JPH0697472A - Semiconductor optical energy conversion apparatus - Google Patents

Abstract

PURPOSE:To permit fine holes or grooves to conduct a current therethrough without lowering open circuit photo electric voltage by providing the fine holes or the fine grooves in an insulating film and directly joinning a semiconductor and an optically transparent conductive material. CONSTITUTION:An insulating film 3 is joinned with a light incident surface of a semiconductor 2, and includes fine holes and/or fine grooves 6 provided for keeping conductivity between the semiconductor 2 and an optically transparent conductive material 4. Diameters of these fine holes and the width of the grooves are specified to be 10-1000Angstrom whereby electric charges produced by light irradiation can be moved without lowering the open circuit photo electric voltage Voc the fine grooves in such a manner, the semiconductor is prevented from being deteriorated to ensure a long if of the same and further ensure a greater phoptoelectric conversion eficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light energy conversion device for converting light energy into electric energy.

[0002]

2. Description of the Related Art With the recent increasing interest in global environmental problems, the effective use of solar energy has been called for. For example, a solar cell is expected as a device for efficiently converting sunlight energy into electric energy, and currently used ones are a pn junction solar cell mainly using single crystal silicon and a pin junction solar cell using amorphous silicon. It is a battery. It has been announced that a pn junction solar cell using single crystal silicon has an efficiency of more than 20%, and an amorphous silicon solar cell using a pin junction has an efficiency of about 12%. However, in order to put it into practical use for general electric power, it is necessary to further improve the efficiency and significantly reduce the cost. As one of the candidates for such a solar cell, a surface barrier type MIS junction solar cell is considered. This solar cell is easy to form a junction,
It is possible to use inexpensive semiconductor materials such as polycrystalline thin films, amorphous thin films, and granular films, and it is expected that the cost will be significantly reduced. However, in the MIS-junction solar cell, a metal thin film such as Pt is vapor-deposited on the surface for forming a junction, and there is a problem that efficiency is reduced. Therefore, a completely new type of solar cell having an ultrafine metal island such as Pt has been proposed (Japanese Patent Laid-Open No. 62-62).
76166). This solar cell open circuit light voltage Voc is 0.
The voltage is 63 to 0.68 V, which is considerably higher than that of a normal pn junction silicon solar cell, and improvement in efficiency is expected.

[0003]

However, since the fine metal islands are used, sunlight is absorbed and reflected by the metal as in the MIS junction solar cell, resulting in a decrease in efficiency.

The present invention has been made in order to solve the above problems, and is a novel semiconductor light energy conversion device which is highly efficient and can significantly reduce the cost without using fine metal islands. The purpose is to provide.

[0005]

The present invention which solves the above-mentioned problems provides a semiconductor, an insulating film provided on the light incident surface of the semiconductor,
A light-transmitting conductive material provided on the insulating film and a conductor ohmic-bonded to the other surface of the semiconductor are provided, and light is incident on the semiconductor through the light-transmitting conductive material to obtain electric energy. In the semiconductor light energy conversion device, the insulating film has minute pores and / or minute grooves, and the semiconductor and the light-transmissive conductive material are directly bonded through the pores and / or grooves. It is a characteristic semiconductor light energy conversion device.

[0006]

The micropores and / or microgrooves in the present invention function to pass an electric current without lowering the open circuit photovoltage Voc.

FIG. 1 is a sectional view showing a semiconductor light energy conversion device according to an embodiment of the present invention. In the figure,
3 is an insulating film bonded to the light incident surface of the semiconductor 2,
Micropores and / or microgrooves 6 provided to maintain the electrical conductivity between the semiconductor 2 and the light-transmissive conductive material 4.
Have. By defining the diameter of the fine pores and the width of the grooves to be 10 to 1000Å, it is possible to easily move the charges generated by the light irradiation without lowering the open circuit photovoltage Voc.

Examples of the semiconductor in the present invention include, for example, Si, GaAs, GaP, GaAs _x P _1-x , In.
P, AlAs, AlP, CdTe, CdSe, CdS,
Cu ₂ S, ZnTe, ZnSe, Zn ₃ P ₂ , MoTe ₂ ,
MoSe ₂ , MoS ₂ , WTe ₂ , WSe ₂ , WS ₂ , Fe
S ₂ , RuS ₂ , FePS ₃ , ZrTe ₂ , ZrS ₂ , Cu
InS ₂ , CuInSe _{2 and the} like can be mentioned.

The structure of this element is basically similar to that of the MIS type solar cell, and it is not necessary to perform the expensive and complicated steps such as the conventional pn and pin junction, and the cost can be reduced. Furthermore, in the solar cell having the pn, pin junction, there is a problem that the recombination of carriers in the p layer or the n layer existing in the light incident surface reduces the photocurrent, but in the semiconductor of the present invention, the light incident surface is reduced. No such p-layer or n-layer exists, and a large photocurrent can be obtained.

The insulating film may be provided with pores having a diameter of 10 to 1000Å and / or grooves having a width of 10 to 1000Å by, for example, a sol-gel method, an etching method using a porous film, or in some cases. Can use a conventionally known photoresist method, X-ray resist method, electron beam resist method, or the like.

[0011]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited thereto.

Example 1 A 0.5 mm thick n-type silicon single crystal (n-Si) wafer (donor concentration: about 1 × 10 ¹⁶ cm ^-3 ) was etched with hydrofluoric acid, nitric acid and a small amount of bromine. It carried out with the etching solution containing (CPD-2). Subsequently, 2 drops of 1N hydrochloric acid were dropped by a pipette into a solution obtained by mixing 1 g of polyvinylpyrrolidone (Mw = 120 × 10 ⁴ ), 2 g of ethyl silicate, and 50 g of ethanol to prepare a dip coating solution. The prepared solution was left at room temperature for 48 hours, and then dip-coated on the previously etched silicon single crystal. Further, it was left at room temperature for 192 hours to prepare a SiO ₂ film containing polyvinylpyrrolidone. The film thickness of the obtained SiO ₂ was 40Å. Subsequently, the silicon single crystal with the SiO ₂ film was placed in an electric furnace and baked at 600 ° C. to remove polyvinylpyrrolidone. As a result, a SiO ₂ film having a pore size of about 50Å was obtained. Subsequently, indium tin oxide (ITO) was vapor-deposited on this by 5,000 liters. A mask was used to deposit gold in a net-like pattern on this, and a copper wire was bonded thereto using a silver paste. The indium tin oxide is a light transmissive conductive material.

On the other hand, on the back surface of this n-Si wafer,
An indium-gallium alloy was used to form a conductor that was ohmic-bonded, and a copper wire was bonded with a silver paste.

In the solar cell thus manufactured, the above-mentioned two copper wires were connected via a variable resistor,
The photocurrent-voltage characteristics were measured while irradiating light from a 0 W halogen lamp as a light source from the arrow a. As a result, as shown in FIG. 2, a closed circuit photocurrent of 25 mAcm ^-2 , an open circuit photovoltage of 0.
60V, fill factor 0.67 was obtained, and the photocurrent was stable for 200 hours or more.

Example 2 The same n-Si wafer as that used in Example 1 was etched with an etching solution (CPD-2) in the same manner as in Example 1, and subsequently, in an oxygen stream containing water vapor. Four
It was heated at 00 ° C. for 1 hour to form a thin oxide film on the surface. Gold was vapor-deposited thereon to a thickness of about 100 Å and immersed in a 10% hydrogen fluoride aqueous solution for about 30 seconds. As a result, the oxide on Si was removed at the minute cracks (width 50 to 100 Å) existing in the gold thin film. Further, it was immersed in aqua regia for about 8 hours to remove the gold on the surface. Subsequently, a light transmissive material and a conductor that was ohmic-bonded were formed in the same manner as in Example 1 to complete a solar cell. The characteristics of the solar cell thus manufactured were a closed circuit photocurrent of 23 mAcm ^-2 , an open circuit photovoltage of 0.56 V and a fill factor of 0.63, and the photocurrent was stable for 200 hours or more.

Example 3 An n-Si wafer with a SiO ₂ film was prepared in the same manner as in Example 2. Then, 1,2,3,4,5-pentaphenylcyclopentadiene was vapor-deposited to a film thickness of 50 Å, and then put in an electric furnace to proceed with crystallization at 200 ° C. The vapor deposition film thus obtained had fine pores of 50 to 100 liters. The device thus obtained was immersed in a 10% hydrogen fluoride aqueous solution for about 30 seconds to remove the oxide on the silicon wafer existing in the minute pores. Further, it was immersed in nitrobenzene to remove 1,2,3,4,5-pentaphenylcyclopentadiene, and an n-Si wafer with a SiO ₂ film having fine pores was produced. Subsequently, a light transmissive material and a conductor that was ohmic-bonded were formed in the same manner as in Example 1 to complete a solar cell. The characteristics of the solar cell thus produced were a closed circuit photocurrent of 24 mAcm ^-2 , an open circuit photovoltage of 0.54 V and a fill factor of 0.62, and the photocurrent was stable for 200 hours or more.

[0017]

As described above, according to the present invention, the semiconductor, the insulating film provided on the light incident surface of the semiconductor, the light-transmissive conductive material provided on the insulating film, and the semiconductor In a semiconductor light energy conversion device having a conductor that is ohmic-bonded on the surface side and injecting light into the semiconductor through the light transmissive conductive material to obtain electric energy, an insulating film provided on a light incident surface portion of the semiconductor Minute pores and /
Alternatively, by providing the minute groove, it is possible to provide a semiconductor light energy conversion device which can suppress the deterioration of the semiconductor, prolong the life thereof, and obtain a further large photoelectric conversion efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor light energy conversion device according to an embodiment of the present invention.

FIG. 2 is a graph showing a measurement result of a current-voltage curve according to an example of the present invention.

[Explanation of symbols]

 1 Ohmic-Joined Conductor 2 Semiconductor 3 Insulating Film 4 Light-Transmissive Material 5 Variable Resistance 6 Micropores and / or Microgrooves

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuyuki Kuroda 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Nippon Petroleum Co., Ltd. Central Technology Research Institute

Claims (3)

[Claims] 1. A semiconductor, an insulating film provided on a light-incident surface of the semiconductor, a light-transmissive conductive material provided on the insulating film, and a conductor ohmic-bonded to the other surface of the semiconductor. In the semiconductor light energy conversion device for obtaining electric energy by injecting light into the semiconductor through the light transmissive conductive material, the insulating film has fine pores and / or fine grooves, A semiconductor light energy conversion device, wherein the semiconductor and the light-transmissive conductive material are directly bonded via a groove. 2. The diameter of the fine pores of the insulating film is 10 to 10.
The semiconductor light energy conversion device according to claim 1, wherein the device is 1000 Å. 3. The width of the minute groove of the insulating film is 10 to 1
The semiconductor light energy conversion device according to claim 1, wherein the semiconductor light energy conversion device is 000Å.