JP2008300512A - Photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photoelectric conversion device which can improve photoelectric conversion efficiency by collectively inserting a large number of crystal semiconductor particles easily into an opening of a light reflecting member with a minimized gap. <P>SOLUTION: The photoelectric conversion device comprises a conductive substrate 1, spherical bodies 2 of a large number of spherical crystal semiconductor particles of first conduction types which have semiconductor layers 3 of second conduction types formed thereon and are spaced by distances from one another on the conductive substrate 1, an insulating layer 4 formed between the conductive substrate 1 and the crystal semiconductor particle bodies 2, a light-transmitting conductive layer 5 formed on the insulating layer 4 and on the crystal semiconductor particle bodies 2, and light reflecting resin-made members 7 which are formed on the light-transmitting conductive layer 5 on the insulating layer 4 and which have light reflecting surfaces 8 of recessed shapes for condensing light at the crystal semiconductor particle body 2 and also an opening 17 of a polygonal shape for exposing the upper part of the crystal semiconductor particle body 2 at the lower end of the light reflecting surface 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion device used as a solar cell or the like, and more particularly to a photoelectric conversion device using crystalline semiconductor particles such as crystalline silicon particles.

  Conventional concentrating photoelectric conversion devices, particularly those used as solar cells, cut a crystalline semiconductor plate such as a crystalline silicon plate to produce small-area photoelectric conversion elements, and these photoelectric conversion elements at intervals And a configuration in which a condenser lens is provided on each photoelectric conversion element has been proposed (see, for example, Patent Document 1).

  Moreover, as a conventional photoelectric conversion device using crystalline semiconductor particles, an opening is formed in a first aluminum foil, and a silicon sphere having an n-type outer shell on a p-type central core is inserted into the opening. After removing the n-type outer shell on the back side of the sphere, forming an insulating layer on the surface of the silicon sphere from which the first aluminum foil and n-type outer shell have been removed, and removing the insulating layer on the back side top of the silicon sphere, A silicon sphere and a second aluminum foil that have been joined via a metal joint has been proposed (see, for example, Patent Document 2).

  This photoelectric conversion device has a spherical lens for condensing on a silicon sphere. When crystal semiconductor particles are used as in this photoelectric conversion device, gaps are generated between the crystal semiconductor particles, resulting in photoelectric conversion loss. Therefore, the light energy incident on the gaps between the crystal semiconductor particles is converted into crystals adjacent to the gaps. In order to input to the semiconductor particle side, a spherical lens is formed on the crystalline semiconductor particle parallel to the curved surface.

As another conventional photoelectric conversion device, a configuration in which light is reflected by a substrate formed on a concave mirror and condensed on a silicon sphere is known.
JP-A-8-330619 US Pat. No. 5,417,782

  However, the photoelectric conversion device disclosed in Patent Document 1 cuts a crystalline semiconductor plate made of a crystalline silicon plate or the like to produce a small area photoelectric conversion element, and connects the photoelectric conversion elements with a connection tab or the like. Therefore, the number of manufacturing steps is increased, the manufacturing becomes complicated, and the cost cannot be sufficiently reduced.

  In addition, a photoelectric conversion device using a spherical lens formed in parallel with the curved surface of the surface of the crystalline semiconductor particle is designed to reduce the incident angle dependency of light on the photoelectric conversion efficiency using the spherical lens. Can be expanded only to about 1/10 of the diameter of the crystalline semiconductor particles. As a result, the amount of semiconductor used in the photoelectric conversion device is not reduced, which is disadvantageous for weight reduction and cost reduction.

  Further, the photoelectric conversion device configured to reflect light by a substrate formed so as to form a concave mirror and collect it on a silicon sphere deforms the substrate into the shape of a concave mirror, but in order to maintain the shape of the substrate Further holding structure is required. In addition, since the boundary portion between adjacent concave mirrors is flat and not formed at an acute angle, reflection of light at the flat boundary portion cannot be ignored, and there is a tendency for photoelectric conversion loss to occur. In addition, the concave mirror-shaped light reflecting surface is mainly made of metal such as silver, so it reacts with air sulfide gas, oxygen gas, etc. in the air and deteriorates (blackening in the case of silver), resulting in a decrease in light reflectivity. Therefore, it was insufficient to maintain stable photoelectric conversion performance over a long period of time.

  For example, in the case of a configuration in which a silicon sphere is inserted into an opening formed in an aluminum foil or a reflecting mirror, the shape of the opening is a circular shape corresponding to the silicon sphere, but the size of the silicon sphere varies. For this reason, it has been extremely difficult to smoothly insert a large number of silicon spheres into the openings. Therefore, some silicon spheres cannot be inserted into the opening or can be easily inserted into the opening, but a large gap is formed between the opening.

  Accordingly, the present invention has been completed in view of the above-described conventional problems, and the object thereof is to collect a large number of crystal semiconductor particles in the opening of the light reflecting member and easily collectively with a minimum gap. To obtain a photoelectric conversion device with improved photoelectric conversion efficiency.

  Moreover, even if the distance between the crystal semiconductor particles is greatly increased, the generation of scratches on the light reflecting surface is suppressed and the light reflecting member can maintain a sufficient photoelectric conversion efficiency for a long period of time. Light incident angle dependency of photoelectric conversion efficiency can be reduced, and a condensing structure can be formed without deforming the substrate. As a result, the amount of semiconductor used is reduced, and the weight is reduced and the cost is reduced. An object of the present invention is to provide a photoelectric conversion device that can sufficiently concentrate on crystalline semiconductor particles after achieving the above.

  The photoelectric conversion device of the present invention has a spherical first conductivity type in which a conductive substrate and a semiconductor portion of the second conductivity type are formed on the surface layer, and a large number of them are joined on the conductive substrate at intervals. A crystalline semiconductor particle; an insulating layer formed between the crystalline semiconductor particles on the conductive substrate; a translucent conductive layer formed on the insulating layer and on the crystalline semiconductor particle; and on the insulating layer A concave light reflecting surface formed on the translucent conductive layer and focused on the crystalline semiconductor particles; and a polygonal opening that exposes an upper portion of the crystalline semiconductor particles at a lower end of the light reflecting surface. And a light reflecting member made of resin.

  In the photoelectric conversion device of the present invention, preferably, the shape of the opening is a regular polygon.

  In the photoelectric conversion device of the present invention, preferably, the opening is circumscribed by a circle having the maximum diameter of the particle size distribution of the plurality of crystal semiconductor particles and inscribed in a circle having the minimum diameter.

  In the photoelectric conversion device of the present invention, preferably, a metal layer is formed on the light reflecting surface, and a transparent protective layer is formed on the metal layer.

  In the photoelectric conversion device of the present invention, preferably, the metal layer is made of aluminum and / or silver.

  In the photoelectric conversion device of the present invention, preferably, the metal layer and the translucent conductive layer are electrically insulated.

  In the photoelectric conversion device of the present invention, it is preferable that the light reflecting member has a sharp apex at the top in the longitudinal section.

  In the photoelectric conversion device of the present invention, preferably, the transparent protective layer has a convex curved surface at the top in the longitudinal section.

  The photoelectric conversion device of the present invention includes a conductive substrate and a spherical first conductivity type crystal in which a second conductivity type semiconductor portion is formed on the surface layer and a large number of them are joined on the conductive substrate at intervals. Semiconductor particles, an insulating layer formed between crystalline semiconductor particles on a conductive substrate, a translucent conductive layer formed on the insulating layer and the crystalline semiconductor particles, and a translucent conductive layer on the insulating layer A light reflecting member made of a resin having a concave light reflecting surface for condensing the crystal semiconductor particles and a polygonal opening that exposes an upper portion of the crystal semiconductor particles at the lower end of the light reflecting surface. Therefore, even if the size of the large number of crystal semiconductor particles varies, the large number of crystal semiconductor particles are interspersed in the polygonal openings formed in the flexible light reflecting member. Can be easily inserted in a batch with minimal .

  That is, the polygonal opening has a diameter corresponding to a circle having a diameter circumscribing the opening from a crystal semiconductor particle having a diameter corresponding to a circle inscribed in the opening (inscribed crystal semiconductor particle). The crystal semiconductor particles (circumscribed crystal semiconductor particles) having can be easily inserted. In addition, when the opening is circular, when a crystal semiconductor particle smaller than the opening is inserted, the gap is formed so as to surround the crystal semiconductor particle, and the gap becomes large, but the polygonal opening is Even when the inscribed crystal semiconductor particles are inserted, the gap is only partially formed around the crystal semiconductor particles. Moreover, when the circumscribed crystal semiconductor particles are inserted into the polygonal openings, almost no gap is formed around the crystal semiconductor particles.

  In addition, when the opening is circular, it may not be possible to insert a crystal semiconductor particle larger than the opening, but the polygonal opening is easily formed even with circumscribed crystal semiconductor particles. Can be inserted.

  Therefore, a large number of crystal semiconductor particles can be easily and collectively inserted into the polygonal opening with a minimum gap.

  In the photoelectric conversion device of the present invention, preferably, the shape of the opening is a regular polygon, so that it becomes easier to insert a large number of spherical crystal semiconductor particles into the openings at once.

  Further, in the photoelectric conversion device of the present invention, preferably, the opening is circumscribed to a circle having the maximum diameter of the particle size distribution of a large number of crystal semiconductor particles and inscribed in a circle having the minimum diameter. It becomes easier to insert a large number of spherical crystal semiconductor particles into the openings at the same time, and the gap between the crystal semiconductor particles and the openings can be minimized.

  In the photoelectric conversion device of the present invention, preferably, a metal layer is formed on the light reflecting surface, and a transparent protective layer is formed on the metal layer. The reflecting member can be easily molded and the cost can be reduced. In addition, when the metal layer is made of a metal such as silver or aluminum, it is prevented that the metal reacts with sulfide gas or oxygen gas in the air and deteriorates (blackening in the case of silver) to reduce the light reflectivity. be able to. Moreover, peeling of the metal layer can be prevented. Moreover, it can prevent that a metal layer and a translucent conductive layer conduct | electrically_connect with an electroconductive foreign material, and the current collection property of a translucent conductive layer falls.

  In the photoelectric conversion device of the present invention, preferably, the metal layer is made of aluminum and / or silver, so that a further sufficient reflectance can be obtained.

  In the photoelectric conversion device of the present invention, preferably, the metal layer and the light-transmitting conductive layer are electrically insulated, so that there is no extra electrical conduction from the light-transmitting conductive layer to the metal layer. Therefore, the current is collected sufficiently by the conductive electrode layer that plays the role of a current collecting electrode, and the current collecting effect is greatly improved.

  In the photoelectric conversion device of the present invention, preferably, the light reflecting member has an acute-angled pointed head in the longitudinal section, so that the incident light is reflected upward at the top of the light reflecting member. And incident light can be efficiently collected on the crystalline semiconductor particles.

  In the photoelectric conversion device of the present invention, preferably, the transparent protective layer has a convex curved surface at the top in the longitudinal section, and the metal layer reflects light by pressing the metal layer from the outside. The effect of forming an acute angle without being cut at the top of the member is obtained.

  Examples of the embodiment of the photoelectric conversion device of the present invention will be described in detail below with reference to the drawings. However, these are merely examples of the embodiment, and the photoelectric conversion device of the present invention is configured as shown in FIGS. It is not limited to.

  FIG. 1 is a cross-sectional view showing an example of an embodiment of the photoelectric conversion device of the present invention, FIG. 2 is a plan view showing an example of the embodiment of the photoelectric conversion device of the present invention, and FIG. It is sectional drawing which shows embodiment of the photoelectric conversion module formed using the photoelectric conversion apparatus of FIG. 4, (a)-(c) is a top view of embodiment of the opening part in the photoelectric conversion apparatus of this invention. is there.

  1-4, 1 is a conductive substrate, 2 is a crystalline semiconductor particle constituting a granular photoelectric converter, 3 is a semiconductor portion (semiconductor layer) constituting a granular photoelectric converter, 4 is an insulating layer, and 5 is a light-transmitting material. A conductive conductive layer, 6 is an alloy layer of aluminum and crystalline semiconductor particles, for example, forming the conductive substrate 1, 7 is a light reflecting member made of transparent resin, and 8 is a light reflecting surface of the surface of the light reflecting member 7. , 9 is a surface filling layer, 10 is a surface protection body, 11 is a back surface filling layer, 12 is a transparent protection layer, 13 is an electrode layer, 14 is a back surface protection layer, and 15 is a spacing member. The conductive substrate 1 itself may be made of aluminum, or a conductive layer made of aluminum or the like may be provided on an insulating substrate.

  The photoelectric conversion device of the present invention includes a conductive substrate 1 and a spherical first conductive material in which a second conductive type semiconductor portion 3 is formed on the surface layer and a large number of first conductive members are joined on the conductive substrate 1 at intervals. Type crystalline semiconductor particles 2, an insulating layer 4 formed between the crystalline semiconductor particles 2 on the conductive substrate 1, a translucent conductive layer 5 formed on the insulating layer 4 and on the crystalline semiconductor particles 2, A concave-shaped light reflecting surface 8 formed on the light-transmitting conductive layer 5 on the insulating layer 4 and condensed on the crystal semiconductor particles 2, and a multi-layer that exposes the upper part of the crystal semiconductor particles 2 at the lower end of the light reflecting surface 8. And a light reflecting member 7 made of a resin having a rectangular opening 17.

  With this configuration, even if there are variations in the size of the large number of crystal semiconductor particles 2, the large number of crystal semiconductor particles 2 are placed in the polygonal openings 17 formed in the flexible light reflecting member 7. It can be easily inserted in a batch with a minimum gap.

  Further, light incident between the crystalline semiconductor particles 2 can be efficiently guided to the crystalline semiconductor particles 2. Moreover, even if the distance between the crystal semiconductor particles 2 is increased to 1/10 or more of the diameter of the crystal semiconductor particles 2, the dependency of photoelectric conversion efficiency on the incident angle of light can be reduced. As a result, the amount of semiconductor used can be reduced, and a photoelectric conversion device that is reduced in weight and cost can be manufactured.

  Moreover, it becomes possible to reduce the clearance gap between the crystal semiconductor particle 2 and the opening part 17 of a light reflection member, and it becomes possible to obtain higher photoelectric conversion efficiency.

  Moreover, generation | occurrence | production of the damage | wound of the light reflection surface 8 of the light reflection member 7 at the time of manufacture of a photoelectric conversion apparatus is suppressed, Furthermore, the light reflection surface 8 can be protected over a long period of time after preparation, and sufficient photoelectric conversion efficiency Can be maintained for a long time. Further, when the light reflecting surface 8 is made of a metal such as silver or aluminum, the metal reacts with sulfide gas, oxygen gas, etc. in the air and deteriorates (blackening in the case of silver), thereby reducing the light reflectivity. Can be prevented. In addition, when the light reflecting surface 8 is formed by covering a metal layer, peeling of the metal layer can be prevented. In addition, when the light reflecting surface is made of a metal or a metal layer, the metal or metal layer and the light-transmitting conductive layer 5 are electrically connected to each other by the conductive foreign matter, and the current collecting property of the light-transmitting conductive layer 5 is reduced. Can be prevented.

  Below, each site | part which comprises the photoelectric conversion apparatus of this invention is demonstrated.

<Conductive substrate>
The conductive substrate 1 in the present invention may be composed of an aluminum substrate, a metal substrate having a melting point higher than that of aluminum, a ceramic substrate having a conductive layer formed on the surface, and the like, for example, aluminum, aluminum alloy, iron, stainless steel, etc. A substrate made of steel, nickel alloy, alumina ceramics or the like is used. When the conductive substrate 1 is made of a material other than aluminum, a conductive layer made of aluminum may be formed on the substrate made of a material other than aluminum.

<Crystal semiconductor particles>
The shape of the crystalline semiconductor particle 2 in the present invention is spherical. Since the crystalline semiconductor particles 2 are spherical, the crystalline semiconductor particles 2 have a convex curved surface, and the dependency of the incident light on the light beam angle can be reduced. As the spherical shape, a true spherical shape is particularly preferable. In this case, the dependency of the incident light on the ray angle can be made smaller, the bonding property of the crystalline semiconductor particles 2 to the conductive substrate 1 can be improved, and the bonding strength of each crystalline semiconductor particle 2 can be improved. Can be made uniform.

  Further, by making the surface of the crystal semiconductor particles 2 rough, the light reflectance on the surface of the crystal semiconductor particles 2 can be reduced, and the light absorbability of the crystal semiconductor particles 2 can be improved. In order to form this rough surface, the crystalline semiconductor particles 2 may be immersed in an alkaline solution and the surface of the crystalline semiconductor particles 2 may be etched, or the crystalline semiconductor particles 2 may be etched using an RIE (Reactive Ion Etching) apparatus or the like. The surface may be finely processed.

  The particle diameter of the crystalline semiconductor particles 2 is preferably 0.2 to 0.8 mm, and more preferably 0.2 to 0.6 mm in particular for reducing the amount of semiconductor (such as silicon) used. When the particle diameter is less than 0.2 mm, it is difficult to assemble the crystalline semiconductor particles 2 to the conductive substrate 1. Also, if the particle diameter exceeds 0.8 mm, the amount of semiconductor used, including the cutting portion, in the conventional crystalline semiconductor plate type photoelectric conversion device manufactured by cutting out from a crystalline semiconductor mother board (wafer) made of silicon or the like is changed. The merit of using the crystalline semiconductor particles 2 tends to disappear.

  In addition, the particle diameter of the crystalline semiconductor particles 2 is an average particle diameter, which is an average particle diameter before bonding to the conductive substrate 1, and the crystalline semiconductor particles 2 before the formation of the translucent conductive layer 5. The average particle diameter. This average particle diameter can be measured by a particle size distribution measuring device using laser light.

  The crystalline semiconductor particles 2 exhibit the first conductivity type (for example, p-type). In the case of the p-type, a dopant such as B, Al, and Ga is produced, and the crystalline semiconductor particles 2 are produced by a jet method (melting drop method) or the like. It is obtained, for example, by incorporating it into the raw material.

  The crystalline semiconductor particles 2 are made of a single crystal or a polycrystal of a semiconductor, but are particularly preferably single crystals since photocurrent can be taken out efficiently. In the case of polycrystal, recombination of electrons and vacancies occurs at the grain boundary, and as a result, the output of photocurrent decreases.

  The crystalline semiconductor particles 2 are formed into a granular shape by, for example, a melt drop method (jet method) or the like, and single crystallized by a method such as a remelt (remelting) method. Further, depending on the manufacturing conditions, it is possible to obtain crystal semiconductor particles 2 that are substantially single crystallized with few grain boundaries only by the jet method, and may be used as it is in a photoelectric conversion device.

  On the surface layer of the crystalline semiconductor particles 2, a second conductivity type (for example, n-type) semiconductor portion 3 is formed. The second conductivity type semiconductor portion 3 is formed by, for example, a thermal diffusion method, a vapor phase growth method, or the like.

  In the thermal diffusion method, for example, if a semiconductor compound 3 is n-type by inserting a crystalline semiconductor particle 2 into a high-temperature quartz tube for a certain period of time using a phosphorus compound such as phosphorus oxychloride as a diffusing agent, a crystalline semiconductor An n-type semiconductor portion 3 can be formed on the surface of the particle 2. As an example, by inserting the crystalline semiconductor particles 2 into a quartz tube at 900 ° C. for 30 minutes, an n-type semiconductor portion 3 having a thickness of 1 μm can be formed on the surface. However, in this case, as shown in FIG. 1, in order to electrically separate the semiconductor portion 3 and the alloy layer (eutectic layer) 6, the surface of the semiconductor portion 3 except for the vicinity of the alloy layer 6 is covered with an acid resistant resist or the like. It is necessary to remove the semiconductor portion 3 by coating with an etching solution and removing the semiconductor portion 3 of the uncovered portion with an etching solution.

  In the case of the thermal diffusion method, it can be performed before the bonding of the crystalline semiconductor particles 2 and the conductive substrate 1.

  Further, in the vapor phase growth method or the like, for example, the n-type semiconductor portion 3 can be formed by introducing a small amount of a vapor phase of a phosphorus compound serving as an n-type dopant into the gas phase of a silane compound.

  The film quality of the semiconductor part (semiconductor layer) 3 may be any of crystalline, amorphous, or a mixture of crystalline and amorphous, but considering the light transmittance, crystalline or crystalline and amorphous. It is good to mix quality.

The concentration of the trace element in the semiconductor part 3 is preferably, for example, 1 × 10 ¹⁶ to 1 × 10 ²¹ atoms / cm ³ . Furthermore, the semiconductor part 3 is preferably formed along a convex curved surface of the surface of the crystalline semiconductor particle 2. By being formed along the surface of the convex curved surface of the crystalline semiconductor particle 2, the area of the pn junction can be increased widely, and carriers generated inside the crystalline semiconductor particle 2 can be efficiently collected. .

<Insulating layer>
The insulating layer 4 formed on the conductive substrate 1 between the crystalline semiconductor particles 2 is made of an insulating material for separating the positive electrode and the negative electrode. That is, the insulating layer 4 is provided so that the translucent conductive layer 5 disposed on the upper surface side thereof does not contact the conductive substrate 1 on the lower surface side. As an insulating material forming the insulating layer 4, SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , CaO, MgO, P ₂ O ₅ , Li ₂ O, SnO, ZnO, BaO, TiO _{2 and the} like are optional components. Examples thereof include low-temperature firing glass (glass frit) materials made of materials, glass compositions containing fillers made of one or more of the above materials, and organic materials such as polyimide or silicone resin. The amount of the insulating material is not particularly limited, and the light-transmitting conductive layer 5 provided on the insulating layer 4 may be provided uniformly.

  The insulating layer 4 may further contain dispersed insulating particles made of an insulating material such as glass, ceramics, or resin. The average particle diameter of the insulator particles is preferably 4 to 20 μm. When the average particle diameter of the insulator particles is within the range, the insulator particles can be sufficiently dispersed in the insulating layer 4.

<Translucent conductive layer>
The translucent conductive layer 5 is coated on the crystalline semiconductor particles 2 and the insulating layer 4. Here, the translucent conductive layer 5 functions as the other electrode when the conductive substrate 1 is used as one electrode.

The translucent conductive layer 5 is made of one or a plurality of oxide-based films selected from SnO ₂ , In ₂ O ₃ , ITO, ZnO, TiO _2, etc., and is formed by sputtering, vapor phase epitaxy, or coating. It is formed by a firing method or the like. The translucent conductive layer 5 can be expected to have an effect as an antireflection film by selecting an appropriate film thickness.

  Since the translucent conductive layer 5 is transparent, a part of incident light is transmitted through the translucent conductive layer 5 in a portion where the crystalline semiconductor particles 2 are not present, and is reflected by the lower conductive substrate 1 to be crystal semiconductor particles 2. The light energy irradiated to the whole photoelectric conversion device can be efficiently guided to the crystal semiconductor particles 2 and irradiated.

  The translucent conductive layer 5 is preferably formed along the surface of the semiconductor portion 3 or the crystalline semiconductor particle 2 and is formed along the convex curved surface of the crystalline semiconductor particle 2. In this case, carriers generated inside the crystalline semiconductor particles 2 can be efficiently collected.

<Light reflecting member>
The light reflecting member 7 has a concave light reflecting surface 8 for condensing the crystal semiconductor particles 2. The light reflecting surface 8 preferably has a concave mirror structure composed of a partially curved surface such as a spherical surface or a spheroid surface in order to improve the light collecting property. In particular, it is preferable that the concave curved surface shape is a curved surface shape of an elliptic rotating body in order to reduce the incident angle dependency of light. According to the computer simulation, when the incident angle changes with time like the sun, the curved surface shape of the elliptical rotating body can collect light more efficiently than the curved surface shape of the sphere. Table 1 shows the light use efficiency for the curved surface of the sphere and the curved surface of the spheroid.

  When a metal layer is formed on the light reflecting surface 8, it is preferable that a metal layer having high reflectivity such as Ag, Al, Au, Cu, Pt, Zn, Ni, Cr is formed. A metal layer made of Al and / or Ag is preferred.

  The metal layer can be formed thin with a uniform thickness by a method such as vacuum deposition, sputtering, electroless plating, or electrolytic plating.

  The thickness of the metal layer forming the light reflecting surface 8 is preferably 0.04 to 0.2 μm. When the thickness is less than 0.04 μm, the reflectance decreases and the light transmittance increases. When the thickness exceeds 0.2 μm, the surface of the metal layer becomes uneven, and the reflected light is scattered.

  The light reflecting member 7 is placed on the light-transmitting conductive layer 5 between the crystal semiconductor particles 2 and adhered as it is so that the crystal semiconductor particles 2 are exposed from the polygonal openings 17 of the light reflecting member 7. Alternatively, as shown in FIG. 3, the light reflecting member 7 is placed on the translucent conductive layer 5, the surface filling layer 9 and the surface protector 10 are sequentially laminated and sealed with a vacuum heating device or the like. , Installed at a predetermined site. Thereby, it is not necessary to perform the operation | work which inserts the crystalline semiconductor particle 2 in the opening part of one individual aluminum foil like the conventional manufacturing method, and the light reflection member 7 can be installed stably at once and easily. .

  The crystal semiconductor particles 2 have a slight variation in particle size (tolerance), and in the case of the circular opening 18, it is necessary to match at least the size of the crystal semiconductor particles 2 having the largest particle size (FIG. 4 (c). )).

  However, when the crystalline semiconductor particles 2 having a small particle diameter are inserted into the circular opening 18, the light incident on the gap region between the opening 18 and the crystalline semiconductor particle 2 does not contribute to photoelectric conversion and thus collects. Light loss. The ratio of the condensing loss is the area of the interval with respect to one unit area of the light reflecting member 7, and the ratio of the condensing loss depends on the particle size variation.

  On the other hand, by using the polygonal opening 17, the area of the gap between the opening 17 and the crystalline semiconductor particles 2 can be reduced.

  As shown in FIGS. 2, 4A and 4B, when the shape of the opening 17 is a regular polygon, a large number of spherical crystalline semiconductor particles 2 are collectively inserted into the opening 17, respectively. It becomes even easier. The opening 17 circumscribes a circle having a maximum diameter in the particle size distribution of the crystal semiconductor particles 2 (the circumscribed circle 21) and inscribed in a circle having the minimum diameter (the inscribed circle 20). In this case, it is easier to collectively insert a large number of spherical crystal semiconductor particles 2 into the openings 17 and minimize the gap between the crystal semiconductor particles 2 and the openings 17. Can be small.

  4A and 4B are circumscribed on the circumscribed circle 21 corresponding to the crystal semiconductor particle 2 having the largest particle diameter and inscribed on the inscribed circle 20 corresponding to the crystal semiconductor particle 2 having the smallest particle diameter. This is an example of a regular hexagonal opening 17.

  When the crystalline semiconductor particles 2 having a diameter equal to or larger than the diameter of the inscribed circle 20 and smaller than the diameter of the circumscribed circle 21 are inserted, the light reflecting member 7 is made of a flexible resin. The side part of the polygonal opening 17 in contact with 2 is deformed, and the crystalline semiconductor particles 2 can be inserted into the opening 17. Moreover, since the area of the gap can be made smaller than when the opening 17 is circular, the ratio of condensing loss is reduced.

  The polygonal opening 17 is preferably from a regular triangle to a regular octagon in consideration of the grain size tolerance. For example, when the tolerance ratio (tolerance / center grain size) is about 15%, it is a regular square and about 7%. Select a regular hexagon.

  Further, since the light reflecting member 7 has flexibility, even the crystalline semiconductor particles 2 having a diameter slightly larger than the diameter of the circumscribed circle 21 can be inserted into the opening 17.

  The opening 17 may be formed at the same time as the light reflecting member 7 is formed, or may be formed by a punching method or the like after the light reflecting member 7 is formed.

  As shown in FIG. 1, the light reflecting member 7 is formed by integrally forming a conductive plate made of copper, aluminum, silver, gold or the like on the lower surface of the light reflecting member 7 or an electrode layer 13 that is a conductive foil, and then forming a conductive adhesive layer 16. It is preferable to adhere on the translucent conductive layer 5, so that the light reflecting member 7 can be more stably and easily installed.

  In the case where a metal layer is formed on the light reflecting surface 8, the main body portion of the light reflecting member 7 excluding the light reflecting surface 8 is made of a resin such as polycarbonate resin, polyethylene terephthalate resin, acrylic resin, fluorine resin, or olefin resin. It is formed. The curved surface shape of the light reflecting surface 8 is formed of resin, metal, or a material capable of maintaining the shape, and an opening is provided at the bottom of the concave curved shape so that the crystalline semiconductor particles 2 can enter. The resin is preferably a resin having flexibility that can be easily deformed under atmospheric pressure. By doing so, the reflection efficiency is improved without the floating of the light reflecting member 7 from the translucent conductive layer 5 spreading to the periphery. Even if the conductive substrate 1, the electrode layer 13, or the insulating layer 4 has irregularities, the light reflecting member 7 can be placed on the upper part thereof.

  It is preferable that the light reflecting member 7 has a sharp apex at the top (boundary portion between the concave mirrors) in the longitudinal section. Conventionally, when the boundary as shown in Patent Document 3 is wide, the horizontal part of the boundary is wide, and therefore light incident on the boundary is reflected upward. The photoelectric conversion device of the present invention suppresses the upward reflection of the incident light at the top, and efficiently concentrates the incident light on the crystal semiconductor particles 2 because the top is an acute-pointed cusp. be able to. The angle of the acute-angled cusp is about 5 ° to 60 °.

  In this case, the metal layer is preferably bent at the top. Thereby, reflection of light at the top of the metal layer can be almost eliminated.

  The light reflecting member 7 is molded by laminating a resin, a metal, or a material capable of maintaining the shape by a molding die having a large number of convex negative shapes (concave shapes) formed of a heat-resistant material such as metal. The light reflecting surface 8 is a metal layer having a high reflectivity such as Ag, Al, Au, Cu, Pt, Zn, Ni, and Cr by a method such as vacuum deposition, sputtering, electroless plating, or electrolytic plating. Or by integrally molding the metal foil with the resin.

<Transparent protective layer>
The photoelectric conversion device of the present invention includes a transparent protective layer 12 that covers the light reflecting surface 8. The transparent protective layer 12 is a surface of the light reflecting surface 8 depending on the surface roughness of the molding die, for example, when a resin sheet to be the light reflecting member 7 having a metal layer as the light reflecting surface 8 on one main surface is formed. This is to prevent damage to the light reflecting surface 8 that is likely to occur in the manufacturing process of the photoelectric conversion device. Then, by providing the transparent protective layer 12 and protecting the light reflecting surface 8 from directly contacting the mold, it is possible to prevent a decrease in the reflectance of the light reflecting surface 8 in the manufacturing process. Furthermore, the deterioration of the light reflecting surface 8 can be suppressed with respect to the problem that the light reflecting surface 8 made of a metal is easily deteriorated by sulfur gas or oxygen by being used for a long time.

  The transparent protective layer 12 is made of a resin such as polyethylene resin, polyethylene terephthalate resin, polycarbonate resin, acrylic resin, fluorine resin, or olefin resin.

  These resins preferably have a refractive index difference of 0.2 or less, more preferably 0.1 or less, and most preferably no refractive index difference with the surface filling layer 9 (FIG. 3) described later. preferable. By doing so, even if the molding die is transferred to the transparent protective layer 12 to some extent, the optical loss is reduced. In this case, even if the surface roughness of the molding die is transferred to the transparent protective layer 12 to some extent, the optical loss is reduced.

  Although the thickness of the transparent protective layer 12 depends on the surface roughness of the molding die, it may be about 1 μm to 50 μm, and if it is less than 1 μm, scratches due to the surface roughness of the molding die cannot be prevented, and if it exceeds 50 μm. The light-reflecting surface 8 after molding is rounded at the ridges at the boundaries of the recesses, so that desired light collection cannot be obtained. By providing the transparent protective layer 12, the corrosion resistance of the light reflecting surface 8 can be improved, and higher reliability can be obtained. A separate anticorrosion coat may be provided between the light reflecting surface 8 and the transparent protective layer 12.

  When a metal layer is formed on the light reflecting surface 8, the metal layer is preferably electrically insulated from the translucent conductive layer 5. By doing so, since there is no electrical continuity from the translucent conductive layer 5 to the metal layer, the current collection effect such as the electrode layer 13 is sufficiently collected, and the current collection effect is There is a tendency to increase significantly.

  The top of the transparent protective layer 12 is preferably composed of a convex curved surface in the longitudinal section as shown in FIG. Since the top of the transparent protective layer 12 has a convex curved surface, the transparent protective layer 12 presses the metal layer from the outside, so that the metal layer is formed at an acute angle without being cut at the top of the light reflecting member 7. The effect is obtained. Further, the top of the transparent protective layer 12 is formed from a convex curved surface in the longitudinal section, and the top of the light reflecting member 7 is an acute-pointed point in the longitudinal section. As a result, a synergistic effect is obtained in that the light applied to the light is reflected by the adjacent crystal semiconductor particles 2 without leaking to the outside and contributes to the photoelectric conversion effect.

<Electrode layer>
The electrode layer 13 has a conductive adhesive layer 16 on the translucent conductive layer 5 between the adjacent crystalline semiconductor particles 2 in order to reduce the series resistance value between the translucent conductive layer 5 and the external terminal. The photocurrent generated by the crystalline semiconductor particles 2 is used as a low-resistance conductor for taking out from the photoelectric conversion device without causing resistance loss.

  The electrode layer 13 is preferably made of a metal plate having an opening corresponding to the crystalline semiconductor particle 2, and for example, Al, Cu, Ni, Cr, Ag, and alloys thereof are suitable. The thickness of the electrode layer 13 is preferably 20 to 200 μm. The use of the electrode layer 13 made of a metal plate is preferable in that it also serves as a substrate that firmly supports the light reflecting member 7 formed thereon.

  The conductive adhesive layer 16 is made of an adhesive made of a thermosetting resin containing conductive particles, and electrically connects the electrode layer 13 and the translucent conductive layer 5. It plays the role of fixing. As the conductive particles, Ag, Ni, Au, or a composite particle thereof is suitable, and the translucent conductive layer 5 can efficiently collect the generated current with respect to the electrode layer 13. Further, the conductive adhesive layer 16 is formed in a circular shape (dot shape) so as to avoid the crystal semiconductor particles 2 and is arranged in a large number so as to be adjacent to the crystal semiconductor particles 2. An area can be eliminated. At the same time, the electrode layer 13 and the conductive adhesive layer 16 can be covered by the light reflecting member 7 described above, and the appearance can be improved. Furthermore, the electrical path of the translucent conductive layer 5 having relatively low conductivity can be shortened by the conductive adhesive layer 16, and the current generated in the crystalline semiconductor particles 2 can be efficiently collected by the electrode layer 13.

<Protective layer>
In the photoelectric conversion device of the present invention, a protective layer (not shown) may be formed on the translucent conductive layer 5. Such a protective layer preferably has a characteristic of a transparent dielectric, such as silicon oxide, cesium oxide, aluminum oxide, silicon nitride, titanium oxide, tantalum oxide, yttrium oxide, etc. by CVD or PVD. Are formed on the light-transmitting conductive layer 5 by a single composition or a combination of a single composition or a plurality of compositions.

  Since the protective layer is on the light incident surface side, the protective layer needs to be transparent, and is a dielectric in order to prevent current leakage between the semiconductor portion 3 or the translucent conductive layer 5 and the outside. It is necessary. In addition, if the thickness of the protective layer is optimized, a function as an antireflection film can be expected.

<Photoelectric conversion module>
Next, a photoelectric conversion module (FIG. 3) is formed using the photoelectric conversion device of the present invention. Here, the photoelectric conversion module is a module in which a plurality of photoelectric conversion elements are connected in series or in parallel, the generated electrical output is improved, and a practical electrical output can be taken out. The photoelectric conversion module can obtain a sufficient electrical output that could not be obtained with one photoelectric conversion element.

  The surface filling layer 9 on the light reflecting member 7 may be an optically transparent material, and examples of the constituent material include ethylene vinyl acetate polymer (EVA), polyolefin, fluorine-based resin, and silicone resin.

  The surface protector 10 on the surface filling layer 9 is made of an optically transparent and weather-resistant material, such as glass, silicone resin, polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), poly Such as tetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkoxy copolymer (PFA), tetrafluoroethylene-6 fluoropropylene copolymer (FEP), polytrifluoroethylene chloride (PCTFE), etc. A fluororesin can be used.

  Further, the back surface filling layer 11 can be provided on the back surface of the conductive substrate 1 using the same material as the material of the surface filling layer 9, and a back surface protective layer 14 may be further laminated. Examples of the material for the back surface protective layer 14 include fluororesins such as polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), and polytrifluoroethylene chloride (PCTFE), polyethylene terephthalate (PET), and the like. The resin is good. Examples of the back surface protective layer 14 include a sheet obtained by laminating an aluminum foil or a metal oxide film using these resins and a metal sheet such as glass or stainless steel.

  In the periphery of the photoelectric conversion device of the present invention, the light reflecting member 7 is a spacing member 15. The spacing member 15 can be easily formed by adding it to the periphery of the mold when forming the light reflecting member 7. The interval holding member 15 has a thickness corresponding to the interval between the surface protection body 10 and the insulating layer 4. When the surface protection body 10, the surface filling layer 9, and the photoelectric conversion device are combined and vacuum heated, The light reflecting member 7 on the conversion device has a role of securing the interval so as not to be destroyed.

  Further, the spacing member 15 may be formed inside the photoelectric conversion device. When the photoelectric conversion device is large, the spacing member 15 formed inside is effective. At this time, one spacing member 15 may be provided in a region corresponding to one crystalline semiconductor particle, or a plurality of spacing members 15 may be arranged.

  Note that a photoelectric conversion device in which one photoelectric conversion element (a photoelectric conversion unit having one crystal semiconductor particle 2) having the above-described configuration is provided or a plurality of photoelectric conversion elements are connected (connected in series, parallel, or series-parallel) To do. Further, one photoelectric conversion device is provided, or a plurality of devices connected in series (connected in series, parallel, or series-parallel) is used as the power generation means, and the generated power is directly supplied from the power generation means to the DC load. Good. In addition, after the power generation means converts the generated power to appropriate AC power via power conversion means such as an inverter, the generated power can be supplied to an AC load such as a commercial power system or various electric devices. It is good also as a power generator. Furthermore, it is also possible to use such a power generation device as a photovoltaic power generation device such as a solar power generation system in various modes by installing it on the roof or wall surface of a building with good sunlight.

  Next, although the Example of the photoelectric conversion apparatus of this invention is described, this invention is not limited to this Example.

  The photoelectric conversion device of the example was manufactured as shown below.

  First, as crystal semiconductor particles, a large number of p-type crystal silicon particles having a center diameter of about 0.3 mm and a particle size tolerance ratio of about 7% are used. As a result, a pn junction was formed.

  Next, a large number (30,000) of crystalline silicon particles are arranged on the main surface of the conductive substrate made of aluminum at an interval of about 0.6 times the diameter, and the eutectic temperature of aluminum and silicon. A large number of crystalline silicon particles were bonded onto a conductive substrate by heating at a temperature of 577 ° C. or higher (630 ° C.) for about 10 minutes.

  After the pn separation was performed by etching around the base of the crystalline silicon particles bonded to the conductive substrate, an insulating layer made of polyimide was filled between a large number of crystalline silicon particles on the conductive substrate. Thereafter, the upper surface of the crystalline silicon particles was washed, and an ITO film having a thickness of 80 nm was formed as a translucent conductive layer.

  Furthermore, as an electrode layer (collector electrode), an aluminum foil having a thickness of 50 μm having through holes about the diameter of the crystalline silicon particles was used, and an Ag paste (on the lower surface of the aluminum foil surrounded by three crystalline silicon particles) Ag particle-containing resin paste) was applied in the form of dots by screen printing. And the electrode layer was formed by heat-processing for 30 minutes at 150 degreeC, pressing on an ITO film | membrane so that a crystalline silicon particle might protrude from the through-hole of an electrode layer.

  Next, the light reflecting member was formed as follows. A light reflecting member was formed by a vacuum forming method using a mold in which a large number of vertically long semi-spheroid shapes were arranged with a width 1.6 times the diameter of the crystalline silicon particles.

  A PET sheet having a thickness of 25 μm in which a silver layer having a thickness of 80 nm constituting the light reflecting surface was formed was laminated on the upper surface of the polycarbonate resin film as the main body of the light reflecting member. And the light reflection member was produced by laminating | stacking the polyester film (thickness 1.5 micrometers) as a transparent protective layer on the upper surface of the silver layer.

  The shape of the light reflecting member is a shape having a concave light reflecting surface for condensing the crystalline silicon particles and an opening exposing the upper portion of the crystalline silicon particles at the lower end of the light reflecting surface. A large number of light reflecting surfaces and openings corresponding to the particles were formed. At this time, the shape of the opening was a regular hexagonal shape with a side of about 0.16 mm because the center diameter of the crystalline semiconductor particles was about 0.3 mm and the particle size tolerance ratio was about 7%.

And the light reflection member was arrange | positioned on the translucent conductive layer on an insulating layer so that a crystalline silicon particle might each protrude from the opening part of a light reflection member. Further, a backside filling layer made of EVA and having a thickness of about 0.4 mm and a backside protective layer having a thickness of about 0.1 mm formed by laminating a PET film, a SiO ₂ layer, and a PET film were laminated on the lower surface of the conductive substrate. Then, on the upper surface side of the conductive substrate, a surface filling layer made of EVA having a thickness of about 0.6 mm and a surface protective body made of glass having a thickness of about 3 mm are sequentially laminated so as to cover the light reflecting member, and these are laminated in a vacuum laminator. The photoelectric conversion device was produced by laminating by the above.

(Comparative example)
Since the shape of the opening of the light reflecting member is about 0.3 mm of the center diameter of the crystalline semiconductor particles and the particle size tolerance ratio is about 7%, the configuration is the same as in the embodiment except that the shape is circular with a diameter of about 0.32 mm. As a result, a photoelectric conversion device of a comparative example was produced.

  The photoelectric conversion efficiency was measured and compared for the photoelectric conversion devices of the above Examples and Comparative Examples. As a result, when the photoelectric conversion efficiency of the comparative example was 1, the photoelectric conversion efficiency of the example was 1.04, indicating an improvement of about 4%. As a result, in the comparative example, since the shape of the opening of the light reflecting member was circular, the loss was large due to the large gap between the crystalline silicon particles and the opening, whereas in the example, the light reflecting member It is considered that the gap between the crystalline silicon particles and the opening is improved because the shape of the opening is a regular hexagon.

  Further, in the photoelectric conversion device of the example, all of 30,000 crystalline silicon particles could be inserted into the opening, but in the photoelectric conversion device of the comparative example, about 250 out of 30,000 crystalline silicon particles. Could not be inserted into the opening.

  In addition, this invention is not limited to said embodiment and Example, A various change can be given in the range which does not deviate from the summary of this invention.

It is sectional drawing which shows an example of embodiment about the photoelectric conversion apparatus of this invention. It is a fragmentary top view which shows an example of embodiment about the photoelectric conversion apparatus of this invention. It is sectional drawing of the photoelectric conversion module produced using the photoelectric conversion apparatus of FIG. (A), (b) is a top view of the regular hexagonal opening part in the photoelectric conversion apparatus of this invention, (c) is a top view of the circular opening part in the conventional photoelectric conversion apparatus.

Explanation of symbols

1: Conductive substrate 2: Crystalline semiconductor particle 3: Semiconductor portion 4: Insulating layer 5: Translucent conductive layer 7: Light reflecting member 8: Light reflecting surface 17: Polygonal opening

Claims (8)

  A conductive substrate; a second conductive type semiconductor portion formed on a surface layer; and a plurality of spherical first conductive type crystalline semiconductor particles bonded to each other at a distance from each other on the conductive substrate; and the conductive An insulating layer formed between the crystalline semiconductor particles on the substrate; a translucent conductive layer formed on the insulating layer and on the crystalline semiconductor particle; and the translucent conductive layer on the insulating layer A light reflecting member formed of a resin having a concave light reflecting surface that is formed and focused on the crystal semiconductor particles, and a polygonal opening that exposes an upper portion of the crystal semiconductor particles at a lower end of the light reflecting surface; A photoelectric conversion device.   The photoelectric conversion device according to claim 1, wherein the shape of the opening is a regular polygon.   3. The photoelectric conversion device according to claim 1, wherein the opening is circumscribed by a circle having a maximum diameter in a particle size distribution of the plurality of crystal semiconductor particles and inscribed in a circle having a minimum diameter.   The photoelectric conversion device according to claim 1, wherein a metal layer is formed on the light reflecting surface, and a transparent protective layer is formed on the metal layer.   The photoelectric conversion device according to claim 4, wherein the metal layer is made of aluminum and / or silver.   The photoelectric conversion device according to claim 4, wherein the metal layer and the translucent conductive layer are electrically insulated.   The photoelectric conversion device according to any one of claims 1 to 6, wherein the light reflecting member has an acute-angled pointed head in a longitudinal section.   The photoelectric conversion device according to claim 1, wherein the transparent protective layer has a convex curved surface at the top in a longitudinal section.

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