JPH0376166A - Photoelectric converter - Google Patents

Abstract

PURPOSE:To enhance the open terminal voltage and a short-circuiting photocurrent of an amorphous photovoltaic element by forming at least one of first and second conductivity type semiconductor thin films of II-VI-V2 compound semiconductor thin film. CONSTITUTION:A conductivity type II-VI-V2 semiconductor thin film 3 is formed of compound semiconductor of P such as ZnSiP3nGeP2, etc. The conductivity type of the compound is controlled to be p-type or n-type by modulating a composition in addition to doping of impurity. In the case of a ZnSiP2 film, high frequency power is independently controlled by using three types of target of Zn, Si and P metals, composition in the film is controlled, and sputtered. If the conductivity type of the thin film is p-type, the other conductivity type semiconductor thin film 5 exhibits n-type properties. The substrate 1 is made of blue plate glass quartz, etc., and the second electrode is made of meal oxide such as tin oxide 2, indium oxide, etc., or light transmission metal, etc. As a result, the open terminal voltage and short-circuiting current of an amorphous photoelectric converter can be improved.

Description

[Detailed description of the invention] (Technical field) The present invention relates to improving the performance of amorphous solar cells, and in particular, aims to improve the efficiency of amorphous solar cells by increasing open circuit voltage and short-circuit photocurrent. Regarding technology.

[Background technology]

Amorphous solar cells (amorphous photoelectric conversion elements) are already in practical use as low-output energy sources to power calculators and watches. However, as an energy supply source with a large output, its performance is insufficient, and various studies are being carried out with the aim of improving its performance. The photoelectric conversion efficiency of a solar cell is expressed as the product of open circuit voltage, short circuit current, and fill factor. As a result of various studies, the short-circuit photocurrent and fill factor have been dramatically improved and improved, but the open-circuit voltage has not been sufficiently improved.In recent years, efforts have been made to improve the reliability of solar cells. , a pin-type amorphous solar cell with nine layers on the light incident side has been studied. In order to improve the open-circuit voltage of this amorphous solar cell, it is necessary to improve the photoelectric properties of the p-type semiconductor thin film.In particular, it is necessary to expand the optical band gap and improve the electrical conductivity at the same time. However, there were technical difficulties. The reason for this is that when the optical bandgap is expanded, −
This is because the electrical conductivity decreases in a significant manner. A microcrystalline thin film has been proposed as a material that satisfies these requirements. However, attempts have been made to form p-type organic crystalline thin films on transparent electrodes using conventional techniques such as plasma CVD and photoCVD, but as a result, the open circuit voltage of amorphous solar cells is This did not lead to an improvement in charging conversion efficiency. In order to solve this problem, we have completed the present invention after extensive research.

[Basic idea of the invention]

■To obtain dramatic improvements in photoelectric properties using only group-based materials,
A great deal of study is required and there are many difficulties as mentioned above.
We focused on the fact that the bandgap can be controlled arbitrarily, and crystallinity can be easily obtained compared to Group Ⅰ materials. By forming an amorphous photovoltaic device in which an n-■-VZ group compound semiconductor thin film with a controlled conductivity type is applied to a conductivity type semiconductor thin film, the open circuit voltage and short circuit of the amorphous photovoltaic device can be reduced. I was able to increase the current.

[Disclosure of the invention]

The present invention includes a substrate, a first electrode, a first conductive type semiconductor thin film,
In an amorphous light converting element formed by laminating a substantially intrinsic amorphous semiconductor thin film, a second conductivity type semiconductor thin film, and a second electrode in this order, the first conductivity type semiconductor thin film and the second conductivity type semiconductor thin film are stacked. The gist is an amorphous photovoltaic device characterized in that at least one of the conductive semiconductor thin films (hereinafter abbreviated as conductive semiconductor thin films) is an n-■-vz group compound semiconductor thin film. be.

In the configuration of the photoelectric conversion element of the present invention, regarding the conductive type semiconductor thin film, specifically, when the first conductive type semiconductor thin film is a p-type semiconductor in which holes are majority carriers, the second conductive type semiconductor thin film is a p-type semiconductor in which holes are majority carriers. The thin film is an n-type semiconductor in which electrons are the majority carriers. Furthermore, when the first conductive type semiconductor thin film is an n-type semiconductor, the second conductive type semiconductor thin film is a p-type semiconductor.

Hereinafter, a configuration example of a photoelectric conversion element of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the layer structure of the element of the present invention,
FIG. 2 is a schematic diagram showing an example of the layer structure of an amorphous photoelectric conversion element according to the prior art.

In the figure, 1.-------Glass substrate, 2--.
--- Tin oxide, 3 --- P-type conductivity type semiconductor 'iR film, 4 --- Substantially intrinsic amorphous semiconductor thin film, 5 n type conductivity type semiconductor thin film, 6
Aluminum metal electrode, 7・・・・−・・・・P
The mold is a crystalline silicon thin film.

The present invention is directed to the P-type conductivity type semiconductor FRH3 in FIG.
or at least one of the n-type conductivity type semiconductor thin films 5 is n-
This is an R/-Vg group compound semiconductor thin film. Accordingly, the conductivity type 1-IV-V group compound semiconductor thin film in the present invention is a salt wide gap semiconductor material, and preferably has a forbidden band width of 1.8 eV or more. Specifically, it is a P-based compound semiconductor, such as Zn5iPz, Z
nGePz, CdS iPz, ZnS 1Ast, etc., and mixtures of constituent elements of these compounds are also effectively used. In addition, in the examples described later, the p-type conductivity type semiconductor thin film 3 is a p-type Z n S i A S
An example using z was shown.

The conductivity type of these compounds is controlled not only by doping with impurities but also by modulating the composition, and can be made p-type or n-type.

The thickness of the conductive semiconductor thin film used is 30λ~1
In particular, the conductive semiconductor thin film used on the light incident side has a thickness of 30 to 500 mm.

Methods for forming the present conductivity type n-1v-v group semiconductor thin film are not particularly limited when carrying out the present invention, but include sputtering, vacuum evaporation, ion blating, and methods using iodine. There are chemical vapor diffusion methods, etc., and from the viewpoint of practicality, sputtering method is preferable.

As a specific method for forming a compound semiconductor thin film by sputtering, the formation of a Zn5iP film, for example, will be described. Sputtering is performed using three types of targets: Zn metal, St gold metal, and P metal, by independently controlling high frequency power and controlling the composition in the film. The gas to be introduced is A r 10
5CCI 1% Hl 2sccm.

Pressure is 10+torr, high frequency power is 50W to Zn,
Input 30W into Te and 60W into P. Furthermore, a method using a one-source sputtering method and using Zn5iPz as a target is also effective.

Substantially intrinsic (hereinafter abbreviated as i-type) semiconductor thin films include hydrogenated silicon thin films, hydrogenated silicon germane thin films, hydrogenated silicon carbon thin films, etc., which form photoactive regions of amorphous solar cells. It is. These substantially intrinsic semiconductor thin films are made from raw materials that are appropriately selected depending on the desired semiconductor thin film from compounds containing silicon in the molecule, compounds containing germanium in the molecule such as germane and silylgermane, and hydrocarbon gases. It is easily formed by applying a plasma CVD (chemical vapor deposition) method or a photo CVD (chemical vapor deposition) method to a gas. The effects of the present invention are not hindered in any way by using conventional techniques in forming an i-type semiconductor thin film, such as diluting the raw material gas with hydrogen, helium, etc., or adding a very small amount of diporane to the raw material gas. Regarding the forming conditions, the forming temperature is 150 to 400°C, preferably 175 to 350°C, and the forming pressure is 0.01 to 5 Torr, preferably 0.5 Torr.
Performed at 0.03 to 1.5 Torr. The thickness of the i-type semiconductor thin film is appropriately determined depending on the use of the solar cell, and is not a limiting condition of the present invention. In order to achieve the effects of the present invention, 1000 to 10000 people is sufficient. be.

Next, in the photovoltaic device of the present invention, at least one conductive type semiconductor thin film contains II-IV-V.

Apply group compound semiconductor thin film. Specifically, when the conductivity type of the thin film is p-type, the other conductivity type semiconductor thin film exhibits n-type properties, and is made of n-type microcrystalline Ti.
IW14, n-type amorphous thin film, etc. can be effectively used. To give a concrete example, an n-type microcrystalline silicon thin film,
Carbon-containing microcrystalline silicon thin films, microcrystalline silicon carbide thin films, amorphous silicon thin films, amorphous silicon carbon thin films, amorphous silicon germane thin films, and the like can be effectively used. These n-type semiconductor thin films are made of compounds containing silicon in the molecule, compounds containing germanium in the molecule such as germane, silylgermane, etc.
A raw material selected from hydrocarbon gas, etc., depending on the desired semiconductor thin film, is mixed with compounds from group Ⅰ of the periodic table, such as phosphine and arsine, and hydrogen, and then plasma CVD (chemical vapor deposition) is performed. ) method or photo-CVD (chemical vapor deposition) method. Furthermore, diluting the raw material gas with an inert gas such as helium or argon does not impede the effects of the present invention in any way.The formation conditions include a formation temperature of 150 to 400°C;
Preferably it is 175 to 35 o'c, and the forming pressure is 0.
01-5 Torr, preferably 0.03-1.5 T
It is done in orr. The thickness of the n-type semiconductor thin film is sufficient to cover 200 to 500 people.

For forming the amorphous photoelectric conversion element of the present invention, the preferred raw material gases to be used will be explained with further specific examples.For compounds having silicon in the molecule,
Hydrogenated silicones such as monosilane, disilane, trisilane; hydrogenated silicones substituted with alkyl groups such as monomethylsilane, dimethylsilane, trimethylsilane, tetramethylsilane, ethylsilane, diethylsilane; vinylsilane, divinylsilane, trivinylsilane, vinyldisilane, divinyl Hydrogenated silicones that have radically polymerizable unsaturated hydrocarbon groups in their molecules such as disilane, propenylsilane, ethynylsilane, etc.: Effectively use fluorinated silicones in which some or all of the hydrogen in these hydrogenated silicones has been converted to 1F with fluorine. Can be used.

As specific examples of hydrocarbon gases, hydrocarbon gases such as methane, ethane, propane, ethylene, propylene, and acetylene are useful. These hydrocarbon gases are conveniently used to change the optical bandgap in forming carbon-containing microcrystalline silicon thin films, microcrystalline silicon carbide thin films, and the like. In addition, for this purpose, silicon hydrides substituted with alkyl groups, silicon hydrides having a radically polymerizable unsaturated hydrocarbon group in the molecule, and silicon hydrides in which hydrogen in these silicon hydrides has been partially or completely replaced with fluorine are also used. Materials such as silicon oxide are also useful.

There are no particular limitations on the substrate, first electrode, second electrode, etc. Conventionally used glass substrate materials such as blue plate glass, borosilicate glass, and quartz glass are useful as substrates, but metals and plastics can also be used as substrate materials. Materials that can withstand temperatures above can be used more effectively. For the first and second electrodes, one or both must be translucent for sunlight to enter, but there are no other restrictions.Specifically, tin oxide, oxide Metal oxides such as indium and zinc oxide, translucent metals, and the like can be effectively used. In addition, as a metal electrode, aluminum,
An appropriate material can be selected from metal oxides such as chromium, nickel-chromium, silver, gold, and platinum, and metal oxides such as tin oxide, indium oxide, and zinc oxide.

[Example 1] As a forming apparatus for a photoelectric conversion element, a plasma CVD method,
A film forming apparatus to which sputtering method and photo-CVD method can be applied was used. The element configuration is as shown in FIG.

A glass substrate 1 coated with a tin oxide film 2 having a thickness of 1 μm was placed in a film forming apparatus.

As the first conductivity type semiconductor thin film 3, p-type Zn5i A
s z was first formed. Zn metal and St gold metal As were used as sputtering targets, and the sputtering conditions were a pressure of 10 mtorr and an Ar gas flow rate of 101 mtorr.
05e, high-frequency electric cuffs of 0W, 40W, and 80W and a substrate temperature of 250°C were used. TC film time 250 seconds, 100
After forming the substrate, the substrate was transferred to a 0-order substantially intrinsic semiconductor thin film forming chamber where heat treatment was performed at 300'C in a hydrogen gas atmosphere, monosilane was introduced, and the pressure was 0.0
Plasma CVD at 8 Torr and formation temperature of 250°C
An amorphous silicon thin film 4 was formed to a thickness of 5,000 wafers by a method. Plasma CVD method is 13.56 MH
The high-frequency discharge of z was used. At this time, the RF power is 3
It was within 0. After forming the substantially intrinsic semiconductor thin film, the substrate was transferred to an n-type semiconductor thin film forming chamber. Monosilane/
Raw material gases consisting of phosphine/hydrogen were introduced such that their respective flow rates were at a ratio of 1010.1/100. The n-type semiconductor thin film 5 was formed to a thickness of 500 nm by plasma CVD under conditions of a pressure of 0.5 Torr and a formation temperature of 240°C. Plasma CVD method uses R of 13.56 MHz.
F discharge was used. At Kono, the RF power was 15 songs. Then, it was taken out from the thin film forming apparatus, and an aluminum metal electrode serving as a second electrode was formed to produce a light 1 conversion element.

[Comparative Example 1] In Example 1, I
I-① In place of the Vz group compound semiconductor thin film, a P-type machine crystalline silicon thin film 7 was formed. The device configuration is shown in FIG. 2. An amorphous photoelectric conversion element was formed using the same steps as in Example 1 except for the nine layers.

To form a P-type mechanical crystal thin film, a mixed gas of monosilane/diborane/hydrogen in the ratio of 110.03/200 was introduced into the film forming chamber, and the R'F power was 50 W, the pressure was 0.1 torr, and the substrate temperature was 250''C. Conducted with a discharge time of 150 seconds, 100
Formed a person.

The performance of the amorphous photoelectric conversion element produced as described above was evaluated. For evaluation, the photovoltaic characteristics of the amorphous charge conversion element were measured by irradiating it with AMl, 5.100 mW/cd light using a solar simulator. As a result of comparing the performance of the photovoltaic elements, an improvement of 5% in open circuit voltage and 15% in short circuit photocurrent was observed. As a result, the photoelectric conversion efficiency was improved by 20%.

〔Effect of the invention〕

As is clear from the above Examples and Comparative Examples, the performance of the amorphous photoelectric conversion element that has been put to practical use in the prior art is improved by using a ■-■-v2 group compound semiconductor in at least one of the conductive semiconductor thin films. In particular, the open-circuit voltage and short-circuit photocurrent are significantly improved. That is, the present invention greatly contributes to improving the photoelectric conversion efficiency of amorphous photoelectric conversion elements at a practical level. In this way, the present invention can provide a technology that enables the high conversion efficiency required for power solar cells, and it cannot be said that it is an extremely useful invention for the energy industry.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the layer structure of the present invention or an example thereof, and FIG. 2 is a schematic diagram showing an example of the layer structure of an amorphous photoelectric conversion element in the prior art or a comparative example. In the figure: 1 Glass substrate, 2 - Tin monoxide, 3 P-type Zn5jAst, 4 Substantially intrinsic amorphous semiconductor thin film, 5 N-type microcrystalline silicon thin film, 6 Aluminum metal electrode, 7・−・−・−・
−・−・P-type crystalline silicon thin film. Figure 1

Claims (1)

[Claims] (1) An amorphous material formed by laminating a substrate, a first electrode, a first conductivity type semiconductor thin film, a substantially intrinsic amorphous semiconductor thin film, a second conductivity type semiconductor thin film, and a second electrode in this order. In the photoelectric conversion element, at least one of the first conductive type semiconductor thin film and the second conductive type semiconductor thin film is II-IV-V_
An amorphous photoelectric conversion element characterized by being a Group 2 compound semiconductor thin film.