JP2013191697A - Solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell the photoelectric conversion efficiency of which is enhanced, by converting to a wavelength range of high photoelectric conversion efficiency in a photoelectric conversion element, depending on the dispersed wavelength range.SOLUTION: A solar cell 10a includes a spectral element 12a for dispersing sunlight LS (incident light) into first wavelength ranges L3, L4, and a second wavelength range L2, a wavelength conversion element 14a for converting the light in the second wavelength range L2 dispersed by the spectral element 12a into the light in the first wavelength range L1, and a photoelectric conversion element 20 performing photoelectric conversion of the light in the first wavelength range L1.

Description

  The present invention relates to a solar cell with improved photoelectric conversion efficiency when converting sunlight energy into electric power.

  In general, in a solar cell, an excitation substance such as silicon or a compound semiconductor is directly irradiated with sunlight to cause excitation to generate electric energy. However, since the forbidden band width (corresponding to the energy required to cause excitation by separating the charges) is constant, excitation light such as silicon or semiconductor is irradiated with light of energy larger than the forbidden band width. When excess energy is consumed as heat. For this reason, even if the excitation material of the solar cell is irradiated with a large amount of light, the light energy converted into electric energy becomes substantially constant, and the conversion efficiency cannot be increased.

  For example, the forbidden band width of single crystal silicon, which is an example of an excitation substance used in a solar cell, is about 1.1 eV, which corresponds to about 1000 nm in the wavelength of light. When light having a wavelength band of 10,000 nm or less having energy larger than the forbidden band width is irradiated, energy loss due to heat consumption increases. The wavelength of sunlight is widely distributed in the range of 300 to 2000 nm. Further, the intensity of light shows a maximum at around 550 nm. Among such sunlight, it is an important issue to convert short wavelength light (300 to 900 nm) with particularly large energy into electric energy efficiently and also convert long wavelength light into electric energy. is there.

  In Patent Documents 1 to 5, a wavelength conversion element (phosphor) that absorbs short-wavelength light with low photoelectric conversion efficiency and emits long-wavelength light with high photoelectric conversion efficiency is photoelectrically converted. The structure of the solar cell arrange | positioned at the incident side of an element is disclosed.

  Patent Document 6 discloses a solar cell that condenses light on a light condensing surface of a photoelectric conversion element using a Fresnel lens and converts light energy into electric energy. In the solar cell described in Patent Document 6, a prism sheet (deflecting plate) that deflects scattered light into vertical light is used to prevent the photoelectric conversion efficiency from being lowered due to the incident scattered light. A configuration arranged on the side is shown.

  Patent Document 7 discloses a configuration in which, in a solar cell including a plurality of current collecting grids on the light receiving surface side of a photoelectric conversion element, the shadow loss due to the current collecting grid is reduced and the photoelectric conversion efficiency is improved. . In the solar cell described in Patent Document 7, a diffraction member is arranged at a predetermined interval on the incident side of the current collecting grid so that light incident toward the current collecting grid is deflected by diffraction. The light is incident on the photoelectric conversion element.

JP 63-200576 A Japanese Patent Laid-Open No. 7-142752 Japanese Patent Laid-Open No. 10-261811 JP-A-11-220147 JP 11-345993 A JP 2007-73774 A JP 2011-165731 A

  However, in the solar cells described in Patent Documents 1 to 5, since the wavelength conversion element is disposed on the entire surface on the incident side of the photoelectric conversion element, light having a wavelength with high photoelectric conversion efficiency is also applied to this wavelength conversion element. Is absorbed and attenuated.

  Moreover, in the solar cell described in patent documents 6-7, the malfunction that the utilization efficiency of the light of a wavelength with bad photoelectric conversion efficiency was bad had arisen.

  In view of the above problems, an object of the present invention is to provide a solar cell with further improved photoelectric conversion efficiency.

  A solar cell according to the present invention includes a spectroscopic element that splits incident light into a first wavelength band and a second wavelength band, a wavelength conversion element that converts a second wavelength band split by the spectroscopic element into a first wavelength band, And a photoelectric conversion element that photoelectrically converts light in the first wavelength band.

  According to the present invention, the photoelectric conversion element can be converted into a wavelength band with good photoelectric conversion efficiency according to the spectral wavelength band. Therefore, it is possible to improve the photoelectric conversion efficiency by effectively using incident light having a wide wavelength band.

  In another aspect of the invention, the spectroscopic element is a diffraction grating, and the wavelength conversion element includes a plurality of types of wavelength conversion elements for a plurality of wavelength bands included in the second wavelength band. To do.

  According to the present invention, spectroscopy can be performed with a simple configuration.

  According to another invention, a mirror is disposed along an optical path between the spectroscopic element and the photoelectric conversion element, and the wavelength conversion element is formed on a surface of the mirror.

  According to the present invention, it is possible to perform wavelength conversion on the dispersed light with a simple configuration.

  According to another aspect of the invention, the spectroscopic element transmits the light in either the first wavelength band or the second wavelength band, and reflects the other light in a predetermined direction. The wavelength conversion element is arranged on the optical path of the light in the second wavelength band.

  The present invention divides incident light according to a wavelength band, converts a wavelength band having a low photoelectric conversion efficiency in a photoelectric conversion element into a wavelength band having a high photoelectric conversion efficiency, and converts the photoelectric conversion element to a photoelectric conversion element. The wavelength band with good photoelectric conversion efficiency is directly output to the photoelectric conversion element. Therefore, it is possible to improve the photoelectric conversion efficiency by effectively using incident light having a wide wavelength band.

  According to another aspect of the invention, there is provided a reflective film that reflects the other light reflected by the first wavelength selection filter toward the photoelectric conversion element.

  According to the present invention, the spectroscopic elements can be collected in a compact manner.

  According to another aspect of the invention, the first wavelength selection filter and the reflective film are arranged in parallel, the wavelength conversion element and the incident light incident surface are arranged in parallel, and the first wavelength selection filter The reflection film, the wavelength conversion element, and the incident surface form a parallelogram-shaped translucent block.

  According to the present invention, the spectroscopic element and the wavelength conversion element can be combined in a compact manner.

  According to another aspect of the invention, the second wavelength selection filter that reflects the light in the first wavelength band toward the wavelength conversion element is disposed on the light incident surface side of the wavelength conversion element.

  ADVANTAGE OF THE INVENTION According to this invention, photoelectric conversion efficiency can be improved by radiate | emitting the light reflected from the photoelectric conversion element toward a photoelectric conversion element again.

  According to another aspect of the invention, a plurality of the first wavelength selection filters are arranged in parallel, and a lens array for condensing incident light is arranged for each of the first wavelength selection filters. .

  ADVANTAGE OF THE INVENTION According to this invention, incident light can be radiate | emitted efficiently with respect to a photoelectric conversion element.

  The solar cell according to the present invention splits incident light according to a wavelength band, and converts the incident light into a wavelength band with good photoelectric conversion efficiency in the photoelectric conversion element according to the split wavelength band. Therefore, it is possible to improve the photoelectric conversion efficiency by effectively using incident light having a wide wavelength band.

It is a figure which shows an example of the wavelength dependence of the photoelectric conversion efficiency in an amorphous silicon type photoelectric conversion element. It is a figure which shows the structure of the solar cell with a wavelength conversion element using the diffraction grating as a spectroscopic element. It is a figure which shows the structure of the solar cell which used the diffraction grating as a spectroscopic element, and has arrange | positioned several wavelength conversion elements according to a wavelength range. It is a figure which shows the structure of the solar cell with a wavelength conversion element provided with the lens which uses a diffraction grating as a spectroscopic element, and parallelized the light of the spectral wavelength band. It is a figure which shows the structure of the solar cell which used the diffraction grating as a spectroscopic element, and formed the wavelength conversion element on the mirror arrange | positioned along the optical path between a spectroscopic element and a photoelectric conversion element. It is a figure which shows the structure of the solar cell using the wavelength spectral conversion module as a spectroscopic element. Configuration of solar cell using a diffraction grating as a spectroscopic element, arranging a plurality of wavelength conversion elements according to the wavelength band, and arranging a second wavelength selection filter for returning the wavelength band L1 reflected by the photoelectric conversion element back to the photoelectric conversion element FIG. It is a figure which shows the structure of the solar cell which has arrange | positioned the 2nd wavelength selection filter which returns the wavelength range | band L1 reflected in the photoelectric conversion element to a photoelectric conversion element again using a wavelength spectral conversion module as a spectral element. It is a figure which shows the structure of the solar cell which has arrange | positioned the deflection | deviation board in order to respond | correspond to diagonal incident light.

  First, FIG. 1 shows an example of wavelength dependency of photoelectric conversion efficiency in an amorphous silicon photoelectric conversion element.

  As shown in FIG. 1, the energy distribution of sunlight extends over a wide wavelength band. On the other hand, the wavelength band in which the amorphous silicon photoelectric conversion element performs photoelectric conversion is in a narrow range. Therefore, the photoelectric conversion element absorbs only a part of sunlight, and the photoelectric conversion efficiency is low.

  Therefore, in the present invention, in order to effectively use light in a wavelength band that is not absorbed by the photoelectric conversion element, first, sunlight is dispersed using a spectral element such as a diffraction grating. Then, light in a wavelength band having a low photoelectric conversion efficiency among the spectral wavelength bands is converted by the wavelength conversion element so as to be light in a wavelength band that can be absorbed by the photoelectric conversion element. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a diagram showing a configuration of a solar cell with a wavelength conversion element using a diffraction grating as a spectroscopic element. In the solar cell 10a shown in FIG. 2, sunlight LS (incident light) is spectrally separated for every predetermined diffraction angle using the spectroscopic element 12a using a diffraction grating. And in the photoelectric conversion element 20, the wavelength band L2 (2nd wavelength band) with low photoelectric conversion efficiency and the wavelength bands L3 and L4 (1st wavelength band) from which predetermined | prescribed photoelectric conversion efficiency are obtained are obtained. Of the spectral bands, the wavelength band L2 having a low photoelectric conversion efficiency in the photoelectric conversion element 20 is converted into light in the wavelength band L1 at which a predetermined photoelectric conversion efficiency is obtained using the wavelength conversion element 14a.

  As described above, the solar cell 10a is obtained by dispersing the sunlight LS with the spectroscopic element 12a using the diffraction grating, and converting the sunlight LS into the wavelength band L1 having better photoelectric conversion efficiency and then entering the photoelectric conversion element 20. The photoelectric conversion efficiency of can be improved.

  When the wavelength conversion element is arranged on the entire light incident surface of the photoelectric conversion element as in the past, light in a wavelength band that does not need to be converted also passes through the wavelength conversion element. Loss due to absorption or scattering occurred. In the present invention, the light is not incident on the wavelength conversion element 14a except for the specific wavelength band L2 having low photoelectric conversion efficiency. Therefore, loss due to absorption or scattering can be suppressed. Since the diffraction angle changes depending on the incident angle, the incident angle is preferably constant. Therefore, it is possible to provide a driving mechanism for tracking sunlight, in order to make the direction of the solar cell 10a follow the incident direction of sunlight.

As the photoelectric conversion element 20, an element such as a single crystal silicon type or an amorphous silicon type can be used. In addition to using a diffraction grating as the spectroscopic element 12a, an element such as a prism can be used. A phosphor or the like can be used as the wavelength conversion element 14a. For example, Y ₃ Al ₅ O ₁₂ : Ce (YAG: Ce-based phosphor) can be used as an element for converting the wavelength from blue to yellow. In addition, as a device for converting the wavelength from green to red, CaAlSiN ₃ : Eu (red cousin phosphor) can be used. In addition, ZnS or the like can be used as a Stokes type wavelength conversion element that absorbs light having a short wavelength and emits light having a long wavelength. Further, YbEr, YbTm, or the like can be used as an anti-Stokes type wavelength conversion element that absorbs light having a long wavelength and emits light having a short wavelength.

  FIG. 3 is a diagram showing a configuration of a solar cell in which a diffraction grating is used as a spectroscopic element and a plurality of wavelength conversion elements are arranged according to the wavelength band. In the solar cell 10b shown in FIG. 3, the sunlight LS is dispersed at every predetermined diffraction angle by using the spectroscopic element 12a using a diffraction grating. And in the photoelectric conversion element 20, the light of the wavelength band L2, L3, L4 (2nd wavelength band) with a low photoelectric conversion efficiency is obtained. Using the wavelength conversion elements 14a, 14b, and 14c suitable for each wavelength band, the wavelength band L1 (first wavelength band) in which higher photoelectric conversion efficiency is obtained with respect to the spectral wavelength bands L2, L3, and L4. Convert to light.

  In this way, the solar light LS is spectrally separated by the spectroscopic element 12a using a diffraction grating, and converted into the wavelength band L1 having excellent quantum efficiency of the photoelectric conversion element 20 and good photoelectric conversion efficiency. By making it enter, the photoelectric conversion efficiency of the solar cell 10b can be improved. By performing spectroscopy for each wavelength using the spectroscopic element 12a, it is possible to select and arrange the wavelength conversion elements 14a, 14b, and 14c suitable for the plurality of wavelength bands L2, L3, and L4.

  FIG. 4 is a diagram illustrating a configuration of a solar cell with a wavelength conversion element that includes a diffraction grating as a spectroscopic element and includes a lens that collimates light in a spectral wavelength band. In the solar cell 10c shown in FIG. 4, the sunlight LS is dispersed at every predetermined diffraction angle using the spectroscopic element 12a using a diffraction grating. And the light of the wavelength band L2 (2nd wavelength band) with a low photoelectric conversion efficiency in the photoelectric conversion element 20 and the wavelength bands L3 and L4 (1st wavelength band) from which predetermined photoelectric conversion efficiency is obtained is obtained. Thereafter, the light beams in the wavelength bands L2 and L4 and the wavelength band L3 that spread and travel using the lens 16 are collected into parallel light. Of the spectral bands, the wavelength band L2 having a low photoelectric conversion efficiency in the photoelectric conversion element 20 is converted into light in the wavelength band L1 at which a predetermined photoelectric conversion efficiency is obtained using the wavelength conversion element 14a.

  Thus, the photoelectric conversion element 20 can be reduced in size by dispersing the sunlight LS with the spectroscopic element 12a using a diffraction grating, concentrating the light into parallel light, and entering the photoelectric conversion element 20. Further, instead of using the lens 16 to convert the light in the wavelength band L2 and the wavelength band L4 into parallel light, the light can be condensed to a predetermined size. By condensing the light of the wavelength band L2 and the wavelength band L4 using the lens 16, the photoelectric conversion element 20 can be further reduced in size.

  FIG. 5 is a diagram showing a configuration of a solar cell in which a diffraction grating is used as a spectroscopic element, and a wavelength conversion element is formed on one of a pair of mirrors arranged to face each other along an optical path between the spectroscopic element and the photoelectric conversion element. It is. In the solar cell 10d shown in FIG. 5, the sunlight LS is dispersed at every predetermined diffraction angle using the spectroscopic element 12a using a diffraction grating. And the light of the wavelength band L2 (2nd wavelength band) with a low photoelectric conversion efficiency in the photoelectric conversion element 20 and the wavelength bands L3 and L4 (1st wavelength band) from which predetermined photoelectric conversion efficiency is obtained is obtained. Of the spectral wavelength band, light in the wavelength band diffracted at a predetermined angle is reflected by mirrors 22a and 22b arranged along the optical path. The wavelength band L2 having a low photoelectric conversion efficiency in the photoelectric conversion element 20 is converted into light in the wavelength band L1 at which a predetermined photoelectric conversion efficiency is obtained using the wavelength conversion element 14a formed on the mirror 22a.

  In this way, the solar light LS is spectrally separated by the spectroscopic element 12a using the diffraction grating, converted into the wavelength band L1 having better photoelectric conversion efficiency, and then incident on the photoelectric conversion element 20, thereby allowing the solar cell 10d to Photoelectric conversion efficiency can be improved. In addition, as shown in FIG. 4, when the condensing lens 16 is arranged, the solar cell 10 c becomes large in size, and the optical path between the diffraction grating and the photoelectric conversion element 20 arranged to face each other. The solar cells 10d can be reduced in size and weight by disposing the mirrors 22a and 22b and disposing the wavelength conversion element 14a on a part of the surface of the mirror 22a.

  In the embodiment shown in FIG. 5, an example is shown in which one type of wavelength conversion element 14a is arranged on the mirror 22a. However, a plurality of types of wavelength conversion elements are provided on the mirror 22a according to the diffraction angle of light. Can be arranged. In addition, other types of wavelength conversion elements can be arranged on the opposite mirror 22b.

  FIG. 6 is a diagram showing a configuration of a solar cell using a wavelength spectral conversion module as a spectroscopic element. In the solar cell 10e shown in FIG. 6, the sunlight LS is spectrally divided into the wavelength band L1 and the wavelength band L2 using the spectroscopic element 12b. The spectroscopic element 12b has a lens array 24 that condenses sunlight LS toward each first wavelength selection filter 28, and transmits the wavelength band L1 of the light collected by the lens array 24 and transmits the wavelength band L2. A first wavelength selection filter 28 that reflects and performs spectroscopy and a reflection film 30 that reflects the wavelength band L2 reflected by the first wavelength selection filter 28 toward the wavelength conversion element 14a are provided.

  The wavelength conversion element 14a converts light in the wavelength band L2 into light in the wavelength band L1. In this way, the sunlight LS is split into the wavelength band L1 and the wavelength band L2 by the spectroscopic element 12b using the first wavelength selection filter 28, and the light in the wavelength band L2 is converted into the wavelength band L1 with better photoelectric conversion efficiency. By converting the light into the photoelectric conversion element 20 after conversion, the photoelectric conversion efficiency of the solar cell 10e can be improved without using a diffraction grating.

  As the first wavelength selection filter 28, a dichroic filter composed of a dielectric multilayer film can be used. The first wavelength selection filter 28 is arranged to be inclined with respect to the optical axis of the sunlight LS (the normal direction of the photoelectric conversion element 20). For example, the short wavelength light (wavelength band L2) in which the quantum efficiency included in the sunlight LS is inferior. ) And the light of the long wavelength light (first wavelength band) excellent in quantum efficiency are transmitted.

  The reflective film 30 is disposed to face the first wavelength selection filter 28 and reflects the light of the short wavelength light (wavelength band L2) reflected by the first wavelength selection filter 28 toward the wavelength conversion element 14a. The wavelength conversion element 14 a enters the light in the wavelength band L <b> 2, converts the light into the light in the wavelength band L <b> 1, and causes the photoelectric conversion element 20 to enter the light. Further, the light in the wavelength band L1 that has passed through the first wavelength selection filter 28 is also incident on the photoelectric conversion element 20.

  Moreover, as shown in FIG. 6, the 1st wavelength selection filter 28 and the reflecting film 30 are arrange | positioned in parallel, and the wavelength conversion element 14a and the incident surface of sunlight LS (incident light) are arrange | positioned in parallel. The first wavelength selection filter 28, the reflective film 30, the wavelength conversion element 14a, and the incident surface are integrally formed so as to form a parallelogram-shaped translucent block. Furthermore, a plurality of parallelogram-shaped translucent blocks are integrated in an array.

  Note that a wavelength selection filter that transmits the wavelength band L2 and reflects the wavelength band L1 may be used instead of the first wavelength selection filter 28 that transmits the wavelength band L1 and reflects the wavelength band L2. In this case, the transmitted light in the wavelength band L2 passes through the wavelength conversion element 14a and is converted into light in the wavelength band L1, and then enters the photoelectric conversion element 20. The wavelength band L1 reflected by the wavelength selection filter is reflected by the reflective film 30 and directly enters the photoelectric conversion element 20. When parallel light such as sunlight is incident on the first wavelength selection filter 28, the lens array 24 composed of a plurality of linear lenses can be basically one.

  FIG. 7 shows a second wavelength selection filter that uses a diffraction grating as a spectroscopic element, arranges a plurality of wavelength conversion elements according to wavelength bands, and returns light reflected and returned from the photoelectric conversion element to the photoelectric conversion element again. It is a figure which shows the structure of the arrange | positioned solar cell. In the solar cell 10 f shown in FIG. 7, the sunlight LS is dispersed at every predetermined diffraction angle by the spectroscopic element 12 a using a diffraction grating. And the light of the wavelength band L2, L3, L4 (2nd wavelength band) with the low photoelectric conversion efficiency in the photoelectric conversion element 20 is obtained. Using the wavelength conversion elements 14a, 14b, and 14c suitable for each wavelength band, the wavelength band L1 (first wavelength band) in which higher photoelectric conversion efficiency is obtained with respect to the spectral wavelength bands L2, L3, and L4. Convert to light.

  Further, in the solar cell 10f, the second wavelength selection filters 32a, 32b, and 32c are disposed between the spectroscopic element 12a and the wavelength conversion elements 14a, 14b, and 14c, and the light that has once reached the photoelectric conversion element 20 is photoelectrically converted. When the light is reflected and returned by the conversion element 20, the light in the wavelength band L <b> 1 is reflected again toward the photoelectric conversion element 20. The second wavelength selection filters 32a, 32b, and 32c are elements that transmit the light dispersed by the spectroscopic element 12a and reflect the wavelength band L1 wavelength-converted by the wavelength conversion elements 14a, 14b, and 14c, and are dichroic filters. Etc. can be used.

  By using the configuration of the solar cell 10 f shown in FIG. 7, the light that is reflected and returned without being converted into electric power by the photoelectric conversion element 20 is incident again on the photoelectric conversion element 20 (the wavelength conversion element 14 a side). Thus, the photoelectric conversion efficiency can be improved.

  FIG. 8 is a diagram illustrating a configuration of a solar cell in which a wavelength spectral conversion module is used as a spectroscopic element, and a second wavelength selection filter that returns the wavelength band L1 reflected and returned from the photoelectric conversion element to the photoelectric conversion element is disposed. is there. In the solar cell 10g shown in FIG. 8, the sunlight LS is spectrally divided into the wavelength band L1 and the wavelength band L2 using the spectroscopic element 12b. The spectroscopic element 12b has a lens array 24 that condenses sunlight LS toward each first wavelength selection filter 28, and transmits the wavelength band L1 of the light collected by the lens array 24 and transmits the wavelength band L2. A first wavelength selection filter 28 that reflects and performs spectroscopy and a reflection film 30 that reflects the wavelength band L2 reflected by the first wavelength selection filter 28 toward the wavelength conversion element 14a are provided.

  The wavelength conversion element 14a converts light in the wavelength band L2 into light in the wavelength band L1. In this way, the sunlight LS is split into the wavelength band L1 and the wavelength band L2 by the spectroscopic element 12b using the first wavelength selection filter 28, and the light in the wavelength band L2 is converted into the wavelength band L1 with better photoelectric conversion efficiency. After conversion, light is incident on the photoelectric conversion element 20. As the first wavelength selection filter 28, a dichroic filter composed of a dielectric multilayer film can be used.

  The reflective film 30 is disposed to face the first wavelength selection filter 28 and reflects the light of the short wavelength light (wavelength band L2) reflected by the first wavelength selection filter 28 toward the wavelength conversion element 14a. . The wavelength conversion element 14 a enters the light in the wavelength band L <b> 2, converts the light into the light in the wavelength band L <b> 1, and causes the photoelectric conversion element 20 to enter the light. Further, the light in the wavelength band L1 that has passed through the first wavelength selection filter 28 is also incident on the photoelectric conversion element 20.

  Furthermore, in the solar cell 10g, the second wavelength selection filter 32 is disposed between the spectroscopic element 12b and the wavelength conversion element 14a, and the light that has once reached the photoelectric conversion element 20 is reflected by the photoelectric conversion element 20 and returned. In this case, the light in the wavelength band L1 is reflected again toward the photoelectric conversion element 20 (on the wavelength conversion element 14a side). The second wavelength selection filter 32 is an element that transmits the light dispersed by the spectroscopic element 12b and reflects the wavelength band L1 wavelength-converted by the wavelength conversion element 14a, and a dichroic filter can be used.

  By using the configuration of the solar cell 10 g shown in FIG. 8, the light that has been reflected without being converted into electric power by the photoelectric conversion element 20 is incident on the photoelectric conversion element 20 again to improve the photoelectric conversion efficiency. be able to. Similarly to the fifth embodiment, a wavelength selection filter that transmits the wavelength band L2 and reflects the wavelength band L1 is opposite to the first wavelength selection filter 28 that transmits the wavelength band L1 and reflects the wavelength band L2. It can also be used.

  FIG. 9 is a diagram showing a configuration of a solar cell in which a diffusion plate is arranged to cope with oblique incident light. In solar cell 10h shown in FIG. 9, slanting sunlight LS (incident light) is deflected so as to approach perpendicular to spectral element 12a (diffuse so as to produce a component that is perpendicularly incident on spectral element 12a). A diffusion plate 34 is disposed. And the sunlight LS is spectrally divided for every predetermined diffraction angle by the spectroscopic element 12a using a diffraction grating. And the light of the wavelength band L2 (2nd wavelength band) with a low photoelectric conversion efficiency in the photoelectric conversion element 20 and the wavelength bands L3 and L4 (1st wavelength band) from which predetermined photoelectric conversion efficiency is obtained is obtained. Among the spectral bands, the wavelength band L2 having a low photoelectric conversion efficiency in the photoelectric conversion element 20 is converted into light of the wavelength band L1 at which a predetermined photoelectric conversion efficiency is obtained using the wavelength conversion element 14a, and then photoelectric conversion is performed. The light enters the element 20. Since the diffuser plate 34 can diffuse the incident light substantially uniformly in all directions, the light incident on the diffraction grating (spectral element 12a) regardless of the position of the sun by arranging the diffuser plate 34. The state (distribution) of can be brought close to a constant. Thereby, stable diffraction (and eventually stable conversion efficiency or improvement of conversion efficiency) can be achieved without providing a drive mechanism for tracking sunlight. A lens for condensing the light diffused by the diffusion plate 34 so as to be close to, for example, parallel light may be disposed between the diffusion plate 34 and the diffraction grating (spectral element 12a).

10a, 10b, 10c, 10d, 10f, 10g, 10h ... solar cells 12a, 12b ... spectral elements 14a, 14b, 14c ... wavelength conversion elements 16 ... lenses 20 ... photoelectric conversion elements 22a, 22b ... mirrors 24 ... lens arrays 26 ... Wavelength spectral conversion module 28 ... first wavelength selection filter 30 ... reflection film 32, 32a, 32b, 32c ... second wavelength selection filter 34 ... diffusing plate

Claims (8)

A spectroscopic element that splits incident light into a first wavelength band and a second wavelength band;
A wavelength conversion element that converts a second wavelength band dispersed by the spectral element into a first wavelength band;
A solar cell comprising: a photoelectric conversion element that photoelectrically converts light in the first wavelength band. The spectroscopic element is a diffraction grating;
The solar cell according to claim 1, wherein the wavelength conversion element includes a plurality of types of wavelength conversion elements for a plurality of wavelength bands included in the second wavelength band. A mirror is disposed along an optical path between the spectroscopic element and the photoelectric conversion element,
The solar cell according to claim 1, wherein the wavelength conversion element is formed on a surface of the mirror. The spectroscopic element is a first wavelength selection filter that transmits light in either the first wavelength band or the second wavelength band and reflects the other light in a predetermined direction.
The solar cell according to claim 1, wherein the wavelength conversion element is disposed on an optical path of light in the second wavelength band.   The solar cell of Claim 4 which has arrange | positioned the reflecting film which reflects the said other light reflected by the said 1st wavelength selection filter toward the said photoelectric conversion element.   The first wavelength selection filter and the reflection film are arranged in parallel, the wavelength conversion element and the incident surface of the incident light are arranged in parallel, the first wavelength selection filter, the reflection film, and the wavelength conversion element. The solar cell according to claim 5, wherein the incident surface forms a parallelogram-shaped translucent block.   7. The first wavelength selection filter according to claim 1, further comprising a second wavelength selection filter configured to reflect the light in the first wavelength band toward the wavelength conversion element side on the light incident surface side of the wavelength conversion element. The solar cell according to item. A plurality of the first wavelength selection filters are arranged in parallel;
The solar cell of any one of Claims 4-7 which has arrange | positioned the lens array which condenses incident light with respect to each of said 1st wavelength selection filter.

Images