JPS6311789B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to devices for converting solar energy into electricity, and more particularly to semiconductor photovoltage generators that can be advantageously used in solar power plant designs.

BACKGROUND OF THE INVENTION Semiconductor photovoltage generators are known which consist of a series of electrically interconnected photovoltage converters. Each converter is made as a plate of p-n junction semiconductor material;
The junction has a rectifying barrier function that separates the base region of the first conductivity type from the opposite region of the second conductivity type.

The photovoltage converters are interconnected by metal current collection contacts connected to the base and reverse regions. Current collecting contacts connected to the opposite areas projecting onto the illuminated surface of the semiconductor photovoltage generator are arranged in a comb-like manner.

Their total area occupies approximately 10% of the inverse area surface of the photovoltage converter. The current collection contact connected to the base area is made as a thin layer occupying the entire rear area of the photovoltage converter.

Generators of this design have only one photoactive surface. Due to the relatively high value of the resistance spread in the opposite region, the series power loss reduces the efficiency of the photovoltaic converter illuminated by focused sunlight. However, if the gaps between the current collecting contacts are made narrower, while their width is increased, they shade the illuminated surface of the semiconductor photovoltage generator to a very large extent. The area of the photoactive surface of the generator is thus reduced, the power generated per unit area of the generator becomes smaller, and the efficiency of the device is reduced.

Such generators are difficult and time-consuming to manufacture because each element is manufactured individually and then these elements are assembled one after the other into a device.

However, there are semiconductor photovoltage generators that are easier to manufacture and have higher efficiency with a high degree of light focusing. They are made as a unitary structure of a plurality of photovoltage converters with pn junctions supporting metal current collecting contacts on their sides. Such photovoltaic converters are made as microparallelepipeds integrated in alignment with current collecting contacts along both sides.
The side surfaces are tilted at an angle with respect to the photoactive surface of the generator so that the abutting ends of the pn junctions reach the photoactive surface.

Such generators are characterized by a higher voltage per unit area of the photoactive surface and a current that varies linearly with the radiation rate in the range from 0 to 10 ⁴ W/cm ² .

(Problem to be Solved by the Invention) However, the sensitivity of the photoactive surface of this type of generation to incident light is sufficiently high only within the area where the p-n junction reaches its surface, but is highly non-uniform. As such, such generators suffer from significant power losses caused by minority carrier surface recombination effects and are relatively inefficient. It should also be noted that the lowest efficiency is obtained when the incident energy is distributed non-uniformly over the surface of the semiconductor photovoltage generator. This non-uniformity is very often observed in the energy distribution within the focus of optical focusing.

An object of the present invention is to improve the efficiency of a semiconductor photovoltage generator when the energy distribution of incident light is non-uniform and when the optical power is highly focused.

Another object of the invention is to reduce the amount of labor required to manufacture semiconductor photovoltage generators.

SUMMARY OF THE INVENTION The essence of the invention comprises a plurality of photovoltage converters connected in series by current collecting contacts along both sides to obtain a unitary structure, each converter having a base and With a p-n junction between opposite regions, according to the invention, the photoactive surface is made as a stepped structure, the area of each step being inversely proportional to the power of the incident light, while the width of each step is is approximately equal to or less than the diffusion length of the minority carriers in the base region.

The problem of increasing the efficiency of the photoactive surface and the light sensitivity of the generator is solved by providing additional current collecting contacts along the periphery of each stage.

The area of the photoactive surface and the photoresistance of the generator are increased by creating transverse parallel grooves on the surface of the stage, the spacing between the ridges of adjacent grooves is smaller than the diffusion distance of the minority carriers in the base region, while the p−n The joints follow the contours of the stages.

In order to improve the sensitivity of the photoactive surface and the photoresistance of the generator, the thickness of the base region in the photovoltage converter of the photoactive surface can be made much smaller than the diffusion length of the minority carriers in the base region. preferable.

It is also preferred that the photovoltaic converters are offset from each other in the rectifying plane to obtain the stepped structure.

It is often advantageous to use an arrangement in which the incident light velocity is rotated by an angle to each other about an axis transverse to the rectifying surface so as to obtain the stepped structure, while the power in the beam has a concentric distribution. Equipped with a photovoltaic converter.

If the photovoltaic converter is made as a tilted parallelepiped, it is preferred that the edges of the steps have an acute shape, while their surfaces are provided with a mirror coating.

It is often an advantageous arrangement for the photovoltaic converters to be made as analogs of decreasing dimensions arranged one after the other in order to obtain the stepped structure.

Preferably, the similar shape is represented by a regular polygon, a disk or a ring.

The essence of the invention also lies in a method for manufacturing a semiconductor photovoltage generator, in which metallized semiconductor plates with p-n junctions are assembled into piles, interconnected by soldering, and at the same time to push out excess solder. In a method that is compressed and cut into separate alignments at an angle to the plane of the plate, according to the invention it also comprises heating the alignment until the solder begins to melt, at which point the alignment elements form a stepped structure. The metal coating is then removed from the surface of the stage obtained in this way by an etching method.

(Example) Examples of the present invention will be described below with reference to the drawings.

The semiconductor photovoltage generator comprises photo-voltage converters 1 made as inclined parallelepipeds (FIGS. 1 and 2) connected in series and arranged to form a unitary structure. Each light-to-voltage converter 1 of the generator comprises a pn junction located in the base region 3 and in the inverse region 4. In the base region 3 either a homomorphic p-p ⁺ or n-n ⁺ junction 5 is arranged. p
-n junction 2 and homojunction 5 are placed in close proximity to a photoactive surface 6 that receives a beam 7 of incident light. The photoactive surfaces 6 are arranged in a stepped structure. Each photovoltaic converter 1 is provided with a current collection contact 8 attached to the opposite area and a current collection contact 9 attached to the base area 3.

The width "a" of the base of stage 10, whose vertices form angle α, is approximately equal to or less than the diffusion distance of the minority carriers of base region 3. The area of each stage 10 is inversely proportional to the power of the incident light 7 received by each photovoltaic converter 1. The area of the stage 10 is thus smaller (in terms of width "a") than that outside the generator in the central part of the generator, which receives a greater amount of incident light 7, as shown in FIG. The thickness "b" of the photovoltaic converter 1 is smaller than the diffusion length of the minority carriers of the base region 3. All photovoltaic converters 1 have the same length "c" without special requirements. The photovoltaic converters 1 are wired to each other along their opposite sides and transferred relative to each other to the transmission surface.

The generator operates as follows. A stepped photoactive surface 6 of a generator with a p-n junction 2 or a homojunction 5 with a beam 7 of the incident light arranged in close proximity to the surface.
shock. Current losses caused by surface recombination of the photogenerating carriers are thus reduced to a minimum.

Additional absorption of light 7 reflected by one of the faces of stage 10 occurs on the immediately adjacent face of stage 10.
The reflection losses of the light 7 are thus also reduced, while the area of the light active surface 6 of the generator is increased.

The different powers of the incident beam 7 can be counterbalanced by varying the area of the photoactive surface 6 by varying the base width "a" of the stage 10 (i.e. by varying their area) within a defined range. be done. The value of the current generated by each photovoltaic converter 1 is thus the same throughout the generator's operating plane.

The power loss due to the series resistance is such that if the width "a" of the base of stage 10 is made approximately equal to the diffusion length of the minority carriers in base region 3, then almost all the minority carriers generated by the incident light 7 will be It is collected by a pn connection placed under the continuous current collection contact 8 so as to be driven towards the reverse region 4, so that it is reduced to a minimum. The current collecting contacts 8, 9 are made of highly conductive metal with negligible resistance. The value of the series resistance of the generator can be as small as several thousandths of Ωcm ² . The generator may thus provide high efficiency while being illuminated by focused sunlight, for example when placed in the focal plane of a rectilinear paraboloid.

The generator provides high efficiency while being illuminated both from the pn junction 2 side or from the homojunction 5 side.

If the generator is made of silicon, typical dimensions of its elements are as follows: Photovoltage converter thickness “b” 0.2mm to 0.5mm, step base width “a”
From 0.2mm to 1.0mm, photoelectric converter length “c” from 5mm
50mm. The depth to which the p-n junction 2 and homojunction 5 are buried in the photoactive surface 6 is 0.1 μm to 0.5 μm. The number of photovoltage converters per cm ² of the generator surface is 10 to 30.
The voltage density value is from 5V/cm to 15V/cm.
It is. The thickness of the current collection contact is 5 μm to 10 μm.

The generator designed as shown in FIG. 1 has a large active surface 6 of photovoltage converters connected in series. Furthermore, it makes it possible to match the area of the photoactive surface 6 with the power distribution of the incident beam, reducing power losses in the case of non-uniform incident beams and increasing the efficiency of the generator when receiving highly concentrated light. .

3, 4 and 5, a generator comprising a photovoltage converter 1 made as a parallelepiped turned by an angle β (fan-shaped) around an axis 18 transverse to a rectifying surface 17. Other variations of are shown.

In this case the photoactive surface 6 is also arranged in a stepped manner, but it forms a concentric shape with its center at the axis 18 . A p-n junction 2 is located in the immediate vicinity of the photoactive surface 6.
is placed. Preferably, the angle β exceeds 30°. This design of the generator ensures that the power distribution of the light beam 7 is concentric and that the maximum light density is centered around the axis 18.
It seems to be optimal if it is placed in Axis line 18
The value of the resistance spread in the inverse region 4 near is negligibly small. It increases with distance from axis 18. However, the concentration of the light beam 7 is also reduced so that the value of the permissible spread resistance is respectively increased.

When compared with the embodiments shown in FIGS. 1 and 2, this generator forms a concentric shape when the photoactive surface is coaxial with the light beam, so that a high intensity of the light beam with a concentric power distribution can be obtained. Shows high efficiency in some cases.

A variant of the generator shown in FIGS. 6 and 7 is constructed as similar polygons, in particular equilateral trapezoids, arranged in an order of decreasing dimensions to form a step-shaped structure of the photoactive surface 6. A photovoltaic converter 1 is provided.

The generator comprises six sections 21 arranged symmetrically around a common center, each section forming a photovoltaic converter 1 connected in series. The sections 21 are separated from each other with the aid of a dielectric layer 22.

The area of the photoactive surface 6 of the photovoltage converter 1 is at step 10
increases progressively with distance from the center of the generator due to increasing length.

This arrangement allows it to result in low power losses when the generator is illuminated with a circular beam 7 with the maximum energy concentration close to its center.

When compared to the variants shown in FIGS. 3, 4 and 5, this generator makes it possible to obtain voltage densities per unit area that are ten times or more higher.

8 and 9 show a generator consisting of a photovoltaic converter 1 made as a disk of similar shape.
In this case the photoactive surface 6 is formed by an annular step 10 . The area of each stage 10 is matched to the concentration value of the circular incident beam 7.

This design of the generator lowers the spread resistance and
And the current and power depend linearly on the intensity of the luminous flux 7 to increase the continuous illumination range.

FIG. 10 shows a generator consisting of photovoltage converters 1 made as a similar ring in the form of an array of successively decreasing dimensions. In this case, the photoactive surface 6 is represented by a stepped cavity. The base of the generator is formed by a photovoltage converter 1 made as a disk.

When compared to the designs shown in FIGS. 8 and 9, this generator shows that the photoactive surface 6 is not shaded by current collecting contacts 8, 9, while the structure of stage 10 completely absorbs the generated current. It has a high efficiency when illuminated with a circular beam 7, since it ensures good collection and the power loss due to the series resistance of the generator is reduced.

In most generators designed according to the present invention, the current collection contacts do not occupy more than 1% of the area of the photoactive surface. Increasing the number of photovoltage converters per unit volume of the generator reduces the step size and the value of the series resistance, increases the generated carrier collection ratio, decreases the reflection ratio, increases the photoresistance of the generator, and increases the generator photoresistance. This results in an expansion of the light intensity range in which the value of the current and power generated by the device remains linearly dependent on the light intensity.

The generator shown in FIGS. 1 and 2 exhibits especially two-sided light sensitivity with the same efficiency and can be used as an element of a solar power storage device illuminated on both sides.

The concentric generators shown in FIGS. 3 to 10 exhibit high efficiency when used in combination with a beam concentrator made in the form of a rotating body. They can be employed in attitude-related systems as matching sensors.

11 to 14 show the sequence of main steps involved in manufacturing the semiconductor photovoltaic generator shown in FIGS. 1 and 2. FIG.

The manufacturing procedure according to the invention consists of the following phases.

A p-n junction 2 arranged along one side of the plate 23
The first metal-coated semiconductor board 23 (11th
) are assembled in a pile as shown in FIG. In the pile, the plates 23 are connected in series to each other by the use of current collecting contacts 8, 9 so as to form a monolithic structure by means of gluing them together with the use of soft solder. At the same time the pile is compressed to force out excess solder.

The ridges are cut in separate alignments along a plane 24 running at an angle with respect to the plane of the plate 23.

The array is placed in a tank 25 (FIG. 13) filled with a liquid having a high boiling temperature. By using the heater 26, the temperature of the liquid is raised until it reaches the temperature at which the solder melts. At this moment a force is applied to the alignment in the direction indicated by arrow 27 in FIG. The force causes the alignment elements to change shape and move along the solder layer relative to each other to match the contour of the stepped support 28 fixed to the bottom of the bath 25.

After cooling, an alignment structure is obtained as shown in FIG. 14, consisting of photovoltaic converters 1 moved with respect to each other with a commutating surface 17 and provided with a metallization 29 on the surface of the stage 10.

The last phase of the manufacturing process consists of etching away the metal layer 29. The surface of the semiconductor material in this phase is thoroughly cleaned, while the surface of stage 10 is coated with an anti-reflective coating.

This method of manufacturing a generator with a stepped structure of photoactive surfaces makes it possible to process several photovoltaic converters simultaneously during one manufacturing phase and to minimize the required manual labor. It therefore simplifies the generator manufacturing process and allows increased productivity.

The method allows the production of generators with photoactive surfaces in a stepped structure arranged on 1, 2, 3 or 4 sides of the generator, while the shape of the steps can be selected to ensure maximum efficiency. do.

The steps used to manufacture the generator as shown in FIGS. 1 and 2 will now be described in detail.

First the p-type conductive silicon plate is chemically and mechanically cleaned and sanded to remove the damaged layer from the surface. Then at its edges acceptor and donor impurities are introduced on both sides of the plate by means of co-diffusion to a depth of 0.1 μm to 0.5 μm to form the diode structure of the plate. After doping, successive layers of metal are applied to both sides of the plate by means of vacuum deposition. The silicon plates with full-layer coating on both sides are then welded together using soft solder to their surfaces to form the mounds. At the same time the pile is compressed to push out excess solder. After that the mountain is p
- The alignment is cut at an angle with respect to the n-junction.

The alignment obtained in this manner is placed in a bath which is heated to the melting temperature of the solder. The alignment element (photovoltage converter) is then arranged such that the area of each step is inversely proportional to the intensity of the incident light and the width "a" of each step is the diffusion of minority carriers in the base region, as shown in Figures 1 and 2. are moved from one another along the solder layers until a step structure equal to the distance is formed.

The step structure is then etched in a chemical to remove the damaged layer from the surface of the semiconductor material, as well as remove metal contacts from the step surface. This step also helps eliminate short circuits and increases the level of photoactivity of the irradiated surface. A current collector is then welded to the current collecting contacts 8,9.

The efficiency of this generator reaches 10% with an incident luminous flux intensity of more than 100 W/cm ² .

In order to manufacture a generator such as that shown in FIGS. 3, 4, and 5, it is necessary to carry out the operations necessary for manufacturing the generator shown in FIGS. 1 and 2. It is. However, after the alignment is all arranged on that side to eliminate the shunt, the photovoltage converter 1
is turned around the axis 18 by an angle β on the rectifying surface 17.

In order to manufacture a generator such as that shown in FIGS. 6 and 7, it is necessary that the operations necessary for manufacturing the generator shown in FIGS. 1 and 2 be carried out. However, the prepared device is divided into six trapezoidal sections. The sections are then interconnected with the aid of an insulating layer 22 to form a hexagonal generator.

To manufacture a generator such as that shown in FIGS. 8 and 9, a silicon plate with diode structure and metallization is cut into discs of decreasing diameter. The discs are soldered in series to form concentric peaks. The soldered core is compressed to push out excess solder. The outer current collecting contacts are protected with a chemically resistive membrane and then stage 1
Metal contacts are chemically etched from the surface of the 0.

To manufacture a generator such as that shown in FIG. 10, a silicon plate with diode structure and metallization is cut into rings of various diameters. At the same time one disk of the same material is made with a diameter greater than or equal to their rings. The disk is used as the base of the ring, which is arranged concentrically in order of decreasing size and soldered to the crest. Excess solder is removed by compressing the pile. The current collecting contacts of the outer photovoltaic converter are then chemically protected with varnish, while the metal contacts of the surface of stage 10 and the central section of the disc-shaped photovoltaic converter are chemically etched.

[Brief explanation of the drawing]

1 shows a cross-sectional view of a semiconductor photovoltaic generator according to the invention with a photoactive surface made as a stepped structure; FIG. 2 shows a top view of the semiconductor photovoltaic generator shown in FIG. 1; 3 is a side view of a semiconductor photovoltaic generator according to the invention made as an assembly of plates rotated around an axis; FIG. 4 is a top view of the generator shown in FIG. 3; FIG. 5 is a cross-sectional view taken along the line -- of the generator shown in FIG. 4, and FIG. 6 is a top view of a semiconductor photovoltage generator according to the invention using photovoltaic converters made as similar polygons. 7 is a cross-sectional view taken along the line -- of the generator shown in FIG. 6, and FIG. 8 is a semiconductor photovoltage generator according to the invention using a photovoltaic converter made as a similar disk. 9 is a cross-sectional view of the generator shown in FIG. 8, and FIG. 10 is a semiconductor photovoltaic device according to the invention using a photovoltaic converter constructed as a similar ring. A cross-sectional view of the generator, FIG. 11 shows a semiconductor photovoltage generator according to the invention in the phase of production of a diode structure being manufactured, and FIG. 21st
The generator shown in the figures, FIG. 13 is the generator shown in FIG. 12 according to the invention of the phase shifting photovoltaic converter in the rectifying plane during manufacture, and FIG. 14 is the photovoltaic converter during manufacture. 14 shows the generator shown in FIG. 13 according to the invention in phase after transferring the transducer; FIG. 1...Photovoltage converter, 2,2'...p-n junction, 3,
3'...Base region, 4...Reverse region, 5...Photoactive surface,
7... Luminous flux, 8, 9... Current collection contact, 10... Stage,
17... Rectifying surface, 18... Axis of rotation, 23... Semiconductor plate, 24... Metal layer.

Claims (1)

[Claims] 1. Each p-
It comprises a plurality of photovoltage transducers with n-junctions connected in series by current collection contacts along both sides to form a unitary structure such that the photoactive surface is stepped. A semiconductor photovoltage generator in which the area of the steps is inversely proportional to the intensity of the incident light and the width of each step is approximately equal to or less than the diffusion length of the minority carriers in the base region. 2. The semiconductor photovoltage generator according to claim 1, wherein the photovoltaic converters are rotated by a predetermined angle about an axis that crosses the rectifying surface to obtain a stepped structure. 3. The semiconductor photovoltage generator according to claim 1, wherein the photovoltaic converters have similar shapes and are arranged so that their dimensions decrease in accordance with the arrangement order to form a stepped structure. . 4. The semiconductor photovoltage generator according to claim 3, wherein the photovoltaic converter has a similar shape to a regular polygon. 5. The semiconductor photovoltage generator according to claim 3, wherein the photovoltage converter has a similar shape to a disk. 6. The semiconductor photovoltage generator according to claim 3, wherein the photovoltaic converter has a ring-like shape. 7 Assemble metal-coated semiconductor boards by stacking them in a pile with p-n junctions along one side, connect the stacked metal-coated semiconductors to each other by soldering, and compress them simultaneously to push out excess solder. , the connected metal-coated semiconductors are cut at an angle to their faces to form an array, the array is heated until the solder begins to melt, and when melted, the metal-coated semiconductors of the array are soldered together. staggered along the layer to form a staircase structure in which the area of each step is inversely proportional to the intensity of the incident light and the width of each step is approximately equal to or less than the diffusion distance of the minority carriers in the base region; A method for manufacturing a semiconductor photovoltage generator in which a metal coating is removed from the surface of a structure by an etching method.