JP2004095784A - Thin film photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film photoelectric converter which can be easily manufactured and which has a high conversion efficiency. <P>SOLUTION: A first thin film photoelectric conversion element 20 includes a first transparent conductive layer 12, a first one conductivity type silicon semiconductor layer 21, a substantially intrinsic amorphous silicon semiconductor layer 22, a first reverse conductivity type silicon semiconductor layer 23, and a second transparent conductive layer 30. These are sequentially formed on a first transparent substrate 11. A second thin film photoelectric conversion element 70 includes a second one conductivity type silicon semiconductor layer 71, a crystalline silicon semiconductor layer 72 having a substantially intrinsic columnar grown surface ruggedness, a third reverse conductivity type silicon semiconductor layer 73 and a third transparent conductive layer 80. These are sequentially formed on a conductive substrate 60 of a second substrate or an insulating substrate 50 of a second substrate having a conductive layer 61. A dense layer 90 between both the elements is made of a transparent resin layer. <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 bonded to each other and separately takes out an electric output, and in particular, uses an amorphous and crystalline thin-film silicon-based semiconductor. The present invention relates to a mechanical stack type thin film photoelectric conversion device having a light confinement structure and a method of manufacturing the same.
[0002]
[Prior art]
Silicon-based thin-film solar cells are being actively developed for high conversion efficiency, 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.
[0003]
As 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 stuck with an adhesive and electric outputs are separately taken out. 27278). 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 of the above publication, a PIN junction of amorphous silicon is described as the first semiconductor, and a PIN junction of amorphous silicon-germanium is described as the second semiconductor. 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. In addition, in order to connect both ends of each of the two series-type solar cells, the first semiconductor is connected in 5 series, and the second semiconductor is connected in 6 series, and the optimum operating voltages at both ends are almost equal. I am trying to become.
[0004]
As Conventional Example 2, a mechanical stack type thin-film solar cell module is known (see Japanese Patent Application Laid-Open No. 1-68997). 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. 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 a substrate in addition to 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 sub-module and the second sub-module are characterized by having a stripe type structure having the same width.
[0005]
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 Japanese Patent Publication No. 5-25187). This silicon-based thin-film solar cell is obtained by laminating two PIN junctions (top cell on the light incident side and bottom cell on the light reflection side) on one substrate, and the second I-type layer is first intrinsic or substantially intrinsic. After the amorphous semiconductor is formed, it is crystallized by irradiating intense light, 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 crystalline. The difference is that the band gap Eg of the I-type film is made 0.15 eV or more without using expensive germane (GeH4). 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. .
[0006]
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 Japanese Patent Application Laid-Open No. 2001-217440). 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. Here, one amorphous photoelectric conversion unit includes one conductivity type layer 21, an amorphous photoelectric conversion layer 22, and a reverse conductivity type layer 23. One crystalline photoelectric conversion unit includes one conductivity type layer 31, The back electrode 40 is composed of a transparent conductive oxide layer 41 and a 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. In the first amorphous photoelectric conversion unit, short-wavelength light is better absorbed and a photocurrent is generated, and in the second crystalline photoelectric conversion unit, 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 obtained by the light confinement effect due to unevenness of each photoelectric conversion unit film surface. Trying to get.
[0007]
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 I of the two photoelectric conversion units coincide with each other to make the two photoelectric conversion units the optimum 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.
[0008]
As a fifth conventional example, a tandem thin film photoelectric conversion device in which the fourth conventional example is integrated is known (see Japanese Patent Application Laid-Open No. H11-186585). 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.
[0009]
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.
[0010]
[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 second semiconductor is an amorphous silicon / germanium having a high light absorptivity for long-wavelength light, and there is no description about the unevenness of the photoelectric conversion surface, probably because it is not necessary to have a light confinement structure.
[0011]
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 which is recrystallized by annealing or the like. No mention is made of light confinement structures such as unevenness of the photoelectric conversion surface, and it is not known whether recrystallized thin-film polycrystalline silicon forms surface irregularities, or whether the crystal irregularities are 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, there is no mention of a light confinement structure such as a roughening of the photoelectric conversion surface made of the first hydrogenated amorphous silicon.
[0012]
In Conventional Example 3, the first cell is amorphous and deteriorates in light, but the second cell is considered not to deteriorate due to crystallization. However, the first and second photoelectric conversion cells are connected in series. Therefore, these currents must be equal in terms of the circuit, and the second cell is also affected by the photodeterioration of the first cell, resulting in a problem that 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.
[0013]
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.
[0014]
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. This has resulted in design difficulties and manufacturing difficulties. That is, the design requires advanced simulation technology for many parameters, the manufacturing requires advanced manufacturing technology to ensure the stability and uniformity in manufacturing, and the solar cell with high yield that can be manufactured at low cost. Was difficult to provide. 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. 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.
[0015]
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 a multi-layer film, and it is difficult to provide an extraction electrode in the film.
[0016]
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.
[0017]
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. Generally, in order to increase the crystallization rate, the temperature of the deposition substrate of the crystalline silicon-based semiconductor film is higher than the temperature of the deposition substrate of the amorphous silicon-based semiconductor film, and such a diffusion problem is easily caused. 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.
[0018]
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 same problem as in the above arises. Was causing.
[0019]
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.
[0020]
The in-plane variation of some 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 series connection, and the conversion efficiency is reduced by integration. was there.
[0021]
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.
[0022]
In the case of a conventional method of manufacturing a thin-film photoelectric conversion device having a two-terminal tandem structure as in Conventional Example 4, continuous film formation is performed by an in-line type chemical vapor deposition apparatus, while avoiding exposure to air during deposition of a thin-film semiconductor. Amorphous silicon-based semiconductors and crystalline silicon-based semiconductors differ in film thickness by about an order of magnitude, resulting in a large difference in film formation time. Inline type continuous film formation equipment is an inefficient production method and increases costs. .
[0023]
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. It is another object of the present invention to provide a thin-film photoelectric conversion device in which light degradation of one cell does not affect the other cell where light degradation does not occur. In addition, the unevenness can be designed and manufactured independently for the first cell and the second cell, and the conversion can be performed by providing an effective light confinement structure between the first cell and the second cell. An object is to provide a thin-film photoelectric conversion device with high efficiency. Also, by separating the production of the first cell and the second cell, and by eliminating or reducing the role of the insertion step such as the diffusion suppressing layer, the production is facilitated, the cost is reduced, and the conversion efficiency is increased. It is an object to provide a thin-film photoelectric conversion device.
[0024]
Another object is to provide a thin-film photoelectric conversion device having an integrated structure with high conversion efficiency.
[0025]
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 amorphous silicon-based semiconductor layer can be reduced, so that the first photoelectric conversion element can be formed. An object of the present invention is to provide a thin-film photoelectric conversion device that can reduce light degradation of a conversion element.
[0026]
Still another object of the present invention is to provide a thin-film electromotive device which eliminates a back sheet, can be reduced in cost, and has excellent environmental resistance.
[0027]
[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 mechanical stack type thin-film photoelectric conversion device comprising a second thin-film photoelectric conversion device and a second thin-film photoelectric conversion device which are opposed to each other so that the two substrates are located outside. A first light-transmitting conductive layer, a first one-conductivity-type silicon-based semiconductor layer, a substantially intrinsic amorphous silicon-based semiconductor layer, and a first reverse-conductivity-type silicon-based semiconductor layer on one substrate , And a second light-transmitting conductive layer are sequentially stacked, and the second thin-film photoelectric conversion element is provided on the second substrate with a second one-conductivity-type silicon-based semiconductor layer, substantially An intrinsic crystalline silicon-based semiconductor layer having an uneven surface, a second reverse conductivity type semiconductor layer; Con-based semiconductor layer, and the third is of a laminated transparent conductive layer are sequentially made by, and intimately layer between the two thin-film photoelectric conversion device is characterized by comprising a translucent resin layer.
[0028]
In particular, the film thickness of the amorphous silicon-based semiconductor layer is 0.05 μm to 0.5 μm, and the film thickness of the crystalline silicon-based semiconductor layer is 0.5 μm to 5 μm.
[0029]
Particularly, the crystalline silicon-based semiconductor layer has spontaneous unevenness due to crystalline columnar deposition, and the third light-transmitting conductive layer formed on the spontaneous unevenness and the third light-transmitting conductive layer The light confinement effect is enhanced by the uneven structure with the close layer.
[0030]
In particular, the surface of the second substrate in contact with the crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has an uneven shape.
[0031]
In particular, it is preferable that at least the surface of the first light-transmitting conductive layer or the surface of the first substrate that is in contact with the amorphous silicon-based semiconductor layer and the first one-conductivity-type silicon-based semiconductor layer have irregularities. Features.
[0032]
In particular, the surface of the second substrate that is in contact with the crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has an uneven shape, and the amorphous silicon-based semiconductor and the first semiconductor layer have the same structure. At least the surface of the first light-transmitting conductive layer or the surface of the first substrate that is in contact with the conductive silicon-based semiconductor layer has an uneven shape, and the height difference and pitch of the uneven portion on the surface of the second substrate are different. The height of the uneven portion on the surface of the first substrate is larger than the pitch.
[0033]
In particular, the amorphous silicon-based semiconductor layer and the crystalline silicon-based semiconductor layer are deposited under unique film forming conditions without being continuously deposited by a chemical vapor deposition method.
[0034]
More particularly, the substrate temperature for depositing the crystalline silicon-based semiconductor layer is higher than the substrate temperature for depositing the amorphous silicon-based semiconductor layer.
[0035]
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.
[0036]
As shown in FIG. 1, the thin-film photoelectric conversion device 1 includes a first thin-film photoelectric conversion element 20 including a first substrate 11 and a second thin-film photoelectric conversion element 70 including a second substrate. A thin film photoelectric conversion device 1 of a mechanical stack type, which is disposed to face both substrates 11 and 50 outside, wherein a first thin film photoelectric conversion element 20 is provided on a light transmitting substrate 11 in order. , A first one-conductivity-type silicon-based semiconductor layer 21, a substantially intrinsic amorphous silicon-based semiconductor layer 22, a first reverse-conductivity-type silicon-based semiconductor layer 23, and a second The second thin-film photoelectric conversion element 70 is formed on the conductive substrate 60 as the second substrate or on the insulating substrate 50 as the second substrate provided with the conductive layer 61. Sequentially, the second one-conductivity-type silicon-based semiconductor layer 71, a substantially intrinsic pillar A crystalline silicon-based semiconductor layer 72 having a growth surface irregularity, a second reverse-conductivity-type silicon-based semiconductor layer 73, and a third light-transmitting conductive layer 80, and the close contact layer 90 between both elements is light-transmitting. It consists of a resin layer.
[0037]
Thus, for example, even if the thickness of the amorphous silicon-based semiconductor film 22 in the first thin film photoelectric conversion element 20 has a center value variation or in-plane variation, this is caused by the photovoltaic effect of 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 electric power, the conversion efficiency as a whole is not reduced, and the conversion efficiency is higher than that of the related art. The same applies to film quality and light degradation. 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.
[0038]
In addition, by providing a close contact layer 90 made of a light-transmitting resin having a large difference in refractive index from the silicon-based semiconductor between the first and second thin-film photoelectric conversion elements, light to the first amorphous silicon-based semiconductor layer can be reduced. Reflection increases, the thickness of the first amorphous silicon-based semiconductor layer 22 can be reduced, and light degradation of the first thin-film photoelectric conversion element 20 can be reduced.
[0039]
Further, according to the thin-film photoelectric conversion device of the present invention, the crystalline silicon-based semiconductor layer 72 has spontaneous irregularities due to crystalline columnar deposition, and the third translucent conductive layer 80 formed on the spontaneous irregularities and The concavo-convex configuration of the third light-transmitting conductive layer 80 and the close contact layer 90 formed of the light-transmitting resin layer can enhance the light confinement effect.
[0040]
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.
[0041]
According to the thin-film photoelectric conversion device of the present invention, the thickness of the substantially intrinsic amorphous silicon-based semiconductor layer 22 is 0.05 μm to 0.5 μm, and the substantially intrinsic crystalline silicon The film thickness of the system semiconductor layer 72 is 0.5 μm to 5 μm.
[0042]
This makes it possible to make the light confinement structure more effective than before, and it is possible to set a thinner film thickness. By setting the amorphous silicon-based semiconductor layer 22 having a smaller thickness, light degradation can be further reduced. Further, by setting the substantially intrinsic crystalline silicon-based semiconductor layer 72 having a smaller film thickness, the film formation time can be further shortened. If the thickness of the amorphous silicon-based semiconductor layer is 0.05 μm or less, sufficient photovoltaic power cannot be obtained from the first thin-film photoelectric conversion element. It is difficult to pay. If the thickness of the crystalline silicon-based semiconductor layer 72 is 0.5 μm or less, sufficient photovoltaic power cannot be obtained from the second thin film photoelectric conversion element. Problem.
[0043]
Further, according to the thin-film photoelectric conversion device of the present invention, the insulating layer having the surface of the conductive substrate 60 or the conductive layer 61 in contact with the crystalline silicon-based semiconductor layer 72 and the second one-conductivity-type silicon-based semiconductor layer 71 is provided. The surface of the substrate 50 is uneven.
[0044]
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.
[0045]
Further, according to the thin-film photoelectric conversion device of the present invention, at least the surface of the first light-transmitting conductive layer 12 or the first surface in contact with the amorphous 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.
[0046]
Further, according to the thin-film photoelectric conversion device of the present invention, the first unevenness (the difference in elevation) of the insulating substrate 50 having the light-reflective conductive substrate 60 or the conductive layer 61 in contact with the crystalline silicon-based semiconductor layer 72 is obtained. (Pitch) is larger than the second unevenness (height difference and pitch) of the light transmitting substrate 11 or the first light transmitting conductive layer 12 which is in contact with the amorphous 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.
[0047]
Further, according to the thin-film photoelectric conversion device of the present invention, the amorphous silicon-based semiconductor layer 22 and the crystalline silicon-based semiconductor layer 72 are deposited under their own film forming conditions without being continuously deposited by the chemical vapor deposition method. It is characterized by being performed.
[0048]
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. In particular, the thickness of the amorphous silicon-based semiconductor layer differs from that of the crystalline silicon-based semiconductor layer by about an order of magnitude, and the film formation time also differs by about an order of magnitude. Good production methods become possible.
[0049]
Further, according to the thin-film photoelectric conversion device of the present invention, chemical vapor deposition at a substrate temperature at which the crystalline silicon-based semiconductor layer 72 is deposited is higher than the substrate temperature at which the amorphous silicon-based semiconductor layer 22 is deposited. It is characterized by being deposited by a method.
[0050]
This facilitates the crystallization deposition of the crystalline silicon-based semiconductor layer 72, and furthermore, the deposition of the crystalline silicon-based semiconductor layer 72 adversely affects the deposited amorphous silicon-based semiconductor layer 22 such as impurity diffusion. High conversion efficiency without providing a special diffusion suppressing film between the P film and the I film of the amorphous silicon semiconductor layer 22 and between the amorphous silicon semiconductor layer 22 and the first transparent conductive layer 12. Is obtained, so that the diffusion suppressing film becomes unnecessary.
[0051]
【Example】
Hereinafter, the present invention will be described with reference to Examples 1 to 4, which show the present invention more specifically.
<Example 1>
In FIG. 1, reference numeral 1 denotes a thin-film photoelectric conversion device. Reference numeral 11 denotes a light-transmitting substrate. In this embodiment, as the light-transmitting substrate, blue plate glass (for example, 1.8 mm in thickness) having both flat surfaces is used. As another light-transmitting substrate, a transparent inorganic substrate such as white 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 film deposited by a sputtering method is used. As another light-transmitting conductive film, a SnO 2 film, a ZnO (impurity-doped) film deposited by a sputtering method or the like may be used, or these light-transmitting conductive films may be stacked and used. Reference numeral 20 denotes an amorphous silicon-based semiconductor film having a PIN junction. The hydrogenated amorphous silicon-based film is used as a PIN junction semiconductor formed by stacking a P-type semiconductor film, an I-type semiconductor film, and an N-type semiconductor film. In the example, deposition is performed by a plasma CVD method, but deposition may be performed by a catalytic CVD method or the like. 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 amorphous, the P-type semiconductor film and / or the N-type semiconductor film may be microcrystalline. Also, 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.
[0052]
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 a-Si: H semiconductor film was deposited at 90 ° (0.009 μm). A P-type a-SiC: H film may be used instead of the P-type a-Si: H semiconductor. SiH4, H2 gas, and B2H6 (diluted to 500 ppm with H2) were used as source gases of P-type a-Si: H, and the flow rates of these gases were 3 sccm, 10 sccm, and 2 sccm, respectively. Subsequently, an I-type semiconductor film was deposited at 1700 °. SiH4 and H2 gases were used as source gases for I-type a-Si: H, and the flow rates of these gases were 30 sccm and 80 sccm, respectively. 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.
[0053]
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, ZnO, SnO2: F, or the like may be used, or a stacked film of these 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.
[0054]
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.
[0055]
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 another material configuration, Ti / Ag: Al alloy / ZnO: Al may be used.
[0056]
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 / or the N-type semiconductor film may be amorphous. 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 °. A P-type μc-SiC: H film may be used instead of the P-type a-Si: H semiconductor. 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 260 ° C. for all of the NIP films.
[0057]
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, ZnO: Al, SnO2: F, or the like may be used, or a stacked film of these may be used. Further, a collector electrode similar to the above may be formed thereon.
[0058]
Reference numeral 90 denotes a light-transmitting resin. In this embodiment, a transparent sealing resin EVA (ethylene-vinyl acetate copolymer resin) is used. An EVA sheet is sandwiched between both substrates, these are decompressed, and a thin film photoelectric conversion element is manufactured by a process including melting of a resin by heating, compression / filling of EVA, thermosetting, primary cooling, release to atmospheric pressure, and secondary cooling. did.
[0059]
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, an element was manufactured using the conventional structure of FIG. 2 under the same manufacturing conditions as above.
[0060]
The results of the conversion efficiencies of the two types of photoelectric conversion devices thus obtained under AM 1.5 show that the conversion efficiency of the thin film electromotive device of Comparative Example 1 was 7.2%, whereas the conversion efficiency of the thin film electromotive device of Example 1 was 7.2%. Was 7.7%, indicating a higher conversion efficiency.
<Example 2>
First, a first thin-film electromotive element substrate was manufactured in the same manner as in Example 1.
[0061]
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, a thin film electromotive force device of Example 2 was manufactured with a configuration in which 90 translucent resins were sandwiched in the same manner as in Example 1. 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.
[0062]
The results of the conversion efficiency of the two types of photoelectric conversion devices thus obtained under AM1.5 show that the conversion efficiency of the thin film electromotive device of Comparative Example 1 was 7.2%, whereas the conversion efficiency of the thin film electromotive device of Example 2 was 7.2%. Was 8.2%, indicating a 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 irregularities of the polycrystalline SnO2: F film were about 150 nm to 250 nm and about 200 nm to 300 nm, respectively. On this substrate, under the same conditions as in Example 1, 20 amorphous silicon-based semiconductor films having a PIN junction and 30 second light-transmitting conductive films were sequentially formed. Then, a second thin-film electromotive element substrate was manufactured in the same manner as in Example 1.
[0063]
Then, a thin film electromotive device was manufactured with a configuration in which 90 translucent resins were 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. An amorphous silicon-based semiconductor film having a PIN junction of 20, a crystalline silicon-based semiconductor film having a PIN junction of 30, and a light-reflective conductive film of 40 were sequentially manufactured in the same manner as in Example 3.
[0064]
The results of the conversion efficiencies of the two types of photoelectric conversion devices thus obtained under AM 1.5 show that the conversion efficiency of the thin film electromotive device of Comparative Example 3 is 7.6%, whereas the conversion efficiency of the thin film electromotive device of Example 3 is 7.6%. Was 8.3%, indicating a 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.
Then, a thin-film electromotive device according to the fourth embodiment was manufactured with a configuration in which ten translucent resins were sandwiched 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.
The results of the conversion efficiencies of the two types of photoelectric conversion devices thus obtained under AM 1.5 show that the conversion efficiency of the thin film electromotive device of Comparative Example 3 is 7.6%, whereas the conversion efficiency of the thin film electromotive device of Example 4 is 7.6%. Showed a higher conversion efficiency of 8.5%.
[0065]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the thin-film photoelectric conversion device of this invention, the adverse effect of center value fluctuation | variation in a thin film manufacture, in-plane variation, etc. was reduced, and the light confinement effect which consists of a concave-convex structure was improved, and conversion efficiency improvement and large area increase. Cost can be reduced.
[0066]
More specifically, according to the thin-film photoelectric conversion device of claim 1, for example, even if the thickness of the amorphous silicon-based semiconductor film in the first thin-film photoelectric conversion element has a central value variation or an in-plane variation, this does not occur. Since the first thin-film photoelectric conversion element has no relation to the photovoltaic power of the second thin-film photoelectric conversion element and is shifted to the optimum operating point, the overall conversion efficiency does not decrease, and the conversion efficiency is higher than that of the prior art. Become. The same applies to film quality and light degradation. 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.
[0067]
Further, by providing a close contact layer made of a translucent resin having a large difference in refractive index from the silicon-based semiconductor between the first and second thin-film photoelectric conversion elements, light reflection on the first amorphous silicon-based semiconductor layer is achieved. Is increased, the thickness of the first amorphous silicon-based semiconductor layer can be reduced, and light degradation of the first thin-film photoelectric conversion element can be reduced.
[0068]
According to the thin film photoelectric conversion device of the third aspect, the crystalline silicon-based semiconductor layer has spontaneous irregularities due to crystalline columnar deposition, and the third translucent conductive layer formed on the spontaneous irregularities and The light confinement effect can be enhanced by the concavo-convex configuration of the third light-transmitting conductive layer and the close-contact layer made of the light-transmitting resin layer. 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.
[0069]
According to the thin film photoelectric conversion device of claim 2, the thickness of the substantially intrinsic amorphous silicon-based semiconductor layer is 0.05 μm to 0.5 μm, and the substantially intrinsic crystalline silicon The film thickness of the system semiconductor layer is 0.5 μm to 5 μm. This makes it possible to make the light confinement structure more effective than before, and it is possible to set a thinner film thickness. By setting the amorphous silicon-based semiconductor layer having a smaller thickness, light degradation can be further reduced. Further, by setting a substantially intrinsic crystalline silicon-based semiconductor layer having a smaller film thickness, the film formation time can be further reduced. If the thickness of the amorphous silicon-based semiconductor layer is 0.05 μm or less, sufficient photovoltaic power cannot be obtained from the first thin-film photoelectric conversion element. It is difficult to pay. If the thickness of the crystalline silicon-based semiconductor layer is 0.5 μm or less, sufficient photovoltaic power cannot be obtained from the second thin-film photoelectric conversion element. If the thickness is 5 μm or more, the efficiency and cost increase due to the decrease in the internal electric field strength in the film. There's a problem.
[0070]
According to the thin-film photoelectric conversion device of the fourth aspect, the surface of the conductive substrate in contact with the crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer or the surface of the insulating substrate having the conductive layer. Have irregularities. 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 irregularities 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 irregularities can be obtained, and a higher conversion efficiency can be obtained as compared with the related art. .
[0071]
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 substrate in contact with the amorphous silicon-based semiconductor layer and the first one-conductivity-type silicon-based semiconductor layer. 11 is characterized in that the surface is uneven. 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.
[0072]
According to the thin film photoelectric conversion device of the sixth aspect, the first unevenness (height difference and pitch) of the light-reflective conductive substrate or the insulating substrate having the conductive layer in contact with the crystalline silicon-based semiconductor layer is reduced. And a second light-transmitting substrate or a first light-transmitting conductive layer in contact with the amorphous 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.
[0073]
According to the thin-film photoelectric conversion device of the seventh aspect, the amorphous silicon-based semiconductor layer and the crystalline silicon-based semiconductor layer are deposited under their own film forming conditions without being continuously deposited by the chemical vapor deposition method. It is characterized by that. 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. In particular, the thickness of the amorphous silicon-based semiconductor layer differs from that of the crystalline silicon-based semiconductor layer by about an order of magnitude, and the film formation time also differs by about an order of magnitude. Good production methods become possible.
[0074]
Further, according to the thin film photoelectric conversion device of claim 8, the chemical vapor deposition method wherein the substrate temperature for depositing the crystalline silicon-based semiconductor layer is higher than the substrate temperature for depositing the amorphous silicon-based semiconductor layer. , Respectively. This facilitates the crystallization and deposition of the crystalline silicon-based semiconductor layer, and furthermore, the deposition of the crystalline silicon-based semiconductor layer does not adversely affect the deposited amorphous silicon-based semiconductor layer such as impurity diffusion. High conversion efficiency can be obtained without providing a special diffusion suppressing film between the P film and the I film of the amorphous silicon semiconductor layer and between the amorphous silicon semiconductor layer and the first transparent conductive layer. No membrane is required.
[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: amorphous 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: crystalline silicon-based semiconductor layer
73: second reverse conductivity type silicon-based semiconductor layer
80: Third translucent conductive layer
90: Close layer

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. A thin film photoelectric conversion device of a mechanical stack type, wherein the first thin film photoelectric conversion element includes a first light-transmitting conductive layer, a first light-transmitting conductive layer, A first conductivity type silicon-based semiconductor layer, a substantially intrinsic amorphous silicon-based semiconductor layer, a first reverse conductivity type silicon-based semiconductor layer, and a second light-transmitting conductive layer are sequentially laminated. The second thin-film photoelectric conversion element includes a second one-conductivity-type silicon-based semiconductor layer, a substantially intrinsic crystalline silicon-based semiconductor layer having an uneven surface, Of a reverse conductivity type silicon-based semiconductor layer and a third light-transmitting conductive layer are sequentially laminated. Made, and the thin-film photoelectric conversion device closely layer is characterized by comprising a light-transmitting resin layer between the two thin-film photoelectric conversion element. 2. The thin-film photoelectric conversion device according to claim 1, wherein the thickness of the amorphous silicon-based semiconductor layer is 0.05 μm to 0.5 μm, and the thickness of the crystalline silicon-based semiconductor layer is 0.5 μm. From 5 to 5 μm. 2. The thin-film photoelectric conversion device according to claim 1, wherein the crystalline silicon-based semiconductor layer has spontaneous irregularities formed by crystalline columnar deposition, and the third translucent conductive layer formed on the spontaneous irregularities. 3. A thin-film photoelectric conversion device, wherein a light confinement effect is enhanced by a concavo-convex structure on the third light-transmitting conductive layer and the close contact layer. 2. The thin-film photoelectric conversion device according to claim 1, wherein a surface of the second substrate in contact with the 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 characterized by the above-mentioned. 2. The thin-film photoelectric conversion device according to claim 1, wherein at least the surface of the first light-transmitting conductive layer in contact with the amorphous silicon-based semiconductor layer and the first one-conductivity-type silicon-based semiconductor layer or the first light-transmitting conductive layer. 3. A thin-film photoelectric conversion device, wherein the surface of the substrate is uneven. 2. The thin-film photoelectric conversion device according to claim 1, wherein the second substrate surface in contact with the crystalline silicon-based semiconductor layer and the second one-conductivity-type silicon-based semiconductor layer has an uneven shape, and At least the surface of the first light-transmitting conductive layer or the surface of the first substrate which is in contact with the crystalline silicon-based semiconductor and the first one-conductivity-type silicon-based semiconductor layer, has an irregular shape, and the second substrate A thin film photoelectric conversion device, wherein a height difference and a pitch of the uneven portion on the surface are larger than a height difference and a pitch of the uneven portion on the first substrate surface. 2. The thin-film photoelectric conversion device according to claim 1, wherein the amorphous silicon-based semiconductor layer and the crystalline silicon-based semiconductor layer are formed under their own film forming conditions without being continuously deposited by a chemical vapor deposition method. A thin film photoelectric conversion device characterized by being deposited. 2. The thin film photoelectric conversion device according to claim 1, wherein a substrate temperature for depositing said crystalline silicon-based semiconductor layer is higher than a substrate temperature for depositing said amorphous silicon-based semiconductor layer. Conversion device.

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