JPH01201968A - Photoelectric conversion device - Google Patents

Abstract

PURPOSE:To prevent an impurity from a transparent conductive film layer of the basement of a semiconductor layer from being mixed at the time of manufacture of a semiconductor layer and to prevent an impurity from being diffused when not in use for a long period of time by forming a thin-film having a amorphous or microcrystalline structure containing carbon or carbon as its main ingredient and by laminating an amorphous or microcrystalline semiconductor layer thereon. CONSTITUTION:A blue plate glass is used as a substrate 1. A tin oxide 2 is accumulated on the surface thereof using normal pressure CVD method. Next, a thin film 3 having an amorphous or microcrystalline structure containing carbon or carbon as its main ingredient is accumulated by glow discharge decomposition using a mixed gas of methane, hydrogen, and diborane. On the surface of this film is accumulated a p-type microcrystalline SiC by an ECR plasma CVD method. After this, an intrinsic a-SiH film is laminated in another room by a glow discharge decomposition of a SiH4 gas. Furthermore, when Si glow discharge decomposition is performed, an n-type fine-crystal Si is obtained. Finally, laminating an Al electrode 5 by deposition completes a photoelectric element.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a photoelectric conversion device in which a transparent conductive film is formed on a glass or other transparent substrate.

"Prior Art" Conventionally, in photoelectric conversion elements using amorphous or microcrystalline semiconductors, as shown in Figure 1, a transparent conductive film (2), a P-type semiconductor, an I-type semiconductor, and a transparent conductive film (1) are deposited on a glass substrate (1). It has a structure in which a semiconductor, an N-type semiconductor (4), and a metal electrode (5) are stacked. This device has the function of converting light incident from the glass side into electricity at the PIN semiconductor section, and supplying it to an external load through a transparent conductive film and metal electrode.

However, the following problem occurs in such a photoelectric conversion device.

(a) Transparent conductive film such as tin oxide or zinc oxide (2
), a process such as plasma CVD or ECR plasma CVD is used to form an amorphous or microcrystalline semiconductor film on the surface of the transparent conductive film. 5n-0 bond or Zn-0 bond may be destroyed. As a result, Sn
The structure is such that atoms, Zn atoms, or O atoms are mixed into the semiconductor layer as impurities.

Such electrons act as trap levels for electrons or holes in the semiconductor layer, resulting in a decrease in photoelectric conversion characteristics.

(b) When forming a semiconductor thin film or using this photoelectric conversion device, the substrate temperature becomes high (50 to 350°C).
) There is a thing. At this time, it is thought that Sn, Zn, or O atoms, which have relatively weak bonds in the transparent conductive film, are thermally diffused from the transparent conductive film layer to the semiconductor layer. In particular, Zn atoms have the highest diffusion coefficient in Si compared to Sn atoms and zero atoms, and can be widely diffused into the semiconductor layer. At this time, the photoelectric conversion characteristics deteriorate as in (a) above.

For this reason, conventional methods have been used to reduce the substrate temperature during semiconductor formation, or to minimize the ion bombardment of the transparent conductive film by using a substrate bias method or a CVD method. However, these methods still have some problems in terms of difficulty in mass production, photoelectric conversion characteristics, and their deterioration.

[Structure of the Invention] An object of the present invention is to solve the above-mentioned problems.

When the structure is as shown in Figure 2, that is, the transparent conductive film (
2) Since the carbon thin film (3) formed on top is strong both chemically and thermally, it acts as a protective film against plasma ions of the transparent conductive film when forming a semiconductor film, and also acts as a protective film against plasma ions from the transparent conductive film layer. Its purpose is to prevent the diffusion of atoms.

A thin film having an amorphous or microcrystalline structure containing carbon or carbon as a main component can be formed by various methods.

Examples include glow discharge method, sputtering method, optical CVD method, microwave CVD method, and ECR plasma CVD method.

At this time, other than the sputtering method, it can be created by adding an appropriate amount of hydrogen gas to a hydrocarbon gas such as methane gas or ethylene, if necessary. Furthermore, impurity gases such as diborane and phosphine are introduced to create P-type or N-type
It is also possible to make a molded carbon film. Further, the energy gap of a thin film having carbon or an amorphous or microcrystalline structure mainly composed of carbon is 1.0 to 2. Since it is about OeV and about 5.4 eV for diamond, it is also possible to control it in the range of 1.0 to 5.4 eV depending on the process conditions. Therefore, by controlling the concentration and energy gap of B and P, it is possible to obtain electrically good ohmink characteristics at the interface between the transparent conductive film and the silicon layer or silicon carbide layer.

The thus obtained photoelectric conversion device with the configuration shown in FIG. can be made.

(Example) A blue plate glass (1.1 mm thick) was used as the substrate, and the surface was coated with TMT (tetramethyltin) and CF, Br.
.

0□, tin oxide was removed by atmospheric pressure CVD using N2.
Approximately 00 to 6000 people will accumulate. The sheet resistance of the modified thin film is set to 10 to 30 Ω/portion.

Next, a thin film having carbon or an amorphous or microcrystalline structure mainly composed of carbon, which is the gist of the present invention, is coated with methane, hydrogen,
20% by glow discharge decomposition method using diborane mixed residue
Deposit about the same amount as people.

At this time, the substrate is set as a film that is harder on the cathode side than on the anode side of the electrode, and the lower the total gas pressure, the harder the film becomes. At this time, Vickers hardness is 2500Kgf/mm2
The above film can be obtained.

On the surface of this film, approximately 200 P-type organic crystalline SiC films are then metamorphosed using the ECR plasma CVD method.

At this time, the carrier gas is F1□101005c,
The reaction gas is 5i)14. c) 14 each 1sccm, Bz
H60.02sccm, the pressure inside the reaction vessel is 10-4
The magnetic field is controlled at ~1O-3torr and the magnetic field is 875 Gauss.
By injecting s, tt wave output of about 200 to IKW into the plasma generation space, a P-type mechanical crystalline SiC film with Eg ~ 2.3 (eV) and conductivity σ 10-' ~ 10° (S/cm:l) can be obtained. After this, in a separate room,
Intrinsic a-5il is produced by the glow discharge decomposition method of Ia gas.
1 films are stacked to a thickness of about 3000 to 7000A. Furthermore, in a separate room, Hz138sccm, SiHagsccm, PH
N-type microcrystalline Si is obtained by glow discharge decomposition at 30.02 seconds. This film thickness is sufficient for metamorphosis of about 500 people.

Finally, about 2,000 Affi electrodes are stacked by vapor deposition to complete the photoelectric conversion element.

When this device is used as a solar cell, the P layer is made of microcrystalline Si.
Since it is C, the open circuit voltage is as high as 0.9V or more, and since the incorporation of impurities from the transparent conductive film is minimized by carbon or a thin film having an amorphous or microcrystalline structure mainly composed of carbon, it is a fill factor. will improve. Therefore, a highly efficient element with a photoelectric conversion efficiency of 12X or more when irradiated with sunlight can be obtained.

〔effect〕

By having the structure of the present invention, it is possible to prevent impurities from entering the transparent conductive film layer underlying the semiconductor layer during fabrication of the semiconductor layer, and to prevent impurities from diffusing during long-term use. can.

Further, even if carbon itself diffuses into the semiconductor layer from this carbon thin film, it will not form a trap level in the semiconductor layer unlike Sn, Zn, or In.

Furthermore, when a thin film mainly composed of carbon is used between the transparent conductive film on the side of the first incident light and the semiconductor layer, when carbon diffuses, the energy gap of the semiconductor layer on the side of the first incident light widens, allowing more light to pass through. We were able to lead to the area where photoelectric conversion is performed.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of a conventional photoelectric conversion device. FIG. 2 shows a schematic diagram of the photoelectric conversion device of the present invention. 1... Board 3...Thin film whose main component is carbon 4...Semiconductor layer

Claims (1)

[Claims] 1. A thin film having an amorphous or microcrystalline structure mainly composed of carbon or carbon is formed on a transparent conductive film, and an amorphous or microcrystalline semiconductor layer is laminated thereon. A photoelectric conversion device characterized by: 2. The thin film is doped with P or N type impurities and has an average thickness of 5 to 200 Å.
The photoelectric conversion device described in . 3. In the photoelectric conversion device according to claim 1, the amorphous or microcrystalline semiconductor layer is a silicon layer or a silicon layer.
A photoelectric conversion device that is a carbide layer.