JP2011198964A - Thin-film photoelectric converter and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thin-film photoelectric converter with high-crystallinity conductive layers whose electrical property is prevented from deteriorating because of increase in electrical resistance in structural layers and structural defects and which excels in photoelectric conversion efficiency, and to provide a manufacturing method for the converter.SOLUTION: The manufacturing method for the thin-film photoelectric converter includes a first step for forming a transparent electrode layer on a translucent substrate, with the transparent electrode layer consisting of a transparent conductive film; a second step for forming an amorphous layer on the transparent electrode layer; a third step for forming a first crystalline conductive layer on the amorphous layer by the ion assistant plasma CVD method; a fourth step for forming a photoelectric conversion layer on the first crystalline conductive layer that converts light into electricity; a fifth step for forming a second conductive layer on the photoelectric conversion layer; and a sixth step for forming a rear surface reflective electrode layer on the second conductive layer.

Description

  The present invention relates to a photoelectric conversion device having a thin film crystal conductivity type layer and a manufacturing method thereof.

  In recent years, in order to achieve both low cost and high efficiency of solar cells, thin film solar cells have been vigorously developed, and multi-junction thin film photoelectric conversion devices have attracted attention. Generally, the configuration of a multi-junction photoelectric conversion device includes a transparent conductive layer, a photoelectric conversion layer, a conductive type layer, an intermediate layer, and a back reflective electrode layer, and is generated in the photoelectric conversion layer by a built-in electric field created by the conductive type layer. Carrier is transported.

  For example, amorphous silicon or microcrystalline silicon is used for the photoelectric conversion layer. Taking a microcrystalline silicon photoelectric conversion layer as an example, it is necessary to devise film forming conditions and a surface state of a film to be manufactured to improve the crystallinity of the initial growth portion of the photoelectric conversion layer. Here, examples of the film to be manufactured include a glass substrate with a transparent conductive layer and a silicon thin film deposited thereon. As one of the means, there is a method of promoting nucleation and enhancing crystallinity by depositing a photoelectric conversion layer on a crystallized conductivity type layer.

  In addition, efforts have been made to improve the electrical characteristics of the photoelectric conversion device by increasing the crystallinity of the conductive layer. In general, the conductivity type layer has a film thickness of several nanometers to several tens of nanometers, is very thin, the film structure is easily disturbed by doping, and a wide range such as silicon carbide or silicon oxide for reducing light absorption loss. It is difficult to crystallize because of the use of a gap material. Therefore, in order to crystallize the conductive layer, it is conceivable to use a laser annealing method or an ion-assisted plasma CVD method used for manufacturing a TFT-related device or the like (see, for example, Patent Document 1 and Patent Document 2).

  The application of the laser annealing method to the manufacture of a thin film photoelectric conversion device is very difficult to apply at present due to the technology and cost problems corresponding to the increase in the area of solar cell panels seen in recent years. In contrast, the ion-assisted plasma CVD method is practically preferable because it is inexpensive and relatively easy to form a film over a large area. The ion-assisted plasma CVD method is characterized by irradiating active ions to a deposition surface in a film formation process by a normal plasma CVD method, which makes it easy for the deposit to acquire energy and move to a stable crystal structure site, Crystallization is promoted.

JP-A-7-094766 JP 2002-030449 A

  However, since the active ion energy during film formation by the ion-assisted plasma CVD method reaches several keV or more, ions can enter the inside of the deposited film by irradiating the deposited surface with active ions, and structural defects can be induced. For this reason, when ion-assisted plasma CVD is used for the production of thin-film solar cells having a multilayer structure, there is a problem of increased electrical resistance or induction of structural defects due to ion damage to the underlying transparent conductive film or photoelectric conversion layer. It was.

  The present invention has been made in view of the above, and has a highly crystalline conductive type layer, and a photoelectric conversion efficiency in which an increase in electrical resistance in a constituent layer and a decrease in electrical characteristics due to structural defects are prevented An object of the present invention is to obtain a thin film photoelectric conversion device and a method for manufacturing the same.

  In order to solve the above-described problems and achieve the object, a method of manufacturing a thin film photoelectric conversion device according to the present invention includes a first step of forming a transparent electrode layer made of a transparent conductive film on a light-transmitting substrate, A second step of forming an amorphous layer on the transparent electrode layer, a third step of forming a crystalline first conductivity type layer on the amorphous layer by ion-assisted plasma CVD, and the crystallinity A fourth step of forming a photoelectric conversion layer for converting light into electricity on the first conductive type layer, a fifth step of forming a second conductive type layer on the photoelectric conversion layer, and the second And a sixth step of forming a back-surface reflective electrode layer on the conductive type layer.

  According to the present invention, the amorphous layer suppresses the channeling phenomenon due to the assist ions in the ion-assisted plasma CVD method, thereby suppressing the damage to the crystalline first conductive type layer and the underlying film. A crystalline first conductivity type layer having high crystallinity can be formed without causing a decrease. Thereby, there exists an effect that the crystallinity of the initial part of the photoelectric converting layer formed into an upper layer can be improved, and photoelectric conversion efficiency can be improved.

FIG. 1 is a cross-sectional view showing the structure of a single junction photoelectric conversion device according to Embodiment 1 of the present invention. FIG. 2 is a flowchart for explaining an example of the manufacturing process of the single junction photoelectric conversion device according to the first embodiment of the present invention. FIGS. 3-1 is sectional drawing for demonstrating an example of the manufacturing process of the single junction photoelectric conversion apparatus concerning Embodiment 1 of this invention. FIGS. 3-2 is sectional drawing for demonstrating an example of the manufacturing process of the single junction photoelectric conversion apparatus concerning Embodiment 1 of this invention. FIGS. 3-3 is sectional drawing for demonstrating an example of the manufacturing process of the single junction photoelectric conversion apparatus concerning Embodiment 1 of this invention. FIGS. 3-4 is sectional drawing for demonstrating an example of the manufacturing process of the single junction photoelectric conversion apparatus concerning Embodiment 1 of this invention. FIG. 4 is a schematic diagram showing an example of the configuration of an ion-assisted CVD apparatus used for manufacturing the thin film crystal conductivity type layer according to the first embodiment of the present invention. FIG. 5 is a cross-sectional view showing the structure of the multi-junction photoelectric conversion device according to the second embodiment of the present invention.

  Embodiments of a thin film photoelectric conversion device and a method for manufacturing the same according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing the structure of a single junction photoelectric conversion device according to Embodiment 1 of the present invention. The single-junction photoelectric conversion device according to the first embodiment has a configuration in which a transparent electrode layer 2, a photoelectric conversion cell 3, a back surface transparent conductive layer 7, and a back surface reflective electrode layer 8 are sequentially stacked on a translucent insulating substrate 1. Have. The photoelectric conversion cell 3 has a configuration in which a thin film crystal conductive layer 31, a photoelectric conversion layer 32, and a conductive layer 33 are sequentially stacked on the transparent electrode layer 2 via an amorphous layer 30. In this single junction photoelectric conversion device, light enters from the translucent insulating substrate 1 side.

  As the light-transmitting insulating substrate 1, for example, a glass substrate, a light-transmitting resin having heat resistance such as polyimide or polyvinyl, or a laminate of them can be used as appropriate. There is no particular limitation as long as it can structurally support the entire solar cell. Further, a metal film with high permeability, a transparent conductive film, or an insulating film may be formed on these surfaces.

The transparent electrode layer 2 is made of a translucent conductive material. For example, tin oxide (SnO ₂ ), zinc oxide (ZnO), indium oxide (In ₂ O ₃ ), or the like can be used. A trace amount of impurities may be added to the film of the transparent electrode layer 2. The transparent electrode layer 2 may be a laminated film of these materials. The transparent electrode layer 2 is formed using a known method such as a CVD method, a sputtering method, or a vapor deposition method. Moreover, it is preferable that the transparent electrode layer 2 has a surface texture structure in which irregularities are formed on the surface. This texture structure scatters the light incident from the translucent insulating substrate 1 side, increases the light absorption amount by extending the substantial optical path length in the photoelectric conversion cell 3, and improves the photoelectric conversion efficiency. Can do.

  The photoelectric conversion cell 3 has at least one pair of pn junctions or pin junctions, and is configured by stacking one or more thin film semiconductor layers (photoelectric conversion layers) that generate photovoltaic power by generating incident light. A semiconductor layer. In the present embodiment, the photoelectric conversion cell 3 includes a first conductive type thin film crystal conductive type layer 31, a photoelectric conversion layer 32, and a second conductive type conductive type layer 33 sequentially stacked via an amorphous layer 30. Has been. For the photoelectric conversion cell 3, for example, amorphous silicon, microcrystalline silicon, amorphous silicon germanium, or microcrystalline silicon germanium is used.

  It is preferable to use the same material for the amorphous layer 30 and the thin film crystalline conductivity type layer 31. For example, amorphous silicon, amorphous silicon carbide, or amorphous silicon oxide is used. Here, the same material is used for the amorphous layer 30 and the thin-film crystalline conductive layer 31 because the amorphous layer 30 is partially melted and recrystallized by the ion-assisted plasma CVD method, and grown on the amorphous layer 30. This is because the interstitial distance and the crystal structure with the thin film crystal conductivity type layer 31 to be formed are made the same to minimize structural defects at the interface. In addition, when the same material is not used for the amorphous layer 30 and the thin film crystalline conductivity type layer 31, the material of the amorphous layer 30 and the thin film crystalline conductivity type layer 31 is a material having a close interstitial distance or a crystal structure. Is preferred. This is to minimize structural defects at the interface. In addition, the crystallized portion of the amorphous layer 30 is integrated with the thin film crystalline conductive layer 31 and functions as a conductive layer, so that the electrical resistance is relaxed.

  Further, in order to suppress damage to the transparent electrode layer 2 due to active ions in the ion-assisted plasma CVD method, the thickness of the amorphous layer 30 is preferably 0.1 nm to 50 nm, and preferably 3 nm to 20 nm. Is more preferable. By setting the film thickness of the amorphous layer 30 to a certain level or more, active ions reaching the transparent electrode layer 2 can be reduced, and damage to the transparent electrode layer 2 can be suppressed. On the other hand, if the film thickness of the amorphous layer 30 becomes too thick, light absorption loss due to the amorphous layer 30 increases. Therefore, the film thickness of the amorphous layer 30 is preferably in the above range.

Further, the thin film crystal conductivity type layer 31 includes helium (He) gas, neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, xenon (Xe) gas and the like as ion species used in the ion-assisted plasma CVD method. Or an ion generated from at least one kind of reactive gas such as hydrogen (H ₂ ) gas, fluorine (F ₂ ) gas, and hydrogen fluoride (HF) gas. It is preferable. By using these ionic species, crystallization of the thin film crystal conductive layer 31 can be promoted stably. In particular, by selecting hydrogen (H ₂ ) gas as the ionic species, the change in the composition of the film is small, and the influence of cross contamination can be ignored.

  The film thickness of the thin-film crystalline conductivity type layer 31 is preferably 0.1 nm to 50 nm, and more preferably 3 nm to 20 nm. By setting the film thickness of the thin film crystal conductivity type layer 31 in the above range, the thin film crystal conductivity type layer 31 has arbitrary crystallinity, and light absorption loss by the thin film crystal conductivity type layer 31 can be allowed. Therefore, the film thickness of the thin film crystalline conductivity type layer 31 is preferably 0.1 nm to 50 nm.

  The back surface reflective electrode layer 8 functions as a back surface electrode and also functions as a reflective layer that reflects light that has not been absorbed by the photoelectric conversion layer 32 and returns the light back to the photoelectric conversion layer 32, thereby contributing to improvement in photoelectric conversion efficiency. . Therefore, it is preferable that the back surface reflective electrode layer 8 has a high light reflectance and a high electrical conductivity. Such a back reflective electrode layer 8 is made of, for example, a metal material such as silver (Ag), aluminum (Al), copper (Cu), an alloy of these metal materials, a nitride of these metal materials, or these metal materials. The oxide can be formed. In addition, the specific material of these back surface reflective electrode layers 8 is not specifically limited, It can select from a well-known material suitably and can be used. The back reflective electrode layer 8 can be produced by a known method such as a vapor deposition method or a sputtering method.

Between the photoelectric conversion cell 3 and the back reflective electrode layer 8, tin oxide (SnO _2), it is preferable to form the back transparent conductive layer 7 made of a translucent conductive material such as zinc oxide (ZnO) . A trace amount of impurities may be added to the film of the transparent electrode layer 2. The back transparent conductive layer 7 may be a laminated film of these materials. The back transparent conductive layer 7 can be formed by using a known method such as a CVD method, a sputtering method, or a vapor deposition method.

  Next, a method for manufacturing the single junction photoelectric conversion device according to the present embodiment configured as described above will be described. FIG. 2 is a flowchart for explaining an example of a manufacturing process of the single junction photoelectric conversion device according to the first embodiment. 3A to 3D are cross-sectional views for explaining an example of the manufacturing process of the single junction photoelectric conversion device according to the first embodiment.

First, the translucent insulating substrate 1 is prepared. Here, a non-alkali glass substrate is used as the translucent insulating substrate 1 and will be described below. In addition, an inexpensive soda lime glass substrate may be used as the translucent insulating substrate 1, but in this case, in order to prevent the diffusion of alkali components from the translucent insulating substrate 1, an SiO ₂ film is formed by plasma CVD or the like. It is good to form.

Next, for example, a tin oxide (SnO ₂ ) film is formed on the translucent insulating substrate 1 by a sputtering method, and the transparent electrode layer 2 having irregularities on the surface is formed (step S10). As a method of forming the transparent electrode layer 2, a known method such as a CVD method or a vapor deposition method may be used in addition to the sputtering method.

  Next, the photoelectric conversion cell 3 is formed on the transparent electrode layer 2. First, the amorphous layer 30 is formed on the transparent electrode layer 2 by plasma CVD (step S20, FIG. 3-1). Next, a thin film crystal conductive layer 31 is formed on the transparent electrode layer 2 by ion-assisted plasma CVD (step S30, FIG. 3-2).

In order to form the amorphous layer 30 by the plasma CVD method, for example, silane (SiH ₄ ) gas and hydrogen (H ₂ ) gas are introduced into the vacuum chamber at a flow ratio of 1: X (0 ≦ X ≦ 50), and a dope gas As an example, phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) is introduced in an amount of 0.1 to 1% by volume with respect to silane (SiH ₄ ) gas, and the RF power is set to 15 mW by a high frequency power source of, for example, about 13 MHz to 60 MHz. Capacitively coupled plasma generated by applying at / cm ^{2 to} 320 mW / cm ² is used.

  The thin film crystal conductive type layer 31 is formed by the ion-assisted plasma CVD method using a film forming apparatus as shown in FIG. 4, and simultaneously with the formation of the conductive type layer by the normal capacitively coupled plasma CVD method, Ion irradiation from the source is performed. FIG. 4 is a schematic diagram showing an example of the configuration of an ion-assisted CVD apparatus used for manufacturing the thin film crystal conductivity type layer 31 according to the present embodiment.

  In forming the thin film crystal conductive layer 31 using this apparatus, the translucent insulating substrate 1 is placed on the substrate holder (cathode) 10 in the vacuum chamber 9, and the vacuum chamber 9 is evacuated in the vacuum chamber 12. The predetermined pressure is set by the operation of

  Next, a source gas containing silicon-based gas is introduced into the vacuum chamber 9 from the source gas supply unit 13 through the shower plate (anode) 11, and an inductively coupled high-frequency electric field is applied from the high-frequency power source 16 through the matching box 15. The applied gas is converted into plasma, and plasma is formed in the vacuum chamber 9. As the source gas, at least one kind of silicon-based gas or at least one kind of silicon-based gas and at least one kind of reactive gas are used.

  Further, ion source gas is introduced into the ion source 17 from the ion source gas supply unit 14, and high frequency power is supplied from the high frequency power source 16 through the matching box 15 to generate plasma in the vacuum chamber 9. By applying an appropriate voltage to the ion irradiation electrode system (not shown) by the acceleration electrode 18 and the deceleration electrode 19, ions are extracted from the plasma at an acceleration energy of 2 keV or more, more preferably 5 keV or more, and the ions are extracted onto the translucent insulating substrate 1. Irradiation of the ion beam is performed. A crystalline silicon film is formed on the translucent insulating substrate 1.

Here, for the capacitively coupled plasma CVD method, for example, silane (SiH ₄ ) gas and hydrogen (H ₂ ) gas are introduced at a flow ratio of 1: X (0 ≦ X ≦ 300), and a high frequency power source of about 13 MHz to 60 MHz. using the conditions applied 15mW ^/ cm ² ~800mW ^/ cm 2 RF power by. In addition, for ion irradiation, for example, hydrogen (H ₂ ) gas ions are used as ions to be irradiated, and irradiation conditions are applied with ion energy set to 2 keV or higher. In order to further improve the crystallinity, it is preferable to apply a condition of irradiation with ion energy of 5 keV or higher. As described above, the ion species to be irradiated include an inert gas or a reactive gas. Among these, since hydrogen (H ₂ ) gas is often used when forming a thin film photoelectric conversion device, it is preferable to use hydrogen (H ₂ ) gas. When other gases are used, there is a concern about the influence of contamination in the film.

  When the thin film crystalline conductive layer 31 is formed, the amorphous layer 30 reduces active ions that reach the underlying transparent electrode layer 2, thereby suppressing channeling phenomenon due to assist ions and ions to the underlying transparent electrode layer 2. Suppresses damage. As a result, it is possible to prevent the device function from being lowered due to a structural defect caused by ion damage. Further, the thin film crystal conductive type layer 31 can be crystallized by the crystallization promoting action by assist ions, and the thin film crystal conductive type layer 31 having high crystallinity can be formed. Therefore, the thin film crystalline conductive layer 31 having high crystallinity can be formed without causing a device function deterioration due to ion damage caused by assist ions. Further, when the thin film crystalline conductive layer 31 is formed, the ion irradiation surface and the inside of the amorphous layer 30 are partially melted and recrystallized by the energy of assist ions, and the conductivity in the film thickness direction is increased. Thereby, the electrical characteristics of the thin film photoelectric conversion device are maintained.

  Further, when the thin film crystal conductive type layer 31 is formed, the amorphous layer 30 is melted and recrystallized, whereby a crystal layer structure including the thin film crystal conductive type layer 31 is formed. For this structure, the ratio of the Raman peak intensity of the crystalline silicon TO mode to the amorphous silicon TO mode by laser Raman spectroscopy is preferably 1-5. When the Raman peak intensity ratio is smaller than 1, the light absorption loss due to this structure becomes significant. When the Raman peak intensity ratio is larger than 5, a structural defect is likely to occur when the photoelectric conversion layer 32 grown on the structure contains a crystalline material. By setting the Raman peak intensity ratio to 1 to 5, light absorption loss can be reduced and upper layer structure defect suppression can be achieved.

  After the formation of the thin film crystal conductivity type layer 31, the photoelectric conversion layer 32 is formed on the thin film crystal conductivity type layer 31 by plasma CVD (step S40). Here, when the thin film crystalline conductive layer 31 has high crystallinity, the crystallinity of the initial portion of the photoelectric conversion layer 32 formed thereon can be increased, and the photoelectric conversion efficiency can be improved. Subsequently, the conductive layer 33 is formed on the photoelectric conversion layer 32 by plasma CVD (step S50, FIG. 3-3).

  Next, for example, zinc oxide (ZnO) is formed on the conductive type layer 33 as the back transparent conductive layer 7 by using a known method such as CVD, sputtering, or vapor deposition (step S60). Subsequently, a metal thin film such as silver (Ag), aluminum (Al), or copper (Cu) is formed on the back transparent conductive layer 7 as a back reflective electrode layer 8 by a known method such as sputtering or vapor deposition ( Step S70, FIG. 3-4). As described above, the single junction photoelectric conversion device according to the first embodiment shown in FIG. 1 is manufactured.

  In the first embodiment described above, the amorphous layer 30 is formed on the transparent electrode layer 2 as a base layer before the thin film crystal conductive layer 31 is formed by the ion-assisted plasma CVD method. The amorphous layer 30 suppresses ion damage to the lower transparent electrode layer 2 by suppressing the channeling phenomenon due to assist ions when the thin film crystal conductive layer 31 is formed by the ion-assisted plasma CVD method. Thereby, the thin film crystal conductive type layer 31 can be crystallized without causing a device function deterioration due to structural defects caused by ion damage, and the thin film crystal conductive type layer 31 having high crystallinity can be formed. . And, since the thin film crystal conductivity type layer 31 has high crystallinity, the crystallinity of the initial part of the photoelectric conversion layer 32 formed on the thin film crystal conductivity type layer 31 is increased, and the photoelectric conversion efficiency is improved. Can do. In the present invention, it is indispensable to directly form the thin-film crystalline conductive layer 31 on the amorphous layer 30, but other configurations can be appropriately changed as necessary, such as addition / deletion. is there.

  In addition, since the ion-assisted plasma CVD method is used, the film can be formed at a low cost and in a large area.

Embodiment 2. FIG.
FIG. 5 is a cross-sectional view showing the structure of the multi-junction photoelectric conversion device according to the second embodiment of the present invention. The multi-junction photoelectric conversion device according to the second embodiment includes a transparent electrode layer 2, a front photoelectric conversion cell 3, an intermediate photoelectric conversion cell 4, an intermediate layer 5, a rear photoelectric conversion cell 6, on a translucent insulating substrate 1. This is a three-junction photoelectric conversion device in which a back transparent conductive layer 7 and a back reflective electrode layer 8 are sequentially laminated. In this multi-junction photoelectric conversion device, light enters from the translucent insulating substrate 1 side. In addition, about the member similar to the case of Embodiment 1, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol as FIG.

  Further, in this multi-junction photoelectric conversion device, the number of junctions of the photoelectric conversion cells is three junctions, but the number of junctions of the photoelectric conversion cells is not limited in the present invention. For example, it may be applied to a photoelectric conversion device having two or more junctions, for example, a two-junction photoelectric conversion device composed of amorphous silicon and microcrystalline silicon, or a three-junction photoelectric conversion device to which amorphous silicon germanium is added. The combination is not limited to this.

  The front photoelectric conversion cell 3, the intermediate photoelectric conversion cell 4, and the rear photoelectric conversion cell 6 have at least one pair of pn junctions or pin junctions, and a thin film semiconductor layer that generates photovoltaic power by generating power with incident light. It is a semiconductor layer formed by laminating one or more layers. The front photoelectric conversion cell 3 is the same as the photoelectric conversion cell 3 in the first embodiment. In the present embodiment, in the front photoelectric conversion cell 3, a thin film crystal conductive type layer 31, a photoelectric conversion layer 32, and a conductive type layer 33 are sequentially stacked on the transparent electrode layer 2 via an amorphous layer 30. In the intermediate photoelectric conversion cell 4, a thin film crystal conductive type layer 41, a photoelectric conversion layer 42, and a conductive type layer 43 are sequentially stacked on the front photoelectric conversion cell 3 through an amorphous layer 40. In the rear photoelectric conversion cell 6, a thin film crystal conductive type layer 61, a photoelectric conversion layer 62, and a conductive type layer 63 are sequentially stacked on the intermediate layer 5 via an amorphous layer 60. For the front photoelectric conversion cell 3, a material having a relatively wide band gap, for example, amorphous silicon is used. The rear photoelectric conversion cell 6 is preferably made of a material having a relatively narrow band gap, such as microcrystalline silicon or microcrystalline silicon germanium.

  It is preferable to use the same material for the amorphous layer 30 and the thin film crystalline conductivity type layer 31. For example, amorphous silicon, amorphous silicon carbide, or amorphous silicon oxide is used. Here, the same material is used for the amorphous layer 30 and the thin film crystalline conductive layer 31 because the thin film crystalline conductive layer 31 is partially melted and recrystallized by the ion-assisted plasma CVD method. This is because the structural defects at the interface are minimized by making the interstitial distance and the crystal structure of the amorphous layer 30 to be the same as that of the thin film crystal conductive type layer 31 grown on the amorphous layer 30 the same. In addition, when the same material is not used for the amorphous layer 30 and the thin film crystalline conductivity type layer 31, the material of the amorphous layer 30 and the thin film crystalline conductivity type layer 31 is a material having a close interstitial distance or a crystal structure. Is preferred. This is to minimize structural defects at the interface. In addition, the crystallized portion of the amorphous layer 30 is integrated with the thin film crystalline conductive layer 31 and functions as a conductive layer, so that the electrical resistance is relaxed.

  For the same reason, it is preferable to use the same material for the amorphous layer 40 and the thin film crystalline conductive layer 41, for example, amorphous silicon, amorphous silicon carbide, or amorphous silicon oxide is used. Further, the crystallized portion of the amorphous layer 40 is integrated with the thin film crystal conductive type layer 41 and functions as a conductive type layer, so that the electrical resistance is relaxed.

  For the same reason, it is preferable to use the same material for the amorphous layer 60 and the thin film crystalline conductivity type layer 61. For example, amorphous silicon, amorphous silicon carbide, or amorphous silicon oxide is used. In addition, the crystallized portion of the amorphous layer 60 is integrated with the thin film crystalline conductive layer 61 and functions as a conductive layer, so that the electrical resistance is relaxed.

  Further, as in the case of the first embodiment, the film thickness of the amorphous layer 30 is set to 0.1 nm to 50 nm in order to suppress damage to the transparent electrode layer 2 due to active ions in the ion-assisted plasma CVD method. It is preferably 3 nm to 20 nm, and more preferably. By setting the film thickness of the amorphous layer 30 to a certain level or more, active ions reaching the transparent electrode layer 2 can be reduced, and damage to the transparent electrode layer 2 can be suppressed. On the other hand, if the film thickness of the amorphous layer 30 becomes too thick, light absorption loss due to the amorphous layer 30 increases. Therefore, the film thickness of the amorphous layer 30 is preferably in the above range.

  Similarly, in order to suppress damage to the conductive type layer 33 by active ions in the ion-assisted plasma CVD method, the thickness of the amorphous layer 40 is preferably 0.1 nm to 50 nm, and is preferably 3 nm to 20 nm. More preferably.

  Similarly, in order to suppress damage to the intermediate layer 5 due to active ions in the ion-assisted plasma CVD method, the thickness of the amorphous layer 60 is preferably 0.1 nm to 50 nm, and preferably 3 nm to 20 nm. Is more preferable.

Further, the thin film crystal conductivity type layers 31, 41, and 61 are helium (He) gas, neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, xenon (ion species) used for ion-assisted plasma CVD. Xe) An inert gas such as a gas, or ions generated from at least one kind of reactive gas such as hydrogen (H ₂ ) gas, fluorine (F ₂ ) gas, and hydrogen fluoride (HF) gas are used. It is preferable to be formed. By using these ionic species, the crystallization of the thin film crystalline conductive layers 31, 41, 61 can be promoted stably.

  Further, the film thickness of the thin film crystal conductivity type layers 31, 41, 61 is preferably 0.1 nm to 50 nm, and more preferably 3 nm to 20 nm. By setting the film thickness of the thin film crystal conductivity type layers 31, 41, 61 within the above range, the thin film crystal conductivity type layers 31, 41, 61 have arbitrary crystallinity, and the thin film crystal conductivity type layers 31, 41 , 61 is acceptable. Therefore, it is preferable that the film thickness of the thin film crystal conductive type layers 31, 41, 61 is 0.1 nm to 50 nm.

  The intermediate layer 5 is a thin film having a low refractive index, a high transmittance or a high reflectance for a desired wavelength, and a conductivity. Such an intermediate layer 5 has, for example, a refractive index of about 1.5 to 2.5 and a film thickness of about 20 nm to 100 nm. Accordingly, even when applied to the multi-junction photoelectric conversion device according to the second embodiment shown in FIG. 5, there is no electrical loss due to the intermediate layer 5, and a desired photoelectric conversion cell on the incident side with respect to the intermediate layer 5 is desired. The light of the desired wavelength can be reflected, and the light of the desired wavelength can be transmitted to the photoelectric conversion cell on the opposite side.

  The manufacturing method of the multijunction photoelectric conversion device according to the second embodiment configured as described above is basically the same as the manufacturing method of the single junction photoelectric conversion device according to the first embodiment. That is, when forming each of the front photoelectric conversion cell 3, the intermediate photoelectric conversion cell 4, and the rear photoelectric conversion cell 6, first, the amorphous layers 30, 40, and 60 are formed by plasma CVD in the same manner as in the first embodiment. Form by the method. Then, the thin film crystal conductive layers 31, 41, 61 are formed on the amorphous layers 30, 40, 60 by the ion-assisted plasma CVD method as in the first embodiment. Thereafter, photoelectric conversion layers 32, 42, 62 and conductive type layers 33, 43, 63 are sequentially formed on the thin film crystal conductive type layers 31, 41, 61 in the same manner as in the first embodiment. Further, after the formation of the intermediate photoelectric conversion cell 4, the intermediate layer 5 is formed on the intermediate photoelectric conversion cell 4 before the amorphous layer 60 is formed.

  The formation conditions of the amorphous layers 30, 40, 60 by the plasma CVD method can be the same as in the first embodiment, for example. Further, the formation conditions of the thin film crystal conductive layers 31, 41, 61 by the ion-assisted plasma CVD method can be the same as those in the first embodiment, for example.

  During the formation of the thin-film crystalline conductive layers 31, 41, 61, the amorphous layers 30, 40, 60 suppress the channeling phenomenon due to assist ions, respectively, to the underlying transparent electrode layer 2, conductive type layer 33, and intermediate layer 5. Suppresses ion damage. As a result, it is possible to prevent the device function from being lowered due to a structural defect caused by ion damage. Further, the thin film crystal conductivity type layers 31, 41, 61 can be crystallized by the action of promoting crystallization by assist ions, and the thin film crystal conductivity type layers 31, 41, 61 having high crystallinity can be formed. . Therefore, it is possible to form the thin film crystal conductive layers 31, 41, 61 having high crystallinity without causing deterioration of the device function due to ion damage caused by assist ions. Further, when forming the thin film crystal conductivity type layers 31, 41, 61, the ion irradiation surface and the inside of the amorphous layers 30, 40, 60 are partially melted and recrystallized by the energy of assist ions, and the film thickness Increase directional conductivity. Thereby, the electrical characteristics of the thin film photoelectric conversion device are maintained.

  Further, when the thin film crystal conductive layers 31, 41, 61 are formed, the amorphous layers 30, 40, 60 are melted and recrystallized, so that the crystal layers including the thin film crystal conductive layers 31, 41, 61 are formed. For this structure where a structure is formed, the Raman peak intensity ratio of the crystalline silicon TO mode to the amorphous silicon TO mode by laser Raman spectroscopy is preferably 1-5. When the Raman peak intensity ratio is smaller than 1, the light absorption loss due to this structure becomes significant. When the Raman peak intensity ratio is larger than 5, a structural defect is likely to occur when the photoelectric conversion layer 32 grown on the structure contains a crystalline material. By setting the Raman peak intensity ratio to 1 to 5, light absorption loss can be reduced and upper layer structure defect suppression can be achieved.

  In the second embodiment described above, before forming the thin film crystalline conductive layers 31, 41, 61 by ion-assisted plasma CVD as in the first embodiment, the amorphous layers 30, 40, 60 is formed on the transparent electrode layer 2, the conductive type layer 33, and the intermediate layer 5. The amorphous layers 30, 40, and 60 are active to reach the underlying transparent electrode layer 2, the conductive type layer 33, and the intermediate layer 5 when the thin film crystalline conductive layers 31, 41, and 61 are formed by ion-assisted plasma CVD. By reducing the ions, channeling phenomenon due to assist ions is suppressed, and ion damage to the lower transparent electrode layer 2, the conductive type layer 33, and the intermediate layer 5 is suppressed. As a result, the thin film crystal conductive type layers 31, 41, 61 can be crystallized without causing deterioration of the device function due to structural defects caused by ion damage, and the thin film crystal conductive type layers 31, 41 having high crystallinity. , 61 can be formed. Since the thin film crystal conductivity type layers 31, 41, 61 have high crystallinity, the initial portions of the photoelectric conversion layers 32, 42, 62 formed on the thin film crystal conductivity type layers 31, 41, 61 are formed. Crystallinity can be improved and photoelectric conversion efficiency can be improved. In the present invention, it is indispensable to directly form the thin film crystalline conductive layers 31, 41, 61 on the amorphous layers 30, 40, 60, respectively. These can be changed as necessary.

  In addition, since the ion-assisted plasma CVD method is used, the film can be formed at a low cost and in a large area.

  Next, specific examples to which the present invention is applied will be described. Below, the material concerning the Example produced by applying this invention and the comparative example produced by the conventional method was produced, and the crystallinity was compared.

(Example)
In the example, according to the method for manufacturing a thin film crystal conductive type layer described above, a thin film crystal conductive type layer composed of an amorphous layer and a silicon film is formed on a glass substrate as follows, and the sample according to the example is prepared. Produced. First, an amorphous layer was formed on a glass substrate by the plasma CVD method under the following conditions. SiH ₄ gas, H ₂ gas, and CO ₂ gas were introduced into the vacuum chamber at a flow ratio of 1: 150: 1, and B ₂ H ₆ was introduced as a doping gas by 0.5 volume% with respect to SiH ₄ gas, and the flow rate was 27.56 MHz. An RF power of 200 mW / cm ^{2 was} applied from a high frequency power source, the substrate temperature was 200 ° C., and the film thickness was 10 nm.

Next, a thin film crystal conductive layer was formed on the amorphous layer by the ion-assisted plasma CVD method under the following conditions. The film forming conditions of the capacitively coupled plasma CVD method mainly involved in deposition are SiH ₄ gas, H ₂ gas, and CO ₂ gas at a flow ratio of 1: 150: 1, and B ₂ H ₆ as a doping gas with respect to SiH ₄ gas. 0.5 volume% was introduced, RF power was applied at 200 mW / cm ² from a 27.56 MHz high frequency power source, the substrate temperature was 200 ° C., and the film thickness was 10 nm. As the ion irradiation conditions, H ₂ gas was selected as an ion species, and the ion energy was set to 5 keV.

(Comparative example)
In the comparative example, a conductive layer made of a silicon film was formed on a glass substrate as follows to prepare a material according to the comparative example. A conductive layer was formed on a glass substrate by the plasma CVD method under the following conditions. SiH ₄ gas, H ₂ gas, and CO ₂ gas were introduced into the vacuum chamber at a flow ratio of 1: 150: 1, and B ₂ H ₆ was introduced as a doping gas by 0.5 volume% with respect to SiH ₄ gas, and the flow rate was 27.56 MHz. An RF power of 200 mW / cm ^{2 was} applied from a high frequency power source, the substrate temperature was 200 ° C., and the film thickness was 20 nm.

  Next, the crystallinity of each of the samples of Examples and Comparative Examples was evaluated by measuring the crystallinity of the silicon film by analysis using laser Raman spectroscopy. As a result, the Raman peak intensity ratio of the crystalline silicon TO mode to the amorphous silicon TO mode was 1.5 in Example 1 and 0.7 in the comparative example.

  Since the Raman peak intensity ratio is smaller than 1 in the silicon film of the comparative example, the light absorption loss becomes significant. Therefore, when this silicon film is applied to a thin film photoelectric conversion device as a conductive type layer, it causes a decrease in photoelectric conversion efficiency.

  On the other hand, in the silicon film of the sample of the example, the Raman peak intensity ratio is a value between 1 and 5, and light absorption loss can be reduced and upper layer structure defect suppression can be achieved. And when this silicon film is applied to a thin film photoelectric conversion device as a conductive layer, the photoelectric conversion efficiency can be improved. Therefore, it can be said that the photoelectric conversion efficiency of the thin film photoelectric conversion device can be improved by applying the present invention.

  As described above, the thin film photoelectric conversion device according to the present invention has a highly crystalline conductive type layer, and a photoelectric conversion efficiency in which an increase in electric resistance and a decrease in electric characteristics due to structural defects in the constituent layers are prevented. It is useful for the manufacture of a thin film photoelectric conversion device excellent in.

DESCRIPTION OF SYMBOLS 1 Translucent insulated substrate 2 Transparent electrode layer 3 Photoelectric conversion cell (front photoelectric conversion cell)
4 Intermediate photoelectric conversion cell 5 Intermediate layer 6 Back photoelectric conversion cell 7 Back surface transparent conductive layer 8 Back surface reflective electrode layer 9 Vacuum chamber 10 Substrate holder (cathode)
11 Shower plate (anode)
DESCRIPTION OF SYMBOLS 12 Vacuum exhaust system 13 Source gas supply part 14 Ion source gas supply part 15 Matching box 16 High frequency power source 17 Ion source 18 Acceleration electrode 19 Deceleration electrode 30 Amorphous layer 31 Thin film crystal conductive type layer 32 Photoelectric conversion layer 33 Conductive type layer 40 Amorphous Layer 41 Thin Film Crystal Conductive Layer 42 Photoelectric Conversion Layer 43 Conductive Type Layer 60 Amorphous Layer 61 Thin Film Crystal Conductive Layer 62 Photoelectric Conversion Layer 63 Conductive Type Layer

Claims (11)

A first step of forming a transparent electrode layer made of a transparent conductive film on a translucent substrate;
A second step of forming an amorphous layer on the transparent electrode layer;
A third step of forming a crystalline first conductivity type layer on the amorphous layer by ion-assisted plasma CVD;
A fourth step of forming a photoelectric conversion layer for converting light into electricity on the crystalline first conductive type layer;
A fifth step of forming a second conductivity type layer on the photoelectric conversion layer;
A sixth step of forming a back-surface reflective electrode layer on the second conductivity type layer;
The manufacturing method of the thin film photoelectric conversion apparatus characterized by including. In the third step, the amorphous layer is partially melted and recrystallized by ion-assisted plasma CVD.
The manufacturing method of the thin film photoelectric conversion apparatus of Claim 1 characterized by these. Forming the amorphous layer and the crystalline first conductive type layer from the same material;
The manufacturing method of the thin film photoelectric conversion apparatus of Claim 1 characterized by these. The thickness of the amorphous layer is 0.1 nm to 50 nm,
The manufacturing method of the thin film photoelectric conversion apparatus of Claim 1 characterized by these. The film thickness of the crystalline first conductivity type layer is 0.1 nm to 50 nm,
The manufacturing method of the thin film photoelectric conversion apparatus of Claim 1 characterized by these. The intensity ratio of the Raman peak in the laser Raman spectroscopy of the crystalline first conductivity type layer to the amorphous layer is 1 to 5,
The manufacturing method of the thin film photoelectric conversion apparatus of Claim 1 characterized by these. On a translucent substrate, a transparent electrode layer made of a transparent conductive film, an amorphous layer, a crystalline first conductive type layer, a photoelectric conversion layer for converting light into electricity, a second conductive type layer, and back reflection An electrode layer,
The intensity ratio of the Raman peak in the laser Raman spectroscopy of the crystalline first conductivity type layer to the amorphous layer is 1 to 5,
A thin film photoelectric conversion device. The amorphous layer and the crystalline first conductive type layer are made of the same material;
The thin film photoelectric conversion device according to claim 7. The amorphous layer has a thickness of 0.1 nm to 50 nm;
The thin film photoelectric conversion device according to claim 7. The film thickness of the crystalline first conductivity type layer is 0.1 nm to 50 nm,
The thin film photoelectric conversion device according to claim 7. The intensity ratio of the Raman peak in the laser Raman spectroscopy of the crystalline first conductivity type layer to the amorphous layer is 1 to 5,
The thin film photoelectric conversion device according to claim 7.

Images