JPWO2006049003A1 - Method for manufacturing thin film photoelectric conversion device - Google Patents

Abstract

To provide a production method capable of producing a highly efficient thin film photoelectric conversion device at low cost without increasing the resistivity even when a transparent conductive film made of zinc oxide having low heat resistance is used. The manufacturing method of the thin film photoelectric conversion device of the present invention includes one or more units of photoelectric conversion including a transparent conductive film containing zinc oxide as a main component and at least a first photoelectric conversion unit in order on one main surface of a translucent substrate. A method of manufacturing a thin film photoelectric conversion device comprising a unit and a back electrode layer, wherein the first photoelectric conversion unit is formed directly on the transparent conductive film, and the first photoelectric conversion is performed The one-conductivity-type semiconductor layer constituting the unit is silicon-based, and the silicon-based one-conductivity-type semiconductor layer is formed on the transparent conductive film maintained at a temperature of 170 ° C. or less, and the back electrode layer formation It is a manufacturing method of the thin film photoelectric conversion apparatus characterized by including the process heated later under atmospheric pressure of 170 degreeC or more.

Description

  The present invention relates to a method for manufacturing a thin film photoelectric conversion device in which a silicon-based single-conductivity type semiconductor layer is directly formed on a transparent conductive film containing zinc oxide as a main component.

  In recent years, thin film photoelectric conversion devices represented by thin film solar cells have also diversified, and crystalline thin film photoelectric conversion devices have been developed in addition to conventional amorphous thin film photoelectric conversion devices. It has become. Such a thin film photoelectric conversion device generally includes a transparent conductive film, one or more photoelectric conversion units, and a back electrode layer that are sequentially stacked on a light-transmitting substrate.

  One photoelectric conversion unit includes a photoelectric conversion layer sandwiched between one conductivity type semiconductor layer and another conductivity type semiconductor layer. As the one-conductivity-type semiconductor layer, a silicon-based one-conductivity-type semiconductor layer is often used. The photoelectric conversion layer is usually formed as an i-type layer. Here, for example, the one-conductivity-type semiconductor layer is a p-type layer, and in this case, the other-conductivity-type semiconductor layer is an n-type layer, and vice versa.

  The photoelectric conversion layer is not limited to an intrinsic semiconductor layer (i-type layer), but is a layer doped in a small amount of p-type or n-type within a range where loss of light absorbed by a doped impurity (dopant) does not become a problem. May be. The photoelectric conversion layer is preferably thicker for light absorption, but if it is thicker than necessary, the cost and time for film formation will increase.

  On the other hand, the p-type or n-type conductive semiconductor layer plays a role of generating an internal electric field in the photoelectric conversion unit, and an open-circuit voltage (one of important characteristics of the thin film photoelectric conversion device depending on the magnitude of the internal electric field). The value of Voc) is influenced. However, these conductive semiconductor layers are inactive layers that do not directly contribute to photoelectric conversion, and light absorbed by impurities doped in the conductive semiconductor layer is a loss that does not contribute to power generation. Therefore, it is preferable that the p-type and n-type conductive semiconductor layers have a thickness as small as possible as long as a sufficient internal electric field can be generated. The thickness of the conductive semiconductor layer is generally about 20 nm or less.

  Here, the photoelectric conversion unit or the thin film photoelectric conversion device has an amorphous photoelectric conversion layer that occupies the main part regardless of whether the p-type and n-type conductive semiconductor layers included therein are amorphous or crystalline. Is called an amorphous unit or an amorphous thin film photoelectric conversion device, and one having a crystalline photoelectric conversion layer is called a crystalline unit or a crystalline thin film photoelectric conversion device.

  As a method for improving the conversion efficiency of the thin film photoelectric conversion device, there is a method of stacking two or more photoelectric conversion units into a tandem type. In this method, a front unit including a photoelectric conversion layer having a large band gap is disposed on the light incident side of the thin film photoelectric conversion device, and a rear unit including a photoelectric conversion layer having a small band gap is sequentially disposed behind the front unit. Thus, photoelectric conversion can be performed over a wide wavelength range of incident light, thereby improving the conversion efficiency of the entire photoelectric conversion device. Among such tandem photoelectric conversion devices, those in which an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit are stacked are referred to as hybrid thin film photoelectric conversion devices.

  For example, the wavelength of light that can be photoelectrically converted by an amorphous silicon photoelectric conversion unit using i-type amorphous silicon as a photoelectric conversion layer is up to about 800 nm on the long wavelength side, but i-type crystalline silicon is used as the photoelectric conversion layer. The crystalline silicon photoelectric conversion unit described above can photoelectrically convert light having a longer wavelength up to about 1150 nm. However, although an amorphous silicon photoelectric conversion layer having a large light absorption coefficient may have a thickness of about 0.3 μm or less for light absorption, a crystalline silicon photoelectric conversion layer having a small light absorption coefficient has a long wavelength. In order to sufficiently absorb light, it is preferable to have a thickness of about 1.5 to 3 μm. That is, the crystalline photoelectric conversion layer is usually desired to have a thickness of about 5 to 10 times that of the amorphous photoelectric conversion layer.

  The translucent substrate normally serves to protect the transparent conductive film and the photoelectric conversion unit formed thereon from sufficient light and protect the photoelectric conversion device from impact and outside air when installed outdoors. For this reason, for example, when a crystalline photoelectric conversion unit having crystalline silicon as a photoelectric conversion layer is formed on a light-transmitting substrate, the light-transmitting substrate has sufficient light for light having a wavelength of about 350 to 1150 nm. It is desirable to have transmittance. In addition, it is desirable to use a material excellent in impact resistance and weather resistance as the translucent substrate.

  The transparent conductive film transmits light incident through the translucent substrate to the photoelectric conversion unit side without losing as much as possible, and efficiently takes out the photocurrent generated in the photoelectric conversion unit to the outside. For this reason, it is desirable to have both high transparency and low sheet resistance. When the sheet resistance increases, the series resistance of the photoelectric conversion device increases, and as a result, the fill factor (FF) decreases.

  Thin film photoelectric conversion devices can make the photoelectric conversion layer thinner than conventional bulk single crystal and polycrystal photoelectric conversion devices, but the light absorption is limited by the thickness of the photoelectric conversion layer. There is a problem of being done. Therefore, in order to more effectively use the light incident on the photoelectric conversion unit including the photoelectric conversion layer, after forming fine irregularities on the surface of the transparent conductive film in contact with the photoelectric conversion unit and scattering light at the interface, A device has been devised to extend the optical path length by making it enter the photoelectric conversion unit and to increase the amount of light absorption in the photoelectric conversion layer. 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.

  The height difference of the unevenness is generally about 0.05 μm to 0.3 μm.

  There is a haze ratio as an index representing the degree of unevenness of the transparent conductive film. This is equivalent to the light that is transmitted when the light from a specific light source is incident on a transparent substrate with a transparent conductive film divided by the scattered component whose optical path is bent and divided by all components. Measured using a C light source containing Generally, the haze ratio increases as the height difference between the projections and depressions increases, or as the distance between the projections and depressions of the projections and projections increases, and the light incident into the photoelectric conversion unit is effectively confined. The effect is excellent.

  Therefore, whether the amorphous silicon single layer thin film photoelectric conversion device or the hybrid thin film photoelectric conversion device described above can improve the transparency of the transparent conductive film, increase the haze ratio, and keep the sheet resistance low. If possible, a high short circuit current density (Jsc) can be maintained even when the photoelectric conversion layer is made thinner, and a high fill factor (FF) can be obtained, so that the performance of the thin film photoelectric conversion device can be improved. Moreover, it leads to lowering the manufacturing cost.

  Tin oxide has been generally used as a material for transparent conductive films, but since the thermal CVD method at 500 ° C. or higher is used, the material used for the light-transmitting substrate is limited and the formation conditions are adjusted. As a result, when the haze ratio is increased by increasing the interval between the convex and concave portions of the concave and convex portions, there is a problem that it becomes difficult to maintain Voc. Furthermore, since the light absorption loss of the material itself is large, if the sheet resistance is kept at a value of about 10 Ω / □, which is normally used, 500 to 800 nm which is an important absorption region of thin film amorphous silicon or crystalline silicon. The absorption loss is not negligible.

  In recent years, attention has been paid to a method using zinc oxide formed on a transparent conductive film by a thermal CVD method at about 200 ° C. for such a problem. Since the transparent conductive film made of zinc oxide is formed at a low temperature, there are advantages that the choice of materials that can be used for the light-transmitting substrate is widened and that Voc can be maintained even if the haze ratio is increased. This is considered to be due to the difference in surface shape from the transparent conductive film made of tin oxide. Further, there is an advantage that the light absorption loss of the material itself is small, and Jsc of the thin film photoelectric conversion device can be increased.

Non-patent document 1 describes that a film made of zinc oxide formed by a CVD method is used as a transparent conductive film of a thin film photoelectric conversion device. Specifically, a transparent conductive film made of zinc oxide to which boron is added is formed at 170 to 200 ° C., a transparent conductive film having a sheet resistance value of about 4Ω / □ is formed, and an amorphous silicon layer is formed thereon. A single photoelectric conversion device of amorphous silicon is obtained by high-frequency plasma CVD. Here, when the thickness of the i-type amorphous silicon layer is 0.35 μm, FF is 0.72 to 0.73, Jsc is 17.5 mA / cm ² , and conversion efficiency is 11.2%. Has been.
J. Meier et al., "Efficiency enhancement of amorphous silicon pin solar cells by LP-CVD ZnO", Proc. Of 28th IEEE Photovoltaic Specialists Conference, Anchorage, 2000, pp.746-749

  In view of the situation as described above, the present invention relates to a thin film photoelectric conversion device in which a silicon-based one-conductivity-type semiconductor layer is directly formed on a transparent conductive film containing zinc oxide as a main component. It is an object to obtain a method for manufacturing a thin film photoelectric conversion device that can be improved.

  In particular, when a transparent conductive film made of zinc oxide with low heat resistance formed by thermal CVD is used, the transparent conductive film is formed by forming a photoelectric conversion unit on the transparent conductive film without changing its resistivity. The present invention relates to a method of manufacturing a thin film photoelectric conversion device that can fully exhibit the potential of the film.

  The method for producing a thin film photoelectric conversion device according to the present invention comprises, in order, one or more units of photoelectric conversion including a transparent conductive film containing zinc oxide as a main component and at least a first photoelectric conversion unit on one main surface of a translucent substrate. A method of manufacturing a thin-film photoelectric conversion device comprising a unit and a back electrode layer, wherein the photoelectric conversion unit includes a one-conductivity-type semiconductor layer, a photoelectric-conversion layer, and another-conductivity-type semiconductor in order from the translucent substrate side. The first photoelectric conversion unit is formed directly on the transparent conductive film, and the one-conductivity-type semiconductor layer constituting the first photoelectric conversion unit is silicon-based. A step of forming the silicon-based one-conductivity type semiconductor layer on the transparent conductive film maintained at a temperature of 170 ° C. or lower, and a step of heating at an atmospheric pressure of 170 ° C. or higher after the formation of the back electrode layer. A method for manufacturing a thin film photoelectric conversion device comprising and. The formation temperature of the silicon-based one-conductivity-type semiconductor layer formed on the transparent conductive film is set to 170 ° C. or lower in order to prevent the resistance of the transparent conductive film from being increased by heating. In order to increase the activation rate of the dopant in the layer and to ensure ohmic contact between the transparent conductive film and the silicon-based one-conductivity-type semiconductor layer, and each junction interface between the other conductive-type semiconductor layer and the back-surface electrode layer, After the formation, heating is performed under atmospheric pressure at a temperature equal to or higher than the formation temperature of the silicon-based one conductivity type semiconductor layer. By these actions, a thin film photoelectric conversion device with improved photoelectric conversion characteristics can be manufactured.

  In addition, the method for manufacturing a thin film photoelectric conversion device according to the present invention preferably further includes a step of forming the transparent conductive film by a CVD method using a raw material gas containing at least zinc, boron, and oxygen as elements. This is because the effects of the present invention are particularly effective for zinc oxide formed by a CVD method using a source gas containing zinc, boron, and oxygen as elements.

  According to the present invention, even when a transparent conductive film made of zinc oxide having low heat resistance is used, the resistance change of the transparent conductive film can be suppressed, and the series resistance of the photoelectric conversion device can be kept small. As a result, a highly efficient thin film photoelectric conversion device can be provided at a low cost by a simple process.

It is a typical sectional view of a hybrid thin film photoelectric conversion device. It is a typical sectional view of an amorphous silicon single photoelectric conversion device. It is a depth direction profile of hydrogen, carbon, oxygen, and nitrogen concentration of the amorphous silicon single photoelectric conversion device produced on the conditions of Example 1. It is a depth direction profile of hydrogen, carbon, oxygen, and nitrogen concentration of the amorphous silicon single photoelectric conversion device produced on the conditions of Comparative Example 1. It is the depth direction profile of hydrogen, carbon, oxygen, and nitrogen concentration of the amorphous silicon single photoelectric conversion device produced on condition of a reference example. It is typical sectional drawing of an integrated hybrid thin film photoelectric conversion apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Translucent substrate 2 Transparent electrically conductive film 3 Amorphous photoelectric conversion unit 3p Amorphous p-type silicon carbide layer 3i Non-doped amorphous i-type silicon photoelectric conversion layer 3n N-type silicon layer 4 Crystalline photoelectric conversion unit 4p p-type Crystalline silicon layer 4i Crystalline i-type silicon photoelectric conversion layer 4n n-type crystalline silicon layer 5 Back electrode layer 5t Transparent reflection layer 2a Transparent electrode layer separation groove 4a Connection groove 5a Back electrode layer separation groove

  The present inventors actually formed a thin film photoelectric conversion device using a film made of zinc oxide formed by a CVD method as a transparent conductive film of the thin film photoelectric conversion device. As a result, the inventors have found that there are the following problems and have come to make the present invention.

  First, it has been found that a transparent conductive film using zinc oxide formed by thermal CVD has a problem of low heat resistance. Specifically, when the transparent conductive film is formed and left in the atmosphere for several months, the sheet resistance of the film increases by an order of magnitude or more. Further, when the transparent conductive film is annealed in the atmosphere at a temperature of about 200 ° C., the sheet resistance of the film similarly increases. Further, when a thin film photoelectric conversion device is formed on a transparent conductive film, the resistance of the transparent conductive film similarly increases, and the series resistance of the photoelectric conversion device increases.

  In order to solve such a problem, the present inventors diligently studied an optimum manufacturing condition of a photoelectric conversion device. As a result, a silicon-based one-conductivity-type semiconductor layer formed on the transparent conductive film is formed at a temperature of 170 ° C. or lower, and then a photoelectric conversion layer, another conductivity-type semiconductor layer, and a back electrode layer are formed. It has been found that the resistance of the transparent conductive film can be prevented from being increased by heating at the above atmospheric temperature under atmospheric pressure.

  The present invention can be applied to a transparent conductive film made of zinc oxide formed by any method such as a CVD method, a sputtering method, and a vapor deposition method. In particular, a source gas containing zinc, boron, and oxygen as elements is used. It is effective for zinc oxide formed by CVD method.

  In the present invention, it is possible to prevent the transparent conductive film made of zinc oxide from increasing in resistance by forming the silicon-based one-conductivity-type semiconductor layer directly formed on the transparent conductive film at a temperature of 170 ° C. or lower. Although this mechanism is not clear, the oxygen defect structure in the film is greatly involved in the conductivity of the zinc oxide film, and when this is heated in an oxygen atmosphere, it is slightly in the atmosphere even under reduced pressure. It is considered that oxygen contained in the film is taken into the film, oxygen vacancies serving as electron channels are reduced, and resistivity is increased. On the other hand, if the silicon-based one-conductivity type semiconductor layer is formed at a temperature of 170 ° C. or lower and the transparent conductive film is covered, oxygen atoms are taken into the transparent conductive film even after a temperature higher than the above temperature. There is nothing. It is considered that this makes it possible to prevent the transparent conductive film from increasing in resistance.

  On the other hand, at a formation temperature of 170 ° C. or lower, the activation rate of the dopant in the one-conductivity-type semiconductor layer containing silicon as a main component may not be sufficiently increased, and the transparent conductive film, the silicon-based one-conductivity-type semiconductor layer, etc. In some cases, each junction interface between the conductive semiconductor layer and the back electrode layer is not in ohmic contact. This problem is solved by performing a step of heating the photoelectric conversion device after forming the photoelectric conversion device, for example, after forming the back electrode layer, at the temperature of 170 ° C. or higher under atmospheric pressure.

  As the gas used in the heating atmosphere, air, nitrogen, a mixture of nitrogen and oxygen, or the like is preferably used. Moreover, the same effect is recognized not only in atmospheric pressure but also in some decompression or pressurization. Specifically, it has an effect in a range of at least 0.5 to 1.5 atmospheres.

  Hereinafter, a thin film photoelectric conversion device as an embodiment of the present invention will be described with reference to FIG. 1 and FIG.

A transparent conductive film 2 is formed on the translucent substrate 1. As the translucent substrate 1, a plate-like member or a sheet-like member made of glass, transparent resin or the like is used. When glass is used as the translucent substrate 1, it is desirable that the total iron oxide converted to Fe ₂ O ₃ contained in the glass be as small as possible in order to suppress a decrease in visible transmittance due to light irradiation. Specifically, it is preferably 0.02% by weight or less.

  Zinc oxide is used as the transparent conductive film 2. The transparent conductive film 2 is preferably formed using a method such as CVD, sputtering, or vapor deposition, and is particularly preferably formed by a CVD method at a formation temperature of about 200 ° C. Further, it is desirable to use boron as a doping material. The transparent conductive film 2 has the effect of increasing the scattering of incident light by producing fine irregularities on the surface by devising the formation conditions. The height difference of the unevenness is about 0.05 to 0.3 μm, and the sheet resistance is set to about 5 to 20Ω / □.

  One or more photoelectric conversion units are formed on the transparent conductive film 2 mainly composed of zinc oxide. The photoelectric conversion unit may be a single unit of an amorphous photoelectric conversion unit or a crystalline photoelectric conversion unit, or may be a hybrid type in which these are stacked. Further, three or more units of these may be laminated. As a material used for the photoelectric conversion unit, a silicon alloy such as silicon, silicon carbide, or silicon germanium, or a compound material such as copper-indium-selenium, gallium-arsenic, or the like is also preferably used.

  For example, when a single unit of an amorphous photoelectric conversion unit is used as the photoelectric conversion unit and silicon is used as the material, the configuration is as shown in FIG. That is, an amorphous photoelectric conversion unit comprising an amorphous p-type silicon carbide layer 3p, a non-doped amorphous i-type silicon photoelectric conversion layer 3i, and an n-type silicon layer 3n, which are one-conductivity type semiconductor layers, on the transparent conductive film 2. 3 is formed. The amorphous p-type silicon carbide layer 3p is formed at a substrate temperature of 170 ° C. or lower in order to prevent the resistance of the transparent conductive film 2 from being increased by heating.

On the other hand, for example, in a hybrid thin film photoelectric conversion device, a crystalline photoelectric conversion unit 4 is formed on an amorphous photoelectric conversion unit 3 as shown in FIG. The crystalline photoelectric conversion unit 4 includes a crystalline p-type silicon layer 4p, a crystalline i-type silicon photoelectric conversion layer 4i, and a crystalline n-type silicon layer 4n. A high frequency plasma CVD method is suitable for forming the amorphous photoelectric conversion unit 3 and the crystalline photoelectric conversion unit 4. As conditions for forming the photoelectric conversion unit, the substrate temperature is 100 to 250 ° C. (however, the amorphous p-type silicon carbide layer 3p is 170 ° C. or less), the pressure is 30 to 1500 Pa, and the high frequency power density is 0.01 to 0.5 W / cm. ² is preferably used. As a source gas used for forming the photoelectric conversion unit, a silicon-containing gas such as SiH ₄ or Si ₂ H ₆ or a mixture of these gases and hydrogen is used. B ₂ H ₆ or PH ₃ is preferably used as the dopant gas for forming the p-type or n-type layer in the photoelectric conversion unit.

  A back electrode layer 5 is formed on the n-type silicon layer 3n in FIG. 2 or the n-type silicon layer 4n in FIG. For the back electrode layer 5, Ag, Al, or an alloy thereof is preferably used. A transparent reflective layer 5t may be inserted between the back electrode layer 5 and the n-type silicon layer 4n in order to prevent metal diffusion from the back electrode layer 5 to the n-type silicon layer 4n. For the transparent reflective layer 5t, a metal oxide having high resistance and excellent transparency, such as ZnO or ITO, is used. In forming the transparent reflective layer 5t and the back electrode layer 5, methods such as sputtering and vapor deposition are preferably used.

  After the formation of the back electrode layer 5, as described above, the photoelectric conversion device is heated under atmospheric pressure at an atmospheric temperature equal to or higher than the formation temperature of the silicon-based one-conductivity-type semiconductor layer, for example, the amorphous p-type silicon carbide layer 3p. By doing so, it becomes a manufacturing method of the thin film photoelectric conversion device of the present invention.

  Below, the manufacturing method of the thin film photoelectric conversion apparatus by this invention is demonstrated, comparing Examples 1 and 2 with Comparative Examples 1-4, referring FIG. 2, FIG.

(Example 1)
FIG. 2 is a cross-sectional view schematically showing the amorphous silicon single photoelectric conversion device manufactured in Example 1.

First, the transparent conductive film 2 having a fine concavo-convex structure on the surface made of zinc oxide was formed on one main surface of the translucent substrate 1 made of 0.7 mm thick white glass by a thermal CVD method. As the formation conditions, the surface temperature of the substrate 1 was set to 160 to 180 ° C. and the pressure was set to 100 Pa, and diethyl zinc, water, B ₂ H ₆ , argon, and hydrogen were used as source gases. The obtained transparent conductive film 2 had a thickness of 1.5 μm, a haze ratio of 22%, and a sheet resistance of 10Ω / □.

  Next, in order to form the amorphous photoelectric conversion unit 3 as the first photoelectric conversion unit, the translucent substrate 1 on which the transparent conductive film 2 is formed is introduced into a high-frequency plasma CVD apparatus, and the surface temperature of the substrate 1 is determined. After heating to 170 ° C., an amorphous p-type silicon carbide (p-type a-SiC) layer (not shown) having a thickness of 20 mm as a silicon-based one-conductivity type semiconductor layer, a microcrystal having a thickness of 50 mm A p-type silicon layer (not shown) and a p-type a-SiC layer 3p having a thickness of 150 mm were sequentially formed. Subsequently, after the surface temperature of the substrate 1 is heated to a predetermined temperature, a non-doped amorphous i-type silicon photoelectric conversion layer 3i having a thickness of 3000 mm as a photoelectric conversion layer, and an n-type having a thickness of 150 mm as another conductive semiconductor layer are further formed. Silicon layers 3n were sequentially stacked.

At this time, the conditions for forming the p-type a-SiC layer 3p are: pressure 150 to 400 Pa, power density of high frequency power 0.02 to 0.05 W / cm ² , SiH ₄ : hydrogen: diluted to 0.1% with hydrogen. When the gas ratio of B ₂ H ₆ : CH ₄ is 1: 30: 10: 1.6 and the thickness of the layer reaches 80 mm, the discharge is maintained and the hydrogen is reduced to 0.1%. The supply of diluted B ₂ H ₆ and CH ₄ was stopped, and instead the gas ratio of hydrogen to SiH ₄ was increased from 30 to 40, and the remaining 70 mm of film was formed.

  Next, a transparent reflective layer 5t made of ZnO having a thickness of 900 mm and a back electrode layer 5 made of Ag having a thickness of 2000 mm were formed as a back electrode layer by a DC sputtering method. Further, by irradiating the YAG second harmonic pulse laser from the translucent substrate 1 side, only the transparent conductive film 2 is left, and the amorphous photoelectric conversion unit 3, the transparent reflective layer 5t, and the back electrode layer 5 are made wide. By removing in a 50 μm line, a 1 cm square island-shaped photoelectric conversion device region was formed.

  Then, the photoelectric conversion apparatus of Example 1 was produced by heat-processing in air | atmosphere for 90 minutes at the atmospheric temperature of 170 degreeC.

To the amorphous silicon single photoelectric conversion device manufactured in Example 1, pseudo-sunlight having a spectral distribution of AM1.5 and an energy density of 100 mW / cm ² is measured under a measurement atmosphere and a temperature of the photoelectric conversion device of 25 ± 1 ° C. The output characteristics of the thin film photoelectric conversion device were measured by irradiation. Voc, Jsc, F.M. F. Table 1 shows the measurement results of conversion efficiency (Eff.) And series resistance (Rs). In addition, when the pressure at the time of the previous heat treatment was changed in the range of 0.5 to 1.5 atmospheres, the obtained photoelectric conversion device characteristics were the same.

  Table 1 is a table comparing the photoelectric conversion characteristics of the amorphous silicon single photoelectric conversion devices manufactured under the conditions of Example 1, Comparative Examples 1 and 2 described later, and Reference Example.

(Comparative Example 1)
In Comparative Example 1, almost the same process as in Example 1 was performed, but the heat treatment was performed at an atmospheric temperature of 150 ° C. in the air after the back electrode layer 5 was formed. The measurement results are shown in Table 1.

(Comparative Example 2)
In Comparative Example 1, almost the same process as in Example 1 was performed, but the formation temperature of the p-type a-SiC layer 3p was 185 ° C., which was different from Example 1. Table 1 shows the measurement results.

  From the comparison between Example 1 and Comparative Example 1 in Table 1, the Eff. It can be seen that is improved by 0.3%. This is considered to be because the activation rate of the dopant of the p-type a-SiC layer was improved and the ohmic contact between the conductive semiconductor layer and the electrode was improved. Further, in Example 1, the sheet resistance of the transparent conductive film is a relatively high value of 10Ω / □, but the F. F. Is obtained, as described in F. of Non-Patent Document 1 shown above. F. It is also a large value compared to.

  On the other hand, from the comparison between Example 1 and Comparative Example 2, when the formation temperature of the p-type a-SiC layer is 185 ° C., the series resistance (Rs) of the photoelectric conversion device increases due to the high resistance of the transparent conductive film. , F. F. Decreases and Eff. The difference reaches 0.8%.

(Reference example)
In the reference example, substantially the same process as in Comparative Example 1 was performed. After the transparent electrode film 2 was formed, the translucent substrate 1 was once heat treated in the atmosphere at an atmospheric temperature of 200 ° C. for 90 minutes, and then the high frequency It was different from Comparative Example 1 in that it was introduced into the plasma CVD apparatus. Table 1 shows the measurement results. In this reference example, the resistivity of the zinc oxide film increased due to the influence of the heat treatment at 200 ° C. in the atmosphere, or oxygen atoms taken into the zinc oxide film by this treatment are converted into photoelectric conversion units, particularly The series resistance Rs is particularly large because of the diffusion to the p-type layer, which is lower than the photoelectric conversion characteristics Eff. It became.

Further, for each of the amorphous silicon single photoelectric conversion devices manufactured under the conditions of Example 1, Comparative Example 1, and Reference Example, SIMS was performed while performing ion sputtering from the back electrode layer 5 side toward the translucent substrate 1 side. The depth profiles of hydrogen, carbon, oxygen and nitrogen concentrations were measured. The measurement results of Example 1, Comparative Example 1, and Reference Example are shown in FIG. 3, FIG. 4, and FIG. 5, respectively. In each figure, the horizontal axis of 0.6 μm corresponds to the interface between the a-SiC that is the p-type layer and the a-Si layer that is the i-type layer of the photoelectric conversion layer. Although it is not an average value, the oxygen amount at that point is about 10 ²¹ atoms / cc in Example 1 and Comparative Example 1 as shown by the horizontal line in each figure, whereas it is 10 ^{22 in the} reference example. The reference example was several times higher at about atoms / cc, and the results supporting the above estimation were obtained.

(Example 2)
6 is a cross-sectional view schematically showing the integrated hybrid thin film photoelectric conversion device manufactured in Example 2. FIG.

First, a transparent conductive film 2 having a fine concavo-convex structure on a surface made of zinc oxide was formed on one main surface of a translucent substrate 1 made of white glass having a thickness of 910 mm × 455 mm × 4 mm by a thermal CVD method. As the formation conditions, the surface temperature of the translucent substrate 1 was set to 150 to 180 ° C. and the pressure was 100 Pa, and diethyl zinc, water, B ₂ H ₆ , argon, and hydrogen were used as source gases. The obtained transparent conductive film 2 had a thickness of 1.7 μm, a haze ratio of 25%, and a sheet resistance of 9.5Ω / □. Next, a transparent electrode layer separation groove 2a having a width of 50 μm is formed by irradiating the translucent substrate 1 with a YAG fundamental wave pulse laser in order to divide the transparent electrode layer 2 into a plurality of strip patterns. Ultrasonic cleaning and drying were performed.

  Next, in order to form the amorphous photoelectric conversion unit 3 as the first photoelectric conversion unit, the translucent substrate 1 on which the transparent conductive film 2 is formed is introduced into a high-frequency plasma CVD apparatus, and the surface of the substrate 1 is After heating to a temperature of 165 ° C., an amorphous p-type silicon carbide (p-type a-SiC) layer (not shown) having a thickness of 20 mm as a silicon-based one-conductivity type semiconductor layer, A crystalline p-type silicon layer (not shown) and a p-type a-SiC layer 3p having a thickness of 150 mm were sequentially formed. Subsequently, after the surface temperature of the substrate 1 is heated to a predetermined temperature, a non-doped amorphous i-type silicon photoelectric conversion layer 3i having a thickness of 3000 mm as a photoelectric conversion layer, and an n-type having a thickness of 300 mm as another conductive semiconductor layer. Silicon layers 3n were sequentially stacked.

At this time, the conditions for forming the p-type a-SiC layer 3p are as follows: the pressure is 120 to 200 Pa, the power density of the high frequency power is 0.01 to 0.02 W / cm ² , and SiH ₄ is diluted to 0.1% with hydrogen: hydrogen. When the gas ratio of B ₂ H ₆ : CH ₄ is 1: 11: 1.6: 1.8 and the thickness of the layer reaches 80 mm, the discharge is maintained and 0.1 The supply of B ₂ H ₆ and CH ₄ diluted to% was stopped, and the remaining 70 mm of film was formed.

  Further, in order to form the crystalline photoelectric conversion unit 4 as the second photoelectric conversion unit, a p-type crystalline silicon layer 4p having a thickness of 150 mm as a one-conductivity-type semiconductor layer is continuously used using a plasma CVD apparatus, a photoelectric conversion layer In this case, a crystalline i-type silicon photoelectric conversion layer 4i having a thickness of 1.5 μm and an n-type crystalline silicon layer 4n having a thickness of 100 mm are sequentially stacked as another conductive semiconductor layer.

  Thereafter, in order to divide the amorphous photoelectric conversion unit 3 and the crystalline photoelectric conversion unit 4 into a plurality of strip patterns, a YAG second harmonic pulse laser is irradiated from the translucent substrate 1 side to connect 60 μm in width. A groove 4a was formed.

  Next, a transparent reflecting layer (not shown) made of ZnO with a thickness of 900 mm and a back electrode layer 5 made of Ag with a thickness of 2000 mm were formed as a back electrode layer by DC sputtering. Further, in order to divide the amorphous photoelectric conversion unit 3, the crystalline photoelectric conversion unit 4, and the back electrode layer 5 into a plurality of strip patterns, YAG second harmonic pulse laser is irradiated from the translucent substrate 1 side. Thus, an integrated hybrid thin film photoelectric conversion device in which a back electrode layer separation groove 5a having a width of 60 μm is formed and strip-like hybrid photoelectric conversion devices adjacent to the left and right as shown in FIG. 3 are electrically connected in series is manufactured. did. In this integrated hybrid thin film photoelectric conversion device, 100 stages of hybrid photoelectric conversion devices each having a width of 8.9 mm and a length of 430 mm are connected.

  Finally, the photoelectric conversion device of Example 2 was fabricated by heat-treating the photoelectric conversion device in the atmosphere at an atmospheric temperature of 190 ° C. for 60 minutes.

The integrated hybrid thin film photoelectric conversion device manufactured in Example 2 was irradiated with pseudo-sunlight having a spectral distribution of AM1.5 and an energy density of 100 mW / cm ² under a measurement atmosphere and a temperature of the photoelectric conversion device of 25 ± 1 ° C. The output characteristics of the thin film photoelectric conversion device were measured. Voc, Jsc, F.M. F. Eff. The measurement results are shown in Table 2. In Table 2, Voc is obtained by dividing the actually obtained value by the number of series stages (100), and Jsc is obtained by dividing the actually obtained short-circuit current value by the area of one stage of the photoelectric conversion device. .

  Table 2 is a table comparing the photoelectric conversion characteristics of the hybrid thin film photoelectric conversion devices manufactured under the conditions of Example 2 and Comparative Examples 3 and 4 described later.

(Comparative Example 3)
In Comparative Example 3, almost the same process as in Example 2 was performed, but the heat treatment was performed at 150 ° C. in the air after the back electrode layer 5 was formed, which was different from Example 1. The measurement results are shown in Table 2.

(Comparative Example 4)
In Comparative Example 4, almost the same process as in Example 2 was performed, but the formation temperature of the p-type a-SiC layer 3p was 180 ° C., which was different from Example 2. The measurement results are shown in Table 2.

  From the comparison between Example 2 and Comparative Examples 3 and 4 in Table 2, the same results as those obtained by comparing Example 1 and Comparative Examples 1 and 2 can be seen.

  From the above, according to the method for manufacturing a thin film photoelectric conversion device of the present invention, even when a transparent conductive film made of zinc oxide having low heat resistance is used, the resistivity thereof is not changed. Improve the dopant activation rate of the directly formed silicon-based one-conductivity-type semiconductor layer, and ensure the bonding interface between the transparent conductive film and the silicon-based one-conductivity-type semiconductor layer, the other-conductivity-type semiconductor layer, and the back electrode layer It can be ohmic contact. As a result, a thin film photoelectric conversion device exhibiting high performance can be provided at low cost.

Claims (2)

A thin film photoelectric device comprising a transparent conductive film containing zinc oxide as a main component, at least one photoelectric conversion unit including at least a first photoelectric conversion unit, and a back electrode layer in order on one main surface of the translucent substrate. A method for manufacturing a conversion device, comprising:
The photoelectric conversion unit is composed of one conductive semiconductor layer, a photoelectric conversion layer, and another conductive semiconductor layer in order from the translucent substrate side.
And the first photoelectric conversion unit is directly formed on the transparent conductive film,
And the one conductivity type semiconductor layer constituting the first photoelectric conversion unit is silicon-based,
Forming the silicon-based one conductivity type semiconductor layer on the transparent conductive film maintained at a temperature of 170 ° C. or lower;
And a method of manufacturing the thin film photoelectric conversion device, comprising a step of heating under an atmospheric pressure of 170 ° C. or higher after the back electrode layer is formed.   2. The method of manufacturing a thin film photoelectric conversion device according to claim 1, further comprising a step of forming the transparent conductive film by a CVD method using a source gas containing at least zinc, boron, and oxygen as elements. A method for manufacturing a thin film photoelectric conversion device.

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