, making the device as a whole expensive.

In order to solve the above-mentioned problems, the present invention provides a concentrating solar panel with a simple structure similar to a flat plate by making it possible to generate electricity by inputting light from both the front and back surfaces of the semiconductor chip 1. The purpose is to obtain batteries.

[Means to solve the problem]

In order to solve the above problems, the concentrating solar cell of the present invention is a concentrating solar cell that optically condenses light incident on a predetermined light irradiation surface and converts it into electrical energy, A semiconductor piece is fixed on a surface and has a semiconductor junction formed thereon that can generate power by receiving light from both the front surface facing the light irradiation side and the back surface thereof, and the and a reflective film spaced apart from the semiconductor piece. The reflective film is characterized in that it is arranged so as to reflect light incident from a region of the light irradiation surface where the semiconductor piece is not present, and to make the light incident on the back surface of the semiconductor piece.

[Function] According to the present invention, light incident on the outside of the region where the semiconductor piece, which is the active part, is present is reflected by the metal thin film deposited on the inclined surface of the transparent material, and is further made incident on the back surface of the semiconductor piece. This allows light to enter from both the surface of the semiconductor chip facing sunlight and the back surface thereof. This makes it possible to focus incident light on an area several times the surface area of the semiconductor piece and convert it into electrical energy.

[Example] An example of the present invention will be described below with reference to FIGS. 1 and 2. The concentrating solar cell of this example has the following configuration. For example, a P-N junction solar cell piece (hereinafter referred to as a "semiconductor piece") 1 made of single crystal Si has a thickness of about 100 μm.
m, and is bonded to one main surface of a flat support 12 made of a transparent material such as glass using a transparent adhesive material such as epoxy resin. As shown in the cross section of FIG. 11(b), the semiconductor chip 1 used in this example has almost the same structure as the conventional one shown in FIG. Conductivity 11! [10c is also formed of a transparent conductive film like the conductive film 10a. With this configuration, electrons and holes are generated not only by the light that has passed through the conductive film 10a and entered the P-type silicon layer 8, but also by the light that has passed through the conductive film 10c and entered the N-type silicon layer 9. pair and P
An electric field is generated at the -N junction, and the conductive films 10a, 10
An electromotive force is generated between c. As a result, the light-receiving area of the semiconductor piece 1 is doubled compared to the conventional one, so that when the same intensity of light is irradiated, the amount of light received is also doubled. Furthermore, by joining two conventional semiconductor pieces 1 shown in FIG. 11(a) vertically symmetrically at the conductive film 10b,
It can receive light from both the front side and the back side, and can be used in this embodiment. In addition, the semiconductor piece 1 of the support body 12
In the recess 13 provided on the surface opposite to the main surface to which the reflection film is bonded, a thin film of silver or aluminum formed by vacuum evaporation, for example, is applied. 114 is formed.

As shown by the solid arrow in the figure, sunlight hits the semiconductor piece 1.
The light enters from the main surface of the support 2 to which is adhered, and the light that enters from the area A enters the semiconductor piece 1, is absorbed by the active part, and contributes to power generation. Further, the light transmitted through the region B, which is the region where the semiconductor chip 1 is not present, is reflected by the reflective film 14 and enters the semiconductor chip 1 again, contributing to power generation. In region A, the semiconductor piece 1 and the reflective film 14 form parallel surfaces separated by a distance g. In area B, the support 12 has a recess 13 characterized by an angle θ and a depth d, and the light incident in area B is reflected by a reflective film 14 that is inclined by θ with respect to area A, and the semiconductor chip The light is incident on the back surface of 1. If this cross section is extended long in the direction perpendicular to the plane of the paper in the figure, then if the length of area A is a and the length of area B is b, then the condensing magnification R
is expressed by the following formula.

R-1+ 2 ... (1) 1+t
an2θ・tanθ tan-tanθ (2) 1=tan2θ (3) In the above formula (1), when θ-10°, R42, 9
, for θ-20°, R″F2. 5. θ-30°
In this case, it becomes R-2.0. Figure 1 is an example of the dimensions when the angle is θ-30°, and the glass thickness g is 4 m.
If m, then d is 2mm, A is 6.93rnm, and b is 3.
It becomes 46rnm. Figure 2 is a two-dimensional representation of each area in this example, where area A is a square with sides of 6.93 mm, area B is a rectangle of 6.93 x 3.46 mrn2,
Area C is a square with sides of 3.46 mm. In the diagonal cross section that includes area C, that is, the cross section that includes the two points shown in FIG. 2, the inclination angle corresponding to θ is 33.9'.
, d has a depth of 3.3 mm. In other words, the depth of the depression at two points in the figure is 3.3 mm.
Therefore, the surface of C has an angle of 33.9° with respect to the surface of A, and most of the light reflected at region C is incident on the back surface of semiconductor piece 1. Therefore, using the planar configuration shown in Figure 2, the total condensing magnification, that is, the ratio of the area of all regions to the area of region A, is
The area C is approximately 4 times larger in total.

FIG. 3 depicts the same planar configuration as in FIG. 2 for more periods, and can cover the entire plane by using the thick line as one unit.

According to the configuration of this embodiment, a light condensing magnification of about 4 times can be obtained, so it is suitable when using a relatively expensive and thin (10 Am to 200 tIm thick) semiconductor piece made of single crystal Si, GaAs, 1nP, etc. It is. Figure 4 shows:
The dimensions of a and b are the same as those shown in Fig. 3, but the areas on the left and right sides of area A are continuous in the horizontal direction.
In the vertical direction, the case is shown in which it spreads in a staggered manner. In this case, the light collection magnification is doubled. Furthermore, FIG. 5 shows a structure in which the cross section of FIG. 1 extends long in the direction perpendicular to the plane of the paper, and depending on the selection of θ, the condensing magnification changes according to equation (1).

Further, the thickness g of the support 12, the depth d of the depression 13, and the widths of the regions A and B also change according to equations (2), 5, and (3).

The structure of this embodiment as described above is particularly suitable for a solar cell using amorphous silicon in which the semiconductor piece 1 can be directly deposited on the support 12. Moreover, it goes without saying that any of the configurations shown in FIGS. 3 to 5 can be applied to any solar cell as long as light can be incident from the back surface.

Further, the support body 12 may be made of plastic, or may be made of a combination of glass and plastic. That is, as shown in FIG. 3, for example, a flat glass 12a and a transparent plastic member 12b are bonded together as a support 12 with a transparent adhesive, a recess 13 is formed in the transparent plastic member 12b, and a recess 13 is formed in the recess 13. Reflection [14] can be used.
Weight reduction can be achieved by increasing the proportion of plastic, which has a lower specific gravity than glass.

Further, the reflective film 14 that reflects the light incident on the region B toward the semiconductor chip 1 does not necessarily have to be a flat surface as shown in FIG. 1, but may be a curved surface as shown in FIG. 7 as an example. is also possible.

In each of the above embodiments, the support 12 is interposed between the semiconductor piece 1 and the reflective film 13, but there may be a space between the semiconductor piece 1 and the reflective film 13.
It is only necessary to provide some other support means for maintaining the two in a predetermined relative positional relationship.

The structure in which the concentrating solar cell in each of the above embodiments is formed into a device is schematically shown in FIG. That is, a large number of semiconductor pieces 1 (6×6 in the figure) are fixed to the upper surface of a flat plate-like support 12 in a matrix arranged vertically and horizontally, and then installed in the solar tracking device 6.

This solar tracking bag W6 is for keeping the surfaces of the support 12 and the semiconductor chip 1 perpendicular to the incident sunlight, and can be adjusted manually using the manual lever 6a.

Although the figure shows the semiconductor chip 1 exposed, in reality, in order to protect the surface of the semiconductor chip 1, the surface of all the semiconductor chips 1 is covered with one glass plate and transparent adhesive is applied. I am using something that is glued with an adhesive.

Further, in each of the above embodiments, cases are shown in which parallel light is incident on the main surface of the support 12 to which the semiconductor chip 1 is fixed, but it goes without saying that the concept of the present invention can be applied even if the light is not parallel. .

For example, it is also possible to apply the present invention to a case in which the light obtained by concentrating sunlight with a Fresnel lens is made incident on a wider area on the main surface of the support body 12 than the area where the semiconductor chip 1 is present. In this case, if the shape of the recess 13 on the back surface of the support body 12 is set so that the light incident from the area where the semiconductor chip 1 is not present is reflected toward the back surface of the semiconductor chip 1, and the reflective film 14 is formed, Even if the Fresnel lens 3 has the same focal length, the same light condensing magnification can be obtained at a shorter distance between the Fresnel lens 3 and the semiconductor piece 1 than in the conventional example shown in FIG.

[Effects of the Invention] As described above, according to the present invention, a semiconductor piece that generates power by receiving light incident from both the front and back sides is fixed on the entire surface of a transparent flat plate, and the semiconductor piece is Light incident from the non-contact area can be reflected by a reflective film formed in a recess provided on the back surface of the flat plate, and further made incident on the back surface of the semiconductor piece to generate power. Therefore, in combination with the light incident from the surface of the semiconductor piece, it is possible to obtain a concentrating solar cell that has a light collection magnification several times that of the case where the light is collected only from the surface of the semiconductor piece.

Furthermore, if the present invention is applied to a concentrating solar cell that condenses light using a Fresnel lens, for example, when obtaining the same light condensing magnification using a Fresnel lens with the same focal length, the distance between the Fresnel lens and the semiconductor piece can be increased. Can be made smaller. Therefore, the structure in which the concentrating solar cell units are integrated and connected on a plane becomes relatively thin, making it possible to reduce the weight and to reduce the influence of wind pressure.

As a result, the strength required for the solar tracking device will also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a concentrating solar cell according to an embodiment of the present invention, FIG. 2 is a plan view showing each region of the same embodiment, and FIG. 3 is a plan view of each region of the same embodiment. 4 and 5 are diagrams showing a modification of the planar configuration of each region when the cross section is as shown in FIG. 1. FIG. 6 is another embodiment of the present invention. FIG. 7 is a sectional view showing a concentrating solar cell according to another embodiment of the present invention, and FIG. 8 is a cross-sectional view showing a concentrating solar cell according to another embodiment of the present invention. FIG. Furthermore, Fig. 9 is a cross-sectional view showing the configuration of a conventional concentrating solar cell, and Fig. 10 is a diagram showing how a structure composed of nine units of a conventional concentrating solar cell is mounted on a sunlight tracking device. FIG. 11(a) is a schematic perspective view showing the structure of the semiconductor chip 1 in a conventional example, and FIG. 11(b) is a schematic perspective view of the structure of the semiconductor chip 1 used in each embodiment of the present invention. FIG. In the figure, 1 is a semiconductor piece, and 14 is a reflective film. Note that in each figure, the same numbers indicate the same or equivalent elements.

Claims (1)

[Scope of Claims] A concentrating solar cell that optically condenses light incident on a predetermined light irradiation surface and converts it into electrical energy, the solar cell being fixed on the light irradiation surface and arranged on the light irradiation side. a semiconductor piece on which a semiconductor junction is formed that can generate electricity by receiving light from both the facing surface and the back surface; a reflective film; the reflective film is arranged so as to reflect light incident from a region of the light irradiation surface where the semiconductor piece is not present and make it enter the back surface of the semiconductor piece. Concentrating solar cells.