JP4875725B2 - Method for manufacturing thin-film silicon laminated solar cell - Google Patents

Description

  The present invention relates to a method for manufacturing a thin film silicon laminated solar cell.

In the technical field of solar cells,
(1) How to efficiently incorporate light from the sun into an energy conversion section such as a pin junction layer formed of a semiconductor material.

(2) How to increase the efficiency of conversion from solar energy to electric energy in the energy conversion section such as the pin junction layer.

There is a technical development item. And the improvement of the power generation efficiency of the whole solar cell is aimed at by improving these efficiency.

  FIG. 1 shows a schematic laminated structure of a solar cell having a conventional tandem structure for the purpose of improving these efficiencies. The solar cell shown in FIG. 1 includes a transparent insulating substrate 1, a first transparent electrode (first conductive layer) 2, a p-type silicon layer (amorphous silicon layer) 3, an i-type silicon layer (non-layered) sequentially stacked. Crystalline silicon layer) 4, n-type silicon layer (amorphous silicon layer) 5, p-type silicon layer (polycrystalline silicon layer) 6, i-type silicon layer (polycrystalline silicon layer) 7, n-type silicon layer (multiple silicon layer) A crystal silicon layer) 8, a second transparent electrode 9, and a back electrode 10.

  A p-type silicon layer (amorphous silicon layer) 3, an i-type silicon layer (amorphous silicon layer) 4, and an n-type silicon layer (amorphous silicon layer) 5 form an amorphous silicon solar cell. Is done. The amorphous silicon layer may be a layer containing silicon as a main component, for example, silicon carbide added with less than 50% carbon, silicon germanium added with less than 20% germanium, or may contain other elements of about several percent or less. The substantial main component may be silicon. The crystallinity of the amorphous silicon layer is not limited to the crystallinity of the p-type silicon layer and the n-type silicon layer, as long as most of the i-type silicon layer, which is the main photoelectric conversion layer, is amorphous.

  The p-type silicon layer (polycrystalline silicon layer) 6, the i-type silicon layer (polycrystalline silicon layer) 7, and the n-type silicon layer (polycrystalline silicon layer) 8 form a crystalline silicon solar cell. . The polycrystalline silicon layer may be a layer containing silicon as a main component, for example, silicon carbide to which carbon is added less than 50%, silicon germanium to which germanium is added to less than 20%, or may contain other elements of about several percent or less, The substantial main component may be silicon. As for the crystallinity of the polycrystalline silicon layer, the majority of the i-type silicon layer which is the main photoelectric conversion layer may be crystalline, and the crystallinity of the p-type silicon layer and the n-type silicon layer is not particular. Sunlight incident from the transparent insulating substrate 1 side is first converted into electric energy in the amorphous silicon solar cell. Next, sunlight that has not been absorbed by the amorphous silicon solar cell reaches the crystalline silicon solar cell formed in the lower layer, where it is converted back into electrical energy. In the solar cell shown in FIG. 1, the thickness of the first transparent electrode 2 is adjusted so that the reflection of incident sunlight is reduced and as much sunlight as possible is taken into the solar cell. In addition, amorphous silicon solar cells have a phenomenon in which the amount of power generation decreases due to deterioration due to light irradiation. However, the film quality is improved, and the rate of light deterioration is reduced (improved stabilization efficiency) by reducing defects in the film. ing.

  However, there are still many remaining issues such as the determination of the lamination configuration of solar cells and the optimization conditions for the thickness of each layer constituting them. In particular, it is necessary to reduce the film thickness of the amorphous silicon solar cell in order to reduce the photodegradation rate of the solar cell and improve the stabilization efficiency. Moreover, in order to improve productivity while aiming at improvement in power generation efficiency, it is necessary to reduce the film thickness of the crystalline silicon solar cell. Since the first solar cell layer made of amorphous silicon and the second solar cell layer made of crystalline silicon are connected in series as an electric circuit of a tandem solar cell, the generated current of the battery is It is governed by a small amount of generated current. Therefore, it is desired that the generated current is well balanced. The importance of deciding the optimization conditions for each layer thickness in consideration of these factors is increasing.

  In relation to the above-described technology, the following proposals have been made.

  In the “thin film photoelectric conversion device” disclosed in JP-A-10-117066, the first and second main surfaces are substantially covered with a polycrystalline photoelectric conversion layer, and the second main surface is covered. The polycrystalline photoelectric conversion layer is substantially composed of a polycrystalline silicon thin film and has an average thickness in the range of 0.5 to 20 μm, and at least the first main surface has a surface texture structure. However, a thin film photoelectric conversion device including fine irregularities having a texture structure smaller than ½ of the average thickness and having a height difference substantially in the range of 0.05 to 3 μm has been proposed.

  In addition, in the “integrated hybrid thin film photoelectric conversion device” disclosed in Japanese Patent Application Laid-Open No. 2001-177134, a transparent electrode layer, an amorphous semiconductor photoelectric conversion unit layer, and a crystalline semiconductor that are sequentially stacked on a transparent insulating substrate. The photoelectric conversion unit layer and the back electrode layer are separated by a plurality of parallel linear separation grooves formed by laser scribing so as to form a plurality of hybrid photoelectric conversion cells, and the plurality of cells are separated. The amorphous photoelectric conversion layers included in the amorphous photoelectric conversion unit layer are electrically connected in series via a plurality of connecting grooves parallel to the grooves, and the amorphous photoelectric conversion layer has a thickness of 250 nm or more. The thickness of the crystalline photoelectric conversion layer included in the conversion unit layer is less than 3 μm, and the integrated hybrid thin film is in the range of 4 to 8 times the thickness of the amorphous photoelectric conversion layer. The photoelectric conversion device has been proposed.

In addition, in the “integrated hybrid thin film photoelectric conversion device” disclosed in Japanese Patent Application Laid-Open No. 2001-177134, a transparent electrode layer, an amorphous semiconductor photoelectric conversion unit layer, which are sequentially stacked on a transparent insulating substrate, A conductive optical intermediate layer that reflects and transmits light, a crystalline semiconductor photoelectric conversion unit layer, and a back electrode layer are separated by a plurality of separation grooves so as to form a plurality of hybrid photoelectric conversion cells; and The plurality of cells are electrically connected in series with each other through a plurality of connection grooves, the amorphous photoelectric conversion unit layer has a thickness in the range of 0.01 to 0.5 μm, The quality photoelectric conversion unit layer has a thickness in the range of 0.1 to 10 μm, and the optical intermediate layer has a thickness in the range of 10 to 100 nm and 1 × 10 ⁻³ to 1 × 10 ⁻¹ Ω.・ Cm range Integrated hybrid thin film photoelectric converter has been proposed which is characterized by having a resistivity of the inner.

Japanese Patent Laid-Open No. 10-117006 JP 2001-177134 A JP 2002-118273 A

  An object of the present invention is to provide a method for manufacturing a thin-film silicon laminated solar cell with high efficiency and high productivity.

  Hereinafter, means for solving the problem will be described using the reference numerals in parentheses used in [Mode for Carrying Out the Invention]. These symbols are added to clarify the correspondence between the description of [Claims] and the description of [Mode for Carrying Out the Invention]. It should not be used to interpret the technical scope of the described invention.

  The method for producing a thin film silicon laminated solar cell according to the present invention is a method for producing a thin film silicon laminated solar cell comprising a first conductive layer, a first solar cell layer, and a second solar cell layer on a transparent substrate. The thickness of the first solar cell layer and the second thickness when the pitch and height difference of the uneven portions formed on the surface of the first conductive layer opposite to the transparent substrate are set to predetermined values, respectively. A step of creating a graph representing the relationship between the film thickness of the solar cell layer and the stabilization efficiency of the solar cell in the combination of the film thicknesses, and the first sun from which a predetermined stabilization efficiency is obtained based on the graph A step of determining a thickness of the battery layer and a thickness of the second solar cell layer, and a step of forming the first solar cell layer and the second solar cell layer so as to have the determined thickness. It is characterized by including.

  The method for producing a thin-film silicon laminated solar cell according to the present invention includes a first conductive layer, a first solar cell layer, a second solar cell layer, the first solar cell layer, and the second sun on a transparent substrate. A method of manufacturing a thin-film silicon laminated solar cell including a transparent intermediate layer between a battery layer and a pitch and height difference of uneven portions formed on a surface of the first conductive layer opposite to the transparent substrate And the film thickness of the first solar cell layer and the film thickness of the second solar cell layer when the film thickness of the transparent intermediate layer is a predetermined value, and the stability of the solar cell in the combination of the film thicknesses. A step of creating a graph representing the relationship with the conversion efficiency, and determining the film thickness of the first solar cell layer and the film thickness of the second solar cell layer based on the graph to obtain a predetermined stabilization efficiency A first solar cell layer and a step so that the determined film thickness is obtained; Characterized in that it comprises a step of forming a serial second solar cell layer.

  In the above invention, in the step of determining the film thickness, the film thickness range of the first solar cell layer and the film thickness range of the second solar cell layer that satisfy the predetermined stabilization efficiency are specified and specified. It is preferable that the smallest value in the film thickness range is the film thickness of the first solar cell layer and the film thickness of the second solar cell layer.

  The thin film silicon laminated solar cell in the reference example of the present invention includes a first conductive layer (20) formed on a transparent substrate (10) and a first solar cell layer (150) formed on the first conductive layer. And a second solar cell layer (200) laminated on the first solar cell layer, the first conductive layer has a pitch of 0.2 to 2.5 μm, and the height difference is 1/2 to 1 of the pitch. It has unevenness that is / 4.

  Moreover, the 1st solar cell layer (150) regarding the thin film silicon | silicone laminated | stacked solar cell of the reference example of this invention is p-type (30) and n-type (50) laminated | stacked in order on a 1st conductive layer (20). ) One conductivity type silicon layer, i-type silicon layer (40), and the other conductivity type silicon layer, and the second solar cell layer (200) is the other conductivity type of the first solar cell layer. The p-type (60) and n-type (80) conductive type silicon layers, the i-type silicon layer (70), and the other conductive type, which are sequentially or indirectly stacked on the silicon layer in turn And a silicon layer.

  The first solar cell layer (150) related to the thin film silicon laminated solar cell of the reference example of the present invention is an amorphous silicon solar cell mainly composed of amorphous silicon and has a thickness of 200 to 400 nm. It is. A 2nd solar cell layer (200) is a crystalline silicon solar cell which has a crystalline silicon as a main component, The thickness is 1.5-3 micrometers.

  In the thin film silicon laminated solar cell of the reference example of the present invention, an intermediate conductive layer (300) is further laminated between the first solar cell layer (150) and the second solar cell layer (200).

  Moreover, the thickness of the 1st solar cell layer (150) regarding the thin film silicon | silicone laminated solar cell of the reference example of this invention is 100-400 nm, and the thickness of a 2nd solar cell layer (200) is 1-3 micrometers. is there.

  Further, the intermediate conductive layer (300) related to the thin film silicon laminated solar cell of the reference example of the present invention is formed of a material mainly containing at least one of ZnO, ITO (Indium Tin Oxide) or SnO2, The light absorption rate at a wavelength of 600 to 1200 nm by the intermediate conductive layer is 1% or less.

  The thin-film silicon laminated solar cell of the reference example of the present invention further includes a second conductive layer (100) formed on the second solar cell layer (200), and the second conductive layer is formed of Ag. Is done.

  In the thin-film silicon laminated solar cell of the reference example of the present invention, the third conductive layer (90) is further laminated between the second solar cell layer (200) and the second conductive layer (100).

  The third conductive layer (90) related to the thin film silicon laminated solar cell of the reference example of the present invention is formed of a material mainly composed of ZnO having a thickness of 20 nm to 100 nm.

  According to the present invention, a thin-film silicon laminated solar cell with high efficiency and high productivity can be provided.

It is a figure which shows the general | schematic laminated structure of the conventional thin film silicon | silicone laminated | stacked solar cell which has a tandem structure. 1 is a diagram showing a schematic stacked configuration of a thin film silicon stacked solar cell according to Embodiment 1. FIG. In Embodiment 2, it is a figure which shows the relationship between the film thickness of an amorphous silicon layer and a crystalline silicon layer, and the stabilization efficiency of the thin film silicon | silicone laminated solar cell at that time. FIG. 4 is a diagram showing a schematic stacked configuration of a thin film silicon stacked solar cell according to a third embodiment. In Embodiment 4, it is a figure which shows the relationship between the film thickness of an intermediate | middle layer, and the quantum efficiency of wavelength 800nm by the crystalline solar cell corresponding to the film thickness of an intermediate | middle layer. In Embodiment 5, it is a figure which shows the film thickness of an amorphous silicon layer and a crystalline silicon layer, and the stabilization efficiency of the thin film silicon | silicone laminated solar cell at that time. In Embodiment 6, it is a figure which shows the relationship between the film thickness of a 2nd transparent electrode, and the stabilization efficiency of the solar cell corresponding to the film thickness of a 2nd transparent electrode.

  A mode for carrying out a thin film silicon laminated solar cell according to the present invention will be described below with reference to the accompanying drawings.

  The object of the present invention is to increase the efficiency of solar cells and to improve productivity. For this purpose, the pitch and height difference values of the concavo-convex portions formed on the first transparent electrode on which sunlight is incident were optimized. Thereby, the incident path | route of sunlight in a solar cell was lengthened, and the stabilization efficiency was improved. Moreover, in the solar cell having a tandem structure, the film thickness values of the amorphous silicon solar cell and the crystalline solar cell were optimized.

  Here, in order to improve the stabilization efficiency, the film thickness of the amorphous silicon solar cell is preferably as thin as possible. Moreover, in order to improve productivity while aiming at the improvement of stabilization efficiency, it is necessary to make the film thickness of a crystalline silicon solar cell as thin as possible.

  In the present invention, a thin-film silicon laminated solar cell with high efficiency and high productivity is realized in consideration of the film thickness balance of each layer as described above.

(Embodiment 1)
FIG. 2 shows a laminated structure of a thin film silicon laminated solar cell having a tandem structure according to the first embodiment.

  The thin-film silicon laminated solar cell according to the present embodiment includes a transparent insulating substrate 10 sequentially laminated, a first transparent electrode 20 having irregularities with a pitch of 0.6 μm and a height difference of 0.2 μm, Amorphous silicon having a pin structure or a nip structure comprising a p-type silicon layer (amorphous silicon layer) 30, an n-type silicon layer (amorphous silicon layer) 50, and an i-type silicon layer (amorphous silicon layer) 40 Crystal of pin structure or nip structure comprising solar cell 150, p-type silicon layer (crystalline silicon layer) 60, n-type silicon layer (crystalline silicon layer) 80, and i-type silicon layer (crystalline silicon layer) 70 A silicon solar cell 200, a second transparent electrode 90, and a back electrode 100 are provided.

  In the present embodiment, uneven portions having a pitch of 0.6 μm and a height difference of 0.2 μm of the pitch are formed on the surface of the first transparent electrode 20 in the sunlight traveling direction. Thereby, all the layers formed in the lower layer part (sunlight advancing direction) of the said 1st transparent electrode 20 are laminated | stacked sequentially with the form match | combined with this uneven | corrugated | grooved part shape.

  In this embodiment, when the amorphous silicon solar cell 150 has a film thickness of 300 nm and the crystalline silicon solar cell 200 has a film thickness of 2 μm, stabilization under sunlight irradiation conditions of AM (Air Mass) 1.5 Efficiency (1SUN; 100mW / cm2, 50 ° C, efficiency after photodegradation by light irradiation for 1000 hours, or efficiency after photodegradation by accelerating light degradation conditions after confirming that the conditions are equivalent) It was 11.5%.

  The concavo-convex portion formed on the surface of the first transparent electrode 20 functions to extend the optical path length in the power generation layer (amorphous silicon solar cell, crystalline silicon solar cell) by scattering incident sunlight. Have. Here, the pitch and the height difference of the surface irregularities are the same pitch as the wavelength of the light to be scattered and the height difference of about 1/3 (because the refractive index of silicon is about 3). It is known that the scattering rate is maximized.

  In addition to the values of the pitch and height difference of the concavo-convex part of the present embodiment, as a comparative example, the pitch and height difference of the concavo-convex part is (a) pitch 0.2 μm, height difference 0.1 μm, (b) pitch 2.5 μm. , Height difference 0.8 μm, (c) pitch 4 μm, height difference 1 μm (amorphous silicon solar cell 150 has a film thickness of 300 nm, crystalline silicon solar cell 200 has a film thickness of 2 μm) Stabilization efficiency was measured. According to this result, the respective stabilization efficiencies were (a) 10.7%, (b) 10.7%, and (c) 10.2%.

  In this embodiment, the stabilization efficiency of 11.5% is realized by efficiently scattering sunlight having a wavelength of 700 to 900 nm, which greatly contributes to the generated current in the crystalline silicon solar cell 200, and crystalline silicon. This is a result of improved power generation efficiency in the solar cell 200.

  In the present embodiment, an uneven portion is formed on the surface of the first transparent electrode 20 in order to obtain a stabilization efficiency of 10.5% or more. Then, by selecting 0.2 to 2.5 μm as the pitch of the concavo-convex portions and 1/2 to ¼ of the pitch as the height difference, the thin film silicon laminated solar having a maximum stabilization efficiency of 11.5% A battery can be realized.

(Embodiment 2)
The basic laminated structure of the thin film silicon laminated solar cell according to the second embodiment is the same as that of the thin film silicon laminated solar cell of the first embodiment. However, in the present embodiment, the film thickness values of the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200 are optimized so that the stabilization efficiency is maximized.

  The power generation current of the solar cell having the tandem structure in the present embodiment is regulated on the lower side of the power generation current of the amorphous silicon solar cell 150 that is the top cell and the crystalline silicon solar cell 200 that is the bottom cell. Will be ruled. Here, the generated current of the amorphous silicon solar battery 150 as the top cell increases in accordance with this film thickness. In addition, the generated current of the crystalline silicon solar cell 200 that is the bottom cell depends on the amount of light that is not absorbed by the top cell (that is, the amount of light that reaches the larger the thinner the amorphous silicon solar cell 150 that is the top cell). ), The same reaching light amount increases according to the film thickness of the crystalline silicon solar cell 200 as the bottom cell. Therefore, an appropriate balance exists between the film thicknesses of the amorphous silicon solar cell 150 as the top cell and the crystalline silicon solar cell 200 as the bottom cell.

  On the other hand, increasing the film thickness of the amorphous silicon solar cell 150, which is the top cell, means a reduction in production efficiency. In addition, the photodegradation rate increases as the thickness of the amorphous silicon solar cell 150 increases. Accordingly, there is an appropriate value for the film thickness of the amorphous silicon solar cell 150 itself.

  Increasing the thickness of the crystalline silicon solar cell 200 as the bottom cell causes a decrease in production efficiency and a decrease in generated voltage due to an increase in the amount of defects in the layer of the crystalline silicon solar cell 200 and a decrease in potential gradient. Accordingly, there is an appropriate value for the film thickness of the crystalline silicon solar cell 200.

  FIG. 3 shows the respective film thicknesses of the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200 of the thin film silicon laminated solar cell according to the present embodiment obtained by measurement (♦) and simulation, and the films. The relationship with the stabilization efficiency in a thick structure is shown. Evaluation (measurement) of the solar cell was performed under the conditions of AM1.5 based on JIS C8934. It is known that a solar cell including an amorphous silicon solar cell undergoes photodegradation during use. The stabilization efficiency after photodegradation is the same as that in the first embodiment, after 1 SUN, 50 ° C., 1000 hours of light irradiation, or under accelerated light degradation conditions that have been confirmed to be equivalent to that. It was set as the measured value after light irradiation.

  As shown in FIG. 3, the stabilization efficiency is 11% or more, good efficiency, and good productivity (the film thickness of the amorphous silicon solar cell 150 is 400 nm or less, and the film thickness of the crystalline silicon solar cell 200 is Is 3 μm or less), the amorphous silicon solar cell 150 has a thickness of 200 to 400 nm, and the crystalline silicon solar cell 200 has a thickness of 1.5 to 3 μm (the hatched portion in FIG. 3). )Met. In this range, a stabilization efficiency of up to about 12% is realized.

  In the present embodiment, the film thickness of each of amorphous silicon solar cell 150 and crystalline silicon solar cell 200 is optimized so as to maximize the stabilization efficiency. As a result, a thin-film silicon laminated solar cell with higher efficiency and higher productivity than that of the first embodiment is realized.

(Embodiment 3)
FIG. 4 shows a schematic laminated configuration of a thin film silicon laminated solar cell according to the third embodiment. The basic laminated configuration of the present embodiment is the same as that of the thin film silicon-based laminated solar cell according to the first embodiment. However, in the present embodiment, a transparent intermediate layer 300 is further laminated between the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200.

  The thin-film silicon laminated solar cell according to the present embodiment has a transparent insulating substrate 10 and a concavo-convex portion having a pitch of 0.6 μm and a height difference of 0.2 μm, which are sequentially laminated, on the solar light traveling direction surface. A pin structure including a first transparent electrode 20 having a p-type silicon layer (amorphous silicon layer) 30, an n-type silicon layer (amorphous silicon layer) 50, and an i-type silicon layer (amorphous silicon layer) 40. Alternatively, a nip structure amorphous silicon solar cell (top cell) 150, a transparent intermediate layer 300, a p-type silicon layer (crystalline silicon layer) 60, an n-type silicon layer (crystalline silicon layer) 80, and i-type silicon. A crystalline silicon solar cell (bottom cell) 200 having a pin structure or a nip structure composed of a layer (crystalline silicon layer) 70, a second transparent electrode 90, and a back electrode 100 are provided.

  In the present embodiment, by further laminating the transparent intermediate layer 300, a part of incident sunlight is reflected by the transparent intermediate layer 300 and is incident on the amorphous silicon solar cell 150 again.

  Thereby, the electric power generation current in a top cell increases. And even if the film thickness of a top cell is made thin, the generated electric current equivalent to the case where the transparent intermediate | middle layer 300 is not laminated | stacked can be obtained. By reducing the film thickness of the amorphous silicon solar battery 150 that is the top cell, light deterioration in the layer can be suppressed, and the stabilization efficiency of the battery as a whole can be improved.

  A thin-film silicon laminated solar cell according to the present embodiment (amorphous silicon solar cell 150; 250 nm, crystalline silicon solar cell 200; 2 μm) includes a transparent intermediate layer 300 made of ZnO and having a thickness of 60 nm. Yes. ZnO used as the transparent intermediate layer 300 is doped with 1.5% Ga. The transparent intermediate layer 300 is laminated by sputtering in an oxygen-containing atmosphere. And 12.4% is implement | achieved as the stabilization efficiency at this time. The transparent intermediate layer 300 may be made of ZnO as a main component and transparent, and may or may not contain Ga, Al or the like as a dopant.

  In the thin film silicon laminated solar cell in the present embodiment, the transparent intermediate layer 300 is laminated between the amorphous silicon solar cell 150 that is the top cell and the crystalline silicon solar cell 200 that is the bottom cell. Thereby, the electric power generation current in the amorphous silicon solar cell 150 can be increased. Further, the amorphous silicon solar cell 150 can be made thin. As compared with Embodiments 1 and 2, the stabilization efficiency is further improved.

(Embodiment 4)
In the thin film silicon multilayer solar cell according to the fourth embodiment, the value of the film thickness of the transparent intermediate layer 300 of the thin film silicon multilayer solar cell according to the third embodiment is optimized to improve the stabilization efficiency. The

  As described in the third embodiment, by increasing the film thickness of the transparent intermediate layer 300, the power generation current of the amorphous silicon solar battery 150 that is the top cell can be increased. At this time, the generated current in the bottom cell at the wavelength of sunlight reflected by the transparent intermediate layer 300 decreases. Actually, in the crystalline silicon solar cell 200 which is a bottom cell, conversion into electric energy by sunlight in a longer wavelength region is performed as compared with the amorphous silicon solar cell 150 which is a top cell.

  Therefore, by optimizing the film thickness of the transparent intermediate layer 300, it is necessary to suppress the absorption rate of sunlight in the long wavelength region that should be absorbed by the crystalline silicon solar cell 200 that is the bottom cell, by the transparent intermediate layer 300. become.

  FIG. 5 shows the film thickness of the transparent intermediate layer 300 of the thin film silicon laminated solar cell according to the present embodiment, and the quantum of the wavelength 800 nm (corresponding to the long wavelength region of sunlight) in the crystalline silicon solar cell 200 as the bottom cell. It shows the relationship with efficiency (ratio of contribution to power generation in incidence). As the film thickness of the transparent intermediate layer 300 increases, the reflectance of sunlight in the long wavelength region at the transparent intermediate layer 300 also increases, and the amount of light incident on the crystalline silicon solar cell 200 that is the bottom cell decreases. As an optical characteristic of the transparent intermediate layer 300 having a wavelength of 600 to 1200 nm, the light absorptance is less than 1%, and it is almost transparent to this wavelength region.

  On the other hand, when the film thickness of the transparent intermediate layer 300 increases, the light confinement effect increases between the transparent intermediate layer 300 and the back electrode 100. For this reason, the absorption factor of the sunlight which injected into the crystalline silicon solar cell 200 which is a bottom cell increases. According to FIG. 5, the light confinement effect in the crystalline silicon solar cell 200 as a bottom cell effectively acts on sunlight having a wavelength of 800 nm (the quantum efficiency can be maintained at a constant value). The film thickness of 300 is 100 nm or less.

  According to the present embodiment, the optimum film thickness value of the transparent intermediate layer 300 is determined in consideration of the power generation current balance between the amorphous silicon solar cell 150 that is the top cell and the crystalline silicon solar cell 200 that is the bottom cell. The Thereby, a thin film silicon laminated solar cell having higher stabilization efficiency is realized.

(Embodiment 5)
The basic laminated structure of the thin film silicon laminated solar cell according to the fifth embodiment is the same as that of the thin film silicon laminated solar cell of the third embodiment. However, in the present embodiment, the film thickness values of the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200 are optimized so as to maximize the stabilization efficiency.

  The generated current of the solar cell having the tandem structure according to the present embodiment includes the generated current of the amorphous silicon solar cell 150 that is the top cell and the crystal that is the bottom cell, under a certain thickness of the transparent intermediate layer 300. It is governed on the low power generation current side of the high-quality silicon solar cell 200. The generated current of the amorphous silicon solar cell 150 that is the top cell increases in accordance with the film thickness. The generated current of the crystalline silicon solar cell 200 that is the bottom cell absorbs light that has not been absorbed by the top cell (that is, the amount of light that reaches the larger the thinner the amorphous silicon solar cell 150 that is the top cell), the same. If the amount of light reaches the target, the thickness increases according to the film thickness of the crystalline silicon solar cell 200 which is a bottom cell. Therefore, an appropriate balance exists between the film thicknesses of the amorphous silicon solar cell 150 as the top cell and the crystalline silicon solar cell 200 as the bottom cell.

  When the thickness of the amorphous silicon solar cell 150 that is the top cell is increased, the production efficiency decreases. Moreover, when the film thickness of the amorphous silicon solar battery 150 which is the top cell is increased, the light deterioration rate increases and the stabilization efficiency decreases. Accordingly, there is an appropriate value for the film thickness of the amorphous silicon solar cell 150 itself.

  Increasing the thickness of the crystalline silicon solar cell 200 as the bottom cell causes a decrease in production efficiency and a decrease in generated voltage due to an increase in the amount of defects in the layer of the crystalline silicon solar cell 200 and a decrease in potential gradient. Accordingly, there is an appropriate value for the film thickness of the crystalline silicon solar cell 200.

  FIG. 6 shows the film thicknesses of the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200 of the thin film silicon laminated solar cell according to the present embodiment and the films obtained by measurement (♦) and simulation. The relationship with the stabilization efficiency in a thick structure is shown. Evaluation (measurement) of the solar cell was performed under the conditions of AM1.5 based on JIS C8934. It is known that a solar cell including an amorphous silicon solar cell undergoes photodegradation during use. As with the first and second embodiments, the stabilization efficiency after photodegradation is 1 SUN, 50 ° C., after 1000 hours of light irradiation, or an accelerated light degradation condition that has been confirmed to be equivalent to that. The measured value after light irradiation at.

  As shown in FIG. 6, the stabilization efficiency is 11% or more, the efficiency is good, and the productivity (the film thickness of the amorphous silicon solar cell 150 is 400 nm or less and the film thickness of the crystalline silicon solar cell 200 is Is 3 μm or less) in the range where the film thickness of the amorphous silicon solar cell 150 is 100 to 400 nm and the film thickness of the crystalline silicon solar cell 200 is 1 to 3 μm (hatched portion in FIG. 6). is there. In this range, a stabilization efficiency of up to about 13% is realized.

  In the present embodiment, the film thickness values of amorphous silicon solar cell 150 and crystalline silicon solar cell 200 are optimized in the thin film silicon laminated solar cell in which transparent intermediate layer 300 is formed. Thereby, as compared with the third embodiment, higher stabilization efficiency and higher productivity (higher stabilization efficiency can be obtained with the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200 having a thinner film thickness). Can be realized).

  In addition, since high stabilization efficiency can be realized by the amorphous silicon solar cell 150 and the crystalline silicon solar cell 200 having thinner thicknesses, the strain stress in each stack is reduced. Thereby, a highly reliable thin film silicon laminated solar cell is realized.

(Embodiment 6)
In the thin-film silicon multilayer solar cell according to the sixth embodiment, the first layer is laminated between the crystalline silicon solar cell 200 that is the bottom cell of the thin-film silicon multilayer solar cell according to the third embodiment and the back electrode 100. The film thickness of the two transparent electrodes 90 (ZnO) is optimized for improving the stabilization efficiency.

  By optimizing the film thickness of the second transparent electrode 90, sunlight in the long wavelength region (wavelength 800 nm) that has not been absorbed by the crystalline silicon solar cell 200 as the bottom cell is converted into the second transparent electrode 90 and the back electrode. 100 to reflect efficiently. Then, sunlight in the long wavelength region is efficiently re-entered into the crystalline silicon solar cell 200 layer. Thereby, the electric power generation current in the crystalline silicon solar cell 200 which is a bottom cell increases, and the stabilization efficiency in the whole thin film silicon laminated solar cell improves.

  In FIG. 7, the relationship between the film thickness of the 2nd transparent electrode 90 of the thin film silicon | silicone laminated solar cell concerning this Embodiment, and the stabilization efficiency in each film thickness is shown. As an optical characteristic with respect to the wavelength of 600 to 1200 nm of the second transparent electrode 90 (ZnO), the light absorptance is less than 1%, and it is almost transparent to this wavelength region.

  According to FIG. 7, by setting the film thickness of the second transparent electrode 90 to be stacked to 20 to 100 nm, it is possible to realize a thin film silicon stacked solar cell that maintains a stabilization efficiency of 12% or more.

  According to the present embodiment, the film thickness of the second transparent electrode 90 is optimized. Thereby, the reflectance of the sunlight of the long wavelength region which is reflected by the 2nd transparent electrode 90 and the back surface electrode 100, and reenters into the crystalline silicon solar cell 200 which is a bottom cell improves. And the electric power generation current in the crystalline silicon solar cell 200 increases. Thereby, a thin film silicon laminated solar cell having higher stabilization efficiency is realized.

  The thin-film silicon laminated solar cell described in the first to sixth embodiments has a tandem structure. However, the present application is applicable to all solar cells having a combination of amorphous silicon solar cells and crystalline silicon solar cells.

DESCRIPTION OF SYMBOLS 1, 10 ... Transparent insulating substrate 2, 20 ... 1st transparent electrode 3, 30 ... p-type silicon layer (amorphous silicon layer)
4, 40 ... i-type silicon layer (amorphous silicon layer)
5, 50 ... n-type silicon layer (amorphous silicon layer)
6, 60 ... p-type silicon layer (polycrystalline silicon layer)
7, 70 ... i-type silicon layer (polycrystalline silicon layer)
8, 80 ... n-type silicon layer (polycrystalline silicon layer)
9, 90 ... second electrode 10, 100 ... back electrode 150 ... amorphous silicon solar cell 200 ... crystalline silicon solar cell 300 ... transparent intermediate layer

Claims (2)

On the transparent substrate, the first conductive layer, the first solar cell layer, the second solar cell layer , the second conductive layer formed on the second solar cell layer, the second solar cell layer, and the A method for manufacturing a thin-film silicon laminated solar cell comprising a third conductive layer formed between the second conductive layer ,
The pitch of the concavo-convex portions formed on the surface of the first conductive layer opposite to the transparent substrate is selected to be 0.2 to 2.5 μm, and the height difference is selected to be 1/2 to 1/4 of the pitch. Forming the first conductive layer;
Creating a graph representing the relationship between the film thickness of the first solar cell layer and the film thickness of the second solar cell layer, and the stabilization efficiency of the solar cell in the combination of the film thickness;
Based on the graph, the step of specifying the film thickness range of the first solar cell layer and the film thickness range of the second solar cell layer that can obtain a predetermined stabilization efficiency;
The smallest value among the specified thickness range is determined as the film thickness of the film thickness and the second solar cell layer of the first solar cell layer, to a thickness that is the determined, the Forming the first solar cell layer and the second solar cell layer ;
And a step of forming the third conductive layer having a thickness of 20 to 100 nm made of a material containing ZnO as a main component . On the transparent substrate, a first conductive layer, a first solar cell layer, a second solar cell layer, a transparent intermediate layer between the first solar cell layer and the second solar cell layer, and the second A method for manufacturing a thin film silicon laminated solar cell , comprising: a second conductive layer formed on a solar cell layer; and a third conductive layer formed between the second solar cell layer and the second conductive layer. There,
The pitch of the concavo-convex portions formed on the surface of the first conductive layer opposite to the transparent substrate is selected to be 0.2 to 2.5 μm, and the height difference is selected to be 1/2 to 1/4 of the pitch. Forming the first conductive layer;
Forming the transparent intermediate layer having a thickness of 60 to 100 nm with a material mainly composed of at least one of ZnO, ITO, and SnO ₂ ;
Creating a graph representing the relationship between the film thickness of the first solar cell layer and the film thickness of the second solar cell layer, and the stabilization efficiency of the solar cell in the combination of the film thickness;
Based on the graph, the step of specifying the film thickness range of the first solar cell layer and the film thickness range of the second solar cell layer that can obtain a predetermined stabilization efficiency;
The smallest value among the specified thickness range is determined as the film thickness of the film thickness and the second solar cell layer of the first solar cell layer, to a thickness that is the determined, the Forming the first solar cell layer and the second solar cell layer ;
And a step of forming the third conductive layer having a thickness of 20 to 100 nm made of a material containing ZnO as a main component .

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