JPH02122576A - Photoelectric conversion device and manufacture thereof - Google Patents

Abstract

PURPOSE:To decrease a photodeterioration phenomenon and obtain the superior quality of a film to improve the sensitivity at the side of a long wave length by making an amorphous silicon semiconductor layer have a specific optical gap; besides, making its layer contain a specific hydrogen concentration in its amorphous silicon semiconductor layer. CONSTITUTION:This device allows an amorphous silicon semiconductor layer 3 to be joined with the first, second, and third conductivity types, in other words, to be formed into P-I-N junction shape on a substrate 1 on which a heat-resisting conductive film 2 is deposited. Further, film formation is performed in such a way that its substrate temperature is 400-450 deg.C and an optical band gap is 1.7-1.5 eV and then a hydrogen concentration in the semiconductor layer 3 is 10-0at.%. In such a case, when at least an I layer out of the amorphous silicon semiconductor layer 3 which is formed into P-I-N junction shape is deposited, it is exposed into a high temperature and an element 0.2-1.0ppm of the group III or V of the periodic table witch determines the conductivity type that is opposite to the conductivity type of the element which is diffused into the I layer is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to optical measuring devices, optical sensors used in optical switching elements, etc., photoelectric conversion devices such as solar cells, and methods of manufacturing the same.

[Background of the invention]

Currently, the amorphous silicon semiconductor layer with P-1-N junction is
It is widely used in photoelectric conversion devices such as solar cells and optical sensors.

This P-I-N junction amorphous silicon semiconductor layer has a P layer and an NJ'5 arranged on both sides of a photocarrier (hole or electron) generation layer (generally one layer), and when exposed to light irradiation. The carriers generated are collected by electrodes formed on the outer surfaces of the PF5 and N layers to obtain photovoltaic force or to obtain changes in the conductivity of the amorphous semiconductor layer.

A photoelectric conversion device having such an amorphous semiconductor layer is
In particular, in one amorphous semiconductor layer, Stibler-Wronski
A photodegradation phenomenon called the effect occurs, and the initial characteristics are reduced to 1/1.
It is known that the value decreases to about 0. This is a fatal drawback for photoelectric conversion devices such as solar cells and optical sensors, and greatly narrows the scope of use of photoelectric conversion devices.

A conventional photoelectric conversion device, for example, an amorphous silicon solar cell element has a transparent glass substrate 61 as shown in FIG.
A transparent conductive film 62 is deposited thereon by a thermal decomposition method or an electron beam method, and an amorphous semiconductor layer, which is an amorphous semiconductor layer, is further formed by P-I-N bonding on the transparent conductive film 62 by a plasma CVD method. A crystalline silicon semiconductor layer 63 is deposited, and a metal electrode 74 of AI, Ni, Cr, etc. is further deposited on the amorphous silicon semiconductor layer 63.
(Refer to Japanese Patent Laid-Open No. 16690/1983).

Amorphous silicon semiconductor layer 6 with conventional P-I-N junction
Due to the characteristics of the film quality of No. 3, the temperature of the film-forming substrate in the plasma CVD method has been set at 200 to 250° C., and the amorphous silicon semiconductor layer 63 has been deposited. This is also the transparent glass substrate 6
ITO (indium tin oxide), tin oxide, etc. are used as the transparent conductive film 62 on the top of the transparent conductive film 62. In order to obtain a film with good transparency and low resistance, the transparent conductive film 62 must be heat resistant in plasma. The substrate temperature was set considering the temperature (maximum around 300° C.).

Therefore, the present inventors conducted extensive research, and in a photoelectric conversion device having a P-I-N junction amorphous silicon semiconductor layer 63, the temperature of the film-forming substrate was set to a high temperature, and the amorphous silicon semiconductor layer 63 was It has been found that the photodegradation phenomenon can be improved by setting the hydrogen concentration in 63 and the optical gap to predetermined values.

[Object of the present invention]

The present invention was devised based on the above findings,
The purpose is to reduce the photodegradation phenomenon that occurs in P-1-N junction amorphous silicon semiconductor layers, and to provide a photoelectric conversion device with high film quality and improved sensitivity on the long wavelength side, and a method for manufacturing the same. be.

[Specific Means for Achieving the Object] According to the present invention, in order to achieve the above-mentioned object, an amorphous silicon semiconductor layer with P-1-N junction is formed on the conductive crotch of a heat-resistant metal. In the photoelectric conversion device, the amorphous silicon semiconductor layer includes 1. The present invention provides a photoelectric conversion device with an optical gap of 7ev to 1.5ev and a hydrogen concentration of less than 10 at% in an amorphous silicon semiconductor layer, and further includes a P-I - In a method of manufacturing a photoelectric conversion device in which an N-junctioned amorphous silicon semiconductor layer is formed, the amorphous silicon semiconductor layer is formed at a temperature of 40° C.
Group Ⅰ of the periodic table or The same element as the group Ⅰ element is used at a gas concentration of 0.2 to 1, OPP
Provided is a method for manufacturing a photoelectric conversion device in which a film is formed using m.

By the above-mentioned specific method, when producing an amorphous silicon semiconductor layer with a P-1-N junction, the substrate temperature was set to 400°C.
With the above settings, it is possible to reduce the hydrogen concentration of the I-type amorphous silicon semiconductor layer, which has the greatest effect on the characteristics due to photodeterioration due to light irradiation. As a result, less hydrogen changes due to the provision of light energy, and even if light irradiation is continued for a long time, the I5 amorphous silicon semiconductor layer becomes stable, and it is thought that output characteristics with less deterioration can be obtained. In addition, by depositing at least one amorphous silicon semiconductor layer on a high-temperature substrate, an element that determines the conductivity type of the layer from the P-type or N-type layer deposited before the one-layer amorphous silicon semiconductor layer can be added. The force is diffused into the q-layer amorphous silicon semiconductor layer, and the Fermi level of one layer changes. In order to correct this, elements that determine the conductivity type opposite to the elements diffused during the deposition of the single-layer amorphous silicon semiconductor layer (elements in group Ⅰ or group Ⅰ of the periodic table) ( In this method, a single-layer amorphous silicon semiconductor contains an element of periodicity group Ⅰ or group ②.

〔Example〕

Hereinafter, the method for manufacturing a photoelectric conversion device of the present invention will be explained in detail based on the drawings.

FIG. 1 is a cross-sectional structural diagram showing the structure of a solar cell according to a photoelectric conversion device of the present invention.

In the solar cell according to the present invention, a first conductivity type, a second conductivity type, and a third conductivity type are bonded on a substrate 1 on which a heat-resistant conductive film 2 is adhered, that is, a P-I-N junction. An amorphous silicon semiconductor layer 3 and a transparent electrode 4 are deposited and configured.

That is, it is a so-called reverse type in which light is irradiated from the opposite surface of the substrate 1.

The substrate 1 is made of a heat-resistant material such as glass, ceramic, or stainless steel, and a heat-resistant conductive film 2 is deposited on one main surface of the groups Fj and l.

The heat-resistant conductive film 2 is made of titanium (Ti), nickel (Ni),
Titanium-silver (Ti-Ag), chromium (Cr), stainless steel, tungsten (W), ill (Ag), platinum (
Metals such as Pt), tantalum (Ta), and cobalt (Co) are used. Specifically, after a mask is attached on one main surface of the substrate 1, the above-mentioned metal film is deposited by a sputtering method, an electron beam method, a resistance heating method, etc. It is formed by depositing a metal film and then performing a resist etching process.

In the amorphous silicon semiconductor layer 3, a first conductivity type, a second conductivity type, and a third conductivity type are joined to form a beaten P-I-N junction. Specifically, the amorphous silicon semiconductor layer 3 is formed using plasma CV in which a silicon compound gas such as silane or disilane and a carrier gas such as hydrogen are decomposed by glow discharge.
The N layer is formed using the above-mentioned gas mixed with an N-type doping gas such as phosphine, the first layer is formed using the above-mentioned reaction gas, and the P layer is formed using the above-mentioned reaction gas. It is formed from a reactive gas containing a P-type doping gas such as diborane.

The transparent electrode 4 is formed in a predetermined shape on the amorphous silicon semiconductor layer 3 so that the amorphous silicon semiconductor layer 3 is sandwiched between the heat-resistant conductive film 2 and the amorphous silicon semiconductor layer 3 . Specifically, the transparent electrode 4 is deposited by a thermal decomposition method or an electron beam method by attaching a mask to the amorphous silicon semiconductor layer 3. As a transparent conductive film, I
TO (indium tin oxide), tin oxide, etc. are used.

When light is irradiated from the transparent electrode 4 side, the light reaches the amorphous silicon semiconductor layer 3 via the transparent electrode 4,
Carriers are generated from one layer of the amorphous silicon semiconductor N3. Then, due to the electric field at the interface between the P layer and the N layer sandwiching one layer, carriers are collected in the P layer and the N layer, and photovoltaic force is derived from between the heat-resistant conductive film 2 and the transparent electrode 4. .

Next, the formation of the amorphous silicon semiconductor layer 3, which is a feature of the present invention, will be described in detail.

In order to elucidate the relationship between the substrate temperature and photodeterioration during the deposition of the amorphous silicon semiconductor layer 3, the present inventors set the substrate temperature at 200°C (line a), 300°C (line b), and 400°C (line b). Line C
) and 450° C. (line d), and each amorphous silicon semiconductor layer was irradiated with light of 100 mW/c111 of AMl.

The results are shown in FIG. In the characteristic diagram, the horizontal axis shows the light irradiation time, and the vertical axis shows the rate of decrease from the initial characteristics.

As is clear from the figure, the substrate temperature is 200°C (line a),
Conventional amorphous silicon semiconductor layers deposited at 300°C (line b) are subject to significant photodegradation and degradation from the initial stage, and when the irradiation time is 105 minutes, the photodegradation decreases by 9%.
It even reaches 0χ.

In contrast, the substrate temperature was set to 400°C (line c) and 450°C.
The amorphous silicon semiconductor layer of the present invention deposited according to line d has a small rate of decline in initial characteristics (slope in the graph) due to photodeterioration, and when the irradiation time is 105 minutes, the initial characteristics are 20% lower than the initial characteristics.
The deterioration remains below χ.

Furthermore, the amorphous silicon semiconductor layer of the present invention was formed at a substrate temperature of 300°C (line b), and the amorphous silicon semiconductor layer of the present invention was formed at a substrate temperature of 400°C (line C). I investigated the spectral sensitivity. The results are shown in FIG.

As is clear from the figure, the substrate temperature was set at 300°C (line b'
), the spectral sensitivity of the amorphous silicon semiconductor layer formed at a substrate temperature of 400°C (line c') is shifted to the longer wavelength side,
It can be confirmed that a sensitivity peak exists on the long wavelength side. If such an amorphous silicon semiconductor layer 3 is used in a solar cell, deterioration of characteristics due to photodeterioration can be suppressed and the amount of energy absorbed can be increased.

When we investigated the physical properties of the amorphous silicon semiconductor N3, which was formed at the above-mentioned substrate temperatures of 400°C and 450°C, we found that the optical band gap was 1.7e, a value that Saneshun could accept.
V~1.5eV (measured by Tautz blot of absorption coefficient)
Met. At this time, the concentration of hydrogen contained in the amorphous silicon semiconductor layer 3 was 10atχ to Oatχ (measured by infrared absorption, amount of hydrogen released, Rutherfort back scanning, etc.).

When such an amorphous silicon semiconductor layer 3 is used as a solar cell element and its characteristics are investigated, it has been confirmed that the rate of deterioration can be halved.

Note that the amorphous silicon semiconductor layer 3 used in the above experiment has a P-1-N junction, and although the substrate temperature was set at a high temperature during the deposition of each layer, it is susceptible to photodegradation. A high temperature substrate (400° C. or higher) may be used only during layer formation and desorption.

In the solar cell, which is a photoelectric conversion device shown in Fig. 1, an N layer (containing elements of group Ⅰ of the periodic table such as phosphorus) is deposited on a heat-resistant conductive layer. The one-layer amorphous silicon semiconductor layer 3 is made of N at a temperature of 400°C or higher.
When a film is formed on N, phosphorus atoms etc. in the N layer are activated,
It will diffuse into one layer. As a result, the Fermi level of one layer becomes approximately 0.6 eV. For this reason, a doping gas containing an element from group Ⅰ of the periodic table, such as diborane (B2H6), which is a P-type dopant for the two-layer amorphous silicon semiconductor layer formed on the first layer during the I layer formation and desorption, is used together with the silane gas. It is important to supply it as a reaction gas and correct the Fermi level to an appropriate value.

FIG. 4 shows the flow rate of diborane supplied together with silane during I layer formation and the Fermi energy that changes depending on diborane.

As is clear from the figure, 1 of the amorphous silicon semiconductor layer 3
To correct for the appropriate Fermi energy as a layer,
The diborane/silane flow ratio is 0.2 to 1. The range of OPPm.

As described above, according to the present invention, by setting the substrate at a temperature of 400° C. or higher, it is possible to satisfactorily suppress the deterioration of initial characteristics due to photodeterioration, and the spectral sensitivity can be extended to the long wavelength side. Furthermore, it was confirmed that it could be easily controlled to an appropriate Fermi level.

FIG. 5 shows the second method of manufacturing a photoelectric conversion device of the present invention.
FIG. 2 is a cross-sectional structural diagram showing the structure of an optical sensor according to an embodiment of the present invention. That is, by shifting the spectral sensitivity toward longer wavelengths, an optical sensor with excellent red sensitivity can be achieved.

The optical sensor of this embodiment has a heat-resistant conductive film 52a.

Heat-resistant conductive films 52a and 5
2b, the first conductivity type, the second conductivity type, and the third conductivity type.
An amorphous silicon semiconductor layer 53 and a transparent electrode 54 are formed in which the conductivity types of
-N bonded laminate a.

b are held together via a transparent electrode 54.

Similar to the solar cell shown in FIG. 1, the substrate 51 and the heat-resistant conductive film 52 are made of a heat-resistant material such as glass, ceramic, and stainless steel.
a and 52 b are titanium (
Ti), nickel (Ni), titanium-silver (Ti-Ag)
, chromium (Cr), stainless steel, tungsten (W),
Metals such as silver (Ag), platinum (Pt), tantalum (Ta), and cobalt (Co) are used.

The amorphous silicon semiconductor layer 53 is a laminate a in which at least heat-resistant conductive films 52a and 52b are formed.

In the portion b, a first conductivity type, a second conductivity type, and a third conductivity type are joined, that is, a P-I-N junction is formed. Specifically, as described above, the N layer, the ■ layer, and the P layer are stacked from the substrate 51 side.

The transparent conductive film 54 is formed of a metal oxide film such as tin oxide, indium oxide, or indium tin oxide, and is formed to be a film common to at least the laminates a and b. Specifically, after mounting a mask on one main surface of the transparent substrate 51,
The metal oxide film described above is deposited by an electron beam method or a thermal decomposition method.

Then, a constant bias voltage is applied between the metal electrodes 52a and 52b from an external circuit (not shown).

The optical sensor having the above structure has a structure in which the diodes of the carcasses a and b are tied together with # connected to the P-1-N junction.

Now, if a + bias voltage is applied to the metal electrode 52a of the laminate a and a negative voltage is applied to the metal electrode 52b of the laminate A, then the laminate a
A reverse bias is applied to the amorphous silicon semiconductor layer 53a on the side, and a forward bias is applied to the amorphous silicon semiconductor layer 53b on the side of the stack.

In the dark state, the resistance between the metal electrodes 52a and 52b is the sum of the reverse resistance Ra of the laminate a and the forward resistance Rb of the laminate A, and the current flowing between the metal electrodes 52a and 52b is
This corresponds to the resistance (Ra+Rb).

In the bright state where light is irradiated from the opposite side of the substrate 1 of the above-mentioned photosensor, a photovoltaic force is generated in the laminate a and the laminate, but since they are at opposite potentials, they cancel each other out, and in reality, the photovoltaic current is Although it does not flow, there is + on the metal electrode 52a, and the metal electrode 52
Since a negative bias voltage is applied to b, the laminate a
A reverse photocurrent is generated. Note that the laminated body becomes a resistor consisting of a forward resistance of a diode.

The current between the two metal electrodes 52a and 52b is from the metal electrode 52a of the stacked body a to the amorphous silicon semiconductor layer 53a.
The current flows to the N layer, the first layer, the second layer, the transparent conductive film 54, the second layer of the amorphous silicon semiconductor layer 53b of the laminated body, the second layer, the NM layer, and the metal electrode 52b.

Here, the photoconductivity of the entire optical sensor appears to have decreased due to the light irradiation, and it functions like a photoconductive type sensor. As a result, the illuminance-resistance value characteristic becomes linear, and the γ value becomes approximately 1.

As mentioned above, in the deposition of the amorphous silicon semiconductor layer 53, which is a feature of the present invention, if the substrate temperature in the deposition of the amorphous silicon semiconductor layer 53 is set to 400° C. or higher, the temperature as shown in FIG. As described above, photodeterioration can be effectively suppressed from the initial characteristics.

As is clear from Figure 3, the optical sensor fabricated at a substrate temperature of 400℃ (line 1)
It can be confirmed that the spectral sensitivity of the optical sensor fabricated using the method is shifted toward longer wavelengths, and the sensitivity peak exists on the longer wavelength side. This means that the optical sensor has excellent blue sensitivity.

Furthermore, as described above, N of the amorphous silicon semiconductor layer 53 is
When forming one layer on top of the other, phosphorus atoms in the N layer become activated and mix into the first layer, causing the Fermi level to change to 0.6 eV. In addition, it is preferable to supply a doping gas containing a Group Ⅰ element of the periodic table, which is a P-type dopant, such as diporan (B2H2) together with the silane gas as a reactive gas.

As mentioned above, in order to fabricate an amorphous silicon semiconductor layer at a substrate temperature of 400°C or 450°C, a transparent electrode - an amorphous silicon semiconductor layer - is placed on a glass substrate due to the film characteristics of the transparent electrode at this stage. It is not suitable for ordinary types covered with metal electrodes. However, as long as the heat-resistant transparent electrode becomes inexpensive and suitable for mass production, the present invention is not limited to this, and can also be applied to an optical sensor such as that proposed in Japanese Patent Application No. 62-331620 previously proposed by the present applicant.

〔Effect of the invention〕

As described above, the present invention provides P on a substrate coated with a conductive film.
In a photoelectric conversion device that forms an amorphous silicon semiconductor layer with a P-I-N junction, a heat-resistant metal is used for the conductive film, the substrate temperature is set to 400°C or higher, and the non-crystalline silicon semiconductor layer with a P-I-N junction is When depositing at least one of the crystalline silicon semiconductor layers, exposure to high temperatures determines the conductivity type opposite to the element of one conductivity type that is diffused into the layer. 0.2 to 1.0 PPm of elements of group or group
As a result, the deterioration of initial characteristics due to photodeterioration can be suppressed well, and the spectral sensitivity can be extended to the long wavelength side, resulting in a photoelectric conversion device that can obtain stable output characteristics.

This allows the use of the photoelectric conversion device to be expanded.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a solar cell according to the method of manufacturing a photoelectric conversion device of the present invention. FIG. 2 is a characteristic diagram showing the state of substrate temperature and photodeterioration in the method for manufacturing a photoelectric conversion device of the present invention. FIG. 3 is a characteristic diagram showing the relationship between substrate temperature and spectral sensitivity in the method of manufacturing a photoelectric conversion device of the present invention. FIG. 4 is a characteristic diagram showing the relationship between the flow rate of diborane mixed into silane during I layer formation and Fermi energy. FIG. 5 is a sectional view showing the structure of a solar cell according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view of an amorphous silicon solar cell element, which is a conventional photoelectric conversion device. 1.51 ・ ・ ・ 2.52a, 52b 3.53a ・ ・ ・ 4.54, ・ ・ ・ ...Insulating substrate...Heat-resistant conductive film Amorphous silicon semiconductor layer Transparent electrode

Claims (2)

[Claims] (1) In a photoelectric conversion device in which a P-I-N bonded amorphous silicon semiconductor layer is formed on a heat-resistant metal conductive film, the amorphous silicon semiconductor layer has a temperature of 1.7ev to 1.5e.
1. A photoelectric conversion device characterized by an optical gap of v and a hydrogen concentration of less than 10 at % in an amorphous silicon semiconductor layer. (2) In a method for manufacturing a photoelectric conversion device in which a P-I-N junction amorphous silicon semiconductor layer is formed on a conductive film of a heat-resistant metal, at least an I layer of the amorphous silicon semiconductor layer is formed. An element which is deposited at a substrate temperature of 400° C. or higher and which is the same element in Group III or V of the periodic table that determines the P layer or N layer deposited on the I layer, in the I layer. 1. A method for manufacturing a photoelectric conversion device, comprising: