JP2004153028A - Thin-film photoelectric converting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin-film photoelectric converting device which is easily manufactured and free of optical deterioration and has high conversion efficiency. <P>SOLUTION: A first thin-film photoelectric converting element 20 comprises on a light-transmissive substrate 11 a first translucent conductive layer 12, a first single-conductive silicon-based semiconductor layer 21, an intrinsic first translucent conductive layer 22, a first reverse conductive silicon-based semiconductor layer 23, and a second translucent conductive layer 30. A second thin-film photoelectric converting element 70 comprises on a conductive substrate 60 as a second substrate or a second insulating substrate 50 equipped with a conductive layer 61 a second single-conductive silicon-based semiconductor 71, an intrinsic second crystalline silicon-based semiconductor layer 72 which has column-grown surface unevenness, a second crystalline silicon-based semiconductor layer 72, a second reverse conductive silicon-based semiconductor layer 73, and a third translucent conductive layer 80. A contact layer 90 between both the elements is formed of a translucent resin layer 91 or an air layer 92 for heat insulation and the translucent resin layer 91. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mechanical stack type thin-film photoelectric conversion device in which photoelectric conversion elements formed on two substrates are attached to each other so as to face each other so that the two substrates are located outside, and electrical outputs are separately taken out. The present invention relates to a mechanical stack type thin film photoelectric conversion device having a light confinement structure (and a heat insulation structure) using crystalline thin film silicon-based semiconductor layers for both substrates.
[0002]
[Prior art]
Silicon-based thin-film solar cells are being actively developed for high conversion efficiency, suppression of light deterioration, large area, and low cost. In this context, active development of silicon-based thin-film solar cells with various concavo-convex structures using light confinement effect and stacked type in which multiple semiconductor junctions with different forbidden band widths are stacked in order to make effective use of solar energy distribution. is there. Development of amorphous silicon-based thin-film solar cells for suppressing photodegradation is active.
[0003]
As a conventional example 1, there is known a mechanical stack type thin film solar cell module in which two types of substrates composed of a group of photoelectric conversion elements are mechanically bonded to each other with an adhesive, and electric outputs are separately taken out. reference).
[0004]
This thin-film solar cell module has a photoelectric conversion region made of a first semiconductor, transparent electrodes on both sides, a first glass substrate provided with a plurality of separated unit cells connected in series, and a narrower than the first semiconductor. A photoelectric conversion region made of a second semiconductor having a band gap and a second glass substrate having a transparent electrode on the side opposite to the substrate and having a separately formed series-connected unit cell are positioned facing each other with both substrates outside. The substrates are hermetically connected to each other by glass, and the space between the unit cells on both substrates is blocked from the outside. In the embodiment disclosed in Patent Document 1, an amorphous silicon PIN junction is described as a first semiconductor, and an amorphous silicon germanium PIN junction is described as a second semiconductor.
[0005]
With this configuration, light incident from the cell side including the first semiconductor having a wide band gap is absorbed by the cell and a photocurrent is generated by junction, but light not absorbed is transmitted from the opposing second semiconductor having a narrow band gap. Since the photocurrent is generated again by being absorbed in the cell, the utilization efficiency of the incident light is improved. Also, in order to connect both ends of each of the two series solar cells, the first semiconductor is connected in 5 series, the second semiconductor is connected in 6 series, and the optimum operating voltages at both ends are almost equal. I am trying to become. The two substrates are sealed with low-melting glass, and an inert gas such as Ar is sealed therein to protect them from humidity and other external atmospheres.
[0006]
As Conventional Example 2, a mechanical stack type thin-film solar cell module is known (see Patent Document 2). This tandem solar cell module is composed of polycrystalline silicon, a lower first solar cell submodule having a large area, a transparent insulating intermediate layer acting as an optical coupler, and a large area transparent amorphous silicon made of hydrogenated amorphous silicon. The upper second solar cell sub-module is characterized by comprising unrelated electrical contacts of both sub-modules.
[0007]
Further, as the polycrystalline silicon, a thin film solar cell module in which a polycrystalline structure is formed by a recrystallization treatment, for example, annealing after a silicon material is deposited on the substrate other than the bulk single crystal silicon is preferable. The optical coupler is made of an electrically insulating material that does not absorb or reflect incident light. Further, the first solar cell sub-module and the second solar cell sub-module are characterized in that they have a stripe type structure having the same width.
[0008]
As Conventional Example 3, a silicon-based thin-film solar cell having a two-terminal tandem structure in which a plurality of semiconductor junctions having different forbidden band widths are stacked on one substrate and optically and electrically connected in series is known. (See Patent Document 3).
[0009]
This silicon-based thin-film solar cell has two PIN junctions (a top cell on the light incident side and a bottom cell on the light reflection side) stacked on one substrate, and the second I-type layer is first intrinsically or substantially. After forming an intrinsic amorphous semiconductor, it is irradiated with strong light to be crystallized, and the first and second semiconductor materials are morphologically different even if they are the same, that is, the first is amorphous, and the second is amorphous. It is characterized in that a difference of 0.15 eV or more is given to the band gap Eg of the I-type film without using expensive germane (GeH4) by crystallization. The first PIN-junction amorphous silicon-based semiconductor absorbs short-wavelength light well to generate photocurrent, and the second PIN-junction crystalline semiconductor well absorbs long-wavelength light to generate photocurrent. .
[0010]
As Conventional Example 4, a silicon-based thin-film solar cell having the same two-terminal tandem structure as Conventional Example 3 is known (see Patent Document 4).
[0011]
FIG. 2 shows a schematic sectional view of this silicon-based thin-film solar cell. According to this figure, it includes an oxide transparent electrode 12, at least one amorphous photoelectric conversion unit 20, at least one crystalline photoelectric conversion unit 30, and a back electrode 40, which are sequentially stacked on a transparent glass substrate 11, The transparent oxide electrode 12 and the crystalline photoelectric conversion unit 30 have an uneven surface structure.
[0012]
Here, one amorphous photoelectric conversion unit 20 is composed of one conductivity type layer 21, amorphous photoelectric conversion layer 22, and reverse conductivity type layer 23, and one crystalline photoelectric conversion unit 30 is one conductivity type layer 31. The back surface electrode 40 is composed of the oxide transparent conductive layer 41 and the metal layer 42. Further, a light-transmitting conductive layer called an intermediate layer may be inserted between the amorphous photoelectric conversion unit 20 and the crystalline photoelectric conversion unit 30.
[0013]
In the amorphous photoelectric conversion unit 20, short-wavelength light is better absorbed and a photocurrent is generated, and in the crystalline photoelectric conversion unit 30, long-wavelength light is better absorbed and a photocurrent is generated. Further, the boundary between the transparent electrode and the amorphous photoelectric conversion film is made uneven by crystal grains of the transparent electrode, and the boundary between the crystalline photoelectric conversion film and the back electrode is also made uneven by the crystal grains of the crystalline photoelectric conversion film. The light confinement effect of these two spontaneous irregularities is obtained, and the photocurrent is increased in both units. It is difficult to obtain high conversion efficiency with one photoelectric conversion unit, and two or more photoelectric conversion units having different forbidden band widths are stacked, and furthermore, high conversion efficiency is achieved by the light confinement effect due to unevenness of each photoelectric conversion unit film surface. Trying to get.
[0014]
In this two-terminal tandem structure, in order to obtain the maximum efficiency, it is necessary to optimize the two photoelectric conversion units so that the photoelectric currents of the two photoelectric conversion units coincide with each other to make the two photoelectric conversion units the optimal operating points. More specifically, optimization design is performed by adjusting the film quality, film thickness, irregularities, etc., based on the invasion light intensity of both photoelectric conversion units, and a method of realizing these optimum values by repeated experiments is taken. The insertion of the intermediate layer makes it easier to adjust the photocurrent of both photoelectric conversion units and is used for optimizing the operation.
[0015]
As Conventional Example 5, a tandem-type thin film photoelectric conversion device in which Conventional Example 4 is integrated is known (see Patent Document 5). It is separated by a plurality of substantially straight and parallel separation grooves to form a plurality of tandem photoelectric conversion cells, the plurality of cells being separated by the separation grooves, The cells are electrically connected in series to each other via a plurality of connection grooves parallel to the separation groove, and are integrated on one substrate.
[0016]
When a thin-film photoelectric conversion device having a single substrate is actually used as a solar cell as in Conventional Examples 3, 4, and 5, a back sheet or the like is adhered to the back electrode side of the substrate with a sealing resin, and the substrate is resistant to heat. Consideration is given to environmental characteristics.
[0017]
Further, as a conventional example 6, a solar cell panel in which a heat insulating material is adhered between a back electrode of a single cell and a back sheet is known (see Patent Document 6).
[0018]
Further, as a conventional example 7, a thin-film solar cell module in which a heat insulating layer is provided on the back surface of a single cell is known (see Patent Document 7).
[0019]
Further, as a conventional example 8, a thin-film solar cell module in which a vacuum heat insulating layer is provided on the back surface of a single cell is known (see Patent Document 8).
[0020]
Further, as a conventional example 9, a solar cell module provided with a foam in a single cell is known (see Patent Document 9).
[0021]
[Patent Document 1]
Japanese Patent Publication No. 5-27278
[Patent Document 2]
JP-A-1-68997
[Patent Document 3]
Japanese Patent Publication No. 5-25187
[Patent Document 4]
JP 2001-217440 A
[Patent Document 5]
JP-A-11-186585
[Patent Document 6]
JP-A-7-297435
[Patent Document 7]
JP 2002-111037 A
[Patent Document 8]
JP 2002-111026 A
[Patent Document 9]
JP-A-9-191121
[0022]
[Problems to be solved by the invention]
In Conventional Example 1, both of the two amorphous silicon-based semiconductors have a problem of light deterioration, and the total output obtained from these two cells causes a decrease in output corresponding to the sum of the respective light deteriorations. There was a problem. Further, the first semiconductor is amorphous silicon having a high light absorptivity for short-wavelength light, and there is no need to use a light confinement structure. Patent Document 1 does not disclose any unevenness of the photoelectric conversion surface. . In addition, the second semiconductor is an amorphous silicon-germanium having a high light absorptivity for long-wavelength light, and there is no need to use a light confinement structure. It has not been. In addition, an inert gas is sealed between the two substrates. However, both the first and second semiconductors are made of amorphous silicon which is photo-degraded. Patent Document 1 does not disclose any deterioration suppressing effect.
[0023]
In the conventional example 2, the first semiconductor is made of hydrogenated amorphous silicon, the second semiconductor is made of polycrystalline silicon, and the polycrystalline silicon may be a thin-film polycrystalline silicon recrystallized by annealing or the like. However, Patent Document 2 does not refer to any light confinement structure such as unevenness of the first and second photoelectric conversion surfaces, and determines whether or not the recrystallized thin-film polycrystalline silicon has surface unevenness. It is not clear whether the size is on the order of the wavelength of light. The presence or absence of this light confinement structure has an important effect on the future improvement of the conversion efficiency of the thin-film photoelectric conversion device, and is a necessary structure for the thin-film photoelectric conversion layer. Similarly, Patent Document 2 does not mention at all the light confinement structure such as the unevenness of the photoelectric conversion surface made of the first hydrogenated amorphous silicon. Further, the optical coupler is made of an electrically insulating material that does not absorb or reflect incident light. However, this cannot reduce the thickness of the hydrogenated amorphous silicon as the first semiconductor and cannot suppress light degradation. Also. The first solar cell submodule made of the first hydrogenated amorphous silicon has a problem of light deterioration, and has a problem of causing a decrease in output.
[0024]
In Conventional Example 3, the first cell was amorphous and had a problem of light degradation. Although the second cell is not considered to be photo-degraded due to crystallization, since the first and second photoelectric conversion cells are connected in series, their currents must be equal in terms of a circuit. There is a problem that the second cell is also affected by the photodeterioration of the cell, and the photocurrent is reduced. Further, if the second semiconductor is made of crystalline silicon having a low light absorptivity for long-wavelength light, the photocurrent of the second cell is small, and the efficiency of the whole series connection is low. The second cell has no light confinement structure such as unevenness of the photoelectric conversion surface.
[0025]
In the photoelectric conversion device having a thin-film two-terminal tandem structure of Conventional Example 4, since the first and second photoelectric conversion cells are connected in series, the photocurrent generated in the first photoelectric conversion cell and the second photoelectric conversion The photocurrent generated in the cell must be equal and this photocurrent must be the optimal operating point for each of these two electromotive cells. If these are not equal, only the smaller photocurrent, which is limited by the photoelectric conversion cell having the smaller photocurrent, can be taken out to the outside, which lowers the efficiency of the whole thin-film electromotive device.
[0026]
For this reason, conventionally, the unevenness for the light confinement effect together with the wavelength and intensity of the penetrating light, the film quality and the thickness of the PIN semiconductor film, and the like so that the photocurrents generated in the first and second photoelectric conversion cells are equal. Adjustment of such parameters has been performed, but complicated adjustment is required because of the large number of parameters. Although many adjustment parameters can be adjusted, there is a problem that many parameters are susceptible to the influence of the parameters.
[0027]
This has resulted in design difficulties and manufacturing difficulties. In other words, the design requires advanced simulation technology for a large number of parameters, and the manufacturing requires advanced manufacturing technology to ensure manufacturing stability and uniformity. It was difficult to provide batteries. In particular, it is very difficult to stably and uniformly manufacture these parameters in manufacturing, and these parameters always have a central value variation between manufacturing lots and in-plane variations between manufacturing lots and between lots. In all of the above-mentioned cases, the central value fluctuation of the photocurrent generated between the production lots and the in-plane variation of the photocurrent generated within the production lot and between the lots occurred in both cells. All of these variations are the rate-limiting factor of the photocurrent and cause problems such as a decrease in conversion efficiency and a decrease in yield, and there has been a major problem as a solar cell in which cost reduction per output cannot be easily realized.
[0028]
In addition to these parameters, it is known that the amorphous silicon-based semiconductor in the top cell has a photodegradation phenomenon, and the crystalline silicon-based semiconductor in the bottom cell does not undergo photodegradation. As a result, there is a problem in that the photocurrent of the bottom cell has to be reduced in terms of the circuit, which makes it difficult to optimize and lowers the efficiency.
[0029]
The intermediate film is used to enhance the reflection of short-wavelength light and to reduce the thickness of the top cell to suppress light degradation. It has problems of center value fluctuation and in-plane variation, and furthermore makes manufacturing difficult. Although a photocurrent can be output from this intermediate film, it is present in the multilayer film, and it is difficult to provide an extraction electrode in the film.
[0030]
In addition, since the first cell and the second cell are stacked directly or via a thin intermediate layer, the two cells cannot be thermally separated from each other. The second cell has a tendency to decrease in efficiency due to light degradation, while the second cell has a tendency to increase efficiency while the first cell has a tendency to deteriorate light degradation in low-temperature actual use. .
[0031]
As the first irregularities formed on the surface of the first light-transmitting conductive film in contact with the amorphous silicon-based semiconductor, spontaneous irregularities due to polycrystallization of the light-transmitting conductive film are usually used. Due to the deposition of the amorphous silicon-based semiconductor film on the uneven surface and the continuous deposition of the crystalline silicon-based semiconductor film, the amorphous silicon-based semiconductor film changes to the spontaneous unevenness. It was not always possible to change the shape of the dragging and light reflecting surface into an uneven shape suitable for long-wavelength light.
[0032]
In addition, due to the deposition of the amorphous silicon-based semiconductor film and the continuous deposition of the crystalline silicon-based semiconductor film, during the deposition of the crystalline silicon-based semiconductor film, mutual diffusion of impurities occurs at the PIN junction of the amorphous silicon-based semiconductor film. For example, it causes the diffusion of metal from the conductive film in contact with the amorphous silicon-based semiconductor film, thereby lowering the photoelectric conversion. In addition, since the long-wavelength light is sufficiently absorbed to generate a photocurrent, the thickness of the crystalline silicon-based semiconductor film is larger than the thickness of the amorphous silicon-based semiconductor film, and the deposition time of the crystalline silicon-based semiconductor film is not long. The diffusion time is longer than the deposition time of the amorphous silicon-based semiconductor film, and these diffusion problems are likely to occur.
[0033]
For this reason, conventionally, a diffusion suppression film has been inserted between the PIs of the amorphous photoelectric conversion film to suppress the diffusion of boron (B). However, a complicated film configuration is required, and the production is performed as described above. Was causing the above problems.
[0034]
In the conventional example 5, the tandem type thin film photoelectric conversion devices of the conventional example 4 are integrated in series, the photocurrents generated in the respective integrated tandem type unit cells are equal, and these photocurrents are respectively If the tandem-type unit cell is not the optimal operating point, high conversion efficiency cannot be obtained by integration.
[0035]
Also, the in-plane variation of some of the above-mentioned parameters tends to increase with an increase in area, and the in-plane variation of these parameters becomes a rate-limiting factor of photocurrent due to serial connection, and conversion efficiency is reduced by integration. There was a problem. This is a serious problem in a thin-film type photoelectric conversion device that has a feature of reducing the cost by increasing the area.
[0036]
In the method of manufacturing a thin film photoelectric conversion device, in the case of Conventional Example 4 having a two-terminal tandem structure, continuous film formation is performed using an in-line type chemical vapor deposition apparatus while avoiding exposure to air during deposition of a thin film semiconductor. Since the film thickness of an amorphous silicon-based semiconductor is different from that of a crystalline silicon-based semiconductor by about an order of magnitude, there is a large difference in film formation time. Had become.
[0037]
In the conventional examples 6 to 8, a heat insulating material, a vacuum heat insulating layer, and a foam are provided to suppress the optical degradation of the amorphous silicon semiconductor, but all of them are installed on the back side of the single cell. Yes, not an effective configuration for tandem cells.
[0038]
The present invention has been made in view of such circumstances, and eliminates a complicated design adjustment between tandem cells, and reduces a central value variation of a parameter depending on a manufacturing lot and an adverse effect of an in-plane variation. The purpose is to provide. Another object of the present invention is to provide a thin-film photoelectric conversion device free from light deterioration by forming the first element (cell) and the second element (cell) with a crystalline silicon-based semiconductor. Further, the unevenness can be designed and manufactured independently for the first element (cell) and the second element (cell), and further, effective light confinement is provided between the first element and the second element. It is an object to provide a thin-film photoelectric conversion device having high conversion efficiency by providing a structure. In addition, by separating the manufacture of the first element and the second element, or by eliminating or reducing the role of the step of inserting a diffusion suppressing layer or the like, manufacturing is facilitated and low conversion cost and high conversion efficiency are achieved. It is an object to provide a thin-film photoelectric conversion device.
[0039]
Another object is to provide a thin-film photoelectric conversion device having an integrated structure with high conversion efficiency.
[0040]
Further, by providing a close layer having high light reflectance for a short wavelength between the first and second elements, the thickness of the first crystalline silicon-based semiconductor layer can be reduced, and the first photoelectric conversion can be performed. It is an object of the present invention to provide a thin-film photoelectric conversion device in which an element has a high light transmittance for a long wavelength.
[0041]
Further, a thin-film photoelectric conversion device capable of reducing a decrease in efficiency due to a rise in temperature of a second crystalline silicon-based semiconductor layer by providing the close contact layer having high heat insulation between the first and second elements. With the goal.
[0042]
Further, it is another object of the present invention to provide a thin-film photoelectric conversion device which eliminates a back sheet, can be reduced in cost, and has excellent environmental resistance.
[0043]
[Means for Solving the Problems]
In order to achieve the above object, a thin film photoelectric conversion device of the present invention includes a first thin film photoelectric conversion element including a first substrate having a light-transmitting property and a second substrate having a conductive surface. A second thin-film photoelectric conversion element facing each other so that the two substrates are located on the outside; and the first thin-film photoelectric conversion element has a first light-transmitting property on the first substrate. A conductive layer, a first one-conductivity-type silicon-based semiconductor layer, a substantially intrinsic crystalline silicon-based semiconductor layer having an uneven surface, a first reverse-conductivity-type silicon-based semiconductor layer, and a second light-transmitting layer The second thin-film photoelectric conversion element is formed on the second substrate by a second one-conductivity-type silicon-based semiconductor layer, which is substantially intrinsic and has an uneven surface. Crystalline silicon-based semiconductor layer, second reverse-conductivity-type silicon-based semiconductor layer, and third light-transmitting layer The first thin-film photoelectric conversion element and the second thin-film photoelectric conversion element have a close layer including a light-transmitting resin layer or a heat-insulating gas layer interposed between the first thin-film photoelectric conversion element and the second thin-film photoelectric conversion element. It is characterized by.
In particular, the first crystalline silicon-based semiconductor layer has a spontaneous uneven portion formed by crystalline columnar deposition, and the second translucent conductive layer formed on the spontaneous uneven portion and the second light transmissive layer. The light confinement effect is enhanced by the concavo-convex configuration with the close contact layer on the conductive conductive layer.
[0044]
In particular, the second crystalline silicon-based semiconductor layer has a spontaneous uneven portion formed by crystalline columnar deposition, and the third light-transmitting conductive layer formed on the spontaneous uneven portion and the third light-transmitting portion. The light confinement effect is enhanced by the concavo-convex configuration with the close contact layer on the conductive conductive layer.
[0045]
In particular, the surface of the second substrate in contact with the second crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has an uneven shape.
[0046]
In particular, at least the surface of the first light-transmitting conductive layer or the surface of the first substrate that is in contact with the first crystalline silicon-based semiconductor layer and the first one-conductivity-type silicon-based semiconductor layer has an uneven shape. It is characterized by the following.
[0047]
In particular, the surface of the second substrate in contact with the second crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has irregularities, and the first crystalline silicon-based semiconductor and At least the surface of the first light-transmitting conductive layer or the surface of the first substrate in contact with the first one-conductivity-type silicon-based semiconductor layer has an uneven shape, and the height of the uneven portion on the surface of the second substrate is high. The difference and the pitch are larger than the height difference and the pitch of the uneven portion on the surface of the first substrate.
[0048]
In particular, the first crystalline silicon-based semiconductor layer and the second crystalline silicon-based semiconductor layer are each deposited under unique film forming conditions without being continuously deposited by a chemical vapor deposition method. And
[0049]
More particularly, the thickness of the second crystalline silicon-based semiconductor layer is larger than the thickness of the first crystalline silicon-based semiconductor layer.
[0050]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the thin-film photoelectric conversion device of the present invention.
[0051]
As shown in FIG. 1, a thin-film photoelectric conversion device 1 includes a first thin-film photoelectric conversion element 20 having a first substrate 10 having a light-transmitting property and a second thin-film photoelectric conversion element having a second substrate 50. The conversion element 70 has a mechanical stack type structure in which the two substrates 11 and 50 are placed outside and facing each other.
[0052]
Here, the first thin-film photoelectric conversion element 20 is, on the light-transmitting substrate 11, sequentially a first light-transmitting conductive layer 12, a first one-conductivity-type silicon-based semiconductor layer 21, and is substantially intrinsic. A second thin-film photoelectric conversion element is formed by laminating a crystalline silicon-based semiconductor layer 22 having surface irregularities of columnar growth, a first reverse-conductivity-type silicon-based semiconductor layer 23, and a second light-transmitting conductive layer 30. Reference numeral 70 denotes a second one-conductivity-type silicon-based semiconductor layer 71, substantially on a conductive substrate 60 as a second substrate or on an insulating substrate 50 as a second substrate provided with a conductive layer 61. A second crystalline silicon-based semiconductor layer 72, a second reverse-conductivity-type silicon-based semiconductor layer 73, and a third light-transmitting conductive layer 80, each of which has an intrinsically intrinsic columnar growth surface irregularity, The close contact layer 90 between the two thin-film photoelectric conversion elements may be, for example, a light-transmitting resin layer 90. Ku is made of a transparent resin layer 91 and the thermal insulation gas layer 92.
[0053]
Thereby, for example, even if the center of the first crystalline silicon-based semiconductor film 22 has a variation in the center value or an in-plane variation in the film thickness of the first thin-film photoelectric conversion element 20, this is caused by the second thin-film photoelectric conversion element 70. By shifting the first thin-film photoelectric conversion element 20 to the optimum operating point without being related to the photovoltaic power, the overall conversion efficiency does not decrease and the conversion efficiency is higher than that of the conventional technique. The same applies to the film quality. In addition, design adjustment of these parameters between the two cells and advanced simulation technology are not required, and advanced manufacturing technology is not required.
[0054]
The first thin-film photoelectric conversion element 20 and the second thin-film photoelectric conversion element 70 include a first crystalline silicon-based semiconductor layer 22 and a second crystalline silicon-based semiconductor layer 72, respectively. Since a high-quality silicon-based semiconductor is not used, there is no light deterioration, and the conversion efficiency after light stabilization is higher than that of the prior art.
[0055]
Further, an adhesion layer 90 mainly including a heat insulating gas layer (including a reduced pressure gas layer or a vacuum layer) between the first and second thin film photoelectric conversion elements, or as shown in FIG. By providing a close contact layer 90 having a large refractive index difference composed of a mixed layer of a gas and a translucent resin material, or a close contact layer 90 having a parallel layer with a light resin layer, Due to the heat insulating effect caused by the gas component of the close contact layer 90, a temperature rise of the second crystalline silicon-based semiconductor layer 72 is suppressed, and a decrease in efficiency due to a temperature rise of the second thin film photoelectric conversion element is suppressed. Here, the adhesive layer 90 is formed by using a liquid adhesive such as silicone, for example, taking in bubbles while stirring the liquid, and performing a curing step by heating without performing vacuum defoaming of the adhesive or decompression during the bonding step. It may be formed. Further, using a solid sheet adhesive such as EVA (ethylene-vinyl acetate copolymer resin) or PVB (polyvinyl butyral), a layer in which a gas layer is mixed in a solid-state sheet in advance by a punching step, or a ring-shaped layer It may be. In addition, as other resin materials, an ethylene-methyl acrylate copolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), a fluororesin, or the like can be considered.
[0056]
In addition, by providing the close contact layer 90 made of the light-transmitting resin layer 90 as described above, light reflection to the first crystalline silicon-based semiconductor layer is increased, and the first crystalline silicon-based semiconductor layer 22 The film thickness can be reduced, and the manufacturing cost of the first thin-film photoelectric conversion element 20 can be reduced.
[0057]
That is, when the close contact layer 90 is mainly a heat insulating gas layer, the refractive index difference and the heat insulating property are large and more effective. In addition, when the heat insulating gas layer is a reduced pressure gas layer or a vacuum layer, the refractive index difference and the heat insulating property are large and more effective. When the close contact layer 90 is a parallel layer of a gas layer for heat insulation and a light-transmitting resin layer, in addition to the effect of the gas layer for heat insulation, the gap between the two elements can be fixed by the light-transmitting resin layer, and the thin film photoelectric conversion can be performed. The mechanical stability of the device can be maintained. In particular, it is convenient to fix the outer periphery in the case of a non-integrated cell and fix the separation groove in the case of an integrated cell without adversely affecting efficiency. When the close contact layer 90 is a mixed layer of a gas and a light-transmitting resin material, the gap can be fixed on the entire surface and mechanical strength can be provided, and the repetition of the gas and the light-transmitting resin material can be performed in the order of the wavelength of light. By doing so, the light reflectance can be increased.
[0058]
Further, in the thin film photoelectric conversion device of the present invention, the first crystalline silicon-based semiconductor layer 22 has a spontaneous uneven portion formed by crystalline columnar deposition, and the second light-transmitting conductive layer formed on the spontaneous uneven portion. 30 and a heat insulating gas layer (including a reduced pressure gas layer or a vacuum layer) on the second light transmitting conductive layer 30, or a parallel layer of a heat insulating gas layer and a light transmitting resin layer, or a gas and light transmitting layer The concavo-convex configuration with the close contact layer 90 made of a mixed layer of a resin material can enhance the light confinement effect. Here, the degree of the spontaneous irregularities can be expressed by the volume crystallization ratio of silicon. That is, crystal growth in a certain direction in a columnar manner from the substrate (referred to as orientation) results in a protruding and irregular surface shape, and between these columnar microcrystalline phases is an amorphous phase, and the degree of spontaneous irregularities is the crystal phase / It is almost proportional to the magnitude of the volume crystallization ratio (%), which is the ratio of (crystal phase + amorphous phase). Generally, the case where the volume crystallization ratio is 60% or more is referred to as spontaneous unevenness, and the case where the volume crystallization ratio is less than 60% is referred to as non-self-generated unevenness.
[0059]
As a result, an uneven surface is further obtained at an intermediate position of the laminated structure, which has not existed conventionally, and selective incidence, reflection, refraction and absorption of light become more active in the first and second thin film photoelectric conversion elements 20 and 70. By improving the light confinement effect, the conversion efficiency is improved as compared with the related art.
[0060]
Further, in the thin film photoelectric conversion device of the present invention, the second crystalline silicon-based semiconductor layer 72 has a spontaneous uneven portion formed by crystalline columnar deposition, and the third light-transmitting conductive layer formed on the spontaneous uneven portion. 80 and a heat insulating gas layer (including a reduced pressure gas layer or a vacuum layer) on the third light transmitting conductive layer 80, or a parallel layer of a heat insulating gas layer and a light transmitting resin layer, or a gas and light transmitting The concavo-convex configuration with the close contact layer 90 made of a mixed layer of a conductive resin material can enhance the light confinement effect.
[0061]
As a result, an uneven surface is further obtained at an intermediate position of the laminated structure, which has not existed conventionally, and selective incidence, reflection, refraction and absorption of light become more active in the first and second thin film photoelectric conversion elements 20 and 70. By improving the light confinement effect, the conversion efficiency is improved as compared with the related art.
[0062]
In addition, the thin-film photoelectric conversion device according to the present invention includes an insulating layer provided with the surface of the conductive substrate 60 or the conductive layer 61 in contact with the second crystalline silicon-based semiconductor layer 72 and the second one-conductivity-type silicon-based semiconductor layer 71. The surface of the substrate 50 is uneven.
[0063]
As a result, an uneven surface is obtained at the back position of the laminated structure, and light reflection and absorption become more active particularly in the second thin-film photoelectric conversion element 70, and the conversion efficiency is improved by increasing the light confinement effect. Bring. In addition, since the concavities and convexities can be newly formed on the conductive substrate 60 or the insulating substrate 50 as the second substrate, the degree of freedom and ease of forming the concavities and convexities can be obtained, and the conversion efficiency is higher than in the past. Bring.
[0064]
In addition, the thin film photoelectric conversion device of the present invention provides at least the surface of the first transparent conductive layer 12 or the first transparent silicon conductive layer 12 in contact with the first crystalline silicon-based semiconductor layer 22 and the first one-conductivity-type silicon-based semiconductor layer 21. The surface of the substrate 11 has irregularities. As a result, an uneven surface is obtained at the incident position of the laminated structure, and selective incidence, refraction, and absorption of light become more active particularly in the first photoelectric conversion element, and the conversion efficiency is improved by increasing the light confinement effect. Bring.
[0065]
Further, in the thin film photoelectric conversion device of the present invention, the first unevenness of the light-reflective conductive substrate 60 or the insulating substrate 50 including the conductive layer 61 in contact with the second crystalline silicon-based semiconductor layer 72 is different. And the pitch is larger than the height difference and the pitch of the second unevenness of the light transmitting substrate 11 or the first light transmitting conductive layer 12 in contact with the first crystalline silicon-based semiconductor layer 22. As a result, the first unevenness becomes more light-transmissive and the second unevenness becomes more light-reflective for long-wavelength light where light penetration is deeper than short-wavelength light, and the light confinement effect of long-wavelength light increases. This results in higher conversion efficiency. Here, the height difference and the pitch of the unevenness can be confirmed (measured) by cross-sectional TEM (transmission electron microscope) photograph or surface observation by AFM (atomic force microscope).
[0066]
Further, according to the thin-film photoelectric conversion device of the present invention, the first crystalline silicon-based semiconductor layer 22 and the second crystalline silicon-based semiconductor layer 72 are each independently formed without being continuously deposited by the chemical vapor deposition method. It is characterized by being deposited under film forming conditions.
[0067]
This makes it possible to independently form a film on each substrate under different film forming conditions or different film forming apparatuses, and the deposition of one PIN semiconductor film has an effect on the characteristics of the other PIN semiconductor film. There is no adverse effect. As a result, crystallization deposition suitable for each wavelength becomes easy, and furthermore, the first crystalline silicon-based semiconductor layer 22 on which the second crystalline silicon-based semiconductor layer 72 is deposited has an adverse effect such as impurity diffusion. Without any effect, between the first crystalline silicon semiconductor layer 22 and the first one-conductivity-type silicon-based semiconductor layer 21 or between the first one-conductivity-type silicon-based semiconductor layer 21 and the first transparent conductive layer 12 In addition, since high conversion efficiency can be obtained without providing a special diffusion suppressing film, a diffusion suppressing film is not required.
[0068]
In particular, the first crystalline silicon-based semiconductor layer 22 requiring short-wavelength sensitivity and the second crystalline silicon-based semiconductor layer 72 requiring long-wavelength sensitivity have optimum crystal grain size and crystallization ratio. Since the film qualities are different and different film forming apparatuses and film forming conditions are used, deposition with high film quality and high conversion efficiency can be performed. In addition, the first crystalline silicon-based semiconductor layer and the second crystalline silicon-based semiconductor layer have different film thicknesses and different deposition times, and the efficiency is improved by using different deposition devices. The production method becomes possible.
[0069]
According to the thin-film photoelectric conversion device of the present invention, the thin-film photoelectric conversion device according to claim 1, wherein the thickness of the second crystalline silicon-based semiconductor layer is equal to the thickness of the first crystalline silicon-based semiconductor layer. It is characterized by being larger than the thickness of the semiconductor layer.
[0070]
As a result, short-wavelength light that is easily absorbed is better absorbed in the first crystalline silicon-based semiconductor layer 22, and long-wavelength light that is hardly absorbed is better absorbed in the second crystalline silicon-based semiconductor layer 72. Therefore, it is not necessary to use semiconductors having different forbidden bandwidths as in the related art. In particular, it is not possible to obtain a high open-circuit voltage of the first cell (top cell) having a large forbidden band width as in the prior art. However, even with a semiconductor having the same forbidden band width, the light confinement effect due to the unevenness is obtained. Accordingly, the first thin-film photoelectric conversion element 20 having a large short-circuit current can be obtained.
[0071]
As described above, the short-wavelength light is rapidly attenuated, and the solar energy distribution can be more effectively reduced when the thickness of the first crystalline silicon-based semiconductor layer is smaller than that of the second crystalline silicon-based semiconductor layer. Available and convenient.
[0072]
【Example】
Hereinafter, Examples 1 to 4 showing the present invention more specifically will be described.
<Example 1>
Description will be made by taking the thin-film photoelectric conversion device 1 shown in FIG. 1 as an example. As described above, reference numeral 11 denotes a translucent substrate. In this embodiment, a white plate glass (thickness: 1.8 mm) having flat surfaces on both sides is used. As other translucent substrates, a transparent inorganic substrate such as blue plate glass or sapphire, or a transparent organic resin substrate such as polycarbonate may be used. Reference numeral 12 denotes a first light-transmitting conductive film. In this embodiment, an ITO (Indium Tin Oxide) film deposited by a sputtering method is used. As another method for producing the light-transmitting conductive film, a vacuum evaporation method, a spray pyrolysis method, an ion plating method, a dip coating method, a sol-gel method, or the like may be used. As another light-transmitting conductive film, a SnO 2 -based film, a ZnO-based film, an In 2 O 3 -based film, or the like doped with an impurity may be used, or a stack of these light-transmitting conductive films may be used. Reference numeral 20 denotes a crystalline silicon-based semiconductor film having a PIN junction, which is a hydrogenated microcrystalline silicon-based film. A PIN junction semiconductor is formed by laminating a P-type semiconductor film, an I-type semiconductor film, and an N-type semiconductor film, and is deposited by the plasma CVD method in this embodiment, but may be deposited by a catalytic CVD method or the like.
[0073]
In the present embodiment, a PIN junction in which a P-type semiconductor film is provided on the side of the first light-transmitting conductive film is used, but an NIP junction of a reverse junction may be used. If the I-type semiconductor film is crystalline microcrystalline or polycrystalline, the P-type semiconductor film and / or the N-type semiconductor film may be amorphous. Further, a hydrogenated microcrystalline silicon alloy-based film or a hydrogenated amorphous silicon alloy-based film may be used. For example, for the P film on the light incident side, hydrogenated amorphous silicon carbide is more preferable because it enhances the light transmission and reduces light penetration loss.
[0074]
In this embodiment, first, a PIN type semiconductor film was continuously deposited on the light-transmitting substrate with the first light-transmitting conductive film by a plasma CVD method. First, a P-type μc-Si: H semiconductor film was deposited at 200 ° (0.02 μm). Here, μc refers to a so-called microcrystalline material having a particle size of submicron or less. A P-type μc-SiC: H film may be used instead of the P-type μc-Si: H semiconductor. SiH 4, H 2 gas, and B 2 H 6 (diluted to 500 ppm with H 2) were used as source gases of P-type μc-Si: H, and the flow rates of these gases were 1 sccm, 200 sccm, and 10 sccm, respectively.
[0075]
Subsequently, an I-type semiconductor film was deposited at 10,000 ° (= 1 μm). SiH4 and H2 gases were used as source gases for I-type μc-Si: H, and the flow rates of these gases were 10 sccm and 100 sccm, respectively. The crystallization ratio of the I-type film was 70%, and spontaneous irregularities were formed on the growth surface.
[0076]
Further, an N-type a-Si: H semiconductor film was deposited at 120 °. SiH4, H2 gas, and PH3 (diluted to 1000 ppm with H2) were used as source gases of N-type a-Si: H, and the flow rates of these gases were 3 sccm, 30 sccm, and 6 sccm, respectively. The substrate temperature was 220 ° C. for all of the PIN films.
[0077]
Reference numeral 30 denotes a second light-transmitting conductive film, on which an ITO film was deposited by a sputtering method. As the other second light-transmitting conductive film, a SnO 2 -based film doped with impurities, a ZnO-based film, an In 2 O 3 -based film, or the like may be used, or a stacked film thereof may be used. Further, a collector electrode having an Ag film deposited thereon to form an electrode pattern such as a comb shape may be provided.
[0078]
Reference numeral 50 denotes an insulating substrate or a conductive substrate 60. In this embodiment, 1.8 mmt of soda lime glass, which is an insulating substrate, is used. As another substrate, an inorganic substrate such as various kinds of glass, an organic resin substrate such as polycarbonate, or a conductive substrate such as an aluminum substrate or a stainless steel substrate may be used.
[0079]
Reference numeral 61 denotes a light-reflective conductive film. In this example, a laminated film of Ti / Ag / Ti was used. The Ti film on the substrate side is for promoting adhesion, and the Ti film on the Ag film is for suppressing Ag diffusion into the semiconductor film. The Ag film has high light reflectivity, and high conversion efficiency is easily obtained. As other material configurations, Ti / Ag: Al alloy / ZnO: Al, Ti / Ag / ITO, Ag / ITO, and the like may be used.
[0080]
Reference numeral 70 denotes a crystalline silicon-based semiconductor film having a PIN junction, which is a microcrystalline silicon-based film having a relatively high crystallization ratio obtained by deposition by a plasma CVD method, a catalytic CVD method, or the like. And a PIN junction semiconductor formed by laminating an I-type semiconductor film and an N-type semiconductor film. If the I-type semiconductor film is microcrystalline, the P-type semiconductor film and the N-type semiconductor film may be microcrystalline or amorphous.
[0081]
In this example, NIP type semiconductor films were continuously deposited on the glass substrate with the light-reflective conductive film by a plasma CVD method. Although the NIP junction in which the N-type semiconductor film is provided on the light reflective conductive film side is used, a PIN junction of a reverse junction may be used. Alternatively, a microcrystalline silicon alloy-based film may be used. In this embodiment, a plasma CVD method is used. First, an N-type μc-Si: H semiconductor film was deposited at 100 °. SiH 4, H 2 gas, and PH 3 (diluted to 1000 ppm with H 2) were used as source gases for N-type μc-Si: H, and the flow rates of these gases were 2 sccm, 30 sccm, and 4 sccm, respectively. Subsequently, a 1.8 μm I-type μc-Si: H semiconductor film was deposited. SiH4 and H2 gases were used as source gases for I-type μc-Si: H, and the flow rates of these gases were set to 20 sccm and 100 sccm, respectively. The crystallization ratio of the I-type film was 70%, and spontaneous irregularities were formed on the growth surface. Further, a P-type a-Si: H semiconductor film was deposited at 90 °. Instead of the P-type a-Si: H semiconductor, a P-type a-SiC: H, a P-type μc-Si: H film, or a P-type μc-SiC: H film may be used. SiH4, H2 gas, and B2H6 (diluted to 500 ppm with H2) were used as source gases for P-type a-Si: H, and the flow rates of these gases were 2 sccm, 400 sccm, and 15 sccm, respectively. The substrate temperature was 240 ° C. for all of the NIP films.
[0082]
Reference numeral 80 denotes a third light-transmitting conductive film. In this embodiment, an ITO film is deposited by a sputtering method. As the other second light-transmitting conductive film, a SnO 2 -based film doped with impurities, a ZnO-based film, an In 2 O 3 -based film, or the like may be used, or a stacked film thereof may be used. Further, a collector electrode similar to the above may be formed thereon.
[0083]
Reference numeral 92 denotes a gas layer for heat insulation, which is an air layer in this embodiment. In addition to air, nitrogen or argon may be used. Vacuum is more preferable if the substrate is thick and the strength can be secured. Reference numeral 91 denotes a light-transmitting resin layer. In this example, a transparent sealing resin EVA (ethylene-vinyl acetate copolymer resin) was used. An EVA tape was sandwiched around the ends of both substrates, and a thin film photovoltaic element was produced by a process consisting of melting resin by heating, pressing EVA, thermosetting, primary cooling, and secondary cooling in a gas. .
[0084]
Four 1 cm-square elements were manufactured on a 5 cm-square substrate size at a distance of 2 cm from each other, and the conversion efficiency was an average value of four elements. For comparison, in the conventional structure shown in FIG. 2, a white plate glass (thickness: 1.8 mm) having flat surfaces on both sides was used, the top cell was made the same as the amorphous silicon semiconductor manufacturing conditions and the film thickness, and the bottom cell was made the above. An element was manufactured under the same manufacturing conditions and film thickness.
[0085]
100 mW / cm of the two types of photoelectric conversion devices thus obtained under AM1.5. ² As a result of the conversion efficiency after light stabilization, the conversion efficiency of the thin film electromotive device of Example 1 was 8.3%, while the conversion efficiency of the thin film electromotive device of Comparative Example 1 was 7.6%. It showed higher conversion efficiency.
<Example 2>
First, a first thin-film electromotive element substrate was manufactured in the same manner as in Example 1.
[0086]
In the production of the second thin film electromotive element base, 1.8 mmt of soda lime glass was used as 50 insulating substrates, and the surface thereof was subjected to sandblasting, and further treated with hydrofluoric acid and washed to form irregularities. The height difference and the pitch of the unevenness were about 250 nm to 350 nm and about 300 nm to 400 nm, respectively. On this substrate, 61 light-reflective conductive films, 70 crystalline silicon-based semiconductor films having an NIP junction, and 80 light-transmitting conductive films were sequentially formed under the same conditions as in Example 1. Then, the thin film electromotive device of the second embodiment was manufactured by setting the 90 close layers to the same configuration as the first embodiment. As a comparative example, the above-described comparative example 1 was used because there was no substrate to be subjected to substrate processing as in this example.
[0087]
100 mW / cm of the two types of photoelectric conversion devices thus obtained under AM1.5. ² As a result of the conversion efficiency after light stabilization, the conversion efficiency of the thin film electromotive device of Example 2 was 8.9%, while the conversion efficiency of the thin film electromotive device of Comparative Example 1 was 7.6%. It showed higher conversion efficiency.
<Example 3>
In this embodiment, a commercially available polycrystalline SnO2: F (fluorine-doped dioxide) is used to obtain 11 light-transmitting substrates and 12 first light-transmitting conductive films of the first thin film electromotive element substrate. A white plate glass with a (tin) film was used. The height difference and pitch of the spontaneous unevenness of the polycrystalline SnO2: F film were about 100 nm to 250 nm and about 200 nm to 300 nm, respectively, according to the TEM observation of the cross section. According to the AFM measurement, the arithmetic average roughness Ra was 26 nm, and the most frequent wavelength (most frequent pitch) of Power Spectral Density was 1.25 μm / cycle. Under the same conditions as in Example 1, a crystalline silicon-based semiconductor film having 20 PIN junctions and a 30 second light-transmitting conductive film were sequentially formed on the substrate. Then, a second thin-film electromotive element substrate was manufactured in the same manner as in Example 1.
[0088]
Then, a thin-film electromotive device was manufactured with a configuration in which the translucent resin of No. 91 was sandwiched in the same manner as in Example 1. As Comparative Example 3, a commercially available polycrystalline SnO2: F () was obtained in order to obtain 11 light-transmitting substrates and 12 first light-transmitting conductive films of the thin film electromotive element substrate as in this example. A white plate glass with a (fluorine-doped tin dioxide) film was used. A crystalline silicon-based semiconductor film having a PIN junction of 30 and a light-reflective conductive film of 40 were sequentially formed on a top cell having a PIN junction of 20 under the manufacturing conditions and thickness of an amorphous silicon semiconductor in Comparative Example 1. It was manufactured in the same way as.
[0089]
100 mW / cm of the two types of photoelectric conversion devices thus obtained under AM1.5. ² As a result of the conversion efficiency after light stabilization, the conversion efficiency of the thin film electromotive device of Example 3 was 8.6%, while the conversion efficiency of the thin film electromotive device of Comparative Example 3 was 7.9%. It showed higher conversion efficiency.
<Example 4>
In the fourth embodiment, the first thin-film electromotive element substrate is made of the same commercially available white plate glass with a polycrystalline SnO2: F (fluorine-doped tin dioxide) film as in the third embodiment, and the other conditions are the same. Made in. The second thin-film electromotive element substrate was manufactured under the same conditions using the same substrate as that of Example 2 except that the surface of the soda lime glass was subjected to sandblasting, further treated with hydrofluoric acid, and washed to form irregularities.
[0090]
Then, the thin film electromotive force device of the fourth embodiment was manufactured by sandwiching the translucent resin of 91 in the same manner as in the first embodiment. Comparative Example 4 was used as Comparative Example 4 because there was no substrate itself for sandblasting the substrate as in this example. 100 mW / cm of the two types of photoelectric conversion devices thus obtained under AM1.5. ² As a result of the conversion efficiency after light stabilization, the conversion efficiency of the thin film electromotive device of Example 4 was 9.3%, while the conversion efficiency of the thin film electromotive device of Comparative Example 3 was 7.9%. It showed higher conversion efficiency.
[0091]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the thin-film photoelectric conversion device of this invention, the bad influence of center value fluctuation | variation in a thin film manufacture, in-plane variation, etc. is reduced, the light confinement effect which consists of an uneven | corrugated structure is improved, and conversion efficiency is improved by a heat insulation structure. Area and cost can be reduced.
[0092]
According to the thin-film photoelectric conversion device of the present invention, neither the first thin-film photoelectric conversion element nor the second thin-film photoelectric conversion element uses a crystalline silicon-based semiconductor layer and does not use an amorphous silicon-based semiconductor. Therefore, there is no light deterioration.
[0093]
More specifically, according to the thin-film photoelectric conversion device of the first aspect, for example, even if the thickness of the crystalline silicon-based semiconductor film in the first thin-film photoelectric conversion element has a center value variation or an in-plane variation, this does not occur. The second thin-film photoelectric conversion element is independent of the photovoltaic power, and the first thin-film photoelectric conversion element is shifted to the optimum operating point, so that the conversion efficiency as a whole does not decrease and the conversion efficiency is higher than that of the prior art. . The same applies to the film quality. In addition, design adjustment of these parameters between the two cells and advanced simulation technology are not required, and advanced manufacturing technology is not required.
[0094]
In addition, by providing a close layer containing a gas component having a large difference in refractive index from the silicon-based semiconductor between the first and second thin-film photoelectric conversion elements, light reflection to the first crystalline silicon-based semiconductor layer is increased. In addition, the thickness of the first crystalline silicon-based semiconductor layer can be reduced, and the manufacturing cost of the first thin-film photoelectric conversion element can be reduced. Further, by providing a close layer containing a gas component between the first and second thin-film photoelectric conversion elements, the insulation between these elements is provided, so that the temperature of the second thin-film photoelectric conversion element in actual use of sunlight irradiation is increased. The purpose is to prevent the decrease in efficiency by suppressing the rise.
[0095]
Moreover, as an additional effect, when the close contact layer is mainly a heat insulating gas layer, the refractive index difference and the heat insulating property are large and more effective. Further, when the heat insulating gas layer is a gas layer of an inert gas or the like, a temporal change of the microcrystalline silicon layer (due to entry of oxygen or the like) can be completely eliminated. In addition, when the heat insulating gas layer is a reduced pressure gas layer or a vacuum layer, the refractive index difference and the heat insulating property are large and more effective. When the close contact layer is a parallel layer of the heat-insulating gas layer and the light-transmitting resin layer, in addition to the above-described effect of the heat-insulating gas layer, the light-transmitting resin layer can fix the gap between the two elements, and the thin-film photoelectric conversion device Can maintain mechanical stability. In particular, it is convenient to fix the outer periphery in the case of a non-integrated cell and fix the separation groove in the case of an integrated cell without adversely affecting efficiency. When the close layer is a mixed layer of a gas and a translucent resin material, the gap can be fixed on the entire surface and mechanical strength can be provided, and the repetition of the gas and the translucent resin material is on the order of the wavelength of light. This can increase the light reflectance.
[0096]
Further, according to the thin-film photoelectric conversion device of the second aspect, the first crystalline silicon-based semiconductor layer has a spontaneous uneven portion formed by crystalline columnar deposition, and the second light-transmitting portion formed on the spontaneous uneven portion. The concavo-convex structure of the conductive layer and the close layer containing the gas component on the second light-transmitting conductive layer can enhance the light confinement effect. As a result, an uneven surface is further obtained at an intermediate position of the laminated structure, which has not been conventionally provided, and selective incidence, reflection, refraction, and absorption of light become more active in the first and second thin-film photoelectric conversion elements. By improving the confinement effect, the conversion efficiency is improved as compared with the related art.
[0097]
Further, according to the thin film photoelectric conversion device of the third aspect, the second crystalline silicon-based semiconductor layer has a self-generated uneven portion formed by crystalline columnar deposition, and the third light-transmitting portion formed on the self-formed uneven portion. The concavo-convex structure of the conductive layer and the close layer containing the gas component on the third light-transmitting conductive layer can enhance the light confinement effect. As a result, an uneven surface is further obtained at an intermediate position of the laminated structure, which has not been conventionally provided, and selective incidence, reflection, refraction, and absorption of light become more active in the first and second thin-film photoelectric conversion elements. By improving the confinement effect, the conversion efficiency is improved as compared with the related art.
[0098]
Further, according to the thin-film photoelectric conversion device of the fourth aspect, the insulating film provided with the surface of the conductive substrate or the conductive layer in contact with the second crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer. The surface of the substrate is uneven. As a result, an uneven surface is obtained at the rear position of the laminated structure, and light reflection and absorption become more active particularly in the second thin film photoelectric conversion element, and the light confinement effect is increased, thereby improving the conversion efficiency. . In addition, since the uneven portion can be newly formed on the conductive substrate or the insulating substrate as the second substrate, the degree of freedom and ease of forming the unevenness can be obtained, and a higher conversion efficiency than the conventional one can be obtained. Bring.
[0099]
According to the thin-film photoelectric conversion device of claim 5, at least the surface of the first light-transmitting conductive layer or the first light-transmitting conductive layer in contact with the first crystalline silicon-based semiconductor layer and the first one-conductivity-type silicon-based semiconductor layer. The surface of the substrate 11 has irregularities. As a result, an uneven surface is obtained at the incident position of the laminated structure, and selective incidence, refraction, and absorption of light become more active particularly in the first photoelectric conversion element, and the conversion efficiency is improved by increasing the light confinement effect. Bring.
[0100]
Further, according to the thin film photoelectric conversion device of the sixth aspect, the first unevenness (the difference between the height and the height) of the light-reflective conductive substrate in contact with the second crystalline silicon-based semiconductor layer or the insulating substrate having the conductive layer. (Pitch) is larger than the second unevenness (height difference and pitch) of the light-transmitting substrate or the first light-transmitting conductive layer in contact with the first crystalline silicon-based semiconductor layer. As a result, the first unevenness becomes more light-transmissive and the second unevenness becomes more light-reflective for long-wavelength light where light penetration is deeper than short-wavelength light, and the light confinement effect of long-wavelength light increases. This results in higher conversion efficiency.
[0101]
Further, according to the thin film photoelectric conversion device of the seventh aspect, the first crystalline silicon-based semiconductor layer and the second crystalline silicon-based semiconductor layer are independently formed without being continuously deposited by the chemical vapor deposition method. It is characterized by being deposited under film conditions. This makes it possible to independently form a film on each substrate under different film forming conditions or different film forming apparatuses, and the deposition of one PIN semiconductor film has an effect on the characteristics of the other PIN semiconductor film. There is no adverse effect. Further, the required spectral sensitivity is different between the first crystalline silicon-based semiconductor layer and the second crystalline silicon-based semiconductor layer, and improvement in conversion efficiency is expected by using different film forming apparatuses. it can. In particular, the first crystalline silicon-based semiconductor layer and the second crystalline silicon-based semiconductor layer have different film thicknesses and different film-forming times, and the efficiency is improved by using different film-forming apparatuses. Production method becomes possible.
[0102]
According to the thin-film photoelectric conversion device of the eighth aspect, the thickness of the second crystalline silicon-based semiconductor layer is larger than the thickness of the first crystalline silicon-based semiconductor layer. As a result, short-wavelength light that is easily attenuated is well absorbed by the thin first crystalline silicon-based semiconductor layer, and long-wavelength light that is hardly attenuated is well absorbed by the thick second crystalline silicon-based semiconductor layer. Brings increased efficiency.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically illustrating one embodiment of a thin-film photoelectric conversion device according to the present invention.
FIG. 2 is a cross-sectional view illustrating an example of a conventional thin-film photoelectric conversion device.
[Explanation of symbols]
1: Thin-film photoelectric conversion device
10: translucent substrate (first substrate)
11: Translucent substrate
12: first light-transmitting conductive layer
20: First thin film photoelectric conversion element
21: First one conductivity type silicon-based semiconductor layer
22: first crystalline silicon-based semiconductor layer
23: first reverse conductivity type silicon-based semiconductor layer
30: Second translucent conductive layer
50: insulating substrate
60: conductive substrate (second substrate)
61: conductive layer
70: Second thin film photoelectric conversion element
71: Second one-conductivity-type silicon-based semiconductor layer
72: second crystalline silicon-based semiconductor layer
73: second reverse conductivity type silicon-based semiconductor layer
80: Third translucent conductive layer
90: Close layer
91: Translucent resin layer
92: Gas layer for heat insulation

Claims (8)

A first thin-film photoelectric conversion element provided with a first substrate having a light-transmitting property and a second thin-film photoelectric conversion element provided with a second substrate having a conductive surface, wherein the two substrates are located outside. Wherein the first thin-film photoelectric conversion element comprises a first light-transmitting conductive layer, a first one-conductivity-type silicon on the first substrate. System semiconductor layer, a first intrinsic crystalline silicon-based semiconductor layer having an uneven surface, a first reverse-conductivity-type silicon-based semiconductor layer, and a second light-transmitting conductive layer are sequentially stacked. And the second thin-film photoelectric conversion element comprises a second one-conductivity-type silicon-based semiconductor layer on the second substrate, a second intrinsic crystalline silicon-based semiconductor layer having an uneven surface. A semiconductor layer, a second opposite conductivity type silicon-based semiconductor layer, and a third light-transmitting conductive layer are sequentially stacked; And a close-contact layer including a light-transmitting resin layer or a heat-insulating gas layer is interposed between the first thin-film photoelectric conversion element and the second thin-film photoelectric conversion element. Conversion device. 2. The thin-film photoelectric conversion device according to claim 1, wherein the first crystalline silicon-based semiconductor layer has a spontaneous uneven portion formed by crystalline columnar deposition, and the second transparent semiconductor formed on the spontaneous uneven portion. 3. A thin-film photoelectric conversion device, wherein a light confinement effect is enhanced by a concavo-convex structure of a photoconductive layer and the close contact layer on the second translucent conductive layer. 2. The thin-film photoelectric conversion device according to claim 1, wherein the second crystalline silicon-based semiconductor layer has a spontaneous uneven portion formed by crystalline columnar deposition, and the third transparent semiconductor formed on the spontaneous uneven portion. 3. A thin-film photoelectric conversion device, wherein a light confinement effect is enhanced by a concavo-convex structure of a photoconductive layer and the close layer on the third light-transmitting conductive layer. 2. The thin-film photoelectric conversion device according to claim 1, wherein a surface of the second substrate in contact with the second crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has an uneven shape. A thin-film photoelectric conversion device. 2. The thin-film photoelectric conversion device according to claim 1, wherein at least a surface of the first light-transmitting conductive layer in contact with the first crystalline silicon-based semiconductor layer and the first one-conductivity-type silicon-based semiconductor layer or The thin-film photoelectric conversion device, wherein the surface of the first substrate has an uneven shape. 2. The thin-film photoelectric conversion device according to claim 1, wherein a surface of the second substrate in contact with the second crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has an uneven shape. 3. At least the surface of the first light-transmitting conductive layer or the surface of the first substrate that is in contact with the first crystalline silicon-based semiconductor and the first one-conductivity-type silicon-based semiconductor layer has an uneven shape; A thin film photoelectric conversion device, wherein a height difference and a pitch of the uneven portion on the surface of the second substrate are larger than a height difference and a pitch of the uneven portion on the surface of the first substrate. 2. The thin-film photoelectric conversion device according to claim 1, wherein the first crystalline silicon-based semiconductor layer and the second crystalline silicon-based semiconductor layer are independently formed without being continuously deposited by a chemical vapor deposition method. A thin-film photoelectric conversion device characterized by being deposited under the following film-forming conditions. 2. The thin film photoelectric conversion device according to claim 1, wherein the thickness of the second crystalline silicon-based semiconductor layer is larger than the thickness of the first crystalline silicon-based semiconductor layer. Photoelectric conversion device.

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