JP2011040796A - Photoelectric conversion device, and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion device and a production method therefor which can improve the optical absorption characteristics of a power-generating layer by controlling and optimizing the three-dimensional structure of a rear-face electrode layer. <P>SOLUTION: The photoelectric conversion device includes a transparent electrode layer 2, at least two power generating layers 91 and 92, and a rear-surface electrode layer 4 on a substrate 1. In the photoelectric conversion device, the rear-surface electrode layer 4 has a silver film, and the surface of the rear-surface electrode layer 4 on the side of the substrate 1 has a concavo-convex shape. When the sum of the amount of the light reflected on the surface of the rear-surface electrode layer 4 and the amount of the light absorbed by the rear-surface electrode layer 4 is 96% or lower of the sum of the amount of the light reflected on the surface of the rear-surface electrode layer 4 and the amount of the light absorbed by the rear-surface electrode layer 4 when the rear-surface electrode layer 4 is smooth. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion device and a manufacturing method thereof, and more particularly to a solar cell using silicon as a power generation layer.

  A solar cell is known as a photoelectric conversion device that receives light and converts it into electric power. Among solar cells, for example, a thin-film solar cell in which a thin-film silicon layer is stacked on a power generation layer (photoelectric conversion layer) is easy to increase in area and has a thickness of about 1/100 that of a crystalline solar cell. It has the advantages of being thin and requiring less material. For this reason, the thin film silicon solar cell can be manufactured at a lower cost than the crystalline solar cell. However, a disadvantage of the thin-film silicon solar cell is that the conversion efficiency is lower than that of the crystal system.

  In a thin film solar cell, various devices have been made to increase conversion efficiency, that is, output power. For example, a tandem solar cell has been proposed that obtains high power generation efficiency by efficiently absorbing incident light by stacking two photoelectric conversion cells having different absorption wavelength bands. In this case, long wavelength light having a wavelength of 500 nm to 1000 nm is absorbed in the crystalline silicon of the photoelectric conversion cell. However, since the absorption coefficient of crystalline silicon in the same wavelength region is small, the incident light is reflected in the solar cell. Therefore, it is necessary to increase the optical path length and increase the amount of light absorption in crystalline silicon. For this reason, in the super straight type in which sunlight enters from the transparent substrate side, improvement of the back electrode structure on the side opposite to the light incident side with respect to the power generation layer has been studied.

  In Patent Document 1, as a back electrode structure, a back electrode is formed of a metal exhibiting a high reflectance with respect to light in the wavelength range of sunlight radiation spectrum, and a transparent conductive layer is formed between the back electrode and the silicon semiconductor layer. It is disclosed. By forming the transparent conductive layer, it is possible to prevent the back electrode material and the silicon thin film from being alloyed, maintain the high reflectivity of the back electrode, and prevent the conversion efficiency from being lowered.

  In Patent Document 2, electromagnetic analysis by FDTD (Finite Difference Time Domain) method is performed, and the optimal structure of the back electrode is a lower refractive index than the transparent conductive layer between the back electrode layer and the transparent conductive layer. A structure in which a refractive index adjusting layer is inserted is disclosed. By inserting the refractive index adjusting layer, the reflected light intensity in the back electrode structure can be improved. As a result, the amount of light absorption in the power generation layer can be increased to increase the short-circuit current.

Japanese Patent Publication No. 60-41878 JP 2006-120737 A

  In a thin film solar cell, the surface of the back electrode layer usually has a shape that follows the surface shape of the transparent electrode layer formed on the substrate. That is, since the surface of the formed transparent electrode layer has a concavo-convex shape, the layer structure laminated on the transparent electrode layer is also affected by the concavo-convex shape on the surface of the transparent electrode layer, and the surface of the back electrode layer on the substrate side Is also uneven. When the surface of the back electrode on the substrate side is uneven, incident light from the substrate side is scattered on the surface of the back electrode layer on the substrate side, and the scattered light is absorbed by the power generation layer. Therefore, in order to increase the reflectance on the surface of the back electrode layer and improve the light absorption amount in the power generation layer, just by optimizing the material and layer structure of the back electrode layer, as in Patent Document 1 and Patent Document 2. Insufficient, it was necessary to consider the shape of the back electrode surface.

  As described above, since the surface of the back electrode layer has a shape that follows the surface shape of the transparent electrode layer, conventionally, the battery performance has been evaluated by controlling the three-dimensional structure of the transparent electrode layer. However, in order to further increase the interference effect in the power generation layer with the back electrode layer as an end point, it is necessary to control the surface shape of the back electrode layer itself.

  The present invention provides a photoelectric conversion device in which the light absorption characteristics of the power generation layer are improved by controlling and optimizing the surface shape of the back electrode layer, and a method for manufacturing the photoelectric conversion device.

  In order to increase the interference effect in the power generation layer with the back electrode layer as an end point, an uneven shape is provided on the surface of the back electrode layer on the substrate side, and the height difference between the concave portion and the convex portion is increased. Generally, a silver thin film with excellent light reflectivity in the incident light wavelength region is used as the back electrode layer. However, when a silver thin film is formed as the back electrode layer, light absorption by the surface plasmon caused by the uneven shape Will occur. Light absorption by the surface plasmon increases as the height difference between the concave and convex portions increases. The present inventors have found a back surface structure in which the light absorption characteristics in the power generation layer are optimum in consideration of the interference effect and the light absorption by the surface plasmon. In the present invention, the “back electrode layer” refers to a layer made of metal. The “back surface structure” refers to the entire structure on the opposite side of the power generation layer from the substrate, and includes the entire plurality of layers including the back electrode layer, the layer configuration, and the surface shape.

  That is, a photoelectric conversion device as a reference example of the present invention is a photoelectric conversion device including a transparent electrode layer, at least two power generation layers, and a back electrode layer on a substrate, and the back electrode layer is a silver thin film. And the substrate-side surface of the back electrode layer has a concavo-convex shape, and a height difference between the concave and convex portions of the concavo-convex shape is 60 nm or more and 210 nm or less.

  As described above, the substrate-side surface of the back electrode layer including the silver thin film has a back surface structure in which the height difference between the concave portion and the convex portion is 60 nm or more and 210 nm or less, thereby providing an interference effect and the back surface. Since the influence of light loss due to surface plasmons in the electrode layer can be suppressed, the amount of light absorption in the power generation layer on the back electrode side can be increased. As a result, the power generation efficiency of the photoelectric conversion device can be improved.

  The photoelectric conversion device of the present invention is a photoelectric conversion device comprising a transparent electrode layer, at least two power generation layers, and a back electrode layer on a substrate, wherein the back electrode layer comprises a silver thin film, and the back electrode layer The surface of the substrate side of the substrate has a concavo-convex shape, the amount of reflected light reflected from the substrate side surface of the back electrode layer and emitted from the substrate, and the amount of light absorbed by the back electrode layer The sum of the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer when the back electrode layer is smooth It is 96% or less of the sum.

  As described above, as a result of considering the interference effect and the light absorption by the surface plasmon, the surface on the substrate side of the back electrode layer including the silver thin film has an uneven shape, and is reflected from the surface of the back electrode layer and reflected from the substrate. The sum of the amount of light and the amount of light absorbed by the back electrode layer comprising the silver thin film is the sum of the amount of reflected light emitted from the substrate and the light absorbed by the back electrode layer when the back electrode layer is smooth. By using a back surface structure that is 96% or less of the sum of the light amount, the amount of light absorption in the power generation layer on the back electrode layer side can be increased. As a result, a photoelectric conversion device that exhibits high power generation efficiency can be obtained. More preferably, the sum of the amount of reflected light and the amount of light absorbed by the back electrode layer is the sum of the amount of reflected light when the back electrode is smooth and the amount of light absorbed by the back electrode layer. If it is 93% or less, the light absorption amount in the power generation layer can be greatly increased.

  The photoelectric conversion device of the present invention is a photoelectric conversion device comprising a transparent electrode layer, at least two power generation layers, and a back electrode layer on a substrate, wherein the back electrode layer comprises a silver thin film, and the back surface When the substrate side surface of the electrode layer has an uneven shape, and the amount of reflected light reflected from the substrate side surface of the back electrode layer and emitted from the substrate is smooth in the back electrode layer It is 93% or less of the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate.

  As described above, as a result of considering the interference effect and the light absorption by the surface plasmon, the surface on the substrate side of the back electrode layer including the silver thin film has an uneven shape, and is reflected from the surface of the back electrode layer and reflected from the substrate. By using a back surface structure in which the amount of light is 93% or less of the amount of reflected light emitted from the substrate when the back electrode layer is smooth, the light absorption amount in the power generation layer on the back electrode layer side is increased. be able to. As a result, a photoelectric conversion device that exhibits high power generation efficiency can be obtained. More preferably, when the amount of reflected light is 90% or less of the amount of reflected light when the back electrode is smooth, the amount of light absorbed by the power generation layer can be significantly increased.

  In the said invention, it is preferable that the haze rate of the laminated body of the said board | substrate and the said transparent electrode layer is 20% or more and 30% or less.

  In the above invention, the power generation layer on the back electrode layer side preferably has a thickness of 1.45 μm to 2.5 μm. When the film thickness of the power generation layer on the back electrode layer side is within the above range, a sufficient amount of light absorption in the power generation layer can be obtained, and the power generation efficiency can be improved.

  In the above invention, it is preferable that a back transparent electrode layer is further provided on a surface of the back electrode layer on the substrate side. In this way, by forming the transparent back electrode layer between the back electrode layer and the power generation layer, the contact resistance between the back electrode layer and the power generation layer is reduced, and the amount of reflected light is increased. The power generation efficiency of the converter can be improved.

  A method for manufacturing a photoelectric conversion device as a reference example of the present invention includes a step of forming a transparent electrode layer on a substrate, a step of forming at least two power generation layers, and a step of forming a back electrode layer. A method for manufacturing an apparatus, wherein the back electrode layer includes a silver thin film, and a concave-convex shape having a height difference between a concave portion and a convex portion of 60 nm to 210 nm is provided on a surface of the back electrode layer on the substrate side. Features.

  As described above, as a result of considering the interference effect and the light absorption by the surface plasmon, a back electrode layer having a silver thin film is formed, and the height difference between the concave portion and the convex portion is 60 nm or more on the substrate side surface of the back electrode layer. By providing a concavo-convex shape of 210 nm or less, a photoelectric conversion device having a large light absorption amount in the power generation layer and high power generation efficiency can be manufactured.

  The method for producing a photoelectric conversion device of the present invention includes a step of forming a transparent electrode layer on a substrate, a step of forming at least two power generation layers, and a step of forming a back electrode layer. The back electrode layer comprises a silver thin film, the amount of reflected light reflected from the substrate side surface of the back electrode layer and emitted from the substrate, and the amount of light absorbed by the back electrode layer; When the back electrode layer is smooth, the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer An uneven shape is provided on the surface of the back electrode layer on the substrate side so as to be 96% or less of the sum of the above.

  As described above, as a result of considering the interference effect and light absorption by the surface plasmon, the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer Is 96% or less, more preferably 93% or less of the sum of the amount of reflected light emitted from the substrate and the amount of light absorbed by the back electrode layer when the back electrode layer is smooth. In addition, if a concave-convex shape is provided on the substrate-side surface of the back electrode layer including the silver thin film, a photoelectric conversion device having a large light absorption amount of the power generation layer and high power generation efficiency can be manufactured.

  Moreover, the manufacturing method of the photoelectric conversion device of the present invention includes a step of forming a transparent electrode layer on a substrate, a step of forming at least two power generation layers, and a step of forming a back electrode layer. In the manufacturing method, the back electrode layer includes a silver thin film, and the amount of reflected light that is reflected from the substrate-side surface of the back electrode layer and emitted from the substrate is smooth. Providing a concave-convex shape on the substrate-side surface of the back electrode layer so that it is 93% or less of the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate. Features.

  Thus, as a result of considering the interference effect and the light absorption by the surface plasmon, the amount of the reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate is the substrate when the back electrode layer is smooth If the concave-convex shape is provided on the substrate side surface of the back electrode layer including the silver thin film so that the amount of reflected light emitted from the substrate is 93% or less, more preferably 90% or less, the light absorption amount of the power generation layer is increased. A photoelectric conversion device that exhibits large and high power generation efficiency can be manufactured.

  In the above invention, the uneven shape is controlled by controlling the formation conditions of the power generation layer on the back electrode layer side, and after providing a predetermined uneven shape on the surface of the power generation layer on the back electrode layer side, It can be provided by forming a back electrode layer.

  In this way, if the back electrode layer is formed after providing a predetermined uneven shape on the surface on the back electrode side of the power generation layer by controlling the formation conditions of the power generation layer, the uneven shape on the surface of the back electrode layer on the substrate side can be changed. It can be easily controlled.

  Further, the power generation layer on the back electrode layer side is formed with the uneven shape, the surface of the power generation layer is etched to form a predetermined uneven shape on the surface of the power generation layer, and then the back electrode is formed. Can be provided.

  In this way, the surface of the power generation layer on the back electrode layer side is etched into a predetermined uneven shape, and then the back electrode layer is formed to easily control the uneven shape on the substrate side surface of the back electrode layer. Can be provided.

  In the said invention, it is preferable that the haze rate of the laminated body of the said board | substrate and the said transparent electrode layer is 20% or more and 30% or less.

  In the above invention, the power generation layer on the back electrode layer side preferably has a thickness of 1.45 μm to 2.5 μm. If the power generation layer on the back electrode layer side is formed with a film thickness within the above range, a photoelectric conversion device exhibiting high power generation efficiency can be obtained.

  In the above invention, it is preferable to further provide a back transparent electrode layer on the surface of the back electrode layer on the substrate side. By providing the back transparent electrode layer between the back electrode layer and the power generation layer, the contact resistance between the back electrode layer and the power generation layer can be reduced and the amount of reflected light can be increased.

  According to the reference example of the present invention, the power generation on the back electrode layer side is provided by providing the surface on the substrate side of the back electrode layer including the silver thin film with a concavo-convex shape having a height difference between the recesses and the protrusions of 60 nm to 210 nm. The power generation efficiency of the photoelectric conversion device can be improved by increasing the amount of light absorption in the layer.

  According to the present invention, when the back electrode layer is smooth, the sum of the amount of reflected light reflected from the substrate side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer An uneven shape is provided on the substrate-side surface of the back electrode layer made of a silver thin film so that the sum of the amount of reflected light emitted from the substrate and the amount of light absorbed by the back electrode layer is 96% or less. Thus, the amount of light absorption in the power generation layer can be increased, and the power generation efficiency of the photoelectric conversion device can be improved.

  Further, the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate is 93% or less of the amount of reflected light emitted from the substrate when the back electrode layer is smooth, By providing an uneven shape on the substrate-side surface of the back electrode layer made of a silver thin film, the amount of light absorption in the power generation layer can be increased, and the power generation efficiency of the photoelectric conversion device can be improved.

  The uneven shape on the surface of the back electrode layer on the substrate side is obtained by etching the power generation layer surface by controlling the formation conditions of the power generation layer on the back electrode layer side or after forming the power generation layer on the back electrode layer side. Can be provided. If it does in this way, the back electrode layer which has the uneven | corrugated shape of a desired surface can be formed easily.

It is sectional drawing which showed typically the structure of the photoelectric conversion apparatus which concerns on one Embodiment of this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel as a photoelectric conversion apparatus which concerns on this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel as a photoelectric conversion apparatus which concerns on this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel as a photoelectric conversion apparatus which concerns on this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel as a photoelectric conversion apparatus which concerns on this invention. The cross-sectional schematic of the laminated structure of the tandem-type solar cell used for calculation by FDTD method is shown. It is a graph which shows the relationship between the sum of the light quantity of the reflected light in the tandem type solar cell of Example 1, and the silver absorbed light quantity, and the height difference h of uneven | corrugated shape. 4 is a graph showing the relationship between the amount of reflected light and the height difference h of the concavo-convex shape in the tandem solar cell of Example 1. 4 is a graph showing the relationship between the amount of light absorption in the second battery layer and the height difference of the concavo-convex structure in the tandem solar cell of Example 1. It is a graph which shows the relationship between the sum of the light quantity of the reflected light in the tandem-type solar cell of Example 2, and the silver absorption light quantity, and the height difference of an uneven structure. It is a graph which shows the relationship between the light quantity of the reflected light in the tandem-type solar cell of Example 2, and the height difference h of uneven | corrugated shape. 6 is a graph showing the relationship between the amount of light absorption in the second battery layer and the height difference of the concavo-convex structure in the tandem solar cell of Example 2. It is a graph which shows the relationship between the sum of the light quantity of the reflected light in the tandem type solar cell of Example 3, and the silver absorbed light quantity, and the height difference of an uneven structure. It is a graph which shows the relationship between the light quantity of the reflected light in the tandem type solar cell of Example 3, and the height difference h of uneven | corrugated shape. 6 is a graph showing the relationship between the amount of light absorption in the second battery layer and the height difference of the concavo-convex structure in the tandem solar cell of Example 3. It is a graph which shows the relationship between the sum of the light quantity of the reflected light in the tandem type solar cell of Example 4, and the silver absorbed light quantity, and the height difference of an uneven structure. It is a graph which shows the relationship between the light quantity of the reflected light in the tandem-type solar cell of Example 4, and the height difference h of uneven | corrugated shape. It is a graph which shows the relationship between the light absorption amount in the 2nd battery layer in the tandem-type solar cell of Example 4, and the height difference of an uneven structure.

A configuration of an embodiment of the photoelectric conversion device of the present invention will be described.
FIG. 1 is a schematic diagram illustrating a configuration of a photoelectric conversion apparatus according to the present embodiment. The photoelectric conversion device 100 is a silicon-based solar cell, and includes a first battery layer 91 (amorphous silicon system) and a second battery layer 92 (crystalline silicon system) as a substrate 1, a transparent electrode layer 2, and a power generation layer 3. And a back electrode layer 4. Here, the silicon-based is a generic name including silicon (Si), silicon carbide (SiC), and silicon germanium (SiGe). The crystalline silicon system means a silicon system other than the amorphous silicon system, and includes a microcrystalline silicon and a polycrystalline silicon system.

  Next, as a photoelectric conversion device of this embodiment, a process for manufacturing a solar cell panel will be described with reference to FIGS.

(1) FIG. 2 (a)
As the substrate 1, a soda float glass substrate (for example, 1.4 m × 1.1 m × plate thickness: a large area substrate having a side of 3 to 6 mm exceeding 1 m) is used. The end face of the substrate is preferably subjected to corner chamfering or R chamfering to prevent damage due to thermal stress or impact.

(2) FIG. 2 (b)
As the transparent electrode layer 2, a transparent electrode film having a thickness of about 500 nm to 800 nm and having tin oxide (SnO ₂ ) as a main component is formed at about 500 ° C. with a thermal CVD apparatus. At this time, a texture with appropriate irregularities is formed on the surface of the transparent electrode film. In the present embodiment, the haze ratio of the laminate of the substrate and the transparent electrode layer is preferably 20% or more and 30% or less. As the transparent electrode layer 2, an alkali barrier film (not shown) may be formed between the substrate 1 and the transparent electrode film in addition to the transparent electrode film. As the alkali barrier film, a silicon oxide film (SiO ₂ ) having a thickness of 50 nm or more and 150 nm or less is formed at about 500 ° C. using a thermal CVD apparatus.

(3) FIG. 2 (c)
Thereafter, the substrate 1 is placed on an XY table, and the first harmonic (1064 nm) of the YAG laser is incident from the layer surface side of the transparent electrode layer as indicated by the arrow in the figure. The laser power is adjusted so that the processing speed is appropriate, and the substrate 10 and the laser beam are moved relative to each other in the direction perpendicular to the series connection direction of the power generation cells so that the groove 10 is formed. And laser etching into a strip shape having a predetermined width of about 6 mm to 15 mm.

(4) FIG. 2 (d)
As the first battery layer 91, a p layer, an i layer, and an n layer made of an amorphous silicon thin film are formed by a plasma CVD apparatus. Using SiH ₄ gas and H ₂ gas as main raw materials, the amorphous silicon p layer 31 from the side on which sunlight is incident on the transparent electrode layer 2 at a reduced pressure atmosphere: 30 Pa to 1000 Pa and a substrate temperature: about 200 ° C. Then, an amorphous silicon i layer 32 and an amorphous silicon n layer 33 are formed in this order. The amorphous silicon p layer 31 is an amorphous B-doped silicon film and has a thickness of 10 nm to 30 nm. The amorphous silicon i layer 32 has a thickness of 200 nm to 350 nm. The amorphous silicon n layer 33 is a P-doped amorphous silicon film and has a thickness of 30 nm to 50 nm. A buffer layer may be provided between the amorphous silicon p layer 31 and the amorphous silicon i layer 32 in order to improve interface characteristics.

  On the 1st battery layer 91, the p layer, i layer, and n layer which consist of a crystalline silicon thin film as the 2nd battery layer 92 are formed into a film with a plasma CVD apparatus. The crystalline silicon p layer 41 is a B-doped crystalline silicon film having a thickness of 10 nm to 50 nm. The film thickness of the crystalline silicon i layer 42 is 1.2 μm or more and 3.0 μm or less. The crystalline silicon n layer 43 is a P-doped crystalline silicon film having a thickness of 20 nm to 50 nm.

In the present embodiment, by controlling the formation conditions of the second battery layer 92 (p layer 41, i layer 42, and n layer 43), a desired surface of the crystalline silicon n layer 43 on the back electrode layer 4 side is formed. An uneven shape is provided. Examples of conditions for forming the second battery layer 92 include a substrate temperature during film formation, a film formation pressure, a hydrogen dilution rate, plasma excitation power, and a plasma generation frequency. For example, using SiH ₄ gas and H ₂ gas as main raw materials, a reduced pressure atmosphere: 3000 Pa or less, a substrate temperature: 25 ° C. or more and 250 ° C. or less, a plasma generation frequency: 40 MHz or more and 100 MHz or less, a crystalline silicon p layer 41, a crystal The crystalline silicon i layer 42 and the crystalline silicon n layer 43 are formed in this order.

  The uneven shape of the surface of the crystalline silicon n layer 43 on the back electrode layer 4 side may be provided by etching the surface of the crystalline silicon n layer 43 after forming the second battery layer 92. In this case, an etching process using hydrogen plasma or hydrogen plasma to which methane, chlorofluorocarbon, or the like is added can be employed.

  In the present embodiment, the intermediate contact layer 5 serving as a semi-reflective film is formed on the first battery layer 91 in order to improve the contact between the first battery layer 91 and the second battery layer 92 and to achieve current matching. You may do it. As the intermediate contact layer 5, a target: Ga-doped ZnO sintered body is used to form a GZO (Ga-doped ZnO) film having a film thickness of 20 nm or more and 100 nm or less using a DC sputtering apparatus.

(5) FIG. 2 (e)
The substrate 1 is placed on an XY table, and the second harmonic (532 nm) of the laser diode-pumped YAG laser is incident from the film surface side of the photoelectric conversion layer 3 as indicated by an arrow in the figure. Pulse oscillation: Laser power is adjusted so as to be suitable for the processing speed from 10 kHz to 20 kHz, and laser etching is performed so that the groove 11 is formed on the lateral side of the laser etching line of the transparent electrode layer 2 from about 100 μm to 150 μm. To do. The laser may be incident from the substrate 1 side. In this case, since a high vapor pressure generated by the energy absorbed by the first battery layer 91 of the photoelectric conversion layer 3 can be used, further stable laser etching processing can be performed. The position of the laser etching line is selected in consideration of positioning tolerances so as not to intersect with the etching line in the previous process.

(6) FIG. 3 (a)
As the back electrode layer 4, an Ag film is formed by a sputtering apparatus at a reduced pressure atmosphere and a film forming temperature of about 150 ° C. Alternatively, as the back electrode layer 4, an Ag film: 200 to 500 nm and a Ti film having a high anticorrosion effect as a protective film: 10 to 20 nm may be laminated in order to form a laminated film of an Ag film / Ti film. good. In this case, the layer structure is such that an Ag film is provided on the substrate side.

  In the present embodiment, for the purpose of reducing the contact resistance between the n layer of the second battery layer 92 and the back electrode layer 4 and improving the light reflection, the back transparent electrode layer (see FIG. The back surface structure may be formed with a not shown in FIG. As the back transparent electrode layer, for example, a GZO (Ga-doped ZnO) film is formed with a film thickness of 50 nm to 100 nm by a sputtering apparatus.

  The back electrode layer is formed following the crystalline silicon n layer. Further, when the back transparent electrode layer is provided, the back transparent electrode layer is thin, and therefore the back transparent electrode layer and the back electrode layer are formed following the crystalline silicon n layer. Therefore, the surface shape of the back electrode layer on the substrate side is substantially the same as the surface shape of the crystalline silicon n layer.

  In the present embodiment, the unevenness shape of the substrate-side surface of the back electrode layer 4 is such that the height difference between the recesses and the protrusions is 60 nm or more and 210 nm or less.

  In the present embodiment, the amount of reflected light reflected from the substrate-side surface of the back electrode layer 4 and emitted from the substrate 2 to the outside of the solar cell and the back electrode layer 4 when sunlight is incident from the substrate 1 side. The sum of the amount of light absorbed by the light source and the back electrode layer 4 is the difference between the amount of reflected light and the back electrode layer 4 when the height difference is 0 nm (that is, when the surface of the back electrode layer 4 on the substrate 2 side is smooth). The concave-convex shape on the substrate-side surface of the back electrode layer 4 is provided so as to be 96% or less, more preferably 93% or less of the sum of the amount of absorbed light.

  Further, in the present embodiment, when sunlight is incident from the substrate 1 side, the amount of reflected light reflected from the substrate-side surface of the back electrode layer 4 and emitted from the substrate 2 to the outside of the solar cell has an elevation difference. The substrate side of the back electrode layer 4 is set to 93% or less, more preferably 90% or less of the amount of reflected light with 0 nm (when the surface of the back electrode layer 4 on the substrate 2 side is smooth) as a reference. An uneven shape on the surface is provided.

(7) FIG. 3 (b)
The substrate 1 is placed on an XY table, and the second harmonic (532 nm) of the laser diode-pumped YAG laser is incident from the substrate 1 side as shown by the arrow in the figure. The laser light is absorbed by the photoelectric conversion layer 3, and the back electrode layer 4 is exploded and removed using the high gas vapor pressure generated at this time. Pulse oscillation: 1 kHz to 10 kHz Laser power is adjusted so as to be suitable for processing speed, and laser etching is performed so that grooves 12 are formed on the lateral side of the laser etching line of the transparent electrode layer 2 from about 250 μm to 400 μm. To do.

(8) FIG. 3 (c)
The power generation region is divided to eliminate the influence that the serial connection portion due to laser etching is likely to be short-circuited at the film edge around the substrate edge. The substrate 1 is placed on an XY table, and the second harmonic (532 nm) of the laser diode pumped YAG laser is incident from the substrate 1 side. Laser light is absorbed by the transparent electrode layer 2 and the photoelectric conversion layer 3, and the back electrode layer 4 explodes using the high gas vapor pressure generated at this time, and the back electrode layer 4 / photoelectric conversion layer 3 / transparent electrode Layer 2 is removed. Pulse oscillation: 1 kHz or more and 10 kHz or less, the laser power is adjusted so as to be suitable for the processing speed, and the position of 5 mm to 20 mm from the end of the substrate 1 is placed in the X-direction insulating groove as shown in FIG. Laser etching is performed to form 15. At this time, the Y-direction insulating groove does not need to be provided because the film surface polishing removal process in the peripheral region of the substrate 1 is performed in a later step.

  The insulating groove 15 has an effective effect in suppressing the intrusion of external moisture into the solar cell module 6 from the end of the solar cell panel by terminating the etching at a position of 5 mm to 10 mm from the end of the substrate 1. Therefore, it is preferable.

  In addition, although the laser beam in the above process is made into a YAG laser, there exists what can use a YVO4 laser, a fiber laser, etc. similarly.

(9) FIG. 4 (a)
In order to secure a sound adhesion / seal surface with the back sheet 24 via EVA or the like in a later process, the laminated film around the substrate 1 (peripheral region 14) has a step and is easy to peel off. Remove. 3 mm from the end of the substrate 1 over the entire circumference of the substrate 1, the X direction is closer to the substrate end than the insulating groove 15 provided in the above-described step of FIG. 3C, and the Y direction is a groove near the substrate end side. The back electrode layer 4 / photoelectric conversion layer 3 / transparent electrode layer 2 is removed using grinding stone polishing, blast polishing, or the like on the substrate end side with respect to 10. Polishing debris and abrasive grains are removed by cleaning the substrate 1.

(10) FIG. 4 (b)
At the terminal box mounting portion, an opening through window is provided in the back sheet 24 and the current collector plate is taken out. A plurality of layers of insulating materials are installed in the opening through window portion to suppress intrusion of moisture and the like from the outside.

  It processes so that electric power can be taken out from the terminal box part on the back side of a solar cell panel by collecting electricity using the copper foil from the solar cell power generation cell at one end and the solar cell generation cell at the other end arranged in series. In order to prevent a short circuit with each part, the copper foil arranges an insulating sheet wider than the copper foil width.

  After the current collecting copper foil or the like is disposed at a predetermined position, an adhesive filler sheet made of EVA (ethylene vinyl acetate copolymer) or the like is disposed so as to cover the entire solar cell module 6 and not protrude from the substrate 1. .

  A back sheet 24 having a high waterproof effect is installed on the EVA. In this embodiment, the back sheet 24 has a three-layer structure of PET sheet / AL foil / PET sheet so that the waterproof and moisture proof effect is high.

  The EVA sheet is placed in a predetermined position until the back sheet 24 is deaerated in a reduced pressure atmosphere by a laminator and pressed at about 150 ° C. to 160 ° C., and EVA is crosslinked and brought into close contact.

(11) FIG. 5 (a)
The terminal box 23 is attached to the back side of the solar cell module 6 with an adhesive.

(12) FIG. 5 (b)
The copper foil and the output cable of the terminal box 23 are connected with solder or the like, and the inside of the terminal box is filled with a sealing agent (potting agent) and sealed. Thus, the solar cell panel 50 is completed.

(13) FIG. 5 (c)
A power generation inspection and a predetermined performance test are performed on the solar cell panel 50 formed in the steps up to FIG. The power generation inspection is performed using a solar simulator of AM1.5 and solar radiation standard sunlight (1000 W / m ² ).

(14) FIG. 5 (d)
Before and after the power generation inspection (FIG. 5C), a predetermined performance inspection is performed including an appearance inspection.

Example 1
In FIG. 6, the schematic of the laminated structure model of the tandem solar cell of Example 1 is shown. In the stacked structure model of FIG. 6, the transparent electrode layer 2 is sequentially stacked on a glass substrate (not shown). The thickness of the glass substrate was semi-infinite.

  The transparent electrode layer 2 has a film thickness of 700 nm, a haze ratio of 20% when formed as a laminate of the substrate 1 and the transparent electrode layer 2, an average pitch (width for one cycle) of 600 nm, and an elevation angle (not shown in FIG. 6). The angle from the glass substrate surface shown in the figure was 30 °.

  In the first battery layer 91 made of amorphous silicon, a p-layer, an i-layer, and an n-layer were stacked in this order from the transparent electrode layer 2 side to have a film thickness of 250 nm. The intermediate contact layer 5 is a GZO film having a thickness of 70 nm. In the second battery layer 92 made of crystalline silicon, a p-layer, an i-layer, and an n-layer were stacked in this order from the first battery layer 91 side to a film thickness of 2.0 μm. Since the first battery layer 91 and the second battery layer 92 are provided on the transparent electrode layer 2, the boundary of each layer has an uneven texture similar to the transparent electrode layer 2, but generally compared with the texture of the transparent electrode layer 2. It becomes dull uneven shape. Therefore, in the structural model of FIG. 6, the uneven shape of the first battery layer 91 and the second battery layer 92 is expressed by a sine function.

  The back surface structure was the back surface transparent electrode layer 7 and the back surface electrode layer 4. The back transparent electrode layer 7 was a GZO film having a thickness of 60 nm. The back electrode layer 4 was an Ag film having a thickness of 250 nm or more. The uneven shape on the substrate side surface of the back transparent electrode layer 7 and the back electrode layer 4 is expressed by a sine function, and the height difference h of the uneven shape is in the range of 0 nm to 400 nm.

Using the FDTD method, optical analysis calculation of the laminated structure model of FIG. 6 was performed.
For the wavelength range of 300 nm to 1200 nm, which is the absorption wavelength band of amorphous silicon and crystalline silicon, the light absorptivity spectrum and the reflectance spectrum of each layer of the stacked structure model in FIG. 6 were obtained by calculation.
The equivalent current value obtained by integrating the product of the reflectance spectrum in the absorption wavelength band of crystalline silicon from 500 nm to 1000 nm and the reference solar spectrum AM1.5G is reflected on the surface of the back electrode layer 4 on the transparent electrode layer 2 side. The amount of reflected light emitted from the transparent electrode layer 2 was defined.
An equivalent current value obtained by integrating the product of the light absorptivity spectrum of the back electrode layer 4 and the reference sunlight spectrum AM1.5G at a wavelength of 300 nm to 1200 nm is absorbed by the transparent electrode layer 2 side (substrate side) surface of the back electrode layer 4. Defined as the amount of light (silver absorbed light amount).
The equivalent current value obtained by integrating the product of the light absorption coefficient spectrum of the second battery layer 92 and the reference sunlight spectrum AM1.5G at wavelengths of 300 nm to 1200 nm was defined as the light absorption amount of the second battery layer.

  FIG. 7 shows the relationship between the sum of the reflected light amount and the silver absorbed light amount in the tandem solar cell of Example 1 and the height difference h of the concavo-convex shape. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the sum of the reflected light amount and the silver absorbed light amount when the height difference is 0 nm. FIG. 8 shows the relationship between the amount of reflected light and the unevenness height difference h in the tandem solar cell of Example 1. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the amount of reflected light when the height difference is 0 nm. In FIG. 9, the relationship between the light absorption amount in the 2nd battery layer and the height difference h of uneven | corrugated shape in the tandem solar cell of Example 1 is shown. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the light absorption amount in the second battery layer when the height difference is 0 nm.

As shown in FIG. 7, the sum of the reflected light amount and the silver absorbed light amount was 96% or less in the case of the height difference of 0 nm within the range of the height difference of 60 nm to 210 nm. When the height difference was 120 nm, the amount of reflected light was minimal. As shown in FIG. 8, the amount of reflected light was 93% or less when the height difference was 60 nm or more and the height difference was 0 nm. The amount of light absorption in the second battery layer increased in the range from 60 nm to 210 nm in height difference corresponding to the sum of the amount of reflected light and the amount of absorbed silver.
Thus, a strong correlation was found between the sum of the amount of reflected light reflected and emitted from the back electrode layer and the amount of absorbed silver light, and the amount of light absorbed by the second battery cell. As shown in FIG. 8, in the solar cell of Example 1, when the height difference was 60 nm or more, the result was that the amount of reflected light was 93% or less of the reference (height difference 0 nm). However, when the height difference becomes large, the controllability when forming the uneven shape deteriorates, and it is difficult to uniformly form the back transparent electrode layer and the back electrode layer on the second battery layer having the uneven shape with a large height difference. Such inconvenience occurs. Therefore, considering the controllability when forming the uneven shape and the film thickness uniformity of the back surface structure, the height difference is preferably 210 nm or less.

(Example 2)
The thickness of the second battery layer in the stacked structure model of Example 1 was changed to 1.45 μm, the sum of the reflected light amount and the silver absorbed light amount, the reflected light amount, and the light absorption amount in the second battery layer. Was calculated.

  FIG. 10 shows the relationship between the sum of the amount of reflected light and the amount of absorbed silver in the tandem solar cell of Example 2 and the height difference h of the uneven shape. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the sum of the reflected light amount and the silver absorbed light amount when the height difference is 0 nm. FIG. 11 shows the relationship between the amount of reflected light and the height difference h of the concavo-convex shape in the tandem solar cell of Example 2. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the amount of reflected light when the height difference is 0 nm. In FIG. 12, the relationship between the light absorption amount in the 2nd battery layer and the height difference h of uneven | corrugated shape in the tandem-type solar cell of Example 2 is shown. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the light absorption amount in the second battery layer when the height difference is 0 nm.

  As shown in FIG. 10, when the height difference is 130 nm, the sum of the reflected light amount and the silver absorbed light amount is minimized. In Example 2, within the range of the height difference of 90 nm to 150 nm, the sum of the amount of reflected light and the amount of absorbed silver was 96% or less when the height difference was 0 nm. Also in Example 2, the light absorption amount in the second battery layer showed a strong correlation with the sum of the reflected light amount and the silver absorbed light amount, and increased in the range of 90 nm to 150 nm in height difference. As shown in FIG. 11, the amount of reflected light was 93% or less when the height difference was within a range of 110 nm to 200 nm and the height difference was 0 nm as a reference.

(Example 3)
In the laminated structure of FIG. 6, the haze ratio in the laminated body of the substrate 1 and the transparent electrode layer 2 was changed to 30%, and the average pitch of the texture structure was changed to 1000 nm. The film thickness of the second battery layer was 2.0 μm. Using the FDTD method, the sum of the amount of reflected light and the amount of absorbed silver light, the amount of reflected light, and the amount of light absorbed by the second battery layer were calculated.

  FIG. 13 shows the relationship between the sum of the amount of reflected light and the amount of absorbed silver in the tandem solar cell of Example 3 and the height difference h of the concavo-convex shape. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the sum of the reflected light amount and the silver absorbed light amount when the height difference is 0 nm. FIG. 14 shows the relationship between the amount of reflected light and the height difference h of the concavo-convex shape in the tandem solar cell of Example 3. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the amount of reflected light when the height difference is 0 nm. In FIG. 15, the relationship between the light absorption amount in the 2nd battery layer and the height difference h of uneven | corrugated shape in the tandem-type solar cell of Example 3 is shown. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the light absorption amount in the second battery layer when the height difference is 0 nm.

As shown in FIG. 13, when the height difference was 120 nm, the sum of the reflected light amount and the silver absorbed light amount was minimized. In Example 3, when the height difference was 100 nm or more, the sum of the reflected light amount and the silver absorbed light amount was 96% or less when the height difference was 0 nm. The amount of light absorption in the second battery layer increased in the above range. As shown in FIG. 14, the amount of reflected light was 90 nm or less with a height difference of 90 nm or more and 93% or less when the height difference was 0 nm as a reference.
In the solar cell of Example 3, as shown in FIG. 13, when the height difference is 100 nm or more, the sum of the reflected light amount and the silver absorbed light amount is 96% or less of the reference (the height difference 0 nm). It was. Further, as shown in FIG. 14, the height difference was 90 nm or more, and the amount of reflected light was 93% or less of the reference (the height difference 0 nm). However, in the same manner as in Example 1, considering the controllability when forming the uneven shape and the film thickness uniformity of the back surface structure, the height difference is preferably 210 nm or less.

Example 4
A laminated structure similar to that of Example 3 except that the thickness of the second battery layer was changed to 2.5 μm, the sum of the reflected light amount and the silver absorbed light amount, the reflected light amount, and the light in the second battery layer Absorption was calculated.
FIG. 16 shows the relationship between the sum of the amount of reflected light and the amount of absorbed silver in the tandem solar cell of Example 4 and the height difference h of the uneven shape. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the sum of the reflected light amount and the silver absorbed light amount when the height difference is 0 nm. FIG. 17 shows the relationship between the amount of reflected light and the height difference h of the concavo-convex shape in the tandem solar cell of Example 4. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the amount of reflected light when the height difference is 0 nm. In FIG. 18, the relationship between the light absorption amount in the 2nd battery layer and the height difference h of uneven | corrugated shape in the tandem-type solar cell of Example 4 is shown. In the figure, the horizontal axis represents the height difference h, and the vertical axis represents the light absorption amount in the second battery layer when the height difference is 0 nm.

  As shown in FIG. 16, when the height difference was 150 nm, the sum of the reflected light amount and the silver absorbed light amount was minimized. When the height difference is 90 nm or more, the sum of the reflected light amount and the silver absorbed light amount is 96% or less when the height difference is 0 nm. The amount of light absorption in the second battery layer increased in the above range. As shown in FIG. 17, the amount of reflected light was at least 120 nm in height difference and 93% or less when the height difference was 0 nm as a reference. Also in Example 4, like Example 1 and Example 3, when the controllability at the time of uneven | corrugated shape formation and the film thickness uniformity of a back surface structure are considered, it is preferable that an elevation difference shall be 210 nm or less.

  In the above Examples 1 to 4, calculations were performed using a laminated structure model in which a back transparent electrode layer was formed between the second battery layer and the back electrode layer. Since the back transparent electrode layer is thin, the surface shape of the back transparent electrode layer and the back electrode layer is a shape following the back electrode layer side surface of the second battery layer. Therefore, the same result can be obtained even when calculation is performed using a layered structure model in which the back transparent electrode layer is not formed.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Transparent electrode layer 3 Photoelectric conversion layer 4 Back electrode layer 5 Intermediate contact layer 6 Solar cell module 31 Amorphous silicon p layer 32 Amorphous silicon i layer 33 Amorphous silicon n layer 41 Crystalline silicon p layer 42 Crystalline silicon i layer 43 Crystalline silicon n layer 91 First battery layer 92 Second battery layer 100 Photoelectric conversion device

Claims (12)

A photoelectric conversion device comprising a transparent electrode layer, at least two power generation layers, and a back electrode layer on a substrate,
The back electrode layer comprises a silver thin film;
The substrate side surface of the back electrode layer has an uneven shape,
When the back electrode layer is smooth, the sum of the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer The photoelectric device is characterized in that it is 96% or less of the sum of the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer. Conversion device. A photoelectric conversion device comprising a transparent electrode layer, at least two power generation layers, and a back electrode layer on a substrate,
The back electrode layer comprises a silver thin film;
The substrate side surface of the back electrode layer has an uneven shape,
The amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate is reflected on the substrate-side surface of the back electrode layer when the back electrode layer is smooth. A photoelectric conversion device comprising 93% or less of the amount of reflected light emitted from a substrate.   3. The photoelectric conversion device according to claim 1, wherein a haze ratio of a laminate of the substrate and the transparent electrode layer is 20% or more and 30% or less.   4. The photoelectric conversion device according to claim 1, wherein a thickness of the power generation layer on the side of the back electrode layer is 1.45 μm or more and 2.5 μm or less.   5. The photoelectric conversion device according to claim 1, further comprising a back transparent electrode layer on a surface of the back electrode layer on the substrate side. A process for producing a photoelectric conversion device comprising a step of forming a transparent electrode layer on a substrate, a step of forming at least two power generation layers, and a step of forming a back electrode layer,
The back electrode layer comprises a silver thin film;
When the back electrode layer is smooth, the sum of the amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer The back electrode so as to be 96% or less of the sum of the amount of reflected light reflected from the substrate side surface of the back electrode layer and emitted from the substrate and the amount of light absorbed by the back electrode layer A method for manufacturing a photoelectric conversion device, comprising providing an uneven shape on a surface of the layer on the substrate side. A process for producing a photoelectric conversion device comprising a step of forming a transparent electrode layer on a substrate, a step of forming at least two power generation layers, and a step of forming a back electrode layer,
The back electrode layer comprises a silver thin film;
The amount of reflected light reflected from the substrate-side surface of the back electrode layer and emitted from the substrate is reflected on the substrate-side surface of the back electrode layer when the back electrode layer is smooth. A method for manufacturing a photoelectric conversion device, comprising: providing a concave-convex shape on a surface of the back electrode layer on the substrate side so that the amount of reflected light emitted from the substrate is 93% or less.   After controlling the formation conditions of the power generation layer on the back electrode layer side to provide the uneven shape on the surface of the power generation layer on the back electrode layer side, the back electrode layer The method for manufacturing a photoelectric conversion device according to claim 6, wherein the photoelectric conversion device is provided by forming the photoelectric conversion device.   Forming the power generation layer on the back electrode layer side, etching the surface of the power generation layer to provide a predetermined uneven shape on the surface of the power generation layer, and then forming the back electrode The method for manufacturing a photoelectric conversion device according to claim 6, wherein the photoelectric conversion device is provided.   The method for manufacturing a photoelectric conversion device according to any one of claims 6 to 9, wherein a haze ratio of a laminate of the substrate and the transparent electrode layer is 20% or more and 30% or less. .   The film thickness of the said electric power generation layer by the side of the said back surface electrode layer is 1.45 micrometers or more and 2.5 micrometers or less, The manufacture of the photoelectric conversion apparatus of any one of Claim 6 thru | or 10 characterized by the above-mentioned. Method.   The method for manufacturing a photoelectric conversion device according to claim 6, further comprising a back transparent electrode layer provided on a surface of the back electrode layer on the substrate side.

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