WO2003073515A1

WO2003073515A1 - Thin-film solar cell and its production method

Info

Publication number: WO2003073515A1
Application number: PCT/JP2003/001999
Authority: WO
Inventors: Hiroshi Yamamoto; Yoshiyuki Nasuno; Takashi Hayakawa; Akihisa Matsuda; Michio Kondou
Original assignee: National Institute Of Advanced Industrial Science And Technology; Sharp Kabushiki Kaisha
Priority date: 2002-02-28
Filing date: 2003-02-24
Publication date: 2003-09-04
Also published as: JP3943080B2; AU2003211649A1; JPWO2003073515A1

Abstract

A thin-film solar cell (20) comprises an i-type microcrystalline silicon layer (13) that is formed in the production process under the condition that the oxygen concentration in the i-type microcrystalline silicon layer (13) is 4 × 1018 cm-3 and under the condition satisfying the following relation (1) 700 ≤ Tsub × Ic/Ia ≤ 1600 (1) where Ic is the peak intensity of a signal attributed to the crystal component, Ia is the peak intensity of a sign attributed to the amorphous component, and Tsub is the substrate temperature when they are measured by a Raman scattering measuring method. By specifying the best suited formation conditions of the oxygen concentration, substrate temperature, and crystallinity in the silicon layer when the i-type silicon layer is formed, a thin-film solar cell having a high photoelectric conversion efficiency and its production method can be provided.

Description

Thin film solar cell and manufacturing method thereof

TECHNICAL FIELD The present invention relates to a microcrystalline silicon-based thin film solar cell and a method for manufacturing the same.

In particular, the present invention relates to a thin film solar cell having high photoelectric conversion efficiency and a method for manufacturing the same. Rice field

BACKGROUND ART At present, fossil fuels such as oil, which are used as a major energy source, have a problem of carbon dioxide emission, which is concerned about future supply and demand and causes global warming. Therefore, solar cells are attracting attention as an energy source that can replace fossil fuels such as petroleum. A solar cell uses a pn junction as a semiconductor photoelectric conversion layer that converts light energy into electric power, and silicon is generally used as a semiconductor material constituting the pn junction. In the thin film solar cell using silicon, it is preferable to use single crystal silicon in terms of photoelectric conversion efficiency. However, in order to realize a larger area and a lower cost, an amorphous silicon material is photoelectrically used. Some thin-film solar cells as conversion layers have also been put into practical use. On the other hand, thin film solar cells using microcrystalline silicon materials as photoelectric conversion layers have been studied for further stabilization of characteristics and higher efficiency. This microcrystalline silicon, like amorphous silicon, can be formed into a thin film by plasma CVD. As a general method for forming thin film silicon by plasma CVD method, there is a method using a source gas obtained by diluting silane gas with hydrogen 10 times or more. When deposited using this source gas, a microcrystalline silicon film can be obtained, and the crystallization rate can be increased by increasing the hydrogen dilution rate.

Note that the microcrystalline silicon film is a thin film composed of a mixture of crystalline silicon and amorphous silicon.

The photoelectric conversion efficiency of current microcrystalline silicon solar cells is lower than the photoelectric conversion efficiency of single-crystal silicon solar cells, about 20%, and about 10%. It is about 7-8%, which is equivalent to the photoelectric conversion efficiency of amorphous silicon solar cells.

In Japanese Patent Application Laid-Open No. 1 1-1 4 5 4 9 8 (release date 1 May 9 9 May 28), the substrate temperature at the time of film formation is set to 5500 ° C or less and the crystallization rate is A solar cell is disclosed in which a high photoelectric conversion efficiency can be obtained by setting 80% or more (I c / I a ≥4).

In T. Repmann et al. 28 ^th IEEE PVSC proceedings, 2000 P912-915, by forming a solar cell by changing the hydrogen dilution rate when forming the photoelectric conversion layer, a low hydrogen dilution rate, ie, a crystal A thin-film solar cell has been reported that can achieve high photoelectric conversion efficiency under conditions where a microcrystalline silicon layer with a low conversion rate is expected to be formed.

Is found in, J. Meier et al. MRS Symp . Proc. Vol. 420, pp.3-14, in 1996, the oxygen concentration in the i-type microcrystalline silicon layer is 2 X ¹ 0 1 ⁸ cm one ³ From the above, it has been reported that when the substrate temperature is increased to 200 ° C or higher, the i-type microcrystalline silicon layer is activated to become n-type, and the characteristics of the thin-film solar cell deteriorate. Has been.

However, the conventional thin film solar cells disclosed in the above publications and literatures have only revealed a partial relationship such as the relationship between the substrate temperature and the crystallization rate, or the hydrogen dilution rate and the crystallization rate. However, a microcrystalline silicon-based thin-film solar cell and an optimum manufacturing method thereof have not yet reached a practical level.

In other words, although it has been experimentally shown that the hydrogen conversion rate suitable for film formation exists in the photoelectric conversion layer of the microcrystalline silicon thin film solar cell, the film formation conditions such as the substrate temperature and the optimum hydrogen The dilution rate will vary depending on the deposition equipment. Therefore, as a method for producing a thin-film solar cell having high photoelectric conversion efficiency, the optimum formation conditions with universality have not been clarified yet. The present invention has been made in view of the above problems. The purpose is to have high photoelectric conversion efficiency by identifying the optimum formation conditions with respect to the oxygen concentration in the silicon layer, the substrate temperature, the crystallization rate, etc. when forming the i-type silicon layer. . To provide a thin film solar cell and a method of manufacturing the same

Disclosure of the invention

In order to solve the above-described problem, a method for manufacturing a thin-film solar cell according to the present invention includes a photoelectric conversion unit on a substrate, and the thin-film solar cell that converts incident light into electrical energy in the photoelectric conversion unit. In the manufacturing method, an i-type semiconductor layer included in at least one layer in the photoelectric conversion portion is subjected to Raman scattering under a condition where the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm _ ³ or less. By measurement When the peak intensity of the signal due to the crystal component of the i-type semiconductor layer is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature at the time of manufacturing the i-type semiconductor layer is T sub, It is characterized by being formed under the formation conditions satisfying the relational expression 7 0 0 ≤ T sub XI c / I a ≤ 1 6 0 0 (1).

According to the above manufacturing method, a thin-film solar cell having high photoelectric conversion efficiency can be manufactured under the formation conditions where the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm ⁻³ or less.

That is, when the product of the substrate temperature T sub and the crystallization rate I c / I a is smaller than 700, the substrate temperature or the crystallization rate is low, and under such formation conditions, The photoelectric conversion efficiency will decrease.

On the other hand, when the product of the substrate temperature T sub and the crystallization rate I c / I a is larger than 1600, the substrate temperature and / or the crystallization rate is increased. When the substrate temperature rises, oxygen in the i-type silicon layer is activated and the i-type semiconductor layer becomes n-type, and hydrogen is desorbed and defects are increased. The photoelectric conversion efficiency will decrease.

Therefore, according to the method for manufacturing a thin-film solar cell of the present invention, the above relational expression (1) is satisfied under the formation conditions in which the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm− ³ or less. By forming the i-type semiconductor layer by changing the crystallization rate in accordance with the formation conditions, i.e., the substrate temperature, the above-described problem of a decrease in photoelectric conversion efficiency can be achieved regardless of the substrate temperature. It is possible to produce a thin film solar cell that can prevent generation and obtain high photoelectric conversion efficiency. In the Raman scattering measurement used to determine the crystallization rate, the silicon layer was irradiated with an argon ion laser (5 14.5 nm) at about 10 mW, and the Raman scattering spectrum was measured. In this measurement method, the crystallization rate can be evaluated by obtaining the peak intensity ratio I c / I a from the peak intensities I c and I a obtained by the measurement.

In order to solve the above-described problem, a method for manufacturing a thin-film solar cell according to the present invention includes a photoelectric conversion unit on a substrate, and the thin-film solar cell that converts incident light into electrical energy in the photoelectric conversion unit. In the manufacturing method, the i-type semiconductor layer included in at least one layer in the photoelectric conversion portion is subjected to Raman scattering measurement under the formation conditions where the substrate temperature of the substrate is 25 ° C. or lower. Where I c is the peak intensity of the signal due to the crystalline component, I a is the peak intensity of the signal due to the amorphous component, and T sub is the substrate temperature at the time of fabrication of the i-type semiconductor layer. ≤ T sub XI c / I a ≤ 1 6 0 0

It is characterized by being formed under conditions that satisfy (1).

According to the above manufacturing method, a thin-film solar cell having high photoelectric conversion efficiency can be manufactured under a forming condition of a substrate temperature of 2550 ° C. or lower, that is, formed by a plasma CVD method or the like. In the i-type semiconductor layer, the crystal grain size increases as the substrate temperature rises, and the quality of the crystal part improves. However, when the substrate temperature rises, oxygen contained in the i-type semiconductor layer is activated and the i-type semiconductor layer becomes _n- type, and hydrogen is desorbed and defects increase.

The photoelectric conversion efficiency of thin-film solar cells will decrease.

Therefore, in the method for manufacturing a thin-film solar cell of the present invention, the substrate temperature is 2500 ° C. Under the following formation conditions, high photoelectric conversion efficiency can be achieved by forming the i-type semiconductor layer under the formation conditions that satisfy the above relational expression (1) without accompanying the above-described decrease in photoelectric conversion efficiency. It is possible to manufacture a thin film solar cell.

The thin-film solar cell manufactured by the above-described method for manufacturing a thin-film solar cell, wherein the crystallization rate is high when forming the film on an amorphous substrate in the initial stage of forming the i-type semiconductor layer. More preferably, the i-type semiconductor layer is formed, and the crystallization rate satisfies the relational expression (1) in the entire region in the film thickness direction.

Thereby, the above-mentioned relational expression (1) can be satisfied in the entire region in the thickness direction of the i-type semiconductor layer, and a thin-film solar cell free from bias of the internal electric field in the thickness direction can be manufactured.

That is, in general, when a microcrystalline silicon layer is formed on an amorphous substrate, the crystallization rate tends to increase as the film thickness increases, so a semiconductor layer with a very thin film thickness is formed. In this case, the increase in the crystallization rate does not reach the saturation state, and the crystallization rate becomes low at the initial stage of film formation in the i-type semiconductor layer.

Therefore, in the method for manufacturing a thin-film solar cell of the present embodiment, in the initial stage of film formation of the i-type semiconductor layer, for example, the conditions for increasing the crystallization rate are, for example, the conditions for a high hydrogen dilution rate and the high input power. It is possible to prevent the crystallization rate from being lowered in the portion formed in the initial stage of film formation by forming the film according to the conditions, etc., and appropriately changing the film formation conditions as the film thickness increases.

In order to solve the above problems, the thin film solar cell of the present invention is a thin film solar cell manufactured by the method for manufacturing a thin film solar cell, wherein the i-type half-cell Integrated intensity of the (2 2 0) X-ray diffraction peak of the conductor layer I _{2 2} . , (1 1 1) X-ray diffraction peak integrated intensity I i 、、, these ratios I _{2 2} . / I i is the relation I _{2 2} . It is characterized by satisfying / I i ≥ 5 (2).

According to said structure, the thin film solar cell which has a stably high photoelectric conversion efficiency is specified by specifying the formation conditions according to the oxygen concentration in the said i-type semiconductor layer, a substrate temperature, a crystallization rate, etc. The thin-film solar battery of the present invention that can be manufactured and can obtain a thin-film solar battery with high photoelectric conversion efficiency more reliably among the thin-film solar batteries, In a thin-film solar cell that has a photoelectric conversion unit and converts incident light into electrical energy in the photoelectric conversion unit, an i-type semiconductor layer included in the photoelectric conversion unit is included in the i-type semiconductor layer. Under conditions where the oxygen concentration is 4 XI 0 ¹⁸ cm ^{3 or} less, the peak intensity of the signal due to the crystalline component of the i-type semiconductor layer is determined by Raman scattering measurement as I c, and the peak intensity of the signal due to the amorphous component I a, the i When the substrate temperature at the time of fabrication of the type semiconductor layer is T sub, it is formed under the formation conditions satisfying the following relational expression (1)

. 7 0 0 ≤ T s u b X I c Z l a ^ l 6 0 0 (1)

According to the arrangement, it is the oxygen concentration in the i-type semiconductor layer is in ^{4 X 1 0 1 8 c πι-} 3 following formation conditions, to provide a thin film solar cell having high photoelectric conversion efficiency.

That is, when the product of the substrate temperature T sub and the crystallization rate I c Z la is smaller than 700, the substrate temperature or the crystallization rate is low. Under such conditions, A photoelectric conversion efficiency will fall. On the other hand, when the product of the substrate temperature T sub and the crystallization rate I c / I a is larger than 1600, the substrate temperature and Z or the crystallization rate are increased. In particular, when the substrate temperature rises, oxygen in the i-type silicon layer is activated and the i-type semiconductor layer becomes n-type, and hydrogen is desorbed and defects are increased. The photoelectric conversion efficiency will decrease.

Therefore, the thin film solar cell of the present invention has a formation condition that satisfies the above relational expression (1) under the formation condition where the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm− ³ or less, In other words, by forming the i-type semiconductor layer by changing the crystallization rate in accordance with the substrate temperature, it is possible to prevent the occurrence of the above-described problem of a decrease in photoelectric conversion efficiency regardless of the substrate temperature. Thus, it is possible to provide a thin film solar cell that can obtain high photoelectric conversion efficiency.

In order to solve the above problems, the thin film solar cell of the present invention has a photoelectric conversion unit on a substrate, and the photoelectric conversion unit converts incident light into electric energy in the photoelectric conversion unit. At least one i-type semiconductor layer is included under the conditions where the substrate temperature of the substrate is 25 ° C. or lower.

The peak intensity of the signal due to the crystalline component of the i-type semiconductor layer measured by Raman scattering is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature at the time of fabrication of the i-type semiconductor layer is T sub Then, it is formed under the formation conditions that satisfy the following relational expression (1). 7 0 0≤ T s u b X

I c / I a ≤ 1 6 0 0 (1)

According to said structure, the thin film solar cell which has high photoelectric conversion efficiency can be provided on the formation conditions whose board | substrate temperature is 2550 degrees C or less. In other words, an i-type semiconductor layer formed by a plasma CVD method or the like increases the crystal grain size and improves the quality of the crystal part when the substrate temperature rises. However, when the substrate temperature rises, oxygen contained in the i-type semiconductor layer is activated and the i-type semiconductor layer becomes n-type, and hydrogen is desorbed and defects are increased. Efficiency will decrease.

Therefore, in the method for producing a thin-film solar cell of the present invention, the above relational expression (1) can be obtained without causing a decrease in the photoelectric conversion efficiency as described above under the formation conditions where the substrate temperature is 2550 ° C. or less. By forming the i-type semiconductor layer under satisfying formation conditions, a thin film solar cell having high photoelectric conversion efficiency can be provided.

In the above thin film solar cell, it is more preferable that the crystallization rate satisfies the relational expression (1) in the entire region in the film thickness direction of the i-type semiconductor layer.

That is, in general, when a microcrystalline silicon layer is formed on an amorphous substrate, the crystallization rate tends to increase as the film thickness increases, so a semiconductor layer with a very thin film thickness is formed. In this case, the increase in the crystallization rate does not reach the saturation state, and the crystallization rate is lowered at the initial stage of film formation in the i-type semiconductor layer.

Therefore, in the method for manufacturing a thin-film solar cell according to the present embodiment, in the initial stage of forming the i-type semiconductor layer, the conditions for increasing the crystallization rate are, for example, the conditions for a high hydrogen dilution rate and the high input power. In the part formed in the initial stage of film formation, the film is formed according to the conditions, etc. It is possible to prevent the crystallization rate from being lowered.

The thin-film solar cell, wherein the integrated intensity I ₂₂ of the (2 2 0) X-ray diffraction peak of the i-type semiconductor layer. (1 1 1) If the integrated intensity of the X-ray diffraction peak is I I, these ratios are I ₂₂ . More preferably, ZI satisfies the following relational expression (2). I s soZ liii ^ S (2) By this, by specifying the formation conditions according to the oxygen concentration, substrate temperature, crystallization rate, etc. in the i-type semiconductor layer, stable and high photoelectric conversion efficiency can be achieved. A thin film solar cell having high photoelectric conversion efficiency can be obtained more reliably among the above thin film solar cells.

In the case of a single-junction thin film solar cell, it is more preferable that the photoelectric conversion layer includes a layer containing microcrystalline silicon.

In the case of a multi-junction thin film solar cell, it is more preferable that a layer containing microcrystalline silicon and a layer containing amorphous silicon are mixed.

Thereby, the photoelectric conversion efficiency can be increased.

Other objects, features and advantages of the present invention will be fully understood from the following description. The benefits of the present invention will become apparent from the following description with reference to the accompanying drawings. Brief Description of Drawings

FIG. 1 is a cross-sectional view showing the structure of a microcrystalline silicon-based thin film solar cell according to an embodiment of the present invention.

FIG. 2 is a graph showing the crystallization rate dependency of the photoelectric conversion rate when the oxygen concentration in the i-type microcrystalline silicon layer is low.

Figure 3 shows the photoelectric at high oxygen concentration in the i-type microcrystalline silicon layer. It is a graph which shows the crystallization rate dependence of conversion efficiency.

Fig. 4 is a graph showing the change in crystallization rate in the thickness direction of a microcrystalline silicon thin film solar cell fabricated on a glass substrate.

FIG. 5 is a flow chart showing the manufacturing process of the microcrystalline silicon solar cell of the present invention. Best Mode for Carrying Out the Invention

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these.

One embodiment of the thin film solar cell and the method for producing the same of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the thin film solar cell 20 of the present embodiment is a thin film solar cell 20 having a super-straight structure that performs photoelectric conversion by light incident from the substrate 11a side. A battery substrate (substrate) 1 1, a photoelectric conversion layer 1 7, and a back electrode 16 are provided on the solar cell substrate 1 1. A back surface reflective layer 15 may be provided between the photoelectric conversion layer 17 and the back electrode 16. Alternatively, a substrate type structure in which a back electrode, a photoelectric conversion layer, a light receiving surface electrode, and a collecting electrode are sequentially laminated on a substrate may be used. The solar cell substrate 11 includes a substrate 11a and a transparent conductive layer 11b formed on the substrate 11a.

The substrate 11a is formed with a thickness of about 0.1 to 30 mm, for example, with appropriate strength and weight. In addition, the substrate 11 a may have irregularities formed on the surface according to the usage mode of the substrate, and may further include an insulating film, a conductive film, a buffer layer, or the like, or these The composite layer which combined these may be laminated | stacked.

The substrate of the thin film solar cell of the present invention is not particularly limited as long as it supports and reinforces the entire solar cell, but has a heat resistance of about 200 ° C., for example. Alternatively, those that can be used for super-straight type solar cells are preferable. For example, glass, polyimide, Ρ Ε Τ, PEN * PES 'heat-resistant polymer film such as Teflon (registered trademark), stainless steel (SUS), aluminum and other metals, ceramics, etc. Can be used in a stacked manner.

The transparent conductive layer l i b is 0. I n n! In order to improve plasma resistance, it is more preferable to have a layer containing zinc oxide (ZnO) at least on the surface. The transparent conductive layer 1 1 b is formed by a sputtering method in order to easily control the transmittance and resistivity.

Further, the transparent conductive layer 11 b may contain impurities in order to reduce the resistivity. As this impurity, there is a group III element such as gallium or aluminum, and its concentration is, for example, 5 X 10 ² . ~ 5 X 1 0 ^{2 1} / cm ³

In the present embodiment, the example in which zinc oxide (ZnO) is used as the transparent conductive layer 11b has been described. However, the present invention is not limited to this. For example, it is also possible to form the S N_〇 _2, I n ₂ 〇 _3, a single layer such as a transparent conductive material such as ITO or a composite layer thereof.

Furthermore, in the present embodiment, the example in which the transparent conductive layer 1 1 b is formed by the sputtering method has been described, but the present invention is not limited to this. For example, instead of the sputtering method, vacuum deposition method, EB deposition method, atmospheric pressure C VD method, reduced pressure C It can be formed using a VD method, a sol-gel method, an electrodeposition method, or the like.

Photoelectric conversion layer 17 consists of p-type microcrystalline silicon layer 1 2, i-type microcrystalline silicon layer 1 3, and n-type microcrystalline silicon layer 1 4 formed by plasma CVD for solar cells. It is configured by laminating on the substrate 11 in this order. The photoelectric conversion layer 17 is usually formed by such a pin junction, and may be a layer containing microcrystalline silicon or a layer containing amorphous silicon.

In particular, in a multi-junction thin film solar cell having a plurality of pin junctions, for example, a layer containing microcrystalline silicon and a layer containing amorphous silicon may be stacked, and all photoelectric conversions The element does not have to be a layer containing microcrystalline silicon or a layer containing amorphous silicon.

However, in the single-junction thin-film solar cell 20 shown in FIG. 1 like the thin-film solar cell 20 of this embodiment, the photoelectric conversion layer 17 includes microcrystalline silicon from the viewpoint of photoelectric conversion efficiency and the like. Preferably it comprises a layer. In a multi-junction thin film solar cell, a layer containing microcrystalline silicon and a layer containing amorphous silicon are preferably mixed from the viewpoint of photoelectric conversion efficiency and the like.

Further, all of the pin junction p-type microcrystalline silicon layer 12, i-type microcrystalline silicon layer 13, and n-type microcrystalline silicon layer 14 constituting the photoelectric conversion layer 17 are micro It is made of crystalline silicon. However, the present invention is not limited to this, and the transparent conductive layer of the p-type microcrystalline silicon layer 12, the i-type microcrystalline silicon layer 13, and the n-type microcrystalline silicon layer 14 is used. Only the silicon layer in contact with the layer 1 1 b may be microcrystalline silicon.

Microcrystalline silicon also includes alloyed silicon, for example, Si XC _χ _ _{χ with} carbon added, Si XG _ei — _{x with} germanium added, Or silicon with other impurities added is included.

The P-type microcrystalline silicon layer 12 is a layer containing a group III element such as boron, aluminum, germanium, indium, titanium, etc., and the group III element concentration is 0.01 to 8 atomic%. The layer thickness is about 1 to 200 nm. The p-type microcrystalline silicon layer 12 may be a single layer, or may be formed of a composite layer composed of a plurality of layers having different I I I group element concentrations or gradually changing.

In addition, the p-type microcrystalline silicon layer 1 2 is formed by forming the p-type microcrystalline silicon layer 1 2 with the C VD method using the RF to UHF frequency band, the ECR plasma C VD method, or these It is formed using the C VD method combining the above. For example, when using the plasma C VD method, the conditions are as follows: frequency about 10 to 200 MHz, power number W to about several kW, chamber internal pressure about 0.1 to 20 Torr, The substrate temperature is from room temperature to about 600 ° C., etc. In this embodiment, the formation of the p-type microcrystalline silicon layer 12 is made from RF.

Although an example of formation using a CVD method using a high frequency in the UHF frequency band, an ECR plasma CVD method, or a CVD method combining these has been described, the present invention is not limited to this. Any method can be used as long as the silicon layer can be formed to have a p-type conductivity. For example, the formation of the silicon layer can be performed by normal pressure C VD, reduced pressure C VD, plasma C VD, ECR plasma CVD, high temperature C VD, low temperature C VD, microwave C VD, catalyst C VD, sputtering method, etc. Any of these may be used.

The silicon-containing gas used at this time is, for example, SiH ₄ , _Examples include Si _{2 He} , Si F ₄ , Si H ₂ Cl ₂ , and Si Cl ₄ , which are used together with H ₂ gas as a dilution gas. The mixing ratio of the silicon-containing gas and the dilution gas may be constant or may be formed while being changed. For example, the volume ratio is about 1: 1 to 1: 100. The doping gas is a gas that optionally contains a group III element. For example, B ₂ H ₆ or the like can be used.

Furthermore, the mixing ratio between the silicon-containing gas and the group III element-containing gas is appropriately adjusted according to the size of the film forming apparatus such as CVD and the concentration of the group III element to be obtained. It may be constant or may be formed while being changed. For example, the capacity ratio may be about 1: 0.0 0 1 to 1: 1. The group III element may be doped at the same time as the formation of the microcrystalline silicon layer. However, after the silicon film is formed, ion implantation, surface treatment of the microcrystalline silicon layer, or solid layer diffusion is performed. May be used. In addition, fluorine gas such as F ₂ , Si F ₄ , Si H ₂ F _2, etc. may be optionally added to the silicon-containing gas. The amount of fluorine gas in this case is, for example, H 2 used as a dilution gas for the silicon-containing gas.

It may be about 0.0 1 to 10 times that of the _two gases.

The silicon-containing gas used at this time is not limited to H ₂ gas.

An inert gas such as A r, He, N e, and X e can be used as a dilution gas.

The i-type microcrystalline silicon layer 13 is made of microcrystalline silicon, and its film thickness is about 0.1 to 10 μππι. Moreover, i-type microcrystalline silicon layer 1 3, during formation, except not using a gas containing a Group III element, in the same manner as P-type microcrystalline silicon layer 1 2, for example, S i H ₄ and It can be formed by decomposing H ₂ gas mixture by plasma CVD. The i-type microcrystalline silicon layer 13 is an intrinsic semiconductor that does not exhibit p-type and n-type conductivity, but has a very weak p-type or n-type conductivity as long as the photoelectric conversion function is not impaired. It may be shown.

The formation conditions of this i-type microcrystalline silicon layer 13 will be described in detail later.

The n-type microcrystalline silicon layer 14 is an n-type conductivity type silicon layer having a thickness of about 10 to 100 nm. The n-type microcrystalline silicon layer 14 is the above-described p-type microcrystalline silicon layer 12 and i-type except that a gas containing a group V element such as PH 3 is used as a dopant gas. It can be formed in the same manner as the microcrystalline silicon layer 1 3. Examples of the donor impurity include phosphorus, arsenic, and antimony, and the impurity concentration is about ^{10 18} to 10 ^{2 Q} cm ⁻³ .

Then, on the photoelectric conversion layer 17, a transparent conductive film made of Sn 0 ₂ , In _{2 2} 0 ₃ , Zn 0, IT 0, etc. is formed with a thickness of about 50 nm by a magnet opening sputtering method. The back reflective layer 15 is formed.

Finally, the back electrode 16 is made of a metal film using materials such as Ag, A1, Cu, Au, Ni, Cr, W, Ti, Pt, Fe, Mo, etc. A single layer or a plurality of metal films are stacked, and the thickness is 10 0 η π! ~ 1 μm.

The thin film solar cell 20 of the present embodiment constitutes a super straight type thin film solar cell 20 by drawing out the electrode 21 from the transparent conductive layer 11 b and the back electrode 16. With the configuration described above, incident light is converted into electrical energy using the light confinement effect in the photoelectric conversion layer 17. be able to.

Here, the formation conditions of the i-type microcrystalline silicon layer 13 which is the main part of the thin film solar cell 20 of the present invention will be described in more detail.

The thin-film solar cell 20 of the present embodiment changes the crystallization rate in accordance with the substrate temperature of the solar cell substrate 11 1 and the hydrogen dilution rate, and the optimum formation conditions for the i-type microcrystalline silicon layer 1 3 As a result of the examination, based on the experimental results described later in Examples 1 to 13 and Comparative Examples 1 to 6, the i-type microcrystalline silicon layer 13 was formed under the following forming conditions. It is formed.

As a result, a thin film solar cell with a relatively high photoelectric conversion efficiency can be obtained.

That is, in the method for manufacturing a thin-film solar cell of this embodiment, when the oxygen concentration contained in the i-type microcrystalline silicon layer 13 is about 2 to 4 X ^{10 18} cm− ³ , If the peak intensity of the signal due to the crystal component in the Raman scattering measurement method is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature is T sub, then the relation 7 0 0 ≤ T sub XI c / I a ≤

The i-type microcrystalline silicon layer 13 is formed under the formation conditions satisfying 1600 (1).

Thereby, a thin film solar cell having a relatively high photoelectric conversion efficiency can be obtained.

That is, i-type microcrystalline silicon layer formed by plasma C V D method

1 3 increases the crystallization rate as the substrate temperature rises. However, the photoelectric conversion efficiency of thin film solar cells does not necessarily improve. This is thought to be because oxygen contained in the i-type semiconductor layer is activated to make the i-type semiconductor layer n-type, and hydrogen is released to increase defects. Therefore, i-type fine at high temperatures In order to obtain high photoelectric conversion efficiency when forming the crystalline silicon layer 1 3, as shown in the graph of FIG. 2, the crystallization rate is lowered and the amorphous silicon is inserted into the grain boundaries. It is necessary to inactivate interface states and impurity levels.

In the thin-film solar cell manufacturing method of the present embodiment, the i-type microcrystalline silicon layer 13 is formed under the formation conditions satisfying the relational expression (1) above, so that it is possible to adapt to such conditions. And a thin film solar cell having high photoelectric conversion efficiency can be obtained.

On the other hand, in the method for manufacturing a thin-film solar cell of this embodiment, in addition to the case where the substrate temperature and the hydrogen dilution rate are changed as described above, the film forming apparatus is opened to the atmosphere, and the i-type microcrystalline silicon layer 13 is formed. When the oxygen concentration remaining in the deposition chamber due to the moisture adsorbed on the inner wall is increased to about 2 to 3 X 10 0 ¹⁹ cm _ ³ by changing the ultimate vacuum during film deposition In addition, the formation conditions of the i-type microcrystalline silicon layer 13 that can achieve high photoelectric conversion efficiency were investigated.

As a result, as shown in the graph of FIG. 3, compared with the graph of FIG. 2, even under the formation conditions where the oxygen concentration is likely to decrease, the substrate temperature is 2550 ° C. or lower. By forming a thin film solar cell under the formation conditions that satisfy the above relational expression (1), a thin film solar cell with high photoelectric conversion efficiency can be produced in the same manner.

As described above, in the method for manufacturing a thin-film solar cell of this embodiment, when the oxygen concentration is 4 × ^{10 18} cm− ³ or less, or when the substrate temperature is 200 ° C. or less. By forming the i-type microcrystalline silicon layer 13 under the formation conditions that satisfy the above relational expression (1), it has a relatively high photoelectric conversion efficiency. A thin film solar cell can be provided.

The Raman scattering measurement used to determine the crystallization rate was performed by irradiating the silicon layer with an argon ion laser (5 14.5 nm) at about 10 mW and applying the Raman scattering spectrum. This is a measurement method in which the peak intensities I c and I a are obtained by measurement. In this Raman scattering spectrum, the peak intensity I c of the signal due to the crystal component appears at a position centered at about 5 20 cm- ¹ , and the peak intensity I a of the signal due to the amorphous component is Appears at a position centered on approximately 4 80 cm— ¹ . Therefore, the crystallization rate can be evaluated by obtaining the peak intensity ratio I c / I a.

Incidentally, it is generally known that when a microcrystalline silicon layer is formed on an amorphous substrate, the crystallization rate tends to increase as the film thickness increases. When forming a solar cell, for example, the p-type microcrystalline silicon layer 12 is very thin, a few tens of nanometers. Therefore, the increase in the crystallization rate does not reach saturation, and the i-type microcrystalline silicon layer It is expected that the crystallization rate will be low at the initial stage of film formation of the con layer 13.

Actually, when the crystallization rate after the formation of the n-type microcrystalline silicon layer 14 was measured, the thin film solar cell satisfying the relational expression (1) regarding the crystallization rate and the substrate temperature described above was The solar cell was polished from the n-type microcrystalline silicon layer 14 side, and the film thickness dependence of the crystallization rate of the i-type microcrystalline silicon layer 13 was measured. As a result, it was found that the crystallization rate was small in the region of several hundred nm from the p-type microcrystalline silicon layer 12 and did not satisfy the relational expression (1) regarding the crystallization rate and the substrate temperature. .

Therefore, in the method for manufacturing a thin-film solar cell of this embodiment, in the initial stage of forming the i-type microcrystalline silicon layer 13, conditions for increasing the crystallization rate, for example, water Film formation is performed under conditions where the element dilution rate is high and input power is high, and the film formation conditions are changed as the film thickness increases.

As a result, a thin film solar cell in which the crystallization rate I c / I a and the substrate temperature T sub satisfy the above relational expression (1) is formed in the entire thickness direction of the i-type microcrystalline silicon layer 13. A thin film solar cell having good solar cell characteristics can be obtained.

Further, the thin-film solar cell of this embodiment obtained by the manufacturing method as described above has the integrated intensity I _{2 2} of the (2 2 0) X-ray diffraction peak of the i-type microcrystalline silicon layer 1 3. . And (1 1 1) Crystal orientation I _{2 2} expressed as a ratio to the integrated intensity I i of the X-ray diffraction peak. / I ii Forces ^s 5 or more. As a result, an active layer with very few defects is formed, and better solar cell characteristics can be obtained.

In the present embodiment, the super-straight type thin film solar cell 20 as shown in FIG. 1 has been described as an example, but the present invention is not limited to this. For example, a substrate type thin film solar cell in which light is incident from each silicon layer side to perform photoelectric conversion may be used.

In the case of a substrate type thin film solar cell, the thin film solar cell of the present invention is at least a metal substrate or a substrate coated with metal on the surface, a transparent conductive layer having surface irregularities on the surface, It is configured to include a photoelectric conversion layer. The transparent conductive layer functions as a light scattering layer reflected by the metal surface. As a result, the same effect as that of the super-straight type thin film solar cell described above can be obtained.

Examples of deriving the above relational expression (1) relating to the thin film solar cell of the present invention will be specifically described below, but the present invention is limited by these examples. is not.

Example 1

In Example 1, a method for manufacturing a single-junction thin-film solar cell with a super-straight structure will be described according to the flow chart shown in FIG. 5 corresponding to the above-described embodiment. For convenience of explanation, members having the same functions as those explained in the above embodiment are given the same reference numerals and explanation thereof is omitted.

A thin film solar cell 20 according to Example 1 was formed as follows.

First, in step (hereinafter referred to as S) 1, a transparent conductive layer 1 1 b is formed on a substrate 11 1 a having a smooth surface, and zinc oxide is formed with a thickness of 800 nm by a magnetron sputtering method. . Thereafter, the surface of the transparent conductive layer 11 b was etched with an acetic acid aqueous solution to form irregularities, thereby forming the solar cell substrate 11.

Next, in S 2 to S 4, a p-type having a thickness of 2 O nm on the transparent conductive layer 1 1 b with an input power of 30 W on the solar cell substrate 11 1 by a high-frequency plasma CVD method. Photoelectric conversion is achieved by laminating a microcrystalline silicon layer 1 2, an i-type microcrystalline silicon layer 1 3 with a thickness of 2 ^ m, and an n-type microcrystalline silicon layer 1 4 with a thickness of 30 nm in this order. Layer 1 7 was created.

At this time, in the S 2, a p-type microcrystalline silicon co emission layer 1 2, used a material obtained by diluting Ri by a S i H ₄ gas to 1 0 0 × H ₂ gas at a flow rate ratio as raw material gases At the same time, B ₂ H ₆ gas was further added by 0.1% with respect to the Si H ₄ gas flow rate.

Then, in S 4, the n-type microcrystalline silicon layer 1 4, 3 1 ^ 1 ₄ those diluted with raw material gas by 1 0 0 × H ₂ gas to gas at a flow ratio It was formed by adding 0.01% of PH ₃ gas to the Si H ₄ gas flow rate.

In S 3, the i-type microcrystalline silicon layer 13 was formed using a material gas obtained by diluting Si H ₄ gas with H ₂ gas.

At this time, p-type microcrystalline silicon layer 1 2 and n-type microcrystalline silicon layer 1

The i-type microcrystalline silicon layer 1 is fixed at a substrate temperature of 100 ° C, the hydrogen dilution rate H ₂ ZS i H ₄ is increased 35 times, and the i-type microcrystalline silicon layer 1 is fixed. A thin film solar cell 20 with 3 was formed. The i-type microcrystalline silicon layer 13 made of S S Back pressure at the time of l X 1 0 ^{_ 7} Torr, and the oxygen atom concentration contained in the formed i-type microcrystalline silicon layer 1 3 When measured by MS, it was about 3 X ¹⁰ ¹⁸ cm- ³ , although it varied depending on the substrate temperature and crystallization rate.

Thereafter, in S 5, a transparent conductive film having a thickness of 50 n Hi was formed using zinc oxide as the back surface reflecting layer 15 by a magnetron sputtering method. Subsequently, in S 6, the back electrode 16 is formed with a thickness of 500 nm using silver by electron beam evaporation, and light is incident from the substrate 11 a side. A single-junction thin-film solar cell with a structure of 20 was manufactured.

(Examples 2 to 9)

As in Examples 2 to 9, the crystallization rate differs in the same manner as in Example 1 except that the film formation conditions (substrate temperature, hydrogen dilution rate, oxygen concentration) of the i-type microcrystalline silicon layer 1 3 are different. A thin-film solar cell with a type microcrystalline silicon layer 1 3 was formed.

[Comparative Examples 1 to 4]

As Comparative Examples 1 to 4, the film formation conditions for the i-type microcrystalline silicon layer 1 3 (substrate temperature A thin-film solar cell having an i-type microcrystalline silicon layer 13 having a different crystallization rate was formed in the same manner as in Example 1, except for the degree of hydrogen, the hydrogen dilution rate, and the oxygen concentration.

[Example 1 0 to: 1 3]

Examples 10 to 13 As the back pressure when forming microcrystalline silicon when forming the i-type microcrystalline silicon layer 1 3, 1 to: L 0 X 1 0 ^{_ 5} Torr The oxygen concentration contained in the i-type microcrystalline silicon layer 13 is set to the above example:! The properties differ depending on the production methods similar to those in Examples 1 to 9 and Comparative Examples 1 to 4 except that 6 XI 0 ^{1 8} to 2 X 10 ^{1 9} cm ³ , which is higher than the formation conditions of ~ 9 etc. A thin-film solar cell having an i-type microcrystalline silicon layer 13 having a thickness of 13 was formed.

[Comparative Example 5 * 6]

And Comparative Example 5, 6, a Back Pressure when that form the microcrystalline silicon during the film of i-type silicon layer, 1 to the ^{1 0 X 1 0- 5 T orr} , i -type silicon The above examples:! To 9 except that the oxygen concentration contained in the con layer was set to 7 X 10 ^{1 8} to 3 X 10 ^{1 9} cm ³ , which was higher than the formation conditions of Examples 1 to 9 and the like. A thin film solar cell having i-type microcrystalline silicon layer 13 having different properties was formed by the same manufacturing method as in Comparative Examples 1 to 4.

Regarding the thin film solar cells according to Examples 1 to 13 and Comparative Examples 1 to 6 as described above, the film forming conditions, the crystallization rate, the crystal orientation, and the oxygen concentration contained in the i-type microcrystalline silicon layer Table 1 shows the photoelectric conversion efficiency of the solar cell under the AM 1.5 (100 mW / cm ² ) irradiation condition.

【table 1 】 Substrate temperature Hydrogen dilution Crystallization rate Tsub X Crystal orientation Oxygen concentration Photoelectric conversion

(° C) Tsub ratio, Ic / Ia Ic / Ia (cm) Efficiency (%) Example 1 100 35 10 1000 2.5 3xl0 ¹⁸ 7.0

Example 2 200 200 3.5 700 2.7 2xl0 ¹⁸ 7.0

Example 3 200 40 6 1200 3.5 2xl0 ¹⁸ 8.2

Example 4 200 50 8 1600 2.9 2xl0 ¹⁸ 7.4

Example 5 250 45 4 1000 5.0 2xl0 ¹⁸ 8.4

Example 6 300 45 2.5 750 4.0 4xl0 ¹⁸ 8.0

Example 7 300 50 3.5 1050 6.5 4xl0 ¹⁸ 8.4

Example 8 300 70 5 1500 4.5 3xl0 ¹⁸ 7.8

Example 9 350 60 3 1050 7.5 4xl0 ¹⁸ 8.3

Example 10 200 40 6 1200 3.5 6xl0 ¹⁸ 8.2

Example 11 200 40 6 1200 3.5 2xl0 ¹⁹ 8.0

Example 12 250 45 4 1000 5.0 6xl0 ¹⁸ 7.9

Example 13 250 45 4 1000 5.0 2xl0 ¹⁹ 7.5

Comparative Example 1 200 25 2.7 540 1.9 2xl0 ¹⁸ 4.8

Comparative Example 2 200 65 8.8 1760 2.0 4xl0 ¹⁸ 6.5

Comparative Example 3 300 40 1.7 510 1.8 2xl0 ¹⁸ 6.0

Comparative Example 4 300 150 7 2100 3.7 4xl0 ¹⁸ 5.5

Comparative Example 5 300 50 3.5 1050 6.5 7xl0 ¹⁸ 6.9

Comparative Example 6 300 50 3.5 1050 6.5 3xl0 ¹⁹ 6.3 From the results of Example 1 shown in Table 1, even when the substrate temperature was 100 ° C, the hydrogen dilution rate during the formation of the photoelectric conversion layer was selected, and the crystallization rate I c It was found that by setting / I a = 10, it was possible to fabricate microcrystalline silicon-based thin-film solar cells with a photoelectric conversion efficiency exceeding the 7% range that could be put to practical use.

Thus, according to the thin-film solar cell of the present invention, a microcrystalline silicon-based thin-film solar cell can be realized even if an inexpensive resin material that is not excellent in heat resistance is used as a substrate. Furthermore, from the results of Examples 1 to 9 shown in Table 1, although the crystallization rate for obtaining high photoelectric conversion efficiency differs depending on the substrate temperature, the i-type microcrystalline silicon layer 13 is in the oxygen concentration is ^{_{4 X 1 0 1 8 C m_}} 3 following formation conditions included, irrespective of the substrate temperature T sub, the product of the substrate temperature T sub and sintering crystallization rate I c / I a is, equation ( 1) If the i-type microcrystalline silicon layer 1 3 is formed so as to satisfy (7 0 0 ≤ T sub XI c Z la ≤ 1 6 0 0), a thin film solar that can achieve relatively high photoelectric conversion efficiency It can be seen that the battery could be fabricated.

On the other hand, in Comparative Examples 1 to 4, although the i-type microcrystalline silicon layer 13 is formed under the same oxygen concentration conditions as in Examples 1 to 9, the substrate temperature T sub And the crystallization rate I c ZI a do not satisfy the above relational expression (1), so the photoelectric conversion efficiency is also low at 4.8 to 6.5%.

Thus, based on the results of Examples 1 to 9 and Comparative Examples 1 to 4, the oxygen concentration contained in the i-type microcrystalline silicon layer 1 3 is 4 X 1 ^{10 18} cm- ³ or less. Then, it was found that a thin film solar cell having a high photoelectric conversion efficiency of 7.0% or more can be produced under the formation conditions satisfying the relational expression (1).

Note that the high photoelectric conversion efficiency was maintained even when the substrate temperature was high because the i-type microcrystalline silicon layer 13 formed by the plasma CVD method was free from defects caused by an increase in the substrate temperature. This is probably because the amorphous silicon was inserted into the grain boundaries with the crystallization rate lowered, and the interface states and impurity levels were deactivated.

In addition, Examples 1 to 5 manufactured under the formation conditions where the substrate temperature is 2500 ° C or less, For 1 0-1 3 the oxygen concentration is 2-3 XI 0 ^{1 8} cm ³ Examples 1-5 are also higher, 6 X 1 0 ¹ 8-2 X 1 0 ^{1 9} cm— ³ Certain examples 10 to 13 also satisfy the condition of the above relational expression (1), and 7.0 to 8.

₀ capable of producing thin-film solar cells with 2% and high photoelectric conversion efficiency

On the other hand, in Comparative Examples 1 to 4, which were also manufactured at a substrate temperature of 25 ° C. or lower, the condition of the above relational expression (1) was not satisfied, and the photoelectric conversion efficiency was 4.8 to 6.5. % Is getting lower.

Thus, from the results of Examples 1 to 5, 10 to 13 and Comparative Examples 1 to 4, the oxygen concentration was increased or decreased under the formation conditions where the substrate temperature was 2550 ° C. or lower. Regardless, it was found that a thin-film solar cell having a high photoelectric conversion efficiency of 7.0% or more can be produced if it is produced under the formation conditions satisfying the relational expression (1).

Furthermore, as in Examples 10 to 13 and Comparative Examples 5 and 6, the oxygen concentration contained in the i-type microcrystalline silicon layer 1 3 is higher than 4 X 1 0 ¹⁸ cm— ³ 6 X 1 0 If the formation of the thin film solar cell in ^{^{1 8 ~ 3 X 1 0 1}} 9 c m- 3 formation conditions, as compared with the case of the oxygen concentration ^{2~ 4 x 1 0 1 8 cm-} 3, the substrate temperature In Example 1 0 · 11 at a temperature of 200 ° C., a relatively high photoelectric conversion efficiency equivalent to that in Example 3 was obtained. Also, in Examples 1 2 and 13 at a substrate temperature of 2500 ° C, although the photoelectric conversion efficiency is lower than that in Example 5, 7.

A high photoelectric conversion efficiency of 5 to 7.9% is obtained. As a result, when the substrate temperature is 25 ° C or lower, the oxygen concentration contained in the i-type microcrystalline silicon layer 1 3 is higher than that of 4 X 1 0 ¹⁸ c ni— ^3. Even in this case, it can be seen that high photoelectric conversion efficiency can be maintained. On the other hand, when the substrate temperature is 300 ° C., Comparative Examples 5 and 6 have a photoelectric conversion efficiency of 8.4% → compared to Example 7 formed at the same crystallization rate and substrate temperature. 6. Decreased significantly from 3 to 6.9%.

From this result, there was a large difference in photoelectric conversion efficiency between Example 7 and Comparative Examples 5 and 6 formed at the same crystallization rate and substrate temperature. When a thin film solar cell is formed under the formation conditions that are high and the oxygen concentration contained in the i-type microcrystalline silicon layer 13 is higher than 2-4 X ^{10 18} cm- ³ It can be seen that even when the relational expression (1) is satisfied, high photoelectric conversion efficiency cannot be obtained.

Also, from Table 1, crystal orientation I _{2 2} . Example 5 in which ZI _t is 5 or more

• 7 and 9 indicate that the photoelectric conversion efficiencies are as high as 8.4%, 8.4%, and 8.3%, respectively.

Therefore, the crystal orientation I _{2 2} further under the formation conditions satisfying the above relational expression (1) or (2). It was found that a thin-film solar cell with a higher level of photoelectric conversion efficiency can be obtained if it is a thin-film solar cell that satisfies the condition that ZI is 5 or more.

(Example 1 4 * 1 5)

As Example 14 except that the first 50 nm thickness of the i-type microcrystalline silicon layer 13 in the initial stage of film formation was formed at a hydrogen dilution rate of 80 times, Example 7 ( A thin film solar cell was manufactured under the same conditions as in manufacturing at a hydrogen dilution rate of 50 times.

In addition, Example 15 was carried out except that the first 50 nm thickness of the i-type microcrystalline silicon layer 13 in the initial stage of film formation was formed under the condition of input power of 60 W. Film was formed under the same conditions as in Example 7 (manufactured with an input power of 30 W). A thin film solar cell was manufactured.

Table 2 shows the photoelectric conversion efficiency of the thin-film solar cell according to Examples 14 and 15 under AM 1.5 (lOO mW / cm ² ) irradiation conditions.

Since the surface of the transparent conductive layer of the microcrystalline silicon solar cell has irregularities suitable for obtaining the light confinement effect, the distribution of the crystallization rate in the film thickness direction is the size of the irregularities. As a result, it is only averaged and an accurate value cannot be measured. Therefore, the p-type microcrystalline silicon layer 1 2, the i-type microcrystalline silicon layer 1 3, and the n-type microcrystalline silicon layer on the glass substrate under the same conditions as in Examples 4 and 14-15. 14 was laminated in order, and the crystallization rate was measured while polishing from the n-type microcrystalline silicon layer 14 side. Figure 4 shows the measurement results.

[Table 2]

Table 2 shows that the current-voltage characteristics of the thin-film solar cell according to Example 1 4 * 1 5 are improved compared to Example 7.

This is thought to be due to the following reasons.

That is, as shown in FIG. 4, in both Example 7 and Examples 14 · 15, the crystallization rate is the same level when measured from the vicinity of the n-type microcrystalline silicon layer 14. However, when the microcrystalline silicon layer is formed on an amorphous substrate, the crystallization rate tends to increase as the film thickness increases, so the p-type microcrystalline silicon layer 1 2 and the i-type silicon layer Near the interface with the microcrystalline silicon layer 1 3, the crystallization rate decreases. Therefore, in Examples 1 4 and 1 5, when forming the interface portion between the p-type microcrystalline silicon layer 1 2 and the i-type microcrystalline silicon layer 1 3, the hydrogen dilution rate or the input power is set to The film is formed at a higher temperature than normal formation conditions. For this reason, in the thin film solar cell according to Examples 14 and 15, the crystallization rate in the vicinity of the interface between the p-type microcrystalline silicon layer 12 and the i-type microcrystalline silicon layer 1 3 is not reduced. The p-type microcrystalline silicon layer 1 2 to 200 nm or more of the underlying layer has a crystallinity of about 3.5 in the entire thickness direction in the thickness direction. T sub XI c / la = 10 0 5 0).

Therefore, in this case, the value of T su b X I c / I a is included in the range of 7 0 0 ≤ T su b X I c / I a ≤ l 6 0 0 shown by the relational expression (1). As a result, an electric field is applied to the entire photoelectric conversion layer, and the photoelectric conversion efficiency of the thin-film solar cell can be more reliably maintained at a high level.

As described above, the method for producing a thin-film solar cell according to the present invention includes an i-type semiconductor layer included in at least one photoelectric conversion portion, and an oxygen concentration in the i-type semiconductor layer is 4 × 10 ^{10 18} cm. — Under the conditions of ³ or less, the peak intensity of the signal due to the crystal component of the i-type semiconductor layer by Raman scattering measurement is I c, the peak intensity of the signal due to the amorphous component is I a, and the i-type If the substrate temperature during the fabrication of the semiconductor layer is T sub, it can be formed under the formation conditions satisfying the relational expression 7 0 0 ≤ T sub XI c / I a ≤ 1 6 0 0 (1).

Therefore, there is an effect that a thin-film solar cell having high photoelectric conversion efficiency can be manufactured under a forming condition where the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm− ³ or less. That is, when the product of the substrate temperature T sub and the crystallization rate I c / I a is smaller than 700, the substrate temperature or the crystallization rate is low, and under such formation conditions, The photoelectric conversion efficiency will decrease.

On the other hand, when the product of the substrate temperature T sub and the crystallization rate I c I a is larger than 1600, the substrate temperature and / or the crystallization rate is increased. When the substrate temperature rises, oxygen in the i-type silicon layer is activated and the i-type semiconductor layer becomes _n- type, and the photoelectric conversion efficiency decreases as described above.

Therefore, according to the method for manufacturing a thin-film solar cell of the present invention, the above relational expression (1) is satisfied under the formation conditions in which the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm− ³ or less. By forming the i-type semiconductor layer by changing the crystallization rate in accordance with the formation conditions, i.e., the substrate temperature, the above-described problem of a decrease in photoelectric conversion efficiency can be achieved regardless of the substrate temperature. It is possible to produce a thin film solar cell that can prevent generation and obtain high photoelectric conversion efficiency.

As described above, the method for producing a thin-film solar cell according to the present invention includes forming an i-type semiconductor layer contained in at least one layer in a photoelectric conversion portion under a forming condition in which the substrate temperature of the substrate is 250 ° C. or less. Is the beak intensity of the signal due to the crystalline component of the i-type semiconductor layer measured by Raman scattering, I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature during the production of the i-type semiconductor layer Where T sub is the relation 7 0 0≤ T sub XI c / I a ≤ 1 6 0 0

It is a method of forming under the forming conditions satisfying (1).

Therefore, there is an effect that a thin-film solar cell having high photoelectric conversion efficiency can be manufactured under the formation conditions where the substrate temperature is 2550 ° C. or less. To do.

That is, the i-type semiconductor layer formed by the plasma C VD method or the like increases the crystal grain size and the quality of the crystal part as the substrate temperature rises. However, oxygen contained in the i-type semiconductor layer is activated and the i-type semiconductor layer becomes n-type, and hydrogen is desorbed and defects are increased, so that the photoelectric conversion efficiency of the thin-film solar cell decreases. End up.

Therefore, in the method for manufacturing a thin-film solar cell of the present invention, the i-type semiconductor layer is formed under the formation conditions satisfying the relational expression (1) under the formation conditions where the substrate temperature is 2550 ° C. or less. Thus, a thin film solar cell having a high photoelectric conversion efficiency can be produced without accompanying a decrease in the photoelectric conversion efficiency as described above.

Therefore, the above-mentioned relational expression (1) can be satisfied in the entire region of the i-type semiconductor layer in the thickness direction, and a thin film solar cell free from internal electric field bias in the thickness direction can be manufactured. Play.

That is, in general, when a microcrystalline silicon layer is formed on an amorphous substrate, the crystallization rate tends to increase as the film thickness increases, so a semiconductor layer with a very thin film thickness is formed. In this case, the increase in the crystallization rate does not reach the saturation state, and the crystallization rate is lowered at the initial stage of film formation in the i-type semiconductor layer. Therefore, in the method for manufacturing a thin-film solar cell of the present embodiment, in the initial stage of film formation of the i-type semiconductor layer, for example, the conditions for increasing the crystallization rate are, for example, the conditions for high hydrogen dilution rate and the high input power It is possible to prevent the crystallization rate from being lowered in the portion formed in the initial stage of film formation by forming the film according to conditions, etc., and appropriately changing the film formation conditions as the film thickness increases.

The thin film solar cell of the present invention is a thin film solar cell manufactured by the method for manufacturing a thin film solar cell as described above, and has a (2 2 0) X-ray diffraction peak of the i-type semiconductor layer. Integrated intensity I _{2 2} . , (1 1 1) X-ray diffraction peak integrated bow angle I 、, these ratios I _{2 2} . / I ii is the relation I _{2 2} 0 / I! ! ! ≥ 5 (2).

Therefore, by specifying the formation conditions according to the oxygen concentration in the i-type semiconductor layer, the substrate temperature, the crystallization rate, etc., it is possible to manufacture a thin-film solar cell having a high photoelectric conversion efficiency stably, Among the above thin film solar cells, there is an effect that a thin film solar cell with high photoelectric conversion efficiency can be obtained more reliably.

It should be noted that the specific embodiments or examples made in the best mode for carrying out the invention are to clarify the technical contents of the present invention. The present invention should not be construed as narrowly limited to the above, but can be implemented with various modifications within the spirit of the present invention and the scope of the following claims. Industrial applicability

According to the method for manufacturing a thin-film solar cell of the present invention, high photoelectric conversion efficiency is obtained under the formation conditions in which the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm− ³ or less. It is possible to manufacture a thin film solar cell having

That is, when the product of the substrate temperature T sub and the crystallization rate I _c / I a is smaller than 700, the substrate temperature or the crystallization rate is low, and under such formation conditions, The photoelectric conversion efficiency will decrease.

On the other hand, when the product of the substrate temperature T sub and the crystallization rate I c ZI a is larger than 1600, the substrate temperature and / or the crystallization rate is increased. When the substrate temperature rises, oxygen in the i-type silicon layer is activated and the i-type semiconductor layer becomes _n- type, and hydrogen is desorbed and defects are increased. Conversion efficiency will decrease.

According to the method for producing a thin-film solar cell of the present invention, a thin-film solar cell having high photoelectric conversion efficiency can be produced under the formation conditions where the substrate temperature is 2550 ° C. or less.

In other words, in an i-type semiconductor layer formed by plasma CVD or the like, the crystal grain size increases and the quality of the crystal part improves as the substrate temperature rises. However, when the substrate temperature rises, oxygen contained in the i-type semiconductor layer is activated and the i-type semiconductor layer becomes n-type, and hydrogen is desorbed and defects increase. The photoelectric conversion efficiency of the thin film solar cell will decrease.

Therefore, in the method for manufacturing a thin-film solar cell of the present invention, the above relational expression (1) can be obtained without the above-described decrease in photoelectric conversion efficiency under the formation conditions where the substrate temperature is 2550 ° C. or less. By forming the i-type semiconductor layer under the formation conditions that satisfy the above conditions, a thin film solar cell having high photoelectric conversion efficiency can be manufactured.

Therefore, in the method for manufacturing a thin film solar cell of the present invention, in the initial stage of forming the i-type semiconductor layer, conditions for increasing the crystallization rate include, for example, a condition with a high hydrogen dilution rate and a condition with a high input power. By forming the film and appropriately changing the film forming conditions as the film thickness increases, it is possible to prevent the crystallization rate from being lowered in the portion formed in the initial stage of film formation.

According to the method for manufacturing a thin-film Kiyo battery of the present invention, by specifying the formation conditions according to the oxygen concentration, substrate temperature, crystallization rate, etc. in the i-type semiconductor layer, stable and high photoelectric conversion is achieved. A thin film solar cell having high efficiency can be manufactured, and among the above thin film solar cells, a thin film solar cell with high photoelectric conversion efficiency can be obtained more reliably.

Claims

WO 03 / 07351S Hiring PCT / JPO 999 35 Scope of claim

1. In a method for manufacturing a thin-film solar cell, which has a photoelectric conversion part on a substrate and converts incident light into electric energy in the photoelectric conversion part.

The i-type semiconductor layer included one layer at least on the photoelectric converter, the oxygen concentration is ^{4 X 1 0 1 8 c m_} 3 under the following conditions of the i-type semi-conductor layer, the i by Raman scattering measurement If the peak intensity of the signal due to the crystal component of the n-type semiconductor layer is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature at the time of fabrication of the i-type semiconductor layer is T sub, then A method for producing a thin-film solar cell, characterized in that the thin-film solar cell is formed under formation conditions satisfying the relational expression (1).

7 0 0≤ T s u b X I c / I a ≤ 1 6 0 0 (1)

2. In a method for manufacturing a thin-film solar cell, which has a photoelectric conversion part on a substrate and converts incident light into electric energy in the photoelectric conversion part.

The i-type semiconductor layer included in at least one layer in the photoelectric conversion portion is subjected to a formation condition in which the substrate temperature of the substrate is 2500 ° C. or less.

The peak intensity of the signal due to the crystalline component of the i-type semiconductor layer measured by Raman scattering is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature when the i-type semiconductor layer is fabricated is T sub Then, a method for producing a thin-film solar cell, characterized in that the thin-film solar cell is formed under formation conditions that satisfy the following relational expression (1).

7 0 0 ≤ T s u b X I c / l a ≤ 1 6 0 0 (1)

3. A thin film solar cell manufactured by the method for manufacturing a thin film solar cell according to claim 1 or 2, In the initial stage of film formation of the i-type semiconductor layer, the i-type semiconductor layer is formed under the condition that the crystallization rate is high when the film is formed on the amorphous substrate. A thin-film solar cell characterized by satisfying the above relational expression (1) in all regions.

4. A thin film solar cell manufactured by the method for manufacturing a thin film solar cell according to claim 1 or 2,

The integrated intensity I _{2 2} of the (2 2 0) X-ray diffraction peak of the i-type semiconductor layer. (1 1 1) If the integrated intensity of the X-ray diffraction peak is Ι _{1 1} , the ratio of these 1 _{2 2} . Z l ^ i is a thin film solar cell characterized by satisfying the following relational expression (2).

I 2 2 0 / I 1 1 1 = °

5. In a thin-film solar cell having a photoelectric conversion part on a substrate and converting incident light into electric energy in the photoelectric conversion part,

The i-type semiconductor layer included in at least one layer in the photoelectric conversion portion is subjected to Raman scattering measurement under the above-mentioned i-type semiconductor layer under the condition that the oxygen concentration in the i-type semiconductor layer is 4 × ^{10 18} cm− ³ or less. If the peak intensity of the signal due to the crystal component of the n-type semiconductor layer is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature at the time of fabrication of the i-type semiconductor layer is T sub, then A thin film solar cell formed under the formation conditions satisfying the relational expression (1).

7 0 0 ≤ T s u b X I c / l a ≤ 1 6 0 0 (1)

6. In a thin-film solar cell having a photoelectric conversion part on a substrate and converting incident light into electric energy in the photoelectric conversion part,

The i-type semiconductor layer included in at least one layer in the photoelectric conversion portion is subjected to a forming condition where the substrate temperature of the substrate is 2550 ° C. or lower. The peak intensity of the signal due to the crystalline component of the i-type semiconductor layer measured by Raman scattering is I c, the peak intensity of the signal due to the amorphous component is I a, and the substrate temperature at the time of fabrication of the i-type semiconductor layer is T sub Then, the thin film solar cell formed on the formation conditions which satisfy | fill the following relational expression (1).

7 0 0 ≤ T s u b X I c / l a ≤ 1 6 0 0 (1)

7. The thin film solar cell according to claim 5 or 6, wherein the crystallization rate satisfies the relational expression (1) in the entire region in the film thickness direction of the i-type semiconductor layer. A thin film solar cell characterized.

8. The thin-film solar cell according to claim 5 or 6, wherein the integrated intensity I _{2 2} of the (2 2 0) X-ray diffraction peak of the i-type semiconductor layer. , (

1 1 1) If the integrated intensity of the X-ray diffraction peak, then the ratio of these 1 _{2 2} .

I i _t is a thin film solar cell that satisfies the following relational expression (2).

I 2 2 o / I 1 1 1≥ 5 (2)

9. The thin film according to any one of claims 5 to 8, wherein in the case of a single-junction thin film solar cell, the photoelectric conversion layer includes a layer containing microcrystalline silicon. Solar cell.

10. In the case of a multi-junction thin film solar cell, any one of claims 5 to 8 wherein a layer containing microcrystalline silicon and a layer containing amorphous silicon are mixed. 2. The thin film solar cell according to item 1.