JP2011014736A - Thin film photoelectric conversion device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin film photoelectric conversion device which has high reliability and has unevenness effective for optical confinement.SOLUTION: The thin film photoelectric conversion device includes a structure wherein a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, and a second electrode are arranged in order from a side close to a substrate, wherein a base layer is included between the substrate and first electrode and has fine periodical unevenness in a direction parallel with one principal surface of the substrate.

Description

  The present invention relates to a thin film photoelectric conversion device and a manufacturing method thereof. More specifically, the present invention relates to a thin film photoelectric conversion device having a concavo-convex structure that is highly reliable and effective for light confinement, and a manufacturing method thereof.

  Photoelectric conversion devices are used in various fields such as light receiving sensors and solar cells. In particular, solar cells are in the limelight as one of the earth-friendly energy sources, and the spread of solar cells is rapidly progressing due to the recent growing interest in environmental issues and the introduction acceleration policies of each country.

  Among photoelectric conversion devices, thin film photoelectric conversion devices that require less raw materials in order to achieve both low cost and high efficiency of photoelectric conversion devices including solar cells have attracted attention and are being energetically developed. In particular, a method of forming a high-quality semiconductor layer on an inexpensive substrate such as glass using a low-temperature process is expected as a method capable of realizing low cost.

  In general, in order to form a photoelectric conversion device, it is indispensable to use a transparent conductive film for a part thereof. The photoelectric conversion device includes one or more photoelectric conversion units between the transparent conductive film and the back electrode layer, and light is incident from the transparent conductive film side.

  Here, the photoelectric conversion unit is composed of a pn junction or pin junction semiconductor layer. When a pin junction is used for a photoelectric conversion unit, a p-type layer, an i-type layer, and an n-type layer are laminated in this order or vice versa, and the i-type photoelectric conversion layer occupying the main part is amorphous. Are called amorphous photoelectric conversion units, and those having an i-type layer crystalline are called crystalline photoelectric conversion units.

The transparent conductive film is made of a conductive metal oxide such as ITO (indium tin oxide), SnO ₂ , or ZnO, and is formed by a method such as CVD (Chemical Vapor Deposition), sputtering, or vapor deposition. The transparent conductive film desirably has an effect of increasing the scattering of incident light by having fine irregularities on the surface. By scattering incident light, the optical path length in the photoelectric conversion unit is extended, the short-circuit current density of the photoelectric conversion device is increased, and the conversion efficiency is improved. The effect of light scattering due to the unevenness of the transparent conductive film is not only effective in a so-called bulk photoelectric conversion device in which the thickness of a photoelectric conversion unit such as single crystal silicon or polycrystalline silicon is as thick as 100 to 500 μm, This is particularly effective for a so-called thin film photoelectric conversion device in which the thickness of the conversion unit is as thin as 0.1 to 10 μm.

Thin film photoelectric conversion devices are classified according to the semiconductor material used for the photoelectric conversion unit, and silicon based thin film photoelectric conversion devices, CdTe thin film photoelectric conversion devices, and CIS thin film photoelectric conversion devices are representative. A silicon-based thin film photoelectric conversion device has a pin junction configuration using amorphous silicon, microcrystalline silicon, polycrystalline silicon, or the like as a material for a photoelectric conversion unit, and emits light from the substrate side or the opposite side of the substrate. Incident and the p-layer is disposed on the light incident side. The CdTe thin film photoelectric conversion device has a configuration of a pn junction made of n-type CdS and p-type CdTe in a photoelectric conversion unit, light is incident from the side opposite to the substrate, and an n layer is disposed on the light incident side. . The CIS thin film photoelectric conversion device has a pn junction structure composed of n-type CdS and p-type CuInSe ₂ (abbreviated as CIS) in the photoelectric conversion unit. Arrange on the incident side.

  A silicon-based thin film photoelectric conversion device which is an example of a thin film photoelectric conversion device uses a pin junction including a p-type layer, an i-type layer which is a substantially intrinsic photoelectric conversion layer, and an n-type layer as a photoelectric conversion unit. Among these, those using amorphous silicon for the i-type layer are called amorphous silicon photoelectric conversion units, and those using crystalline silicon are called crystalline silicon photoelectric conversion units. Note that as the amorphous or crystalline silicon-based material, not only a case where only silicon is used as a main element constituting a semiconductor, but also an alloy material including elements such as carbon, oxygen, nitrogen, germanium, and the like can be used. The main constituent material of the conductive layer is not necessarily the same as that of the i-type layer. For example, amorphous silicon carbide can be used for the p-type layer of the amorphous silicon photoelectric conversion unit, and n A silicon layer (also referred to as μc-Si) containing crystal in the mold layer can also be used.

  A plate-like member or a sheet-like member made of glass, transparent resin, or the like is used for a transparent insulating substrate used in a photoelectric conversion device of a type in which light enters from the substrate side.

As the back electrode layer formed on the photoelectric conversion unit, for example, a metal layer such as Al or Ag is formed by sputtering or vapor deposition. Further, a layer made of a conductive oxide such as ITO, SnO ₂ , or ZnO may be formed between the photoelectric conversion unit and the metal electrode.

  An amorphous silicon photoelectric conversion device, which is an example of a thin film photoelectric conversion device, has a problem that the initial photoelectric conversion efficiency is lower than that of a single crystal or polycrystalline photoelectric conversion device, and further, the conversion efficiency is lowered due to a photodegradation phenomenon. Therefore, a crystalline silicon thin film photoelectric conversion device using crystalline silicon such as thin film polycrystalline silicon or microcrystalline silicon as a photoelectric conversion layer is expected to be able to achieve both low cost and high efficiency. Has been. This is because the crystalline silicon thin film photoelectric conversion device can be formed at a low temperature by the plasma CVD method similarly to the formation of amorphous silicon, and the light deterioration phenomenon hardly occurs. The amorphous silicon photoelectric conversion layer can photoelectrically convert light having a wavelength of about 800 nm on the long wavelength side, while the crystalline silicon photoelectric conversion layer photoelectrically converts light having a longer wavelength of about 1200 nm. can do.

  As a method for improving the conversion efficiency of a photoelectric conversion device, a photoelectric conversion device employing a structure called a stacked type in which two or more photoelectric conversion units are stacked is known. In this method, a front photoelectric conversion unit including a photoelectric conversion layer having a large optical forbidden bandwidth is arranged on the light incident side of the photoelectric conversion device, and a rear photoelectric conversion including a photoelectric conversion layer having a small band gap in order behind the photoelectric conversion layer. By arranging the conversion unit, photoelectric conversion over a wide wavelength range of incident light is possible, and the conversion efficiency of the entire apparatus is improved by effectively using incident light. In the present invention, the photoelectric conversion unit disposed relatively on the light incident side is referred to as a front photoelectric conversion unit, and the photoelectric conversion unit disposed adjacent to the interface farther from the light incident side than this. The conversion unit is called a rear photoelectric conversion unit.

  By the way, the thin film photoelectric conversion device can make the photoelectric conversion layer thinner than the photoelectric conversion device using the conventional bulk single crystal or polycrystalline silicon, but on the other hand, the light absorption of the entire thin film is the film thickness. There is a problem that it is limited by. Therefore, in order to use light incident on the photoelectric conversion unit including the photoelectric conversion layer more effectively, the surface of the transparent conductive film or metal layer in contact with the photoelectric conversion unit is made uneven (also referred to as texturing), and at the interface. After scattering light, the optical path length is extended by making it enter into a photoelectric conversion unit, and the device which makes the light absorption amount in a photoelectric converting layer increase is made | formed. This technique is called “optical confinement”, and is an important elemental technique for practical use of a thin film photoelectric conversion device having high photoelectric conversion efficiency.

  In order to obtain the concavo-convex shape of the transparent conductive film optimum for the photoelectric conversion device, an index that quantitatively indicates the concavo-convex shape is necessary. There is a haze ratio as an index representing the shape of the unevenness.

  The haze ratio is an index for optically evaluating the unevenness of a transparent substrate, and is expressed by (diffuse transmittance / total light transmittance) × 100 [%] (JIS K7136). The haze ratio can be easily measured by commercially available haze meters that automatically measure the haze ratio. As a light source for measurement, what is measured using a C light source is generally used.

An amorphous silicon photoelectric conversion device which is an example of a thin-film photoelectric conversion device often uses a tin oxide (SnO ₂ ) film formed on a transparent substrate such as glass and having surface irregularities as a transparent conductive film. However, the size of the unevenness of the SnO ₂ film by the ordinary atmospheric pressure CVD method (normal pressure thermochemical vapor deposition method) varies, and the unevenness effective for light confinement is designed with good controllability. It is difficult. In addition, it is difficult to control the haze ratio, which is an index indicating average unevenness, with a high reproducibility, and there is a problem in that the haze ratio has a distribution in the plane of the substrate and varies among production lots. Also, the effect of light confinement is insufficient and there is room for improvement. Further, a glass substrate on which an SnO ₂ film is formed by atmospheric pressure CVD as a transparent conductive film having surface irregularities effective for light confinement requires a high-temperature process of about 550 to 650 ° C. to form the transparent conductive film. Therefore, there is a problem that the manufacturing cost is high. In addition, since the film forming temperature is high, there is a problem that an inexpensive substrate such as glass or plastic film after solidification cannot be used. When tempered glass is exposed to a high-temperature process, it can be tempered, so it is not possible to use tempered glass as a substrate. As a result, there is a problem of becoming heavy.

In addition, the SnO ₂ film has low plasma resistance, and the SnO ₂ film is reduced in the deposition environment of the photoelectric conversion layer at a high plasma density using hydrogen. When the SnO ₂ film is reduced, the SnO ₂ film is blackened, and the incident light is absorbed by the blackened transparent conductive film portion, the amount of transmitted light to the photoelectric conversion layer is reduced, which causes a decrease in conversion efficiency.

On the other hand, zinc oxide (ZnO) has advantages that it is cheaper than SnO ₂ or indium tin oxide (ITO), which are widely used as a material for transparent conductive films, and has high plasma resistance. It is suitable as a transparent conductive film material for solar cells. In particular, crystalline silicon such as thin-film polycrystalline silicon or microcrystalline silicon that uses a larger amount of hydrogen than the deposition conditions used when forming amorphous silicon and requires a large plasma density is used as one of the photoelectric conversion units. It is effective for a crystalline silicon thin film photoelectric conversion device used as a part.

  As a method for forming irregularities effective for light confinement in a ZnO film, it is known that when a ZnO film is formed by a low-pressure thermal CVD method (also called MOCVD method) of 200 ° C. or less, a transparent conductive film having irregularities can be formed at a low temperature. ing. However, there is a problem that the size of the unevenness of the ZnO film formed by the low pressure thermal CVD method varies. In addition, even in the haze ratio, which is an index indicating average unevenness, the shape of the unevenness changes sensitively under the conditions of the low-pressure thermal CVD method, and it is difficult to control the unevenness with good reproducibility. There is a problem in that there is a distribution within, and there are variations in production lots.

  Further, a method is known in which a ZnO film is formed by sputtering, and then the ZnO film is roughened by wet etching. However, there is a problem that the unevenness of the ZnO film due to sputtering and etching varies. Also, in the haze ratio, which is an index indicating average unevenness, the shape of the unevenness changes sensitively under wet etching conditions, and it is difficult to control the unevenness with good reproducibility. There is a problem in that there is a distribution or variation in production lots.

  Recently, as a method for forming fine unevenness, nanoimprint technology that transfers uneven patterns by pressing fine unevenness of several tens of nanometers to several μm against a workpiece is an alternative to patterning technology by resist UV exposure. Application to is expected.

  In addition, as a method of using the nanoimprint technology optically, application to an antireflection coating (AR) layer has been studied. For example, when light is incident on a glass having a refractive index of 1.5 from an air having a refractive index of 1, an ordinary AR layer having no irregularities has a refractive index of 1.25 between them and a quarter of the wavelength. Coating thickness. On the other hand, when an uneven film having a pitch sufficiently smaller than the wavelength of light is formed using nanoimprint, the uneven film substantially exhibits an intermediate refractive index between air and the uneven film material, and reduces the reflectance. Demonstrate. Since it has the same structure as the surface of the eye of the eyelid, it is also referred to as a “moth eye” structure.

  In the specification of the present application, the terms “crystalline” and “microcrystal” include those partially including amorphous.

(Prior Example 1)
Patent Document 1 discloses a solar cell having a structure of translucent substrate / transparent conductive film / pin junction and having an amorphous silicon layer / Ag electrode structure. The transparent conductive film on the translucent substrate has an uneven gold with a pitch of 300 nm or less. A method is disclosed in which a mold is pressed to make the transparent conductive film uneven. Specifically, a method for forming a transparent conductive film is a so-called thermal nanoimprint in which a concavo-convex pattern is transferred by pressing a mold with a concavo-convex pitch of 100 nm on an In ₂ O ₃ —SnO ₂ sol-gel material applied to a substrate and heating it. Unevenness is formed using the method. By forming irregularities with a periodic structure with a pitch smaller than the wavelength of incident light of the solar cell in the transparent conductive film, reflection at the interface between the transparent conductive film and the amorphous silicon layer is suppressed, forming a so-called non-reflective layer, It is said that the solar cell characteristics are improved by reducing the reflection loss of sunlight.

(Prior Example 2)
In Patent Document 2, a mixed liquid containing a siloxane component, particularly hydrogen silsesquioxane resin (HSQ), is applied to a substrate, a mold having fine irregularities is pressed against the coated surface at room temperature, and the irregular pattern is transferred. A method for forming irregularities of silicon oxide using a so-called room temperature nanoimprint method is disclosed. Specific application methods include application to dry etching mask patterns and quantum devices (single-electron transistors, quantum magnetic disks).

(Prior Example 3)
Patent Document 3 discloses that the surface of the transparent electrode layer can be a random wavy curve to increase the optical path length of light entering the semiconductor layer and increase the generated current. Specifically, it is a photoelectric conversion device in which a concavo-convex underlayer of SiO ₂ , an ITO transparent electrode layer, an amorphous silicon pin structure semiconductor layer, and an Al electrode layer are laminated on a smooth glass substrate in this order.

JP 2008-153570 A Japanese Patent Laid-Open No. 2003-100609 JP 61-44476 A

  An object of the present invention is to provide a thin film photoelectric conversion device having high reliability and unevenness effective for light confinement.

  When unevenness is formed on the transparent electrode layer by film forming conditions or etching, there are problems that the size of the unevenness varies, it is difficult to control the reproducibility of the unevenness, and light confinement is not sufficient.

  In addition, when a moth-eye structure is created on the light-receiving surface side of a glass substrate of a thin film photoelectric conversion device by a nanoimprint method, in a thin film photoelectric conversion device, particularly a thin film solar cell, which is premised on long-term outdoor use, The concavo-convex structure is prone to water and dust, and is difficult to remove once attached, making it impossible to exhibit the AR effect. In addition, there is a problem that the fine unevenness is damaged and the AR effect cannot be exhibited. Furthermore, when a moth-eye structure is created using the UV nanoimprint method, there is a problem that the transmittance with respect to ultraviolet rays is reduced and the amount of incident light on the thin-film solar cell is reduced.

  On the other hand, in the first example, a fine uneven structure having a pitch of 300 nm or less is formed on the transparent conductive film by thermal nanoimprint, and the fine uneven structure is not exposed on the surface. There is little worry of. However, sol-gel ITO is used for the transparent electrode layer, which generally has a high resistivity and a low transmittance, making it difficult to obtain a good quality transparent electrode layer. On the other hand, a transparent electrode layer with low resistivity and high transmittance is formed by sputtering, vapor deposition, atmospheric pressure CVD, low temperature CVD, etc. Is solidified, and it is difficult to form irregularities by the nanoimprint method.

  In addition, a workpiece used for thermal nanoimprinting or UV nanoimprinting is generally an organic resin, and there is a problem that it does not have heat resistance of 200 ° C. or higher. For this reason, there exists a problem which cannot be utilized for the thin film photoelectric conversion apparatus which has a 150-300 degreeC thermal process in a process.

  Prior Example 2 discloses a method for forming irregularities of silicon oxide by room temperature nanoimprinting using HSQ, but does not show an optical application method.

  In view of the above problems, an object of the present invention is to provide a thin film photoelectric conversion device having improved characteristics by a concavo-convex structure that is reliable for long-term outdoor use and has an enhanced light confinement effect.

  The thin film photoelectric conversion device of the present invention is a thin film photoelectric conversion device including a structure in which a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, and a second electrode layer are sequentially arranged from the side closer to the substrate. Thus, the problem is solved by including an underlayer between the substrate and the first electrode, and the underlayer having fine periodic irregularities in a direction parallel to one main surface of the substrate. Since the fine periodic unevenness is not exposed on the surface of the thin film photoelectric conversion device, there is no problem of the unevenness of the uneven layer or damage even when used outdoors for a long time. Also, the thin periodic photoelectric unevenness of the underlayer is effectively scattered by the light incident on the thin film photoelectric conversion device, the optical path length is extended, the light confinement effect is exhibited, and the short-circuit current density is increased. The characteristic of becomes higher.

  It is desirable that the pitch (L) of the unevenness in the direction parallel to one main surface of the substrate of the base layer is a length equal to or longer than the minimum wavelength of incident light.

  The unevenness pitch (L) is preferably greater than 100 nm and not greater than 10 μm, and more preferably greater than 300 nm and not greater than 2 μm.

  Further, it is preferable that the base layer has an aspect ratio which is a ratio (D / L) between the height difference D of unevenness in a direction perpendicular to one principal surface of the substrate and L is 1 or more.

  The underlayer can be formed of silicon oxide. Since the heat resistance of silicon oxide is sufficiently high, a process such as plasma CVD at 300 ° C. or higher can be performed after the base layer is formed. Moreover, since the transmittance | permeability of a silicon oxide is high, it can form in the light-incidence side from a photoelectric conversion unit.

  Specifically, the thin film photoelectric conversion device of the present invention includes a light-transmitting underlayer, a light-transmitting first electrode layer, and one or more photoelectric elements having fine periodic irregularities on one main surface of a light-transmitting insulating substrate. A structure in which a semiconductor layer including a conversion unit and a second electrode layer are sequentially arranged and light is incident through the substrate can be obtained.

  Alternatively, in the thin film photoelectric conversion device of the present invention, an underlying layer, a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, and a translucent second electrode layer are sequentially disposed on one main surface of the substrate, A structure in which light is transmitted through the translucent second electrode layer can be taken. In this case, the substrate, the base layer, and the first electrode layer may be opaque.

  The thin film photoelectric conversion device of the present invention can be manufactured by using the nanoimprint method in the step of producing the base layer.

  Specifically, as a process for preparing the underlayer of the thin film photoelectric conversion device of the present invention, a mixed liquid containing hydrogen silsesquioxane resin (HSQ) is applied onto the substrate, and a mold having fine periodic irregularities. Can be manufactured by embossing at room temperature and releasing the mold, followed by heating and / or hydrolysis.

  Alternatively, as a process for producing the underlayer of the thin film photoelectric conversion device of the present invention, a sol-gel material containing alkoxysilane is applied on the substrate, and then heated at a first temperature to have a fine periodic unevenness Can be manufactured by releasing the mold after embossing and heating at a second temperature higher than the first temperature.

  In the present invention, the term “low pressure thermal CVD method” refers to a thermochemical vapor deposition method using a gas having a pressure lower than atmospheric pressure. Low pressure thermal CVD is also called low pressure CVD or low pressure CVD (abbreviation LP-CVD), and is defined as thermochemical vapor deposition using a gas lower than atmospheric pressure. The Usually, the term “CVD” refers to “thermal CVD” except when an energy source is clearly indicated, such as “plasma CVD”, “photo CVD”, etc. It is synonymous with “thermal CVD method”. In addition, the low pressure thermal CVD method includes an organometallic CVD method (abbreviation, MO-CVD method) under reduced pressure.

  The term “nanoimprint” refers to a processing technique in which a mold having fine irregularities with a size of 0.1 nm to 100 μm is pressed against a material to be processed for transfer / molding. The “nanoimprint material” refers to a material to be processed onto which the unevenness of the mold is transferred by nanoimprint.

  According to the present invention, a thin film photoelectric conversion device including a structure in which a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, and a second electrode layer are sequentially arranged from the side closer to the substrate, And an underlying layer between the first electrode and the first layer, and the underlying layer has fine periodic irregularities in a direction parallel to one main surface of the substrate, so that the irregular layer is soiled or damaged in long-term outdoor use. There is no problem, and a thin film photoelectric conversion device with high reliability and characteristics can be provided by improving the light confinement effect.

  Further, by forming a base layer having fine periodic unevenness with silicon oxide, a process such as plasma CVD at 300 ° C. or higher can be performed after the base layer is formed. Moreover, since the transmittance | permeability of a silicon oxide is high, a base layer can be formed in the light-incidence side from a photoelectric conversion unit.

  In addition, according to the present invention, by using the nanoimprint method, an underlayer having fine periodic irregularities can be manufactured with high accuracy and reproducibility.

It is sectional drawing of the thin film photoelectric conversion apparatus of one Embodiment of this invention. It is a manufacturing method of the base layer of the fine periodic unevenness | corrugation by this invention. It is the transmission spectrum of the translucent insulating substrate of Example 1 by this invention and a translucent base layer, and the transmission spectrum of the translucent insulating substrate of the comparative example 1 by a conventional method. It is a spectral sensitivity spectrum of Example 1 by this invention and Comparative Examples 1 and 2 by a conventional method. It is sectional drawing of the thin film photoelectric conversion apparatus of the comparative example 1 by a conventional method. It is sectional drawing of the thin film photoelectric conversion apparatus of the comparative example 2 by a conventional method. It is sectional drawing of the thin film photoelectric conversion apparatus of Example 11 of this invention. It is the spectral sensitivity spectrum of Example 1 by this invention, and the comparative example 3 by a conventional method. It is a SEM image of the translucent base layer of Example 4 by this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In each drawing of the present application, dimensional relationships such as thickness and length are appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships. Moreover, in each figure, the same referential mark represents the same part or an equivalent part.

  In a thin film photoelectric conversion device, the reduction of the reflectance by the non-reflective layer and the light confinement effect by the light scattering by the fine uneven structure are important for increasing the short-circuit current density (Jsc) and improving the conversion efficiency. However, as described in the problem, when unevenness is formed on the transparent electrode layer by film forming conditions or etching, there are problems that the size of the unevenness varies, it is difficult to control the reproducibility of the unevenness, and light confinement is not sufficient.

  On the other hand, nanoimprinting can be used as a method for forming irregularities with high reproducibility and accuracy, but as an optical application, an uneven film having a pitch sufficiently smaller than the wavelength of light on the light receiving surface side of an optical element, so-called MOS A method for forming an antireflection layer by forming an eye structure is known. However, in thin-film photoelectric conversion devices that are premised on long-term outdoor use, especially thin-film solar cells, the fine uneven structure on the light-receiving surface side is likely to be contaminated and damaged, making it impossible to exhibit an anti-reflection effect. There is a problem that the reliability of the thin film photoelectric conversion device is low.

  In general, a nanoimprint material has a low glass transition temperature (for example, the glass transition temperature of polymethyl methacrylate is 105 ° C.), and it is difficult to perform a process at 200 ° C. or higher after forming irregularities by nanoimprint. For this reason, as far as the inventors know, there are few examples in which irregularities are formed by nanoimprint inside the device of the thin film photoelectric conversion device (other than the outermost surface of the device). Although the example which used the transparent electrode of the sol-gel material for the nanoimprint material was reported to the prior example 1, since the transparent electrode of a sol-gel material has a high resistivity and a low transmittance, the transparent electrode of the thin film photoelectric conversion device It is hard to say that it is suitable as a material.

  In view of the above-mentioned problems, the inventors diligently studied a device structure and a manufacturing method for forming a highly reliable unevenness effective for light confinement with high accuracy and good reproducibility.

  As a result, a thin film photoelectric conversion device including a structure in which a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, and a second electrode layer are sequentially arranged from the side closer to the substrate, The present invention has been completed by including a base layer between the electrodes, and the base layer having fine periodic irregularities in a direction parallel to one main surface of the substrate.

  At that time, it was surprisingly found that the pitch (L) of the unevenness in the direction parallel to one main surface of the substrate of the underlayer is preferably longer than the minimum wavelength of incident light. A moth-eye structure formed by a nanoimprint method is well known as an antireflection layer on the light receiving surface. In this case, it is important that L is sufficiently smaller than the wavelength of incident light. However, in the present invention, rather, the characteristics of the thin film photoelectric conversion device are improved when L is longer than the incident light. This is considered to be due to the fact that by making L longer than the wavelength, light scattering is strongly reflected at the interface having the periodic concavo-convex structure to exhibit a high light confinement effect.

  In the case of a periodic uneven structure, it is usually considered that a strong scattering effect appears only at a specific wavelength. Therefore, it is usually considered that the so-called random unevenness having various sizes and pitches exhibits a scattering effect in a wider wavelength range than the periodic unevenness. However, surprisingly, according to the configuration of the present invention, it has been found that the scattering effect can be obtained in a wide wavelength range despite having the periodic uneven structure. For example, it can be seen from the spectral sensitivity spectrum shown in FIG. 4 that the light scattering effect is obtained in the present invention in a wide wavelength range of 500 to 1000 nm.

  FIG. 1 is a cross-sectional view of a thin film photoelectric conversion device according to an example of an embodiment of the present invention. In order from the side closer to the incident light 7, the transparent insulating substrate 1, the transparent base layer 2 having fine periodic irregularities, the transparent first electrode layer 3, the crystalline photoelectric conversion unit 4, and the second electrode layer 5 are arranged sequentially.

  A plate-like member or sheet-like member made of glass, transparent resin or the like is mainly used for the translucent insulating substrate 1. In particular, when a glass substrate is mainly used as the light-transmitting insulating substrate 1, it is desirable as the light-transmitting insulating substrate 1 because of its high transmittance and low cost.

  Since the transparent insulating substrate 1 is located on the light incident side when the thin film photoelectric conversion device 5 is configured, in order to transmit more sunlight and absorb it in the amorphous or crystalline photoelectric conversion unit, as much as possible It is preferably transparent, and a glass plate is suitable as the material. For the same purpose, it is desirable to apply a non-reflective coating to the light incident surface of the translucent insulating substrate 1 so as to reduce the light reflection loss on the light incident surface of sunlight.

  A translucent underlayer 2 having fine periodic irregularities is formed on the translucent insulating substrate 1. The light-transmitting underlayer is preferably produced by forming irregularities on silicon oxide by a nanoimprint method. Since silicon oxide has high heat resistance, a process such as plasma CVD or sputtering that reaches 150 to 300 ° C. can be performed after the base layer is formed. Further, since silicon oxide has high transmittance, it can be disposed as a base layer on the light incident side of the photoelectric conversion unit.

  The translucent underlayer 2 can be formed by, for example, a so-called room temperature imprinting method in a process as shown in FIG. 2 using hydrogen silsesquioxane resin (HSQ) as a nanoimprint material. In FIG. 2A, first, the translucent insulating substrate 1 is cleaned in the cleaning tank 801. At this time, it is desirable that the cleaning liquid 802 be ultrasonically cleaned by sequentially using an alkaline detergent and pure water.

Next, as illustrated in FIG. 2B, a mixed liquid 201 containing hydrogen silsesquioxane is applied onto a light-transmitting insulating substrate to form a coating film 202. Examples of the coating method include a dipping method, a spin coating method, a bar coating method, a spray method, a die coating method, a roll coating method, a flow coating method, and the like. A spin coating method is preferable for uniformly forming a coating film. Used for. HSQ is a resin having a repeating structure of HSiO _3/2 . HSQ is roughly classified into a cage structure and a ladder structure, but it is desirable to include the ladder-shaped HSQ in the mixed solution 201 in order to increase heat resistance. The mixed solution 201 preferably contains alcohol, ester, ketone, or a mixture thereof as an organic solvent in addition to HSQ.

  Next, as shown in FIG. 2C, a mold 805, which is a mold having fine periodic irregularities, is pressed onto the coating film 202 using a nanoimprint apparatus including a stage 803 and a press plate 804. The embossing can be performed at room temperature at a pressure of 5 to 100 MPa. The mold 805 is preferably preliminarily coated with a release material made of a fluorine resin on the surface. Thereafter, as shown in FIG. 2D, the mold 805 is released from the coating film 202 while keeping the room temperature.

  Next, as shown in FIG. 2E, the uneven coating film 202 is cured by heating in an oven 806. Heating may be performed at a temperature of 200 to 500 ° C. for 1 minute to 12 hours. Thus, as shown in FIG. 2F, the underlayer 2 made of silicon oxide and having fine periodic irregularities is produced.

The translucent underlayer 2 can also be formed by a so-called thermal nanoimprint method in which embossing and heat curing are performed using a sol-gel material containing alkoxysilane as a nanoimprint material. First, the transparent insulating substrate 1 is cleaned and dried as in FIG. Next, a sol-gel material containing alkoxysilane is applied in the same manner as in FIG. Examples of the alkoxysilane include tetraethoxysilane (TEOS), tetramethoxysilane, tetrapropoxysilane, and alkylalkoxysilane. Further, as alkoxysilanes, condensate ethylsilicate 40 (polyethoxysilane, containing SiO _{2 in an amount} of 40% by weight and averaging TEOS pentamer condensate) and methylsilicate 51 (polymethoxysilane, SiO ₂ being SiO ₂ A tetramer silane tetramer condensate containing 51% by weight on average can also be used. For example, tetraethoxysilane is added to a mixed solution of water and ethyl cellosolve, hydrochloric acid is further added to hydrolyze tetraethoxysilane, and diacetone alcohol and propylene glycol are added as a diluting solution, and a coating solution for a sol-gel material. It can be. After this coating liquid is applied to the translucent insulating substrate 1, it can be semi-cured by heating at a first temperature of 20 ° C. to 150 ° C., preferably 60 ° C. to 90 ° C. for 5 minutes to 60 minutes. Next, the mold may be pressed into the coating solution on the transparent insulating substrate, heated to a second temperature higher than the first temperature at 20 to 500 ° C., and held for 5 to 60 minutes. After the coating solution is solidified, the mold is released. In this way, the underlayer 2 having fine periodic irregularities made of silicon oxide can be produced.

  It is desirable that the uneven pitch (L) in the direction parallel to the one main surface of the substrate of the underlayer 2 is a length equal to or longer than the minimum wavelength of incident light. Thereby, when L is more than the minimum wavelength of incident light, light scattering becomes strong and the light confinement effect can be enhanced. When light is incident on the photoelectric conversion unit through the glass substrate and the transparent electrode layer, only light having a wavelength longer than 300 nm can be substantially used due to absorption of the glass substrate and the transparent electrode layer.

  L is preferably greater than 100 nm and not greater than 10 μm, and more preferably greater than 300 nm and not greater than 2 μm. When L is larger than 100 nm, a scattering effect is recognized, and when L is larger than 300 nm, the scattering effect is further increased because it is larger than the incident wavelength to the photoelectric conversion unit. In addition, when L is small, it is difficult to produce a mold, and when forming irregularities by nanoimprinting, it becomes difficult for the nanoimprint material to enter the concave portions of the mold, and the irregularities are liable to sag. Therefore, L is preferably larger than 100 nm. , Larger than 300 nm, more preferably 500 nm or more. If L is too wide, it becomes difficult to increase the unevenness of the unevenness, particularly the aspect ratio, by nanoimprinting. Therefore, L is preferably 10 μm or less, and more preferably 2 μm or less.

  It is preferable that the underlayer has an aspect ratio which is a ratio (D / L) of 1 or more of the height difference D of the unevenness in the direction perpendicular to one main surface of the substrate and the L. This is because the light scattering effect becomes more remarkable by setting the aspect ratio to 1 or more.

The material of the light transmissive first electrode layer 3 may for example SnO _2, ITO, ZnO is used. In particular, ZnO is preferable because it can be manufactured at low cost using a sputtering method or low-pressure thermal CVD method at a low temperature of 300 ° C. or lower. In the case of forming a film by sputtering, it is desirable that the ZnO target contains 0.5 to 10% by weight, preferably 2 to 5% by weight, of any of B, Al and Ga impurities in order to lower the resistivity. .

When depositing ZnO by low-pressure thermal CVD, diethylzinc (DEZ) or dimethylzinc is used as the organometallic vapor, water is used as the oxidant vapor, diborane (B ₂ H ₆ ) is used as the boron-containing gas, and H is used as the dilution gas. ₂ , N ₂ , or any one or more of rare gases (He, Ar, Ne, Kr, Rn), and the mixed gas is introduced into a vacuum chamber maintained at a pressure of 5 to 200 Pa to produce ZnO. It is preferable to carry out the membrane. Specifically, DEZ flow rate 10 to 1000 sccm as organometallic vapor flow rate (FZ), boron-containing gas flow rate (FB) B ₂ H ₆ flow rate 0.01 to 100 sccm, water flow rate 10 to 1000 sccm, H A flow rate of ₂ to 100 sccm and an Ar flow rate of 100 to 10,000 sccm are preferable.

  The sheet resistance of ZnO is 15Ω / □ or less, preferably 10Ω / □ or less, in order to suppress resistance loss.

  The average thickness of the ZnO film is preferably 0.3 to 3 μm, and more preferably 0.5 to 2 μm. This is because if the ZnO film is too thin, it is difficult to obtain the necessary conductivity as a transparent conductive film, and if it is too thick, the light absorption by the ZnO film itself reduces the amount of light that passes through the ZnO and reaches the photoelectric conversion unit, thus lowering the efficiency. Because it does. Furthermore, when it is too thick, the film forming cost increases due to an increase in the film forming time.

  The crystalline silicon photoelectric conversion unit 4 is formed by stacking a p-type semiconductor layer, an i-type layer, and an n-type semiconductor layer in this order using, for example, a plasma CVD method. Specifically, p-type microcrystalline silicon layer 41 doped with 0.01 atomic% or more of boron, substantially i-type crystalline silicon photoelectric conversion layer 42, and 0.01 atomic% or more of phosphorus are doped. An n-type microcrystalline silicon layer 43 is deposited in this order.

The second electrode layer 5 includes at least one metal layer made of at least one material selected from aluminum (Al), silver (Ag), gold (Au), copper (Cu), platinum (Pt), and chromium (Cr). The layer is preferably formed by sputtering or vapor deposition. Between the photoelectric conversion unit and the metal layer, ITO, may be formed a layer made of SnO _2, conductive oxides such as ZnO (not shown).

  Furthermore, a protective film can be adhered by lamination using ethylene vinyl acetate resin (EVA) as an adhesive layer on the second electrode layer (not shown).

  Although FIG. 1 shows a single-junction thin-film photoelectric conversion device using a crystalline silicon photoelectric conversion layer as a photoelectric conversion unit, it goes without saying that a photoelectric conversion unit using other materials may be used. For example, a photoelectric conversion unit using amorphous silicon, amorphous silicon germanium, amorphous germanium, crystalline silicon germanium, or crystalline germanium can be used for the photoelectric conversion layer having a pin junction. Alternatively, a CdS / CdTe laminated film or a CIS / CdS laminated film having a pn junction can be used for the photoelectric conversion unit.

  Although FIG. 1 shows a single junction thin film photoelectric conversion device, it goes without saying that a thin film photoelectric conversion device in which two or more junction or more photoelectric conversion units are stacked may be used. For example, a so-called hybrid photoelectric conversion device in which amorphous silicon photoelectric conversion units / crystalline silicon photoelectric conversion units are stacked can also be configured.

  Although FIG. 1 shows a thin film photoelectric conversion device in which light is incident from the substrate side, the present invention is also effective in a thin film photoelectric conversion device in which light is incident from the side opposite to the substrate. In that case, as shown in FIG. 7, the thin film photoelectric conversion device includes a base layer 21, a first electrode layer 31, a semiconductor layer 4 including one or more photoelectric conversion units, a light-transmitting property, on one main surface of the substrate 11. A structure in which the second electrode layers 51 are sequentially disposed and the light 7 is incident through the light-transmissive second electrode layer 51 can be obtained. In this case, the substrate 11, the base layer 21, and the first electrode layer 31 may be opaque. The photoelectric conversion unit 4 is desirably laminated in the order of an n-type microcrystalline silicon layer 43, a substantially i-type crystalline silicon photoelectric conversion layer 42, and a p-type microcrystalline silicon layer 41. This is because the hole diffusion distance is shorter than that of electrons, so that the characteristics of the thin film photoelectric conversion device are enhanced when the p-type layer is disposed on the light incident side.

  Hereinafter, examples according to the present invention and comparative examples according to the prior art will be described in detail. In the drawings, the same members are denoted by the same reference numerals, and redundant description is omitted. Moreover, this invention is not limited to a following example, unless the meaning is exceeded. The embodiment is one of the preferred embodiments.

Example 1
As Example 1 of the present invention, a thin film photoelectric conversion device 9 having the structure shown in FIG. 1 was produced. As the translucent insulating substrate 1, a glass substrate having a thickness of 1 mm and 50 mm × 50 mm was used.

  The translucent underlayer 2 was produced by the process shown in FIG. The substrate was ultrasonically washed successively with an alkaline detergent and pure water for 5 minutes, and then dried at 80 ° C. for 30 minutes. A coating film 202 having a thickness of 500 nm was formed on the translucent insulating substrate 1 by spin coating using a mixed solution 201 containing about 20% by weight of HSQ and using propylene glycol dimethyl ether as an organic solvent.

  A cylindrical silicon mold 805 having a height of 320 nm and a pitch of 320 nm was used. The mold 805 was previously coated with OPTOOL DSX manufactured by Daikin Industries, Ltd. as a release material. Using a nanoimprint apparatus comprising a stage 803 and a press plate 804, this mold was embossed at room temperature at a pressure of 10 MPa for 1 minute in the coating liquid 202 on the light-transmitting insulating substrate 1. Thereafter, the mold was released and heated in an oven 806 at 300 ° C. for 30 minutes to form a translucent underlayer 2. When this translucent underlayer 2 was observed with an SEM, cylindrical holes were observed, and the pitch (L) was 320 nm and the depth (D) was 200 nm in a direction parallel to the surface of the translucent insulating substrate 1. The aspect ratio (D / L) was 0.625.

  The transmission spectrum of the light-transmitting insulating substrate with the light-transmitting underlayer 2 is shown in Example 1 in FIG. Light was incident from the side where the transparent base layer 2 was not attached, and the transmission spectrum was measured. For the transmission spectrum, a self-recording spectrophotometer UV3100 manufactured by Shimadzu Corporation was used. An integrating sphere was used for the detector. For reference, a transmission spectrum of only a glass substrate without the translucent underlayer 2 is shown as Comparative Example 1. The transmission spectrum of Example 1 has a transmittance lower than the transmission spectrum of the glass substrate of Comparative Example 1 only in the wavelength range of about 370 nm to 800 nm. From this, it can be seen that the translucent underlayer 2 does not function as a non-reflective layer. Moreover, the region where the transmission spectrum of Example 1 is low shows a substantially constant transmittance, and shows a unique spectrum different from the interference of a normal thin film. This is presumably because the amount of transmitted light detected was reduced despite the fact that light was strongly scattered by the light-transmitting underlayer 2 and an integrating sphere was used for the detection unit.

About 700 nm of ZnO was formed on the light-transmitting underlayer 2 as the light-transmitting first electrode layer 3 by sputtering using a DC power source. A ZnO target containing 3% by weight of Al ₂ O ₃ was used as the target. The sheet resistance of the produced ZnO film was 5Ω / □.

  Furthermore, the crystalline silicon photoelectric conversion unit 4 was produced using the plasma CVD method. A crystal composed of a p-type microcrystalline silicon layer 41 having a thickness of 15 nm, a crystalline silicon photoelectric conversion layer 42 of substantially intrinsic crystalline silicon having a thickness of 1.7 μm, and an n-type microcrystalline silicon layer 43 having a thickness of 15 nm. Quality silicon photoelectric conversion layer units were sequentially formed by plasma CVD.

Next, a conductive oxide layer of ZnO doped with 3 wt% Al ₂ O ₃ with a thickness of 90 nm and an Ag metal layer with a thickness of 200 nm were used as the second electrode layer 5, and a mask with an opening of 1 cm ² was used. They were sequentially formed by sputtering. Then, after attaching a lead wire with ultrasonic soldering, the protective film was adhered using EVA as an adhesive layer.

The thin film photoelectric conversion device of Example 1 thus obtained was irradiated with AM 1.5 light at a light amount of 100 mW / cm ² and the output characteristics were measured. The open circuit voltage (Voc) was 0.517 V and the short-circuit current was measured. The density (Jsc) was 21.82 mA / cm ² , the fill factor (FF) was 0.633, and the conversion efficiency (Eff) was 7.14%.

  Moreover, the spectral sensitivity of the thin film photoelectric conversion apparatus of Example 1 is shown in FIG.

  Moreover, when the characteristics were measured after Example 1 was exposed outdoors for 60 days, the retention rate of Eff was 99%.

(Comparative Example 1)
As Comparative Example 1 by a conventional method, a thin film photoelectric conversion device 91 having a structure shown in FIG. 5 was produced. The structure and the manufacturing method of Comparative Example 1 were the same as those of Example 1 except that there was no translucent underlayer 2. A transmission spectrum of only the translucent insulating substrate 1 of Comparative Example 1 is shown in FIG.

When the output characteristics of the obtained thin film photoelectric conversion device of Comparative Example 1 were measured in the same manner as in Example 1, Voc = 0.519 V, Jsc = 20.14 mA / cm ² , FF = 0.635, and Eff = 6. It was 64%. In Comparative Example 1, Jsc is lower and Eff is lower than that in Example 1. This is probably because the light confinement effect is hardly obtained in Comparative Example 1.

  FIG. 4 shows the spectral sensitivity of Comparative Example 1. Although the transmittance | permeability of the glass substrate with the translucent base layer 2 of Example 1 in FIG. 3 is lower in the wavelength range of 370 nm to 800 nm than the transmittance | permeability of only a glass substrate, of Example 1 The spectral sensitivity is higher than that of Comparative Example 1 over a wide wavelength range from 500 nm to 1000 nm. From this, it can be said that strong scattering occurs by the translucent underlayer 2, and effective light confinement is realized in the thin film photoelectric conversion device of Example 1, and Jsc and Eff are increased.

  Moreover, when the characteristics of the Comparative Example 1 were measured after 60 days of outdoor exposure, the retention rate of Eff was 98%.

(Comparative Example 2)
As Comparative Example 2 by the conventional method, a thin film photoelectric conversion device 92 having a structure shown in FIG. 6 was produced. The comparative example 2 has the same structure and production method except that the concavo-convex layer 6 was produced on the light receiving surface side in the same manner as the translucent underlayer 2 of Example 1 instead of having no translucent underlayer 2. Same as Example 1.

When the output characteristics of the obtained thin film photoelectric conversion device of Comparative Example 2 were measured in the same manner as in Example 1, Voc = 0.516 V, Jsc = 20.94 mA / cm ² , FF = 0.631, and Eff = 6. 82%. The spectral sensitivity of Comparative Example 2 is shown in FIG.

  In Comparative Example 2, Jsc increased compared to Comparative Example 1, but Jsc was lower and Eff was lower than Example 1. Judging from the transmission spectrum of Example 1 in FIG. 3, the uneven layer 6 can be said to have no effect of the non-reflective layer. Although it is considered that the Jsc slightly increased as compared with Comparative Example 1, the light scattering effect is considered. However, since the uneven layer 6 is on the light receiving surface side, the scattered light is photoelectrically equivalent to the thickness of the translucent insulating substrate 1. It is considered that the Jsc is lower than that of Example 1 because it is difficult to enter the conversion unit 4.

  Moreover, when the comparative example 2 was exposed outdoors for 60 days and then the characteristics were measured, the retention rate of Eff was 87%. This can be said that the uneven layer 6 on the light-receiving surface is soiled by exposure to the outside, and the fine unevenness is damaged, and thus the transmittance and the scattering effect are reduced, and the characteristics are deteriorated.

(Comparative Example 3)
As Comparative Example 3 by a conventional method, a thin film photoelectric conversion device similar to Comparative Example 1 was produced. In Comparative Example 3, the transparent base layer 2 having periodic unevenness was used, and a commercially available product in which tin oxide having random unevenness was attached to the glass substrate as the transparent first electrode layer 3 was used as Comparative Example 1 Different. In other respects, the structure and manufacturing method of the thin film photoelectric conversion device were the same as those in Comparative Example 1.

When the output characteristics of the obtained thin film photoelectric conversion device of Comparative Example 3 were measured in the same manner as in Example 1, Voc = 0.512 V, Jsc = 21.35 mA / cm ² , FF = 0.630, and Eff = 6. It was 89%. The spectral sensitivity of Comparative Example 3 is shown in FIG.

  In Comparative Example 3, Jsc increased compared to Comparative Example 2, but Jsc was lower and Eff was lower than Example 1. Comparative Example 3 has a light scattering effect to some extent due to the random unevenness of the translucent first electrode layer 3, and Jsc is higher than Comparative Examples 1 and 2. However, Jsc of Example 1 is higher and the period is higher. It can be said that the light scattering effect is higher in Example 1 having an internal uneven structure on the inner surface.

  From FIG. 8, the spectral sensitivity of Example 1 is higher than that of Comparative Example 3 over a wide wavelength range of 700 to 1000 nm. Usually, in order to obtain a light scattering effect in a wide wavelength range, unevenness of various sizes is essential, and it is generally considered that a random uneven structure is necessary. Conversely, in the case of a periodic uneven structure, it is generally considered that only a specific wavelength has a light scattering effect. However, as is apparent from FIG. 8, the thin film photoelectric conversion device having a periodic uneven structure according to the present invention does not have a light scattering effect only at a specific wavelength. I understand that there is.

  Note that the spectral sensitivity of Comparative Example 3 is higher than that of Example 1 at 300 to 400 nm because the absorption coefficient of tin oxide, which is the transparent electrode layer material of Comparative Example 3, is lower than that of the transparent electrode layer material ZnO of Example 1. Thus, it is unrelated to the light scattering effect of the present invention.

(Example 2)
As Example 2 of the present invention, a thin film photoelectric conversion device 9 having the structure shown in FIG. 1 was produced. In Example 2, the structure and the production method were the same as those in Example 1, except that the pressing pressure when producing the translucent underlayer 2 by nanoimprinting was 20 MPa.

  When the light-transmitting underlayer 2 of Example 2 was observed by SEM, cylindrical holes were observed, and L = 320 nm, D = 320 nm, and aspect ratio D / L = 1.0.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 2 were measured in the same manner as in Example 1, Voc = 0.520V, Jsc = 22.43 mA / cm ² , FF = 0.632, and Eff = 7. 37%. In the second embodiment, the aspect ratio of the light-transmitting underlayer 2 is increased to 1, the Jsc is increased, and the Eff is improved as compared with the first embodiment.

(Example 3)
As Example 3 of the present invention, a thin film photoelectric conversion device 9 having the structure shown in FIG. 1 was produced. In Example 3, the structure and the manufacturing method were the same as those in Example 2 except that a cylindrical mold having a height of 500 nm and a pitch of 500 nm was used for forming the light-transmitting underlayer 2. .

  When the light-transmitting underlayer 2 of Example 3 was observed by SEM, cylindrical holes were observed, and L = 500 nm, D = 500 nm, and aspect ratio D / L = 1.0.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 3 were measured in the same manner as in Example 1, Voc = 0.518 V, Jsc = 23.35 mA / cm ² , FF = 0.627, and Eff = 7. 58%. In Example 3, Jsc further increased and Eff improved compared to Example 2.

Example 4
As Example 4 of this invention, the thin film photoelectric conversion apparatus 9 of the structure shown in FIG. 1 was produced. In Example 4, the thickness of the coating film 202 when forming the light-transmitting underlayer 2 was set to 1000 nm, and the mold was used in a cylindrical shape with a height of 1000 nm and a pitch of 1000 nm. The structure and manufacturing method were the same as in Example 2.

  When the light-transmitting underlayer 2 of Example 4 was observed by SEM, cylindrical holes were observed, L = 1000 nm, D = 950 nm, and aspect ratio D / L = 0.95. FIG. 9 shows an SEM image.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 4 were measured in the same manner as in Example 1, Voc = 0.517V, Jsc = 2.48 mA / cm ² , FF = 0.625, and Eff = 7. 26%.

(Example 5)
As Example 5 of the present invention, a thin film photoelectric conversion device 9 having the structure shown in FIG. 1 was produced. In Example 5, the thickness of the coating film 202 when forming the translucent underlayer 2 was set to 2000 nm, and a mold having a cylindrical shape with a height of 2000 nm and a pitch of 2000 nm was used. The structure and manufacturing method were the same as in Example 2.

  When the light-transmitting underlayer 2 of Example 5 was observed by SEM, cylindrical holes were observed, and L = 2000 nm, D = 1800 nm, and aspect ratio D / L = 0.90.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 5 were measured in the same manner as in Example 1, Voc = 0.516 V, Jsc = 22.25 mA / cm ² , FF = 0.620, and Eff = 7. 09%.

(Example 6)
As Example 6 of this invention, the thin film photoelectric conversion apparatus 9 of the structure shown in FIG. 1 was produced. In Example 6, except that the thickness of the coating film 202 when forming the translucent underlayer 2 was 10000 nm, and a mold having a cylindrical shape with a height of 9500 nm and a pitch of 9500 nm was used. The structure and manufacturing method were the same as in Example 2.

  When the light-transmitting underlayer 2 of Example 6 was observed by SEM, cylindrical holes were observed, L = 9500 nm, D = 8000 nm, and aspect ratio D / L = 0.842.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 6 were measured in the same manner as in Example 1, Voc = 0.518 V, Jsc = 21.76 mA / cm ² , FF = 0.618, and Eff = 6. 97%.

(Example 7)
As Example 7 of the present invention, a thin film photoelectric conversion device 9 having the structure shown in FIG. 1 was produced. In Example 7, the thickness of the coating film 202 when forming the translucent underlayer 2 was set to 200 nm, and a mold having a cylindrical shape with a height of 120 nm and a pitch of 120 nm was used. The structure and manufacturing method were the same as in Example 2.

  When the light-transmitting underlayer 2 of Example 7 was observed by SEM, cylindrical holes were observed, and L = 120 nm, D = 120 nm, and the aspect ratio D / L = 1.0.

When the output characteristics of the thin film photoelectric conversion device of Example 7 obtained were measured in the same manner as in Example 1, Voc = 0.517V, Jsc = 21.41 mA / cm ² , FF = 0.634, and Eff = 7. 02%.

(Example 8)
As Example 8 of the present invention, a thin film photoelectric conversion device 9 having the structure shown in FIG. 1 was produced. In Example 8, the structure and the production method were the same as those in Example 3 except that the pressing pressure when producing the translucent underlayer 2 by nanoimprinting was 7 MPa.

  When the light-transmitting underlayer 2 of Example 8 was observed by SEM, cylindrical holes were observed, and L = 500 nm, D = 250 nm, and aspect ratio D / L = 0.5.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 8 were measured in the same manner as in Example 1, Voc = 0.517V, Jsc = 21.55 mA / cm ² , FF = 0.630, and Eff = 7. 02%.

Example 9
As Example 9 of the present invention, a thin film photoelectric conversion device 9 having a structure shown in FIG. 1 was produced. In Example 9, except that the thickness of the coating film 202 when forming the translucent underlayer 2 was 1000 nm, and a mold having a cylindrical shape with a height of 1000 nm and a pitch of 500 nm was used. The structure and manufacturing method were the same as in Example 2.

  When the light-transmitting underlayer 2 of Example 9 was observed by SEM, cylindrical holes were observed, and L = 500 nm, D = 1000 nm, and aspect ratio D / L = 2.0.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 9 were measured in the same manner as in Example 1, Voc = 0.516 V, Jsc = 24.35 mA / cm ² , FF = 0.627, and Eff = 7. It was 88%.

(Example 10)
As Example 10 of this invention, the thin film photoelectric conversion apparatus 9 of the structure shown in FIG. 1 was produced. In Example 10, except that the thickness of the coating film 202 when forming the light-transmitting underlayer 2 was 2000 nm, and a mold having a cylindrical shape with a height of 2000 nm and a pitch of 500 nm was used. The structure and manufacturing method were the same as in Example 2.

  When the light-transmitting underlayer 2 of Example 10 was observed with an SEM, cylindrical holes were observed, L = 500 nm, D = 2000 nm, and aspect ratio D / L = 4.0.

When the output characteristics of the obtained thin film photoelectric conversion device of Example 10 were measured in the same manner as in Example 1, Voc = 0.515 V, Jsc = 2.17 mA / cm ² , FF = 0.619, and Eff = 8. 02%.

(Example 11)
As Example 11 of the present invention, a thin film photoelectric conversion device 93 having a structure shown in FIG. 7 was produced. As the substrate 11, a stainless steel substrate (SUS304) having a thickness of 1 mm and 50 mm × 50 mm was used. The underlayer 21 was produced in the same manner as in Example 3. When the underlayer 21 of Example 11 was observed by SEM, cylindrical holes were observed, and L = 500 nm, D = 500 nm, and the aspect ratio D / L = 1.0.

Further, a ZnO conductive oxide layer doped with 3 wt% Al ₂ O ₃ with a thickness of 90 nm and an Ag metal layer with a thickness of 200 nm are formed as a first electrode layer 31 by sputtering. A conductive oxide layer of ZnO doped with 3 wt% Al ₂ O ₃ having a thickness of 90 nm was sequentially formed by sputtering. A crystalline photoelectric conversion unit 4 was produced in the same manner as in Example 1 except that the stacking order was an n-type layer, an i-type layer, and a p-type layer. Further, as the translucent second electrode layer 51, ITO having a thickness of 70 nm was formed by sputtering using a mask having an opening area of 1 cm ² .

When the output characteristics of the obtained thin film photoelectric conversion device of Example 11 were measured in the same manner as in Example 1, Voc = 0.520V, Jsc = 23.62 mA / cm ² , FF = 0.635, and Eff = 7. 80%.

(Comparative Example 4)
As Comparative Example 4 by a conventional method, a thin film photoelectric conversion device was produced. In Comparative Example 4, the structure and the manufacturing method were the same as those in Example 11 except that the base layer 21 was not provided.

When the output characteristics of the obtained thin film photoelectric conversion device of Comparative Example 4 were measured in the same manner as in Example 1, Voc = 0.519 V, Jsc = 20.57 mA / cm ² , FF = 0.634, and Eff = 6. 77%.

(Examples 1-11, Comparative Examples 1-4)
Table 1 summarizes the outline and characteristics of the manufacturing methods of the thin film photoelectric conversion devices of Examples 1 to 11 and Comparative Examples 1 to 4.

DESCRIPTION OF SYMBOLS 1 Translucent insulating substrate 11 Substrate 2 Translucent foundation layer 21 Underlayer 201 Coating liquid 202 Coating film 3 Translucent first electrode layer 31 First electrode layer 4 Crystalline silicon photoelectric conversion unit 41 p-type microcrystalline silicon layer 42 substantially intrinsic crystalline silicon photoelectric conversion layer 43 n-type microcrystalline silicon layer 5 second electrode layer 51 translucent second electrode layer 6 uneven layer 7 incident light 801 cleaning tank 802 cleaning liquid 803 stage 804 press plate 805 mold 806 Oven 9 Thin Film Photoelectric Conversion Device According to the Present Invention 91 Thin Film Photoelectric Conversion Device According to Conventional Method 92 Thin Film Photoelectric Conversion Device According to Another Conventional Method 93 Thin Film Photoelectric Conversion Device According to Another Present Invention

Claims (11)

  A thin film photoelectric conversion device including a structure in which a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, and a second electrode layer are sequentially arranged from the side closer to the substrate, between the substrate and the first electrode A thin film photoelectric conversion device comprising: a base layer, wherein the base layer has fine periodic irregularities in a direction parallel to one main surface of the substrate.   2. The thin film photoelectric conversion device according to claim 1, wherein a pitch (L) of unevenness in a direction parallel to one main surface of the substrate of the base layer is a length equal to or longer than a minimum wavelength of incident light. A thin film photoelectric conversion device.   2. The thin-film photoelectric conversion device according to claim 1, wherein an unevenness pitch (L) in a direction parallel to one principal surface of the substrate of the base layer is greater than 100 nm and less than or equal to 10 μm, desirably greater than 300 nm and less than or equal to 2 μm. There is a thin film photoelectric conversion device.   2. The thin film photoelectric conversion device according to claim 1, wherein a pitch (L) of unevenness in a direction parallel to one main surface of the substrate of the base layer is greater than 300 nm and equal to or less than 2 μm. Conversion device.   5. The thin-film photoelectric conversion device according to claim 1, wherein the underlayer has a height difference D of unevenness in a direction perpendicular to one main surface of the substrate and a ratio of L (D / L). A thin film photoelectric conversion device having an aspect ratio of 1 or more.   6. The thin film photoelectric conversion device according to claim 1, wherein the underlayer is silicon oxide.   The thin-film photoelectric conversion device according to claim 1, wherein a light-transmitting underlayer, a light-transmitting first electrode layer, and one or more photoelectric conversions are provided on one main surface of the light-transmitting insulating substrate. A thin film photoelectric conversion device, wherein a semiconductor layer including a unit and a second electrode layer are sequentially arranged, and light is incident through the substrate.   7. The thin film photoelectric conversion device according to claim 1, wherein a base layer, a first electrode layer, a semiconductor layer including one or more photoelectric conversion units, a translucent layer on one main surface of the substrate. A thin film photoelectric conversion device, wherein two electrode layers are sequentially arranged, and light enters through a light-transmitting second electrode layer.   9. The method for manufacturing a thin film photoelectric conversion device according to claim 1, wherein the step of forming the underlayer uses a nanoimprint method.   10. The method of manufacturing a thin film photoelectric conversion device according to claim 9, wherein the step of forming the base layer is performed by applying a liquid mixture containing hydrogen silsesquioxane resin (HSQ) on the substrate, and performing a fine cycle. A thin-film photoelectric conversion device, wherein the underlayer is produced by pressing a mold having irregularities at room temperature, releasing the mold, and performing a curing process by heating and / or hydrolysis Manufacturing method.   10. The method for manufacturing a thin film photoelectric conversion device according to claim 9, wherein the step of producing the underlayer is performed by applying a sol-gel material containing alkoxysilane on the substrate, and then heating the substrate at a first temperature. A thin-film photoelectric converter characterized by producing a base layer by embossing a mold having periodic irregularities, heating the mold at a second temperature higher than the first temperature, and then releasing the mold. A method for manufacturing a conversion device.