JPH0338068A - Photoelectromotive force element - Google Patents

Abstract

PURPOSE:To secure the diffusion preventive effect for obtaining the high thermal resistance by a method wherein the dopant diffusion preventive layers exceeding two layers are laid between a p type semiconductor layer and an i type semiconductor layer. CONSTITUTION:A transparent electrode 2, a p type semiconductor layer 3, an interface layer 4 as a diffusion preventive layer, an i type semiconductor layer 7, an n type semiconductor layer 8 and a rear surface electrode 9 are successively lamination-formed on a translucent substrate such as glass. Next, the diffusion preventive layers exceeding two layers are provided between the p type semiconductor layer 3 and the i type semiconductor layer 7. That is, the interface layer 4 is composed of superlattice structure provided with multiple SiN layers, etc. Through these procedures, sufficient diffusion preventive effect on a dopant such as boron, etc., can be achieved to enhance the thermal stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photovoltaic element used as a solar cell or the like.

[Conventional technology]

For example, in a pin-type amorphous silicon solar cell, an amorphous silicon semiconductor layer with a p-type conductivity (hereinafter simply referred to as a p-type semiconductor layer) and an amorphous silicon semiconductor layer with an i-type conductivity are formed on a transparent substrate. An amorphous silicon semiconductor layer with an n-type conductivity (hereinafter simply referred to as an n-type semiconductor layer) is laminated in this order, but an l-type semiconductor layer is laminated on a p-type semiconductor layer. In order to prevent boron, which is a dopant of the p-type semiconductor layer, from diffusing into the l-type semiconductor layer, an energy band gap discontinuity is formed on the p-type semiconductor layer prior to the formation of the l-type semiconductor layer. For improvement, a diffusion prevention layer such as SiC is formed.

[Problem to be solved by the invention]

However, such conventional elements have a problem in that the diffusion prevention effect against dopants such as boron is not sufficient and they lack thermal stability.

The present invention has been made in view of the above circumstances, and its object is to provide a photovoltaic element that can achieve a high dopant diffusion prevention effect.

[Means to solve the problem]

In the photovoltaic device according to the present invention, in the photovoltaic device having at least one set of pin structures, two or more anti-diffusion layers are provided between the p-type semiconductor layer and the l-type semiconductor layer. It is characterized by:

[Function] According to the present invention, the diffusion prevention layer is thermally stable even when forming an i-type semiconductor layer, and prevents dopant diffusion.

[Example 1] The present invention will be specifically described below based on drawings showing examples thereof.

FIG. 1 is a cross-sectional structural diagram of Example 1 of the present invention, in which a transparent electrode 2 is formed on the surface of a transparent substrate l such as glass. 3. An amorphous silicon semiconductor layer (hereinafter simply referred to as an i-type semiconductor layer) 7. An n-type amorphous silicon semiconductor layer (hereinafter simply referred to as an n-type semiconductor layer) 8. A back electrode. 9 are laminated in this order.

The interface layer 4 has a superlattice structure having a plurality of SiN layers. Table 1 shows an example of the conditions for forming the SiN layer.

Table 1 Note that N may be used instead of NH3 as the nitrogen source. Nil! The supply amount is 10sec105e/5iH
4=0.5), and s/5i of the interface layer was set to 5.

The formation conditions, the calendar number of each layer, the film thickness, etc. are not limited and may be set as necessary.

A comparison of the boron diffusion element functions of amorphous SiN and amorphous SiC is as shown in FIG. Second
The figure shows the IMA profile of boron after constructing a solar cell using a photovoltaic element with the structure shown in Figure 1 and thermally annealing it at 250°C for 5 hours. Time (hours) is shown, and boron concentration is plotted on the vertical axis.

As is clear from this graph, the concentration of boron is significantly reduced when SiN is used compared to SiC, in other words, the effect of preventing boron diffusion is greater.

[Example 2] FIG. 3 is a cross-sectional structural diagram of Example 2 of the present invention, in which a transparent electrode 2. p-type semiconductor layer 3
．． Amorphous SiN which is the interface layer 7! ! 14° amorphous SiC layer 15. Further, an i-type semiconductor layer Ln-type semiconductor layer 8. The back electrode 9 is laminated in this order.

Amorphous SiN layer 14 and amorphous 5iCJi1
The stacking order with 5 is that amorphous Si is placed on the p-type semiconductor layer 3 side.
The N layer 14 also has an amorphous layer 5i on the i-type semiconductor layer 7 side.
CIJ15 may be located.

It has been confirmed that similar effects can be obtained by using a graded SiC layer or an i-type semiconductor layer with many 5i-Hz bonds.

When this was constructed as a solar cell, the initial photoelectric conversion efficiency was 8.5%. Further, a heat resistance test was conducted to thermally anneal the material at 250° C. and measure the change in photoelectric conversion efficiency, and the results shown in FIG. 4 were obtained.

FIG. 4 shows annealing time (hours) on the horizontal axis and charge conversion efficiency (%) on the vertical axis. In the graph, the results plotted with O marks are the results for the device of the present invention, and the results plotted with Δ marks are the results for the conventional device. As is clear from this graph, when the annealing time exceeds 1 hour, the photoelectric conversion efficiency (%) of the conventional device rapidly decreases, in other words, the diffusion of boron into the i-type semiconductor layer rapidly increases. It can be seen that while the characteristics as a solar cell are deteriorated, the characteristics of the device of the present invention are maintained for a long time although some deterioration is observed.

(Example 3) FIG. 5 is a cross-sectional structural diagram of Example 3 of the present invention, in which a transparent electrode 2, a p-type semiconductor layer 3, a transparent electrode 2, a p-type semiconductor layer 3, etc.
．． Amorphous Si0 layer 24° amorphous SiN layer 25. which is an interface layer. Amorphous SiC layer 26° further i
type semiconductor N7. n-type semiconductor layer 8. The back electrodes 9 are formed by laminating them in this order.

Note that SiN is the ratio of N to Si, that is, N/S
The component composition is i=0.5 (=50%) or more. When the photovoltaic device of Example 3 was used as a solar cell, the initial preemptive conversion efficiency was 9%.

FIG. 6 is a graph showing the relationship between N/Si and photoelectric conversion efficiency, with N/Si (%) plotted on the horizontal axis and photoelectric conversion efficiency (%) plotted on the vertical axis. The O mark in the graph plots the thickness of the SiN layer for 100 people, and Δ
Plotted with marks is the case where the thickness of the SiN layer is 50 mm, and shows the results after thermal annealing at 250° C. for 3 hours. As is clear from this graph, it can be seen that higher photoelectric conversion efficiency than the conventional element is obtained when N/5i=5% or more.

In addition, in the above-mentioned Examples 1 to 3, the case of a pin-type amorphous silicon photovoltaic element was explained.
Of course, the present invention can also be applied to nip type amorphous silicon photovoltaic elements.

〔Effect of the invention〕

As described above, in the device of the present invention, two or more dopant diffusion prevention layers are interposed between the p-type semiconductor layer and the l-type semiconductor layer, so that the diffusion prevention effect is reliable and the heat resistance is high. The present invention has excellent effects such as improved performance and improved reliability.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional structural diagram of Example 1 of the present invention, and FIG.
Graph showing the boron diffusion prevention effect of N and SiC, 3rd
FIG. 4 is a graph showing thermal annealing time and photoelectric conversion efficiency. FIG. 5 is a cross-sectional structure diagram showing Example 3 of the present invention. FIG. N/S
It is a graph showing the relationship between i and photoelectric conversion efficiency after thermal annealing. l... Transparent substrate 2... Transparent electrode 3... P-type semiconductor layer 4... Interface layer 7... L-type semiconductor layer
8...N-type semiconductor layer patent Applicant: Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A photovoltaic device having at least one set of pin structures, characterized in that two or more anti-diffusion layers are provided between a p-type semiconductor layer and an i-type semiconductor layer.