JP5548878B2 - Multi-junction optical element - Google Patents

Description

  The present invention relates to a multi-junction solar cell, a multi-junction light-receiving element, and a multi-junction light-emitting element having excellent photoelectric conversion efficiency.

  Conventionally, as a means for improving the conversion efficiency of a solar cell, a semiconductor layer having a different light absorption spectrum or band gap, for example, a tandem type in which an amorphous silicon semiconductor layer and a crystalline silicon semiconductor layer are laminated via a transparent conductive film or A solar cell called a multi-junction type is known (see Patent Documents 1 to 3). In such a multi-junction solar cell, when sunlight enters from a semiconductor layer whose upper light absorption spectrum is on the short wavelength side or a semiconductor layer with a wider forbidden band, the long wavelength transmitted through the semiconductor layer The sunlight with many components is absorbed in the semiconductor layer whose lower light absorption spectrum is on the long wavelength side or the semiconductor layer with the narrow forbidden band, and the solar spectrum is effectively absorbed as a whole. There is an effect of increasing the photoelectric conversion efficiency.

  Among such multi-junction solar cells, the technique disclosed in Patent Document 1 is shown in FIG. In Patent Document 1, in order to reduce the influence of defects at the stack interface between the first cell 51 and the second cell 54 of the solar battery, an insulating film 52 of nitride or oxide film is formed at the stack interface, and the insulating film An opening hole 53 is provided in the layer to realize electrical connection between the stacked layers.

  FIG. 7 is a diagram of a photovoltaic device having a tandem structure in which semiconductor layers having different forbidden bandwidths are stacked in Patent Document 2. As shown in FIG. 7, a single crystal silicon solar cell 65 formed on a single crystal silicon substrate 61 and provided with a metal electrode 63 having an opening on the surface, and a chalcopyrite formed on an insulating transparent substrate 66. Patent Document 2 discloses a tandem solar cell in which a compound thin film 67 and a solar battery cell 68 sandwiched between transparent electrode films 60 such as aluminum-doped zinc oxide are bonded and laminated with a transparent epoxy resin 62 or the like. . Also in this solar cell, the sun with many long-wavelength components transmitted through the chalcopyrite compound cell 67 by entering sunlight from the chalcopyrite compound cell 67 side having a wide forbidden band through the insulating transparent substrate 66. Light is absorbed by the single crystal silicon cell 65 having a narrow forbidden band below, and as a whole, the solar spectrum can be effectively absorbed to increase the photoelectric conversion efficiency of the solar cell.

  As an example of a multi-junction solar cell, a lower photoelectric conversion layer including a polycrystalline silicon substrate, an intermediate layer stacked on the lower photoelectric conversion layer, and an upper portion made of amorphous silicon stacked on the intermediate layer A structure including a photoelectric conversion layer is disclosed in Patent Document 3. The intermediate layer includes a transmissive conductive layer that selectively reflects and transmits light incident from the upper photoelectric conversion layer side according to a wavelength, and a silicon oxide film interspersed with a plurality of penetrating conductive portions. It is disclosed that the conductive portion is provided by applying and baking a conductive paste on a silicon oxide film.

JP 2003-124481 A JP-A-6-283737 JP-A-2003-142709

  When trying to stack a plurality of solar cells in order to increase the photoelectric conversion efficiency, various problems as described below arise when the stack is embodied. This is a problem common to multi-junction light-receiving elements and multi-junction light-emitting elements in which cells are stacked regardless of solar cells, and the present invention intends to solve these problems.

  In the technique disclosed in Patent Document 1, a semiconductor layer having a light absorption spectrum on the long wavelength side or a semiconductor layer having a narrow forbidden band and a light absorption spectrum on the same substrate (for example, a glass substrate). A semiconductor layer on the short wavelength side or a semiconductor layer with a wider forbidden band is sequentially deposited to form a tandem solar cell. The semiconductor layer deposited later as a procedure has a problem that the deposition conditions are limited by the properties of the substrate or the previously deposited semiconductor layer, and the optimum deposition conditions cannot always be selected. For example, if the upper limit of the stable temperature of the semiconductor layer deposited earlier is lower than the optimum temperature of the semiconductor layer deposited later, the semiconductor layer deposited earlier deteriorates when the deposition temperature is high, and conversely the deposition temperature If it is low, there is a problem that the characteristics of a semiconductor layer deposited later are not sufficient. Further, although the properties of the semiconductor layer deposited later are affected by the underlying layer, there is a problem that when a plurality of layers are deposited on the same substrate, it is not always possible to select an optimal underlying substrate for deposition. For example, a single crystal that is lattice-matched with the single crystal semiconductor layer is optimal as the base for depositing the single crystal semiconductor layer. However, when the base is a polycrystalline layer, the single crystal layer cannot be deposited. Furthermore, the direction in which sunlight is incident is limited to one direction from the transparent substrate side, and there is a problem that the degree of freedom in structure is small. Also in Patent Document 3, since the upper photoelectric conversion layer is laminated on the lower photoelectric conversion layer including the polycrystalline silicon substrate, there is a problem similar to that of Patent Document 1.

  In the technique disclosed in Patent Document 2, a plurality of solar cells are formed on a plurality of different substrates, and an optimum deposition condition can be selected for each cell. Since it is merely mechanically bonded with resin, there is no electrical connection between the cells, and there is a problem that the electrode of each cell must be taken out from the bonded portion. For this reason, when the cell area is large, there is a problem that the distance from the center of the cell to taking out the electrode to the outside becomes long, the electrical resistance increases and the power loss increases. In addition, since an extra space for taking out and connecting the electrodes to the outside is required, there is a problem that the size of the element increases. Furthermore, the direction in which sunlight is incident is limited to one direction from the transparent substrate side, and there is a problem that the degree of freedom in structure is small.

  The present invention is intended to solve these problems. In a multi-junction solar cell, a multi-junction light-receiving element, and a multi-junction light-emitting element, the performance of the solar cell and each element is improved by an improved laminated structure. The purpose is to let you. Furthermore, in multi-junction solar cells, multi-junction light-receiving elements, and multi-junction light-emitting elements, when laminating solar battery cells, light-receiving element cells, and light-emitting element cells, it is possible to select optimum lamination conditions, An object is to increase the degree of freedom of the layer structure such as a crystal layer, a single crystal layer, and an amorphous layer.

  In order to achieve the above object, the present invention has the following characteristics.

  The multi-junction solar cell of the present invention is a multi-junction solar cell in which a plurality of solar cells having different light absorption spectra are stacked and electrically connected, and at least one of the solar cells. Is formed on a transparent substrate having through-holes opened on both sides, and the inside of the through-hole of the transparent substrate and the surface of the transparent substrate on which no solar cells are formed are covered with a transparent conductive film, The battery cell is characterized in that the cells are laminated and joined in the order of the absorption wavelength so that light enters from the cell having the shortest light absorption wavelength.

  At least one of the solar battery cells is a solar battery cell excluding an end solar battery cell on the opposite side to which light is incident.

  The transparent substrate used in the present invention is selected from any one or more of a glass substrate, a resin substrate, a polycrystalline substrate, and a single crystal substrate.

At least one of the solar cells according to the present invention is formed of a single crystal thin film of silicon, germanium, silicon germanium, silicon tin, or silicon germanium tin formed on a glass substrate.
Further, at least one of the solar cells is made of a microcrystalline thin film of silicon or silicon germanium formed on a glass substrate.
Further, at least one of the solar cells is made of an amorphous thin film of silicon or silicon carbide formed on a glass substrate.

In addition, at least one of the solar cells is formed of a single crystal thin film of gallium arsenide, gallium arsenide, or indium gallium phosphide formed on a gallium arsenide single crystal substrate.
In addition, at least one of the solar cells is made of a single crystal thin film of indium gallium nitride formed on a sapphire or gallium nitride substrate.
Further, at least one of the solar cells is made of a chalcopyrite thin film formed on a soda lime glass substrate. In addition, at least one of the solar cells is composed of an organic thin film formed on a transparent plastic substrate.

In the present invention, at least one of the solar cells is laminated by adjoining the adjacent solar cells and a transparent conductive film.
In addition, at least one of the solar cells is a solar cell excluding an end solar cell on the side opposite to the side on which light is incident. The end solar cell on the side opposite to the light incident side does not need to be provided on the transparent substrate. Further, it is preferable to provide all of the solar cells except for the end solar cells on the side opposite to the light incident side on the transparent substrate having through holes as in the present invention, but not all, but at least one A solar battery cell may be provided on a transparent substrate having a through hole, and a conventional structure may be used for the stacked structure of other solar battery cells.

  The multi-junction light-receiving element of the present invention is a multi-junction light-receiving element in which a plurality of light-receiving elements having different light absorption spectra are stacked and electrically connected, and at least one of the light-receiving elements has a through hole. The transparent substrate has a through-hole in the transparent substrate and the surface of the transparent substrate on the side where the light receiving element is not formed is covered with a transparent conductive film, and the light receiving element has a shortest light absorption wavelength. Each light receiving element is laminated and joined in order of absorption wavelength so that light is incident.

  The multi-junction light-emitting element of the present invention is a multi-junction light-emitting element in which a plurality of light-emitting elements having different emission spectra are stacked and electrically connected. At least one of the light-emitting elements is transparent with a through hole. Formed on the substrate, the inside of the through hole of the transparent substrate and the surface of the transparent substrate where the light emitting element is not formed are covered with a transparent conductive film, and the light emitting element emits light from the light emitting element with the shortest emission wavelength. Each light emitting element is laminated and joined in the order of the emission wavelength.

In the multijunction solar cell according to the present invention, a plurality of solar cells having different light absorption spectra are laminated and joined in the order of absorption wavelengths so that light enters from the cell having the shortest light absorption wavelength. It is possible to effectively absorb a wide sunlight spectrum and increase the photoelectric conversion efficiency of the solar cell.
In the multi-junction solar cell according to the present invention, since a plurality of different solar cells are formed on a plurality of different substrates, the optimum substrate and formation conditions can be selected for each solar cell. .

Further, in the multi-junction solar cell according to the present invention, at least the solar cell substrate except the end solar cell on the side opposite to where light is incident has through-holes opened on both sides thereof, and The inside of the through hole and at least the surface of the substrate on which the solar cells are not formed are covered with a transparent conductive film, and each is electrically connected by bonding. There is no need to take out the electrode of the cell to the outside, the electric resistance can be reduced, the power loss can be reduced, and the area of the element can be reduced.
In the multi-junction solar cell according to the present invention, since the solar cells are formed on a glass substrate, a transparent resin substrate, or a transparent crystal substrate, sunlight is transmitted to the transparent substrate side according to the order of their lamination. Even if it is incident from the opposite side, it has the structural freedom to operate almost the same even if it is incident from the opposite side, so the optimal light reflecting structure should be provided on the opposite side of the incident surface as appropriate Can do.

In the multi-junction type light receiving element according to the present invention, a plurality of light receiving elements having different light absorption spectra are joined by stacking the elements in the order of the absorption wavelengths so that light enters from the light receiving element having the shortest light absorption wavelength. Thus, incident light having a wide spectrum can be efficiently distributed to the light receiving elements having the same light absorption spectrum.
In the multi-junction type light receiving element according to the present invention, since a plurality of different light receiving elements are formed on a plurality of different substrates, respectively, an optimum substrate and formation conditions can be selected for each light receiving element.

In the multi-junction light receiving element according to the present invention, the substrate of each light receiving element excluding at least the end light receiving element on the side opposite to where light is incident has through holes opened on both sides thereof, Since at least the surface of the substrate where the light receiving element is not formed is covered with a transparent conductive film and each is electrically connected by bonding, the electrodes of each light receiving element except for the cells at both ends are exposed to the outside. There is no need to take out, and the area of the element can be reduced.
Further, in the multi-junction type light receiving element according to the present invention, each light receiving element except at least the end light receiving element on the side opposite to where light is incident is formed on a glass substrate, a transparent resin substrate, or a transparent crystal substrate. Therefore, depending on the order of the stacking, it is possible to have a structural degree of freedom in which the operation is almost the same regardless of whether the light is incident from the substrate side or the opposite side.

In the multi-junction light-emitting device according to the present invention, the light-emitting elements having different emission spectra are laminated and joined in the order of the emission wavelength so that the light-emitting elements having different emission spectra are emitted from the element having the shortest emission wavelength. Thus, it is possible to efficiently emit a broad spectrum light.
In the multi-junction light-emitting element according to the present invention, since a plurality of different light-emitting elements are formed on a plurality of different substrates, the optimum substrate and formation conditions can be selected for each light-emitting element.

Further, in the multi-junction light emitting device according to the present invention, the substrate of each light emitting device excluding at least the end light emitting device on the side opposite to where light is emitted has through holes opened on both sides thereof, At least the surface of the substrate on which the light emitting element is not formed is covered with a transparent conductive film, and each is electrically connected by bonding. Therefore, the electrodes of each light emitting element excluding the light emitting elements at both ends are exposed to the outside. There is no need to take out, and the area of the element can be reduced.
Further, in the multi-junction light emitting device according to the present invention, at least each light receiving device except the end light emitting device on the opposite side from which light is emitted is formed on a glass substrate, a transparent resin substrate, or a transparent crystal substrate. Therefore, depending on the order of the stacking, it is possible to have a structural degree of freedom in which the operation is almost the same whether the light is emitted from the substrate side or the opposite side.

The figure which shows the structure of the multijunction solar cell which concerns on 1st Example of this invention. The figure which shows the structure of the multijunction solar cell which concerns on 2nd Example of this invention. The figure which shows the cross-section of the middle (the glass substrate which deposited the transparent conductive film) which produces a microcrystal silicon germanium photovoltaic cell in 1st Example of the multijunction type solar cell by this invention The figure which shows the structure of the multijunction solar cell which concerns on 3rd Example of this invention. The figure which shows the structure of the multijunction solar cell which concerns on 4th Example of this invention. The figure which shows the structure of the multijunction type solar cell of a prior art. The figure which shows the structure of the multijunction type solar cell of another prior art.

A first embodiment of the multijunction solar cell of the present invention will be described with reference to FIG. As shown in FIG. 1, three layers are laminated in the order of a p-type single crystal silicon film 3 / i-type single crystal silicon germanium film 4 / n-type single crystal silicon germanium film 5 on a glass substrate 2 having a through hole. The first solar cell 17 made of the p-type i-type n-type single crystal film is formed. The glass substrate 2 has through-holes 20, and the inside of the through-holes and at least the surface of the substrate on which the solar cells are not formed are covered with the metal thin film 1.
Further, on the first solar cell 17, a glass substrate 2 having a through hole having openings on both surfaces and having the inside of the through hole and the substrate surface covered with the transparent conductive film 6 is disposed. Yes. Three layers of p-type i-type n-type microcrystalline films are laminated on a glass substrate 2 in this order: p-type microcrystalline silicon film 8 / i-type microcrystalline silicon germanium film 9 / n-type microcrystalline silicon film 10. A second solar battery cell 18 is formed.
Further, on the second solar battery cell 18, a glass substrate 2 having a through hole 20 having openings on both sides and having the inside of the through hole and the substrate surface covered with the transparent conductive film 6 is disposed. ing. A third layer composed of three layers of p-type i-type n-type amorphous silicon films laminated in the order of p-type amorphous silicon film 13 / i-type amorphous silicon film 14 / n-type amorphous silicon film 15 on glass substrate 2. The solar battery cell 19 is formed. A transparent conductive film 6 is formed on the third solar battery cell 19.

(Function)
In the multi-junction solar cell of FIG. 1, when sunlight enters from the upper side of the figure, the semiconductor layer located on the upper side and having a light absorption spectrum on the short wavelength side or the semiconductor layer with the wider forbidden band (third The short wavelength component of sunlight is absorbed by the solar cell 19). The sunlight having a lot of long wavelength components transmitted through the semiconductor layer is a semiconductor layer having a light absorption spectrum located on the lower wavelength side or a semiconductor layer having a narrow forbidden band (second solar cell 18). To be absorbed. Further, sunlight having a longer wavelength component transmitted through the semiconductor layer is located below, the semiconductor layer having a light absorption spectrum on the longer wavelength side, or a semiconductor layer with a narrower forbidden band (first semiconductor layer) Absorbed by the solar cell 17). Thus, the solar spectrum is effectively absorbed as a whole, and the photoelectric conversion efficiency of the solar cell is increased. Further, the solar cells are electrically connected to each other by bonding through the through-hole interior 20 and the transparent conductive film 6 covered with the transparent substrate.

  The example of a three-stage solar cell composed of first to third solar cells has been illustrated and described as a multi-junction solar cell. However, the same structure applies when two or more cells are joined. Form with. Although an example of a glass substrate has been shown as the transparent substrate, it may be laminated using any one or more of a transparent resin substrate, a transparent polycrystalline substrate, and a transparent single crystal substrate. By using the laminated structure of the present invention, an optimum semiconductor layer can be formed using different substrates, and the performance can be further improved. Since the through holes are finely processed, it is preferable to form the first half by laser light irradiation and the second half by etching. As other methods, it can also be formed by laser irradiation, etching or the like. The transparent conductive film is preferably made of zinc oxide doped with gallium or indium oxide doped with hydrogen. The transparent substrate is an example of a glass substrate, but a resin substrate, a polycrystalline substrate, or a single crystal substrate can be used.

  As a semiconductor layer of a photovoltaic cell, not only the illustrated layer but also a conventionally used photovoltaic cell can be used. At least one of the solar cells to be stacked is preferably made of a single crystal thin film of silicon, germanium, silicon germanium, silicon tin or silicon germanium tin formed on a glass substrate. In addition, at least one of the solar cells to be stacked is preferably made of a microcrystalline thin film of silicon or silicon germanium formed on a glass substrate. Moreover, it is preferable that at least one of the stacked photovoltaic cells is made of an amorphous thin film of silicon or silicon carbide formed on a glass substrate. In addition, at least one of the stacked solar battery cells is preferably made of a single crystal thin film of indium gallium nitride formed on a sapphire or gallium nitride substrate. Moreover, it is preferable that at least one of the stacked photovoltaic cells is made of a chalcopyrite thin film formed on a soda lime glass substrate. Moreover, it is preferable that at least one of the stacked solar battery cells is made of an organic thin film formed on a transparent plastic substrate.

  At least one of the multi-stage solar cells to be joined of the present invention is formed on a transparent substrate having through holes that are open on both sides, and the inside of the through holes of the transparent substrate and the transparent substrate The surface on which the solar cells are not formed is formed so as to be covered with a transparent conductive film. Thus, since each cell is electrically connected by bonding with the transparent conductive film inside the through hole, the electrical resistance can be reduced and the power loss can be reduced without taking out the cell electrode to the outside. Can be reduced.

<Manufacturing method>
The solar cell according to the first embodiment is formed by stacking a single crystal silicon germanium solar cell, a microcrystalline silicon germanium solar cell, and an amorphous silicon solar cell.

(Manufacturing method of the first cell)
First, a single crystal silicon germanium solar battery cell on a glass substrate is manufactured by the following procedure.
SiOG (single crystal silicon thin film on glass) or GeOG (single crystal germanium thin film on glass) developed by Corning, USA is used as the substrate. Glass is alkali-free with a thickness of 0.7 mm, a depth of 0.65 mm, a diameter of 0.1 mm to 0.5 mm, and a tapered hole that narrows toward the single crystal film, with a wavelength of 800 nm and a power of 260 mJ. A laser beam is irradiated 70,000 times per laser beam, and two-dimensionally arranged at intervals of 2 to 5 mm. Here, the method for forming the hole is not limited to laser light, and etching, sandblasting, and a mechanical drill may be used. The single crystal silicon or germanium thin film is p + type, has a thickness of 200 nm and a plane orientation (100).

On this substrate, silane (SiH ₄ ) and germanium tetrafluoride (GeF ₄ ) are used as raw gases, and an undoped composition having a forbidden band width of 0.9 eV by thermochemical vapor deposition (CVD) at a substrate temperature of 400 ° C. Single crystal silicon germanium (SiGe) is epitaxially grown to a thickness of 5 μm. Further, phosphine (PH ₃ ) is added to the source gas, and an n + -type SiGe is grown thereon to a thickness of 200 nm.
Next, after masking portions other than the openings on the back surface (surface with holes) of the glass substrate with a resist or the like, the glass is etched with diluted hydrofluoric acid (HF) to penetrate the holes.

Next, a 100 nm thick amorphous amorphous hydrogen-doped indium oxide (In ₂ O ₃ ) transparent conductive film is deposited on the single crystal SiGe layer by magnetron sputtering. Sputtering uses an indium oxide sintered body as a raw material target, the substrate temperature is room temperature, and a mixed atmosphere of argon (Ar), oxygen (O ₂ ), and water vapor (H ₂ O) (total pressure about 0.5 Pa, Ar partial pressure) 4.98 × 10 ⁻¹ Pa, O ₂ partial pressure 2 × 10 ⁻³ Pa, H ₂ O partial pressure 1 × 10 ⁻⁴ Pa). Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film.
This single crystal silicon germanium solar battery cell has the maximum photoelectric conversion efficiency at a wavelength of about 1 μm. Note that the growth method of single crystal silicon germanium is not limited to the thermal CVD method, and a molecular beam epitaxy (MBE) method or a plasma enhanced chemical vapor deposition (PECVD) method may be used.

(Manufacturing method of the second cell)
Next, a microcrystalline silicon germanium solar battery cell on a glass substrate is manufactured by the following procedure.
A tapered hole with a depth of 0.25 mm and a diameter of 0.02 mm to 0.1 mm becomes narrow on a Pyrex (registered trademark) glass substrate with a thickness of 0.3 mm, and a femtosecond with a wavelength of 800 nm and a power of 260 mJ. A laser beam is irradiated 25,000 times per laser beam, and two-dimensionally opened at intervals of 1 to 2 mm. A transparent conductive film of zinc oxide (ZnO) doped with gallium oxide and 5.7 weight of digallium trioxide (Ga ₂ O ₃ ) on the non-perforated surface of the Pyrex (registered trademark) glass substrate. Using ZnO containing 2% as a target, a thickness of 300 nm is deposited by high-frequency sputtering in an argon atmosphere.

  FIG. 3 shows a cross-sectional structure of a glass substrate on which a transparent conductive film is deposited according to the procedure so far.

Next, a p-type microcrystal having a thickness of 30 nm is formed on the transparent conductive film by plasma enhanced chemical vapor deposition under the conditions of a temperature of 250 ° C., a pressure of 1 Torr, an electrode interval of 8 mm, and a high frequency power density of 0.3 W / cm ^2. Silicon, i-undoped microcrystalline silicon germanium with a thickness of 1 μm, and n-type microcrystalline silicon with a thickness of 30 nm are sequentially deposited. Here, silane (SiH ₄ ) having a flow rate of 5 sccm and germane (GeH ₄ ) having a flow rate of 0.3 sccm are diluted with hydrogen (H ₂ ) having a flow rate of 300 sccm.

At this time, the germanium composition in the microcrystalline silicon germanium is approximately 0.2, and the photoelectric conversion efficiency of the solar battery cell is maximized around the wavelength of 650 nm.
Phosphine (PH ₃ ) is used for p-type impurity doping, and diborane (B ₂ H ₆ ) is used for n-type diluted with hydrogen.

On these microcrystalline layers, a 100 nm thick amorphous hydrogen-dominated indium oxide (In ₂ O ₃ ) transparent conductive film is deposited by magnetron sputtering. Sputtering uses an indium oxide sintered body as a raw material target, the substrate temperature is room temperature, and a mixed atmosphere of argon, oxygen and water vapor (total pressure: about 0.5 Pa, Ar partial pressure: 4.98 × 10 ⁻¹ Pa, O ₂ min. Pressure 2 × 10 ⁻³ Pa, H ₂ O partial pressure 1 × 10 ⁻⁴ Pa). Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film.
Next, after masking the glass substrate other than the opening on the back (surface with holes) with a resist, etc., the glass is etched with diluted hydrofluoric acid (HF), and the holes are penetrated until the transparent conductive film is exposed. . Further, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide (In ₂ O ₃ ) transparent conductive film is similarly deposited on the back surface of the glass by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the transparent conductive film on the glass surface. To improve the flatness of the back side. Further, a polishing process may be performed.

Here, the transparent conductive film is not limited to zinc oxide (ZnO) or indium oxide (In ₂ O ₃ ), but includes tin (Sn), titanium (Ti), zirconium (Zr), hafnium (Hf), and molybdenum. Indium oxide metal oxides, zinc oxide metal oxides, gallium oxide metal oxides, tin oxide metal oxides, magnesium oxide containing elements having a valence of 4 or more, such as (Mo) and tungsten (W) It may be a metal oxide, a cadmium oxide metal oxide, or two or more metal oxides selected from the metal oxides. Further, the method of depositing the transparent conductive film is not limited to the sputtering method, but may be a chemical vapor reaction (CVD) method that is more suitable for embedding in the through hole. Further, the method for drilling the glass substrate is not limited to the femtosecond laser, and sandblasting, etching, or a mechanical drill may be used.

(Manufacturing method of the third cell)
Next, an amorphous silicon cell on a glass substrate is produced by the following procedure.
Taper holes that become narrower as the depth increases from 0.02 mm to 0.1 mm at a depth of 0.25 mm on a Pyrex (registered trademark) glass substrate with a thickness of 0.3 mm. Open dimensionally. A transparent conductive film of zinc oxide doped with gallium oxide is deposited on the surface of the Pyrex (registered trademark) glass substrate, which has no holes, in the same manner as described above to a thickness of 300 nm.

Next, p-type amorphous silicon with a thickness of 30 nm is formed on the transparent conductive film under the conditions of a plasma-excited chemical vapor deposition method at a temperature of 200 ° C., a pressure of 0.05 Torr, an electrode interval of 8 mm, and a high-frequency power density of 0.02 W / cm ^2. Then, an i (undoped) type amorphous silicon having a thickness of 300 nm and an n type amorphous silicon having a thickness of 30 nm are sequentially deposited. Here, the source gas is used by diluting silane having a flow rate of 20 sccm with hydrogen having a flow rate of 300 sccm. Phosphine is used for p-type impurity doping, and diborane is diluted with hydrogen for n-type.

On these amorphous layers, a 100 nm-thick amorphous hydrogen-dominated indium oxide transparent conductive film is deposited by magnetron sputtering. Sputtering uses an indium oxide sintered body as a raw material target, the substrate temperature is room temperature, and a mixed atmosphere of argon, oxygen and water vapor (total pressure: about 0.5 Pa, Ar partial pressure: 4.98 × 10 ⁻¹ Pa, O ₂ min. Pressure 2 × 10 ⁻³ Pa, H ₂ O partial pressure 1 × 10 ⁻⁴ Pa). Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film.

  Next, after masking portions other than the opening on the back surface (surface with holes) of the glass substrate with a resist or the like, the glass is etched with diluted hydrofluoric acid, and the holes are penetrated until the transparent conductive film is exposed. Further, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is similarly deposited on the rear surface of the glass by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the transparent conductive film on the glass surface. To improve the flatness of the back side. Further, a polishing process may be performed. This amorphous silicon cell has the maximum photoelectric conversion efficiency of the solar battery cell in the vicinity of a wavelength of 500 nm.

(Join 3 cells)
The single crystal silicon germanium solar battery cell, the microcrystalline silicon germanium solar battery cell and the amorphous silicon solar battery thus manufactured are joined by the following procedure.
Plasma treatment is performed on each transparent conductive film formed on the surface of the single crystal silicon germanium solar cell, the front and back surfaces of the microcrystalline silicon germanium solar cell, and the back surface of the amorphous silicon solar cell. The plasma treatment is performed by ion irradiation for 120 seconds in an argon or oxygen atmosphere (total pressure: about 10 Pa).

Next, in order for the plasma-treated amorphous and polycrystalline transparent conductive films to be combined, the three cells in the order of single crystal silicon germanium solar cell, microcrystalline silicon germanium solar cell, and amorphous silicon solar cell are connected. Stack in the atmosphere. Place the superposed sample on a hot press machine heated to 160 ° C, apply a load of 1 to 6 MPa and hold it for 10 minutes, raise the temperature of the press machine to 180 ° C over about 5 minutes and hold for 10 minutes . Thereafter, the temperature of the press is raised to 200 ° C. over about 5 minutes and held for 10 minutes. Then, it is naturally air-cooled with a load applied, and the sample is taken out from the press. It should be noted that the arrangement of the amorphous and polycrystalline transparent conductive films may be reversed from that in the above embodiment, and both of them may be amorphous without being annealed before bonding.
A comb-like or grid-like electrode is formed on the transparent conductive film on the upper surface of the laminated three-junction cell, and an electrode reaching the back of the through hole is formed on the entire glass substrate on the lower surface by vacuum deposition of silver or aluminum, respectively.

  A second embodiment of the multijunction solar cell of the present invention will be described with reference to FIG. As shown in FIG. 2, the p-type amorphous silicon film 13 / i-type amorphous silicon film 14 / n-type amorphous silicon film 15 are laminated in this order on the glass substrate 2 covered with the transparent conductive film 6. A first solar cell 17 made of a type i type n type amorphous silicon film is formed. The glass substrate 2 has a through hole 20, and the inside of the through hole and the surface of the substrate on which the solar cells 17 are not formed are covered with the transparent conductive film 6. Further, on the first solar cell 17, there is disposed a glass substrate 2 that has through holes 20 having openings on both surfaces and the inside of the through holes and both surfaces of the substrate are covered with the transparent conductive film 6. Has been. Three layers of p-type i are laminated in the order of p-type microcrystalline silicon film 8 / i-type microcrystalline silicon germanium film 9 / n-type microcrystalline silicon film 10 on glass substrate 2 covered with transparent conductive film 6. A second solar cell 18 made of a type n type microcrystalline film is formed. Further, on the second solar battery cell 18, a glass substrate 2 having a through hole 20 having openings on both sides and having the inside of the through hole and the substrate surface covered with the transparent conductive film 6 is disposed. ing. Three layers of p-type i-type n-type single crystal laminated in order of p-type single-crystal silicon film 3 / i-type single-crystal silicon germanium film 4 / n-type single-crystal silicon germanium film 5 on glass substrate 2 A third solar battery cell 19 made of a film is formed. Further, the metal thin film 1 is formed on the third solar battery cell 19. Further, a comb-like or lattice-like metal thin film 1 is formed on the transparent conductive film 6 on the lower surface of the first solar battery cell 17.

(Function)
In the multi-junction solar cell of FIG. 2, when sunlight enters from the lower side of the figure, spectral components near and shorter than the wavelength of 500 nm are mainly absorbed by the amorphous silicon solar cell and out of the spectral components transmitted therethrough Spectral components around 650 nm and shorter wavelengths are mainly absorbed by microcrystalline silicon germanium solar cells, and the spectral components on the long wavelength side that have passed through them are absorbed into single-crystal silicon germanium solar cells centered around 1 μm wavelength. Absorbed. Here, the glass substrate and the transparent conductive film are transparent in the light wavelength region of interest, and almost no loss occurs due to absorption. The sunlight components absorbed in each cell are converted into currents and connected in series with a transparent conductive film, so that the combined power can be efficiently extracted from the upper and lower electrodes.

  The example of a three-stage solar cell composed of first to third solar cells has been illustrated and described as a multi-junction type solar cell, but the same applies when two or more cells are joined. Form with structure. Further, the second embodiment has the same configuration as that described in the first embodiment except that the incident direction of sunlight is different.

<Manufacturing method>
This example also consists of a stack of amorphous silicon solar cells, microcrystalline silicon germanium solar cells and single crystal silicon germanium solar cells.

(Manufacturing method of the first cell)
The method of forming the amorphous silicon solar cell is the same as that of the first embodiment until the formation of the amorphous silicon layer. Next, after masking the glass substrate other than the opening on the back (surface with holes) with a resist, etc., the glass is etched with diluted hydrofluoric acid (HF), and the holes are penetrated until the transparent conductive film is exposed. . Further, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is similarly deposited on the rear surface of the glass by magnetron sputtering. The transparent conductive film on the back surface is also embedded inside the through hole and is in electrical contact with the transparent conductive film on the glass surface. Then, a 100 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is deposited on the amorphous silicon layer by magnetron sputtering. After that, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive films on both sides.

(Manufacturing method of the second cell)
The method of forming the microcrystalline silicon germanium solar cell is the same as that of the first embodiment until the microcrystalline silicon germanium layer is formed. Next, after masking portions other than the opening on the back surface (surface with holes) of the glass substrate with a resist or the like, the glass is etched with diluted hydrofluoric acid, and the holes are penetrated until the transparent conductive film is exposed. Further, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is similarly deposited on the rear surface of the glass by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the transparent conductive film on the glass surface. Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film. Then, on the microcrystalline silicon germanium layer, a 100 nm thick amorphous dominant hydrogen-doped indium oxide transparent conductive film is deposited by magnetron sputtering.

(Manufacturing method of the third cell)
The single crystal silicon germanium solar battery cell is the same as that of the first embodiment until the formation of the single crystal silicon germanium thin film. Next, after masking portions other than the openings on the back surface (surface with holes) of the glass substrate with a resist or the like, the glass is etched with diluted hydrofluoric acid (HF) to penetrate the holes. Then, a 300 nm thick amorphous hydrogen-doped indium oxide transparent conductive film having a dominant thickness of 300 nm is similarly deposited on the back surface of the glass by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the p + type single crystal silicon or germanium film. Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film.

(Join 3 cells)
The amorphous silicon solar cell, the microcrystalline silicon germanium solar cell, and the single crystal silicon germanium solar cell thus manufactured are joined by the following procedure.
Plasma treatment is performed on each of the transparent conductive films formed on the amorphous silicon solar cell surface, the front and back surfaces of the microcrystalline silicon germanium solar cell, and the single crystal silicon germanium solar cell back surface.
Next, in order for the plasma-treated amorphous and polycrystalline transparent conductive films to come together, the amorphous silicon solar cell, the microcrystalline silicon germanium solar cell, and the single crystal silicon germanium solar cell are connected in this order. Stack in the atmosphere. The subsequent joining procedure is the same as in the first embodiment.
Electrodes are formed on the entire surface of the single-crystal silicon germanium on the top surface of the stacked three-junction cell, and comb-shaped or lattice-shaped electrodes that do not overlap with the through-holes are formed on the transparent conductive film on the bottom glass substrate by vacuum deposition of silver or aluminum, respectively. To do.

In this embodiment, as shown in FIG. 5, a single crystal silicon solar battery cell 17 and a single crystal gallium arsenide solar battery cell 18 are stacked.

<Manufacturing method>
The single crystal silicon solar battery cell 17 forms a pn junction by diffusing phosphorus (P) into a p-type silicon wafer having a resistivity of 1 μcm and a thickness of 0.2 mm manufactured by the CZ method. Diffusion is carried out by bubbling POCl ₃ with nitrogen and at a temperature of 900 ° C. for 10 minutes. Thereafter, the n-type layers on the end face and the back face are mechanically removed. In order to improve the absorption efficiency by scattering sunlight, the back surface may be further treated in a 5% solution of sodium hydroxide at a temperature of 80 ° C. for 10 minutes to form a texture structure.
Thereafter, a transparent conductive film of zinc oxide doped with gallium oxide is deposited on the surface of the n-type silicon layer with a thickness of 300 nm by RF sputtering in an argon atmosphere using ZnO containing 5.7% by weight of digallium trioxide as a target. To do. Here, the transparent conductive film is not limited to zinc oxide, but an indium oxide-based metal oxide or zinc oxide-based metal containing an element having a positive valence of four or more, such as tin, titanium, zirconium, hafnium, molybdenum, and tungsten. Oxide, gallium oxide metal oxide, tin oxide metal oxide, magnesium oxide metal oxide, cadmium oxide metal oxide, or two or more metal oxides selected from the metal oxides. May be. Further, the method for depositing the transparent conductive film is not limited to the sputtering method, but may be a chemical vapor reaction method. This single crystal silicon cell has the maximum photoelectric conversion efficiency of the solar battery cell at a wavelength of around 800 nm.
However, as the transparent conductive film on the surface of the n-type silicon layer, a 100 nm thick amorphous hydrogen-doped indium oxide (In ₂ O ₃ ) transparent conductive film is deposited by magnetron sputtering.

Next, the single crystal gallium arsenide solar battery cell 18 is manufactured by the following procedure.
On a semi-insulating gallium arsenide substrate 44 with a thickness of 0.3 mm, p + type aluminum gallium arsenide (Al _0.3 Ga _0.7 As) having a thickness of 500 nm and a carrier concentration of 1 × 10 ¹⁸ cm ⁻³ by metal organic chemical vapor deposition (MOCVD) 45, p + type aluminum arsenide (AlAs) 46 having a thickness of 5 nm, p-type gallium arsenide (GaAs) 47 having a thickness of 1 μm and a carrier concentration of 1 × 10 ¹⁷ cm ⁻³ , n-type having a thickness of 500 nm and a carrier concentration of 3 × 10 ¹⁸ cm ⁻³ Gallium arsenide (GaAs) 48, n + type aluminum gallium arsenide (Al _0.3 Ga _0.7 As) 49 having a thickness of 50 nm and carrier concentration of 1 × 10 ¹⁸ cm ⁻³ , and n + type gallium arsenide (GaAs) 48 having a thickness of 50 nm are successively grown. The growth method is not limited to the MOCVD method, and may be a molecular beam epitaxy (MBE) method.

  Then, by photolithography and etching, tapered holes that become narrower from 0.02 mm to 0.1 mm in diameter from the back side of the gallium arsenide substrate are two-dimensionally spaced from 1 mm to 2 mm until reaching the aluminum arsenide (AlAs) layer. Open. Here, when a 4-to-1 mixture of citric acid and hydrogen peroxide is used as the etchant and etching is performed for 100 minutes, the aluminum arsenide layer serves as a stopper and the etching automatically stops.

Similarly, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film 6 is deposited on the back surface of the gallium arsenide substrate by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the p + type aluminum arsenide layer. Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film.

  Single crystal gallium arsenide solar cells have high photoelectric conversion efficiency for light with a wavelength of 880 nm or less.

(Joining)
The single crystal silicon solar battery cell 17 and the single crystal gallium arsenide solar battery cell 18 thus fabricated are joined in the following procedure.
Plasma treatment is performed on each transparent conductive film formed on the back surface of the single crystal gallium arsenide solar cell and the surface of the single crystal silicon solar cell.
Next, two cells are stacked in the order of single-crystal gallium arsenide solar cell and single-crystal silicon solar cell so that the plasma-treated amorphous and polycrystalline transparent conductive films are combined. The subsequent joining procedure is the same as in the first embodiment.
The comb-shaped or lattice-shaped aluminum electrode 1 is formed on the gallium arsenide on the upper surface of the stacked two-junction cell, and the aluminum electrode 1 is formed on the entire lower surface of the silicon substrate by vacuum evaporation.

(Function)
When the multi-junction solar cell shown in FIG. 5 is irradiated with sunlight from above, the spectral component having a wavelength of 880 nm or less is mainly absorbed by the single-crystal gallium arsenide solar cell and transmitted through the long wavelength. The spectral component on the side is absorbed by the single crystal silicon solar cell. Here, the semi-insulating gallium arsenide substrate has little drude absorption by free carriers and is transparent to light with a wavelength of 900 nm or more, and the transparent conductive film is also transparent in the light wavelength region of interest. There is no loss. The sunlight components absorbed in each cell are converted into currents and connected in series with a transparent conductive film, so that the combined power can be efficiently extracted from the upper and lower electrodes.

  In this embodiment, a stacked structure of single crystal silicon solar cells and single crystal gallium arsenide solar cells formed on a silicon substrate is shown, but a single crystal of silicon or germanium is used instead of the single crystal silicon solar cells. Any of single-crystal thin film solar cells of germanium, silicon germanium, silicon tin or silicon germanium tin formed on the substrate may be used, and microcrystalline silicon germanium solar cells formed on the glass substrate are used. May be. Instead of the single crystal gallium arsenide solar cell, a single crystal indium gallium phosphide solar cell formed on a semi-insulating gallium arsenide substrate may be used. Moreover, although the structure of the 2 junction cell was shown in the present Example, the same effect can be anticipated even if it is 3 junctions or more. The order of the p-type layer and the n-type layer may be reversed as a whole. Further, an antireflection film or an intermediate reflection film for a specific wavelength region may be superimposed on the transparent conductive film as long as it does not hinder the bonding.

  In this embodiment, microcrystalline silicon germanium solar cells or amorphous silicon solar cells are replaced with chalcopyrite solar cells in the first embodiment.

<Manufacturing method>
A chalcopyrite solar cell is produced by the following procedure.
A soda-lime glass substrate with a thickness of 0.3 mm is two-dimensionally spaced from 1 mm to 2 mm by irradiating femtosecond laser light into a tapered hole that becomes narrower as the diameter increases from 0.02 mm to 0.1 mm at a depth of 0.25 mm. Open to. A zinc oxide transparent conductive film doped with gallium oxide is deposited to a thickness of 300 nm on the surface of the glass substrate on which holes are not formed by high frequency sputtering. Next, n-type sulfur sulfide is deposited by a resistance heating vapor deposition method to a thickness of 50 nm, and a chalcopyrite compound (Cu (In, Ga) (S, Se) ₂ ) having a desired composition is added to each element at a thickness of 1.5 μm. It is deposited by the simultaneous vapor deposition method. The chalcopyrite compound may be deposited by sputtering or selenization / sulfurization.

  On this chalcopyrite layer, an amorphous dominant hydrogen-doped indium oxide transparent conductive film having a thickness of 100 nm is deposited by magnetron sputtering. Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film. Next, after masking portions other than the opening on the back surface (surface with holes) of the glass substrate with a resist or the like, the glass is etched with diluted hydrofluoric acid, and the holes are penetrated until the transparent conductive film is exposed. Further, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is similarly deposited on the rear surface of the glass by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the transparent conductive film on the glass surface.

  Here, the transparent conductive film is not limited to zinc oxide or indium oxide, but is not limited to tin (Sn), titanium (Ti), zirconium (Zr), hafnium (Hf), molybdenum (Mo), tungsten (W), etc. Indium oxide-based metal oxide, zinc oxide-based metal oxide, gallium oxide-based metal oxide, tin oxide-based metal oxide, magnesium oxide-based metal oxide, cadmium oxide-based metal oxide containing an element having a valence higher than the valence Or two or more metal oxides selected from the above metal oxides. Further, the method of depositing the transparent conductive film is not limited to the sputtering method, but may be a chemical vapor reaction method that is more suitable for embedding in the through hole. Further, the method for drilling the glass substrate is not limited to the femtosecond laser, and sandblasting, etching, or a mechanical drill may be used.

  The chalcopyrite solar cell produced in this way is replaced with the microcrystalline silicon germanium solar cell or the amorphous silicon solar cell in the first embodiment according to the distribution of its light absorption spectrum, and is laminated and bonded. . The joining method and the electrode forming method are the same as in the first embodiment.

(Function)
When the multi-junction solar cell manufactured as described above is irradiated with sunlight from the upper surface, the short wavelength spectral component is sequentially absorbed by the upper solar cell, and the long wavelength component that has passed through it is sequentially applied to the lower solar cell. Absorbed by the cell. Here, the glass substrate and the transparent conductive film are transparent in the light wavelength region of interest, and almost no loss occurs due to absorption. The sunlight components absorbed in each cell are converted into currents and connected in series with a transparent conductive film, so that the combined power can be efficiently extracted from the upper and lower electrodes.

  In addition, although the structure of the 3 junction cell was shown in the present Example, the same effect can be anticipated by the same structure even if it is 2 junctions or 4 junctions or more. Further, the composition of silicon germanium may be a composition other than that shown in this embodiment, or a composition containing only silicon or germanium. Further, chalcopyrite compound cells having different compositions may be stacked in two stages. The order of the p-type layer and the n-type layer may be reversed as a whole. Further, an antireflection film or an intermediate reflection film for a specific wavelength region may be superimposed on the transparent conductive film as long as it does not hinder the bonding.

  In this embodiment, the amorphous silicon solar battery cell is replaced with an indium gallium nitride solar battery cell in the first embodiment, and the p-type layer and the n-type of the single crystal silicon germanium solar battery cell and the microcrystalline silicon germanium solar battery cell are used. Layers are stacked in reverse order.

<Manufacturing method>
The indium gallium nitride solar battery cell is manufactured by the following procedure.
A 0.3mm-thick sapphire (Al ₂ O ₃ ) substrate is irradiated with YAG laser light with a power of 100W and a pulse width of 1ms in a tapered hole that becomes 0.25mm deep and narrows as the diameter increases from 0.02mm to 0.1mm. Open 2D at intervals of 1mm to 2mm. On the non-perforated surface of this glass substrate, n + -type gallium nitride (GaN) with a thickness of 1 μm, carrier concentration 5 × 10 ¹⁸ cm ⁻³ , and 200 nm i (by metal organic chemical vapor deposition (MOCVD) Undoped) type indium gallium nitride (In _0.05 Ga _0.95 N), p-type gallium nitride (GaN) with a thickness of 100 nm and a carrier concentration of 5 × 10 ¹⁷ cm ⁻³ are grown sequentially. The growth method is not limited to the MOCVD method, and a hydride vapor phase growth (HVPE) method may be used.

  Next, the back surface (surface with holes) of the sapphire substrate is etched with a 1: 3 mixture of sulfuric acid and phosphoric acid at a temperature of 150 ° C. for 5 hours to penetrate the holes until the gallium nitride layer is exposed. Further, a 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is similarly deposited on the back surface of sapphire by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the transparent conductive film on the glass surface.

  Here, the transparent conductive film is not limited to indium oxide, but is positive tetravalent such as tin (Sn), titanium (Ti), zirconium (Zr), hafnium (Hf), molybdenum (Mo), tungsten (W), etc. Indium oxide-based metal oxides, zinc oxide-based metal oxides, gallium oxide-based metal oxides, tin oxide-based metal oxides, magnesium oxide-based metal oxides, cadmium oxide-based metal oxides containing elements having the above valences Alternatively, two or more metal oxides selected from the metal oxides may be used. Further, the method of depositing the transparent conductive film is not limited to the sputtering method, but may be a chemical vapor reaction (CVD) method that is more suitable for embedding in the through hole. Further, the method of drilling the sapphire substrate is not limited to the YAG laser, and sand blasting or a mechanical drill may be used.

Single crystal indium gallium nitride solar cells have high photoelectric conversion efficiency with respect to light having a wavelength of 400 nm or less.
The manufacturing method of the single crystal silicon germanium solar cell and the microcrystalline silicon germanium solar cell is the same except that the p-type layer and the n-type layer are replaced in the first embodiment.

The single crystal silicon germanium solar cell, the microcrystalline silicon germanium solar cell and the single crystal indium gallium nitride solar cell thus fabricated are stacked in this order, and joined in the same procedure as in the first embodiment.
Comb-like or lattice-like nickel (Ni) electrodes are formed on the gallium nitride layer on the upper surface of the laminated three-junction cell, and silver (Ag) or aluminum (Al) electrodes reaching the back of the through-holes on the entire glass substrate on the lower surface. These are formed by vacuum deposition.

(Function)
When the multi-junction solar cell manufactured as described above is irradiated with sunlight from the upper surface, a spectral component having a wavelength of 400 nm or less is mainly absorbed by the single-crystal indium gallium nitride solar cell, and the wavelength of the spectral component transmitted therethrough is the wavelength. Spectral components near 650 nm and shorter wavelengths are mainly absorbed by microcrystalline silicon germanium solar cells, and the longer-wavelength spectral components transmitted through it are absorbed by single-crystal silicon germanium solar cells centered around 1 μm wavelength. Is done. Here, the sapphire substrate, the glass substrate, and the transparent conductive film are transparent in the region of the light wavelength of interest, and almost no loss due to absorption occurs. The sunlight components absorbed in each cell are converted into currents and connected in series with a transparent conductive film, so that the combined power can be efficiently extracted from the upper and lower electrodes.

  In the present embodiment, the configuration of a three-junction cell is shown, but the same effect can be expected with the same configuration even when there are two or four junctions. Further, the composition of silicon germanium may be a composition other than that shown in this embodiment, or a composition containing only silicon or germanium. Further, single crystal indium gallium nitride cells having different compositions may be stacked in two stages. Further, an antireflection film or an intermediate reflection film for a specific wavelength region may be superimposed on the transparent conductive film as long as it does not hinder the bonding.

  In this embodiment, the amorphous silicon solar battery cell is replaced with an organic thin film solar battery cell in the first embodiment.

<Manufacturing method>
Next, an organic thin-film solar battery cell is produced according to the following procedure.
A 300 nm thick amorphous amorphous hydrogen-doped indium oxide transparent conductive film is deposited on a polyimide substrate having a thickness of 0.3 mm by magnetron sputtering. Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film. Next, a polyethylene dioxythiophene: polysulfonic acid styrene (PEDOT: PSS) film having a thickness of 30 nm is formed by spin coating and heat drying. Then, zinc phthalocyanine (ZnPc) having a thickness of 25 nm, fullerene (C60) having a thickness of 25 nm, and bathocuproine (BCP) having a thickness of 6 nm are sequentially deposited by vacuum deposition. The deposition method is not limited to the vacuum vapor deposition method, and may be a spray coating method.

  Thereafter, by photolithography and etching, tapered holes that become narrower as the diameter becomes deeper from 0.02 mm to 0.1 mm from the back surface of the polyimide substrate are two-dimensionally opened at intervals of 1 mm to 2 mm until reaching the transparent conductive film. Here, as the etching solution, an alkaline aqueous solution (for example, polyimide etching solution “TPE-3000” manufactured by Toray Engineering Co., Ltd.) containing caustic alkali and an organic amine compound as main components is used.

  A 300 nm thick amorphous hydrogen-doped indium oxide transparent conductive film having a thickness of 300 nm is similarly deposited on the back surface of the polyimide substrate by magnetron sputtering. The transparent conductive film on the back surface is also embedded in the through hole and is in electrical contact with the transparent conductive film on the substrate surface. Thereafter, annealing is performed in vacuum at 200 ° C. for 2 hours to polycrystallize the transparent conductive film.

  This organic thin film solar cell has high photoelectric conversion efficiency with respect to light having a wavelength of around 550 nm.

The organic thin-film solar battery thus produced is replaced with an amorphous silicon solar battery cell in the first embodiment, and bonded in the same procedure as in the first embodiment.
Comb-like or lattice-like magnesium-silver alloy (Mg: Ag) electrodes are formed on the BCP layer on the top surface of the laminated three-junction cell, and silver (Ag) or aluminum ( Al) electrodes are formed by vacuum deposition.

(Function)
When the multi-junction solar cell fabricated as described above is irradiated with sunlight from the upper surface, the spectral components near and shorter than the wavelength of 550 nm are mainly absorbed by the organic thin-film solar cell, and the spectral components transmitted through it are transmitted. Among them, spectral components near 650 nm and shorter wavelengths are mainly absorbed by microcrystalline silicon germanium solar cells, and the spectral components on the long wavelength side that have passed through them are single-crystal silicon germanium solar cells centered around 1 μm wavelength. To be absorbed. Here, the polyimide substrate, the glass substrate, and the transparent conductive film are transparent in the region of the light wavelength of interest, and almost no loss due to absorption occurs. The sunlight components absorbed in each cell are converted into currents and connected in series with a transparent conductive film, so that the combined power can be efficiently extracted from the upper and lower electrodes.

  In addition, although the structure of the 3 junction cell was shown in the present Example, the same effect can be anticipated by the same structure even if it is 2 junctions or 4 junctions or more. The composition and configuration of the organic thin film are not limited to this example. Further, the composition of silicon germanium may be a composition other than that shown in this embodiment, or a composition containing only silicon or germanium. The order of the p-type layer and the n-type layer may be reversed as a whole. Further, an antireflection film or an intermediate reflection film for a specific wavelength region may be superimposed on the transparent conductive film as long as it does not hinder the bonding.

  The multi-junction type light-receiving element according to the present invention is realized by adjusting the size of the element and the arrangement of the electrodes in accordance with the requirements of the light-receiving area and the response speed in the same configuration as the above-described multi-junction type solar cell embodiment. The Since light receiving elements having different response wavelength spectra are stacked and electrically connected via a transparent conductive film, photoelectric conversion can be efficiently performed on incident light having a wide spectrum in a small area.

The multi-junction light-emitting device according to the present invention is realized by stacking and electrically connecting light-emitting devices having different emission spectra by the same joining method as in the above-described multi-junction solar cell embodiment. For example, red-emitting aluminum gallium arsenide (AlGaAs) diodes formed on semi-insulating gallium arsenide (GaAs) substrates and green-emitting nitrogen-doped gallium phosphide formed on semi-insulating gallium phosphide (GaP) substrates. When a blue light-emitting indium gallium nitride (InGaN) diode formed on a (GaP: N) diode and a sapphire (Al ₂ O ₃ ) substrate is bonded via a transparent conductive film, the light emission of each color is almost absorbed by the substrate. Since the light is synthesized from the surface of indium gallium nitride without emitting light, a white light emitting element with a small area can be realized.

  The multi-junction solar cell according to the present invention can be used for a solar cell that efficiently uses the spectrum of sunlight and has high photoelectric conversion efficiency and low loss of electrical connection. The multi-junction light-receiving element according to the present invention can be used for a small light-receiving element that efficiently distributes and detects incident light having a wide spectrum. The multi-junction light emitting device according to the present invention can be used for a small light emitting device that efficiently emits light having a wide spectrum.

1, metal electrode 2, glass substrate 3, p-type single crystal silicon film or germanium film 4, i-type single crystal silicon germanium film 5, n-type single crystal silicon germanium film 6, transparent conductive film 8, p-type microcrystalline silicon film 9, i-type microcrystalline silicon germanium film or silicon film 10, n-type microcrystalline silicon film 13, p-type amorphous silicon film 14, i-type amorphous silicon film 15, n-type amorphous silicon film 17, first solar cell 18 , Second solar cell 19, third solar cell 20, through-hole 42, n-type single crystal silicon diffusion layer 43, p-type single crystal silicon substrate 44, semi-insulating gallium arsenide substrate 45, p-type aluminum arsenide Gallium film 46, p-type aluminum arsenide film 47, p-type gallium arsenide film 48, n-type gallium arsenide film 49, n-type arsenide Minium gallium film 51, solar cell first cell 52, insulating film 53, opening hole 54, solar cell second cell 60, transparent electrode film 61, single crystal silicon substrate 62, transparent epoxy resin 63, metal electrode 65, single crystal silicon solar cell 66, insulating transparent substrate 67, chalcopyrite compound thin film 68, chalcopyrite solar cell

Claims (14)

A multi-junction solar cell in which a plurality of solar cells having different light absorption spectra are stacked and electrically connected,
Each of the solar cells has an individual transparent substrate, a semiconductor layer on the surface side of the substrate, and an upper transparent conductive film on the surface of the semiconductor layer,
The transparent substrate of at least one of the solar cells has a through hole ,
The inside of the through hole of the transparent substrate and the back surface of the transparent substrate are covered with a lower transparent conductive film by the same process,
The upper transparent conductive film provided on the surface side of the one solar battery cell and the lower transparent conductive film formed on the back surface of the transparent substrate of another solar battery cell are joined,
The solar cell is a multi-junction solar cell characterized in that each cell is laminated and joined in the order of absorption wavelength so that light enters from the cell having the shortest light absorption wavelength. 2. The multi-junction solar cell according to claim 1, wherein at least one of the solar cells is a solar cell excluding an end solar cell opposite to a side where light is incident. battery. The multi-junction solar cell according to claim 1, wherein the transparent substrate is selected from one or more of a glass substrate, a resin substrate, a polycrystalline substrate, and a single crystal substrate. 2. At least one of the solar cells is made of a single crystal thin film of silicon, germanium, silicon germanium, silicon tin or silicon germanium tin formed on a glass substrate. Multi-junction solar cell. 2. The multi-junction solar cell according to claim 1, wherein at least one of the solar cells comprises a microcrystalline thin film of silicon or silicon germanium formed on a glass substrate. 2. The multi-junction solar cell according to claim 1, wherein at least one of the solar cells is made of an amorphous thin film of silicon or silicon carbide formed on a glass substrate. At least one of the solar cells is composed of a single crystal thin film of silicon, germanium, silicon germanium, silicon tin or silicon germanium tin formed on a silicon or germanium single crystal substrate. The multijunction solar cell according to claim 1. 2. At least one of the solar cells is made of a single crystal thin film of gallium arsenide, gallium arsenide, or indium gallium phosphide formed on a gallium arsenide single crystal substrate. The multijunction solar cell described. 2. The multi-junction solar cell according to claim 1, wherein at least one of the solar cells comprises a single crystal thin film of indium gallium nitride formed on a sapphire substrate. 2. The multi-junction solar cell according to claim 1, wherein at least one of the solar cells is a chalcopyrite thin film formed on a soda lime glass substrate. The multi-junction solar cell according to claim 1, wherein at least one of the solar cells is made of an organic thin film formed on a transparent plastic substrate. The said transparent conductive film consists of a metal oxide containing the 1 type (s) or 2 or more types selected from an indium oxide, a tin oxide, a zinc oxide, a gallium oxide, magnesium oxide, or cadmium oxide. Multi-junction solar cell. In a multi-junction type light receiving element in which a plurality of light receiving elements having different light absorption spectra are stacked and electrically connected,
Each of the light receiving elements has an individual transparent substrate, a semiconductor layer on the surface side of the substrate, and an upper transparent conductive film on the surface of the semiconductor layer ,
The transparent substrate of at least one of the light receiving elements has a through hole,
The inside of the through hole of the transparent substrate and the back surface of the transparent substrate are covered with a lower transparent conductive film by the same process,
The upper transparent conductive film provided on the surface side of the one light receiving element and the lower transparent conductive film formed on the back surface of the transparent substrate of the other light receiving element are joined,
A multi-junction type light receiving element, wherein the light receiving elements are laminated and joined in order of absorption wavelength so that light enters from the light receiving element having the shortest light absorption wavelength. In a multi-junction light emitting device in which a plurality of light emitting devices having different emission spectra are stacked and electrically connected,
Each of the light emitting elements has an individual transparent substrate, a semiconductor layer on the surface side of the substrate, and an upper transparent conductive film on the surface of the semiconductor layer ,
The transparent substrate of at least one of the light emitting elements has a through hole,
The inside of the through hole of the transparent substrate and the back surface of the transparent substrate are covered with a lower transparent conductive film by the same process,
The upper transparent conductive film provided on the surface side of the one light emitting element and the lower transparent conductive film formed on the back surface of the transparent substrate of the other light emitting element are joined,
Multijunction light emitting device emitting element characterized in that it is joined by laminating the light emitting elements in the order of the emission wavelength so that the light from the shortest light-emitting device having an emission wavelength is emitted.

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