JP2001094129A - CdS/CdTe SOLAR CELL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high performance CdS/CdTe solar cell by enlarging the photoelectrically convertible wavelength range. SOLUTION: A CdS film 3 and a CdTe film 4 are formed sequentially on one side of a transparent glass substrate 2, an AgIn film 7 is formed on the CdS film, while a current collector film 5 and an AgIn film 6 are formed on the CdTe film 4, and a film 1 containing a fluorescent substance an absorbing light, having a wavelength shorter than 510 nm and an emitting light having wavelength of 510 nm or longer is formed on the other side of the transparent glass substrate 2 to produce a CdS/CdTe solar cell. Since photoelectrically unconvertible light having wavelength of shorter than 510 nm is converted through the wavelength converting action of the fluorescent substance into photoelectrically convertible light, optical energy of a light source can be photoelectrically converted effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a CdS / CdTe
Regarding high performance of solar cells.

[0002]

2. Description of the Related Art In recent years, CdS / CdTe solar cells have become widespread as power sources for small consumer devices such as calculators and automobile accessories.

In this CdS / CdTe solar cell, a CdS film and a CdTe film are sequentially formed on one surface of a transparent glass substrate by applying and sintering a paste containing each material, and then a positive electrode is formed on the CdTe film. , Formed by forming a negative electrode on a CdS film (for example, see JP-A-7-30).
137). In this CdS / CdTe solar cell, 5
Light having a wavelength of 10 nm to 860 nm is incident on a CdS / CdTe junction, which is a photoelectric conversion layer of a solar cell, and is photoelectrically converted. That is, light having a wavelength of less than 510 nm is not photoelectrically converted. If the light having a wavelength of 510 nm or less can be photoelectrically converted, the photoelectric conversion efficiency of the solar cell increases, which leads to an improvement in performance.

In order to improve the performance of the CdS / CdTe solar cell, it has been proposed to reduce the thickness of the CdS film to 0.1 μm or less to photoelectrically convert light having a wavelength of 510 nm or less to improve the performance. (See, for example,
-31826 gazette).

[0005]

However, the above-mentioned conventional configuration has a problem, and the solar cell performance is not sufficiently improved.

In a CdS / CdTe solar cell proposed in Japanese Patent Application Laid-Open No. 11-31826 and the like in which the thickness of the CdS film is set to 0.1 μm or less, the film resistance is increased by making the CdS film thinner. In order to prevent this adverse effect, it is necessary to newly form a transparent conductive film between the glass substrate and the CdS film. However, the transparent conductive film is expensive and has a problem of high cost. Further, C
It is difficult to reduce the thickness of the dS film uniformly,
Pinholes are likely to be generated in the dS film, and there is also a problem that the yield is deteriorated when manufacturing a large-area solar cell.

Further, a film of a fluorescent substance is formed on the light-receiving surface of the solar cell, and the wavelength conversion function of the fluorescent substance is used to extend the wavelength range of light that can contribute to photoelectric conversion to the shorter wavelength side to improve the performance. Although proposals to be made are made in Japanese Patent Application Laid-Open No. 6-31074 and the like, they are for silicon-based solar cells, and there is no specific description about CdS / CdTe solar cells having different absorption wavelengths.

The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide an inexpensive and high-performance CdS / CdTe solar cell.

[0009]

In order to solve the above-mentioned problems, a CdS / CdTe solar cell according to the present invention has a CdS film and a CdTe film sequentially formed on one surface of a transparent glass substrate, and a negative electrode is formed on the CdS film. An electrode is formed by forming a positive electrode on the CdTe film and further forming a positive electrode on the other surface of the transparent glass substrate.
A film containing a fluorescent substance that absorbs and excites with light having a wavelength of less than 0 nm and emits light with a wavelength of 510 nm or more is formed. According to the above configuration, the wavelength conversion function of the fluorescent substance can be used to widen the wavelength range of light that can be photoelectrically converted to a shorter wavelength side, thereby achieving higher photoelectric conversion efficiency. This is because light having a wavelength of less than 510 nm, which could not be photoelectrically converted by a conventional CdS / CdTe solar cell, can be photoelectrically converted.
Since it is converted into light having a wavelength of 10 nm or more and is incident on a CdS / CdTe junction, which is a photoelectric conversion layer of a solar cell, the wavelength range of light that can be substantially photoelectrically converted can be extended to a shorter wavelength side of less than 510 nm It is. Therefore,
A high-performance CdS / CdTe solar cell with improved photoelectric conversion efficiency can be obtained.

[0010]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a CdS film and a CdTe film are sequentially formed on one surface of a transparent glass substrate.
A CdS / CdTe solar cell in which a negative electrode is formed on a dS film and a positive electrode is formed on the CdTe film, and the other surface of the transparent glass substrate is excited by absorption with light having a wavelength of less than 510 nm.
A film containing a fluorescent substance that emits light having a wavelength of 10 nm or more is formed. With such a configuration, CdS / Cd
The wavelength range of light that can be photoelectrically converted by the Te solar cell is extended to the shorter wavelength side, and the light energy of the light source can be more effectively converted to electric energy, so that high photoelectric conversion efficiency can be achieved and high performance CdS / CdTe solar cell can be obtained.

510 nm for CdS / CdTe solar cells
Light having a wavelength of ８860 nm is incident on a CdS / CdTe junction, which is a photoelectric conversion layer of a solar cell, and is photoelectrically converted. The sensitivity at which photoelectric conversion is performed with respect to this wavelength is referred to as spectral sensitivity.
m shows a gentle normal distribution curve with a peak, and the spectral sensitivity of the amorphous silicon
It draws a gentle normal distribution curve with a peak at 50 nm, and does not show extreme spectral sensitivity. On the other hand, CdS / C
The spectral sensitivity of the dTe solar cell is 510 nm to 8
Very high sensitivity is obtained at 60 nm, and little else is photoelectrically converted. For this reason, converting the wavelength of less than 510 nm that has not been subjected to photoelectric conversion into a wavelength region where photoelectric conversion is performed will greatly contribute to improving photoelectric conversion efficiency.

According to the structure of the present invention, light having a wavelength of less than 510 nm, which could not be photoelectrically converted conventionally, is converted into light of a wavelength of 510 nm or more that can be photoelectrically converted. , The wavelength range of light that can be substantially photoelectrically converted is 5
It can be extended to shorter wavelengths of less than 10 nm. This increases the photoelectric conversion efficiency of the solar cell, leading to an improvement in solar cell performance.

In particular, since the emission spectrum of a white fluorescent lamp used indoors has a large spectrum intensity at a wavelength of less than 510 nm, its use for indoor CdS / CdTe solar cells is highly effective and preferable.

Further, the thickness of the CdS film is preferably 0.5 μm or more. When the thickness of the CdS film is sufficiently large, light having a wavelength of 510 nm or less having energy having a band gap of 2.4 eV or more is not absorbed and reaches the CdS / CdTe junction where photoelectric conversion is performed. Cannot contribute to photoelectric conversion. However, Cd
When the thickness of the S film becomes 0.5 μm or less, the wavelength 510 nm
The following light passes through the CdS film and contributes to photoelectric conversion, and spreads from a wavelength range of 510 to 860 nm where photoelectric conversion can be performed to a short wavelength range. In such a case, even if a film containing a fluorescent colorant is formed on the light receiving surface of the solar cell as in the present invention, the effect cannot be sufficiently obtained. Accordingly, the thickness of the CdS film is preferably 0.5 μm or more.

Preferably, the CdS film is a film formed by applying and sintering a paste containing CdS powder as a main component. According to this method, a uniform film having a large area can be obtained, and further, patterning can be easily performed.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Example 1 An indoor CdS / CdTe solar cell mainly using a fluorescent lamp and an incandescent lamp as a light source was manufactured. FIG. 1 shows a cross section of a basic CdS / CdTe solar cell of the present invention. On one surface of the transparent glass substrate 2, a CdS film 3 and a CdTe film 4 are formed in this order, and the CdTe film 4 has a current collector film 5 and a AgI serving as a positive electrode.
An n film 6 is formed, and an AgIn film 7 serving as a negative electrode is formed on the CdS film 3. A phosphor film 1 is formed on the other surface of the transparent glass substrate 2, which is a light receiving surface of the solar cell.

The CdS film is made of a CdS paste obtained by dispersing a CdS powder and a CdCl ₂ powder in a mixed solution of propylene glycol and water at a weight ratio of 4: 1 at a weight ratio of 100: 12: 30. After printing on a glass substrate and drying, it was heated under a nitrogen gas flow at 690 ° C. for about 60 minutes to perform sintering.

The CdTe film is a CdTe paste obtained by pulverizing Cd and Te in water, and dispersing a dried powder and dCl ₂ powder in ethylene glycol monophenyl ether at a weight ratio of 100: 0.5: 30. Is printed on a CdS film formed on a transparent glass substrate, dried, and then dried.
It was manufactured by heating under a nitrogen gas stream at 20 ° C. for about 20 minutes to perform a sintering process.

In this embodiment, four basic cells each composed of a CdS film, a CdTe film, a current collector film and an AgIn film are connected in series to a glass substrate by printing patterning.
CdTe solar cells were used. The thickness of the CdS film is 8 to 10
μm, and the thickness of the CdTe film is 15 to 20 μm.

The CdS / CdTe thus prepared
A fluorescent substance was applied to the light receiving surface of the transparent glass substrate of the solar cell to form a fluorescent substance film, and a solar cell A according to an example of the present invention was manufactured. The fluorescent substance is a fluorescent colorant (MPI-505C manufactured by Nippon Fluorescent Chemical Co., Ltd.), which is mixed with an epoxy resin and butyl carbitol to form a paste.
A fluorescent material film was formed by applying and drying the light receiving surface of the transparent glass substrate of the solar cell. As a comparative example, a solar cell without a fluorescent material film was prepared, which was used as a conventional solar cell X. The spectral spectral sensitivities of the solar cell A of the present invention and the conventional solar cell X were measured by using YQ- manufactured by JASCO Corporation.
It measured using the 250CW type constant output energy spectrometer. This is to express spectral spectral sensitivity by irradiating light with a fixed font and measuring a current value flowing thereby.

FIG. 2 shows the results of measuring the absorption excitation spectrum and the fluorescence emission spectrum of this fluorescent colorant. It is excited by light having a wavelength range of 350 to 500 nm and emits fluorescence having a wavelength range of 450 to 600 nm.

FIG. 3 shows the result of measuring the spectral sensitivity of the solar cell. The horizontal axis represents wavelength, and the vertical axis represents spectral sensitivity in photocurrent. (A) is a conventional solar cell X in which a fluorescent material film is not formed.
Light in the wavelength range of 60 nm is photoelectrically converted. on the other hand,
(B) is a solar cell A of the present invention in which a phosphor film having a thickness of 10 μm is formed, and photoelectrically converts light in the wavelength range of 350 to 500 nm in addition to the wavelength range of 510 to 860 nm. This is due to the fact that the fluorescent colorant
Is converted to light having a wavelength range of 450 to 600 nm, and light having a wavelength of 510 nm or more is converted to CdS.
This is because photoelectric conversion is performed at the junction of / CdTe.

Further, the thickness of the fluorescent material film is set to 0, 3, 10,
The photovoltaic conversion characteristics of these solar cells were measured using a white fluorescent lamp (illuminance of 200 lux) and a daylight fluorescent lamp (illuminance of 200 lux) as light sources. The results are shown in (Table 1).

[0025]

[Table 1]

From the results shown in Table 1, the thickness of the fluorescent material film was changed from 0 μm (no fluorescent material film was formed) to 3 μm, 10 μm.
It can be seen that the short circuit current increases by setting m and 20 μm, and as a result, the maximum output increases.

This is because the emission spectra of the white fluorescent lamp and the daylight fluorescent lamp are spread even in a wavelength range shorter than the wavelength range of 510 to 860 nm in which the photoelectric conversion of the conventional CdS / CdTe solar cell can be performed. 510
This is because light of a portion smaller than nm can be effectively photoelectrically converted by forming the fluorescent material film.

Example 2 An outdoor CdS / CdTe solar cell mainly using outdoor light as a light source was manufactured. The basic CdS / CdTe solar cell has the same structure as the indoor one of Example 1, and was manufactured by the same method.

In this embodiment, eight CdS / Cd cells are connected in series to a glass substrate by printing patterning of a basic cell composed of a CdS film, a CdTe film, a current collector film and an AgIn film.
A dTe solar cell was used. The thickness of the CdS film is 15 to 20
μm. A fluorescent substance was applied to the light receiving surface of the transparent glass substrate of the CdS / CdTe solar cell to form a fluorescent substance film, thereby manufacturing a solar cell B according to the embodiment of the present invention. The fluorescent substance is a fluorescent colorant (MPI-5 manufactured by Nippon Fluorescent Chemical Co., Ltd.)
05C), which was mixed with an epoxy resin and butyl carbitol to form a paste, and applied to the light-receiving surface of a transparent glass substrate of a solar cell and dried to form a fluorescent material film. As a comparative example, a solar cell without a fluorescent material film was prepared, and was used as a conventional solar cell Y. The spectral sensitivities of the solar cell B of the present invention and the conventional solar cell Y were measured in the same manner as in Example 1.

FIG. 4 shows the result of measuring the spectral sensitivity of the solar cell. The horizontal axis represents wavelength, and the vertical axis represents spectral sensitivity in photocurrent. (A) is a conventional solar cell Y without forming a fluorescent material film,
Light in the wavelength range of 60 nm is photoelectrically converted. on the other hand,
(B) is a solar cell B of the present invention in which a phosphor film having a thickness of 10 μm is formed, and photoelectrically converts light in a wavelength range of 350 to 500 nm in addition to a wavelength range of 510 to 860 nm.

In addition, simulated sunlight (irradiation energy: 1 k
W / m ² ) as a light source, and the photoelectric conversion characteristics of the solar cell were measured. The results are shown in (Table 2).

[0032]

[Table 2]

From the results shown in Table 2, it can be seen that the short-circuit current is increased by setting the thickness of the fluorescent material film to 10 μm as compared with the case where no fluorescent material film is formed, and as a result, the maximum output is increased.

This is because light in a wavelength range shorter than 510 to 860 nm, which can be photoelectrically converted in a conventional CdS / CdTe solar cell, can be effectively photoelectrically converted by forming a fluorescent material film.

In this embodiment, the CdS film is formed by the coating and sintering method. However, the film is not limited to the coating and sintering method, but may be formed by a method such as vapor deposition or electrodeposition.

The fluorescent colorant as the fluorescent substance used in the examples is excited by light having a wavelength range of 350 to 500 nm and emits fluorescence having a wavelength range of 450 to 600 nm, and is used for photoelectric conversion of CdS / CdTe solar cells. Although it is convenient to extend the wavelength range that can be achieved, the material is not limited to this, and any material that is excited by light having a wavelength of less than 510 nm and emits fluorescence with a wavelength of 510 nm or more, regardless of the material of the fluorescent substance, can be used as a CdS / CdTe solar cell. By forming a fluorescent substance film on the light receiving surface of the battery, the performance of the CdS / CdTe solar cell can be improved.

In the amorphous silicon solar cell, the wavelength range in which photoelectric conversion can be performed has a peak at around 500 nm and extends to around 300 nm on the short wavelength side. Even if it is formed on a surface, it cannot be expected to improve the performance like a CdS / CdTe solar cell.

[0038]

As described above, according to the present invention, CdS /
By forming a film containing a fluorescent substance that absorbs and excites light having a wavelength of less than 510 nm and emits light having a wavelength of 510 nm or more on the light receiving surface of the CdTe solar cell, CdS / CdTe is formed.
Higher performance of the solar cell can be achieved. Further, the method can be implemented by an inexpensive and simple method of forming a film containing a fluorescent substance on the light receiving surface without changing the conventional method of manufacturing a CdS / CdTe solar cell.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional configuration of a basic CdS / CdTe solar cell according to an embodiment of the present invention.

FIG. 2 is a diagram showing an absorption excitation spectrum and an emission spectrum of the fluorescent colorant used in this example.

FIG. 3 (a) is a diagram showing the spectral spectral sensitivity of a conventional indoor CdS / CdTe solar cell; and (b) is a diagram showing the spectral spectral sensitivity of an indoor CdS / CdTe solar cell of the present embodiment.

FIG. 4 (a) is a diagram showing the spectral spectral sensitivity of a conventional CdS / CdTe solar cell for outdoor use; FIG. 4 (b) is a diagram showing the spectral spectral sensitivity of an outdoor CdS / CdTe solar cell of the present embodiment;

[Explanation of symbols]

 Reference Signs List 1 fluorescent substance film 2 transparent glass substrate 3 CdS film 4 CdTe film 5 current collector film 6 AgIn film (positive electrode) 7 AgIn film (negative electrode)

Claims (3)

[Claims] 1. A CdS / CdT film in which a CdS film and a CdTe film are sequentially formed on one surface of a transparent glass substrate, a negative electrode is formed on the CdS film, and a positive electrode is formed on the CdTe film.
An e-solar cell, wherein a film containing a fluorescent substance that absorbs and excites with light having a wavelength of less than 510 nm and emits light having a wavelength of 510 nm or more is formed on the other surface of the transparent glass substrate. CdTe solar cells. 2. The CdS / CdTe according to claim 1, wherein said CdS film has a thickness of 0.5 μm or more.
Solar cells. 3. The CdS / CdTe solar cell according to claim 1, wherein the CdS film is a film formed by applying and sintering a paste containing CdS powder as a main component.