JPS63200576A - Solar cell - Google Patents

Abstract

PURPOSE:To raise the efficiency of a solar cell by absorbing a light of a wavelength range having low photoelectric conversion efficiency in a photoelectric conversion layer, and forming a wavelength converter layer for irradiating a light of a wavelength range having high photoelectric conversion efficiency in parallel with the photoelectric conversion layer. CONSTITUTION:A solar light incident to a reflection preventive film 1 is incident to a wavelength converter layer 3 through the film 1 and a transparent protective cover 2. The wavelengths of the incident light range over 0.3-5mum. Of them, the light of 0.3-0.5mum of wavelength having low photoelectric conversion efficiency is absorbed by the layer 3, converted to the wavelength of 0.5-0.6mum to be irradiated. The light having the wavelength of 0.5mum or longer not absorbed by the layer 3 is transmitted as it is through the layer 3, a transparent adhesive 4 and a transparent electrode 5 to be incident to a photoelectric conversion layer 6 formed in parallel with the layer 3 to be converted to power. The light having the wavelength of 0.5-0.6mum irradiated from the layer 3 is radiated from a light irradiation point in all directions and incident to the layer 6 to be converted to power.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to solar cells, and in particular to solar cells that utilize wavelength conversion and are suitable for efficiently converting sunlight in a wide spectral range into electricity. Regarding batteries.

[Conventional technology]

Conventional LA battery using wavelength conversion
5675), as shown in FIG.
are arranged, the wavelength of external light such as sunlight is converted by the glass plate 8, and the condensed light is incident on the solar cell element 9 to be converted into electric power.

[Problem that the invention seeks to solve]

Although the above-mentioned conventional technology can reduce the area of the solar cell element required for unit electric output, the conversion efficiency of the entire thick pond including the phosphor-containing glass plate is not high. In other words, considering the absorption and emission characteristics of the phosphor, when the external light is sunlight, the proportion of sunlight energy that can be focused on the end face of the plastic plate containing the phosphor is at most the amount of incident solar energy. It is 10 to 20 inches. Therefore, even if the efficiency of the solar cell element is 30q6, only 3 to 6qb of incident solar energy can be converted into electricity. Therefore, in the above conventional technology, the power conversion efficiency per unit area of the plastic plate is low, and the area of the entire solar cell including the phosphor-filled plastic plate required for unit electric output is large. .

An object of the present invention is to provide a solar cell with high efficiency per unit area.

[Failure to solve the problem]

The solar cell of the present invention has a wavelength converter (fluorescent material) on the light incidence side of the photoelectric conversion layer that absorbs light in a wavelength range where the photoelectric conversion efficiency is low and emits light in a wavelength range where the photoelectric conversion efficiency is high. The % mark is that the layer of photoelectric material) is provided in parallel with the photoelectric conversion layer.

[Operation] Figure 3 shows the sunlight spectrum and the wavelength dependence of the photoelectric conversion efficiency of the photoelectric conversion layer. As shown in the figure, the photoelectric conversion efficiency is only high in a certain wavelength range of the sunlight spectrum.

However, in the present invention, a layer of a wavelength converter having an absorption wavelength in a wavelength range where photoelectric conversion efficiency is low and an emission wavelength in a wavelength range where photoelectric conversion efficiency is high is provided on the light incident side of the photoelectric conversion layer. As a result, light in the wavelength range that could not contribute to photoelectric conversion can now effectively contribute to photoelectric conversion.
Efficiency per unit area increases with respect to incident sunlight.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. 1st
The figure is a cross-sectional view showing the structure of the solar cell of this example.

In FIG. 1, an antireflection film 1, a transparent protective cover (glass) 2, a wavelength converter N3, a transparent adhesive 4, a transparent electrode 5
, the photoelectric conversion layer 6, and the back electrode 7 are sequentially logged in layers. In this embodiment, ZnS is used as the layer 3 of the wavelength converter and is deposited on the transparent protective cover 2. Also,
As the photoelectric conversion layer 6, a polycrystalline St PN junction element was used. This PN junction element has the ability to convert light with a wavelength of 0.5 to 1.0 μm into electric power.

The sunlight incident on the antireflection film 1 passes through the antireflection film 1 and the transparent protective cover 2 and enters the layer 3 of the wavelength converter.

The wavelength of this incident sunlight ranges from 0.3 to 5 μm, and among this, the light with a wavelength of 0.3 to 0.5 μm is absorbed by the layer 3 of the wavelength converter and becomes a wavelength of 0.5 to 0.6 μm. It is converted and emits light.

Light with a wavelength of 0.5 μm or more that is not absorbed by the wavelength converter layer 3 passes through the wavelength converter layer 3, the transparent adhesive 4, and the transparent electrode 5, enters the photoelectric conversion layer 6, and generates electric power. is converted to The transparent adhesive 4 is a wavelength converter fVi
3 and the transparent FiAt pole 5 to reduce reflections at the interface.

The light with a wavelength of 0.5 to 0.6 μm emitted from the layer 3 of the wavelength converter is radiated in all directions from the light emitting point, but the light emitted from the layer 3 of the wavelength converter
The light emitted to the side directly enters the photoelectric conversion layer 6 and is converted into electric power. In addition, a part of the light emitted toward the transparent protective cover 2 is reflected at the interface between the antireflection film 1 and the transparent protective cover 2, the interface between the antireflection film 1 and the outside, etc., and is reflected by the photoelectric conversion layer 6. incident and converted into electric power.

The converted power is extracted to the outside through the transparent electrode 5 and the back electrode 7.

In this example, light at the short wavelength (0.3 to 0.5 μm) side (approximately 7% of solar energy), which has not been used for photoelectric conversion, is converted to light at a long wavelength (0.5 μm) that can be used for photoelectric conversion. ~0
．． 6 μm) side and input it to the photoelectric conversion layer 6,
And the wavelength range originally usable for photoelectric conversion (0.5~
1.0μtn) (approximately 40% of solar energy) is directly incident on the photoelectric conversion layer 6, so even if the light in the wavelength range that can be used for photoelectric conversion is predetermined with loss during the process, the light (approximately 40% of solar energy) is .1 times or more. Therefore, the efficiency of the solar cell of this example is improved by about 10% or more compared to the conventional solar cell.

As explained above, in this embodiment, both light in the wavelength range conventionally used for photoelectric conversion and light in a part of the wavelength range that has not been used can be used for photoelectric conversion at the same time. This has the effect of improving efficiency.

FIG. 4 is a sectional view of a solar cell panel showing another embodiment of the present invention. In the figure, transparent electrode 5° photoelectric conversion layer 6
(The material is the same as that of the photoelectric conversion layer 6 of the above embodiment), and a plurality of solar cell elements each consisting of a back electrode 7 are arranged, and these solar cell elements are made of a bed of fine powder of a wavelength converter such as ZnS. It is optically adhered to the transparent protective cover 2 by a transparent adhesive 10. Further, the back surfaces of these solar cell elements are insulated by an insulating cover 11.

In this example, the effect of improving solar cell efficiency is the same as in the previous example. Moreover, in this embodiment, since the fine powder of the wavelength converter is dispersed and mixed into the transparent adhesive and integrated, the assembly process of the solar cell panel is almost unchanged from the conventional one. Therefore, manufacturing costs do not increase.

A similar effect can be obtained by dispersing and mixing fine powder of the wavelength converter into the transparent protective cover.

FIG. 5 is a sectional view of a solar cell showing another embodiment of the present invention. The basic structure of this embodiment is the same as that of the embodiment shown in FIG. 1, and only the different parts will be explained. That is, in this embodiment shown in FIG. 5, the layer 3 of the wavelength converter shown in FIG.
etc.) layer 31, and an antis layer 31 that performs the reverse wavelength conversion to the above)
-X type wavelength converter (YbEr, YbTm, etc.)
It has a two-layer structure with a layer 32. The layer 31 of the Stokes-type wavelength converter converts wavelengths of 0.00 to 0.00000, which could not be used for photoelectric conversion.
Converts short wavelength light of 5 μm or less into long wavelength light that can be used for photoelectric conversion. The anti-Stokes type wavelength converter converts light with a wavelength of 1°0 μm or more, which was previously too long to be used for photoelectric conversion, to a wavelength of 1.0 μm that can be used for photoelectric conversion.
Convert to the following wavelengths. Therefore, in this embodiment, both short wavelength light and long wavelength light of sunlight, which could not be used conventionally, can be used for photoelectric conversion, which has the effect of further improving efficiency. .

In carrying out the present invention, a wavelength converter that absorbs short wavelength light and emits long wavelength light is ZnS:Ag(30
(absorbs light of 0 to 400 nm and emits light of 400 to 500 nm), ZnS:Cu (300 to 450 nm)
(which absorbs light of 450 to 600 nm and emits light of 450 to 600 nm) can be cited as suitable examples.

When forming a layer of wavelength converter on the back surface of a transparent protective cover (glass) by vacuum evaporation or gas phase reaction method, the thickness of the layer is determined by experiments depending on the absorption rate of the wavelength converter. Although the thickness is set, normally several micrometers to several tens of micrometers is appropriate. When forming a layer of wavelength converter by mixing fine phosphor powder into a transparent adhesive, the optimum concentration can be determined through experiments, etc.
It is appropriate to mix it at a concentration of f/an''.

Regarding the material and thickness of the photoelectric conversion layer, single-crystal silicon solar cells: 50 μm to 300 μm thick, gallium-arsenide solar cells: 50 μm to 200 μm thick, or amorphous silicon solar cells: several μm thick. is appropriate.

A transparent electrode is not necessarily required in single-crystal silicon or gallium-arsenide solar cells, and may be a grid electrode. Transparent electrodes are necessary in amorphous silicon solar cells. The material of the transparent electrode may be SnO2 or ITO (indium tin oxide).

〔Effect of the invention〕

According to the present invention, in addition to sunlight in the conventionally used wavelength range, light in the wavelength range that was previously unusable can be converted into a usable wavelength range and used. Efficiency can be improved by 10% or more.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a solar cell according to an embodiment of the present invention, FIG. 2 is an external view of a conventional solar cell, and FIG. 3 is a diagram showing the sunlight spectrum and the wavelength dependence of the photoelectric conversion efficiency of the photoelectric conversion layer. The figure shown,
FIG. 4 is a sectional view of a solar cell according to another embodiment of the present invention, and FIG.
The figure is a sectional view of a solar cell according to still another embodiment of the present invention. 1...Anti-reflection film 2...Transparent protective cover 3.
31.32... Layer of wavelength converter 4... Transparent adhesive 5... Transparent electrode 6... Photoelectric conversion layer 7... Back electrode Figure 1 Figure 2 Figure 3 Wavelength (PL)

Claims (1)

[Claims] 1. A wavelength converter on the light incidence side of the photoelectric conversion layer that absorbs light in a wavelength range where the photoelectric conversion efficiency is low in the photoelectric conversion layer and emits light in a wavelength range where the photoelectric conversion efficiency is high. A solar cell characterized in that a layer is provided in parallel with a photoelectric conversion layer. 2. The solar cell according to claim 1, wherein the wavelength converter layer is sandwiched between the photoelectric conversion layer and the transparent protective cover. 3. The layer of the wavelength converter consists of a transparent protective cover in which fine powder of the wavelength converter is dispersed and mixed. Claim 1
Solar cells described in section. 4. The solar cell according to claim 1, wherein the wavelength converter layer is formed by dispersing fine wavelength converter powder in a transparent adhesive layer between the photoelectric conversion layer and the transparent protective cover. .