JP2007251114A - Substrate for high-performance solar cell having optical multi-layer film, and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a solar cell substrate of high-power generation efficiency, by preventing power generation efficiency from deteriorating due to the rise in the temperature under strong sunlight, in the substrate for solar cell. <P>SOLUTION: On a light-receiving surface on which the sunlight is made incident of the solar cell substrate, a multi-layer film which has high absorption characteristics with respect to the sunlight having the wavelength in a sensitivity region of high sunlight spectral density, and has reflection characteristics with respect to the sunlight of the wavelength, in a sensitivity region where the sunlight spectral density deteriorates, is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solar cell substrate having an optical multilayer film capable of high-efficiency power generation on a solar light receiving surface.

Technical background

  In a solar cell substrate that receives sunlight and generates electric power by photoelectric conversion, as one technique for increasing the power generation efficiency, a silicon nitride (SiN) film is formed on the surface of the light receiving surface, so that sunlight can be used as an antireflection film. Power generation efficiency is improved by preventing reflection and reducing the loss of sunlight incident due to reflection. In order to further increase the efficiency, a textured shape with an uneven surface has been developed.

However, the conventional crystalline solar cells have a drawback in that the power generation capacity decreases in summer when the temperature is weak and the temperature rises.
Further, the silicon nitride (SiN) film has a transmittance of 90% or more in the wavelength region of 550 nm to 1000 nm, and a high antireflection effect is obtained. However, in the range of 400 nm to 500 nm, which is a part of the sensitivity region where the sunlight spectral density is high, which is photoelectrically converted, the transmittance is reduced, the reflection of sunlight is increased, and the power generation efficiency is lowered. Further, in the infrared region of 1000 nm or more, the transmittance of sunlight is 80% or more, and the absorption factor in the long wavelength region is high. In particular, the solar cell substrate is absorbed by the sunlight in the infrared region absorbed during the daytime in summer. Is heated, which is disadvantageous for power generation capacity.

As a measure for improvement, a multilayer film having a characteristic that a transmittance of 95% or more is obtained in a wavelength region from about 400 nm to about 1100 nm, and the transmittance is lowered and the reflectance is increased in a long wavelength region of about 1100 nm or more. Is formed on the solar light receiving surface of the substrate for solar cells, so that the absorption efficiency of sunlight is increased in the advantageous sensitivity band of photoelectric conversion, and the sunlight in the wavelength band in the infrared region, which is a long wavelength, is reflected. Thus, a solar cell substrate with high power generation efficiency can be obtained by preventing a temperature rise of the solar cell substrate and suppressing a decrease in power generation capacity.
JP-A-2005-244073 Industrial Materials January 2006 (Vol.54 No.1)

  The problems to be solved are as wide as possible for the sensitivity region where the solar spectrum density is high, and the point that the power generation efficiency decreases due to the temperature rise under intense sunlight, which was a drawback of the prior art. It is the point which raises the transmittance of sunlight in the range.

  The solar cell substrate increases the absorption of sunlight in a high sensitivity region (for example, about 450 nm to about 11000 nm) where the solar spectrum density is photoelectrically converted with high efficiency, and in the long wavelength infrared region (for example, about 1100 nm or more) Reflecting light is the main feature.

  The solar cell substrate of the present invention enhances the absorption of sunlight in the sensitive region with high optical spectral density, and reflects the sunlight in the long wavelength infrared region where the temperature of the solar cell substrate rises, There is an advantage that the temperature rise of the solar cell substrate can be suppressed and the power generation efficiency can be increased.

An example of film formation by plasma CVD is shown. TiO2 is used as the high refractive index material, and SiO2 is used as the low refractive index material. As deposition conditions for TiO2, H4TiO4 heating is used as a source gas, and the temperature on the substrate is set to 250C to 400C. SiH4 + oxygen is used as the SiO2 vapor deposition source gas. The film structure is eight layers of Si (Sub) / TiO2 / SiO2 / TiO2 / SiO2 / SiO2 / TiO2 / SiO2 / TiO2 / SiO2. The film thicknesses are 71.8 nm / 133.2 nm / 6 nm / 74.6 nm / 144.3 nm / 224.79 nm / 139.6 nm / 11.59 nm.
FIG. 1 shows spectral transmission characteristics formed on a solar cell substrate by plasma CVD deposition.
FIG. 2 shows spectral reflection characteristics formed on a solar cell substrate by plasma CVD deposition.

An example of film formation by a sputtering method will be shown. Nb2O5 is used as the high refractive index material, and SiO2 is used as the low refractive index material. The substrate temperature is 100 ° C. The film configuration is 14 layers of Si (Sub) / Nb2O5 / SiO2 / Nb2O5 / SiO2. The film thickness is 63.72 nm / 56.71 nm / 17.2 nm / 68.2 nm / 31.4 nm / 15.4 nm / 84.0 nm / 27.48 nm / 17.69 nm / 153.73 nm / 12.4 nm / 31.22 nm /109.09 nm / 95.0 nm.
FIG. 3 shows the spectral transmission characteristics formed on a solar cell substrate by sputtering deposition.
FIG. 4 shows spectral reflection characteristics formed on a solar cell substrate by sputtering deposition.

An example of film formation by electron beam vacuum deposition will be described. An ITO film is formed as the first layer film in the film configuration. By introducing this ITO film, the short-circuit current of the solar battery can be improved. In this embodiment, the substrate temperature is 200 ° C. The film structure is eight layers of Si (Sub) / ITO / SiO2 / TiO2 / SiO2 / TiO2 / TiO2 / TiO2 / SiO2. The film thicknesses are 70.4 nm / 136.9 nm / 11.3 nm / 31 nm / 124.5 nm / 215.86 nm / 138.07 nm / 109.36 nm.
FIG. 5 shows spectral transmission characteristics formed on a solar cell substrate by vacuum evaporation.
FIG. 6 shows spectral reflection characteristics formed on a solar cell substrate by vacuum evaporation.

It is a figure explaining the permeation | transmission characteristic of the multilayer film formed into a film on the board | substrate for solar cells by a plasma CVD vapor deposition method. It is a figure explaining the reflective characteristic of the multilayer film formed into a film on the board | substrate for solar cells by a plasma CVD vapor deposition method. It is a figure explaining the permeation | transmission characteristic of the multilayer film formed into a film on the board | substrate for solar cells by a sputtering method. It is a figure explaining the reflective characteristic of the multilayer film formed into a film on the board | substrate for solar cells by a sputtering method. It is a figure explaining the permeation | transmission characteristic of the multilayer film formed into a film on the board | substrate for solar cells by an electron beam vacuum evaporation method. It is a figure explaining the reflective characteristic of the multilayer film formed into a film on the board | substrate for solar cells by an electron beam vacuum evaporation method.

Claims (4)

  In the sensitivity band with high solar spectral density where the solar cell performs photoelectric conversion on the surface that receives solar light on the substrate for solar battery, the sensitivity that absorbs sunlight and prevents reflection and lowers the solar spectral density. A solar cell substrate, wherein a multilayer film having a characteristic of reflecting sunlight is formed in an infrared region which is a band.   2. The solar cell substrate according to claim 1, wherein the multilayer film formed on the solar light receiving surface is made of a material having a high refractive index and a material having two types of refractive index, a material having a low refractive index. A substrate for a solar battery, which is a multilayer film.   2. The solar cell substrate according to claim 1, wherein the multi-layer film formed on the solar light receiving surface is a multi-layer film made of a material having two or more kinds of refractive indexes.   The solar cell substrate according to claim 1, wherein one of the constituent materials of the multilayer film according to claim 2 or 3 formed on the sunlight receiving surface has a transparent conductive material. Solar cell board to be used.

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