JP6261088B2 - Photoelectric conversion device, building and electronic equipment - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a photoelectric conversion device, a building, and an electronic device. For example, the photoelectric conversion device suitable for use as a solar cell installed on a building window or a display of various electronic devices, and the photoelectric conversion device are used. It relates to buildings and electronic equipment.

  In order not only to prevent global warming, but also to pass the green earth in harmony with the natural environment to the next generation, as a key technology for the future recycling society, more effective use of sunlight is desirable. It is. From this point of view, solar cells are attracting attention worldwide, and active research and development are being carried out in order to improve photoelectric conversion efficiency and reduce manufacturing costs.

  As a conventional solar cell, a solar cell using amorphous or crystalline silicon, a solar cell using GaAs crystal, a solar cell using an organic semiconductor, and the like are known. These solar cells have a structure in which a pn junction composed of a p-type semiconductor layer and an n-type semiconductor layer is sandwiched between an anode electrode and a cathode electrode, and sunlight is vertically incident on the junction surface of the pn junction. Are common (see, for example, Non-Patent Document 1).

  This conventional solar cell is shown in FIG. As shown in FIG. 1, in this conventional solar cell, a p-type semiconductor layer 151 and an n-type semiconductor layer 152 form a pn junction, an anode electrode 153 is formed on the p-type semiconductor layer 151, and an n-type semiconductor is formed. A cathode electrode 154 is formed on the layer 152 and has a plate-like shape as a whole. In this solar cell, the traveling direction of the light 156 incident perpendicularly to one main surface 155, and the cathode electrode 154 and the electrons and holes generated in the pn junction by the incidence of the light 156 are caused by drift or diffusion, respectively. The direction toward the anode electrode 153, in other words, the net moving direction of the carriers is parallel. For this reason, if the p-type semiconductor layer 151 and the n-type semiconductor layer 152 are made thick in order to sufficiently absorb the light 156, the distance between the anode electrode 153 and the cathode electrode 154 becomes large. It has been extremely difficult to achieve both an increase in absorption and an improvement in carrier collection efficiency, and this has hindered improvement in photoelectric conversion efficiency. That is, in the conventional solar cell, the number of absorbed photons and the photocarrier collection efficiency both depend on the electrode spacing, in other words, the total thickness d of the p-type semiconductor layer 151 and the n-type semiconductor layer 152, and have a trade-off relationship. Therefore, the photoelectric conversion efficiency η behaves as shown by the thick solid line in FIG. Moreover, since many conventional solar cells are mass-productive and use a single band gap, the photoelectric conversion efficiency is theoretically at most 30% as shown by the solid line in FIG. There was a problem that could only be obtained. To make up for this, there are attempts to make solar cells into a stack structure, or to construct a solar cell using a multi-junction structure or multiple types of semiconductors with different band gaps. There is a problem that area-ization is not easy. Theoretically, as shown in FIG. 3, high efficiency of about 60% can be obtained by using N = 10, that is, a band gap of 10 steps.

On the other hand, for the purpose of significantly improving photoelectric conversion efficiency, a solar cell of a type in which sunlight is incident in parallel to the joint surface of a pn junction has recently been proposed (for example, see Patent Document 1). In this solar cell, an anode electrode and a cathode electrode are formed in a spiral shape with a pn junction composed of a p-type semiconductor layer and an n-type semiconductor layer interposed therebetween, and have a thin disk shape as a whole. . The band gap E _g of the p-type semiconductor layer and the n-type semiconductor layer decreases stepwise from the light incident surface in the thickness direction of the disk in n steps (n ≧ 2). _g1 , _Eg2 ,..., _Egn ( _Eg1 > _Eg2 >...> _Egn ).

FIG. 4 shows an example of a solar cell described in Patent Document 1 manufactured by a roll-to-roll process, and shows a cross section in the diameter direction of a disk. In order to manufacture this solar cell, an anode electrode, a semiconductor layer, and a cathode electrode of a solar cell are formed on a transparent resin base film, and a spiral structure is formed while the base film is wound. As shown in FIG. 4, in this solar cell, anode electrodes 202, 203, 204, and 205 are sequentially formed in the width direction of the base film 201 (the thickness direction of the disk). These anode electrodes 202, 203, 204, and 205 are formed to be elongated in the longitudinal direction of the base film 201. On the anode electrodes 202, 203, 204, 205, a region 206 made of a semiconductor having band gaps E _g of E _g1 , E _g2 , E _g3 , E _g4 (E _g1 > E _g2 > E _g3 > E _g4 ), respectively. , 207, 208, and 209 are formed. A cathode electrode 210 which is a full-surface electrode is formed on the surface of these regions 206, 207, 208 and 209 opposite to the anode electrodes 202, 203, 204 and 205. Here, the width in the thickness direction of the disk in the regions 206, 207, 208, and 209 is typically about several tens of μm, and the width in the diameter direction of the disk is typically about 150 nm. On the other hand, in FIG. 4, the thickness of the base film 201 is drawn extremely small for convenience of illustration, but the thickness of the base film 201 is about 100 μm, for example, and the regions 206, 207, 208, and 209 are drawn. It is about three orders of magnitude larger than the width of the disk in the diameter direction.

  Although it relates to a solar cell using a single substance as a photoelectric conversion material, there is a report aiming at improvement of photoelectric conversion efficiency in consideration of light propagation without using a condensing system (Non-Patent Document 2, 3). In addition, when a condensing system using a lens or the like is used, the area of the element can be reduced relative to the area that receives sunlight, and the photoelectric conversion efficiency can be improved by increasing the number of photons by condensing. As is known, the temperature of the solar cell also rises due to light collection, leading to a decrease in photoelectric conversion efficiency.

Japanese Patent No. 4022631

D.J.Friedman, J.F.Geisz, S.R.Kurtz, and J.M.Olson, July 1998 ・ NREL / CP-520-23874 Efficiency enhancement in Si solar cells by textured photonic crystal back reflector, L. Zeng, et.al., Appl. Phys. Lett. 89, 111111 _2006_ Conversion of Light Propagation Direction for Highly Efficient Solar Cells, Ikuo Suemune, Applied Physics Express 4, 102301 (2011) [Search on October 13, 2012] Internet <URL: http://www.hikari-energy.jp/websheetouyou.pdf> [October 11, 2013 search] Internet <URL: http://www.brl.ntt.co.jp/J/activities/file/report02/J/report15.html> Japan Society for the Promotion of Science 69 Committee for the Study of the Society of Resources and Materials March 21, 2013 Reference 6-4 NEDO [Search October 11, 2013] Internet <URL: http://www.aist.go.jp/aist_j/new_research/nr20080829/nr20080829.html> [Search on October 11, 2013], Internet <URL: http://www.nedo.go.jp/content/100092910.pdf> [October 11, 2013 search] Internet <URL: http://www.nedo.go.jp/content/100086784.pdf> [Search October 11, 2013], Internet <URL: http://hashi.shinshu-u.ac.jp/research/research2/research2.html> M.Liu, M.B.Jonson, and H.J.Snaith, Nature, published online 11 Sep.2013, doi: 10.1038 / nature12509 KURENAI: Kyoto University Research Information Repository [searched on October 11, 2013], Internet <URL: http://hdl.handle.net/2433/120869> Sci. Technol. Adv. Mater. 11 (2010) 044305 (23pp) doi: 10.1088 / 1468-6996 / 11/4/044305 Kentaro Imamura, Francisco C. Franco, Jr., Taketoshi Matsumoto, and Hikaru Kobayashi, ochoch Ultra-low reflectivity coated siliconsurfaces formed by surface structure chemical transfer method ", APPLIED PHYSICSLETTERS 103, 013110 (2013)

  However, in the solar cell shown in FIG. 4, light perpendicularly incident on one surface of the disk passes through the transparent base film 201 and escapes to the outside from the other surface of the disk. Does not contribute anything. That is, it can be seen that the base film 201 is insensitive to incident light, but the area of the end face of the base film 201 in the area of the disk, that is, the ratio of the area of the insensitive area is extremely large. This restricted the photoelectric conversion efficiency of this solar cell. In addition, since there is a path through which sunlight is guided in the base film 201 and directly enters a semiconductor region located in the deep part, when the semiconductor in the deep part is amorphous silicon, photoelectric conversion of the solar cell is caused by light incidence. When there is a so-called Stebbler-Lonsky (SW) effect that lowers the efficiency and the deep semiconductor is an organic semiconductor, there is a problem of deterioration of the organic semiconductor due to the ultraviolet component of sunlight. This problem is the same in general amorphous silicon solar cells. In addition, the amorphous silicon solar cell has a problem that even if the thickness of the semiconductor layer is increased, the internal electric field is reduced by the space charge effect, and the characteristics are not improved.

  Therefore, the problem to be solved by the present invention is that the insensitive area for incident light can be eliminated, deterioration of the organic semiconductor due to the Stebbler-Lonsky effect and ultraviolet components can be suppressed, and extremely high photoelectric conversion efficiency can be obtained. It is possible to provide a photoelectric conversion device suitable for use as a solar cell and the like, and a building and an electronic device using this excellent photoelectric conversion device, which can be increased in area and extremely easily.

  Another problem to be solved by the present invention is that, in the concentrating solar power generation, the temperature increase as a by-product due to the introduction of the condensed light cancels out the photoelectric conversion efficiency that is higher than that in the case without the original condensing. It is providing the photoelectric conversion apparatus which can prevent that.

  Further, another problem to be solved by the present invention is that, in concentrating solar power generation using a lens or the like, the photoelectric conversion efficiency decreases when the direct sunlight of the sun is lost, that is, when the diffused light becomes main. However, it is an object of the present invention to provide a photoelectric conversion device that can solve this problem.

In order to solve the above problems, the present invention provides:
A structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light;
A planar optical waveguide for guiding the two-dimensional spatial propagation light;
Having a semiconductor layer for photoelectric conversion provided at an end of the planar optical waveguide,
The light incident on the main surface of the planar optical waveguide is configured to be guided in the planar optical waveguide and incident on the semiconductor layer,
A net traveling direction of light guided in the planar optical waveguide, and a net moving direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from an end surface of the planar optical waveguide; The photoelectric conversion device is characterized in that the angle θ formed by is substantially a right angle.

  Typically, the planar optical waveguide and the semiconductor layer are provided integrally with each other, and, for example, their ends are joined together. A first electrode and a second electrode are provided on a pair of surfaces of the semiconductor layer facing each other. One of the first electrode and the second electrode is used as an anode electrode, and the other is used as a cathode electrode.

  Specifically, for example, π / 2−δ ≦ θ ≦ π / 2 + δ is selected as θ. However, although δ is used as the anode electrode of the first electrode and the second electrode, the ratio of the thickness of the semiconductor layer to the width (electrode width) in the direction parallel to the light traveling direction in the semiconductor layer Δ to semiconductor layer thickness / electrode width.

  The structure for converting the three-dimensional spatially propagated light into the two-dimensional spatially propagated light includes, for example, a first band-shaped portion and a second band-shaped portion having different refractive indexes alternately periodically or at regular intervals. It has an ordered structure. The structure that converts the three-dimensional spatially propagated light into two-dimensional spatially propagated light is typically provided in the main surface of the planar optical waveguide or in the planar optical waveguide. Specifically, the structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light is, for example, a main surface of a planar optical waveguide or a diffraction grating provided in the planar optical waveguide. This diffraction grating can be formed by a conventionally known method. For example, a material having a refractive index different from that of the planar optical waveguide, in which convex portions are periodically formed on the main surface of the planar optical waveguide by imprint technology, or concave portions are periodically formed on the main surface. The diffraction grating can be formed by embedding or changing the refractive index by ion exchange. Alternatively, a transparent plastic film in which a diffraction grating having a periodic structure is formed can be attached to the main surface of the planar optical waveguide. On the structure that converts the three-dimensional spatially propagated light into the two-dimensional spatially propagated light, a light wave traveling direction converting sheet (see, for example, Non-Patent Document 4; referred to as a condensing sheet in Non-Patent Document 4). Is provided).

  The planar optical waveguide may be a planar optical waveguide or a curved optical waveguide. The planar shape of the planar optical waveguide is selected as necessary, but typically has a quadrangular shape, for example, a rectangular shape or a square shape. In this case, a semiconductor layer is provided at an end of the planar optical waveguide corresponding to at least one of a pair of opposite sides of the rectangular optical waveguide. A light reflection mechanism is provided at the end of the planar optical waveguide corresponding to at least one of a pair of sides different from the pair of sides facing each other. In this case, the light incident on the main surface of the planar optical waveguide is reflected when entering the light reflecting mechanism when guided in the planar optical waveguide, and the optical path is bent in the direction toward the semiconductor layer. The amount of light incident on the end face of the semiconductor layer increases.

  Preferably, the light is not directly incident on the semiconductor layer when the light is incident on the main surface of the planar optical waveguide. In other words, when light is incident on the main surface of the photoelectric conversion device, the light is incident on the main surface of the planar optical waveguide, but the light is not directly incident on the surface of the semiconductor layer. By doing so, it is possible to prevent the temperature of the semiconductor layer from being increased due to light that is directly incident on the semiconductor layer, thereby preventing deterioration of the characteristics of the semiconductor layer, and thus dissipating as heat. Coupled with the low energy, the photoelectric conversion efficiency of the photoelectric conversion device can be prevented from being lowered, and high photoelectric conversion efficiency can be obtained.

  Since the thickness of the planar optical waveguide is generally larger than the thickness of the semiconductor layer, it is preferably guided in the planar optical waveguide in order to effectively use the light guided in the planar optical waveguide. The collected light is collected and incident on the semiconductor layer. For this purpose, for example, the planar optical waveguide has a portion (having the same thickness as the semiconductor layer) in which the light guided in the planar optical waveguide is in contact with the semiconductor layer of the planar optical waveguide. For example, a refractive index profile that is collected asymptotically is provided. That is, the light guided in the planar optical waveguide is guided according to the refractive index distribution of the planar optical waveguide, and thus is collected asymptotically to the portion that contacts the semiconductor layer while being guided.

  The semiconductor layer is made of an inorganic semiconductor or an organic semiconductor, and is typically a pn junction made of a p-type semiconductor layer and an n-type semiconductor layer. The thickness of the semiconductor layer is appropriately selected as a function of the diffusion length of carriers in the semiconductor layer, and is typically 10 nm or more and 100 μm or less. The semiconductor constituting the semiconductor layer may be amorphous (amorphous), polycrystalline, or single crystal.

Examples of inorganic semiconductors include II-VI group compound semiconductors such as CdSe, PbS, PbSe, and PbTe, III-V group compound semiconductors such as GaSb, InAs, InN, AlInN, GaInN, GaN, AlGaN, GaAsN, and GaPN, and Si and SiGe. Group IV semiconductors such as Si _x Ge _y Sn _1-xy O, SiN _x , SiO _x , CIS (CuInSe), CIGS (CuInGaSe), CuInGaSeTe, and the like can be used (see, for example, Non-Patent Documents 5 to 10). ). These semiconductors are characterized in that the band gap can be controlled, for example, by controlling the composition ratio of group III elements such as In and Ga or mixing sulfur (S). The semiconductor layer can also be constituted by fine particles made of these inorganic semiconductors.

As the organic semiconductor, all materials generally reported as organic solar cell materials can be used. Specifically, polyacenes such as pentacene, polyacetylene (preferably disubstituted polyacetylene), poly (p -Phenylene vinylene), poly (2,5-thienylene vinylene), polypyrrole, poly (3-methylthiophene), polyaniline, poly (9,9-dialkylfluorene) (PDAF), poly (9,9-dioctylfluorene- co-bithiophene) (F8T2), poly (1-hexyl-2-phenylacetylene) (PH _X PA) (shows blue light emission as the light emitting material), poly (diphenylacetylene) derivative (PDPA- _n Bu) (light emission) The materials are green light emission), poly (pyridine) (PPy), poly (pyridylbi) Ren) (PPyV), cyano-substituted poly (p-phenylenevinylene) (CNPPV), poly (3,9-di-tert-butylindeno [1,2-b] fluorene (PIF), etc. can be used. As for the dopant of the organic semiconductor, alkali metals (Li, Na, K, Cs) can be used as donors, and halogens (Br ₂ , I ₂ , CI ₂ ), Lewis acids (BF ₃ , PF ₅ , AsF ₅ , SbF ₅ , SO ₃ ), transition metal halides (FeCl ₃ , MoCl ₅ , WCl ₅ , SnCl ₄ ), TCNE, TCNQ can be used as organic acceptor molecules, and electrochemical doping. dopant ions used in the tetraethylammonium ions as cations (TEA ^+), tetrabutylammonium Ion ^{(TBA +), Li +,} Na +, K +, ClO 4 as the anion ^{_{-, BF 4 -, PF 6}} -, AsF 6 -, SbF 6 -. Or the like can be used as the organic semiconductor In addition, specific examples of this polymer electrolyte include polyanions such as sulfonate polyaniline, poly (thiophene-3-acetic acid), sulfonate polystyrene, poly (3-thiophene). Examples of polycations such as alkanesulfonates include polyallylamine, poly (p-phenylene-vinylene) precursor polymer, poly (p-methylpyridinium vinylene), protonated poly (p-pyridylvinylene), and polotone (2- N-methylpyridinium acetylene) and the like can be used. When an organic semiconductor layer doped with a low impurity concentration is used as the semiconductor layer, the organic semiconductor layer can have a heterojunction type or bulk heterojunction type structure. In the organic semiconductor layer having the heterojunction structure, the p-type organic semiconductor film and the n-type organic semiconductor film are joined so as to be in contact with the first electrode and the second electrode. The organic semiconductor layer having a bulk heterojunction structure is composed of a mixture of p-type organic semiconductor molecules and n-type organic semiconductor molecules, and has a fine structure in which the p-type organic semiconductor and the n-type organic semiconductor are intertwined with each other.

  As a semiconductor constituting the semiconductor layer, an organic-inorganic hybrid semiconductor can be used in addition to the inorganic semiconductor and the organic semiconductor. As such an organic-inorganic hybrid semiconductor, for example, a perovskite-based semiconductor (see, for example, Non-Patent Document 11) can be used.

  Preferably, the first electrode and the second electrode are in ohmic contact with the semiconductor layer. In the case where an organic semiconductor is used as the semiconductor layer, the first electrode and the second electrode may not be in ohmic contact with the semiconductor layer. As the first electrode and the second electrode, various transparent conductive oxides such as indium tin oxide (ITO) as well as metals such as gold (Au), nickel (Ni), and aluminum (Al) are used. Although it can be used, it is not limited to this.

  Preferably, the band gap of the semiconductor layer, or, if the semiconductor layer is made of an organic semiconductor, the HOMO (highest occupied molecular orbital) -LUMO (lowest unoccupied molecular orbital) gap is stepwise and / or sequentially in the light traveling direction. Or make it decrease continuously. By doing so, for example, when sunlight is incident on the main surface of the semiconductor layer of the photoelectric conversion device, when the sunlight is guided in the planar optical waveguide and incident on the semiconductor layer, the band gap or HOMO− The light enters the semiconductor with the largest LUMO gap first, and finally enters the semiconductor with the smallest band gap. In this process, the short wavelength light to the long wavelength light in the solar spectrum are spread. It is absorbed sequentially and this amount of absorption is maximized. For this reason, depending on how the band gap or HOMO-LUMO gap of the semiconductor layer is changed and the type of semiconductor used, the main part of the solar spectrum or substantially all light can be photoelectrically converted. Can bring the photoelectric conversion efficiency close to the theoretical maximum efficiency. Typically, the semiconductor layer includes a plurality of regions in which a band gap or a HOMO-LUMO gap is gradually reduced in the light traveling direction, and the first electrode and the second electrode are formed on a pair of surfaces facing each other. Two electrodes are provided, and at least one of the first electrode and the second electrode is provided separately between the regions.

  Preferably, the semiconductor layer includes a plurality of regions in which a band gap or a HOMO-LUMO gap is gradually reduced in the light traveling direction, and the width of each region in the light traveling direction is equal to the band gap or HOMO of each region. -More than the reciprocal of the absorption coefficient in each region of light having energy equal to the LUMO gap.

When the semiconductor layer is composed of a plurality of regions in which the band gap or the HOMO-LUMO gap is decreased stepwise in order in the light traveling direction, examples of these regions include Si _x C ₁ in order in the light traveling direction. _-x (0 <x <1) region consisting of a region consisting of a region made of Si and _{Si y Ge 1-y (0} <y <1) or a region consisting of Si _x C _1-x, made of Si A region composed of a region and a microcrystal Si _y Ge _{1 -y} , or a region containing at least one semiconductor selected from the group consisting of AlGaN, GaN and IGZO (In, Ga, Zn oxide), Si _x C _{1 -x} region, Si region and Si _y Ge _{1 -y} region, or Si _x C _{1 -x} region, Si region, Si _y Ge _{1 -y} region and Ge Territory It is an area.

  The photoelectric conversion device includes not only a solar battery but also an optical sensor. If necessary, a plurality of photoelectric conversion devices or solar cells may be combined to form a module or system.

In addition, this invention
Having at least one photoelectric conversion device;
The photoelectric conversion device is
A structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light;
A planar optical waveguide for guiding the two-dimensional spatial propagation light;
Having a semiconductor layer for photoelectric conversion provided at an end of the planar optical waveguide,
The light incident on the main surface of the planar optical waveguide is configured to be guided in the planar optical waveguide and incident on the semiconductor layer,
A net traveling direction of light guided in the planar optical waveguide, and a net moving direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from an end surface of the planar optical waveguide; The building is characterized in that the angle θ formed by is substantially a right angle.

  Here, the building may basically be any building as long as it can install a photoelectric conversion device. Specifically, for example, a building, a condominium, a detached house, There are apartments, station buildings, school buildings, government buildings, stadiums, stadiums, hospitals, churches, factories, warehouses, huts, and bridges. The installation location of the photoelectric conversion device in these buildings is not particularly limited, and is selected as necessary. Examples of installation locations are the glass windows and daylighting sections of these buildings. In this case, the photoelectric conversion device is, for example, a solar cell used as a power source for these buildings and electrical products installed therein. Preferably, the semiconductor layer is disposed in a shaded part of the building so that the light does not directly enter the semiconductor layer when the light enters the main surface of the planar optical waveguide. For example, the planar optical waveguide includes a portion having a gentle curvature, and this portion is disposed, for example, under a tile, under a protruding central portion of a roof, on a window frame or a crosspiece.

In addition, this invention
Having a photoelectric conversion device attached to the outer surface;
The photoelectric conversion device is
A structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light;
A planar optical waveguide for guiding the two-dimensional spatial propagation light;
Having a semiconductor layer for photoelectric conversion provided at an end of the planar optical waveguide,
The light incident on the main surface of the planar optical waveguide is configured to be guided in the planar optical waveguide and incident on the semiconductor layer,
A net traveling direction of light guided in the planar optical waveguide, and a net moving direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from an end surface of the planar optical waveguide; The electronic device is characterized in that the angle θ formed by is substantially a right angle.

  Electronic devices may be basically any type, including both portable and stationary types, but specific examples include mobile phones, mobile devices, robots, personal computers. , In-vehicle equipment, various home appliances. In this case, the photoelectric conversion device is, for example, a solar battery used as a power source for these electronic devices.

  According to the present invention, the net traveling direction of light guided in the planar optical waveguide and the net movement of carriers generated in the semiconductor layer by light incident on the semiconductor layer from the end surface of the planar optical waveguide. Since the angle θ formed with the direction is substantially a right angle, it is possible to achieve both the maximization of the amount of light absorption and the minimization of the distance between the electrodes by selecting the thickness of the photoelectric conversion layer in the light incident direction. For this reason, extremely high photoelectric conversion efficiency can be obtained. Further, since the incident light can be received by the entire main surface of the planar optical waveguide, there is no insensitive region for the incident light. In addition, since light incident on the main surface of the planar optical waveguide is guided through the planar optical waveguide and incident on the semiconductor layer, it is possible to prevent light from directly entering the semiconductor layer. For this reason, even when the semiconductor layer is made of, for example, amorphous silicon or an organic semiconductor, the deterioration of the organic semiconductor due to the Stebbler-Lonsky (SW) effect or an ultraviolet component can be suppressed. Further, it is very easy to increase the area of the photoelectric conversion device by increasing the area of the planar optical waveguide. In addition, when the band gap of the semiconductor layer or the semiconductor layer is made of an organic semiconductor, the HOMO-LUMO gap decreases stepwise and / or continuously in the light incident direction, so that the main part of the solar spectrum can be obtained. Alternatively, photoelectric conversion can be performed by absorbing light of all wavelengths, and ultimately, photoelectric conversion efficiency approaching the theoretical maximum efficiency can be obtained.

It is sectional drawing which shows the conventional solar cell. It is a basic diagram which shows the relationship between the distance between electrodes of a solar cell, and photoelectric conversion efficiency. It is a basic diagram which shows the relationship between photon energy and the photon density of sunlight. It is a basic diagram which shows the solar cell proposed by patent document 1. It is a top view which shows the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing which shows the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing which expands and shows the principal part of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing which shows the principal part of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing which shows an example of the semiconductor layer of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing which shows the principal part of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing which shows the example in which the light wave advancing direction change sheet | seat was provided on the planar optical waveguide in the photoelectric conversion apparatus by 1st Embodiment of this invention. It is a drawing substitute photograph which shows a mode that the advancing direction of a light wave is converted by the light wave advancing direction conversion sheet | seat shown in FIG. It is a drawing substitute photograph which shows a mode that the advancing direction of a light wave is converted by the light wave advancing direction conversion sheet | seat shown in FIG. It is a drawing substitute photograph which shows a mode that the advancing direction of a light wave is converted by the light wave advancing direction conversion sheet | seat shown in FIG. It is a basic diagram which shows the experimental result performed in order to show that the photoelectric conversion efficiency of the photoelectric conversion apparatus by 1st Embodiment of this invention is decided irrespective of the light absorption rate of a semiconductor layer. It is a basic diagram which shows another experimental result performed in order to show that the photoelectric conversion efficiency of the photoelectric conversion apparatus by 1st Embodiment of this invention is decided irrespective of the light absorption rate of a semiconductor layer. In the photoelectric conversion apparatus by 1st Embodiment of this invention, when a semiconductor layer consists of four types of semiconductors from which a band gap mutually differs, it is a basic diagram which shows the relationship between the photon energy and the photon density of sunlight. It is a basic diagram which shows the temperature dependence of the diffusion coefficient of various elements in a silicon | silicone. It is a basic diagram which shows the result of the Raman scattering measurement of the amorphous silicon layer crystallized by laser annealing. It is a drawing substitute photograph which shows the sample which formed the SiGe layer and the SiC layer by partially modifying the surface of the Si substrate. It is sectional drawing which shows the sample which modified the surface of Si substrate partially, and formed the SiGe layer and the SiC layer. It is a basic diagram which shows the result of having measured the current density-voltage characteristic of the SiGe element part of the sample shown to FIG. 17A and FIG. 17B. It is a basic diagram which shows the result of having measured the current density-voltage characteristic of the Si element part of the sample shown to FIG. 17A and FIG. 17B. It is a basic diagram which shows the result of having measured the current-voltage characteristic of the SiC element part of the sample shown to FIG. 17A and FIG. 17B. It is a top view for demonstrating an example of the growth method of the semiconductor layer of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing for demonstrating an example of the growth method of the semiconductor layer of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is sectional drawing for demonstrating the other example of the growth method of the semiconductor layer of the photoelectric conversion apparatus by 1st Embodiment of this invention. It is a basic diagram which shows the model of the simulation performed in order to verify the optical waveguide performance of the planar optical waveguide of the photoelectric conversion apparatus by 2nd Embodiment of this invention. It is a basic diagram which shows the result of the simulation performed in order to verify the optical waveguide performance of the planar optical waveguide of the photoelectric conversion apparatus by 2nd Embodiment of this invention. It is an equivalent circuit diagram which shows the composite photoelectric conversion apparatus by 4th Embodiment of this invention.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described with reference to the drawings. In the following embodiments, in principle, the same or corresponding parts are denoted by the same reference numerals.

<First Embodiment>
[Photoelectric conversion device]
5A and 5B show the photoelectric conversion device according to the first embodiment. As shown in FIGS. 5A and 5B, this photoelectric conversion device includes a rectangular or square planar optical waveguide 20 and a photoelectric conversion provided on end faces corresponding to a pair of parallel sides of the planar optical waveguide 20. And a semiconductor layer 30 for use. The semiconductor layer 30 generally has an elongated rectangular shape. The planar optical waveguide 20 and the semiconductor layer 30 are provided integrally with each other and have a planar shape as a whole. The planar optical waveguide 20 and the semiconductor layer 30 are provided on the support substrate 40.

  A first electrode 50 and a second electrode 60 are provided on a pair of opposing surfaces (upper surface and lower surface) of the semiconductor layer 30, respectively. One of the first electrode 50 and the second electrode 60 is used as an anode electrode, and the other as a cathode electrode. For example, the first electrode 50 is used as an anode electrode, and the second electrode 60 is used as a cathode electrode. When the semiconductor layer 30 is divided into a plurality of regions made of different semiconductors, the first electrode 50 and the second electrode 60 may be provided for each region, or one of them may be on all the regions. It may be a full-surface electrode extending to the surface.

The refractive index of the material constituting the planar optical waveguide 20 is n ₁ . In this case, stripe-shaped (band-shaped) buried layers 70 made of a material having a refractive index of n ₂ (n ₂ > n ₁ ) are provided in a predetermined arrangement on the light incident surface 20 a that is the main surface of the planar optical waveguide 20. Yes. With regard to the arrangement of the buried layers 70, considering that the strict periodicity has rather a delta function-like wavelength discrimination, it has a periodicity globally, but is locally random or systematic. It is effective to provide a quasi-periodic refractive index modulation structure that has fluctuations or deviates from strict periodicity. That is, as shown in FIGS. 5A and 5B, in this case, the stripe-shaped buried layer 70 and the stripe-like planar light between the buried layers 70 are within a certain range in the plane of the planar optical waveguide 20. The waveguides 20 are arranged alternately at regular intervals P at regular intervals or at regular intervals, whereby the three-dimensional spatially propagated light incident on the light incident surface 20a of the planar optical waveguide 20 is converted into the two-dimensional spatially propagated light. A structure 80 to be converted into is formed. However, in FIG. 5A and FIG. 5B, the buried layer 70 is shown on the entire surface of the planar optical waveguide 20 for convenience. The buried layer 70 extends parallel to the side of the planar optical waveguide 20 where the semiconductor layer 30 is provided. Assuming that the depth of the buried layer 70 is D, the light having the wavelength λ that is perpendicularly incident on the light incident surface 20 a of the planar optical waveguide 20 has a planar shape on both sides of the light that has passed through the buried layer 70 and the buried layer 70. A phase difference represented by 2π (n ₂ −n ₁ ) D / λ is obtained when the light passes through the structure 80 between the light passing through the optical waveguide 20. By setting D so that this phase difference is π or an odd multiple thereof, the amplitude of the light traveling in the vertical direction when passing through the structure 80 can be made zero. Preferably, an antireflection film (nonreflective coating) is further applied to the upper surface of the structure 80. By doing so, incident light must be propagated in the lateral direction (in-plane direction of the planar optical waveguide 20). Thus, the three-dimensional spatially propagated light becomes two-dimensional spatially propagated light and is efficiently guided in the planar optical waveguide 20. As a material for the buried layer 70, for example, SiN is preferable as a material having a refractive index of ˜2 and transparent in the ultraviolet (UV) to infrared (IR) region, but is not limited thereto.

The period P (or the constant interval W) is preferably three-dimensional over the entire wavelength band of photons corresponding to the energy of 3 eV to 0.5 eV with respect to the wavelength of the photons constituting the solar spectrum. Setting is made so that the spatially propagated light is converted into two-dimensional spatially propagated light. Most simply, P _i = λ _i (λ _i is a wavelength selected from the wavelength band of photons constituting the solar spectrum, i = 1 to N), a multiple (N-fold) periodic structure, and a plurality of intervals Set the structure. Multiplicity here means that there is a periodic structure of a plurality of layers in the thickness direction of the planar optical waveguide 20 (this periodicity is along the extending direction of the planar optical waveguide 20). By doing so, it is possible to convert the three-dimensional spatially propagated light into the two-dimensional spatially propagated light with respect to the entire sunlight spectrum. Preferably, the multiplicity N is made equal to the number of later-described E _gi regions constituting the semiconductor layer 30, in other words, the number of band gaps set stepwise in the light traveling direction in the semiconductor layer 30. The multiplicity of the periodic structure or the plurality of the structure interval may be set in the plane of the structure 80, or may be set in the depth direction. This corresponds to the configuration of the bandpass multilayer structure in the lateral direction.

  In this photoelectric conversion device, the three-dimensional spatially propagated light (incident light) incident on the light incident surface 20 a of the planar optical waveguide 20 is converted into two-dimensional spatially propagated light and guided through the planar optical waveguide 20. The light is collected and then incident on the semiconductor layer 30. As shown in FIG. 6, in this case, the net traveling direction of the light guided in the planar optical waveguide 20 and the light incident on the semiconductor layer 30 from the end surface of the planar optical waveguide 20 The angle θ formed by the net movement direction of the carriers (photocarriers) generated in (the direction connecting the first electrode 50 and the second electrode 60 in the shortest) is substantially a right angle. Specifically, the angle θ is divided into a plurality of regions in which the width of the light travel direction of the first electrode 50 or the semiconductor layer 30 is made of different semiconductors, and the first electrode 50 is provided for each region. If the width of the first electrode 50 provided in each region in the light traveling direction is W ′ and the thickness of the semiconductor layer 30 is d, then π / 2−δ ≦ θ ≦ π / 2 + δ (provided that Δ˜d / W ′), typically 80 ° ≦ θ ≦ 100 °, and most preferably 90 °. In order to prevent reflection of incident light as necessary, the light incident surface 20a of the planar optical waveguide 20 in FIG. A membrane is provided. A conventionally known antireflection film can be used. For example, a periodic multilayer structure composed of a plurality of materials having different refractive indexes can be given. In addition to this, it is also effective to arrange a fine structure (nanostructure / microstructure) generated by pyramid or etching on the surface. In particular, the fine structure provided on the surface of the planar optical waveguide 20, that is, the buried layer 70, has a functional structure having a distance x along the optical waveguide direction and has a diffractive action, so that FIGS. The direction shown in FIG. 2 is a redirection waveguide (that is, a redirection waveguide) (that is, incident light that is three-dimensional spatially propagated light is converted into two-dimensional spatially propagated light by, for example, diffraction, A functional thin film structure that can be guided in the lateral direction immediately). These low reflectance structures are selected as needed. Further, an antireflection film is preferably provided on the joint surface between the planar optical waveguide 20 and the semiconductor layer 30 in order to prevent reflection of light incident on the semiconductor layer 30 from the planar optical waveguide 20.

  A light reflection mechanism is provided on the end surface of the planar optical waveguide 20 corresponding to a pair of sides different from the pair of sides on which the semiconductor layer 30 is provided. In this light reflecting mechanism, for example, the light reflecting film provided on the end surface of the planar optical waveguide 20 or the end surface of the planar optical waveguide 20 is configured as a mirror surface. In this case, light incident on the main surface of the planar optical waveguide 20 is reflected when entering the light reflecting mechanism when guided in the planar optical waveguide 20, and the optical path is bent in the direction toward the semiconductor layer 30. As a result, the amount of light incident on the semiconductor layer 30 increases.

  This photoelectric conversion device is configured such that light does not directly enter the semiconductor layer 30 when light enters the light incident surface 20 a of the planar optical waveguide 20. In other words, when light is incident on the photoelectric conversion device, the light is incident on the light incident surface 20 a of the planar optical waveguide 20, but the light is not directly incident on the surface of the semiconductor layer 30. For this purpose, for example, the following is performed. For example, a light shielding layer is provided above the semiconductor layer 30 so as to cover the first electrode 50. A conventionally well-known thing can be used for a light shielding layer, and it selects as needed, For example, it is the aluminum laminated film etc. in which the plastic film was formed on both surfaces of the aluminum foil. This light shielding layer can prevent light from directly entering the semiconductor layer 30. In addition, when the support substrate 40 constitutes a part of the outer surface of a building or an electronic device, sunlight is incident on the planar optical waveguide 20, but sunlight is not incident on the semiconductor layer 30. In other words, the semiconductor layer 30 is covered with a member or the like so as to be shaded. For example, when this photoelectric conversion device is installed in a window of a building, the window glass serves as the support substrate 40, the planar optical waveguide 20 is provided on the window glass exposed to the outside, and the semiconductor layer 30 is made of, for example, aluminum. Hide inside the window frame. Further, when this photoelectric conversion device is spread on the roof of a building, the end portions of adjacent photoelectric conversion devices overlap each other, and the lower photoelectric conversion device is formed by the semiconductor layer 30 at the end portion of the upper photoelectric conversion device. The semiconductor layer 30 is covered at the end. When the photoelectric conversion device is installed in a display unit of an electronic device, for example, a smartphone, the transparent member on the surface of the display unit becomes the support substrate 40, and the planar optical waveguide 20 is formed on the transparent member exposed to the outside. The semiconductor layer 30 is provided so as to be hidden inside a member provided on the surface of the display unit.

  The planar optical waveguide 20 is made of transparent glass or transparent plastic. Examples of the transparent plastic include polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride, acetyl cellulose, brominated phenoxy, aramids, polyimides, polystyrenes, polyarylates, Examples include polysulfones and polyolefins. As the material of the planar optical waveguide 20, a fluorine-based material used for a plastic optical fiber (POF) or the like is particularly suitable because of its low light loss. The thickness of the planar optical waveguide 20 is selected as necessary, and is, for example, 1 to 1000 μm. The size (length and width) of the planar optical waveguide 20 is appropriately selected according to the location where the photoelectric conversion device is installed. In general, for example, (1 cm to 1 m) × (1 cm to 1 m). is there.

  The semiconductor layer 30 is selected as necessary from among those already mentioned. The semiconductor layer 30 is typically a pn junction composed of a p-type semiconductor layer and an n-type semiconductor layer. Preferably, a portion of the semiconductor layer 30 in contact with the first electrode 50 and the second electrode 60 is doped with a high impurity concentration, and the first electrode 50 and the second electrode 60 are doped with the semiconductor layer 30. And make ohmic contact. The length of one side of the semiconductor layer 30 is typically selected to be the same as the length of the side of the planar optical waveguide 20 on which the semiconductor layer 30 is provided, but the length of the side perpendicular to this side is generally For example, the thickness is 10 μm to 1 cm, and typically 20 μm to 1 mm. Since the size of the planar optical waveguide 20 is, for example, (1 cm to 1 m) × (1 cm to 1 m) as described above, the area of the semiconductor layer 30 is generally much larger than the area of the planar optical waveguide 20. It's small. That is, in this photoelectric conversion device, the planar optical waveguide 20 occupies most and the semiconductor layer 30 occupies only a small part at the end. For example, when the size of the planar optical waveguide 20 is 10 cm × 10 cm and the size of the semiconductor layer 30 is 1 mm × 10 cm, the two semiconductor layers occupy the entire area of the planar optical waveguide 20 and the two semiconductor layers 30. The ratio of the area of 30 is only 2 × 0.1 × 10 / 10.2 × 10.2 = 0.199≈2%. In addition, since the thickness of the semiconductor layer 30 is generally as small as several tens of μm or less, the volume of the semiconductor layer 30 is extremely small. That is, the amount of semiconductor layer 30 used can be extremely small. For this reason, the manufacturing cost of the photoelectric conversion device can be reduced. Further, the end portion of the planar optical waveguide 20 is bent (bended), for example, by 90 degrees downward with a finite radius of curvature, so that the light propagates in the semiconductor layer 30 in the vertical direction in FIG. 5B. be able to. Thereby, as described above, it is possible to minimize the light shielding loss that occurs when the light shielding layer is provided above the semiconductor layer 30 so as to cover the first electrode 50.

The band gap or HOMO-LUMO gap E _g of the semiconductor layer 30 is decreased stepwise in N stages (N ≧ 2) in the light traveling direction in the semiconductor layer 30, and in order E _g1 , E _g2,. E _gN (E _g1 > E _g2 >...> E _gN ). FIG. 7 shows an example where N = 4, but the present invention is not limited to this. As shown in FIG. 7, the semiconductor layer 30 includes regions 31, 32, 33, and 34 having band gaps or HOMO-LUMO gaps E _g of E _g1 , E _g2 , E _g3 , and E _g4 , respectively. Each of the regions 31, 32, 33, and 34 has an elongated stripe shape extending in a direction parallel to the side where the semiconductor layer 30 of the planar optical waveguide 20 is provided. In FIG. 7, first electrodes 51, 52, 53, and 54 are provided on the respective regions 31, 32, 33, and 34 so as to be separated from each other. The second electrode 60 is a full-surface electrode and is a common electrode for each of the regions 31, 32, 33, and 34. (The width in the traveling direction of light, the length of the lateral direction in FIG. 7) the width of each E _gi region constituting the semiconductor layer 30, the photoelectric conversion target photons (bandgap E of the E _gi region of the E _gi region _If the absorption coefficient of this E _gi region with respect to the one having the lowest energy among the photons having the energy of _gi or higher) is α _i , it is 1 / α _i or higher.

E _gi can be set as follows. For example, the wavelength is divided into N sections in the entire wavelength range of the AM1.5 sunlight spectrum or its main wavelength range (including a portion with a high incident energy). These sections are numbered in order from the short wavelength side (high energy side) 1, 2,..., N, and E _gi is selected to be equal to the minimum photon energy in the i-th section. In this way, when a photon having photon energy in the kth section is incident on the E _gi region, an electron-hole pair is generated and photoelectric conversion is performed. In this case, the photon having the photon energy in the k-th section reaches each _Egi region and is sufficiently absorbed, so that the _{Egi is introduced} from the junction surface between the planar optical waveguide 20 and the semiconductor layer 30. Choose the distance to the area. As a result, sunlight that is guided through the planar optical waveguide 20 and incident on the semiconductor layer 30 first enters the E _g1 region, and in the spectrum, the photon energy of E _g1 or higher is absorbed and photoelectric conversion is performed. Then, it enters the E _g2 region and the spectrum whose photon energy is greater than or equal to E _{g2 and} smaller than E _g1 is absorbed and photoelectrically converted, and finally enters the E _gN region and enters the photon of the spectrum. Those whose energy is greater than or _equal to E _{gN and} less than E _gN-1 are absorbed and photoelectrically converted. As a result, light in almost the entire solar spectrum or in the main wavelength range can be used for photoelectric conversion.

An ideal setting example of E _gi will be described. FIG. 3 shows the relationship between the photon energy hν of the AM1.5 sunlight spectrum and the number of photons n (hν). Here, it is assumed that the photon energy of the AM1.5 sunlight spectrum is equally divided into 10 sections of energy width Δ. In this case, the theoretical maximum photoelectric conversion efficiency is about 70%, which is more than double the theoretical maximum photoelectric conversion efficiency of 31% of a conventional solar cell with E _g = 1.35 eV, for example.

However, the photon number n (hν) is
It is represented by The photoelectric conversion efficiency η is
It is represented by

Each E _gi can be set by changing the composition of the semiconductor constituting each E _gi region, the form of the semiconductor (amorphous, polycrystalline, single crystal), or the like. Specifically, each E _gi region is formed of a different type of semiconductor. In this case, the semiconductor has a wide range of choices because it can be selected to have a high carrier mobility μ regardless of the absorption coefficient α. Some specific examples of using an inorganic semiconductor are as follows. In the case of N = 3, for example, the E _g1 region is Si _x C _1-x (E _g = 1.8 to 2.9 eV), the E _g2 region is Si (E _g = 1.11 eV), and the E _g3 region Is made of Ge (E _g = 0.76 eV). When N = 4, for example, the E _g1 region is Si _x C _1-x (E _g = 1.8 to 2.9 eV), and the E _g2 region is amorphous silicon (a-Si) (E _g = 1.4 to 1.8 eV), the E _g3 region is composed of Si _y Ge _1-y (E _g = 1.11 eV), and the E _g4 region is composed of Si _y Ge _1-y (E _g = ˜0.76 eV). . Alternatively, when N = 4, the E _g1 region is IGZO (In, Ga, Zn oxide) (E _g = ˜3 eV), and the E _g2 region is Si _x C _1-x (E _g = ˜1.8 eV). ), The E _g3 region is composed of Si (E _g = 1.11 eV), and the E _g4 region is composed of Si _y Ge _1-y (E _g = ˜0.76 eV). In addition, it can also be configured as follows. In the simplest case of N = 2, for example, the E _g1 region is a-Si (E _g = 1.4 to 1.8 eV), and the E _g2 region is Si _y Ge _1-y (E _g = ˜0. 76 eV). When N = 3, for example, the E _g1 region is GaP (E _g = 2.25 eV), the E _g2 region is GaAs (E _g = 1.43 eV), and the E _g3 region is InN (E _g = 0). .7 eV). When N = 4, for example, the E _g1 region is Ga _x In _1-x N (E _g = 2.3 eV), and the E _g2 region is Ga _y In _1-y N (E _g = 1.4). ~1.8eV), E _g3 area _{Ga z In 1-z N (} E g = 1.1eV), is composed of InN (E _g = 0.7eV) the E _g4 region. In the case of N = 5, for example, the CdSe fine particles (absorption peak wavelength 445 nm) having a diameter of about 1.9 nm in the E _g1 region, the CdSe fine particles (absorption peak wavelength 585 nm) having a diameter of about 4.0 nm in the E _g2 region, The _Eg3 region has a PbSe fine particle (absorption peak wavelength 800 nm) with a diameter of about 2 nm, the _Eg4 region has a PbSe fine particle with a diameter of about 4.5 nm (absorption peak wavelength 1100 nm), and the _Eg5 region has a PbSe fine particle with a diameter of about 90 nm (absorption peak wavelength). 2300 nm). Furthermore, it is also possible to configure the E _gi region in the case of N to 10 only by controlling x using GaInN _x As _1-x or GaInN _x P _1-x . In addition, the E _gi region may be formed using II-VI group compound semiconductors that are known to exhibit large bowing when Te is included. Specific examples of the case where an organic semiconductor and an inorganic semiconductor are used are as follows. For example, when N = 4, the E _g1 region is MDMO-PPV (E _g = 2.2 eV), the E _g2 region is a-Si (E _g = 1.4 to 1.8 eV), and the E _g3 region is The polyacene-based (hexacene) semiconductor (E _g = 1 to 1.2 eV) and the E _g4 region are composed of a polyacene-based (heptacene) semiconductor (E _g = 0.6 to 0.8 eV). Further, in the case of N ≧ 2, the E _g1 region is formed from IGZO (In, Ga, Zn oxide) (E _g = ˜3 eV), AlInN (E _g = 2.8 to 3 eV), or GaInN (E _g = 2.8 to 3 eV), or any one of oxide semiconductors (ZnO, ZnMgO, etc.) having a similar band gap, and a subsequent region, for example, an E _g2 region is defined as a-Si (E _g = 1). .4 to 1.8 eV), photons that cause the Stebler-Lonsky reaction, which has been shown to be generated by light having a wavelength of 450 nm or less, are photoelectrically converted in advance before entering the a-Si layer. Therefore, the reaction can be suppressed, and therefore the lifetime of the photoelectric conversion region formed of the a-Si layer can be extended. This high-energy photon removal function that suppresses coherent energy while effectively performing photoelectric conversion is not just passivation, but also improves the reliability and longevity of organic semiconductor photoelectric conversion units, which are also considered to be weak for outdoor use. Is also effective.

The thickness d of each E _gi region is selected as necessary, and is, for example, several μm to several tens of μm. The width of each E _gi region (the width in the light traveling direction in the semiconductor layer 30) is also selected as necessary, and is, for example, several tens of μm to several hundreds of μm. For example, FIG. 8 is an enlarged view of the regions 31 to 34 in FIG. 7. The thickness d of each region 31 to 34 is several μm to several tens of μm, and the widths w _{1 to} w ₄ of each region 31 to 34 are several. Select from 10 μm to several hundred μm, for example, to 100 μm.

  As shown in FIG. 9, in a typical case, each of the regions 31 to 34 is constituted by a pn junction including a p-type semiconductor layer and an n-type semiconductor layer. In FIG. 9, the junction surface of the pn junction which comprises each area | region 31-34 is shown with a broken line.

  By the way, when the three-dimensional spatial propagation light incident on the light incident surface 20a of the planar optical waveguide 20 is sunlight, the incident angle changes with time due to the rotation of the earth. In this case, as shown in FIG. 10, a light wave traveling direction conversion sheet 85 (for example, non-patent document) is formed on the structure 80 of the planar optical waveguide 20 that converts the three-dimensional space propagation light into the two-dimensional space propagation light. It is desirable to provide 4). When the antireflection film (non-reflective coating) is applied to the planar optical waveguide 20, it is formed on the light wave traveling direction changing sheet 85, and the effective refraction due to the nanostructure that the light wave traveling direction changing sheet 85 itself has on its surface. Asymptotic change in the rate (while entering the interior of the light wave traveling direction changing sheet 85 from free space), or geometric optical effects such as refraction and reflection caused by the microstructure of the light wave traveling direction changing sheet 85 itself on its surface However, it is possible to reduce the reflectance. Instead of the light wave traveling direction conversion sheet 85, for example, a pyramid structure, or an aggregate having a triangular cross section, which has translational symmetry in the direction perpendicular to the cross section (the vertical direction in FIG. 5A). It is also possible to use. FIG. 11A, FIG. 11B, and FIG. 11C are photographs of the light orientation characteristics with respect to the incident light of the light wave traveling direction changing sheet 85, and the light emitted to the back plane through the air by irradiating the light wave traveling direction changing sheet 85 Was taken in a photo. From FIG. 11A, FIG. 11B, and FIG. 11C, it can be seen that even when the irradiation angle of the laser beam is inclined in the horizontal direction, the emitted light is emitted at a right angle to the surface. Therefore, by using this light wave traveling direction conversion sheet 85, sunlight from an arbitrary direction can be changed from sunrise to sunset (although it is most preferable to change the elevation angle depending on the season so that the surface faces the ecliptic). Regardless of the time, it can be brought to the normal incidence arrangement of FIG. 9, and therefore the above-described three-dimensional spatially propagated light can be efficiently converted into two-dimensional spatially propagated light as described above. Furthermore, by using this light wave traveling direction changing sheet 85, all diffused light such as cloudy sky and wall reflected light can be brought to the light incident arrangement of FIG. Thereby, the difficulty of a lens-type condensing system can be solved, and the photoelectric conversion efficiency improvement with respect to diffused light can be implement | achieved. The light wave traveling direction changing sheet 85 can be a parabolic aggregate or a prismatic aggregate.

  The support substrate 40 may be basically any type, but is typically a transparent substrate that is at least transparent to visible light. Specifically, the transparent substrate is, for example, a glass plate or a transparent plastic plate. Examples of the transparent plastic constituting the transparent plastic plate include polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polystyrene, polyethylene, polypropylene, polyphenylene sulfide, polyvinylidene fluoride, acetyl cellulose, brominated phenoxy, aramids, polyimides, and polystyrene. , Polyarylates, polysulfones, polyolefins and the like can be used. Specifically, the support substrate 40 is, for example, a window glass of various buildings (public facilities, building diggs, condominiums, detached houses, etc.), various electronic devices (mobile phones, smartphones, notebook personal computers, desktop personal computers, TV, liquid crystal display, organic EL display) and the like, but not limited thereto.

[Operation of photoelectric conversion device]
The operation of this photoelectric conversion device will be described. The semiconductor layer 30 is a pn junction. As shown in FIGS. 5A and 5B, three-dimensional spatial propagation light, for example, the sun, is formed on the light incident surface 20a of the planar optical waveguide 20 of the photoelectric conversion device on which the structure 80 that converts to two-dimensional spatial propagation light is formed. Light enters. Light does not directly enter the surface of the semiconductor layer 30. The three-dimensional spatial propagation light incident on the light incident surface 20a of the planar optical waveguide 20 is converted into two-dimensional spatial propagation light by the structure 80 that converts the three-dimensional spatial propagation light into the two-dimensional spatial propagation light. The two-dimensional spatially propagated light is efficiently guided through the planar optical waveguide 20 while being repeatedly reflected on its upper and lower surfaces (see FIG. 24 described later), and exits from the end surface of the planar optical waveguide 20. After entering the semiconductor layer 30, it proceeds through the semiconductor layer 30, and electron-hole pairs are generated in the semiconductor layer 30 in the process. The electrons and holes thus generated move in the semiconductor layer 30 by drift or diffusion, and are collected by one and the other of the first electrode 50 and the second electrode 60. In this way, photoelectric conversion is performed in the semiconductor layer 30, and current (photocurrent) is extracted from the first electrode 50 and the second electrode 60 to the outside.

In this photoelectric conversion device, θ is almost a right angle as described above. Therefore, unlike the conventional solar cell shown in FIG. 1, the number of absorbed photons and the photocarrier collection efficiency are not in a trade-off relationship. Most preferably, θ = 90 °. In other words, light that is guided through the planar optical waveguide 20 and emitted from the end surface of the planar optical waveguide 20 from the direction perpendicular to the straight line that connects the first electrode 50 and the second electrode 60 in the shortest direction. The light can enter the semiconductor layer 30. In this case, the absorption photon number of the semiconductor layer 30 is governed by the width of the light incident direction (width w ₁ to w ₄ regions 31-34 when the semiconductor layer 30 is formed of, for example, regions 31-34), photoelectric The conversion efficiency η is not controlled by the thickness d of the semiconductor layer 30 in the light absorption rate limiting region (thick dashed line in FIG. 2). That is, the photoelectric conversion device is extremely advantageous in that it optimizes light absorption and carrier collection efficiency by making the incident direction of light with respect to the planar optical waveguide 20 and the moving direction of carriers orthogonal to each other, for example. Is completely compatible with each other. Furthermore, the small absorption coefficient α of the semiconductor layer 30 is the width of the semiconductor layer 30 in the light incident direction (in the case where the semiconductor layer 30 is composed of, for example, the regions 31 to 34, the widths w _{1 to} w _{4 of the} regions 31 to 34). ) Can be compensated for, so that the material of the semiconductor layer 30 can be a material having a large μ that is the only dominant parameter, regardless of the size of α. By doing so, it is possible to obtain a high photoelectric conversion efficiency η as shown by a thick dashed line in FIG. Thereby, it is possible to obtain the photoelectric conversion efficiency approaching the thermodynamic limit.

12 and 13 show the results of experiments conducted to verify that the photoelectric conversion efficiency η is released from the constraint due to α in this photoelectric conversion device. 12, an IZO (indium zinc oxide) film, a PEDOT: PSS film, and a P3HT: PCBM film are sequentially formed on a PEN (polyethylene naphthalate) film, and the P3HT: PCBM film is formed. An Al film was formed. The thickness of the P3HT: PCBM film is d. The result of measuring the voltage-current characteristics by applying a voltage between the IZO film and the Al film is shown in the lower inset of FIG. The black rhombus plot in FIG. 12 is η when light is incident on the P3HT: PCBM film from the vertical direction, and the white ellipse plot is η measurement results when light is incident from the end face of the P3HT: PCBM film. Indicates. The dotted straight line in FIG. 12 indicates η∝d. FIG. 13 shows the results of another lot (sample). The dependence of I _SC V _OC (I _SC is the saturation current, V _OC is the open circuit voltage) on the thickness d of the P3HT: PCBM film is shown as P3HT: PCBM. The measurement result about the case where light is incident on the film from the vertical direction and the case where light is incident from the end face of the P3HT: PCBM film is shown. 12 and 13, when light is incident on the P3HT: PCBM film from the vertical direction, η increases as d increases, whereas light is incident from the end face of the P3HT: PCBM film. In this case, the photoelectric conversion efficiency shows the opposite tendency that η increases as d decreases. Further, when the thickness of the P3HT: PCBM film is the same (for example, 150 nm), the light is incident from the end face of the P3HT: PCBM film as compared with the case where the light is incident on the P3HT: PCBM film from the vertical direction. It can be seen that η is larger in the case. This means that η is not bound to the absorption coefficient α of the P3HT: PCBM film, more generally the semiconductor layer.

Next, an optimum setting example of E _g1 , E _g2 , E _g3 , and E _g4 when the semiconductor layer 30 includes four regions 31 to 34 as shown in FIG. 7 will be described. FIG. 14 shows the relationship between the photon energy hν of the AM1.5 sunlight spectrum and the number of photons n _ph . In FIG. 14, E _g1 , E _g2 , E _g3 , and E _g4 are described as E _g (1), E _g (2), E _g (3), and E _g (4). As shown in FIG. 14, the photon energy of the AM1.5 sunlight spectrum is divided into four sections. The theoretical maximum photoelectric conversion efficiency in this case is about 50% as shown in the inset of FIG. 14, which is about 1 of the theoretical maximum photoelectric conversion efficiency of 31% of a conventional solar cell with E _g = 1.35 eV, for example. .6 times.

  Further, this photoelectric conversion device is a condensing system, and this condensing effect further improves the photoelectric conversion efficiency as shown in the inset of FIG. 3, and 60% can be achieved when N = 4. At N = 10, as can be seen from the inset of FIG. 3, a photoelectric conversion efficiency of 75% is also possible. In particular, N can be increased by using a gradient composition structure in which the composition of the semiconductor layer 30 can be easily realized by using the gradient parameter arrangement described later, and the composition of the semiconductor layer 30 is inclined in the direction of light traveling in the semiconductor layer 30. In addition, at least one of the electrodes 50 and 60 is allowed to be formed in batch with respect to N regions (segments) (that is, a tandem structure connected in parallel). Taking advantage of this photoelectric conversion device, it is possible to realize an ideal condensing system that can be as thin as 85% of the thermodynamic limit.

Consider a case where a Si layer is used as the semiconductor layer 30 and an element other than Si is introduced into the Si layer to partially modify the Si layer and convert it to another semiconductor. FIG. 15 shows the temperature dependence of the diffusion coefficients of various elements in Si. From FIG. 15, for example, Si _x C _1-x can be produced by diffusing C in the Si layer, and Si _y Ge _1-y can be produced by diffusing Ge.

  FIG. 16 shows the result of Raman scattering measurement of a sample obtained by using an a-Si layer doped with phosphorus (P) as the semiconductor layer 30 and crystallizing the a-Si layer by laser annealing. Laser annealing was performed using laser light having a wavelength of 514 nm obtained using an argon (Ar) laser. The irradiation energy density was 6.1 mW and the irradiation time was 10 minutes. The number of times of laser light irradiation was changed to 1, 2, 3, and 4. From this result, it can be seen that the a-Si layer can be selectively converted into crystalline Si only at the portion irradiated with light. Since a-Si and crystalline Si have different band gaps, it can be seen that two regions having different band gaps can be formed. In addition, the stripe width can be controlled by the irradiation width of the laser beam.

  FIG. 17A shows a sample in which Ge is partially diffused on the surface of the Si substrate to form a striped SiGe region, and C is diffused to another portion of the surface of the Si substrate to form a striped SiC region. It is the photograph which image | photographed the surface of this with the optical microscope. FIG. 17B shows the cross-sectional shape of this sample.

18 to 20 show measurement results of current density (J) -voltage (V) characteristics of the SiGe element portion, J-V characteristics of the Si element portion, and IV characteristics of the SiC element portion of this sample, respectively. 18 to 20, it can be seen that the SiGe element, the Si element, and the SiC element have different built-in voltages, and the open-circuit voltages V _oc are 0.22 to 0.24 V, .about.0.42 V,. Since it is 45-0.6V, it turns out that the band gap of a pn junction surface can be changed by the composition control by diffusion of elements other than Si to a Si substrate. This is evidence that photons in different energy ranges of the sunlight spectrum can be photoelectrically converted.

Here, a preferred example of a specific method for growing the semiconductor layer 30 will be described. Here, as an example, the case where the semiconductor layer 30 is composed of three types of semiconductors having a gradient composition in the light traveling direction in the semiconductor layer 30 and the band gap decreasing in the light traveling direction will be described. This growth method is not limited to this, and can generally be applied to the case of N kinds of semiconductors. In addition, here, these three types of semiconductors are A _p B _1-p C, A _q B _1-q C, and A _r B _1-r C (p>q> r or p The case where <q <r) will be described. However, the present invention is not limited to this, and in general, a binary or quaternary or higher semiconductor may be used. By setting C = {φ} (empty set), these three types of semiconductors become binary materials (for example, Si _x Ge _1-x ).

As shown in FIGS. 21A and 21B, an A _p B _1-p C layer 102, an A _q B _1-q C layer 103, and an A _r B _1-r C layer 104 are grown in this order on the substrate 101 in the x-axis direction. Let The A _p B _1-p C layer 102, the A _q B _1-q C layer 103, and the A _r B _1-r C layer 104 have an elongated stripe shape extending in the y-axis direction. As shown in FIG. 21A, the growth of these A _p B _1-p C layer 102, A _q B _1-q C layer 103, and A _r B _1-r C layer 104 occurs on the substrate 101 in the x-axis direction. Although it can be performed by supplying a raw material flux, an inclination parameter arrangement is performed at this time. That is, the parameter value monotonously changes (increases or decreases) along the x-axis direction of FIGS. 21A and 21B. Here, the monotonicity (changing to monotonus) is important. That is, for example, in the growth material A _x B _1-x C (x = p, q, r), p>q> r (or p <q <r), and the composition of A along the x-axis direction Is monotonically decreasing (or monotonically increasing). The parameters include the growth temperature, the lattice constant of the substrate 101, the number of off-angles of the substrate 101, and the light intensity at the time of light irradiation when using light during growth. It is also effective to combine a plurality of these. Examples of a method for changing the lattice constant of the substrate 101 include ion implantation and diffusion. As an atomic species used for ion implantation or diffusion, use of a constituent element of the substrate 101 or a constituent element of a target growth layer has high affinity, but is not limited thereto. The light irradiation is selected according to the purpose, such as a case where the crystal growth reaction itself is promoted or a case where the substrate temperature rises. Examples of the raw material flux include a raw material-containing gas, a molecular beam, and a raw material-containing solution. By moving the substrate 101 at a constant speed in the y-axis direction of FIG. 21A, a multi-stripe semiconductor layer can be grown on a virtually infinitely long tape-like substrate. Since doping can be performed simultaneously with growth, a pn junction can also be formed, the semiconductor layer 30 can be easily formed, and a photoelectric conversion device can be easily manufactured. Note that when the substrate 101 is left as it is after the growth of the semiconductor layer 30, a conductive substrate is used as the substrate 101, and when only the semiconductor layer 30 is peeled off after the growth of the semiconductor layer 30, the substrate 101 is used. Either a conductive substrate or a non-conductive substrate may be used.

  Another preferred example of a specific method for growing the semiconductor layer 30 will be described. As shown in FIG. 22, one side in the left-right direction from the direction inclined by a certain angle with respect to the main surface of the substrate 101 while moving the substrate 101 toward the back side (the y-axis direction in FIG. 21A). For example, the raw material flux supply device 105 supplies the raw material flux 106 for supplying A and C, and the raw material flux supply device 107 supplies the raw material flux 108 for supplying B and C, for example, from the other side in the left-right direction. The raw material fluxes 106 and 108 are, for example, a raw material gas, a molecular beam, mist spray (for example, see Non-Patent Documents 12 to 13), and the like. Also by this method, it is possible to grow the semiconductor layer 30 made of three kinds of semiconductors having a gradient composition in the light traveling direction in the semiconductor layer 30 and having a band gap decreasing in the light traveling direction. When growing a quaternary or higher multi-element semiconductor, a necessary number of raw material flux supply devices are prepared. Further, the combined use of the growth method shown in FIGS. 21A and 21B and the growth method shown in FIG. 22 is also effective.

According to the first embodiment, the following various advantages can be obtained. That is, in this photoelectric conversion device, the planar optical waveguide 20 occupies most of the area, and the entire planar optical waveguide 20 can receive incident light. Absent. Further, in this photoelectric conversion device, the light incident on the light incident surface 20a of the planar optical waveguide 20 and guided by being condensed in the planar optical waveguide 20 is incident on the semiconductor layer 30. As shown in the inset of FIG. 3, extremely high photoelectric conversion efficiency can be obtained. For example, when the size of the planar optical waveguide 20 is 10 cm × 10 cm, the thickness d of the semiconductor layer 30 is 50 μm = 50 × 10 ⁻⁴ cm, and the width of the semiconductor layer 30 is 10 cm, the light collection rate is (planar optical waveguide). The area of the waveguide 20 / (the area of the end face on which light of the semiconductor layer 30 is incident) = (10 × 10) / 2 × (10 cm × 50 × 10 ⁻⁴ ) = 1000 times. The photoelectric conversion efficiency at this time exceeds 60% from the inset of FIG. Further, in the conventional solar cell, since it is necessary to provide a semiconductor for photoelectric conversion on the entire light incident surface, a large amount of semiconductor is used, whereas in this photoelectric conversion device, only a part of the semiconductor layer 30 is provided. Therefore, the volume of the semiconductor can be very small, so that the amount of semiconductor used can be reduced and the manufacturing cost can be reduced. When the semiconductor layer 30 includes a plurality of regions in which the band gap or the HOMO-LUMO gap gradually decreases in the light traveling direction in the semiconductor layer 30, a high energy ultraviolet component of sunlight. Can be absorbed in the region of the first stage, for example, so that the ultraviolet component can be prevented from entering the region of the subsequent stage. For this reason, even if the latter region is made of amorphous silicon or an organic semiconductor, there is no problem of the Stebbler-Lonsky effect or the deterioration of the organic semiconductor. For this reason, it is possible to improve the photoelectric conversion efficiency and improve the reliability of the photoelectric conversion device. Furthermore, this photoelectric conversion device can be easily increased in area simply by increasing the area of the planar optical waveguide 20. Further, the semiconductor layer 30 is provided at the end portion of the planar optical waveguide 20, and the light guided in the planar optical waveguide 20 exits from the end surface of the planar optical waveguide 20 and enters the semiconductor layer 30. Therefore, a lens for condensing light is not necessary, the configuration is extremely simple, and optical axis alignment is not necessary, so that not only manufacturing is easy, but also manufacturing cost is reduced. It is also possible to prevent changes over time and changes over time. In addition, the point that the photoelectric conversion efficiency decreases with respect to the diffused light, which was a drawback of the lens-type condensing system, is extremely compatible with the light wave traveling direction changing sheet 85 in the sense that they are mutually planar and can be bonded together. By adopting the structure of the planar optical waveguide 20, even diffused light can be recovered to about 95% (which is the efficiency of the light wave traveling direction changing sheet 85) compared to the photoelectric conversion efficiency for direct light. . In addition, in this photoelectric conversion device, the space charge effect that is a problem in the amorphous silicon solar cell can be suppressed. That is, the amorphous silicon solar cell has a problem that even if the thickness of the amorphous silicon is increased to increase the light absorption, the internal electric field is canceled by the space charge and the characteristics are not improved. On the other hand, in this photoelectric conversion device, when a partial region of the semiconductor layer 30 is composed of amorphous silicon, the region between the first electrode 50 and the second electrode 60 provided above and below the semiconductor layer 30 is used. The distance can be reduced, and at the same time, the length of the amorphous silicon region in the light traveling direction in the semiconductor layer 30 can be increased, so that the space charge effect can be suppressed.

Further, in this photoelectric conversion device, the surface that can convert the three-dimensional spatially propagated light into the two-dimensional spatially propagated light and efficiently propagate the two-dimensional spatially propagated light, that is, the light receiving surface (planar optical waveguide 20). ) And the semiconductor layer 30 which is a photoelectric conversion region can be spatially separated, so that an increase in the temperature of the semiconductor layer 30 due to direct sunlight can be suppressed. For example, the planar optical waveguide 30 includes a portion having a gentle curvature, and the other portion is disposed under the tile, under the protruding central portion of the roof, under the window rail, etc. When light is incident on the light incident surface 20a, the semiconductor layer 30 can be disposed in a shaded portion. Thereby, both the temperature rise by direct light and the bad influence with respect to the coupling | bonding of the semiconductor layer 30 by the ultraviolet (UV) light component in direct light can be suppressed. In particular, by setting the band gap E _{g1 of the} first layer on which sunlight is incident to be equal to or greater than the coherent energy of the semiconductor material used, it is possible to protect the bonding of the subsequent semiconductors, extend the device life, and obtain long-term reliability. It is done. Regarding the temperature rise, the high efficiency of this photoelectric conversion device means that the loss as heat can be minimized, so the energy is highly efficient for the guided light. By reducing the component that is converted into electric energy and converted into heat, the temperature rise can be suppressed.

  As described above, according to this photoelectric conversion device, on the basis of the suppression of the temperature rise (through the reduction of energy lost as heat) due to the high efficiency, further, the bad place of the condensing system (due to the incidence of high intensity light) Temperature rise) can be eliminated, and only a good point (a point where the conversion efficiency increases by about 20% as shown in the inset in FIG. 3 as compared with the non-condensing system) can be utilized.

The advantages of this photoelectric conversion device can be summarized as follows.
(1) The optical absorption and carrier collection efficiency can be independently and simultaneously optimized by the orthogonality between the photon traveling direction and the photocarrier moving direction.
(2) Multi-stage multi-striping with a gradient composition is possible, and full-width photoelectric conversion of the sunlight spectrum is possible.
(3) Due to the light condensing system, an efficiency increase of about 20% is expected compared to the non-light condensing system.
(4) Since it is possible to perform photoelectric conversion using multi-stage multi-gap semiconductors, energy dissipated as heat can be minimized, so that temperature rise, which was a weak point of a concentrated solar power generation system, can be suppressed. .
(5) Since it is a condensing system using a planar optical waveguide using a diffraction grating, deterioration of condensing characteristics with respect to diffused light during cloudy weather is suppressed.
(6) High energy photons that harm the bonding of materials are photoelectrically converted in the first layer of the multi-strip (without wasting energy) to form the subsequent intermediate gap semiconductor layer and narrow gap semiconductor layer It is possible to prevent deterioration of the substances to be obtained, and as a result, high reliability can be obtained. In particular, if a material that could not be used outdoors is used in the photoelectric conversion device, it can be used outdoors with high reliability.

  As described above, this photoelectric conversion device can be said to be an ultimate photoelectric conversion system having many characteristics.

<Second Embodiment>
[Photoelectric conversion device]
In the first embodiment, three-dimensional spatial propagation light incident on the light incident surface 20 a of the planar optical waveguide 20 is provided by providing the buried layer 70 on the light incident surface 20 a that is the main surface of the planar optical waveguide 20. In the second embodiment, a periodic concavo-convex structure is provided on the light incident surface 20a by stamping or nano-microimprinting. Thus, the structure 80 that converts the three-dimensional space propagation light into the two-dimensional space propagation light is formed. The periodic concavo-convex structure has, for example, a comb tooth shape, a sawtooth shape, a sinusoidal shape, or the like. Others are the same as in the first embodiment.

In this photoelectric conversion device, a simulation was performed to verify the optical waveguide performance of the planar optical waveguide 20 in which the structure 80 that converts the three-dimensional spatially propagated light into the two-dimensional spatially propagated light is formed on the light incident surface 20a. . The model used for the simulation is shown in FIG. As shown in FIG. 23, convex portions 112 a having a rectangular cross section are periodically formed in a part of one main surface (light incident surface) of the planar optical waveguide 111 to form a periodic concavo-convex structure 112. Has been. The planar optical waveguide 111 corresponds to the planar optical waveguide 20, and the periodic uneven structure 92 corresponds to the structure 80 that converts the three-dimensional spatial propagation light into the two-dimensional spatial propagation light. On the other main surface of the planar optical waveguide 111, a back metal 113 made of Al that functions as a reflection film is formed over a larger area than the periodic uneven structure 112. The interface between the back metal 113 and the planar optical waveguide 111 is formed in a sawtooth shape, and light hitting a minute inclined surface of the back metal 113 on the sawtooth interface is reflected in various directions. ing. The simulation conditions are as follows. The refractive index of the planar optical waveguide 111 was n = 1.65 (assuming resin, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), etc. as the material of the planar optical waveguide 111). The (x, y, z) coordinate system was taken as shown in FIG. The width of the planar optical waveguide 111 in the x-axis direction was 80 μm, and the thickness in the z-axis direction was 4 μm. The direction in which the convex portions 112 a are arranged is the x-axis direction, the direction orthogonal to the x-axis direction in the plane of the planar optical waveguide 111 is the y-axis direction, and the direction perpendicular to the plane of the planar optical waveguide 111 is the z-axis direction. It is. The number of protrusions 112a is 5, the pitch of protrusions 112a in the x-axis direction is 2.0 μm, the width of protrusions 112a in the x-axis direction is 1.0 μm, and the groove between the protrusions 112a and 112a The width is 1.0 μm, the height in the z-axis direction of the projection 112a is 1.5384 μm, and the width in the y-axis direction of the projection 112a is 3.9 μm. Light having a wavelength of 2.1 μm (plane wave) was incident on the periodic uneven structure 112 in the z-axis direction. Under these conditions, the y component E _y of the electric field in the planar optical waveguide 111 was calculated using the Maxwell equation. The distribution of the amplitude of _Ey thus calculated is shown in the upper diagram of FIG. As can be seen from this result, most of the light incident perpendicularly to the periodic concavo-convex structure 112 is diffracted by the periodic concavo-convex structure 112 and the traveling direction thereof is changed by 90 °, and the light travels in the planar optical waveguide 111. Waveguide. In other words, the redirection wave guide was shown to be feasible, and the structural parameters were also clarified. It is possible to cope with light of other wavelengths by appropriately changing the size and period of the convex portion 112a (or the embedded layer 70). The lower part of FIG. 24 shows the result of the same calculation performed by setting the height of the projection 112a in the z-axis direction to 1.0 μm. In this case, since the diffraction condition is not satisfied, the diffraction hardly occurs, and the light incident perpendicularly to the periodic concavo-convex structure 112 hardly guides the planar optical waveguide 111. From the above results, it was verified that the optical waveguide performance of the planar optical waveguide 20 in which the periodic concavo-convex structure of the photoelectric conversion device is provided on the light incident surface 20a is high. In addition, the above result is similarly established when the structure 80 for converting the three-dimensional spatial propagation light into the two-dimensional spatial propagation light is formed by providing the embedded layer 70 as in the first embodiment. .
According to the second embodiment, advantages similar to those of the first embodiment can be obtained.

<Third Embodiment>
[Photoelectric conversion device]
In the third embodiment, in the photoelectric conversion device according to the first embodiment, a minute uneven structure (a jagged structure) is provided on the side surface of the semiconductor layer 30 in contact with the end face of the planar optical waveguide 20. Others are the same as in the first embodiment.

By providing such a minute uneven structure on the side surface of the semiconductor layer 30, a low reflectance can be provided regardless of the wavelength of incident light (see, for example, Non-Patent Document 14). In Non-Patent Document 14, a p-type polycrystalline silicon wafer doped with boron is immersed in an aqueous solution containing 15 wt% H ₂ O ₂ and 25 wt% HF at room temperature, and is applied to the surface of the p-type polycrystalline silicon wafer. A fine concavo-convex structure is formed by contacting the platinum mesh attached to the roller and etching the surface of the p-type polycrystalline silicon wafer from the opening of the platinum mesh while rotating the roller. As described above, when a minute uneven structure is formed by etching the side surface of the semiconductor layer 30, an etching solution and an etching method to be used are appropriately determined according to the type of semiconductor exposed on the side surface of the semiconductor layer 30. According to Non-Patent Document 14, the reflectance of the p-type polycrystalline silicon wafer can be suppressed to 1 to 3% in the wavelength range of 300 nm to 800 nm. Further, as can be seen from FIGS. 1B and 2A of Non-Patent Document 14, since the structure has no periodicity in the range from 0 to 10 μm, the same is true in the wavelength range from 800 nm to 2.4 μm. Low reflectance can be obtained. When such a minute uneven structure is used for a conventional planar solar cell, the solar cell may be used outdoors, and if dust or the like accumulates on the surface, the effect tends to be reduced. In the photoelectric conversion device, since this minute uneven structure is formed on the side surface of the semiconductor layer 30, it is not only horizontally oriented, but also directly coupled to the end surface of the planar optical waveguide 20, so that dust can be contained in the unevenness. Since there is no room for such deposition, high characteristics can be constantly maintained and long-term stability is achieved.

  As described above, according to the third embodiment, in addition to the same advantages as those of the first embodiment, it is possible to obtain the advantage that the long-term stability of the photoelectric conversion device can be realized. .

<Fourth embodiment>
[Composite photoelectric conversion device]
In the fourth embodiment, a composite photoelectric conversion device in which two photoelectric conversion devices according to the first embodiment are combined will be described.

As shown in the left diagram of FIG. 25, in the photoelectric conversion device according to the fourth embodiment, the semiconductor layer 30 includes two semiconductor layers 30 having four band gaps, that is, photoelectric conversion devices 121 and 122. Prepare. These photoelectric conversion devices 121 and 122 have, for example, the configuration shown in FIG. E _g (1), E _g (2), E _g (3), and E _g (4) correspond to the E _g1 region, the E _g2 region, the E _g3 region, and the E _g4 region. As shown in the diagram on the right side of FIG. 25, these photoelectric conversion devices 121 and 122 are connected to each other. That is, the first electrode 51, the first electrode 52, the first electrode 53, and the first electrode 54 of the photoelectric conversion device 121 are respectively connected to the first electrode 54, the first electrode 53, and the photoelectric conversion device 122. Connected to the first electrode 52 and the first electrode 51.

  According to the fourth embodiment, the same advantages as those of the first embodiment can be obtained, and a composite photoelectric conversion device having a high photoelectric conversion efficiency η can be realized while maintaining a single output voltage. be able to.

  Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, at the end of the above-mentioned planar optical waveguide 20, a layer having a small refractive index has been formed from the back side by changing the refractive index of the glass waveguide, for example, by ion exchange, and has been guided two-dimensionally. As light approaches the semiconductor layer 30, the light is condensed also in the direction perpendicular to the surface, and gathers to the same thickness as the semiconductor layer 30 at the contact portion between the planar optical waveguide 20 and the semiconductor layer 30 ( Asymptotically concentrate the light).

  Further, for example, the UV light component in the sunlight spectrum does not have a high ratio as can be seen from FIG. 3, so that it is not converted into two-dimensional spatially propagated light from the beginning, and therefore is guided in the planar optical waveguide 20. Instead, only the light having a lower energy component than this is converted into two-dimensional spatially propagated light, guided in the planar optical waveguide 20 and incident on the semiconductor layer 30 to be photoelectrically converted. When a-Si or an organic semiconductor is included, the lifetime of the photoelectric conversion device can be improved and the reliability can be improved.

  Further, for example, by segmenting the semiconductor layers 30 at both ends of FIG. 5A at predetermined lengths (for example, about 10 cm) in the vertical direction (y-axis direction) in the drawing, the connection as shown in FIG. 25 is achieved. The probability / risk of the malfunction of the photoelectric conversion device due to the defect generated in the element unit of the tandem structure that occurs when the operation is performed can be reduced. This is because in the conventional series-connected tandem structure, the larger the area, the higher the probability of the above-mentioned problem, whereas in the photoelectric conversion device according to the present invention, the element unit of the tandem structure is in a line shape and the area is small. In addition to being extremely small, this element unit is segmented in the stripe direction as described above, and as described above, the probability that a local defect will cause the entire photoelectric conversion device to be defective is markedly increased. Can be lowered.

  For example, the numerical values, materials, shapes, arrangements, and the like given in the above-described embodiments are merely examples, and different numerical values, materials, shapes, arrangements, and the like may be used as necessary.

  Further, a plurality of photoelectric conversion devices according to the first to fourth embodiments may be spread to constitute a photoelectric conversion device system (or a solar cell system).

  Further, with the above-mentioned redirection wave guide, for example, the entire side surface of the building is wrapped around in a headband shape, and the photoelectric conversion element part (semiconductor layer 30) coupled thereto is, for example, one place on the north side surface of the building (that is, For example, they may be arranged in a concentrated manner in an area of several meters in the vertical direction and several mm to 1 cm in the lateral direction. In addition, this headband-shaped redirection wave guide itself is provided with a reverse redirection structure (that is, returning a two-dimensional spatially propagated light to a three-dimensional spatially propagated light) in a part of the shaded portion of the building. Therefore, it can also be used for applications that substantially eliminate the shade formed by the building.

  In some cases, in the present invention, a structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light can be omitted. That is, it has a planar optical waveguide that guides two-dimensional spatially propagated light, and a photoelectric conversion semiconductor layer provided at an end of the planar optical waveguide, and is incident on the main surface of the planar optical waveguide. Light is guided in the planar optical waveguide and incident on the semiconductor layer, and the net traveling direction of the light guided in the planar optical waveguide and the planar optical waveguide A photoelectric conversion device is also effective in that the angle θ formed with the net movement direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from the end face is substantially a right angle. In this case, the three-dimensional spatial propagation light is incident on the main surface of the planar optical waveguide, the light enters the planar optical waveguide, and the two-dimensional spatial propagation light is guided through the planar optical waveguide. The

DESCRIPTION OF SYMBOLS 20 Planar optical waveguide 20a Light incident surface 30 Semiconductor layer 40 Support substrate 50-54 1st electrode 60 2nd electrode 70 Embedded layer 80 Structure 85 which converts 3D space propagation light into 2D space propagation light 85 Light wave progress Direction change sheet

Claims (14)

A structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light;
A planar optical waveguide for guiding the two-dimensional spatial propagation light;
A photoelectric conversion semiconductor layer integrally provided at the end of the planar optical waveguide,
The light incident on the main surface of the planar optical waveguide is configured to be guided in the planar optical waveguide and incident on the semiconductor layer,
A net traveling direction of light guided in the planar optical waveguide, and a net moving direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from an end surface of the planar optical waveguide; The angle θ formed by
The semiconductor layer is, on a single substrate, Ga _p1 In _1-p1 N layer in order in the traveling direction of light, Ga _p2 In _1-p2 N layer, grown ... and Ga _pN In _1-pN N layer, These Ga _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer,... And Ga _pN In _1-pN N layer have an elongated stripe shape extending in a direction perpendicular to the light traveling direction. The growth of these Ga _p1 In _{1 -p1} N layer, Ga _p2 In _{1 -p2} N layer,... And Ga _pN In _{1 -pN} N layer is carried out according to the growth temperature, the lattice constant of the substrate, and the off-angle of the substrate. The band gap is gradually increased step by step in the light traveling direction by monotonically decreasing the Ga composition in the light traveling direction by changing the number or a combination of these in a monotonous manner in the light traveling direction. It consists of N reduced areas (N ≧ 2),
The structure that converts the three-dimensional spatially propagated light into the two-dimensional spatially propagated light has a period P _i = λ _i (λ _i constitutes the sunlight spectrum) provided in the thickness direction of the planar optical waveguide. A periodic structure of a plurality of layers having a wavelength, i = 1 to N) selected so as to convert the three-dimensional spatially propagated light into the two-dimensional spatially propagated light from the photon wavelength band to the entire wavelength band of sunlight. A photoelectric conversion device comprising: A micro uneven structure having no periodicity is provided on a side surface of the semiconductor layer in contact with an end surface of the planar optical waveguide to reduce the reflectance of light incident on the side surface. Item 2. The photoelectric conversion device according to Item 1. A first electrode and a second electrode on the first surface of the semiconductor layer opposite to each other and on the second surface opposite to the side on which the three-dimensional spatially propagated light is incident, respectively. Two electrodes are provided, and the first electrode is provided so as to be separated from each other among the N (N ≧ 2) regions, and is provided above the semiconductor layer so as to cover the first electrode. 3. The photoelectric conversion device according to claim 1, wherein the three-dimensional spatial propagation light is not directly incident on the semiconductor layer by providing a light shielding layer. 4. Reflected over the area larger than the periodic structure of the multiple layers of the structure for converting the three-dimensional spatially propagated light into the two-dimensional spatially propagated light on the other principal surface opposite to the principal surface of the planar optical waveguide A back metal functioning as a film is provided, and the interface between the back metal and the planar optical waveguide is formed in a sawtooth shape, and various types of light hitting the minute inclined surface of the back metal at the sawtooth interface. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device is reflected in a direction. Having at least one photoelectric conversion device;
The photoelectric conversion device is
A structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light;
A planar optical waveguide for guiding the two-dimensional spatial propagation light;
A photoelectric conversion semiconductor layer integrally provided at the end of the planar optical waveguide,
The light incident on the main surface of the planar optical waveguide is configured to be guided in the planar optical waveguide and incident on the semiconductor layer,
A net traveling direction of light guided in the planar optical waveguide, and a net moving direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from an end surface of the planar optical waveguide; The angle θ formed by
The semiconductor layer is formed of Ga on the single substrate in the light traveling direction. _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer, ... and Ga _pN In _1-pN N layers are grown and these Ga _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer, ... and Ga _pN In _1-pN The N layer has an elongated stripe shape extending in a direction perpendicular to the light traveling direction. _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer, ... and Ga _pN In _1-pN The growth of the N layer is performed by changing the growth temperature, the lattice constant of the substrate, the off-angle number of the substrate, or a combination of these in a monotonous manner in the light traveling direction, thereby forming the composition of Ga in the light traveling direction. Is monotonously reduced, and the band gap is made up of N regions (N ≧ 2) in which the band gap gradually decreases in the light traveling direction,
The structure for converting the three-dimensional spatially propagated light into the two-dimensional spatially propagated light has a period P provided in the thickness direction of the planar optical waveguide. _i = Λ _i (Λ _i Is a wavelength selected to convert the three-dimensional spatially propagated light into the two-dimensional spatially propagated light from the wavelength band of the photons constituting the solar spectrum over the entire wavelength band of sunlight, i = 1 to N A building characterized by having a periodic structure of a plurality of layers. A micro uneven structure having no periodicity is provided on a side surface of the semiconductor layer in contact with an end surface of the planar optical waveguide to reduce the reflectance of light incident on the side surface. Item 5. The building according to item 5. A first electrode and a second electrode on the first surface of the semiconductor layer opposite to each other and on the second surface opposite to the side on which the three-dimensional spatially propagated light is incident, respectively. Two electrodes are provided, and the first electrode is provided so as to be separated from each other among the N (N ≧ 2) regions, and is provided above the semiconductor layer so as to cover the first electrode. The building according to claim 5 or 6, wherein a light shielding layer is provided so that the three-dimensional space propagation light does not directly enter the semiconductor layer. Reflected over the area larger than the periodic structure of the multiple layers of the structure for converting the three-dimensional spatially propagated light into the two-dimensional spatially propagated light on the other principal surface opposite to the principal surface of the planar optical waveguide A back metal functioning as a film is provided, and the interface between the back metal and the planar optical waveguide is formed in a sawtooth shape, and various types of light hitting the minute inclined surface of the back metal at the sawtooth interface. The building according to any one of claims 5 to 7, wherein the building is reflected in a direction. The planar optical waveguide has a square or rectangular shape, and the semiconductor layer having an elongated rectangular shape is provided on an end surface corresponding to a pair of parallel sides of the planar optical waveguide, and the window of the building The building according to claim 5, wherein the planar optical waveguide is provided on the window glass exposed to the outside using the window glass as a supporting substrate, and the semiconductor layer is hidden inside an aluminum window frame. Having at least one photoelectric conversion device attached to the outer surface;
The photoelectric conversion device is
A structure that converts three-dimensional spatially propagated light into two-dimensional spatially propagated light;
A planar optical waveguide for guiding the two-dimensional spatial propagation light;
A photoelectric conversion semiconductor layer integrally provided at the end of the planar optical waveguide,
The light incident on the main surface of the planar optical waveguide is configured to be guided in the planar optical waveguide and incident on the semiconductor layer,
A net traveling direction of light guided in the planar optical waveguide, and a net moving direction of carriers generated in the semiconductor layer by light incident on the semiconductor layer from an end surface of the planar optical waveguide; The angle θ formed by
The semiconductor layer is formed of Ga on the single substrate in the light traveling direction. _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer, ... and Ga _pN In _1-pN N layers are grown and these Ga _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer, ... and Ga _pN In _1-pN The N layer has an elongated stripe shape extending in a direction perpendicular to the light traveling direction. _p1 In _1-p1 N layer, Ga _p2 In _1-p2 N layer, ... and Ga _pN In _1-pN The growth of the N layer is performed by changing the growth temperature, the lattice constant of the substrate, the off-angle number of the substrate, or a combination of these in a monotonous manner in the light traveling direction, thereby forming the composition of Ga in the light traveling direction. Is monotonously reduced, and the band gap is made up of N regions (N ≧ 2) in which the band gap gradually decreases in the light traveling direction,
The structure for converting the three-dimensional spatially propagated light into the two-dimensional spatially propagated light has a period P provided in the thickness direction of the planar optical waveguide. _i = Λ _i (Λ _i Is a wavelength selected to convert the three-dimensional spatially propagated light into the two-dimensional spatially propagated light from the wavelength band of the photons constituting the solar spectrum over the entire wavelength band of sunlight, i = 1 to N An electronic apparatus having a periodic structure of a plurality of layers. A micro uneven structure having no periodicity is provided on a side surface of the semiconductor layer in contact with an end surface of the planar optical waveguide to reduce the reflectance of light incident on the side surface. Item 11. The electronic device according to Item 10. A first electrode and a second electrode on the first surface of the semiconductor layer opposite to each other and on the second surface opposite to the side on which the three-dimensional spatially propagated light is incident, respectively. Two electrodes are provided, and the first electrode is provided so as to be separated from each other among the N (N ≧ 2) regions, and is provided above the semiconductor layer so as to cover the first electrode. 12. The electronic apparatus according to claim 10, wherein a light shielding layer is provided so that the three-dimensional space propagation light does not directly enter the semiconductor layer. Reflected over the area larger than the periodic structure of the multiple layers of the structure for converting the three-dimensional spatially propagated light into the two-dimensional spatially propagated light on the other principal surface opposite to the principal surface of the planar optical waveguide A back metal functioning as a film is provided, and the interface between the back metal and the planar optical waveguide is formed in a sawtooth shape, and various types of light hitting the minute inclined surface of the back metal at the sawtooth interface. The electronic device according to claim 10, wherein the electronic device is reflected in a direction. The planar optical waveguide has a square or rectangular shape, and the semiconductor layer having an elongated rectangular shape is provided on an end surface corresponding to a pair of parallel sides of the planar optical waveguide, The transparent optical member is used as a support substrate, the planar optical waveguide is provided on the transparent member exposed to the outside, and the semiconductor layer is hidden inside a member provided on the surface of the display unit. Electronics.