JP6192562B2 - Solar cell element and solar cell module - Google Patents

Description

  The present invention relates to a solar cell element and a solar cell module.

  Conventionally, as a photoelectric conversion device typified by a solar cell, for example, a back electrode on one surface side of a substrate, a light-receiving surface side on the other surface, a photoelectric conversion layer composed of a semiconductor layer on which light is incident, and a light transmission on the photoelectric conversion layer Electrode, a current collecting electrode on a translucent electrode, and a surface protective layer are sequentially formed. This photoelectric conversion device generates a photovoltaic potential by generating a diffusion potential in the photoelectric conversion layer by light incidence and collecting the generated electron-hole pairs.

  In such a photoelectric conversion device, in order to improve the photoelectric conversion efficiency, the light incident on the photovoltaic device is scattered to increase the optical path length in the semiconductor layer, and the amount of light absorbed in the semiconductor layer There is a method of increasing the short-circuit current by increasing. For example, it is known that incident light is scattered inside the photoelectric conversion layer, the optical path length is extended, and the light can be confined by a minute uneven structure called a texture applied to the surface of the photoelectric conversion layer.

  For example, in Patent Document 1, in order to solve these problems, by providing fine particles that cause light scattering in the surface protective layer, the optical path length in the photoelectric conversion layer is extended to increase light absorption and increase the short-circuit current. This increases the photoelectric conversion efficiency.

  By the way, in recent years, a photoelectric conversion device is left as it is, and a photon having a specific wavelength in the spectrum of sunlight is converted into a photon having a wavelength optimum for the photoelectric conversion device to be used and absorbed by the photoelectric conversion device (hereinafter referred to as wavelength). Conversion) has been proposed. Wavelength conversion is currently available for high energy photons that are not currently used effectively, including down conversion that converts one photon into multiple low energy photons and downshift that converts one photon into one low energy photon. Low-energy photons that are not used can be classified into up-conversions that convert energy photons that are effective for photoelectric conversion using the energy of a plurality of low-energy photons.

  For example, in Patent Document 2, a wavelength conversion layer that converts the wavelength of high energy photons having low photoelectric conversion efficiency into a plurality of low energy photons that are more suitable for photoelectric conversion is disposed at a position closer to the light incident side than the photoelectric conversion layer, In addition, a technique is disclosed in which a wavelength conversion layer that converts a plurality of low energy photons having low photoelectric conversion efficiency into higher energy photons that are more suitable for photoelectric conversion is disposed at a position opposite to the light incident side than the photoelectric conversion layer. ing.

  Furthermore, a method for disposing a wavelength conversion layer is also shown for a solar cell module. For example, in Patent Document 3, a solar cell module in which a wavelength conversion layer and a light reflection layer are provided in order from the solar cell element side on the surface opposite to the light receiving surface of the solar cell element is configured. A solar cell module by converting short-wavelength light leaked to the back surface without being used in the light into long-wavelength light used for power generation in the wavelength conversion layer and reflecting it toward the solar cell element in the light reflection layer A technique for increasing the amount of power generation is disclosed.

JP-A-5-335610 JP 2011-151068 A JP 2012-129391 A

  In the above-mentioned patent document 1, it is said that by providing fine particles that cause light scattering, there is an effect of increasing light absorption by extending the optical path length in the photoelectric conversion layer. However, for light in a wavelength region with low spectral sensitivity, a large effect cannot be expected in light absorption by the photoelectric conversion layer by extending the optical path length.

  Further, in Patent Document 2, the wavelength conversion unit is disposed on the light incident side with respect to the photoelectric conversion layer and on the opposite side of the light incidence with respect to the photoelectric conversion layer, and is perpendicular to the layers constituting the photoelectric conversion layer. A wavelength conversion layer is provided over the entire surface direction. In such a structure, the wavelength conversion layer disposed on the light incident side or the opposite side of the light incidence with respect to the photoelectric conversion layer absorbs a part of light having a wavelength contributing to power generation by being absorbed by the photoelectric conversion layer. Since it absorbs, there exists a problem that the power generation gain by wavelength conversion becomes small. Further, there is a problem that the material cost is increased by providing the wavelength conversion layer over the entire surface direction perpendicular to the layers constituting the photoelectric conversion layer. A similar problem exists in Patent Document 3.

  In general, in a photoelectric conversion device, current collecting electrodes for taking out generated carriers to the outside exist on the light receiving surface and the back surface, respectively. In such a photoelectric conversion device, of the light incident on the photoelectric conversion device from the light receiving side, the light applied to the current collecting electrode is blocked by the current collecting electrode and does not contribute to power generation.

  The present invention has been made in view of the above, and the solar cell element and the solar cell module having high photoelectric conversion efficiency by increasing the generated current by effectively using the light applied to the collecting electrode for power generation The purpose is to obtain.

In order to solve the above-described problems and achieve the object, the present invention includes a semiconductor layer constituting a photoelectric conversion unit, and first and second current collecting electrodes sandwiching the semiconductor layer. which are in between the first collector electrode and a semiconductor layer formed on the light-receiving surface of the collector electrode, having a wavelength conversion layer only provided directly under the first collector electrode.

  According to the present invention, of the light incident on the solar cell element from the light receiving surface side, the light collected by the current collecting electrode is irradiated to the current collecting electrode and is blocked by the current collecting electrode and does not contribute to power generation. The wavelength conversion material converts the wavelength into light having a high spectral sensitivity of the solar cell element and scatters it. Part of the scattered light is incident on the photoelectric conversion layer and is efficiently photoelectrically converted due to the wavelength light with high spectral sensitivity of the solar cell element, so that the generated current can be increased and the power generation efficiency is increased. There is an effect.

FIG. 1 is a top view showing the structure of the solar cell module according to Embodiment 1. FIG. FIG. 2 is a perspective view showing the structure of the solar cell element of the first embodiment. FIG. 3 is a cross-sectional view showing the structure of the solar cell module according to the first embodiment. 4 (a) and 4 (b) are cross-sectional views showing the structure of the solar cell element of the first embodiment. FIG. 4 (a) is a cross-sectional view taken along line C1-C1 in FIG. 1, and FIG. It is C2 sectional drawing. FIG. 5 is a cross-sectional view showing the structure of the downshift wavelength conversion layer in the solar cell module of the first embodiment. 6A to 6F are process cross-sectional views illustrating the method for manufacturing the solar cell element according to the first embodiment. FIG. 7 is a partial cross-sectional view showing a part of the configuration of the solar cell module of the first embodiment. FIG. 8 is a diagram showing a locus of incident light in the solar cell module according to the first embodiment. FIG. 9 is a diagram showing the quantum efficiency of a typical silicon module. FIG. 10 is a diagram showing the solar cell module of Embodiment 2 and the locus of incident light. FIG. 11 is a diagram showing the solar cell module of Embodiment 3 and the locus of incident light.

  EMBODIMENT OF THE INVENTION Below, embodiment of a solar cell module is demonstrated in detail based on drawing as a photoelectric conversion apparatus concerning this invention. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings.

Embodiment 1 FIG.
FIG. 1 is a top view showing an example of the structure of the solar cell module according to Embodiment 1, and is a view seen from the light receiving surface side of sunlight. FIG. 2 is a perspective view showing the structure of the solar cell element 20 used in the solar cell module 100 of the first embodiment. On the surface of the solar cell element 20 are a thick wavelength conversion layer 7R and a bus current collecting electrode 7a, and a thin grid current collecting electrode also called a finger electrode so as to run perpendicular to the bus current collecting electrode 7a. 8 is formed. FIG. 3 is a cross-sectional view showing the structure of the solar cell module 100 of the first embodiment, and is a cross section taken along the dotted line AB in FIG. In this solar cell module 100, a plurality of solar cell elements 20 are interconnected by an interconnector 40, a glass plate 10 as a light-receiving surface side protection member (translucent substrate), and a back film 11 as a back surface side protection member. In between, it is sealed with sealing resin 9. The solar cell element 20 includes first and second current collecting electrodes on the light receiving surface (first surface) 20A side surface and the back surface (second surface) 20B side surface, and is arranged adjacent to the solar cell. The electrodes of the element 20 are connected in series by an interconnector 40. The first current collecting electrode on the light receiving surface 20A side is composed of the bus current collecting electrode 7a and the grid current collecting electrode 8, and the current collecting material on the back surface side as the second current collecting electrode on the entire back surface 20B of the solar cell element 20. An electrode 6 is formed. The interconnector 40 is electrically connected to the bus collector electrode 7a. Reference numeral 30 denotes an external lead. This wavelength conversion layer 7R is blocked by the bus current collecting electrode, and converts the wavelength of light that does not contribute to photoelectric conversion to the photoelectric conversion unit.

  FIGS. 4A and 4B are cross-sectional views showing a schematic configuration of the solar cell element 20 used in the solar cell module 100 of the first embodiment, and FIG. C1 sectional drawing, (b) is C2-C2 sectional drawing of FIG. The wavelength conversion layer 7R is provided on the light receiving surface 20A side of the solar cell element 20, and the bus current collecting electrode 7a is provided on the surface of the wavelength conversion layer 7R. The battery element 20 is converted to light having a wavelength with high spectral sensitivity. 4A shows a cross section in which the grid current collecting electrode 8 is not formed on the bus current collecting electrode 7a, and the wavelength conversion layer 7R, the bus current collecting electrode 7a, Is formed. In the C2-C2 cross-sectional view shown in FIG. 4B, the grid current collecting electrode 8 is formed on the bus current collecting electrode 7a, and the grid current collecting electrode 8 and the bus current collecting electrode 7a are electrically connected. ing.

  Next, FIG. 5 schematically shows the bus collector electrode 7a and the wavelength conversion layer 7R. As shown in FIG. 5, the downshift type wavelength conversion layer 7R is formed under the bus collector electrode 7a, and is composed of a mixture of a base resin 7B made of a thermoplastic resin and particles R of the wavelength conversion material. Yes. The particle R of the wavelength conversion material is a downshift material that converts light having a wavelength of about 300 to 400 nm into light having a wavelength of about 400 to 900 nm.

These downshift materials may be dispersed in a light-transmitting polymer material such as an acrylic resin or a silicone resin. It can be formed into a solution using an appropriate solvent, and formed by a printing method, a spray coating method, or the like. The wavelength conversion layer 7R converts light having a wavelength of about 300 to 400 nm into light having a wavelength of about 400 to 900 nm. For example, the excitation wavelength is about 300 to 500 nm close to ultraviolet light, and the emission wavelength is 500 of visible light. CaAlSiN ₃ : Eu ²⁺ which is about 700 nm is used. Other inorganic fluorescent agents include zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium sulfide (CdS); Er ³⁺ , Yb ³⁺ , Ho ³⁺ , Pr ³⁺ , An inorganic fluorescent agent such as rare earth-containing YAG (yttrium, aluminum, garnet) containing rare earth elements such as Eu ³⁺ is used. An organic phosphor or the like may be used.

  FIG. 1 shows a solar cell module 100 in which twelve solar cell elements 20 are connected in series, but the number and arrangement can be arbitrarily changed, and parallel connection may be combined. Although not shown in the drawing, lead wires for taking out electric power to the back surface side of the solar cell module 100 are connected to both ends of the solar cell module 100.

  As the glass plate 10, for example, a material such as soda lime glass can be used. In a solar cell module used outdoors, a glass plate that has been thermally or chemically reinforced may be used as the light-receiving surface side protective material. The size of the glass plate 10 can be variously changed according to the number of the solar cell elements 20, but a typical thickness is 0.5 to 3 mm. As the back film 11, a film with low moisture permeability or a glass plate similar to the front side is used so that the solar cell element does not deteriorate due to intrusion of moisture or the like. In order to reflect the solar cell element 20 and the light that has passed through the gap between the solar cell element 20 and the solar cell element 20, a white or metallic light reflective material may be used as the back film 11. As the sealing resin 9, translucent EVA, silicone resin, or the like can be used. For the interconnector 40, for example, a copper wire coated with solder can be used.

  4A and 4B, the n-type semiconductor substrate is a thin semiconductor substrate made of crystalline silicon such as single crystal silicon or polycrystalline silicon, a compound semiconductor, or the like. In this embodiment, an n-type single crystal silicon substrate 1 is used. In the case of crystalline silicon, the typical substrate size is approximately 10 to 15 cm square, and the thickness is 0.1 to 0.3 mm.

  On the surfaces on both sides of the n-type single crystal silicon substrate 1, i-type amorphous silicon layers 2a and 2b are formed. A p-type amorphous silicon layer 3 containing impurities of a conductivity type opposite to that of the n-type single crystal silicon substrate 1 is formed on the i-type amorphous silicon layer 2a. The i-type amorphous silicon layer 2b formed on the substrate surface opposite to the side where the p-type amorphous silicon layer 3 is formed contains impurities of the same conductivity type as the n-type single crystal silicon substrate 1. An n-type amorphous silicon layer 4 is formed. Translucent electrodes 5 a and 5 b are formed on the p-type amorphous silicon layer 3 and the n-type amorphous silicon layer 4. A laminated pattern of the wavelength conversion layer 7R and the bus current collecting electrode 7a is formed on the translucent electrode 5a, and a grid current collecting electrode 8 is formed on the upper layer so as to be orthogonal to the laminated pattern. A current collecting electrode 6 on the back side is formed on the translucent electrode 5b. The current collecting electrode 6 on the back surface side is an electrode formed on the entire surface of the back surface of the solar cell element 20, and the bus current collecting electrode 7a is formed on the wavelength conversion layer 7R on the surface of the light receiving surface of the solar cell element 20. It is a thick line electrode. The grid current collecting electrode 8 is a thin line electrode that is in contact with the bus current collecting electrode 7a so as to be orthogonal thereto. The current collecting electrode 6 and the bus current collecting electrode 7a on the back side can be formed on both surfaces of the n-type single crystal silicon substrate 1 by printing a metal paste in which metal fine particles such as silver or copper and a resin are mixed. The current generated in the surface of the n-type single crystal silicon substrate 1 is collected by a film forming technique such as sputtering or plating. The bus collector electrode 7a is preferably a bus-like pattern in which thick lines extending in a straight line are arranged in parallel at intervals as shown in FIG. 2, but may be a mesh or dendritic pattern.

  As shown in FIGS. 4 (a) and 4 (b), the n-type single crystal silicon substrate 1 has fine irregularities (texture 1T) for preventing reflection on both surfaces. In the figure, both surfaces of the n-type single crystal silicon substrate 1 are uneven, but a flat layer may be formed on the back side, or both sides may be flat. Due to the presence of the texture 1T, unevenness is often formed up to the translucent electrodes 5a and 5b, and constitutes a diffusion surface.

  Next, the manufacturing method of the solar cell element 20 of the first embodiment will be described. 6A to 6F are cross-sectional views for explaining the procedure of the manufacturing method of the first embodiment. First, an n-type single crystal silicon substrate 1 is prepared as shown in FIG. 6A, and an uneven structure called texture 1T is formed on the surface of the n-type single crystal silicon substrate 1 as shown in FIG. 6B. . An acidic or alkaline etching solution is used to form the unevenness. Concavity and convexity formation may be performed only on the light incident side. Moreover, you may implement the process of removing the damage layer on the substrate surface before uneven | corrugated formation. In addition, it is desirable to improve the performance by performing gettering treatment of impurities in the substrate after the damaged layer removing step. As the gettering process, a phosphorus diffusion process or the like is used. In order to form unevenness only on the surface on the light-receiving surface side and keep the surface on the back-side surface flat, the n-type single electrode is processed with a process of contacting an etching solution only on the surface on the light-receiving surface side or with a protective film formed on the back-surface side. A process of etching the crystalline silicon substrate 1 is performed.

  After the unevenness is formed, the chemical vapor deposition (CVD) method is used in this order to form the i-type amorphous silicon layer 2a and the p-type amorphous silicon layer 3 on one side of the substrate as shown in FIG. Form. The i-type amorphous silicon layer 2a may have a thickness of about several nm, and the p-type amorphous silicon layer 3 may have a thickness of about several to 20 nm. Instead of the i-type amorphous silicon layer 2a, an i-type amorphous silicon carbide layer, an i-type amorphous silicon oxide layer, or a multilayer film in which these layers are stacked may be used. Instead of the p-type amorphous silicon layer 3, a p-type amorphous silicon carbide layer, a p-type amorphous silicon oxide layer, a p-type microcrystalline silicon layer, or a multilayer film in which these layers are stacked may be used.

  Next, as shown in FIG. 6D, an i-type amorphous silicon layer 2b and an n-type amorphous silicon layer 4 are formed in this order on the opposite side of the substrate by chemical vapor deposition. The thickness of the i-type amorphous silicon layer 2b is preferably about several nm, and the thickness of the n-type amorphous silicon layer 4 is preferably about several to 20 nm. Instead of the i-type amorphous silicon layer 2b, an i-type amorphous silicon carbide layer, an i-type amorphous silicon oxide layer, or a multilayer film in which these layers are stacked may be used. Instead of the n-type amorphous silicon layer 4, an n-type amorphous silicon carbide layer, an n-type amorphous silicon oxide layer, an n-type microcrystalline silicon layer, or a multilayer film in which these layers are stacked may be used.

  Next, in order to reduce interface defects between the i-type amorphous silicon layers 2a and 2b and the n-type single crystal silicon substrate 1, thermal annealing may be performed in an inert gas or a hydrogen gas diluted with an inert gas. . The annealing temperature is desirably 200 ° C. or lower.

After the thermal annealing treatment, as shown in FIG. 6E, translucent electrodes 5a and 5b are formed on the p-type amorphous silicon layer 3 and the n-type amorphous silicon layer 4, respectively, by sputtering or vapor deposition. And so on. The film thickness of the translucent electrodes 5a and 5b is desirably a film thickness at which the reflectance decreases at the peak wavelength of the sunlight spectrum due to the interference effect. As the light-transmitting electrode material, ITO, indium oxide (In ₂ O ₃ : Indium Oxide), SnO ₂ , ZnO, or the like may be used. In addition, it is desirable that the translucent electrode has a low resistivity, but if the carrier density responsible for conductivity is high, the light absorptance increases. Therefore, the material used as the translucent electrode needs to have high mobility.

  Next, as shown in FIG. 6F, the wavelength conversion layer 7R and the bus collector electrode 7a are sequentially formed on the translucent electrode 5a by the screen printing method. Next, the grid current collecting electrode 8 is formed so as to run on the bus current collecting electrode 7a. After that, the collector electrode 6 made of a metal paste is formed on the back side of the n-type single crystal silicon substrate 1 by screen printing. The width of the wavelength conversion layer 7R on the light receiving surface side is preferably as narrow as possible in order to suppress light shielding. However, since the width of the bus current collecting electrode 7a formed later on the wavelength conversion layer 7R is also narrowed, the resistance increases. Therefore, it is desirable that the bus collector electrode 7a on the light receiving surface side has a large layer thickness, and a screen printing method may be used so as to repeatedly overlap the same pattern.

  As described above, the wavelength conversion layer 7R, the bus collector electrode 7a, and the grid collector electrode 8 on the light receiving surface side are formed in the order of the wavelength conversion layer 7R, the bus collector electrode 7a, and the grid collector electrode 8. carry out. Thereby, electrical contact between the bus current collecting electrode 7a and the grid current collecting electrode 8 can be ensured. Further, the current collecting electrode 6 on the back side is formed on the translucent electrode 5b by printing on the entire surface. Baking is performed after the collector electrode 6, the wavelength conversion layer 7R, the bus collector electrode 7a, and the grid collector electrode 8 are printed. In the high-temperature heat treatment, since the i-type amorphous silicon layers 2a and 2b are crystallized, the firing temperature after screen printing is desirably 200 ° C. or lower.

Further, a screen printing method or the like is used to form the bus collector electrode 7a on the wavelength conversion layer 7R. In the layer formation, a plurality of screen printings may be repeated to ensure the thickness. Alternatively, a two-layer sheet of the bus current collecting electrode 7a and the wavelength conversion layer 7R may be prepared and cut and pasted into a strip shape, or the wavelength conversion material may be shaped into a sheet having a desired thickness, You may make it cut | disconnect to a desired width | variety and stick this. In this embodiment, the width of the bus collector electrode 7a on the wavelength conversion layer 7R may be the same as the width of the wavelength conversion layer 7R. However, in consideration of the process margin, it is desirable that the width is smaller than the wavelength conversion layer 7R, and about 800 μm. The layer thickness was 20 μm. The wavelength conversion layer 7R converts light having a wavelength of about 300 to 400 nm, which has a low spectral sensitivity of silicon, into light having a wavelength of about 400 to 900 nm, which has a high spectral sensitivity of silicon. Screen printing method after using CaAlSiN ₃ : Eu ²⁺ having an emission wavelength in the visible light region of about 500 to 700 nm and dispersing in a material such as a polymer to form a solution using an appropriate solvent. And so on. Other inorganic fluorescent agents include zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), cadmium sulfide (CdS); Er ³⁺ , Yb ³⁺ , Ho ³⁺ , Pr ³⁺ , An inorganic fluorescent agent such as rare earth-containing YAG (yttrium, aluminum, garnet) containing rare earth elements such as Eu ³⁺ is used. An organic phosphor or the like may be used. These downshift materials may be formed by screen printing or the like after being dispersed in a material such as a translucent polymer such as a silicone resin and made into a solution using an appropriate solvent. By performing the above steps, the solar cell element 20 shown in FIGS. 4A and 4B is obtained.

  When using a downshift material, the sealing resin 9 is not a material that absorbs short-wavelength light such as EVA or acrylic resin, and uses a member having a high light transmittance around 300 to 350 nm, such as silicone. By doing so, the conversion efficiency can be improved.

  In addition, although said solar cell element 20 is a heterojunction type solar cell element, it is good also as another diffusion type solar cell element etc., for example. In general, since the heterojunction solar cell element has lower current conversion efficiency in a short wavelength region such as ultraviolet light than the diffusion solar cell element, the effect of the wavelength conversion layer 7R is greater in the heterojunction solar cell element. .

  Next, the manufacturing method of the solar cell module 100 of the first embodiment will be described. As the solar cell element, the solar cell element of the first embodiment is used. FIG. 7 is a partial cross-sectional view showing a portion including two adjacent solar cell elements 20 in the solar cell module of FIG. Next, the solar cell elements 20 are connected by the interconnector 40. For the connection of the interconnector 40, a low melting point solder or the like is used. The interconnector 40 that connects two adjacent solar cell elements ensures electrical continuity by connecting to the bus current collecting electrode 7 a covered with the grid current collecting electrode 8 on the solar cell element 20. When the interconnector 40 is connected, the lower wavelength conversion layer 7R is also melted through the bus current collecting electrode 7a covered with the grid current collecting electrode 8, and the connection with the translucent electrode 5a becomes strong and good. Next, the glass plate 10, the sealing resin 9, the solar cell element 20, the sealing resin 9, and the back film 11 connected to each other by the interconnector 40 are sequentially stacked, and a sealing process of pressing with heating in vacuum is performed. . The sealing resin 9 melts and fills the gap between the glass plate 10 on the light receiving surface side and the back film 11 on the back surface side, and fixes the solar cell element 20. In this way, the solar cell module 100 shown in FIG. 7 is completed.

Next, the locus of light incident on the solar cell module 100 will be described. FIG. 8 is a partial cross-sectional view of the solar cell module 100 of FIG. 3 in which the interconnector 40 is omitted and a portion including one solar cell element is taken out, and the incident light from the light receiving surface side and its locus are shown. Is shown. A part of the light L ₀₁ incident on the light receiving surface of the solar cell module is reflected by the layer forming the solar cell element 20 like the light L ₀₂ . Such reflection is caused by a difference in refractive index at the interface of each layer. Light L ₀₂ is at the light-receiving surface side of the bus collecting electrode 7a immediately below the formed wavelength conversion layer 7R, it is converted into light of a high order of 400~900nm spectral sensitivity of solar cell elements is scattered. A part of the scattered light L ₀₃ is incident on the photoelectric conversion layer and is efficiently photoelectrically converted because of the light having a wavelength of about 400 to 900 nm, which is much absorbed by the solar cell element 20. As a result, the generated current can be increased as compared with the conventional structure, and the effect of increasing the power generation efficiency can be obtained.

Note that, as described above, the wavelength conversion layer 7R formed by printing or the like under the bus collector electrode 7a on the light receiving surface side contains a large amount of fine particles, and therefore is incident directly under the bus current collector electrode 7a on the light receiving surface side. The light L ₀₂ is scattered and reflected by the wavelength conversion layer 7R, and the transmittance of the bus collector electrode 7a is almost zero. Therefore, most of the light L ₀₂ incident on the wavelength conversion layer 7R is like the light L ₀₃ . It is considered to be incident on the photoelectric conversion layer. Here, in order to increase the incident amount of the light L ₀₃ reflected on the light receiving surface side of the solar cell element 20 to the solar cell element 20, the sealing resin 9 disposed on the light receiving surface side of the solar cell element 20 is used. It is preferable to make the thickness as thin as possible within a range thicker than the bus collector electrode 7a or the interconnector 40 on the light receiving surface side so that the impact resistance is not lost.

  FIG. 9 shows the quantum efficiency of a typical silicon module. It can be seen that the spectral sensitivity with a wavelength of about 300 to 400 nm centered on ultraviolet light and the infrared wavelength of about 1000 to 1200 nm is low, and the spectral sensitivity with a wavelength of about 400 to 900 nm centered on visible light is high.

  As described above, in the first embodiment, the wavelength conversion layer 7 </ b> R is installed directly below the bus current collecting electrode 7 a on the light receiving surface side of the solar cell element 20. The effect in this case will be described. Part of the light incident on the light receiving surface is converted into light having a light absorption of about 400 to 900 nm by the solar cell element 20 in the wavelength conversion layer 7R formed immediately below the bus current collecting electrode 7a on the light receiving surface side. Scattered. Most of the scattered light is incident on the photoelectric conversion layer 7R, and is efficiently photoelectrically converted because of the wavelength light with high spectral sensitivity of the solar cell element 20. As a result, the generated current can be increased as compared with the conventional structure, and the effect of increasing the power generation efficiency can be obtained.

  In addition, the unevenness of the texture 1T is slightly reflected on the translucent electrode 5a formed on the surface of the n-type single crystal silicon substrate 1 where the texture 1T is formed, and the wavelength conversion layer 7R is formed on the uneven surface. The bus collector electrode 7a is formed on the upper layer. Accordingly, the adhesion between the substrate and the wavelength conversion layer 7R is good, and the scattering property after wavelength conversion is also very good. And current collection is very good by the grid current collection electrode 8 riding on the bus current collection electrode 7a, and the current collection resistance can be kept small.

  The following is an estimate of the improvement in conversion efficiency expected by the downshift wavelength conversion layer. Of the sunlight incident on the module, about 95% of light having a wavelength of 350 to 400 nm centered on ultraviolet light is reflected on the light receiving surface of the solar cell element 20 except for about 5% reflected by the glass plate 10. Incident. In addition, when silicone was used as the sealing resin 9, it was considered that the transmittance of light having a wavelength of about 350 to 400 nm is approximately 100%. Assuming that the area ratio of the surface of the solar cell element 20 to the panel surface is 90%, the area of the bus collector electrode 7a occupying the entire area of the solar cell element 20 is about 1%. It can be said that the ratio of light having a wavelength of about 350 to 400 nm that is wavelength-converted by the downshift wavelength conversion layer is about 0.9% of the amount of light having a wavelength of about 350 to 400 nm incident on the module.

  Next, in the solar ray air mass 1.5 falling on the ground, among the generated current in a typical silicon solar cell module, the current due to light having a wavelength of 350 to 400 nm is approximately 1.1%, and the wavelength 400 to 400%. The power generation current of light per unit wavelength of 900 nm is estimated to be about four times that of the light generation current of light per unit wavelength of 350 to 400 nm. Therefore, it is estimated that the generation current and the conversion efficiency are increased by about 0.03% due to the presence of the downshift wavelength conversion layer. Here, the solar air mass refers to the amount of air passing, AM1.0 means light incident from an incident angle of light of 90 degrees (directly above), and AM1.5 is 1.5 times the amount of passage. Represents reaching light at an incident angle of 41.8 degrees. As sunlight passes through the atmosphere, part of the light is absorbed by ozone, water vapor, etc. in the atmosphere. Therefore, the amount of light is defined by the incident angle.

Embodiment 2. FIG.
FIG. 10 is a cross-sectional view showing a part of the configuration of the solar cell module 200 according to the second embodiment. The solar cell module 200 of the second embodiment is similar to that of the first embodiment, but the current collector electrode 6 on the rear surface side in the first embodiment is different from the bus rear surface current collector electrode 7b similar to the current collector electrode on the light receiving surface side. The difference is that the grid current collecting electrode 8 is provided, and the up-conversion type wavelength conversion layer 7R2 is provided between the back surface bus rear surface current collecting electrode 7b and the translucent electrode 5b. As in the case of the first embodiment, the wavelength conversion layer 7R1 is provided between the bus collector electrode 7a on the light receiving surface side and the translucent electrode 5a. The wavelength conversion layer 7R2 is also formed by a screen printing method or the like, similar to the light collecting surface side bus collector electrode 7a described in the first embodiment. Here, the wavelength conversion formed between the bus current collecting electrode 7a located on the light receiving surface side and formed between the bus current collecting electrode 7a and the translucent electrode 5a, formed in the vertical direction with respect to the substrate of the solar cell element 20. The layer 7R1 and the wavelength conversion layer 7R2 formed between the bus back surface collecting electrode 7b and the translucent electrode 5b located on the back surface side have the same coordinates with respect to the substrate direction. In addition, the grid current collection electrode 8 is formed also in the back surface side, and bears the electrical connection of the bus back surface current collection electrode 7b and the solar cell element 20. FIG. The wavelength conversion layer 7R2 is an up-conversion material that converts light having a wavelength longer than about 900 nm into light having a wavelength of about 400 to 900 nm, and compounds such as porphyrin and phthalocyanine as dyes having two-photon absorption characteristics, and fluorene-based light emission. It consists of polymers. As an example, it is known that a phosphor containing Tm ³⁺ and Yb ³⁺ absorbs light having a near infrared wavelength of about 1000 nm and emits light having a blue wavelength of about 400 to 500 nm. Further, a rare earth element such as _{Er Y 2 O 3, YAO 3} , YF 3 may be a sintered particles obtained by adding the like. Since the silicon-based solar cell element 20 transmits a relatively large amount of light having a wavelength of 1000 nm or more on the back surface side, it is desirable to convert light in these wavelength ranges into 400 to 700 nm that is easily absorbed by silicon. These up-conversion materials may be formed by screen printing or the like after being dispersed in a material such as a light-transmitting polymer such as an acrylic resin or a silicone resin and made into a solution using an appropriate solvent. Other parts are the same as those in the first embodiment, and the description thereof will be omitted.

In the solar cell module 200 according to the second embodiment, the light L ₁ incident on the solar cell element 20 without being blocked by the bus collector electrode 7 a out of the incident light from the light receiving surface side is received by the solar cell element 20. There is transmitted light L _2a that is not completely absorbed and is emitted to the outside of the solar cell element 20. A part of the transmitted light L _2a is reflected by the back film 11. The light L _3a which is a part of such reflected light is incident again from the back surface of the solar cell element 20. Such light L _3a is up-converted by the wavelength conversion layer 7R2 formed between the bus back surface collecting electrode 7b and the translucent electrode 5b, and then becomes part of the light L _4a as a solar cell. The light is incident again from the back surface of the element 20, and is efficiently photoelectrically converted because of the wavelength light with high spectral sensitivity of the solar cell element 20. As a result, the generated current can be increased as compared with the conventional structure, and the effect of increasing the power generation efficiency can be obtained.

On the other hand, in the solar cell module 200, there is transmitted light L _2b emitted to the outside of the solar cell element 20 out of the incident light L ₁ from the light receiving surface side. After a part of the light of the transmitted light L _2b is reflected by the back film 11, as in the light L _3b, is reflected as the light L _3c enters the bus back surface collector electrode 7b, further light L _3c Some of the light L _3d is up-converted by the wavelength conversion layer 7R2 formed between the bus back surface collecting electrode 7b and the translucent electrode 5b, and then part of the light L _4b. Thus, the light is incident again from the back surface of the solar cell element 20 and is efficiently photoelectrically converted because of the wavelength light with high spectral sensitivity of the solar cell element 20. As a result, the generated current can be increased as compared with the conventional structure, and the effect of increasing the power generation efficiency can be obtained.

  As described above, in this embodiment, in addition to the configuration of Embodiment 1, the wavelength conversion layer is provided on the back surface side of the solar cell element. Thus, the effect at the time of installing a wavelength conversion layer in the back surface side of a solar cell element is demonstrated. Of the light incident on the light receiving surface, the light that is not absorbed in the photoelectric conversion layer is emitted from the back surface of the solar cell element to the sealing resin or back film on the back surface side of the solar cell module, and partially reflected to the sun. Incident from the back surface of the battery element. A part of the incident light is converted into light having a high spectral sensitivity of the solar cell element of about 400 to 900 nm and scattered by the wavelength conversion layer formed on the back surface side of the solar cell element. Part of this scattered light is incident on the photoelectric conversion layer and is efficiently photoelectrically converted due to the wavelength light with high spectral sensitivity of the solar cell element, so that the generated current can be increased compared to the conventional structure, The effect of increasing the power generation efficiency can be obtained.

  In addition, the solar cell element 20 in this Embodiment 2 may be a diffused solar cell element in addition to the heterojunction solar cell element. In general, since the heterojunction solar cell element and the diffusion solar cell element both have low current conversion efficiency in the infrared light region, the effect of the wavelength conversion layer 7R2 is that the heterojunction solar cell element and the diffusion solar cell element. Any of these can be obtained equally.

  In addition, here, the back film is configured to have reflectivity or scattering, but if a scattering surface is formed between the back film as the back surface side protection member and the solar cell element (cell), Light transmitted to the back side of the battery element 20 can be guided again to the solar cell element 20 by scattering.

Embodiment 3 FIG.
FIG. 11 is a cross-sectional view showing a part of the configuration of the solar cell module 300 according to the third embodiment. The solar cell module 300 of the third embodiment is similar to the second embodiment, but in the second embodiment, the bus current collector formed on the light receiving surface side formed in the vertical direction with respect to the substrate of the solar cell element 20. It was formed between the electrode 7a, the wavelength conversion layer 7R1 formed between the bus collector electrode 7a and the translucent electrode 5a, and the bus back collector electrode 7b and the translucent electrode 5b located on the back side. There is a difference in that the coordinates with respect to the substrate direction are different between the wavelength conversion layer 7R2. Other parts are the same as those in the second embodiment, and the description thereof will be omitted.

Below, the effect of Embodiment 3 is demonstrated. Both the structure of FIG. 10 as shown in the second embodiment and FIG. 11 of the third embodiment are incident on the solar cell element 20 without being blocked by the collector electrode 7a on the light receiving side of the solar cell element 20. Of the light L ₁ , the light reaching the interface between the translucent electrode 5b of the solar cell element 20 and the sealing resin 9 or the interface between the translucent electrode 5b of the solar cell element 20 and the wavelength conversion layer 7R2 The light that exists and reaches the interface between the translucent electrode 5b of the solar cell element 20 and the sealing resin 9 in the light L _{1 is} the light L _2a and L _2b in both FIG. 10 and FIG.

Moreover, as light reaching the interface between the translucent electrode 5b of the solar cell element 20 and the wavelength conversion layer 7R2, as shown in FIG. 11 in the solar cell module 300, the incident light L ₁ from the light receiving surface side is included. There is light L ₅ that is not emitted to the outside of the solar cell element 20 and is incident on the wavelength conversion layer 7R2 formed between the bus back surface collecting electrode 7b and the translucent electrode 5b. The light L ₅ is up-converted in the wavelength conversion layer 7R2, and a part of the light re-enters the photoelectric conversion layer of the solar cell element 20 like the light L _{6 and} is due to the wavelength light with high spectral sensitivity of the solar cell element. Thus, photoelectric conversion is efficiently performed. As a result, the generated current can be increased as compared with the conventional structure, and the effect of increasing the power generation efficiency can be obtained.

The light L ₅ described above is constituted by scattered light inside the solar cell element 20 and straight light incident on the solar cell module 300 from the vertical direction. The straight light incident on the solar cell module 300 from the vertical direction is formed in the vertical direction with respect to the substrate of the solar cell element 20, the bus current collecting electrode 7 a located on the light receiving surface side, and the bus current collecting electrode 7 a A wavelength conversion layer 7R1 formed between the translucent electrode 5a and a wavelength conversion layer 7R2 formed between the bus rear surface collecting electrode 7b and the translucent electrode 5b located on the rear surface side with respect to the substrate direction. This happens because the coordinates are different.

Of one, even in the solar cell module 200 according to the second embodiment, without being released to the outside of the solar cell element 20 of the incident light L ₁ from the light-receiving surface side, and the bus collecting electrode 7b and the translucent electrode 5b Although light L ₅ incident on the wavelength conversion layer 7R2 formed between the two is present, it is composed of scattered light inside the solar cell element 20, and is incident on the solar cell module 200 from the vertical direction. Few things are composed of. This is because, in the solar cell module 200, the bus collector electrode 7a, the bus collector electrode 7a, and the translucent electrode 5a, which are formed in the vertical direction with respect to the substrate of the solar cell element 20 and located on the light receiving surface side. Since the wavelength conversion layer 7R1 formed therebetween and the wavelength conversion layer 7R2 formed between the bus back surface collecting electrode 7b and the translucent electrode 5b located on the back surface side have the same coordinates with respect to the substrate direction. It is.

Therefore, the structure of the solar cell module 300 of the third embodiment has a larger amount of light L _{5 than} the structure of the solar cell module 200 of the second embodiment. In the solar cell module 200 according to the second embodiment and the solar cell module 300 according to the third embodiment, the light L ₁ incident on the solar cell element 20 without being blocked by the light collecting side bus collector electrode 7 a of the solar cell element 20. Among them, the total amount of light reaching the interface between the translucent electrode 5b of the solar cell element 20 and the sealing resin 9 or the interface between the translucent electrode 5b of the solar cell element 20 and the wavelength conversion layer 7R2 is the same. However, a part of the light reaching the interface between the translucent electrode 5b and the sealing resin 9 of the solar cell element 20 is wavelength-converted as light _L4a or light _L4b. A part of the light such as the light L _2a and the light L _2b re-entering the photoelectric conversion layer is absorbed by the sealing resin 9 outside the solar cell element 20. In contrast, among the light reaching the interface between the translucent electrode 5b and the wavelength conversion layer 7R2 of the solar cell element 20, the part light, photoelectric conversion layer is wavelength-converted as light L ₆ in Since the light such as the light L _{5 that} is incident again is not emitted to the outside of the solar cell element 20, it is not absorbed by the sealing resin 9 or the like outside the solar cell element 20. Therefore, the structure of the solar cell module 300 according to the third embodiment increases the amount of light that undergoes wavelength conversion compared to the structure of the solar cell module 200 according to the second embodiment, so that an increase in generated current can be expected.

  Therefore, in the structure in which most of the irradiation light from the light receiving surface side is incident on the solar cell module from the vertical direction, and there is a wavelength conversion material between the current collecting electrode on the back surface and the substrate. In the power generation, it is desirable that the structure is such that all or part of the bus electrode on the back surface exists at a position different from the diametrically opposite side of the collector electrode on the light receiving surface side with respect to the substrate. Since the structure of Embodiment 3 is a structure that satisfies this, an increase in generated current is expected as compared with Embodiment 2.

  In the third embodiment, a portion that does not intersect with the grid current collecting electrode is shown. However, the grid current collecting electrode may intersect with the bus current collecting electrode and may not be in contact with the bus current collecting electrode. In other words, if the wavelength conversion layer can be made conductive by a method such as forming the base layer of the wavelength conversion layer with a conductive resin or mixing conductive particles, the grid collector electrode is placed on the bus collector electrode. It is not necessary to cross and contact the bus collector electrode.

  Also in the third embodiment, the conductivity of the wavelength conversion layer 7R is not pursued, the grid current collecting electrode is crossed on the bus current collecting electrode, and is brought into contact with the bus current collecting electrode via the grid current collecting electrode. You may make it connect a translucent electrode and a bus current collection electrode.

  In the first to third embodiments, examples of forming a downshift wavelength conversion layer have been described. In the second and third embodiments, the example in which the wavelength conversion layer for up-conversion is formed on the back surface side has been described. In such a case, a down-conversion wavelength conversion layer may be provided instead of the down-shift wavelength conversion layer. That is, instead of a downshift wavelength conversion layer that converts the energy of one high-energy photon into one energy photon that is effective for photoelectric conversion, the energy of one high-energy photon is effective for photoelectric conversion. Changes such as conversion to a plurality of energy photons and a wavelength conversion layer for down conversion are also possible.

  In the first to third embodiments, the wavelength conversion layer 7R is not responsible for electrical connection, but the translucent electrodes 5a, 5b and the bus current collector electrode 7a are connected via the grid current collector electrode 8. However, if the wavelength conversion layer 7R can be made conductive, the grid current collecting electrode 8 is crossed on the bus current collecting electrode 7a (bus rear surface current collecting electrode 7b), and the bus current collecting electrode 7a ( It does not have to be in contact with the bus rear surface collecting electrode 7b). Examples of a method for imparting conductivity to the wavelength conversion layer 7R include a method in which the base layer of the wavelength conversion layer 7R is made of a conductive resin, or conductive particles are mixed. In this case, the grid current collecting electrode 8 can be formed in the same process as the bus current collecting electrode 7a (bus back surface current collecting electrode 7b). When the grid current collecting electrode 8 and the bus current collecting electrode 7a (bus back surface current collecting electrode 7b) are formed in the same process, the wavelength conversion layer 7R may also be formed under the grid current collecting electrode 7a.

  Further, the configuration of the solar cell is not limited to the heterojunction solar cell in any of the first to third embodiments, and can be appropriately selected from a diffusion solar cell and the like.

  Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  As described above, the solar cell element and the solar cell module according to the present invention are useful for improving the conversion efficiency, and are particularly suitable for increasing the efficiency of a thin solar cell module.

1 n-type single crystal silicon substrate, 2a, 2b i-type amorphous silicon layer, 3p-type amorphous silicon layer, 4n-type amorphous silicon layer, 5a, 5b translucent electrode, 6 collector electrode, 7a bus collector electrode, 7b bus back collector electrode, 7B base resin, R wavelength conversion material particles, 7R, 7R1, 7R2 wavelength conversion layer, 8 grid current collector electrode, 9 sealing resin, 10 glass plate, 11 back Film, light incident on the L ₀₁ light receiving surface, light incident on the wavelength converting layer on the L ₀₂ light receiving surface, light incident on the photoelectric conversion layer through the wavelength converting layer on the L ₀₃ light receiving surface, and light incident on the back surfaces of L _2a and L _2b Transmitted light, light reflected by L _3a , L _3b , L _3d back film, light reflected by L _3C bus back surface collecting electrode, reflected by L _4a , L _4b back film, back surface of solar cell element light to more re-enters the photoelectric conversion layer, L ₅ backside wavelength conversion layer and the back surface translucent conductive Light entering electrode and the light reaching the interface, is wavelength-converted by the L ₆ backside wavelength conversion layer into the light conversion layer side from the back of, 20 solar cell elements, 30 lead, 40 interconnector, 100, 200, 300 solar cell module.

Claims (9)

A semiconductor layer constituting a photoelectric conversion unit;
First and second current collecting electrodes sandwiching the semiconductor layer;
There between the first collector electrode formed on the light receiving surface side of the first and second collector electrode and the semiconductor layer, provided only directly under the first collector electrode A solar cell element having a wavelength conversion layer.   The first and second current collecting electrodes are provided on the first and second surfaces facing each other of the semiconductor layer, and the wavelength conversion layer is formed by both the first and second current collecting electrodes. The solar cell element according to claim 1, which is provided between the current collecting electrode and the semiconductor layer. Before Symbol the wavelength conversion layer provided directly below the first collecting electrode, the solar cell element according to claim 1 or 2 which is a wavelength conversion layer of the wavelength conversion layer or down-conversion of the down-shifting. One of the first and second collector electrodes, the wavelength conversion layer provided immediately below the second collector electrode formed on the back surface side, according to claim 2 which is a wavelength conversion layer of up-conversion The solar cell element according to. Before SL first collector electrode is formed of a plurality of grid electrodes, the bus electrodes orthogonal to said grid electrode,
The wavelength conversion layer is provided between the bus electrode and the semiconductor layer,
5. The solar cell element according to claim 1, wherein the grid electrode intersects with the bus electrode on the bus electrode. 6.   The solar cell element according to claim 5, wherein the wavelength conversion layer and the bus electrode are formed of a thick printed layer.   The solar cell element according to claim 5, wherein the wavelength conversion layer and the bus electrode are configured by a sheet layer having a two-layer structure. Before SL first collector electrode, the solar cell device according to any one of claims 2 to 7 in opposite positions the second collector electrode on the back side are arranged to present. The solar cell element according to any one of claims 1 to 8,
A light-receiving surface side protective member covering the light-receiving surface of the solar cell element;
The solar cell module which fixed between the back surface side protection members which cover the surface opposite to the light-receiving surface of the said solar cell element with sealing resin.

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