JPH01280366A - Photovoltaic element - Google Patents

Abstract

PURPOSE:To enhance the photoelectric conversion efficiency by a method wherein a p-type semiconductor thin film is a semiconductor thin film, composed of hydrogenated silicon and carbon, which is formed by alternately laminating two layers whose composition of silicon and carbon is different. CONSTITUTION:An electrode composed of a light-transmitting conductive oxide, a p-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, a second substantially intrinsic semiconductor thin film, an n-type semiconductor thin film and a rear metal electrode are formed one after another on a light-transmitting and insulating substrate. In such a photovoltaic element, said p-type semiconductor thin film is a semiconductor thin film, composed of hydrogenated silicon and carbon, which is formed by alternately laminating two layers whose composition of silicon and carbon is different. It is suitable that a film thickness of the two layers whose composition ratio of said silicon to carbon is different is 10Angstrom or higher and less than 50Angstrom . In addition, it is preferable that said p-type semiconductor thin film is formed by using a vapor chemical decomposition method which utilizes discharge energy or luminous energy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing an amorphous silicon photovoltaic device, and particularly to improving its performance.

[Background Art] Amorphous silicon photovoltaic devices are attracting attention as clean light energy conversion devices because they are inexpensive to manufacture, require little energy to manufacture, and can be manufactured over a large area.

[Prior art and its problems] This amorphous silicon photovoltaic device in the prior art mainly includes a p-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, and a second substantially intrinsic semiconductor thin film. , n-type semiconductor thin films stacked in this order has been proposed by us.

A problem with the prior art is that it is necessary to further improve the film characteristics of the p-type semiconductor thin film.

For this reason, a silicon carbide semiconductor thin film is used as a p-type semiconductor thin film, but if the amount of carbon contained in silicon is increased to widen the optical forbidden band width of the semiconductor thin film, this thin film There was a problem in that the electrical conductivity of the film decreased and the film properties deteriorated.

The inventors of the present invention focused on this point and as a result of intensive study,
We have discovered that the photoelectric conversion efficiency of photovoltaic devices can be dramatically improved by improving the film properties of P-type semiconductor thin films.We are hereby disclosing this new technology and, in return, are receiving patents. In accordance with the spirit of the law, this request is for the granting of patent rights, which are exclusive and exclusive rights (Article 1 of the Patent Law).

[Disclosure of the Invention] The present invention provides an electrode made of a transparent conductive oxide, a P-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, and a second substantially intrinsic semiconductor thin film on a transparent and insulating substrate. essentially intrinsic semiconductor thin film, n
In a photovoltaic device in which a type semiconductor thin film and a back metal electrode are formed in this order, the HAP type semiconductor thin film is a semiconductor thin film made of hydrogenated silicon and carbon,
The photovoltaic element is characterized in that two layers having different compositions of silicon and carbon are laminated alternately, and more preferably, the film thickness of the two layers having different composition ratios of silicon and carbon is , a photovoltaic element having a diameter of 10 Å or more and less than 50 Å.

That is, the present invention provides an electrode made of a transparent conductive oxide, a P-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, a second substantially intrinsic semiconductor thin film, and a second substantially intrinsic semiconductor thin film on a transparent and insulating substrate. The basic structure of the photovoltaic element is a photovoltaic element formed in this order of a P-type semiconductor thin film, an N-type semiconductor thin film, and a back metal electrode.
It has a structure of (hereinafter also referred to as two layers for short).

The method for manufacturing two layers having such a structure is preferably carried out by a vapor phase chemical decomposition method (hereinafter also referred to as CVD method) using discharge energy or light energy, and more preferably by a vapor phase chemical decomposition method using light energy. This is carried out by a chemical decomposition method (hereinafter also referred to as photo-CVD method).

The raw material for producing pN is basically a mixed gas of a silane compound gas, a doping gas that imparts p-type conductivity, a dilution gas, and a carbon-containing compound gas.

As such a silane compound, silane, disilane, trisilane, etc. are used.

Diborane, trinotylboron, and trimethylindium are used as the dopant gas that imparts p-type conductivity.

Hydrogen, helium, argon, fluorine, etc. are used as the diluent gas.

Further, as the carbon-containing compound, acetylene, monomethylsilane, dimethylsilane, etc. are used.

The most characteristic feature of the present invention is that the P-type semiconductor thin film of the present invention is a thin film (hereinafter referred to as a thin film) formed by repeatedly stacking two semiconductor thin films (hereinafter also referred to as a barrier layer or a well layer) having different compositions of silicon and carbon. (also referred to as a laminated film for short), and the two semiconductor thin films having different compositions of silicon and carbon are preferably
It is a very thin semiconductor thin film with a thickness of more than 50 Å and less than 50 Å.

Both the barrier layer and the well layer in the present invention are hydrogenated amorphous semiconductor thin films, and the barrier layer has a larger amount of carbon than the well layer compared to silicon.

Such a method for manufacturing the N-layer film can be carried out by temporally changing the mixing ratio of the silane compound and the carbon-containing compound in the CVD method.

The mixing ratio can be changed by controlling the flow rates of the silane compound and carbon-containing compound gas.

The pN film thickness is typically about 10-1000 degrees thick. The thickness of both the barrier layer and the well layer is 10 Å or more and less than 50 Å.

The manufacturing conditions other than the two-layer flow rate are: substrate temperature 100 to 400;
The pressure per °C is about 0.001 to 10 Torr.

The first substantially intrinsic semiconductor thin film (hereinafter also referred to as a buffer layer for short) contains a silane compound gas, a diluent gas,
It is formed by °CVD of a mixed gas such as a carbon-containing compound gas. These gases are preferably the same as those used for producing the P-type semiconductor thin film.

As the silane compound gas, carbon-containing compound gas, and diluent gas, disilane, acetylene, and hydrogen are preferable.

The method for manufacturing the buffer layer is to form a p-type semiconductor thin film using the CVD method, then stop supplying the doping gas, gradually reduce the carbon-containing compound gas, and manufacture the thin film under the same conditions. is more preferable.

The buffer layer is an amorphous semiconductor thin film made of hydrogenated silicon and carbon. The buffer layer thickness is 25 Å
The upper limit is not particularly critical as long as it is within several thousand, but a deposition degree of at most 500 is sufficient. Particularly preferred are amorphous thin films having a thickness in the range of .

The second substantially intrinsic semiconductor thin film (hereinafter also referred to as an i-layer) is formed by a CVD method (hereinafter also referred to as a plasma CVD method) using discharge of a silane compound gas. Silane and disilane are used as the silane compound.

The i-layer is an amorphous semiconductor thin film of hydrogenated silicon.The film thickness of 1Jiji is about 1000 to 100OO.

As the manufacturing conditions for the i-layer, the flow of silane compound gas is ff1l.
-100sec cm, substrate temperature 200~4o.

゛C1 pressure 0. OITorr~10Torr,
The discharge power is about 0.001 to IW/cmz.

Hydrogen or helium may be used as a diluent gas for the silane compound gas.

The n-type semiconductor thin film is a hydrogenated silicon semiconductor thin film containing a mixture of amorphous and crystalline materials (hereinafter also referred to as n-layer), and is produced in a plasma CVD chamber using a mixed gas of silane compound gas, dopant gas, and dilution gas. Manufactured by

The thickness of the n-layer is about 100 to 1,000 layers.

Silane and disilane are used as the silane compound, and hydrogen is used as the diluent gas.

Phosphine is used as the dopant gas.

The manufacturing conditions for nN are as follows: silane compound gas flow t;

, 1 to 101005e, dopant gas flow rate 0.
001-10105e, hydrogen flow i11-101005c
, pressure 0.01~10torr, discharge power 0.01
~10 W/cm'', and the five-plate temperature is approximately 100 to 400°C.

Hereinafter, one example of a specific embodiment of the present invention will be explained with reference to Examples.

[Example] The manufacturing equipment includes a preparation room, a take-out room, and a P-type semiconductor 1119.
Formation and optical CV for first substantially intrinsic semiconductor thin film formation
It consists of a total of five chambers: a D chamber, a first plasma CVD chamber for forming a second substantially intrinsic semiconductor thin film, and a second plasma CVD chamber for forming an n-type semiconductor thin film. are separated. In plasma CVD, a parallel plate capacitive coupling type method was used.

First, two layers were formed.

A hydrogenated amorphous silicon carbide semiconductor thin film was prepared as PM. A glass plate was used as a transparent insulating substrate. We used a transparent conductive thin film consisting of two layers: one containing oxidized indium and tin, and the other containing oxidized tin. The manufacturing method for the two layers is
A direct decomposition photoCVD method was used.

The degree of vacuum achieved in the optical CVD chamber was 10-'Torr or less.

The manufacturing conditions for pN were a substrate temperature of 250'C, disilane,
The flow rate of diborane and hydrogen gas was 5scc each.
m, 0.3sccm, 10105c.

The acetylene flow rate is explained below, and the pressure inside the reaction chamber is 0. It was set to ITorr. In the photoCVD method, the ultraviolet light of 185 nm and 2
45 nm light was used.

As a two-layer deposition method, the above-mentioned ultraviolet light was introduced into the optical CVD chamber through a quartz window to decompose the mixed gas of disilane, acetylene, diporane, and hydrogen introduced into the optical CVD chamber. went. At this time, the acetylene flow rate is set to two values, lsec and 5sc, using a flow rate controller.
A laminated semiconductor thin film was formed by alternating the ratio of carbon to silicon contained in the pN thin film by alternating the ratio by cm.

The repetition time interval was set to 40 seconds and 100 seconds, and two samples were produced.

Since the thin film deposition rate under these conditions is 0.5/sec, the thickness of the barrier layer or well layer in the laminated film is determined by two samples: 20 and 50.

This corresponds to the fact that we prototyped a model.

The residence time of the mixed gas in the photoCVD chamber was made shorter than the deposition time of a monoatomic layer.

The thickness of the two layers was 100 to 150 people.

Next, a buffer layer was formed.

As a buffer layer, an amorphous semiconductor thin film of hydrogenated non-doped silicon carbide was used. In particular, it was formed so that the amount of carbon gradually decreased compared to silicon.

As a manufacturing method, disilane and acetylene are produced by photo-CVD.
After the light was introduced into the chamber and the pressure was maintained at a constant value, ultraviolet light generated from a low-pressure mercury lamp was introduced through a quartz window to deposit an amorphous semiconductor thin film on the p-type semiconductor thin film. At this time, the flow rate of acetylene was introduced in such a manner that the flow rate was gradually decreased relative to the flow rate of disilane.

Next, an i-layer was formed.

The i-layer is an amorphous semiconductor thin film of hydrogenated silicon.

As a manufacturing method, monosilane is used in the first plasma CV method.
The manufacturing conditions for the first layer of monosilane 101 are as follows:
05e, i-plate temperature 250° C., pressure 50 mTorr. The discharge power was 0°01 W/Cmz. i
The thickness of the layer was 6000.

Next, an n layer was formed.

As a manufacturing method, monosilane is produced by second plasma CVD.
After introducing the material into a chamber and setting the temperature and pressure to constant values, high-frequency power from parallel plate electrodes was applied to generate discharge, thereby depositing the material. The manufacturing conditions for nN are as follows: monosilane tc amount 1
secm, phosphine flow rate 0.2 secm, hydrogen flow 31
10 sec m, substrate temperature 250°C, pressure Q,
Torr, discharge power 0゜2 W/cm", nN
The film thickness was 400 people.

Finally, a metal electrode on the back was formed.

As a method for forming the back electrode, aluminum metal was vapor-deposited using a resistance heating type vacuum vapor deposition apparatus.

The photovoltaic device of the present invention can be used as a solar shemulator (A
The voltage-current characteristics were measured under simulated sunlight from ML, 100 mW/cm"). The measurement results are shown in Table 1. Sample 1 was measured without using a laminated film, and sample 2 was tested under 50 people. Sample 3 uses a laminated film with a repetition period of 20 people. Sample 3 uses a laminated film with a repetition period of 50 people, and some photoelectric conversion occurs. Improvement in efficiency was observed, and 2
It is clear that the photoelectric conversion efficiency is significantly improved by using a laminated film having a repetition period of 0.

As described above, the present invention provides an electrode made of a transparent conductive oxide, a p-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, a second substantially intrinsic semiconductor thin film, and a second substantially intrinsic semiconductor thin film. In a photovoltaic device in which a substantially intrinsic semiconductor thin film, an n-type semiconductor thin film, and a back metal electrode are formed in this order, the p-type semiconductor thin film is a semiconductor thin film made of hydrogenated silicon and carbon, It is a photovoltaic device characterized by two layers having different compositions of silicon and carbon stacked alternately, and the thickness of the nif layers having different composition ratios of silicon and carbon is sometimes 10 Å. This is a photovoltaic device with less than 50 members, and by adopting such a configuration, the photovoltaic device has a significantly improved photoelectric conversion function.

Therefore, the present invention is industrially useful as photovoltaic elements such as solar cells and optical sensors.

1 0.87 16.0 0.710 9
．． 802 0.87 16.0 0.720
9.903 0.87 1? , 0 0.
720 10.7 Patent applicant Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] (1) On a transparent and insulating substrate, an electrode made of a transparent conductive oxide, a p-type semiconductor thin film, a first substantially intrinsic semiconductor thin film, and a second substantially intrinsic semiconductor thin film In a photovoltaic device in which an n-type semiconductor thin film and a back metal electrode are formed in this order, the p-type semiconductor thin film is a semiconductor thin film made of hydrogenated silicon and carbon, and the silicon and carbon have different compositions. A photovoltaic device characterized by two layers stacked alternately. (2) The photovoltaic device according to claim 1, wherein the two layers having different composition ratios of silicon and carbon have a thickness of 10 Å or more and less than 50 Å.