JP2009071034A - Thin film photoelectric converion device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin film photoelectric conversion device which improves photoelectrically converting efficiency. <P>SOLUTION: The thin film photoelectric conversion device includes a transparent electrode layer, one or more photoelectric conversion units and a rear electrode layer which are successively disposed from a light incidence side. In the thin film photoelectric conversion device, the photoelectric conversion unit is one in which a p-type semiconductor layer, a photoelectric conversion layer of a substantially intrinsic semiconductor, and an n-type semiconductor layer are disposed in this order from a light incidence direction. The transparent electrode layer contains Zn, Mg, O and a doping impurity, and the transparent electrode layer contacts with the p-type semiconductor layer contained in one of the photoelectric conversion units at an interface. Thus, the problem is solved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thin film photoelectric conversion device and a method for manufacturing the same, and more particularly to improvement of the transparent electrode layer.

  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 interest in environmental problems 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.

  FIG. 1 is a conceptual cross-sectional view showing an example of a laminated structure of such a thin film photoelectric conversion device. In the drawings of the present application, dimensional relationships such as length, width, and thickness are appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships. In the drawings of the present application, the same reference numerals represent the same or corresponding parts.

In the manufacture of a thin film photoelectric conversion device as illustrated in FIG. 1, a glass substrate is generally used as the translucent insulating substrate 11. Alternatively, a glass substrate 111 and a light-transmitting base layer 112 that are stacked may be used as the light-transmitting insulating substrate. On the glass substrate, as the transparent electrode layer 12, for example, a SnO ₂ film having a thickness of 700 nm is formed by a thermal CVD (chemical vapor deposition) method. On the transparent electrode layer 12, a semiconductor layer 20 including one or more amorphous photoelectric conversion units and / or crystalline photoelectric conversion units is formed. Subsequently, the back electrode layer 4 is formed. Finally, the back side of the thin film photoelectric conversion device is protected by a sealing resin (not shown).

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

The transparent electrode layer 12 is made of a transparent conductive oxide (TCO) such as ITO (Indium Tin Oxide), SnO ₂ , or ZnO, and is generally formed by a method such as CVD, sputtering, or vapor deposition. The transparent electrode layer 12 preferably has an effect of increasing the scattering of incident light by having fine irregularities on its surface.

One photoelectric conversion unit includes a semiconductor layer including a pn junction or a pin junction. As the semiconductor layer, amorphous silicon, crystalline silicon, CuInSe ₂ (abbreviation CIS), CdTe, or the like can be used. In the specification of the present application, the terms “crystalline” and “microcrystalline” also mean a material partially including amorphous material.

  In the case of a silicon-based thin film photoelectric conversion device, the photoelectric conversion unit includes a pin junction formed by a p-type layer, a substantially intrinsic i-type photoelectric conversion layer, and an n-type layer. The unit including the amorphous silicon i-type photoelectric conversion layer is referred to as an amorphous silicon photoelectric conversion unit, and the unit including the crystalline silicon i-type photoelectric conversion layer is referred to as a crystalline silicon photoelectric conversion unit. The Note that as the amorphous or crystalline silicon-based material, not only a material containing only silicon as a main element but also an alloy material containing elements such as carbon, oxygen, nitrogen, and germanium can be used. Further, the conductive type layer is not necessarily formed of the same semiconductor material as the i-type layer. For example, when the i-type layer is amorphous silicon, amorphous silicon carbide can be used for the p-type layer, and a microcrystal-containing silicon layer (also referred to as a μc-Si layer) can be used for the n-type layer. it can.

As the back electrode layer 4 formed on the semiconductor layer 20, for example, a metal layer such as Al or Ag can be formed by sputtering or vapor deposition. Further, as shown in FIG. 1, even if a conductive oxide layer 41 such as ITO, SnO ₂ , or ZnO is formed between the semiconductor layer 20 and the metal layer 42 included in the back electrode layer 4. Good.

  In the amorphous silicon thin film photoelectric conversion device, the initial photoelectric conversion efficiency is lower than that of bulk single crystal and polycrystalline photoelectric conversion devices, and the conversion efficiency decreases due to the photodegradation phenomenon (Staebler-Wronsky effect). is there. Therefore, a crystalline silicon thin film photoelectric conversion device using a crystalline silicon thin film containing polycrystals or microcrystals as a photoelectric conversion layer is expected and studied as a photoelectric conversion device that can achieve both low cost and high efficiency. ing. This is because the crystalline silicon thin film photoelectric conversion device can be manufactured at a relatively low temperature by the plasma CVD method as in the case of the amorphous silicon thin film photoelectric conversion device, and hardly causes a photodegradation phenomenon. In addition, the amorphous silicon photoelectric conversion layer can photoelectrically convert light up to a wavelength of about 800 nm on the long wavelength side, whereas the crystalline silicon photoelectric conversion layer photoelectrically converts light up to a wavelength of about 1200 nm. Can be converted.

  Furthermore, as a method for improving the conversion efficiency of a thin film photoelectric conversion device, a stacked thin film photoelectric conversion device including two or more stacked photoelectric conversion units is known. In this stacked thin film photoelectric conversion device, a front unit including a photoelectric conversion layer having a large energy band gap is disposed on the light incident side, and a rear unit including a photoelectric conversion layer having a small band gap is sequentially disposed behind the front unit. . Thus, photoelectric conversion over a wide wavelength range of incident light is enabled, and the conversion efficiency of the entire laminated thin film photoelectric conversion device is improved. Among stacked thin film photoelectric conversion devices, a stack of an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit is referred to as a hybrid thin film photoelectric conversion device.

  By the way, the thin film photoelectric conversion device can make the photoelectric conversion layer thinner compared to the conventional photoelectric conversion device using bulk single crystal or polycrystalline silicon. There is a problem that is limited by. Therefore, in order to use light incident on the semiconductor layer more effectively, the surface of the transparent electrode layer or the back electrode layer in contact with the semiconductor layer is roughened (textured), and light is scattered at the interface to scatter the light inside the semiconductor layer. In order to extend the optical path length of the light-emitting layer, a device for increasing the amount of light absorbed in the photoelectric conversion layer has been devised. This technique is called “optical confinement”, and is an important elemental technique for putting a thin film photoelectric conversion device having high photoelectric conversion efficiency into practical use.

  In order to obtain the surface uneven shape of the transparent electrode layer optimal for the thin film photoelectric conversion device, an index that quantitatively represents the uneven shape is required. Haze rate and surface area ratio (Sdr) are known as indices representing such surface irregularities.

  The haze ratio is an index for optically evaluating the surface unevenness of the transparent substrate, and is expressed by (diffuse transmittance / total light transmittance) × 100 [%] (JIS K7136). Such a haze rate can be automatically measured by a commercially available haze meter. A C light source is generally used as a light source for the measurement.

  The surface area ratio is an index that represents not only the size of the surface unevenness but also the shape of the unevenness. If the surface irregularities of the transparent electrode layer are sharpened, the open-circuit voltage and the fill factor of the thin film photoelectric conversion device may decrease, so the surface area ratio is effective as an index of the surface irregularities of the transparent electrode layer in the thin film photoelectric conversion device. . The surface area ratio is also called a developed surface area ratio, and Sdr is used as an abbreviation.

A thin film photoelectric conversion device is formed on a transparent substrate such as glass, and a tin oxide (SnO ₂ ) film having surface irregularities is often used as a transparent electrode layer. The surface unevenness of the transparent electrode layer contributes to light confinement in the photoelectric conversion layer. Therefore, in order to enhance the light confinement effect, it is desirable to increase the surface unevenness. However, with the SnO ₂ film alone, it is possible to make the surface uneven shape remarkable while maintaining the translucency and conductivity required for the photoelectric conversion device. Not easy.

Further, a glass substrate having a SnO ₂ film formed by atmospheric pressure CVD as a transparent electrode layer having surface irregularities effective for light confinement has a relatively high temperature of about 550 to 650 ° C. in order to form the transparent electrode layer. Since a high temperature process is required, the manufacturing cost is increased. And since the CVD temperature is high, an inexpensive substrate such as normal glass or plastic film cannot be used. Also, if the tempered glass is subjected to a high temperature process, the tempering effect disappears, so the tempered glass cannot be used for the substrate, and in order to ensure the strength of the glass substrate in the large area photoelectric conversion device, it is necessary to increase its thickness, As a result, the photoelectric conversion device becomes heavy.

Furthermore, SnO ₂ film is plasma resistance is low, SnO ₂ film can be reduced in a deposition environment of the semiconductor layer utilizing high-density plasma containing hydrogen. When the SnO ₂ film is reduced, the SnO ₂ film is blackened and the transparency is lowered. That is, the blackened SnO ₂ electrode layer absorbs incident light, reduces the amount of light transmitted to the photoelectric conversion layer, and causes a decrease in conversion efficiency of the thin film photoelectric conversion device. In particular, when a hybrid thin film photoelectric conversion device is manufactured, a higher plasma density is required when depositing a crystalline silicon layer than when depositing an amorphous silicon layer, and a SnO ₂ film is used as a transparent electrode layer. However, it is difficult to greatly improve the conversion efficiency.

On the other hand, zinc oxide (ZnO) is less expensive than SnO ₂ or ITO widely used as a material for the transparent electrode layer, and has an advantage of high plasma resistance, and is transparent for thin film photoelectric conversion devices. It is suitable as an electrode material. In particular, a zinc oxide layer is a crystalline silicon thin film photoelectric conversion device or a hybrid thin film photoelectric conversion device including a crystalline silicon layer that requires a high-density plasma containing a large amount of hydrogen during deposition compared to an amorphous silicon layer. Preferred as a transparent electrode layer.

ZnO is a CIS photoelectric conversion device using CuInSe ₂ (abbreviation CIS) or Cu (In, Ga) Se 2 (abbreviation CIGS) for the light absorption layer. In addition to the transparent electrode layer, a high-resistance buffer layer or n-type is used. Used as a window layer. Specific laminated structure of CIS photoelectric conversion device is as follows: glass / Mo back electrode / CIS or CIGS p-type semiconductor light absorption layer / ZnO buffer layer / CdS n-type window layer / ITO transparent electrode layer / grid electrode The structure which laminated | stacked in order of these is mentioned. Alternatively, a structure of glass / Mo back electrode / CIS or CIGS p-type semiconductor light absorption layer / ZnO n-type window layer / ZnO transparent electrode layer / grid electrode may be mentioned.

  (Prior art example 1) For example, the formation method of the ZnO film disclosed in Patent Document 1 is disclosed that a thin film having unevenness can be formed at a low temperature by a low pressure thermal CVD method (also called MOCVD method) of 200 ° C. or lower is doing. Compared with atmospheric pressure thermal CVD, a low temperature process of 200 ° C. or lower can reduce the cost. In addition, an inexpensive base such as glass or plastic film after solidification can be used. Furthermore, since tempered glass can be used, the glass substrate of the large-area photoelectric conversion device can be reduced to about 2/3 and lighter. In addition, the low-pressure thermal CVD method is preferable for a thin film photoelectric conversion device in terms of manufacturing cost because it can be formed at a film forming speed one digit or more faster than the sputtering method and the utilization efficiency of raw materials is high. It is said.

(Prior Art 2) Patent Document 2 discloses that a CIS photoelectric conversion device includes a back electrode layer, a CIS or CIGS p-type semiconductor light absorption layer, and Zn _1-x Mg _x O (0 <x <1, abbreviated as ZMO). A structure in which an n-type window layer and a ZMO transparent electrode layer containing a doping impurity are sequentially laminated is disclosed. The transparent electrode layer is required to contain any of Al, Ga, and In as a doping element. The CIS photoelectric conversion device of Patent Document 2 uses a ZMO instead of the general ZnO for the window layer and the transparent electrode layer, thereby allowing the light absorption layer / window layer interface and the window layer / transparent electrode layer interface, respectively. The band discontinuity of the conduction band is reduced, and the characteristics of the photoelectric conversion device are improved. The preferred range of the Mg concentration x is 0.05 to 0.35, and the resistivity of the ZMO window layer is 1 × 10 ¹² Ω · cm or less, preferably 1 × 10 ¹¹ Ω · cm or less. The sheet resistance of the transparent electrode layer of ZMO in the example is 60Ω / □.
JP 2000-252501 A JP 2004-281938 A

The present inventor fabricated a thin film photoelectric conversion device using ZnO containing a doping impurity in the transparent electrode layer disclosed in the above-mentioned Patent Document 1, and examined its characteristics. As a result, the transparent electrode layer contained SnO containing a doping impurity. _As compared with the case of using ₂ , it was found that the collection efficiency of light having a short wavelength of 300 to 400 nm is lowered.

  In Patent Document 2 described above, the window layer of the CIS photoelectric conversion device uses a high-resistance ZMO that does not contain doping impurities, and the transparent electrode layer uses ZMO that contains doping impurities. Since the ZMO of the transparent electrode layer is in contact with the ZMO of the n-type window layer, there is a problem that not only a function as a transparent electrode but also a function as a strong n-type semiconductor is required. That is, since the characteristics of the photoelectric conversion device may be deteriorated due to the conduction band discontinuity at the interface between the window layer and the transparent electrode layer, the ZMO containing the doping impurity of the transparent electrode layer is banded by the ZMO containing no doping impurity of the window layer. There is a problem that the gap and Mg composition are limited and cannot be optimized independently. Similarly, since the window layer is limited by the p-type semiconductor light absorption layer, ZMO including doping impurities in the transparent electrode layer is also limited to the p-type semiconductor light absorption layer, and there is a problem that cannot be optimized independently. . For this reason, optimization of ZMO containing the doping impurity of a transparent electrode layer is restrict | limited, and the subject that the sheet resistance of a transparent electrode layer becomes high occurs.

  Furthermore, since the p-type semiconductor light absorption layer of Patent Document 2 is produced by vacuum deposition, the n-type window layer is produced by sputtering. Therefore, the junction interface between the p-type semiconductor and the semiconductor of the n-type window layer is used. Therefore, there is a problem that the characteristics of the photoelectric conversion device may be deteriorated due to oxidation or adhesion of impurities.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a thin film photoelectric conversion device with improved characteristics.

The first aspect of the present invention is a thin film photoelectric conversion device including a transparent electrode layer, one or more photoelectric conversion units, and a back electrode layer, which are sequentially arranged from the light incident side. It is a photoelectric conversion unit arranged in the order of a semiconductor layer, a substantially intrinsic semiconductor photoelectric conversion layer, and an n-type semiconductor layer,
The thin film photoelectric conversion characterized in that the transparent electrode layer contains Zn, Mg, O and doping impurities, and the transparent electrode layer is in contact with the p-type semiconductor layer included in one of the photoelectric conversion units at the interface. Device. By using a transparent electrode layer containing Zn, Mg, O, and a doping impurity, the short wavelength transmittance of the transparent electrode layer is increased and the spectral sensitivity of the short wavelength thin film photoelectric conversion device is improved. In addition, by using a photoelectric conversion unit in which a p-type semiconductor layer, a substantially intrinsic semiconductor photoelectric conversion layer, and an n-type semiconductor layer are arranged in this order from the light incident direction, transparent containing Zn, Mg, O, and doping impurities. Since the electrode layer is in contact with the p-type semiconductor, the transparent electrode layer containing Zn, Mg, O, and doping impurities does not require the function of a strong n-type semiconductor, but only functions as a transparent electrode. A transparent electrode layer containing Zn, Mg, O, and doping impurities can be used as the transparent electrode layer without any influence of the band discontinuity.

  In addition, by using a pin junction, it is not necessary to take out to the atmosphere at the semiconductor junction interface, and the influence of oxidation and impurity adhesion on the semiconductor junction interface is eliminated.

  The present invention is the thin film photoelectric conversion device according to claim 1, wherein the doping impurity includes one or more elements selected from the group consisting of B, Al, Ga, and In.

  The transparent electrode layer preferably contains a Group 3 element as the doping impurity, particularly one or more elements selected from the group consisting of B, Al, Ga and In. By including a group 3 element, the resistance of ZMO can be easily reduced. In particular, B, Al, Ga, and In can be easily obtained industrially as a material for a sputtering target, so that the cost is reduced.

  The present invention is also a method for producing the thin film photoelectric conversion device, wherein the method includes a step of forming the transparent electrode layer by a sputtering method. By forming by sputtering, there is an effect that a ZMO thin film can be formed in a large area. Moreover, since a low-temperature process of 200 ° C. or lower can be used, there is an effect that an inexpensive substrate such as glass or plastic film after solidification can be used.

  The present invention is also a method for producing the thin film photoelectric conversion device, wherein the transparent electrode layer is formed by a low pressure CVD method. By forming ZMO by a low pressure CVD method, there is an effect that unevenness effective for light confinement can be formed at a low film formation temperature of 200 ° C. or lower. Moreover, since a low-temperature process of 200 ° C. or lower can be used, there is an effect that an inexpensive base such as glass or plastic film after solidification can be used. In addition, the low-pressure thermal CVD method can form a film at a film formation speed that is one digit or more faster than the sputtering method, and has a high utilization efficiency of raw materials, and thus has an effect of reducing the manufacturing cost.

In the present invention, the raw material of Mg used in the low-pressure CVD method is bismethylcyclopentadienylmagnesium {Mg (CH ₃ C ₅ H ₄ ) ₂ , abbreviation MeCp ₂ Mg}, and bisethylcyclopentadienylmagnesium. _{{Mg (C 2 H 5 C} 5 H 4) 2, abbreviated EtCp ₂ Mg} is one or more selected from the group consisting of a method for manufacturing a thin film photoelectric conversion device, it is. With this configuration, a relatively high vapor pressure can be obtained as the organometallic vapor containing Mg, and there is an effect that it can be easily used for the low pressure CVD method.

  The present invention also provides a method for producing a thin film photoelectric conversion device, wherein a source of doping impurities used in the low-pressure CVD method is a gas containing one or more selected from the group consisting of diborane, trimethylboron, and boron trifluoride. Method. With this configuration, since it is a gas at normal temperature and pressure, there is an effect that it is not necessary to use a vaporizer and the manufacturing cost can be reduced.

  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, it is clear that the low pressure thermal CVD method includes an organic metal CVD method under reduced pressure (abbreviation, MO-CVD method).

  According to the present invention, by using a transparent electrode layer containing Zn, Mg, O, and doping impurities (in other words, ZMO containing doping impurities) for the transparent electrode layer, the transmittance of the short wavelength of the transparent electrode layer is improved. The spectral sensitivity of the short wavelength thin film photoelectric conversion device is improved, the short circuit current density (Jsc) is increased, and a thin film photoelectric conversion device with improved characteristics can be provided. In addition, the photoelectric conversion unit is a photoelectric conversion unit that is arranged in the order of the p-type semiconductor layer, the substantially intrinsic semiconductor photoelectric conversion layer, and the n-type semiconductor layer from the light incident direction (in one embodiment, a pin type ZMO can be used as a transparent electrode layer without the influence of the band discontinuity of the conduction band, and the ZMO characteristics can be optimized independently of the semiconductor layer. A thin film photoelectric conversion device with improved characteristics can be provided.

  Furthermore, by using a pin junction, there is no need to take out to the atmosphere at the semiconductor junction interface, and there is no influence of oxidation or impurity adhesion on the semiconductor junction interface, and a thin film photoelectric conversion device with improved characteristics or yield is provided. it can.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 can also refer to a thin film photoelectric conversion device according to an embodiment of the present invention. That is, the integrated thin-film solar cell according to one embodiment of the present invention also includes the thin-film photoelectric conversion device substrate 1 including the translucent insulating substrate 11 and the transparent electrode layer 12 formed thereon (see FIG. 1). ). On the substrate 1, a semiconductor layer 20 including a front photoelectric conversion unit 2 and a rear photoelectric conversion unit 3 that are sequentially stacked is formed, and a back electrode layer 4 is formed thereon.

  The translucent insulating substrate 11 is mainly a plate-like member or sheet-like member made of glass, transparent resin, or the like. In particular, when a glass substrate is mainly used as the light-transmitting insulating substrate, it is preferable as the light-transmitting insulating substrate because of its high transmittance and low cost.

  Since the translucent insulating substrate 11 is positioned on the light incident side when the thin film photoelectric conversion device 5 configured as shown in FIG. 1 is configured, for example, it transmits more sunlight and is amorphous or crystalline. In order to be absorbed by a high-quality photoelectric conversion unit, it is preferably as transparent as possible, 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 so as to reduce the light reflection loss on the light incident surface of sunlight.

  Although it is possible to use a glass substrate alone as the light-transmitting insulating substrate 11, the light-transmitting insulating substrate 11 further includes a light-transmitting base 111 such as glass having a smooth surface and a light-transmitting property. More preferably, the base layer 112 is a laminate. At this time, the translucent underlayer 112 has fine surface irregularities having a root mean square roughness of 5 to 50 nm at the interface on the transparent electrode layer 12 side, and the convex parts are curved surfaces. Is preferred. The surface area ratio can be controlled to a desired value by providing the light-transmitting underlayer 112 as described above.

The translucent underlayer 112 can be produced, for example, by applying translucent fine particles 1121 together with a binder forming material containing a solvent. Specifically, examples of the light-transmitting binder 1122 include metal oxides such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, and tantalum oxide. The light-transmitting fine particles 1121 include silica (SiO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), indium tin oxide (ITO), or magnesium fluoride. (MgF ₂ ) or the like can be used. Examples of the method for applying the coating solution on the surface of the translucent substrate 111 include a dipping method, a spin coat method, a bar coat method, a spray method, a die coat method, a roll coat method, and a flow coat method. A roll coating method is preferably used to form the fine particles finely and uniformly. When the coating operation is completed, the coated thin film is immediately dried by heating.

  Note that FIG. 1 illustrates an embodiment in which a light-transmitting base layer 112 is provided on one surface of the light-transmitting base 111, but the same surface as the light-transmitting base layer 112 is provided on the opposite surface of the light-transmitting base 111. An aspect provided with material may be sufficient. In an aspect in which the material of the light-transmitting base layer 112 is provided on both surfaces of the light-transmitting substrate 111, one surface serves as the base layer, contributing to an increase in the unevenness of the transparent electrode layer and an improvement in adhesion, and the opposite surface. The surface on the light incident side is more preferable in the sense that it works as an antireflection film and the effect of light confinement is further enhanced. When the dipping method is used, the material of the light-transmitting underlayer 112 can be simultaneously formed on both surfaces of the light-transmitting substrate 111.

As a material of the transparent electrode layer 12 disposed on the light-transmitting insulating substrate 11, Zn _1-x Mg _x O containing doping impurities (0 <x <1, abbreviated as ZMO) is used. The doping impurity preferably contains one or more elements selected from the group consisting of B, Al, Ga, and In. In particular, B and Al are preferable because of low cost, and B is particularly preferable because a gaseous material can be easily obtained. The impurities preferably include 5 × 10 ¹⁹ atoms / cm ³ or more of Al atoms or 2 × 10 ¹⁹ atoms / cm ³ or more of B atoms. In addition to doping impurities, hydrogen and carbon may be included as impurities. In particular, in the case of containing 2 × 10 ²⁰ atoms / cm ³ or more of H atoms, a texture structure having a light confinement effect is formed even at a low temperature of 200 ° C. or less, which is preferable.

The Mg ratio in the transparent electrode layer containing Zn, Mg, O, and doping impurities can be defined by the following formula (1).
(Mg ratio) = (Mg atom number density) / {(Mg atom number density) + (Zn atom number density)} × 100 [%] (1) Formula Transparent electrode layer containing Zn, Mg, O, and doping impurities In order to increase the transmittance of the short wavelength, the Mg ratio is desirably larger than 10%, and more desirably larger than 15%. In order to reduce the sheet resistance of the transparent electrode layer containing Zn, Mg, O and doping impurities, the Mg ratio is preferably less than 40%, and more preferably less than 30%.

In the present application, a transparent electrode layer containing Zn, Mg, O, and doping impurities is employed. Until now, in a thin film photoelectric conversion device including a pin type photoelectric conversion unit, ITO, SnO ₂ , ZnO or the like has been used as a transparent electrode layer. Since MgO is an insulator, it is clear that ZMO in which Mg is added to ZnO of the conventional transparent electrode layer has a high resistivity, and is not desirable as a transparent electrode layer. Further, if a large amount of doping impurities is added to compensate for the increase in resistivity, the transmittance at a long wavelength is lowered, which is not desirable as a transparent electrode layer. In addition, ZnO containing a doping impurity conventionally uses Zn, O, and a doping impurity element as a raw material. However, since ZMO containing a doping impurity further requires Mg, the raw material cost increases. Specifically, when the manufacturing method is sputtering, the cost of the target increases. In addition, when the manufacturing method is a low pressure CVD method, in the case of ZnO, diethylzinc (DEZ), water, and B ₂ H ₆ are used as raw materials, whereas two vaporizers for DEZ and water are used. In addition, since ZMO containing doping impurities further uses MeCp ₂ Mg or EtCp ₂ Mg, another vaporizer is required, and the device cost increases with the raw material cost. In addition, since MeCp ₂ Mg and MgEtCp ₂ Mg have vapor pressures that are 2-3 orders of magnitude lower than DEZ and water, it is more difficult to vaporize than DEZ and water. Therefore, it is considered that there is little reason for those skilled in the art to actively adopt a thin film photoelectric conversion device including a pin-type photoelectric conversion unit using ZMO containing a doping impurity as a transparent electrode layer.

  However, when the present inventor applied ZMO containing a doping impurity as a transparent electrode layer to a thin film photoelectric conversion device including a pin-type photoelectric conversion unit, it shows characteristics that can be sufficiently used as a transparent electrode layer at an industrially acceptable cost. It became clear.

For example, the transparent electrode layer containing Zn, Mg, O, and doping impurities of the present invention can be formed by sputtering. It can be manufactured using a target containing Zn, Mg, O and doping impurities. The doping impurities preferably include one or more selected from the group consisting of B, Al, Ga and In. A plurality of targets may be used. For example, a ZnO target containing Al as a doping impurity and an MgO target can be used. In this case, sputtering may be performed by simultaneously discharging the two targets, or the two targets may be sputtered alternately in a short time or alternately at a predetermined frequency interval. Ar gas is preferably used when sputtering. In order to optimize the oxygen concentration in the transparent electrode layer containing Zn, Mg, O, and doping impurities, O ₂ gas can be added. Further, H ₂ gas can be added in order to improve the resistivity of the transparent electrode layer containing Zn, Mg, O, and doping impurities.

  Further, the transparent electrode layer containing Zn, Mg, O and doping impurities of the present invention can be formed by a low pressure CVD method at a substrate temperature of 200 ° C. or lower. The substrate temperature here means the temperature of the surface where the substrate is in contact with the heating unit of the film forming apparatus. When the low pressure CVD method is used, the film forming speed is higher than that of the sputtering method, and the manufacturing time is shortened. Therefore, the manufacturing cost can be reduced. Further, although it is difficult to form a texture structure on a transparent electrode layer containing Zn, Mg, O, and doping impurities by sputtering, it is transparent that contains Zn, Mg, O, and doping impurities produced by low-pressure CVD. The electrode layer is preferable because it can form a texture structure at a low manufacturing temperature of 200 ° C. or less and can increase the light confinement effect.

Specifically, the formation of a transparent electrode layer containing Zn, Mg, O, and doping impurities by low-pressure CVD is performed by using organic materials such as diethyl zinc (DEZ), dimethyl zinc, or Mg as an organic metal vapor. MeCp ₂ Mg or EtCp ₂ Mg is suitably used as the metal vapor, and water is suitably used as the oxidant vapor. In particular, DEZ is preferably used as a Zn raw material because it has a vapor pressure close to that of water. As the Mg raw material, MeCp ₂ Mg is particularly preferred because it has a higher vapor pressure than EtCp ₂ Mg. As the doping gas, diborane (B ₂ H ₆ ), trimethylboron {B (CH ₃ ) ₃ }, and boron trifluoride (BF ₃ ) are preferably used because they are gases at room temperature and normal pressure, and particularly B ₂ H _6. Is preferably used because of its high decomposition efficiency. One or more of H ₂ , He, Ar, and N ₂ may be added as a dilution gas. It is preferable to carry out ZMO film formation by introducing these mixed gases into a vacuum chamber maintained at a pressure of 5 to 200 Pa. Specifically, the flow rate of DEZ is 10 to 1000 sccm, the flow rate of MeCp ₂ Mg is 1 to 500 sccm, the flow rate of water is 10 to 1000 sccm, the flow rate of H ₂ is 100 to 10,000 sccm, and the flow rate of Ar is 100 to 10,000 sccm. B ₂ H ₆ is preferably formed into a film at 0.1% to 10% with respect to DEZ.

  The transparent electrode layer containing Zn, Mg, O, and doping impurities has a particle diameter of about 50 to 500 nm and a height of the unevenness of about 20 to 200 nm. It is preferable at the point which acquires the confinement effect. The particle size can be measured with a scanning microscope such as an atomic force microscope (AFM) or a scanning tunneling microscope (STM), a scanning electron microscope (SEM), or a transmission electron microscope (TEM). Further, the height of the unevenness can be measured by AFM, STM, TEM or the like. The haze ratio is preferably 15% or more, and more preferably 20% or more from the viewpoint of obtaining the light confinement effect.

  The sheet resistance of the transparent electrode layer containing Zn, Mg, O, and doping impurities is 20Ω / □ or less, preferably 10Ω / □ or less, in order to suppress resistance loss.

  The average thickness of the transparent electrode layer containing Zn, Mg, O, and doping impurities is preferably 0.7 to 5 μm, and more preferably 1 to 3 μm. This is because if the transparent electrode layer containing Zn, Mg, O, and doping impurities is too thin, it is difficult to sufficiently provide unevenness that effectively contributes to the light confinement effect, and the necessary conductivity for the transparent electrode layer. If it is too thick, light is absorbed by the transparent electrode layer itself containing Zn, Mg, O, and doping impurities, and passes through the transparent electrode layer containing Zn, Mg, O, and doping impurities to reach the photoelectric conversion unit. This is because the amount of light decreases and the efficiency decreases. Furthermore, when it is too thick, the film forming cost increases due to an increase in the film forming time.

  Further, the surface area ratio (Sdr) is desirably 55% or more and 95% or less under the film forming conditions of the transparent electrode layer containing Zn, Mg, O, and doping impurities. When Sdr is too large, the open circuit voltage (Voc) and the fill factor (FF) decrease, and Eff decreases. In some cases, the short circuit current density (Jsc) decreases and the conversion efficiency (Eff) decreases. When Sdr is large, Voc and FF decrease because the unevenness of the substrate for the thin film photoelectric conversion device becomes sharp, the coverage of the silicon semiconductor layer on the transparent electrode layer deteriorates, and the contact resistance increases or leaks. This is thought to be due to an increase in current. The reason why Jsc decreases when Sdr is large is thought to be that the growth of the semiconductor layer on the transparent electrode layer is inhibited, the film quality of the semiconductor layer is deteriorated, and loss due to carrier recombination increases. On the contrary, when Sdr is too small, the unevenness of the thin film photoelectric conversion device substrate becomes small, so that the effect of light confinement is weakened, the short-circuit current density (Jsc) is lowered, and Eff is lowered. The surface area ratio can be controlled to an optimum value by controlling the film forming conditions of the transparent electrode layer containing Zn, Mg, O, and doping impurities. For example, in the low pressure CVD method, the surface area ratio of the transparent electrode layer containing Zn, Mg, O, and doping impurities varies greatly depending on the film forming conditions such as the substrate temperature, the raw material gas flow rate, and the pressure. The surface area ratio can be set to a desired value.

  If an amorphous silicon-based material is selected as the front photoelectric conversion unit 2, it has sensitivity to light of about 360 to 800 nm, and if a crystalline silicon-based material is selected for the rear photoelectric conversion unit 3, it is longer than about 1200 nm. Sensitivity to light. Therefore, the thin film photoelectric conversion device 5 arranged in this order from the light incident side to the front photoelectric conversion unit 2 of the amorphous silicon-based material and the rear photoelectric conversion unit 3 of the crystalline silicon-based material allows the incident light in a wider range. Effective use becomes possible. However, “silicon-based” materials include silicon alloy semiconductor materials containing silicon such as silicon carbide and silicon germanium in addition to silicon.

  The front photoelectric conversion unit 2 is formed by stacking each semiconductor layer by a plasma CVD method in the order of, for example, a pin type. Specifically, for example, a p-type amorphous silicon carbide layer doped with 0.01 atomic% or more of boron, which is a conductivity type determining impurity atom, is used as one conductivity type layer 21, and an intrinsic amorphous silicon layer is a photoelectric conversion layer. The n-type microcrystalline silicon layer doped with 0.01 atomic% or more of phosphorus, which is a conductivity-determining impurity atom, may be deposited as the reverse conductivity type layer 23 in this order.

  The rear photoelectric conversion unit 3 is formed by stacking each semiconductor layer by a plasma CVD method in the order of, for example, a pin type. Specifically, for example, a p-type microcrystalline silicon layer doped with 0.01 atomic% or more of boron, which is a conductivity-determining impurity atom, is used as one conductivity-type layer 31, and an intrinsic crystalline silicon layer is used as a photoelectric conversion layer 32. An n-type microcrystalline silicon layer doped with 0.01 atomic% or more of phosphorus, which is a conductivity type determining impurity atom, may be deposited as the reverse conductivity type layer 33 in this order.

As the back electrode layer 4, it is preferable to form one or more materials selected from the group consisting of Al, Ag, Au, Cu, Pt and Cr as at least one metal layer 42 by sputtering or vapor deposition. Further, it is preferable to form a conductive oxide layer 41 such as ITO, SnO ₂ , or ZnO as a part of the back electrode layer 4 between one or more photoelectric conversion units. The conductive oxide layer 41 enhances the adhesion between the one or more photoelectric conversion units and the back electrode layer 4, increases the light reflectance of the back electrode layer 4, and further changes the chemical change of the photoelectric conversion unit. It has a function to prevent.

  Although FIG. 1 shows a thin film photoelectric conversion device in which a transparent electrode layer, a photoelectric conversion unit, and a back electrode layer are stacked in this order on one main surface of a translucent insulating substrate, the thin film photoelectric devices stacked in reverse order as follows. A conversion device is also effective. That is, a thin film photoelectric conversion device in which a substrate, a back electrode layer, one or more photoelectric conversion units, and a ZMO transparent electrode layer are stacked in this order, the photoelectric conversion unit being an n-type semiconductor layer, a substantially intrinsic semiconductor photoelectric conversion layer Even a thin film photoelectric conversion device laminated in the order of the p-type semiconductor layer is effective. In the thin film photoelectric conversion device having such a structure, since light is incident from the opposite surface of the substrate, an opaque substrate can be used, and the choice of a material for the substrate becomes wide. For example, a flexible thin film photoelectric conversion device can also be manufactured using polyimide as a heat-resistant plastic film, stainless steel foil as a metal, or the like as an opaque substrate.

  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.

Example 1
As Example 1 of the present invention, a transparent electrode layer containing Zn, Mg, O, and doping impurities was produced. A transparent electrode layer containing Zn, Mg, O, and a doping impurity was produced on a glass substrate having a thickness of 0.7 mm and 125 mm × 125 mm by sputtering. The composition of the target was 15 wt. %, ZnO is 82 wt. %, Al ₂ O ₃ is 3 wt. %. The pressure was 0.5 Pa at an Ar flow rate of 50 sccm. Sputtering was performed using DC discharge with a power density of 300 mW / cm ² . The film forming speed was about 0.5 nm / s.

  The film thickness obtained from the interference of the reflection spectrum of the produced transparent electrode layer containing Zn, Mg, O and doping impurities was about 400 nm. When the Mg ratio in this transparent electrode layer was measured by energy dispersive X-ray spectroscopy (abbreviation EDX), the Mg ratio was 24.8%.

  The absorption coefficient α was determined from the transmission spectrum and the reflection spectrum, and the optical energy E [eV] was plotted on the X axis and (αE) ^ 2 was plotted on the Y axis, and the intercept of the X axis was determined as the band gap Eg. As a result, the band gap Eg of Example 1 was 3.72 eV. The sheet resistance was 8.8Ω / □, and the haze ratio was 4.3%.

  FIG. 2 shows a transparent electrode layer containing Zn, Mg, O, and doping impurities of Example 1, and transmission spectra of Comparative Example 1 and Example 2 described later. The wavelength at which the transmittance on the short wavelength side of Example 1 was 10% was 337 nm, and the wavelength at which the transmittance was 60% was 361 nm.

(Comparative Example 1)
As a conventional comparative example 1, a transparent electrode layer of ZnO containing doping impurities was prepared. The same manufacturing method as in Example 1 was used except that the composition of the target was different. The composition of the target was 97 wt. %, Al ₂ O ₃ is 3 wt. %. The film forming speed was about 0.5 nm / s.
The thickness of the produced ZnO film containing doping impurities was about 400 nm. The Mg ratio in the film was 0%. The band gap was 3.30 eV. The sheet resistance was 6.5Ω / □, and the haze ratio was 3.7%.

  As shown in FIG. 2, the wavelength at which the transmittance on the short wavelength side of the ZnO film containing the doping impurity of Comparative Example 1 was 10% was 377 nm, and the wavelength at which the transmittance was 60% was 408 nm.

(Example 2)
As Example 2 of the present invention, a transparent electrode layer containing Zn, Mg, O, and doping impurities was produced. The same manufacturing method as in Example 1 was used except that the composition of the target was different. The composition of the target is 20 wt. %, ZnO is 77 wt. %, Al ₂ O ₃ is 3 wt. %. The film forming speed was about 0.5 nm / s. The film thickness of the produced transparent electrode layer containing Zn, Mg, O and doping impurities was about 400 nm. The Mg ratio in the film was 33.8%. The band gap was 3.91 eV. The sheet resistance was 11.8Ω / □ and the haze ratio was 4.5%.

  As shown in the transmission spectrum in FIG. 2, the wavelength at which the transmittance on the short wavelength side of the transparent electrode layer containing Zn, Mg, O, and doping impurities of Example 2 is 10% is 322 nm, and the transmittance is 60%. The resulting wavelength was 347 nm.

(Summary of Examples 1 and 2 and Comparative Example 1)
From FIG. 2, it can be seen that as the Mg ratio increases, the rising edge of the transmission spectrum on the short wavelength side shifts to the short wavelength side. The wavelength at which the transmittance becomes 10% is obtained by comparing ZMO (Zn, Mg, O, and doping impurities) with doping impurities with a Mg ratio of 24.8% in Example 1 with respect to ZnO containing doping impurities in Comparative Example 1. The transparent electrode layer containing 40 nm has a short wavelength of 40 nm, and ZMO (transparent electrode layer containing Zn, Mg, O, and doping impurities) containing a doping impurity of 33.8% in Example 2 has a short wavelength of 55 nm. Further, the wavelength at which the transmittance is 60% is that the ZnO containing the doping impurity of Comparative Example 1 is doped with ZMO (Zn, Mg, O, and doping impurities) with the doping ratio of 24.8% of Mg in Example 1. 47 nm wavelength is short in the transparent electrode layer containing 3) and ZMO (transparent electrode layer containing Zn, Mg, O, and doping impurities) containing the doping impurity with the Mg ratio of 33.8% in Example 2 has a short wavelength of 61 nm. . Therefore, compared with ZnO containing doping impurities, the transparent electrode layer of ZMO containing doping impurities (transparent electrode layer containing Zn, Mg, O, and doping impurities) transmits light having a shorter wavelength, and thin film photoelectric conversion. It can be said that the short-wave current density can be improved by increasing the short wavelength sensitivity of the device.

(Example 3)
As Example 3 of the present invention, a transparent electrode layer containing Zn, Mg, O, and doping impurities was produced by low-pressure CVD. A light-transmitting base layer 112 containing SiO ₂ fine particles 1121 was formed on a light-transmitting substrate 111 of a glass substrate having a thickness of 0.7 mm and 125 mm × 125 mm, whereby a light-transmitting insulating substrate 11 was obtained. The coating liquid used for forming the light-transmitting underlayer 111 was tetraethoxysilane added to a mixture of a spherical silica dispersion having an average particle diameter of 100 nm, water and ethyl cellosolve, and hydrochloric acid was further added to add tetraethoxysilane. A product obtained by hydrolyzing silane was used. After coating the coating solution on glass with a printing machine, drying is performed at 90 ° C. for 30 minutes, and then heating is performed at 450 ° C. for 5 minutes to obtain a light-transmitting insulating substrate 11 having fine irregularities formed on the surface. It was. When the surface of the translucent insulating substrate 11 was observed with an atomic force microscope (AFM), irregularities in which the convex portions were curved reflecting the shape of the fine particles were confirmed. The root mean square roughness (RMS) of the light-transmitting underlayer 112 formed under these conditions was 5 to 50 nm. In addition, RMS in this invention is calculated | required from the atomic force microscope (AFM) image which observed the square area | region whose one side is 5 micrometers (ISO 4287/1). The non-contact mode of Nano-R system (manufactured by Pacific Nanotechnology) was used for this AFM measurement.

A transparent electrode layer 12 containing Zn, Mg, O, and doping impurities was formed on the obtained translucent insulating substrate 11 by a low pressure thermal CVD method. This transparent electrode layer 12 has a substrate temperature of 160 ° C., a pressure of 20 Pa, a flow rate of diethyl zinc (DEZ) of 400 sccm, a flow rate of MeCp ₂ Mg of 120 sccm, a flow rate of water of 1000 sccm, a diborane (B ₂ H ₆ ) flow rate of ₂ sccm, and argon. It was formed at a flow rate of 500 sccm and a hydrogen flow rate of 500 sccm. At this time, the film forming speed was 2 nm / s. That is, the deposition rate of the transparent electrode layer containing Zn, Mg, O, and doping impurities of Example 3 manufactured by the low pressure CVD method is the same as that of Zn, Mg, O, and doping of Examples 1 and 2 manufactured by the sputtering method. The film-forming speed of the transparent electrode layer containing impurities was four times faster.

  The film thickness obtained from interference of the reflection spectrum of the obtained transparent electrode layer 12 containing Zn, Mg, O and doping impurities was 1.8 μm. The Mg ratio in the film determined from EDX was 29.7%. The sheet resistance was 13.2 Ω / □. The surface area ratio (Sdr) was 72.5%. The Sdr in the present invention is obtained from an atomic force microscope (AFM) image obtained by observing a square region having a side of 5 μm. The non-contact mode of Nano-R system (manufactured by Pacific Nanotechnology) was used for this AFM measurement. The haze ratio measured using a C light source was 28.4%.

(Comparative Example 2)
As Comparative Example 2 by the conventional method, a transparent electrode layer of ZnO containing doping impurities was produced by a low pressure CVD method. The structure and the manufacturing method were the same as those in Example 3 except that MeCp ₂ Mg was not used when forming ZnO containing doping impurities. The film forming speed was 2 nm / s.

  The film thickness of the transparent electrode layer of the obtained ZnO film containing doping impurities was 1.8 μm. The sheet resistance was 12.4Ω / □. The surface area ratio (Sdr) was 75.3%. The haze ratio was 27.0%.

Example 4
As Example 4 of the present invention, by using the transparent electrode layer of Example 3 and forming an amorphous silicon photoelectric conversion unit, a crystalline silicon photoelectric conversion unit, and a back electrode layer thereon, a laminated thin film A photoelectric conversion device was produced. FIG. 1 is a conceptual diagram of a cross-sectional structure of the thin film photoelectric conversion device of Example 4.

  Specifically, on the transparent electrode layer 12 of Example 1, a one-conductivity type layer 21 composed of a p-type microcrystalline silicon layer having a thickness of 10 nm and a p-type amorphous silicon carbide layer having a thickness of 15 nm. Forming a front photoelectric conversion unit 2 of an amorphous photoelectric conversion unit comprising a photoelectric conversion layer 22 of 350 nm intrinsic amorphous silicon layer and a reverse conductivity type layer 23 of n-type microcrystalline silicon layer having a thickness of 15 nm; One conductivity type layer 31 of a p-type microcrystalline silicon layer having a thickness of 15 nm, a photoelectric conversion layer 32 having an intrinsic crystalline silicon layer having a thickness of 1.5 μm, and a reverse conductivity type of an n-type microcrystalline silicon layer having a thickness of 15 nm. The rear photoelectric conversion unit 3 of the crystalline silicon photoelectric conversion layer unit composed of the layer 33 was sequentially formed by the plasma CVD method. Further, an Al-doped ZnO conductive oxide layer 41 having a thickness of 90 nm and an Ag metal layer 42 having a thickness of 200 nm are sequentially formed as the back electrode layer 4 by a sputtering method to produce a stacked thin film photoelectric conversion device. did.

The thin film photoelectric conversion device 5 of Example 4 obtained in this way was irradiated with AM 1.5 light at a light amount of 100 mW / cm ² to measure the output characteristics, and the open circuit voltage (Voc) was 1.291 V, short-circuited. The current density (Jsc) was 13.25 mA / cm ² , the fill factor (FF) was 0.705, and the conversion efficiency (Eff) was 12.06%.

(Comparative Example 3)
In Comparative Example 3, a thin film photoelectric conversion device similar to Example 4 was produced. That is, it was different from Example 4 only by using the ZnO layer containing the doping impurity of Comparative Example 2 for the transparent electrode layer. 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 4, Voc was 1.292 V, Jsc was 12.90 mA / cm ² , FF was 0.708, and Eff Was 11.80%.

(Comparative Example 4)
In Comparative Example 4, a thin film photoelectric conversion device similar to Example 4 was produced. That is, the thin film photoelectric conversion device of Comparative Example 4 has no translucent underlayer 112, SnO containing F as a doping impurity instead of the transparent electrode layer containing Zn, Mg, O, and a doping impurity as a transparent electrode layer. It was different from Example 4 only in the three points that _two layers were used and that one conductivity type layer 21 consisted only of a p-type amorphous silicon carbide layer having a thickness of 15 nm. As the substrate 1 for a thin film photoelectric conversion device, a commercially available product in which a SnO ₂ electrode layer 12 containing a doping impurity is formed by a thermal CVD method is used, and its haze ratio is 13.2%. A SnO ₂ electrode layer containing a doping impurity The sheet resistance was 12.5Ω / □. 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 4, Voc was 1.302 V, Jsc was 12.52 mA / cm ² , FF was 0.710, and Eff Was 11.56%.

(Collection efficiency of Example 4, Comparative Examples 3 and 4)
In FIG. 3, the collection efficiency spectrum of the thin film photoelectric conversion apparatus of Example 4 and Comparative Examples 3 and 4 is shown. When measuring the collection efficiency spectrum, the collection efficiency of the front photoelectric conversion unit was measured by irradiating with red bias light, and the collection efficiency of the rear photoelectric conversion unit was measured by irradiating with blue bias light. Comparing the wavelengths at which the collection efficiency of 300 to 400 nm starts to rise on the short wavelength side, Comparative Example 3 using ZnO containing a doping impurity for the transparent electrode layer was about 360 nm, and SnO ₂ containing a doping impurity was used for the transparent electrode layer. Comparative Example 4 has a thickness of 300 nm, and Example 4 in which ZMO containing a doping impurity (a transparent electrode layer containing Zn, Mg, O, and doping impurities) is used as the transparent electrode layer has a thickness of 300 nm. This is because the band gap of the transparent electrode layer containing Zn, Mg, O, and doping impurities is larger than that of ZnO containing doping impurities, and light having a short wavelength equivalent to that of SnO ₂ containing doping impurities can be transmitted. .

  Moreover, when comparing the long-wavelength skirts having a collection efficiency of 750 to 1100 nm, Example 4 and Comparative Example 3 are substantially equivalent, and Comparative Example 4 is low. This is because ZMO containing a doping impurity (transparent electrode layer containing Zn, Mg, O, and doping impurities) has irregularities with a high haze ratio of 25% or more like ZnO containing doping impurities. This is because the light confinement effect is high.

  That is, compared with Comparative Example 3 and Comparative Example 4, Example 4 using the transparent electrode layer containing Zn, Mg, O, and doping impurities as the transparent electrode layer improved the collection efficiency, and thus increased Jsc. Eff was improved.

(Comparative Example 5)
In Comparative Example 5, a thin film photoelectric conversion device similar to Example 4 was produced. That is, without using the B ₂ H ₆ in the production of the transparent electrode layer, only in that with ZMO layer containing no doping impurity as a transparent electrode layer, was different from Example 4. When the output characteristics of the obtained thin film photoelectric conversion device of Comparative Example 5 were measured in the same manner as in Example 4, the IV curve was linear and Eff = 0%, which was not usable as a solar cell.

(Example 5)
As Example 5 of the present invention, on a stainless steel substrate, by forming a back electrode layer, a crystalline silicon photoelectric conversion unit arranged in the order of n, i, and p type, and a transparent electrode layer of ZMO containing doping impurities, A thin film photoelectric conversion device was produced. This is a so-called single-structure thin-film photoelectric conversion device having only one photoelectric conversion unit. FIG. 4 is a conceptual diagram of a cross-sectional structure of the thin film photoelectric conversion device of Example 5.

Specifically, on a stainless steel substrate having a thickness of 0.5 mm and 30 mm × 30 mm, an Ag metal layer 42 having a thickness of 200 nm and an Al-doped ZnO conductive oxide layer 41 having a thickness of 90 nm are formed as the back electrode layer 4. Were sequentially formed by sputtering. On top of that, an n-type microcrystalline silicon layer reverse-conductivity type layer 33 having a thickness of 15 nm, an intrinsic crystalline silicon layer photoelectric conversion layer 32 having a thickness of 2.0 μm, and a p-type microcrystalline silicon layer having a thickness of 15 nm are formed. Crystalline silicon photoelectric conversion layer units 34 composed of one conductivity type layer 31 were sequentially formed by plasma CVD. Further, the transparent electrode layer 12 containing Zn, Mg, O, and doping impurities was formed by the low pressure CVD method in the same manner as in Example 3 to form a thin film photoelectric conversion device. When the output characteristics of the obtained thin film photoelectric conversion device of Example 5 were measured in the same manner as in Example 4, Voc was 0.514 V, Jsc was 25.0 mA / cm ² , FF was 0.702, and Eff Was 9.02%.

(Comparative Example 6)
In Comparative Example 6, a thin film photoelectric conversion device similar to Example 5 was produced. That is, it was different from Example 5 only by using a ZnO layer containing a doping impurity for the transparent electrode layer. The conditions for forming the ZnO layer were the same as in Comparative Example 2. When the output characteristics of the obtained thin film photoelectric conversion device of Comparative Example 6 were measured in the same manner as in Example 4, Voc was 0.523 V, Jsc was 23.6 mA / cm ² , FF was 0.695, and Eff Was 8.6%.

  In Example 5, it can be seen that by using ZMO containing a doping impurity in the transparent electrode layer, Eff is improved by increasing Jsc as compared with Comparative Example 6.

Sectional drawing of the board | substrate for photoelectric conversion apparatuses of one Embodiment of this invention, and a thin film photoelectric conversion apparatus. The transmission spectrum of the transparent electrode layer of Example 1, Example 2 of this invention, and the comparative example 1 of the conventional method. The collection efficiency spectrum of Example 4 of this invention and the comparative examples 3 and 4 of a conventional method. Sectional drawing of the thin film photoelectric conversion apparatus of Example 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate for photoelectric conversion devices 11 Translucent insulating substrate 111 Translucent substrate 112 Translucent foundation layer 1121 Translucent fine particle 1122 Translucent binder 12 Transparent electrode layer 20 Semiconductor layer 2 Front photoelectric conversion unit 21 One conductivity type layer DESCRIPTION OF SYMBOLS 22 Photoelectric conversion layer 23 Reverse conductive type layer 3 Back photoelectric conversion unit 31 One conductive type layer 32 Photoelectric conversion layer 33 Reverse conductive type layer 34 Crystalline photoelectric conversion unit 4 Back surface electrode layer 41 Conductive oxide layer 42 Metal layer 5 Thin film photoelectric Conversion device 6 Stainless steel substrate

Claims (6)

In a thin film photoelectric conversion device including a transparent electrode layer, one or more photoelectric conversion units, and a back electrode layer, which are sequentially arranged from the light incident side,
The photoelectric conversion unit is a photoelectric conversion unit arranged in the order of a p-type semiconductor layer, a substantially intrinsic semiconductor photoelectric conversion layer, and an n-type semiconductor layer from the light incident direction,
The thin film photoelectric conversion characterized in that the transparent electrode layer contains Zn, Mg, O and doping impurities, and the transparent electrode layer is in contact with the p-type semiconductor layer included in one of the photoelectric conversion units at the interface. apparatus.   The thin film photoelectric conversion device according to claim 1, wherein the doping impurity includes one or more elements selected from the group consisting of B, Al, Ga, and In.   A method for manufacturing the thin film photoelectric conversion device according to claim 1, comprising a step of forming the transparent electrode layer by a sputtering method.   A method for producing the thin film photoelectric conversion device according to claim 1, comprising a step of forming the transparent electrode layer by a low pressure CVD method. The raw materials for Mg used in the low-pressure CVD method are bismethylcyclopentadienyl magnesium Mg (CH ₃ C ₅ H ₄ ) ₂ and bisethylcyclopentadienyl magnesium Mg (C ₂ H ₅ C ₅ H ₄ ) _2. The manufacturing method of the thin film photoelectric conversion device of Claim 4 which is 1 or more selected from the group which consists of.   The thin film photoelectric conversion device according to claim 4 or 5, wherein a source of doping impurities used in the low pressure CVD method is a gas containing one or more selected from the group consisting of diborane, trimethylboron, and boron trifluoride. Manufacturing method.

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