JP2011086731A - Photoelectric conversion apparatus and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a photoelectric conversion apparatus having a superior efficiency of photoelectric conversion, capable of preventing the reduction of efficiency of photoelectric conversion caused by the surface plasmon absorption at a light incoming surface of a back electrode layer and defects of a semiconductor photoelectric conversion layer. <P>SOLUTION: A photoelectric conversion apparatus has: a transparent conductive layer that includes a translucent conductive material and that is formed on a translucent insulating substrate while having an irregular structure; at least a pair of semiconductor photoelectric conversion layers laminated so as to have pin junction on the transparent conductive layer; and a back electrode layer formed on the semiconductor photoelectric conversion layer. An i-type semiconductor layer is configured by laminating a first i-type semiconductor layer formed on the transparent conductive layer and a second i-type semiconductor layer formed on the first i-type semiconductor layer. In the first i-type semiconductor layer, a square average roughness of a surface on the second i-type semiconductor layer side is smaller than that of a surface on the transparent conductive layer side, and a square average roughness of a p-type semiconductor layer or an n-type semiconductor layer arranged on the back electrode layer side in the semiconductor photoelectric conversion layer is smaller than that of a surface of the transparent conductive layer side in the first i-type semiconductor layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion device and a manufacturing method thereof.

  In a conventional photoelectric conversion device, a transparent conductive layer having a concavo-convex shape, a semiconductor photoelectric conversion layer, and a back electrode layer are laminated in this order on a translucent substrate (for example, see Patent Document 1). Moreover, the semiconductor photoelectric conversion layer formed on the transparent conductive layer having an uneven shape has been proposed with different flatness depending on the material (see, for example, Patent Document 2). In Patent Document 2, microcrystalline silicon has an effect of increasing unevenness. When the back electrode side of the tandem solar cell is a microcrystalline silicon semiconductor photoelectric conversion layer, the unevenness between the back electrode and the back electrode increases. It has been shown that the amount of light absorption can be increased.

  In addition, a photoelectric conversion device has been proposed in which the combination of the uneven shape of the electrode interface of the transparent conductive film on the light incident side and the uneven shape of the electrode interface of the back electrode is optimized (see, for example, Patent Document 3). In this photoelectric conversion device, the ratio of the average convex portion height / average convex portion width in the concavo-convex shape of the transparent conductive film is made larger than that of the back electrode, and the reflectance in the long wavelength region at the electrode interface of the back electrode is increased. Reduce. The uneven shape of the back electrode is formed by a method such as sandblasting the surface of the photoelectric conversion layer.

  It has also been proposed to improve the light confinement effect by forming suitable irregularities different from the irregularities on the front surface side on the back side of the photoelectric conversion layer. (For example, refer to Patent Document 4). The uneven shape on the back surface side of the photoelectric conversion layer is formed by depositing conditions when forming the photoelectric conversion layer, or by performing mechanical processing such as sandblasting or etching on the surface of the photoelectric conversion layer.

Japanese Patent No. 2862174 JP 2003-101047 A JP 2002-158366 A JP 2002-141525 A

  However, in the above photoelectric conversion device, the shape of the light incident surface of the back electrode layer is a shape reflecting the uneven shape of the underlying translucent substrate and the shape affected by the uneven growth of the photoelectric conversion layer. There is a problem that it is difficult to form a desired back electrode layer suitable for the light reflection effect.

  In addition, if the photoelectric conversion layer is processed after formation to form a desired concavo-convex shape, there arises a problem that defects are generated near the interface with the back electrode and the photoelectric conversion characteristics are deteriorated.

  The present invention has been made in view of the above, and the photoelectric conversion efficiency is prevented from decreasing due to surface plasmon absorption at the light incident surface of the back electrode layer and defects in the semiconductor photoelectric conversion layer. It aims at obtaining the photoelectric conversion apparatus excellent in conversion efficiency, and its manufacturing method.

  In order to solve the above-described problems and achieve the object, a photoelectric conversion device according to the present invention includes a translucent insulating substrate and a translucent conductive material on the translucent insulating substrate, and has an uneven structure. A transparent conductive layer formed in a state, and at least one set of semiconductor photoelectric layers in which a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are stacked as a semiconductor layer on the transparent conductive layer with a pin junction. A conversion layer; and a back electrode layer formed on the semiconductor photoelectric conversion layer, wherein the i-type semiconductor layer includes a first i-type semiconductor layer formed on the transparent conductive layer, and the first i-type semiconductor. A second i-type semiconductor layer formed on the layer, and the first i-type semiconductor layer has a root mean square roughness of the surface on the second i-type semiconductor layer side of the surface on the transparent conductive layer side. Less than the root mean square roughness in the semiconductor photoelectric conversion layer The root mean square roughness of the p-type semiconductor layer or n-type semiconductor layer disposed on the surface electrode layer side is smaller than the root mean square roughness of the surface on the transparent conductive layer side in the first i-type semiconductor layer, To do.

  According to the present invention, it is possible to prevent a decrease in photoelectric conversion efficiency due to surface plasmon absorption at the light incident surface of the back electrode layer and defects in the semiconductor photoelectric conversion layer, and to provide a photoelectric conversion device excellent in photoelectric conversion efficiency. There is an effect that it can be obtained.

FIG. 1 is a cross-sectional view showing a schematic configuration of a photoelectric conversion apparatus according to an embodiment of the present invention. FIGS. 2-1 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. FIGS. FIGS. 2-2 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. FIGS. FIGS. 2-3 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. FIGS. 2-4 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. 2-5 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. 2-6 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. 2-7 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. 2-8 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. 2-9 is sectional drawing for demonstrating the manufacturing method of the photoelectric conversion apparatus concerning embodiment of this invention. FIG. 3 is a characteristic diagram showing the correlation between RMS and Jsc of the back electrode layer of the solar battery cell.

  Embodiments of a 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 a schematic configuration of a thin-film solar cell which is a photoelectric conversion device according to an embodiment of the present invention. The photoelectric conversion device includes a transparent conductive layer 2, a semiconductor photoelectric conversion layer 3, a back surface side transparent conductive layer 4, and a second electrode that have at least a concavo-convex structure on the surface and serve as a first electrode layer on the translucent insulating substrate 1. The back electrode layer 5 to be a layer is laminated in this order.

  As the translucent insulating substrate 1, an insulating substrate having translucency is used. For such a translucent insulating substrate 1, a material having a high transmittance is usually used, and for example, a glass substrate having a small absorption from the visible to the near infrared region is used. As the glass substrate, an alkali-free glass substrate may be used, or an inexpensive blue plate glass substrate may be used. However, the translucent insulating substrate 1 is not necessarily made of glass, and a substrate made of resin or the like can be used as long as it is an insulating substrate that transmits light.

The transparent conductive layer 2 is made of a transparent conductive film and has an uneven structure. The transparent conductive layer 2 is, for example, a transparent conductive material containing at least one of zinc oxide (ZnO), indium tin oxide (ITO), tin oxide (SnO ₂ ), and indium oxide (In ₂ O ₃ ). It is composed of an oxide film (TCO: Transparent Conducting Oxide) or a transparent conductive film in which these are laminated. In addition, the transparent conductive layer 2 is formed by using aluminum (Al), gallium (Ga), indium (In), boron (B), yttrium (Y), silicon (Si), zirconium (Zr), You may be comprised by the translucent film | membrane using at least 1 or more types of element selected from titanium (Ti) and fluorine (F).

  Such a transparent conductive layer 2 has a surface uneven shape including fine unevenness, and has a function of increasing the light use efficiency in the semiconductor photoelectric conversion layer 3 by irregular reflection of light on the uneven surface. In general, this uneven shape has an average interval between local peaks of several tens of nanometers to several tens of micrometers, an opening angle of concave portions of 10 degrees to 170 degrees, and a root mean square (RMS) roughness at this time is about 100 nm to 500 nm. It has the shape which is, and the unevenness | corrugation of various shapes in this range is included in the surface. Such a transparent electrode layer 2 is formed by sputtering, electron beam deposition, atmospheric pressure chemical vapor deposition (CVD), low pressure CVD, metal organic chemical vapor deposition (MOCVD). It can be produced by various methods such as a Deposition method, a sol-gel method, a printing method, and a spray method.

  The semiconductor photoelectric conversion layer 3 is composed of a non-single-crystal silicon thin film semiconductor layer having a pin junction, and includes a p-type semiconductor layer 3a that is a first-type semiconductor layer, an i-type semiconductor layer 3b that is a second-type semiconductor layer, and a first An n-type semiconductor layer 3 c that is a 3-type semiconductor layer includes a pin semiconductor junction in which the main surface of the translucent insulating substrate 1 is sequentially stacked substantially in parallel. In the i-type semiconductor layer 3b, a first i-type semiconductor layer 3b1 and a second i-type semiconductor layer 3b2 are stacked in this order from the p-type semiconductor layer 3a side. Here, the silicon-based thin film semiconductor layer includes only silicon (Si) or at least one of carbon (C), oxygen (O), germanium (Ge), or other elements containing silicon (Si) as a main component. It means a layer made of a thin film. As the i-type semiconductor layer 3b, a semiconductor layer made of any one of microcrystalline silicon, microcrystalline silicon germanium, amorphous silicon germanium, a microcrystalline silicon oxide film, a single crystal semiconductor, and a polycrystalline semiconductor can be given.

Such a semiconductor photoelectric conversion layer 3 is generally deposited by using a plasma CVD method, a thermal CVD method or the like. At this time, in order to improve the junction characteristics of each layer in the semiconductor photoelectric conversion layer 3, between the p-type semiconductor layer 3a and the i-type semiconductor layer 3b, and between the i-type semiconductor layer 3b and the n-type semiconductor layer 3c, Non-single-crystal silicon (Si) layer, non-single-crystal silicon carbide (Si _x C _1-x ) layer, non-single-crystal silicon nitride (Si _x N _1-x ), non-single-crystal silicon oxide (Si _x O _1-x ) Or the like may be interposed in one layer or two or more layers.

  Further, since the semiconductor photoelectric conversion layer 3 is deposited on the transparent conductive layer 2 having a concavo-convex shape, the semiconductor photoelectric conversion layer 3 has a fine concavo-convex shape reflecting the concavo-convex shape of the transparent conductive layer 2, and its RMS is generally 100 nm. ~ 500 nm. The back electrode layer 5 subsequently deposited on the semiconductor photoelectric conversion layer having such a fine concavo-convex shape has the same fine concavo-convex shape on the surface on the incident light side, so that surface plasmon absorption is performed on the light incident surface. Occurs. As a result, the light reflectance at the back electrode layer is reduced by the surface plasmon absorption, and the photoelectric conversion efficiency is lowered.

  Therefore, in the semiconductor photoelectric conversion layer 3 according to the present embodiment, the semiconductor photoelectric conversion layer is subjected to an unevenness relief process described later. That is, the unevenness relief treatment is applied to the uneven shape on the upper surface (back electrode layer 5 side) of the first i-type semiconductor layer 3b1. The purpose of this treatment is to reduce the surface roughness of the light incident surface of the back electrode layer 5 by relaxing the uneven shape of the semiconductor photoelectric conversion layer. Specifically, the planarization process is performed so that the root mean square roughness on the back electrode layer 5 side of the first i-type semiconductor layer 3b1 is significantly smaller than the root mean square roughness on the translucent insulating substrate 1 side. As described above, the unevenness of the top surface of the first i-type semiconductor layer 3b1 is subjected to the unevenness relief treatment, so that the unevenness of the light incident surface of the back electrode layer 5 formed thereon is relaxed, and the surface plasmon Since light absorption loss due to absorption is suppressed, photoelectric conversion efficiency is improved.

  As a measure of unevenness relief on the upper surface of the first i-type semiconductor layer 3b1, the RMS (root mean square) roughness of the uneven shape after unevenness relief may be about 10 nm to 90 nm, and more preferably about 30 nm to 50 nm. . At this time, the average interval between the concave and convex local peaks and the opening angle of the recess are not particularly limited, but in order to improve the light scattering effect in the visible light to near infrared light region, the average interval between the local peaks is 500 nm to 5 μm, The opening angle of the recess is preferably 90 to 150 degrees. For example, the mean square roughness of the surface on the transparent conductive layer 2 side in the first i-type semiconductor layer 3b1 is 100 nm or more, and the RMS on the surface on the back electrode side 5 side in the n-type semiconductor layer 3c is 50 nm or less. preferable. Thereby, the unevenness | corrugation by the side of the light-incidence in i type semiconductor layer 3b is large, and a photoelectric converting layer can absorb incident light efficiently.

  The first i-type semiconductor layer 3b1 is preferably subjected to a defect repair process on the processed surface of the semiconductor layer after the unevenness relief process. As defect repair processing, in vacuum or silicon (Si) for repairing vacancy defects, hydrogen (H) or nitrogen (N) having a defect termination action, other helium (He), neon (Ne), argon (Ar) ), Krypton (Kr), xenon (Xe), fluorine (F), oxygen (O), carbon (C), etc., plasma treatment, heat treatment, laser irradiation in an atmosphere containing at least one element selected from Alternatively, it is preferable to use a method combining these.

The back-side transparent conductive layer 4 is made of a light-transmitting conductive material, and a transparent conductive film such as tin oxide (SnO ₂ ), zinc oxide (ZnO), or ITO can be used. A small amount of impurities may be added to the film of the back side transparent conductive layer 4. For example, when zinc oxide (ZnO) is the main component, a group IIIB element such as gallium (Ga), aluminum (Al), or boron (B) or a group IV element such as copper (Cu) is contained. This reduces the resistivity and is suitable for use as an electrode. Such a back side transparent conductive layer 4 is formed by an electron beam evaporation method, a sputtering method, an atomic layer deposition method, a CVD method, a sol-gel method, a printing method, a coating method, or the like.

  The back electrode layer 5 preferably reflects more transmitted light in order to use the light transmitted through the semiconductor photoelectric conversion layer 3 again in the semiconductor photoelectric conversion layer. The back electrode layer 5 is made of, for example, at least one selected from titanium (Ti), chromium (Cr), aluminum (Al), silver (Ag), gold (Au), copper (Cu), and platinum (Pt). A layer made of metal or an alloy thereof is used. In addition, the specific material as a metal material of these back surface electrode layers 5 is not specifically limited, It can select from a well-known material suitably and can be used.

  Further, the first i-type semiconductor layer 3b1 is planarized so that the root mean square roughness on the back electrode layer 5 side is significantly smaller than that on the translucent insulating substrate 1 side. The root mean square roughness of the surfaces of the second i-type semiconductor layer 3b2, the back-side transparent conductive layer 4, and the back-side electrode layer 5 that are stacked on the light-transmitting insulating substrate 1 side in the first i-type semiconductor layer 3b1 is also larger than that of the first i-type semiconductor layer 3b1. It is significantly smaller.

  As described above, the photoelectric conversion device according to the present embodiment includes the semiconductor photoelectric conversion layer 3 on which the surface on the back electrode layer 5 side is subjected to the unevenness relief treatment, and thereby the light incident surface of the back electrode layer 5. Also, the shape of the unevenness is relaxed. As a result, the light incident side maximizes the light scattering effect by the transparent conductive layer 2 having a desired concavo-convex shape, and the back side has a light reflectance of surface plasmon absorption on the light incident surface of the back electrode layer 5. The decrease can be suppressed, and the problem of a decrease in photoelectric conversion efficiency can be solved.

  In the photoelectric conversion device according to the present embodiment, since the i-type semiconductor layer 3b is divided into the first i-type semiconductor layer 3b1 and the second i-type semiconductor layer 3b2, the i-type semiconductor layer 3b and n Defects are unlikely to occur near the interface with the type semiconductor layer 3c, and the influence of defects in the semiconductor photoelectric conversion layer 3 can be suppressed. That is, since defects do not concentrate near the interface between the i-type semiconductor layer 3b and the n-type semiconductor layer 3c, the photoelectric conversion rate can be made more efficient. Even if defects are concentrated between the first i-type semiconductor layer 3b1 and the second i-type semiconductor layer 3b2, the i-type semiconductor layer 3b is in the middle of its thickness, and the influence of the defects is suppressed. Therefore, it is preferable that the thickness of the second i-type semiconductor layer 3b2 is somewhat thick. In the present embodiment, the thickness of each layer is considered as the thickness when the surface is the position where the unevenness of each surface is averaged.

  On the other hand, in a microcrystalline semiconductor, in particular, a semiconductor layer containing microcrystalline silicon as a main component, unevenness is likely to increase with film formation. Therefore, it is preferable that the thickness of the second i-type semiconductor layer 3b2 on the back surface side is thin to some extent. From the above, for example, in the case of the i-type semiconductor layer 3 made of microcrystalline silicon having a total thickness of 2 μm to 4 μm, if the thickness of the second i-type semiconductor layer 3b2 is about 50 nm to 500 nm, the influence of defects can be suppressed. It is preferable from the viewpoint of reducing unevenness.

  In the above description, the i-type semiconductor layer 3 is formed in two layers. However, the i-type semiconductor layer 3 may be formed in more layers, and planarization may be performed during the formation of each layer.

  Further, when the i-type semiconductor layer 3 is made of a semiconductor whose main component is a microcrystalline semiconductor such as microcrystalline silicon or microcrystalline silicon germanium, the first i-type semiconductor layer 3b1 and the second i-type semiconductor layer 3b2 are arranged at the interface. An initial growth layer of the 2i type semiconductor layer 3b2 exists (not shown). A microcrystalline semiconductor layer formed at a low temperature by a plasma CVD method or the like is a layer in which microcrystal and amorphous are mixed. In addition, the initial growth layer can be a layer mainly made of amorphous material. For example, in the case of microcrystalline silicon, the initial growth layer is an amorphous silicon layer having a thin thickness of 0.5 nm to 50 nm.

  In the photoelectric conversion device according to the present embodiment, since a flattened initial growth layer is formed, this growth occurs when there is a defect penetrating in the thickness direction in the microcrystalline layer of the first i-type semiconductor layer 3b1. Defects are blocked by the initial layer and do not propagate to the microcrystalline layer of the second i-type semiconductor layer 3b2. For this reason, the performance fall by the defect of a photoelectric converting layer can be suppressed. That is, the microcrystal of the first i-type semiconductor layer 3b1 and the microcrystal of the second i-type semiconductor layer 3b2 are separated by a thin initial growth layer having a thickness of 0.5 nm to 50 nm. For this reason, the defects in the microcrystal of the first i-type semiconductor layer 3b1 generated under the influence of the unevenness of the base do not lead to the microcrystal of the second i-type semiconductor layer 3b2 thereabove. For this reason, since the path of the defect penetrating vertically through the i-type semiconductor layer 3b is reduced, the leakage current that has passed through the defect is reduced, and the conversion efficiency is improved.

  Therefore, according to the photoelectric conversion device according to the present embodiment, a photoelectric conversion device having excellent photoelectric conversion characteristics can be provided.

  Next, a manufacturing method of the photoelectric conversion device according to the present embodiment configured as described above will be described with reference to FIGS. 2-1 to 2-9 are cross-sectional views for explaining the method for manufacturing the photoelectric conversion device according to this embodiment.

  First, a glass substrate is prepared as the translucent insulating substrate 1 (FIG. 2-1). However, the translucent insulating substrate 1 does not necessarily need to be a glass substrate, and a substrate made of resin or the like can be used as long as it is an insulating substrate that transmits light.

  Next, a transparent conductive layer 2 having a surface irregular shape including fine irregularities is formed on the translucent insulating substrate 1 by a known method (FIG. 2-2). For example, the transparent electrode layer 2 made of a zinc oxide (ZnO) film is formed on the translucent insulating substrate 1 by a sputtering method. In general, the uneven shape has an average interval between local peaks of several tens of nanometers to several tens of micrometers, an opening angle of concave portions of 10 degrees to 170 degrees, and a mean square (RMS) roughness of about 100 nm to 500 nm. It has the shape which is, and the unevenness | corrugation of various shapes in this range is included in the surface. Such a transparent electrode layer 2 may be produced by other methods such as an electron beam deposition method, a CVD method, a low pressure CVD method, an MOCVD method, a sol-gel method, a printing method, and a spray method.

  Next, a semiconductor photoelectric conversion layer 3 made of a non-single crystal silicon thin film semiconductor layer having a pin junction is stacked on the transparent conductive layer 2 so as to be substantially parallel to the main surface of the translucent insulating substrate 1. Here, the silicon-based thin film semiconductor layer includes only silicon (Si) or at least one of carbon (C), oxygen (O), germanium (Ge), or other elements containing silicon (Si) as a main component. It means a layer made of a thin film. First, a p-type semiconductor layer 3a is laminated on the transparent conductive layer 2 by, for example, a plasma CVD method so as to be substantially parallel to the main surface of the translucent insulating substrate 1 (FIG. 2-3).

  Next, on the p-type semiconductor layer 3a, the first i-type semiconductor layer 3b1 is laminated and formed substantially parallel to the main surface of the translucent insulating substrate 1 by, for example, plasma CVD (FIG. 2-4). In this embodiment, after the formation of the first i-type semiconductor layer 3b1, the surface of the first i-type semiconductor layer 3b1 is subjected to unevenness relief treatment (FIG. 2-5). That is, the unevenness relief treatment is applied to the uneven shape on the upper surface (back electrode layer 5 side) of the first i-type semiconductor layer 3b1. The purpose of this treatment is to reduce the surface roughness of the light incident surface of the back electrode layer 5 by relaxing the uneven shape of the semiconductor photoelectric conversion layer. Specifically, the planarization process is performed so that the root mean square roughness of the upper surface of the first i-type semiconductor layer 3b1 is significantly smaller than the root mean square roughness of the surface on the translucent insulating substrate 1 side. As described above, the unevenness of the light incident surface of the back electrode layer 5 formed on the upper surface of the first i-type semiconductor layer 3b1 can be reduced by performing the unevenness relief treatment on the unevenness of the upper surface of the first i-type semiconductor layer 3b1. Thereby, since the light absorption loss by surface plasmon absorption can be suppressed, photoelectric conversion efficiency improves.

  The unevenness reduction treatment includes ion milling, focused ion beam (FIB), dry etching, wet etching, reverse sputtering, chemical mechanical polishing (CMP), and the like. It is done by combination. At this time, in order to improve processing accuracy, the unevenness relief treatment may be performed after spin-coating the resist material.

  As a measure of relief of unevenness on the upper surface of the first i-type semiconductor layer 3b1, the RMS (root mean square) roughness of the uneven shape after relaxation may be about 10 nm to 90 nm, and more preferably about 30 nm to 50 nm. At this time, the average interval between the concave and convex local peaks and the opening angle of the recess are not particularly limited, but in order to improve the light scattering effect in the visible light to near infrared light region, the average interval between the local peaks is 500 nm to 5 μm, The opening angle of the recess is preferably 90 to 150 degrees.

  Moreover, it is preferable to perform a defect repair process on the processed surface of the first i-type semiconductor layer 3b1 after the unevenness relief process. As defect repair processing, silicon (Si) for repairing vacancy defects, hydrogen (H) and nitrogen (N) having a defect termination action, other helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), fluorine (F), oxygen (O), at least one element selected from carbon (C), etc., plasma treatment in an atmosphere containing at least one element, heat treatment, laser irradiation, or the like It is preferable to use a method combining the above.

  Next, the second i-type semiconductor layer 3b2 is formed on the first i-type semiconductor layer 3b that has been subjected to the unevenness relief process by, for example, a plasma CVD method so as to be substantially parallel to the main surface of the translucent insulating substrate 1 (FIG. 2). -6). As a result, the i-type semiconductor layer 3b in which the first i-type semiconductor layer 3b1 and the second i-type semiconductor layer 3b2 are stacked in this order on the p-type semiconductor layer 3a is formed.

  Next, on the second i-type semiconductor layer 3b2, an n-type semiconductor layer 3c of the same type as the i-type semiconductor layer 3b is laminated and formed substantially parallel to the main surface of the translucent insulating substrate 1 by, for example, plasma CVD (FIG. 2). -7). As a result, the pin is composed of a non-single-crystal silicon-based thin film semiconductor layer, and the p-type semiconductor layer 3a, the i-type semiconductor layer 3b, and the n-type semiconductor layer 3c are sequentially stacked substantially parallel to the main surface of the translucent insulating substrate 1. A semiconductor photoelectric conversion layer 3 including a semiconductor junction is formed on the transparent conductive layer 2.

In addition, in order to improve the junction characteristics of each layer in the semiconductor photoelectric conversion layer 3, there is a non-between between the p-type semiconductor layer 3 a and the i-type semiconductor layer 3 b and between the i-type semiconductor layer 3 b and the n-type semiconductor layer 3 c. Semiconductors such as single crystal Si layer, non-single crystal silicon carbide (Si _x C _1-x ) layer, non-single crystal silicon nitride (Si _x N _1-x ), non-single crystal silicon oxide (Si _x O _1-x ) One layer or two or more layers may be interposed.

  Next, the back side transparent conductive layer 4 is formed on the semiconductor photoelectric conversion layer 3 (n-type semiconductor layer 3c) by a known method (FIGS. 2-8). For example, the back-side transparent conductive layer 4 made of a zinc oxide (ZnO) film is formed on the semiconductor photoelectric conversion layer 3 (n-type semiconductor layer 3c) by a sputtering method. Further, as a film formation method, another film formation method such as a CVD method may be used.

  Subsequently, the back electrode layer 5 is formed on the back side transparent conductive layer 4 by a known method (FIG. 2-9). For example, the back electrode layer 7 made of a silver (Ag) film having a high reflectance is formed on the back electrode layer 5 by a sputtering method. Here, in the previous step, flattening is performed so that the root mean square roughness of the surface of the first i-type semiconductor layer 3b1 on the back electrode layer 5 side is significantly smaller than the root mean square roughness of the surface on the translucent insulating substrate 1 side. Since the processing is performed, the root mean square roughness of the second i-type semiconductor layer 3b2, the back-side transparent conductive layer 4 and the back-side electrode layer 5 laminated thereon is also on the translucent insulating substrate 1 side of the first i-type semiconductor layer 3b1. It is much smaller than the root mean square roughness. Through the above processing, the photoelectric conversion device according to this embodiment shown in FIG. 1 is obtained.

  As described above, in the method for manufacturing the photoelectric conversion device according to the present embodiment, the surface on the back electrode layer 5 side of the first i-type semiconductor layer 3b1 in the semiconductor photoelectric conversion layer 3 is subjected to unevenness relief treatment. The light incident surfaces of the second i-type semiconductor layer 3b2, the back-side transparent conductive layer 4 and the back-side electrode layer 5 to be laminated also have a shape in which the unevenness is relaxed. As a result, the light incident side maximizes the light scattering effect by the transparent conductive layer 2 having a desired concavo-convex shape, and the back side has a light reflectance of surface plasmon absorption on the light incident surface of the back electrode layer 5. The decrease can be suppressed, and the problem of a decrease in photoelectric conversion efficiency can be solved.

  Further, in the method of manufacturing the photoelectric conversion device according to the present embodiment, the i-type semiconductor layer 3b is divided into the first i-type semiconductor layer 3b1 and the second i-type semiconductor layer 3b2, so that the i-type semiconductor layer 3b Defects are unlikely to occur near the interface with the n-type semiconductor layer 3c, and the influence of defects in the semiconductor photoelectric conversion layer 3 can be suppressed. Therefore, it is preferable that the thickness of the second i-type semiconductor layer 3b2 is somewhat thick. In the above description, the i-type semiconductor layer 3 is formed in two layers. However, the i-type semiconductor layer 3 may be formed in more layers, and planarization may be performed during the formation of each layer.

  When the i-type semiconductor layer 3 is made of a microcrystalline semiconductor such as microcrystalline silicon or microcrystalline silicon germanium, the second i-type semiconductor layer 3b2 is connected to the interface between the first i-type semiconductor layer 3b1 and the second i-type semiconductor layer 3b2. There is an initial growth layer (not shown). A microcrystalline semiconductor layer formed at a low temperature by a plasma CVD method or the like is a layer in which microcrystal and amorphous are mixed. In addition, the initial growth layer can be a layer mainly made of amorphous material. For example, in the case of microcrystalline silicon, the initial growth layer is an amorphous silicon layer having a thin thickness of 0.5 nm to 50 nm.

  In the manufacturing method of the photoelectric conversion device according to the present embodiment, since a flattened initial growth layer is formed, when there is a defect penetrating in the thickness direction in the microcrystalline layer of the first i-type semiconductor layer 3b1. The defects are blocked by this initial growth layer and do not propagate to the microcrystalline layer of the second i-type semiconductor layer 3b2. For this reason, the performance fall by the defect of a photoelectric converting layer can be suppressed.

  Therefore, according to the method for manufacturing a photoelectric conversion device according to this embodiment, a photoelectric conversion device having excellent photoelectric conversion characteristics can be manufactured.

  In the above description, a photoelectric conversion device having a semiconductor photoelectric conversion layer has been described as an example of an embodiment of the present invention. However, the present invention is not limited to this and does not depart from the gist of the invention. As long as it can be in any form. That is, the present invention is not limited to, for example, a photoelectric conversion device having one semiconductor photoelectric conversion layer, and can also be applied to a tandem photoelectric conversion device in which two or more semiconductor photoelectric conversion layers are stacked. The present invention is not limited to a photoelectric conversion device having, for example, a silicon-based semiconductor photoelectric conversion layer, and can also be applied when the semiconductor photoelectric conversion layer uses a compound-based or organic-based semiconductor.

  Next, although this invention is demonstrated based on a specific Example, this invention is not limited to a following example, unless it deviates from the summary.

Example 1.
In Example 1, a photoelectric conversion device was manufactured according to the method for manufacturing a photoelectric conversion device according to this embodiment described above. As the translucent insulating substrate 1, a glass substrate having a thickness of 5 mm was used. A zinc oxide (ZnO) film doped with about 2 × 10 ²¹ cm ⁻³ of aluminum (Al) atoms as impurities was formed with a thickness of 1 μm on a glass substrate by a sputtering method. And the transparent conductive layer 2 which has the uneven structure of the light-receiving surface side was formed by implementing the etching process of a zinc oxide (ZnO) film | membrane for 60 second using hydrochloric acid diluted to 0.5% as a chemical | medical solution. At this time, the RMS of the surface of the transparent conductive layer 2 after etching was 200 nm.

  Next, of the semiconductor photoelectric conversion layer 3, a p-type microcrystalline silicon film with a thickness of 20 nm and an i-type microcrystalline silicon film with a thickness of 3 μm as the first i-type semiconductor layer 3 b 1 are formed on the transparent conductive layer 2 by plasma CVD. Laminated by the method. Then, after depositing the i-type microcrystalline silicon film, an unevenness relief process was performed on the i-type microcrystalline silicon layer as the first i-type semiconductor layer 3b1. Photoresist was applied to 500 nm and baked at 100 ° C. After baking, dry etching was performed for 300 seconds to remove the photoresist.

  Next, annealing was performed for 2 hours in a hydrogen gas atmosphere. Next, an i-type microcrystalline silicon layer having a thickness of 100 nm and a n-type microcrystalline silicon film having a thickness of 30 nm as the second i-type semiconductor layer 3b2 are formed on the etched i-type semiconductor layer as the first i-type semiconductor layer 3b1. Were laminated by the plasma CVD method.

Next, as the back side transparent conductive layer 4, a zinc oxide (ZnO) film doped with about 2 × 10 ²¹ cm ⁻³ of aluminum (Al) atoms as impurities was formed to a thickness of 100 nm by a sputtering method. At this time, as a result of evaluating the uneven shape of the back surface side transparent conductive layer 4 on the back electrode 5 side using an atomic force microscope (AFM), the RMS roughness was estimated to be 51 nm. The RMS roughness of the incident light side unevenness of the back electrode layer described later is substantially equal to the estimated RMS roughness of the unevenness of the back surface transparent conductive layer 4 on the back electrode layer 5 side.

  Next, on the zinc oxide (ZnO) film | membrane as the back surface side transparent conductive layer 4, the film which forms the film as a back electrode layer 5 with a film thickness of 500 nm by the sputtering method, and has the structure shown by FIG. 1 photoelectric conversion cell was produced.

As a result of evaluating the cell characteristics of the produced photoelectric conversion cell of Example 1, the conversion efficiency (η) was 6.8%, the short-circuit current density (Jsc) was 19.5 mA / cm ² , and the open-circuit voltage (Voc) was 0. .50 V and fill factor (FF) was 0.70.

Example 2
In Example 2, a photoelectric conversion cell was produced in the same manner as in Example 1 except that the etching time of the etching process after deposition of the i-type microcrystalline silicon layer as the first i-type semiconductor layer 3b1 was different (600 seconds). . That is, in Example 2, the dry etching process after the deposition of the i-type microcrystalline silicon layer as the first i-type semiconductor layer 3b1 was performed for 600 seconds, and then the annealing process was performed for 2 hours in a hydrogen gas atmosphere. Thereafter, an i-type microcrystalline silicon layer having a thickness of 100 nm and an n-type microcrystalline silicon having a thickness of 30 nm as the second i-type semiconductor layer 3b2 are formed on the etched i-type microcrystalline silicon film as the first i-type semiconductor layer 3b1. The film was laminated by a plasma CVD method.

Next, as the back side transparent conductive layer 4, a zinc oxide (ZnO) film doped with about 2 × 10 ²¹ cm ⁻³ of aluminum (Al) atoms as impurities was formed to a thickness of 100 nm by a sputtering method. At this time, as a result of evaluating the concavo-convex shape on the back surface electrode 5 side of the back surface side transparent conductive layer 4 using an atomic force microscope (AFM), the RMS roughness was estimated to be 18 nm.

  Next, on the zinc oxide (ZnO) film | membrane as the back surface side transparent conductive layer 4, the film which forms the film as a back electrode layer 5 with a film thickness of 500 nm by the sputtering method, and has the structure shown by FIG. 2 photoelectric conversion cells were produced.

As a result of evaluating the cell characteristics of the produced photoelectric conversion cell of Example 2, the conversion efficiency (η) was 7.2%, the short-circuit current density (Jsc) was 19.9 mA / cm ² , and the open-circuit voltage (Voc) was 0. .51 V and the fill factor (FF) was 0.71.

Comparative Example 1
In Comparative Example 1, a photoelectric conversion cell in which an i-type microcrystalline silicon layer as the second i-type semiconductor layer 3b2 was not formed was manufactured. As the translucent insulating substrate 1, a glass substrate having a thickness of 5 mm was used. A zinc oxide (ZnO) film doped with about 2 × 10 ²¹ cm ⁻³ of aluminum (Al) atoms as impurities was formed with a thickness of 1 μm on a glass substrate by a sputtering method. And the transparent conductive layer 2 which has the uneven structure of the light-receiving surface side was formed by implementing the etching process of a zinc oxide (ZnO) film | membrane for 60 second using hydrochloric acid diluted to 0.5% as a chemical | medical solution. At this time, the RMS of the surface of the transparent conductive layer 2 after etching was 200 nm.

  Next, of the semiconductor photoelectric conversion layer 3, a p-type microcrystalline silicon film with a thickness of 20 nm and an i-type microcrystalline silicon film with a thickness of 3 μm as the first i-type semiconductor layer 3 b 1 are formed on the transparent conductive layer 2 by plasma CVD. Laminated by the method. Then, after depositing the i-type microcrystalline silicon film, 1 μm of a photoresist was applied and baked at 100 ° C. After baking, dry etching was performed for 300 seconds to remove the photoresist.

  Next, annealing was performed for 2 hours in a hydrogen gas atmosphere. Next, an n-type microcrystalline silicon film having a thickness of 30 nm was stacked on the i-type semiconductor layer as the etched first i-type semiconductor layer 3b1 by a plasma CVD method.

Next, as the back side transparent conductive layer 4, a zinc oxide (ZnO) film doped with about 2 × 10 ²¹ cm ⁻³ of aluminum (Al) atoms as impurities was formed to a thickness of 100 nm by a sputtering method. At this time, as a result of evaluating the concavo-convex shape on the back surface electrode 5 side of the back surface side transparent conductive layer 4 using an atomic force microscope (AFM), the RMS roughness was estimated to be 47 nm. The RMS roughness of the incident light side uneven shape of the back electrode layer 5 described later substantially matches the estimated RMS roughness of the uneven shape of the back surface transparent conductive layer 4 on the back electrode layer 5 side.

  Next, on the zinc oxide (ZnO) film as the back surface side transparent conductive layer 4, the photoelectric conversion cell of the comparative example 1 was produced by forming silver into a film thickness of 500 nm as a back surface electrode layer 5 by sputtering method. .

As a result of evaluating the cell characteristics of the produced photoelectric conversion cell of Comparative Example 1, the conversion efficiency (η) was 6.5%, the short-circuit current density (Jsc) was 18.7 mA / cm ² , and the open-circuit voltage (Voc) was 0. .50 V and fill factor (FF) was 0.70.

Comparative Example 2
In Comparative Example 2, a photoelectric conversion cell was produced in the same manner as in Example 1 except that the etching time of the etching process after deposition of the i-type microcrystalline silicon layer as the first i-type semiconductor layer 3b1 was different (30 seconds). . That is, in Comparative Example 2, the dry etching process after the deposition of the i-type microcrystalline silicon layer as the first i-type semiconductor layer 3b1 was performed for 30 seconds, and then the annealing process was performed for 2 hours in a hydrogen gas atmosphere. Thereafter, an i-type microcrystalline silicon layer having a thickness of 100 nm and an n-type microcrystalline silicon having a thickness of 30 nm as the second i-type semiconductor layer 3b2 are formed on the etched i-type microcrystalline silicon film as the first i-type semiconductor layer 3b1. The film was laminated by a plasma CVD method.

Next, as the back side transparent conductive layer 4, a zinc oxide (ZnO) film doped with about 2 × 10 ²¹ cm ⁻³ of aluminum (Al) atoms as impurities was formed to a thickness of 100 nm by a sputtering method. At this time, as a result of evaluating the concavo-convex shape on the back surface electrode 5 side of the back surface side transparent conductive layer 4 using an atomic force microscope (AFM), the RMS roughness was estimated to be 98 nm.

  Next, on the zinc oxide (ZnO) film | membrane as the back surface side transparent conductive layer 4, the film which forms the film as a back electrode layer 5 with a film thickness of 500 nm by the sputtering method, and has the structure shown by FIG. 2 photoelectric conversion cells were produced.

As a result of evaluating the cell characteristics of the produced photoelectric conversion cell of Example 2, the conversion efficiency (η) was 5.8%, the short-circuit current density (Jsc) was 16.8 mA / cm ² , and the open-circuit voltage (Voc) was 0. .49 V and fill factor (FF) was 0.70.

  According to the comparison between Example 1 and Comparative Example 1 described above, the short-circuit current density (Jsc) of the photoelectric conversion device was improved by laminating the i-type semiconductor layer again after the unevenness relaxation treatment of the i-type microcrystalline silicon layer. I understand that. This is because defects are concentrated at the interface between the i-type semiconductor layer and the n-type semiconductor layer when the n-type semiconductor layer is formed after the unevenness relief treatment of the i-type semiconductor layer, whereas the unevenness relief treatment of the i-type semiconductor layer again. This is because by laminating the i-type semiconductor layer, a decrease in electrical junction characteristics at the interface between the i-type semiconductor layer and the n-type semiconductor layer is suppressed.

  FIG. 3 shows the result of comparing the RMS and cell characteristics of Example 1, Example 2, and Comparative Example 1, and in addition, the correlation between the RMS and Jsc of the back electrode layer of various other solar cells. It is a characteristic view which shows the result of having investigated. Other various solar battery cell configurations and manufacturing methods are the same as those in Comparative Example 1.

  As shown in FIG. 3, the short-circuit current density (Jsc) showed a high value when RMS was 50 nm or less, and the short-circuit current density (Jsc) was particularly high when RMS was 20 nm or less. This can be explained as follows. The surface plasmon absorption on the silver surface shows the maximum value due to surface plasmon resonance at a light wavelength of 300 nm to 500 nm. In the visible light to near-infrared light region having a wavelength longer than the maximum wavelength, the amount of light absorption increases as the RMS on the silver surface increases. That is, as the RMS on the light incident side of the back electrode layer is smaller, the light absorption in the back electrode layer is reduced, and as a result, the conversion efficiency of the photoelectric conversion device is improved.

  As described above, the photoelectric conversion device according to the present invention is useful for preventing a decrease in photoelectric conversion efficiency due to surface plasmon absorption at the light incident surface of the back electrode layer and defects in the semiconductor photoelectric conversion layer.

DESCRIPTION OF SYMBOLS 1 Translucent insulated substrate 2 Transparent conductive layer 3 Semiconductor photoelectric conversion layer 3a p-type semiconductor layer 3b i-type semiconductor layer 3c n-type semiconductor layer 3b1 1i-type semiconductor layer 3b2 2i-type semiconductor layer 4 Back surface side transparent conductive layer 5 Back electrode Layer 10 Photoelectric conversion device

Claims (8)

A translucent insulating substrate;
A transparent conductive layer formed of a translucent conductive material and having a concavo-convex structure on the translucent insulating substrate;
At least one pair of semiconductor photoelectric conversion layers in which a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are stacked as a semiconductor layer on the transparent conductive layer with a pin junction;
A back electrode layer formed on the semiconductor photoelectric conversion layer;
With
The i-type semiconductor layer is formed by laminating a first i-type semiconductor layer formed on the transparent conductive layer and a second i-type semiconductor layer formed on the first i-type semiconductor layer.
The first i-type semiconductor layer has a root mean square roughness on the surface on the second i-type semiconductor layer side that is smaller than the root mean square roughness on the surface on the transparent conductive layer side,
The root mean square roughness of the p-type semiconductor layer or n-type semiconductor layer disposed on the back electrode layer side in the semiconductor photoelectric conversion layer is greater than the root mean square roughness of the surface on the transparent conductive layer side in the first i-type semiconductor layer. Is also small,
A photoelectric conversion device characterized by the above. The i-type semiconductor layer is a semiconductor layer made of any one of microcrystalline silicon, microcrystalline silicon germanium, amorphous silicon germanium, microcrystalline silicon oxide film, single crystal semiconductor, and polycrystalline semiconductor;
The photoelectric conversion device according to claim 1. The first i-type semiconductor layer and the second i-type semiconductor layer are semiconductor layers containing a microcrystalline semiconductor as a main component;
Having an initial growth layer of the second i-type semiconductor layer mainly composed of an amorphous semiconductor at the interface between the first i-type semiconductor layer and the second i-type semiconductor layer;
The photoelectric conversion device according to claim 1. The root mean square roughness of the surface on the back electrode side in the i-type semiconductor layer or the n-type semiconductor layer of the semiconductor photoelectric conversion layer is 50 nm or less,
The photoelectric conversion device according to claim 1. The root mean square roughness on the transparent conductive layer side in the first i-type semiconductor layer is 100 nm or more, and the RMS on the back electrode side in the n-type semiconductor layer is 50 nm or less,
The photoelectric conversion device according to claim 1. A backside transparent conductive layer made of a translucent conductive material is provided between the semiconductor photoelectric conversion layer and the backside electrode layer;
The photoelectric conversion device according to claim 1. A first step of forming a transparent conductive layer made of a light-transmitting conductive material and having a concavo-convex structure on a light-transmitting insulating substrate;
A second step of forming at least one set of semiconductor photoelectric conversion layers having a pin junction by stacking a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer as semiconductor layers on the transparent conductive layer;
A third step of forming a back electrode layer on the semiconductor photoelectric conversion layer;
Including
The step of forming the i-type semiconductor layer in the second step includes
A fourth step of forming a first i-type semiconductor layer on a p-type semiconductor layer or an n-type semiconductor layer formed on the transparent conductive layer;
A fifth step of performing unevenness relief treatment for relaxing unevenness on the upper surface of the first i-type semiconductor layer;
A sixth step of forming a second i-type semiconductor layer on the first i-type semiconductor layer subjected to the unevenness relief treatment;
A process for producing a photoelectric conversion device, comprising: In the fifth step, the upper surface of the first i-type semiconductor layer is vacuum or silicon (Si), hydrogen (H), nitrogen (N), helium (He), neon (Ne), argon (Ar). Plasma treatment, heat treatment or laser irradiation treatment in an atmosphere containing at least one element selected from krypton (Kr), xenon (Xe), fluorine (F), oxygen (O), and carbon (C) Performing one or more processing steps of
The method for manufacturing a photoelectric conversion device according to claim 7.

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