JP5636325B2 - Thin film solar cell and manufacturing method thereof - Google Patents

Description

  The present invention relates to a thin film solar cell and a method for manufacturing the same.

  In recent years, thin-film solar cells that use less raw materials have attracted attention in order to achieve low cost and high efficiency of solar cells.

  A general thin film solar cell includes a photoelectric conversion unit in which a p-type layer (p-type semiconductor layer), an i-type layer (i-type semiconductor layer), and an n-type layer (n-type semiconductor layer) are sequentially stacked. Such pin-type or nip-type photoelectric conversion units are classified into amorphous photoelectric conversion units in which the i-type layer occupying most of the structure is amorphous and crystalline photoelectric conversion units other than amorphous. Is done.

  By the way, mass production is necessary to spread the thin film solar cells. As a measure for mass-producing thin film solar cells, a method of forming a photoelectric conversion unit at a high speed using a CVD method can be mentioned. However, when a crystalline photoelectric conversion unit is formed at a high speed, a crystal grain boundary is likely to be generated, and defects concentrate on the crystal grain boundary, resulting in a decrease in the open-circuit voltage and the fill factor of the solar cell. There is a problem that the conversion efficiency tends to decrease.

  Therefore, in the crystalline photoelectric conversion unit of Patent Document 1, the photoelectric conversion efficiency is improved by inserting a silicon oxide low-refractive layer between the i-type crystalline silicon layer and the n-type silicon-based interface layer.

Japanese Patent No. 4257332

  However, in Patent Document 1, the decrease in the open circuit voltage is suppressed to the same level as the conventional open circuit voltage, but the decrease in the fill factor has not been improved, and there is still room for improvement.

  Therefore, the present invention solves the above-described problems, and an object of the present invention is to develop a thin film solar cell having high photoelectric conversion efficiency while suppressing a decrease in open circuit voltage and a fill factor.

The invention according to claim 1 for solving the above-mentioned problem is a thin-film solar cell in which at least a first electrode layer having translucency, a photoelectric conversion layer, and a second electrode layer are stacked on a substrate. The photoelectric conversion layer has at least a crystalline photoelectric conversion unit, and the crystalline photoelectric conversion unit has a p-type crystal layer, an i-type crystal layer, and an n-type microcrystalline layer, and the p-type The crystal layer is made of p-type microcrystalline silicon, the i-type crystal layer is made of i-type crystalline silicon, and the n-type microcrystalline layer is made of n-type microcrystalline silicon. In addition, an n-type amorphous layer and an n-type alloy layer are laminated in order from the i-type crystal layer side between the i-type crystal layer and the n-type microcrystalline layer, and the n-type alloy layer includes oxygen, A silicon alloy composed of one or more elements selected from carbon and nitrogen and silicon elements. The n-type alloy layer is an n-type microcrystalline silicon oxide, and the n-type amorphous layer is a layer formed of an amorphous n-type semiconductor, The thin-film solar cell is characterized in that the n-type amorphous layer is formed of n-type amorphous silicon.
That is, the invention according to claim 1 is a thin film solar cell in which at least a light-transmitting first electrode layer, a photoelectric conversion layer, and a second electrode layer are stacked on a substrate. It has at least a crystalline photoelectric conversion unit, and the crystalline photoelectric conversion unit has a p-type crystal layer, an i-type crystal layer, and an n-type microcrystalline layer, and the p-type crystal layer has p The i-type crystal layer is made of i-type crystalline silicon, the n-type microcrystalline layer is made of n-type microcrystalline silicon, and the i-type crystal An n-type amorphous layer and an n-type alloy layer are stacked in this order from the i-type crystal layer side between the layer and the n-type microcrystalline layer, and the n-type alloy layer is formed of oxygen, carbon, or nitrogen. Formed from a silicon alloy composed of one or more elements selected from , N-type amorphous layer is a layer formed of an amorphous n-type semiconductor, you wherein the band gap is larger than the i-type crystalline layer.

  Note that the “p-type” referred to here represents one in which holes are used as carriers for carrying charges. The “i-type” represents a pure substance to which substantially no impurities are added. “N-type” refers to those in which free electrons are used as carriers carrying charge. “Crystal” as used herein refers to something other than amorphous. That is, it is a concept including microcrystal, single crystal, polycrystal and the like. “Microcrystal” refers to a crystal having a crystal volume fraction of 1% to almost 100% and a crystal grain size of 1 nm to 2 μm with respect to the amorphous component.

  That is, the n-type alloy layer is formed of a silicon alloy composed of one or more elements selected from oxygen, carbon, and nitrogen and a silicon element.

In the related invention of the present invention , the n-type alloy layer is any one of n-type amorphous silicon carbide, n-type microcrystalline silicon oxide, n-type amorphous silicon nitride, and n-type amorphous silicon oxynitride. The thin film solar cell according to claim 1, wherein

The film thickness of the n-type alloy layer is preferably 5 nm to 100 nm (claim 2).

According to one aspect of the present invention, n-type amorphous layer, that is formed by the n-type amorphous silicon.

The film thickness of the n-type amorphous layer is preferably 0.1Nm～20nm (claim 3).

According to one aspect of the present invention, n-type alloy layer, characterized in that an n-type microcrystalline silicon oxide.

The thickness of the n-type microcrystalline layer is preferably 0.1Nm～30nm (claim 4).

The invention according to claim 5 is an amorphous structure in which the photoelectric conversion layer includes a p-type amorphous layer, an i-type amorphous layer, and an n-type amorphous layer in addition to the crystalline photoelectric conversion unit. The p-type amorphous layer is made of p-type amorphous silicon or p-type amorphous silicon carbide, and the i-type amorphous layer is made of i-type amorphous. is formed from a quality silicon, the n-type amorphous layer is a thin-film solar cell according to any one of claims 1 to 4, characterized in that it is formed from n-type amorphous silicon.

It is preferable that the photoelectric conversion layer is laminated | stacked in order of the amorphous photoelectric conversion unit and the crystalline photoelectric conversion unit from the board | substrate side (Claim 6 ).

A seventh aspect of the present invention is the method of manufacturing a thin film solar cell according to any one of the first to sixth aspects, wherein the step of forming the n-type amorphous layer is performed by performing a hydrogen plasma treatment during the film formation. It is a manufacturing method of the thin film solar cell characterized by having a plasma treatment process.

In the method described above, at the stage of 70% to 30% of the film thickness are stacked as a target of n-type amorphous layer, it is preferable to perform the plasma treatment process (claim 8).

In the thin film solar cell of the present invention, since the n-type amorphous layer has a larger band gap than the i-type crystal layer, the electron collecting effect on the valence band side is excellent. That is, it has a high open circuit voltage. In addition, since the n-type amorphous layer is doped n-type, recombination of carriers due to entry of holes can be suppressed.
Further, since the n-type alloy layer is provided, the effect of the n-type amorphous layer can be further promoted by the interaction between the n-type amorphous layer and the n-type alloy layer.
Since the n-type microcrystalline layer is laminated on the n-type alloy layer, the n-type alloy layer functions as a base of the n-type microcrystalline layer, and the crystal of the n-type microcrystalline layer is obtained due to the effect of inhibiting crystallization of different elements. The increase in diameter can be suppressed.
According to the method for manufacturing a thin film solar cell of the present invention, in the step of forming the n-type amorphous layer, the plasma processing step of performing the hydrogen plasma treatment in the middle of the film formation includes the n-type amorphous layer on the i-type crystal layer. It is possible to passivate defects (hereinafter referred to as “dangling bonds”) that occur at the initial stage when laminating a type amorphous layer.

It is a conceptual diagram of the thin film solar cell of 1st Embodiment of this invention. It is a conceptual diagram of the thin film solar cell of 1st Embodiment of this invention. The sealing member is excluded. Further, only the crystalline photoelectric conversion unit is hatched for easy understanding. 3 is a flowchart showing a film forming process of the n-type amorphous layer of FIG.

  The present invention relates to a thin film solar cell and a method for producing the thin film solar cell. FIG. 1 shows a thin film solar cell 1 according to a first embodiment of the present invention. In the present embodiment, a thin film solar cell having both an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit, which is called a hybrid solar cell among those skilled in the art, will be described as an example.

  As shown in FIG. 1, the thin-film solar cell 1 has a structure in which a first electrode layer 3, a photoelectric conversion unit 5, and a second electrode layer 6 are laminated in this order on one surface of a substrate 2. These are sealed by the sealing member 7. Then, as shown in FIG. 1, sunlight is incident from the substrate 2 side, and power is generated by absorbing the sunlight.

  Hereinafter, the configuration of the thin-film solar cell 1 will be described in order from the sunlight incident side (lower side in FIG. 2) mainly using FIG. In FIG. 2, the sealing member 7 is omitted for convenience of explanation.

  The material of the substrate 2 is not particularly limited, and is appropriately selected from, for example, a flexible film substrate or a plastic substrate. In particular, a glass substrate or a transparent film substrate is preferable in terms of transparency and good workability.

The material constituting the first electrode layer 3 is not particularly limited as long as it is a conductive material. For example, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ). A conductive metal oxide such as zinc oxide (ZnO) can be used. The surface of the first electrode layer 3 preferably has fine irregularities. The first electrode layer 3 is formed by a known method such as sputtering or vacuum deposition.

  Subsequently, the photoelectric conversion unit 5 (photoelectric conversion layer) is a deposited layer that absorbs solar incident light and converts it into electricity. The photoelectric conversion unit 5 is divided into an amorphous photoelectric conversion unit 11 and a crystalline photoelectric conversion unit 12 in order from the first electrode layer 3 side. That is, the amorphous photoelectric conversion unit 11 and the crystalline photoelectric conversion unit 12 are laminated in this order on the first electrode layer 3.

The layer configuration of the amorphous photoelectric conversion unit 11 will be described.
The amorphous photoelectric conversion unit 11 has a structure in which at least a p-type amorphous layer 15, an i-type amorphous layer 16, and an n-type amorphous layer 17 are stacked in order from the substrate 2 side (the lower side in FIG. 2). Formed from layers.

The p-type amorphous layer 15 is a layer formed of an amorphous p-type semiconductor. As a constituent material of the p-type amorphous layer 15, for example, p-type amorphous silicon or p-type amorphous silicon carbide (SiC) can be employed. Note that the “p-type” referred to here represents one in which holes are used as carriers for carrying charges.
The i-type amorphous layer 16 is a layer formed of an amorphous i-type semiconductor. As a constituent material of the i-type amorphous layer 16, for example, i-type amorphous silicon can be employed. The “i-type” referred to here represents a pure product to which substantially no impurities are added.
The n-type amorphous layer 17 is a layer formed of an amorphous n-type semiconductor. As a constituent material of the n-type amorphous layer 17, for example, n-type amorphous silicon can be adopted. The “n-type” referred to here represents one in which free electrons are used as carriers for carrying charges.

Next, the layer configuration of the crystalline photoelectric conversion unit 12 will be described. The thin film solar cell 1 of the present embodiment has a characteristic configuration in the crystalline photoelectric conversion unit 12.
The crystalline photoelectric conversion unit 12 includes at least a p-type crystal layer 18, an i-type crystal layer 20, an n-type amorphous layer 21, an n-type alloy layer 22, and an n-type microcrystal in order from the substrate 2 side (lower in FIG. 2). The layer 23 is formed of five layers stacked. That is, the n-type amorphous layer 21 and the n-type alloy layer 22 are interposed between the i-type crystal layer 20 and the n-type microcrystalline layer 23.

The p-type crystal layer 18 is a layer formed of a crystalline p-type semiconductor, and is preferably a layer formed of a microcrystalline p-type semiconductor. As a constituent material of the p-type crystal layer 18, for example, p-type microcrystalline silicon can be employed. “Crystal” as used herein refers to something other than amorphous. That is, it is a concept including microcrystals and polycrystals. “Microcrystal” refers to a crystal having a crystal volume fraction of 1% to almost 100% and a crystal grain size of 1 nm to 2 μm with respect to the amorphous component.
The i-type crystal layer 20 is a layer formed of a crystalline i-type semiconductor. As a constituent material of the i-type crystal layer 20, for example, i-type crystalline silicon can be employed.

  The n-type amorphous layer 21 is a layer formed of an amorphous n-type semiconductor, and is formed of a material having a band gap larger than that of the i-type crystal layer 20. As a constituent material of the n-type amorphous layer 21, for example, when the i-type crystal layer 20 is i-type crystalline silicon, n-type amorphous silicon, n-type amorphous silicon carbide, or the like can be employed.

  The film thickness of the n-type amorphous layer 21 is preferably 0.1 nm to 20 nm, and particularly preferably 0.5 nm to 5 nm.

The n-type alloy layer 22 is composed of a silicon alloy composed of one or more elements selected from oxygen, carbon, and nitrogen (heterogeneous elements) and a silicon element.
For example, the n-type alloy layer 22 includes n-type amorphous silicon carbide (SiC), n-type microcrystalline silicon oxide (SiO ₂ ), n-type amorphous silicon nitride (Si ₃ N ₄ ), n-type amorphous. it is preferably formed of quality silicon oxynitride (SiO _x N _y) or the like. In particular, it is more preferable to use n-type amorphous silicon carbide and n-type microcrystalline silicon oxide. N-type microcrystalline silicon oxide is more preferable in that the refractive index is lower than that of the n-type amorphous layer 21, that is, the light reflection property is high.

  The film thickness of the n-type alloy layer 22 is preferably 5 nm to 100 nm, and particularly preferably 15 nm to 60 nm.

  The n-type microcrystalline layer 23 is a layer formed from a microcrystalline n-type semiconductor. For example, n-type microcrystalline silicon can be used.

The film thickness of the n-type microcrystalline layer 23 is preferably 0.1 nm to 30 nm, and particularly preferably 2.5 nm to 15 nm.
The above is the layer configuration of the crystalline photoelectric conversion unit 12.

  Subsequently, when the eyes are moved to the second electrode layer 6, the second electrode layer 6 has an oxide layer 8 and a reflective electrode layer 10 on the n-type microcrystalline layer 23 in order from the incident light side (lower side in FIG. 2). It has a laminated structure. The material of the oxide layer 8 is not particularly limited, but metal oxides such as indium tin oxide (ITO) and zinc oxide (ZnO) are suitable. The material of the reflective electrode layer 10 is not particularly limited, but is preferably aluminum (Al) or silver (Ag). For example, a metal, an alloy, an electrically conductive compound, and a mixture thereof may be used. it can. The oxide layer 8 and the reflective electrode layer 10 can be formed by various known methods, but it is particularly preferable to form them by a CVD method, a sputtering method, or a vacuum evaporation method.

The material of the sealing member 7 is not particularly limited. For example, ethylene / vinyl acetate copolymer (EVA), ethylene / vinyl acetate / triallyl isocyanurate (EVAT), polyvinyl butyrate (PVB), polyisobutylene. (PIB), polyolefin resin, ionomer resin, or the like can be used. From the viewpoint of not requiring a heat treatment step for curing, polyolefin-based resins and ionomer-based resins are preferable.
Furthermore, a moisture absorbing material or an oxygen absorbing material may be provided on the photoelectric conversion unit 5 side of the sealing member 7, or these may be blended in the sealing member itself. As such an absorbent, for example, barium oxide (BaO), calcium oxide (CaO), alkali metal, alkaline earth metal, or active iron oxide fine powder can be used.
The above is the description of the configuration of the thin film solar cell 1.

Next, the manufacturing method of the thin film solar cell 1 which concerns on this embodiment is demonstrated.
The thin film solar cell 1 is manufactured using, for example, a high-frequency plasma CVD apparatus, a vacuum vapor deposition apparatus, and a laser scribing apparatus. Hereinafter, each process will be described in order.

First, the first electrode layer 3 is formed on the substrate 2.
As the material of the first electrode layer 3, indium tin oxide (ITO), tin oxide (SnO ₂ ), zinc oxide (ZnO), or the like is used. The first electrode layer 3 is formed on the substrate 2 by a CVD method, a sputtering method, or a vacuum evaporation method.

  Subsequently, a laser scribing process is performed as necessary to form first electrode layer separation grooves in the first electrode layer 3.

  In addition, as a laser scribing apparatus, what has an XY table, a laser generator, and an optical engagement member can be used, for example. The first laser scribing step is performed by placing the substrate 2 on an XY table and moving the substrate 2 linearly at a constant speed in the vertical direction while irradiating the laser beam. Then, the X / Y table is moved in the horizontal direction to shift the irradiation position of the laser beam, and the substrate 2 is linearly moved again in the vertical direction while irradiating the laser beam.

  The substrate after the first laser scribing step is cleaned on the surface in some cases in order to remove the scattered film. A known cleaning method can be applied as the cleaning method.

  Next, an amorphous photoelectric conversion unit 11 is formed on the first electrode layer 3. That is, three layers of a p-type amorphous layer 15, an i-type amorphous layer 16, and an n-type amorphous layer 17 are formed in this order on the substrate.

Each layer of the amorphous photoelectric conversion unit 11 can be formed by various known methods, but it is particularly preferable to use a plasma CVD method. The formation conditions of each layer of the amorphous photoelectric conversion unit 11 when using the plasma CVD method are a substrate temperature of 100 ° C. to 300 ° C., a pressure of 20 to 2600 Pa, and a plasma output of 0.003 to 0.6 W / cm ^2. Is preferred. Moreover, as source gas used for formation of each layer of the amorphous photoelectric conversion unit 11, silicon-containing gases such as monosilane (SiH ₄ ) and disilane (Si ₂ H ₆ ), and these silicon-containing gases are diluted with hydrogen. Can be used. As the dopant gas, diborane (B ₂ H ₆ ) or the like can be used for the p-type amorphous layer 15, and phosphine (PH ₃ ) or the like can be used for the n-type amorphous layer 17.

Subsequently, a crystalline photoelectric conversion unit 12 is formed on the amorphous photoelectric conversion unit 11. That is, five layers of a p-type crystal layer 18, an i-type crystal layer 20, an n-type amorphous layer 21, an n-type alloy layer 22, and an n-type microcrystalline layer 23 are formed on the substrate in this order.
Specifically, first, the p-type crystal layer 18 is formed on the substrate.
The p-type crystal layer 18 can be formed by various known methods, but it is particularly preferable to use a plasma CVD method.
The formation conditions of the p-type crystal layer 18 when using the plasma CVD method are preferably a substrate temperature of 100 ° C. to 300 ° C., a pressure of 500 to 1300 Pa, and a plasma output of 0.03 to 0.3 W / cm ² . As the source gas used for forming the p-type crystal layer 18, a silicon-containing gas such as monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ), or a gas obtained by diluting these silicon-containing gases with hydrogen is employed. it can. Diborane (B ₂ H ₆ ) or the like can be used as the dopant gas.

Subsequently, an i-type crystal layer 20 is formed on the p-type crystal layer 18.
The i-type crystal layer 20 can be formed by various known methods, but it is particularly preferable to use a plasma CVD method.
The formation conditions of the i-type crystal layer 20 when the plasma CVD method is used are preferably a substrate temperature of 100 ° C. to 300 ° C., a pressure of 600 to 2600 Pa, and a plasma output of 0.1 to 0.7 W / cm ² . As the source gas used for forming the i-type crystal layer 20, a silicon-containing gas such as monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ), or a gas obtained by diluting these silicon-containing gases with hydrogen is employed. it can.

Subsequently, an n-type amorphous layer 21 is formed on the i-type crystal layer 20. The method for manufacturing a thin-film solar cell of the present invention is characterized by a method for forming the n-type amorphous layer 21.
The n-type amorphous layer 21 is basically formed by a plasma CVD method.

  The film forming process of the n-type amorphous layer 21 includes three processes. That is, the film formation process of the n-type amorphous layer 21 includes an initial film formation process, a plasma treatment process, and a late film formation process as shown in FIG.

In the initial film formation process, the distance between the substrate film formation surface and the electrode in the CVD apparatus is 7 to 20 mm, the pressure is 20 to 2600 Pa, and the plasma output is 0.003 to 0.3 W / cm ^{2 by} the CVD method. Film formation is performed. The source gas used for the film formation is not particularly limited, but a silicon-containing gas such as monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ), or a gas obtained by diluting these silicon-containing gases with hydrogen can be employed. Particularly in the case of amorphous silicon, a mixed gas of monosilane (SiH ₄ ) and hydrogen is suitable. As the dopant gas, phosphine (PH ₃ ) or the like can be adopted. Then, monosilane (SiH ₄₎ and phosphine (PH _3), when depositing the n-type amorphous layer 21, the flow rate of monosilane (SiH ₄₎ and phosphine (PH ₃₎ is 1: 2 It is preferable.

The film formation of the n-type amorphous layer 21 is started on the substrate (first film formation start). Thereafter, when the layers are stacked until a predetermined film thickness is reached, the film forming operation is stopped (end of the first film forming), and the process proceeds to the plasma processing step.
Specifically, it is preferable to shift to the plasma processing step using the stage where 30% to 70% of the film thickness at the end of the formation of the entire n-type amorphous layer 21 is stacked as the switching reference value. It is more preferable to set 40% to 60% of the film thickness at the end of the entire film formation of the n-type amorphous layer 21 as the switching reference value. It is particularly preferable to set 45% to 55% of the film thickness at the end of the entire film formation of the n-type amorphous layer 21 as the switching reference value.

Subsequently, in the plasma processing step, the substrate is irradiated with hydrogen plasma.
As conditions for the hydrogen plasma treatment, a distance of 7 to 20 mm, a pressure of 20 to 2600 Pa, and a plasma output of 0.003 to 0.3 W / cm ² can be adopted between the substrate film formation surface and the electrode in the CVD apparatus. The plasma output is preferably 0.1 W / cm ² or less, and more preferably 0.05 W / cm ² or less.

Irradiation of hydrogen plasma to the substrate is started, and when a predetermined time has elapsed, the irradiation of hydrogen plasma is terminated, and the process proceeds to a later film formation step.
Specifically, it is preferable to move to the later film-forming process with the switching reference time being 5 seconds to 300 seconds from the start of the hydrogen plasma irradiation. It is more preferable that 10 seconds to 180 seconds elapse from the start of hydrogen plasma irradiation as the switching reference time. It is particularly preferable that 30 to 90 seconds elapse from the start of hydrogen plasma irradiation as the switching reference time.

In the latter film formation step, the n-type amorphous layer 21 is formed on this substrate (second film formation start).
Film formation is performed by the CVD method under the conditions that the distance between the substrate film formation surface and the electrode in the CVD apparatus is 7 to 20 mm, the pressure is 20 to 2600 Pa, and the plasma output is 0.003 to 0.3 W / cm ² . The source gas used for the film formation is not particularly limited, but in the case of amorphous silicon, a mixed gas of SiH ₄ and H ₂ is suitable.
Thereafter, when the film is formed to the target film thickness, the film formation is finished (second film formation is completed).
The film forming process of the n-type amorphous layer 21 has been described above.

  Subsequently, an n-type alloy layer 22 is formed on the n-type amorphous layer 21 formed as described above.

The n-type alloy layer 22 can be formed by a known method, but it is particularly preferable to use a plasma CVD method.
For example, when an n-type microcrystalline silicon oxide film is formed by plasma CVD, a mixed gas of SiH ₄ , H ₂ , PH _3, and CH ₄ can be used as a source gas used for film formation. As a specific flow rate ratio of this mixed gas, when SiH ₄ is 1, H ₂ is preferably 10 to 300, PH ₃ is preferably 0.1 to 10, and CO ₂ is preferably 0.5 to 5.5. . Further, as conditions for plasma CVD at the time of forming the n-type microcrystalline silicon oxide, the distance between the substrate film formation surface and the electrode of the CVD apparatus is 6 to 13 mm, the pressure is 800 to 1800 Pa, and the plasma output is 0.12 to 0. .27 W / cm ² can be suitably employed.
When forming an n-type amorphous silicon carbide film by the plasma CVD method, a mixed gas of SiH ₄ , H ₂ , PH _3, and CH ₄ can be used as a source gas used for film formation. As a specific flow ratio of this mixed gas, when SiH ₄ is 1, H ₂ is preferably 0 to 10, PH ₃ is preferably 1 to 4, and CH ₄ is preferably 0.5 to 2.0. The plasma CVD conditions for forming the n-type amorphous silicon carbide are as follows: the distance between the substrate deposition surface and the electrode in the CVD apparatus is 7 to 20 mm, the pressure is 30 to 200 Pa, and the plasma output is 0.005. -0.02 W / cm < ² > can be employ | adopted suitably.

  Subsequently, an n-type microcrystalline layer 23 is formed on the n-type alloy layer 22 formed as described above.

The n-type microcrystalline layer 23 can be formed by a known method, but it is particularly preferable to use a plasma CVD method.
For example, when n-type microcrystalline silicon is formed by a plasma CVD method, a mixed gas of SiH ₄ , H _2, and PH ₃ can be used as a source gas used for film formation. The conditions for plasma CVD during the deposition of n-type microcrystalline silicon are as follows: the distance between the substrate deposition surface and the electrode in the CVD apparatus is 7 to 20 mm, the pressure is 500 to 1300 Pa, and the plasma output is 0.03 to 0.03. It is preferably 0.3 W / cm ² .

  And a 2nd laser scribing process is performed with respect to the board | substrate taken out from the CVD apparatus as needed, and the photoelectric converting layer separation groove | channel is formed in the photoelectric conversion unit 5. FIG.

  Subsequently, the substrate is inserted into a vacuum evaporation apparatus, and the second electrode layer 6 is formed on the photoelectric conversion unit 5.

  Subsequently, a third laser scribing process is performed as necessary to form unit light emitting element separation grooves in both the second electrode layer 6 and the photoelectric conversion unit 5.

Further, a power supply electrode (not shown) is formed, a separation groove (not shown) on the outside thereof is formed as necessary, and the second electrode layer 6 and the like on the outer portion of the separation groove are removed.
Thereafter, the sealing member 7 is installed, and a laminating process and a curing process in which heat sealing is performed are performed, and the thin film solar cell 1 of the present embodiment is completed.

In the thin film solar cell 1 formed as described above, the n-type amorphous layer 21 has a band gap larger than that of the i-type crystal layer 20, so that the electron collecting effect on the valence band side is excellent. That is, it has a high open circuit voltage. Further, since the n-type amorphous layer 21 is doped n-type, recombination of carriers due to entry of holes can be suppressed.
Moreover, according to the manufacturing method of the thin film solar cell 1 as described above, the film forming process of the n-type amorphous layer 21 includes a plasma processing process for performing a hydrogen plasma process. It is possible to passivate dangling bonds generated when the type amorphous layer 21 is laminated.

  In the above-described embodiment, the photoelectric conversion unit 5 has the two photoelectric conversion units of the amorphous photoelectric conversion unit 11 and the crystalline photoelectric conversion unit 12, but has at least one crystalline photoelectric conversion unit 12. The number of photoelectric conversion units is not limited. That is, only the crystalline photoelectric conversion unit 12 may be provided, or three or more photoelectric conversion units may be provided.

  In the embodiment described above, in the film formation process of the n-type amorphous layer 21, the switching reference value for switching from the initial film formation process to the plasma treatment process is set to the film thickness at the end of the film formation of the n-type amorphous layer 21. However, the present invention is not limited to this, and the film formation time of the n-type amorphous layer 21 relative to the total film formation time of the n-type amorphous layer 21 may be used as the film formation reference value.

  In the above-described embodiment, the curing process is performed. However, the present invention is not limited to this, and the curing process may be omitted depending on the material of the sealing member. For example, when a polyolefin resin or an ionomer resin is used, a curing process that increases costs and reduces productivity can be omitted.

  In the above-described embodiment, after forming the i-type crystal layer 20, the process proceeds to the process of forming the n-type amorphous layer 21. However, the present invention is not limited to this, and the i-type crystal layer 20 is formed. After the film formation, the i-type crystal layer 20 may be subjected to a hydrogen plasma treatment and then may be shifted to the film formation process of the n-type amorphous layer 21.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

  A specific example of the present invention and a manufacturing procedure of a thin film solar cell of a comparative example with respect to the example and evaluation results thereof will be described.

[Example 1]
In Example 1, a hybrid thin film solar cell conceptually shown in FIG. 1 was manufactured by the following procedure.

  First, a first laser scribing step was performed on a transparent conductive glass (glass with a TCO film) having a thickness of 5.0 mm.

  Next, an amorphous photoelectric conversion unit 11 was formed. That is, after introducing the glass with a TCO film into a high-frequency plasma CVD apparatus and heating to 160 ° C., a p-type amorphous silicon carbide layer having a thickness of 15 nm, an i-type amorphous silicon layer having a thickness of 300 nm, and a film N-type amorphous silicon layers having a thickness of 30 nm were sequentially stacked.

Subsequently, a crystalline photoelectric conversion unit was formed. That is, using a plasma CVD apparatus, a p-type microcrystalline silicon layer having a thickness of 15 nm, an i-type crystalline silicon layer having a thickness of 1.5 μm, an n-type amorphous silicon layer having a thickness of 3 nm, and an n-type having a thickness of 50 nm. A type silicon alloy layer and an n-type microcrystalline silicon layer having a thickness of 10 nm were sequentially laminated.
In this case, the i-type crystalline silicon layer is formed under the following conditions: the substrate deposition surface-electrode distance is 10 mm, the pressure is 1000 Pa, the plasma output is 0.3 W / cm ² , and the flow ratio of SiH ₄ and H ₂ is 1: 100. did. The average film formation speed under these film formation conditions was 0.3 nm / second.
The deposition conditions for the n-type amorphous silicon layer were as follows: the distance between the substrate deposition surface and the electrode was 10 mm, the pressure was 300 Pa, the plasma output was 0.04 W / cm ² , and the flow ratio of SiH ₄ and PH ₃ was 1: 2.
An n-type microcrystalline silicon oxide layer was formed as an n-type silicon alloy layer. The film forming conditions were such that the distance between the substrate film forming surface and the electrode was 10 mm, the pressure was 1000 Pa, the plasma output was 0.15 W / cm ² , and the flow ratio of SiH ₄ , PH ₃ and CO ₂ was 1: 2: 5. The film formation conditions for the n-type microcrystalline silicon layer are as follows: the distance between the substrate formation surface and the electrode is 10 mm, the pressure is 800 Pa, the plasma output is 0.15 W / cm ² , and the flow ratio of SiH ₄ , PH ₃ and H ₂ is 1: 4: 200.

Next, a second laser scribing step was performed on the formed glass substrate.
Thereafter, an oxide layer 8 made of zinc oxide having a thickness of 80 nm was formed by sputtering, and a reflective electrode layer 10 made of silver having a thickness of 250 nm was formed by electron beam evaporation. Furthermore, a third laser scribe process was performed.

The fabricated hybrid thin-film solar cell is irradiated with simulated sunlight having a spectral distribution AM1.5 and an energy density of 100 W / cm ² under the conditions where the measurement ambient temperature and the temperature of the solar cell are 25 ± 1 ° C. By measuring the current, the output characteristics of the thin film solar cell were measured (hereinafter referred to as “before curing”).

Next, the sealing process was implemented using the ethylene / vinyl acetate copolymer (EVA). After the laminating step, the curing process is performed at 150 ° C. for 120 minutes to complete the crosslinking reaction, and then the spectrum distribution AM1 is measured under the conditions where the measurement ambient temperature and the temperature of the solar cell are 25 ± 1 ° C. .5, simulated sunlight with an energy density of 100 W / cm ² was irradiated, and the output characteristics of the thin-film solar cell were measured again (hereinafter referred to as after curing).

[Example 2]
A hybrid thin film solar cell was prepared according to Example 1, but in Example 2, plasma treatment was performed during the formation of the n-type amorphous silicon layer. When the n-type amorphous silicon layer was deposited to a thickness of 1.5 nm, the film formation was temporarily stopped and the gas in the chamber was exhausted. Next, hydrogen plasma treatment was performed for 60 seconds under the conditions of a substrate deposition surface-electrode distance of 10 mm, a pressure of 500 Pa, a plasma output of 0.04 W / cm ² , and an H 2 flow rate of 0.1 sccm / cm ² . After completion, the remaining thickness of the n-type amorphous silicon layer was 1.5 nm, which was different from Example 1.

[Comparative Example 1]
A hybrid thin-film solar cell was manufactured according to Example 1, but in Comparative Example 1, the n-type amorphous silicon layer of the crystalline photoelectric conversion unit was not formed, which is different from Example 1. It was.

  Table 1 shows the results of the evaluation of the output characteristics of the thin-film solar cells in Examples 1 and 2 and Comparative Example 1. In Table 1, the data of Comparative Example 1 is normalized based on the standard.

なお、Ｉｓｃは短絡電流、Ｖｏｃは開放電圧、ＦＦは曲線因子、及びＥｆｆは光電変換効率を表している。

Note that Isc represents a short circuit current, Voc represents an open circuit voltage, FF represents a fill factor, and Eff represents a photoelectric conversion efficiency.

  In Examples 1 and 2, the open-circuit voltage and the fill factor were improved compared to Comparative Example 1 both before and after curing, and a thin film solar cell with high photoelectric conversion efficiency was obtained. In this example, high photoelectric conversion efficiency was obtained not only after curing but also before curing. That is, a high open-circuit voltage and a fill factor were shown even without a curing treatment by introducing n-type amorphous silicon. Therefore, for example, when a polyolefin-based or ionomer-based resin sealing member is used, the curing process can be shortened.

DESCRIPTION OF SYMBOLS 1 Thin film solar cell 2 Board | substrate 3 1st electrode layer 5 Photoelectric conversion unit (photoelectric conversion layer)
6 Second electrode layer 7 Sealing member 11 Amorphous photoelectric conversion unit 12 Crystalline photoelectric conversion unit 15 p-type amorphous layer 16 i-type amorphous layer 17 n-type amorphous layer 18 p-type crystal layer 20 i Type crystal layer 21 n type amorphous layer 22 n type alloy layer 23 n type microcrystalline layer

Claims (8)

In a thin film solar cell in which at least a first electrode layer having translucency, a photoelectric conversion layer, and a second electrode layer are stacked on a substrate,
The photoelectric conversion layer has at least a crystalline photoelectric conversion unit,
The crystalline photoelectric conversion unit has a p-type crystal layer, an i-type crystal layer, and an n-type microcrystalline layer,
The p-type crystal layer is made of p-type microcrystalline silicon,
The i-type crystal layer is made of i-type crystalline silicon,
The n-type microcrystalline layer is formed of n-type microcrystalline silicon,
Between the i-type crystal layer and the n-type microcrystalline layer, an n-type amorphous layer and an n-type alloy layer are laminated in order from the i-type crystal layer side,
The n-type alloy layer is formed of a silicon alloy including one or more elements selected from oxygen, carbon, and nitrogen and a silicon element,
The n-type alloy layer is n-type microcrystalline silicon oxide,
n-type amorphous layer is a layer formed of an amorphous n-type semiconductor, a band gap than the i-type crystalline layer is rather large,
The thin-film solar cell, wherein the n-type amorphous layer is formed of n-type amorphous silicon . The thin film solar cell according to claim 1, wherein the n-type alloy layer has a thickness of 5 nm to 100 nm. The film thickness of the n-type amorphous layer, thin-film solar cell according to claim 1 or 2, characterized in that it is 0.1Nm～20nm. The thin film solar cell according to any one of claims 1 to 3 , wherein the film thickness of the n-type microcrystalline layer is 0.1 nm to 30 nm. The photoelectric conversion layer has an amorphous photoelectric conversion unit including a p-type amorphous layer, an i-type amorphous layer, and an n-type amorphous layer in addition to the crystalline photoelectric conversion unit,
The p-type amorphous layer is made of p-type amorphous silicon or p-type amorphous silicon carbide,
The i-type amorphous layer is made of i-type amorphous silicon,
The n-type amorphous layer, thin-film solar cell according to any one of claims 1 to 4, characterized in that it is formed from n-type amorphous silicon. The thin film solar cell according to any one of claims 1 to 5 , wherein the photoelectric conversion layer is laminated in the order of an amorphous photoelectric conversion unit and a crystalline photoelectric conversion unit from the substrate side. A method of manufacturing a thin film solar cell according to any of claims 1 to 6, the step of forming the n-type amorphous layer, that has a plasma processing step of performing hydrogen plasma treatment on the way of deposition A method for producing a thin-film solar cell. 8. The method of manufacturing a thin film solar cell according to claim 7 , wherein the plasma treatment step is performed when 30% to 70% of a target film thickness of the n-type amorphous layer is laminated.

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