JPS6226869A - Manufacture of photovoltaic device - Google Patents

Abstract

PURPOSE:To eliminate the adverse effects caused by heat and to deposit a transparent electrode layer having a high quality, by holding a lower electrode and a substrate having an amorphous semiconductor layer adhered thereon within a reaction chamber in which a vacuum can be held while insulating the lower electrode from the substrate, by introducing a reactive gas containing oxygen, by evaporating a material and by applying a high frequency voltage. CONSTITUTION:A reaction chamber 1 is evacuated to 10<-6>Torr or less. A reactive gas containing oxygen is introduced in the chamber 1 through a supply valve 3 so that the gas pressure is held around 10<-4>Torr. Particles evaporated from an evaporation source 4 and the reactive gas are converted into plasma by the discharge from a high-frequency voltage applied to a high-frequency coil 5, so that a discharge region is provided around the high-frequency coil 5. A lower electrode 23 and a susceptor 6 for holding a substrate 22 having an amorphous semiconductor layer 24 adhered thereon are provided so as to face the evaporation source 4 with the high-frequency coil 5 interposed therebetween and are fixed in the reaction chamber by means of an insulating support 7. The evaporated particles positively combine with the oxygen contained in the reactive gas converted into plasma in the discharge region within the high-frequency coil 5 and the compound is separated out and deposited on the amorphous semiconductor layer 24 of the substrate 22 insulated completely.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a photovoltaic device used for solar cells, optical sensors, and the like. In particular, the present invention relates to a method of manufacturing a photovoltaic device having a structure in which a substrate, a lower electrode, an amorphous semiconductor layer, and a transparent electrode are sequentially deposited.

(Background of the Invention) Since a photovoltaic device operates by irradiation with light, one of the electrodes that sandwich the amorphous semiconductor layer must be a light object.

Depending on the manufacturing method, the formation of the transparent electrode layer may be performed before depositing the amorphous semiconductor layer, i.e., the formation of the transparent electrode layer - the amorphous semiconductor layer - the two-part (metal) electrode on the glass substrate. The lower (metal) electrode - amorphous semiconductor layer -
In some cases, the transparent electrode is deposited in this order.

The present invention relates to a method for manufacturing a photovoltaic device in which a transparent electrode layer is deposited after the latter amorphous semiconductor layer is deposited.
A method for depositing a transparent electrode layer has been devised that has no adverse effect on the amorphous semiconductor layer, has stable characteristics, and improves the film formation rate.

(Prior art and its problems) Conventionally, photovoltaic devices such as solar cells and optical sensors have the structure shown in FIG. I have been using an electromotive force device.

FIG. 5 is a structural diagram of a photovoltaic device. 22 is a substrate made of ceramic or the like with a smooth surface. 23 is a lower electrode made of aluminum, chromium, etc. deposited on the substrate 22, and on the lower electrode 23, a P-i-N junction, an N-1
An amorphous semiconductor layer 24 having a -P junction or an arbitrary junction formed by doping with a certain impurity is deposited. Furthermore, a transparent electrode layer 2 is provided on this amorphous semiconductor layer 24.
5 is formed.

A transparent electrode layer 2 is added to the photovoltaic device 20 having the above structure.
When light is irradiated from the 5 side, electrons and holes are generated in the amorphous semiconductor layer 24 to generate a photovoltaic force or change the conductivity. The advantage of this structure is that the light is irradiated from the side of the transparent electrode layer 25, which has a thickness of several hundred layers, so the amorphous semi-quadram layer 24
The amount of light that reaches up to 500 nm is extremely large, and the amount of light absorbed for a given wavelength can be easily controlled by increasing or decreasing the film thickness. In the method for manufacturing the photovoltaic device 20, methods for depositing and forming the transparent electrode layer 25 on the amorphous semiconductor layer 24 include vacuum evaporation, sputtering, vapor deposition, spraying, etc. , metal oxides such as indium tin oxide have often been used as coating materials.

For example, indium tin oxide has high transmittance and high electrical conductivity, and the transparent electrode layer 2 of the photovoltaic device 20
5, it is an excellent material.

On the other hand, in the case of the above-mentioned method of depositing and forming the transparent electrode layer 25, unless the substrate is heated to 200°C or higher during film formation, optical properties such as transmittance and electrical properties such as conductivity are However, there was a problem that an excellent film could not be obtained.

However, the transparent electrode layer 25 on the amorphous semiconductor layer 24
When the substrate 22 (on which the amorphous semiconductor layer 24 has already been deposited) is heated to 200° C. or higher, the amorphous semiconductor layer 24
This may lead to the problem of having a negative impact on

That is, the metal contained in the lower electrode 23 is the amorphous semiconductor 1'.
P-i in the amorphous semiconductor layer 24 causes thermal diffusion to i24.
This is because the -N junction etc. will be destroyed and a sufficient photovoltaic force will not be obtained.

As described above, conventional methods for manufacturing a photovoltaic device that form a transparent electrode layer with excellent characteristics without adversely affecting the amorphous semiconductor layer have not been satisfactory.

(Objective of the present invention) The object of the present invention is to prevent the adverse effects of heat on the amorphous semiconductor layer when depositing a transparent electrode layer on the amorphous semiconductor layer, and to prevent the amorphous semiconductor layer from being adversely affected by heat, and to provide optical and electrical performance. Another object of the present invention is to provide a method for manufacturing a photovoltaic device that provides an excellent transparent electrode layer.

(Specific means for solving the problem) A specific means for solving the above-mentioned problem is a light-emitting device formed by sequentially depositing a lower electrode, an amorphous semiconductor layer, and a transparent electrode layer on the main surface of a substrate. In a method for manufacturing an electromotive force device, a lower electrode and a substrate on which an amorphous semiconductor layer is deposited are insulated and held in a reaction chamber that can be maintained in a vacuum, and a reactive gas containing oxygen is introduced into the reaction chamber, In this atmosphere, the transparent electrode material is evaporated from the evaporation source of a metal material such as indium or a metal oxide material, and
The method is characterized in that evaporated particles turned into plasma by applying a high frequency voltage near the evaporation source and the reactive gas or their compound are deposited as a transparent electrode layer on the amorphous semiconductor layer of the substrate. It is.

(Example) Hereinafter, an example of a manufacturing apparatus used in the method of manufacturing a photovoltaic device of the present invention will be specifically described with reference to FIG. 1, which is a schematic diagram schematically showing an example.

A reaction chamber 1 capable of maintaining a vacuum is connected to an exhaust system (not shown) such as a rotary pump via an exhaust valve 2, and the inside of the reaction chamber 1 is evacuated to a pressure of 10-' Torr or less. Furthermore, the reaction chamber 1 is connected to a gas system (not shown) via a reactive gas supply valve 3, a reactive gas containing oxygen is introduced, and the gas pressure is maintained at about 10-'Torr. The evaporation source 4 is made of a metal oxide material such as indium oxide or an evaporation material (transparent electrode material) of a metal material such as indium, and a high frequency coil 5 is provided near and above the evaporation source 4 .

That is, the evaporated particles evaporated from the evaporation source 4 are turned into plasma by the discharge of the high frequency voltage applied to the high frequency coil 5 together with the reactive gas, and form a discharge region around the high frequency coil 5. High frequency coil 5 is 13.56 Mll
It is connected to the high frequency power supply 11 indicated by □.

A substrate 22 on which a lower electrode 23 and an amorphous semiconductor layer 24 are deposited at a position facing the evaporation source 4 with the high frequency coil 5 in between.
A susceptor 6 is provided for holding the susceptor 6, and the susceptor 6 is fixed within the reaction chamber 1 by an insulating support 7 made of ceramic or the like. That is, the substrate 22 has a structure in which no bias voltage or the like is applied at all.

The evaporation source 4 is heated to evaporate indium oxide or the like using a heating means such as an electron beam or resistance heating.

In the embodiment shown in FIG. 1, an electron beam heating method is used in which an electron beam emitted from a filament 9 heats the evaporation source 4. Note that 10 is a heater that heats the substrate 22, and the substrate temperature is suppressed to 200° C. or less.

The transparent electrode layer 25 is deposited on the amorphous semiconductor layer 24 of the substrate 22 using the transparent electrode layer depositing apparatus having the above structure and operation.

Particles evaporated from the evaporation source 4 actively combine with oxygen, a reactive gas that has become plasma in the discharge region of the high-frequency coil 5, and are deposited on the amorphous semiconductor layer 24 of the completely insulated substrate 22. be coated.

In addition to oxygen gas alone, a mixed gas of oxygen gas and an inert gas such as argon may be used as the reactive gas exclusively contained in the reaction chamber.

Experiment 1 The inventor deposited a transparent electrode layer 25 on the amorphous semiconductor layer 24 of the substrate 22 under the following reaction conditions using the above-mentioned apparatus. Evaporation #4 is indium tin oxide.

Substrate temperature 155℃ Ar flow 13 55CCMO□ flow it
15 SCCM high frequency power supply output 200 electron beam Acceleration voltage 4.5 KV Substrate area 30 cal As a result, the transparent electrode layer 25 could be deposited at a high deposition rate of about 4.0 people/SEC, and as shown in FIG. A very high transmittance was obtained. The sheet resistance at this time was 90Ω/hole to 120Ω/hole, and the variation in film thickness was within ±5%.

In FIG. 2, the horizontal axis indicates the wavelength of the irradiated light, and the vertical axis indicates the transmittance with respect to the wavelength of the light.

A transmittance of 80% or more was obtained for light with a wavelength of 550 nm or more.

Experiment 2 The inventor deposited a transparent electrode layer 25 on the amorphous semiconductor layer 24 of the substrate 22 under the following reaction conditions using the above-mentioned apparatus. Evaporation #4 is indium tin oxide.

Substrate temperature 200°C Ar flow ffi 55 CCMO□ flow ffi 50 SCCM high frequency power supply output 200 W Electron beam acceleration voltage 4.5 KV Substrate area 30 col As a result, the transparent electrode layer 25 was deposited at an extremely fast film formation rate of about 20 people/SEC. A high-quality product with a transmittance of 83% or more at a wavelength of 550 r+m was obtained.

Comparative experiment With the above-mentioned device, no high-frequency voltage was applied to the high-frequency coil 5,
A transparent electrode layer 25' was formed on the amorphous semiconductor layer 24 of the substrate 22 under the following reaction conditions.

Substrate temperature 200°C Ar flow M
5 SCCM02 flow rate 155C
As a result, a transparent electrode N25 was deposited on a CM electron beam acceleration voltage of 4.5 KV and a substrate area of 30 cm at a film formation rate of 1.5 people/SEC, and its transmittance was close to that of the reactive gas supply port 12 containing oxygen. The transparent electrode layer 25' formed there
The transparent electrode layer 25゜ formed at a distance of 1
A variation of around 0% occurred, and the film thickness distribution was also distorted and varied. Furthermore, the sheet resistance of the transparent electrode layer 25゛ is 47Ω.
/mouth to 370Ω/mouth and unstable.

As a result of the above experiment, the following was found.

From Experiment 1 and the comparative experiment, (1) In order to improve the transmittance of the transparent electrode layer 25, it is important to sufficiently transform the reactive gas containing oxygen into plasma and cause it to react sufficiently with the evaporation material.

(2) In order to obtain a transparent electrode layer 25 with uniform sheet resistance and film thickness, it is important to form a discharge region in a wide range corresponding to the entire substrate to which it is deposited, and to promote plasma conversion of the reactive gas.

Also, from Experiments 1 and 2, in order to improve the deposition rate of the transparent electrode layer 25, the amount of reactive gas commensurate with the amount of evaporation material should be maintained at a substrate temperature that does not cause heat damage to the amorphous semiconductor layer 24. It is important to introduce it and actively turn it into plasma to react with the evaporation material.

Regarding the relationship between the output of the high frequency power source and the transmittance, the output of the high frequency power source was varied under the same conditions as in Experiment 1, and the results were measured under a light wavelength of 650 nm. The results are shown in FIG.

The horizontal axis in FIG. 3 shows the output of the high frequency power source 11, and the vertical axis shows the transmittance of the transparent electrode layer 25.

Next, an important point in the method for manufacturing a photovoltaic device of the present invention is that, as described above in the description of the device, the substrate 22 is held insulated, and a transparent electrode layer is formed on the amorphous semiconductor layer 24 without applying any bias. 25 is deposited and formed. This is board 2
2 is electrically connected to the inner wall of reaction chamber 1 and grounded, or DC
This is to prevent electrons, ions, etc. of the reactive gas turned into plasma from violently colliding with the amorphous semiconductor N24 and causing damage when a bias is applied.

The present inventor applied DC to the substrate 22 under the same reaction conditions as in Experiment 1.
A bias was applied in the range of -15 V to +15 V, and the transparent electrode N25 was deposited on the amorphous semiconductor N24 of the substrate 22.

In FIG. 4, the horizontal axis shows the DC bias, and the vertical axis shows the transmittance of the deposited transparent electrode layer 25. Note that this data was measured with previous irradiation at a wavelength of 650n+++.

As a result, when a negative bias is applied to the substrate, the transmittance is extremely low and a high-quality transparent electrode layer cannot be obtained. Further, when a positive bias is applied, although the transmittance does not decrease as much as a negative bias, it is difficult to obtain a transmittance of 80% or more, and it is never possible to obtain a transparent electrode layer for a photovoltaic device.

Note that the present invention is not limited to the above-described embodiments, and the evaporation source may be a metal oxide such as tin oxide or indium oxide, or a metal material such as tin or indium in addition to indium oxide.

(Effects) As described above, when depositing a transparent electrode layer on an amorphous semiconductor layer in the method for manufacturing a photovoltaic device of the present invention, the lower electrode and the amorphous semiconductor layer are placed in a reaction chamber that can be maintained in vacuum. At the same time, a reactive gas containing oxygen is introduced into the reaction chamber to evaporate the metal material and metal oxide material in this atmosphere, and a high frequency voltage is applied near the evaporation source. Because the transparent electrode layer is deposited on the amorphous semiconductor layer by applying an electric current, the substrate temperature is such that heat does not adversely affect the amorphous semiconductor layer, and extremely high quality with excellent transmittance and uniform sheet resistance and film thickness is achieved This is a method for manufacturing a photovoltaic device that can deposit a transparent electrode layer on an amorphous semiconductor layer and greatly improve the deposition rate.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram schematically showing an embodiment of a manufacturing apparatus used in the method for manufacturing a photovoltaic device of the present invention. Figures 2 and 3 are graphs of various data of the transparent electrode layer obtained by the method for manufacturing a photovoltaic device of the present invention, and Figure 2 shows changes in transmittance with respect to wavelength of light. . FIG. 3 shows the change in transmittance with respect to the output of the high frequency power source. FIG. 4 shows the change in transmittance between the transparent electrode layer obtained by the method for producing a photovoltaic device of the present invention and the transparent electrode layer produced by applying a DC bias to the substrate. FIG. 5 is a cross-sectional structural diagram of the photovoltaic device. 4... Evaporation source 5... High frequency coil 6... Susceptor 7... Insulating support 10... Heater 11... High frequency power supply

Claims (1)

[Claims] In a method for manufacturing a photovoltaic device in which a lower electrode, an amorphous semiconductor layer, and a transparent electrode layer are sequentially deposited on the main surface of a substrate, the lower electrode and The substrate covered with the amorphous semiconductor layer is held insulated and the transparent electrode material is evaporated from the evaporation source of the transparent electrode material in an oxygen-containing reactive gas atmosphere, and plasma is generated by applying a high frequency voltage near the evaporation source. 1. A method for manufacturing a photovoltaic device, comprising depositing the evaporated particles and the reactive gas or a compound thereof on the amorphous semiconductor layer of the substrate as a transparent electrode layer.