WO2012036074A1 - Method for producing photovoltaic devices - Google Patents

Abstract

The purpose of the present invention is to provide a method for producing photovoltaic devices having high conversion efficiency, which minimize the occurrence of surface plasmon absorption in a rear electrode layer. A method for producing a photovoltaic device (100), in which a first transparent electrode layer (2), a photovoltaic layer (3), a second transparent electrode layer (5), and a rear electrode layer (4) comprising a metal film are sequentially laminated on a substrate (1), said method forming the second transparent electrode layer (5) by means of sputtering in a film forming chamber in which the vapor partial pressure is maintained at not more than 0.6%.

Description

Method for manufacturing photoelectric conversion device

The present invention relates to a method for manufacturing a photoelectric conversion device, and more particularly to a method for manufacturing a solar cell.

As a photoelectric conversion device that receives light and converts it into electric power, for example, a thin film solar cell in which a thin film silicon film is stacked on a power generation layer (photoelectric conversion layer) is known. A thin-film solar cell is generally configured by sequentially laminating a transparent electrode layer (first transparent electrode layer), a silicon-based semiconductor layer (photoelectric conversion layer), and a back electrode layer on a substrate.

The transparent electrode layer is mainly composed of a metal oxide such as zinc oxide (ZnO), tin oxide (SnO ₂ ), or indium tin oxide (ITO).
The back electrode layer is made of a metal film such as Ag or Al. Ag is considered to have better light reflection characteristics than Al. When an Ag film is laminated on a smooth glass substrate, an ideal high reflectance (R = about 98%) can be obtained.

In the field of thin film solar cells, various devices have been made to improve the open circuit voltage and the short circuit current in order to improve the battery performance.
For example, a tandem solar cell in which photoelectric conversion layers having different absorption wavelengths are stacked has been proposed. By making the photoelectric conversion layer a tandem type, incident light can be effectively absorbed, and a short circuit current and an open circuit voltage can be increased.

For example, by providing a transparent conductive film structure (intermediate reflective layer) with optimized film thickness between the upper photoelectric conversion layer and the lower photoelectric conversion layer, battery performance can be improved by inserting a new material layer at each layer interface. A way to improve it has been proposed.

Also, a method for improving the light transmission side structure (back surface structure) of the photoelectric conversion layer has been proposed. For example, Patent Document 1 describes a photoelectric conversion device in which a transparent electrode layer is provided between a photoelectric conversion layer and a back electrode layer. Through the transparent electrode layer, alloying between the semiconductor film and the metal film can be prevented. Thereby, since the metal film can maintain a high reflectance, a decrease in photoelectric conversion efficiency can be suppressed. For example, Patent Document 2 describes a photoelectric conversion device in which a low refractive index light-transmitting buffer layer is provided between a photoelectric conversion layer and a back electrode layer. In Patent Document 2, the back electrode layer (back electrode) is an Ag film.

Japanese Patent Publication No. 60-41878 (Claims) Japanese Patent No. 3342257 (Claim 1, paragraph [0020])

As in the photoelectric conversion devices proposed in Patent Document 1 and Patent Document 2, the improvement of the back surface structure focusing on the layer structure cannot sufficiently reduce the light absorption loss in the metal film.

When the transparent electrode layer on the back side and the back electrode layer (metal film) are sequentially stacked on the photoelectric conversion layer as the back surface structure, the shape of the substrate side surface of the metal film is the back side in contact with the metal film. Follow the shape of the surface of the transparent electrode layer. That is, if there are minute irregularities on the surface of the back side transparent electrode layer, the metal film is formed following the minute irregularities. Due to the presence of minute irregularities on the surface of the metal film, light absorption by surface plasmon resonance occurs on the surface of the metal film (hereinafter referred to as surface plasmon absorption). When surface plasmon absorption occurs, light that enters from the substrate side, passes through the photoelectric conversion layer, and reaches the back electrode layer is absorbed at the interface between the metal film and the back surface transparent electrode layer. The reflected light is reduced. As a result, the amount of light absorbed by the photoelectric conversion layer decreases and the generated current decreases (that is, the conversion efficiency decreases).

This invention is made | formed in view of such a situation, Comprising: It aims at providing the manufacturing method of the photoelectric conversion apparatus with high conversion efficiency which suppressed generation | occurrence | production of the surface plasmon absorption in a back surface electrode layer. .

In order to solve the above problems, the present invention provides a photoelectric device in which a first transparent electrode layer, a photoelectric conversion layer, a second transparent electrode layer, and a back electrode layer made of a metal film are sequentially laminated on a substrate. Provided is a method for manufacturing a conversion device, which is a method for manufacturing a photoelectric conversion device in which a second transparent electrode layer is formed in a film forming chamber in which a water vapor partial pressure is controlled to 0.6% or less.

As a result of intensive studies, the present inventors have found that the generated current can be increased by optimizing the surface shape of the back surface structure.
When forming the second transparent electrode layer, oxygen is introduced into the film forming chamber in order to make up for oxygen deficiency of the second transparent electrode layer and ensure transparency. However, by introducing oxygen, there arises a problem that the resistance of the second transparent electrode layer is increased and the surface smoothness is also impaired.
According to the above invention, by controlling the water vapor partial pressure in the film forming chamber to 0.6% or less, it is possible to prevent an increase in the series resistance of the second transparent electrode layer and to improve the surface smoothness. . If the increase in the resistance of the second transparent electrode layer is prevented, the reduction of the form factor can be prevented when the photoelectric conversion device is obtained. Further, when the smoothness of the surface of the second transparent electrode layer is improved, light absorption due to surface plasmon resonance on the surface of the metal film is reduced, so that the short-circuit current can be increased when the photoelectric conversion device is formed. Therefore, in such a photoelectric conversion device, the conversion efficiency is improved.

In one aspect of the above invention, it is preferable to introduce water vapor into the film forming chamber so that the water vapor partial pressure in the film forming chamber is 0.6% or less after reducing the water vapor partial pressure in the film forming chamber. .

In a vacuum apparatus, it is generally preferred that the moisture in the film forming chamber be as small as possible. On the contrary, the inventors of the present application propose to introduce water vapor into the film forming chamber as one method for controlling the water vapor partial pressure in the film forming chamber within an allowable range.
When film formation is performed in a state where the film formation chamber is evacuated, the partial pressure of water vapor in the film formation chamber changes during the film formation process. According to the above aspect, since the water vapor is introduced so that the water vapor partial pressure in the film forming chamber is once within the allowable range and then the desired partial pressure is obtained, the film forming conditions can be stabilized. Thereby, the quality of the second transparent electrode layer can be stabilized.

In one embodiment of the present invention, it is preferable to provide a step of annealing the back electrode layer at a temperature of 160 ° C. or higher and 220 ° C. or lower after forming the back electrode layer at a temperature of 40 ° C. or higher and 110 ° C. or lower.

According to one aspect of the invention, the metal film is formed at a temperature of 40 ° C. or higher and 110 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower, thereby smoothing the interface between the second transparent electrode layer and the back electrode layer. Sexual deterioration can be suppressed. Further, when the back electrode layer thus laminated is annealed at 160 ° C. or higher and 220 ° C. or lower, preferably 180 ° C. or higher and 210 ° C. or lower, the variation in the series resistance value is reduced, and the second transparent electrode layer and the back electrode layer are reduced. It is possible to improve the electrical connection between the two.

Moreover, this invention is a manufacturing method of the photoelectric conversion apparatus by which the 1st transparent electrode layer, a photoelectric converting layer, a 2nd transparent electrode layer, and the back surface electrode layer which consists of metal films are laminated | stacked in order on a board | substrate. A method for producing a photoelectric conversion device is provided in which the back electrode layer is formed at a temperature of 40 ° C. or higher and 110 ° C. or lower and then annealed at a temperature of 160 ° C. or higher and 220 ° C. or lower.

According to the above invention, the metal film deposition temperature is 40 ° C. or higher and 110 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower, and the annealing temperature is 160 ° C. or higher and 220 ° C. or lower, preferably 180 ° C. or higher. It shall be 210 degrees C or less. By doing so, the deterioration of the smoothness of the interface between the second transparent electrode layer and the back electrode layer can be prevented and the variation in the series resistance value can be reduced, so that the conversion efficiency of the photoelectric conversion device can be stabilized. Can be improved.

According to the present invention, by forming the second transparent electrode layer while controlling the water vapor partial pressure, a layer having transparency, surface smoothness, and low resistance can be obtained. In addition, after forming the back electrode layer at a low temperature, annealing is performed under appropriate conditions to prevent deterioration of the smoothness of the interface between the second transparent electrode layer and the back electrode layer, and the series resistance varies. Can be reduced. Therefore, a highly efficient photoelectric conversion device in which surface plasmon absorption hardly occurs can be manufactured.

It is the schematic showing the structure of the photoelectric conversion apparatus manufactured by the manufacturing method of the photoelectric conversion apparatus of this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel using the manufacturing method of the photoelectric conversion apparatus of this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel using the manufacturing method of the photoelectric conversion apparatus of this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel using the manufacturing method of the photoelectric conversion apparatus of this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel using the manufacturing method of the photoelectric conversion apparatus of this invention. It is the schematic explaining one Embodiment which manufactures a solar cell panel using the manufacturing method of the photoelectric conversion apparatus of this invention. It is a figure which shows the surface area increase rate of Example 1 and Reference Example 1. It is a figure which shows the relationship between a water vapor partial pressure and a short circuit current. It is a figure which shows the relationship between a water vapor partial pressure and an open circuit voltage. It is a figure which shows the relationship between water vapor partial pressure and a shape factor. It is a figure which shows the relationship between water vapor partial pressure and conversion efficiency. It is a figure which shows the relationship between water vapor partial pressure and series resistance. It is the figure which expanded the vertical axis | shaft of FIG. It is the figure which expanded the vertical axis | shaft of FIG. It is the figure which expanded the vertical axis | shaft of FIG. It is the figure which expanded the vertical axis | shaft of FIG. FIG. 6 is a diagram showing the reflectance of Example 3. It is a figure which shows the relationship between annealing temperature and a short circuit current. It is a figure which shows the relationship between annealing temperature and an open circuit voltage. It is a figure which shows the relationship between annealing temperature and a shape factor. It is a figure which shows the relationship between annealing temperature and conversion efficiency. It is a figure which shows the relationship between annealing temperature and series resistance.

FIG. 1 is a schematic diagram showing the configuration of a photoelectric conversion device manufactured by the method for manufacturing a photoelectric conversion device of the present invention. The photoelectric conversion device 100 is a tandem silicon solar cell, and includes a substrate 1, a first transparent electrode layer 2, a first cell layer 91 (amorphous silicon system) and a second cell layer as the solar cell photoelectric conversion layer 3. 92 (crystalline silicon type), an intermediate contact layer 93, a second transparent electrode layer 5, and a back electrode layer 4. Here, the silicon-based is a generic name including silicon (Si), silicon carbide (SiC), and silicon germanium (SiGe). Further, the crystalline silicon system means a silicon system other than the amorphous silicon system, and includes microcrystalline silicon and polycrystalline silicon.

<First Embodiment>
A method for manufacturing a photoelectric conversion device according to the first embodiment will be described by taking a process for manufacturing a solar cell panel as an example. 2 to 6 are schematic views showing a method for manufacturing the solar cell panel of the present embodiment.

(1) FIG. 2 (a)
As the substrate 1, a large soda float glass substrate (for example, 1.4 m × 1.1 m × plate thickness: 3.0 mm to 6.0 mm) having an area exceeding 1 m ² is used. The end face of the substrate is preferably subjected to corner chamfering or R chamfering to prevent damage due to thermal stress or impact.

(2) FIG. 2 (b)
As the first transparent electrode layer 2, a transparent conductive film having a thickness of about 500 nm to 800 nm and having tin oxide (SnO ₂ ) as a main component is formed at about 500 ° C. with a thermal CVD apparatus. At this time, a texture with appropriate irregularities is formed on the surface of the transparent electrode film. As the first transparent electrode layer 2, in addition to the transparent electrode film, an alkali barrier film (not shown) may be formed between the substrate 1 and the transparent electrode film. As the alkali barrier film, a silicon oxide film (SiO ₂ ) is formed at a temperature of about 500 ° C. with a thermal CVD apparatus at 50 nm to 150 nm.

(3) FIG. 2 (c)
Thereafter, the substrate 1 is set on an XY table, and the first harmonic (1064 nm) of the YAG laser is irradiated from the film surface side of the transparent electrode film as indicated by an arrow in the figure. The laser power is adjusted so as to be suitable for the processing speed, and the transparent electrode film is moved relative to the direction perpendicular to the series connection direction of the power generation cells 7 to move the substrate 1 and the laser beam to form the groove 10. Thus, laser etching is performed in a strip shape having a predetermined width of about 6 mm to 15 mm.

(4) FIG. 2 (d)
As the first cell layer 91, a p layer, an i layer, and an n layer made of an amorphous silicon thin film are formed by a plasma CVD apparatus. Using SiH ₄ gas and H ₂ gas as main raw materials, amorphous silicon p from the incident side of sunlight on the first transparent electrode layer 2 at a reduced pressure atmosphere: 30 Pa to 1000 Pa, substrate temperature: about 200 ° C. The layer 31, the amorphous silicon i layer 32, and the amorphous silicon n layer 33 are formed in this order. The amorphous silicon p layer 31 is mainly made of amorphous B-doped silicon and has a thickness of 10 nm to 30 nm. The amorphous silicon i layer 32 has a thickness of 200 nm to 350 nm. The amorphous silicon n layer 33 is mainly P-doped silicon containing microcrystalline silicon in amorphous silicon, and has a thickness of 30 nm to 50 nm. A buffer layer may be provided between the amorphous silicon p layer 31 and the amorphous silicon i layer 32 in order to improve interface characteristics.

Next, a crystalline material as the second cell layer 92 is formed on the first cell layer 91 by a plasma CVD apparatus at a reduced pressure atmosphere: 3000 Pa or less, a substrate temperature: about 200 ° C., and a plasma generation frequency: 40 MHz or more and 100 MHz or less. A silicon p layer 41, a crystalline silicon i layer 42, and a crystalline silicon n layer 43 are sequentially formed. The crystalline silicon p layer 41 is mainly made of B-doped microcrystalline silicon and has a thickness of 10 nm to 50 nm. The crystalline silicon i layer 42 is mainly made of microcrystalline silicon and has a film thickness of 1.2 μm or more and 3.0 μm or less. The crystalline silicon n layer 43 is mainly made of P-doped microcrystalline silicon and has a thickness of 20 nm to 50 nm. The crystalline silicon n layer may be replaced with an amorphous silicon n layer.

In forming the i-layer film mainly composed of microcrystalline silicon by the plasma CVD method, the distance d between the plasma discharge electrode and the surface of the substrate 1 is preferably 3 mm or more and 10 mm or less. If it is smaller than 3 mm, it is difficult to keep the distance d constant from the accuracy of each component device in the film forming chamber corresponding to the large substrate, and there is a possibility that the discharge becomes unstable because it is too close. When it is larger than 10 mm, it is difficult to obtain a sufficient film forming speed (1 nm / s or more), and the uniformity of the plasma is lowered and the film quality is lowered by ion bombardment.

An intermediate contact layer 93 serving as a semi-reflective film is provided between the first cell layer 91 and the second cell layer 92 in order to improve the contact property and obtain current matching. As the intermediate contact layer 93, a ZnO film doped with Ga or Al having a film thickness of 20 nm to 100 nm is formed by sputtering using a target: Ga-doped ZnO sintered body or Al-doped ZnO sintered body. Further, the intermediate contact layer 93 may not be provided.

(5) FIG. 2 (e)
The substrate 1 is placed on an XY table, and the second harmonic (532 nm) of the laser diode-pumped YAG laser is irradiated from the film surface side of the photoelectric conversion layer 3 as shown by the arrow in the figure. Pulse oscillation: 10 kHz to 20 kHz, the laser power is adjusted so as to be suitable for the processing speed, and the groove 11 is formed on the lateral side of about 100 μm to 150 μm of the laser etching line of the first transparent electrode layer 2. Laser etching. Further, this laser may be irradiated from the substrate 1 side. In this case, since the photoelectric conversion layer 3 can be etched using a high vapor pressure generated by the energy absorbed by the photoelectric conversion layer 3, further stable laser etching is possible. Processing can be performed. The position of the laser etching line is selected in consideration of positioning tolerances so as not to intersect with the etching line in the previous process.

(6) FIG. 3 (a)
On the crystalline silicon n layer 43 of the second cell layer 92, the second transparent electrode layer 5 and the back electrode layer 4 are formed in this order. Note that FIG. 3 is a diagram mainly for explaining a groove forming method, and therefore the description of the second transparent electrode layer 5 in which the groove is formed simultaneously with the back electrode layer 4 is omitted.
As the second transparent electrode layer 5, a GZO film is formed by a sputtering apparatus. Film forming conditions are: target: Ga-doped ZnO sintered body, reduced pressure atmosphere: 0.67 Pa, discharge gas: argon, film thickness: 50 nm to 150 nm, film forming temperature: 20 ° C. to 90 ° C., preferably 20 ° C. or higher 60 ° C. or lower.

The film formation of the second transparent electrode layer 5 is performed in the film forming chamber. During film formation, the water vapor partial pressure in the film formation chamber is controlled to 0.6% or less. As a control method, for example, before starting the film formation, the film forming chamber is evacuated so that the water vapor partial pressure is 0.6% or less, and then a partial pressure gauge is used so that the water vapor partial pressure does not exceed 0.6%. Used to monitor the partial pressure of water vapor in the deposition chamber. For example, before starting the film formation, the film formation chamber is evacuated so that the water vapor partial pressure is a predetermined value or less, and then the discharge gas is set so that the desired water vapor partial pressure (an arbitrary value of 0.6% or less) is obtained. Steam is introduced into the deposition chamber.
The method for controlling the water vapor partial pressure is not limited to the above method, and any method can be used as long as the water vapor partial pressure in the film forming chamber during film formation can be maintained at 0.6% or less.

As the back electrode layer 4, an Ag film is formed by a sputtering apparatus at a discharge gas of argon and a film forming temperature of about 150 ° C. Alternatively, as the back electrode layer 4, an Ag film: 200 nm to 500 nm, and a Ti film having a high anticorrosive effect as a protective film: 10 nm to 20 nm may be laminated in this order to form an Ag film / Ti film laminated film. good. In this case, the layer structure is such that an Ag film is provided on the substrate side.

(7) FIG. 3 (b)
The substrate 1 is placed on an XY table, and the second harmonic (532 nm) of the laser diode-pumped YAG laser is irradiated from the substrate 1 side as indicated by the arrow in the figure. The laser light is absorbed by the photoelectric conversion layer 3, and the back electrode layer 4 is exploded and removed using the high gas vapor pressure generated at this time. Pulse oscillation: laser power is adjusted so that the processing speed is appropriate from 1 kHz to 50 kHz, and a laser is formed so that grooves 12 are formed on the lateral side of the laser etching line of the first transparent electrode layer 2 from 250 μm to 400 μm. Etch.

(8) FIG. 3 (c) and FIG. 4 (a)
The power generation region is divided, and the film edge around the substrate edge is laser-etched to prevent a short circuit at the serial connection portion. The substrate 1 is set on an XY table, and the second harmonic (532 nm) of the laser diode pumped YAG laser is irradiated from the substrate 1 side. The laser light is absorbed by the first transparent electrode layer 2 and the photoelectric conversion layer 3, and the back electrode layer 4 explodes using the high gas vapor pressure generated at this time, and the back electrode layer 4 / photoelectric conversion layer 3 / 1 The transparent electrode layer 2 is removed. Pulse oscillation: 1 kHz or more and 50 kHz or less, the laser power is adjusted so as to be suitable for the processing speed, and the position of 5 mm to 20 mm from the end of the substrate 1 is placed in the X-direction insulating groove as shown in FIG. Laser etching is performed to form 15. In addition, in FIG.3 (c), since it becomes X direction sectional drawing cut | disconnected in the direction in which the photoelectric converting layer 3 was connected in series, the back surface electrode layer 4 / photoelectric conversion is originally in the position of the insulating groove 15 A state (see FIG. 4A) corresponding to the peripheral film removal region 14 where the layer 3 / the first transparent electrode layer 2 has been removed by polishing should appear, but the processing to the end of the substrate 1 For the sake of convenience, the insulating groove formed to represent the Y-direction cross section at this position will be described as the X-direction insulating groove 15. At this time, the Y-direction insulating groove does not need to be provided because the film surface polishing removal processing of the peripheral film removal region of the substrate 1 is performed in a later process.

The insulating groove 15 has an effective effect in suppressing moisture permeation from the outside into the solar cell module 6 from the end of the solar cell panel by terminating the etching at a position of 5 mm to 15 mm from the end of the substrate 1. This is preferable.

In addition, although the laser beam in the above steps is a YAG laser, there are some that can use a YVO4 laser or a fiber laser in the same manner.

(9) FIG. 4 (a: view from the solar cell film side, b: view from the substrate side of the light receiving surface)
Since the laminated film around the substrate 1 (peripheral film removal region 14) has a step and is easy to peel off in order to ensure a sound adhesion / seal surface with the back sheet 24 via EVA or the like in a later process, The film is removed to form a peripheral film removal region 14. In removing the film over the entire circumference of the substrate 1 at 5 mm to 20 mm from the end of the substrate 1, the X direction is closer to the substrate end than the insulating groove 15 provided in the step of FIG. The back electrode layer 4 / photoelectric conversion layer 3 / first transparent electrode layer 2 are removed by using grinding stone polishing, blast polishing, or the like on the substrate end side with respect to the groove 10 near the side portion.
Polishing debris and abrasive grains are removed by cleaning the substrate 1.

(10) FIG. 4 (a) (b)
A solar cell is obtained by collecting current from the back electrode layer 4 of the power generation cell 7 at one end and the back electrode layer 4 of the current collecting cell connected to the power generation cell 7 at the other end using a copper foil. It processes so that electric power can be taken out from the part of the terminal box 23 of a panel back side. In order to prevent short circuit with each part, the copper foil for current collection arrange | positions an insulating sheet wider than copper foil width.
After the current collecting copper foil or the like is disposed at a predetermined position, an adhesive filler sheet made of EVA (ethylene vinyl acetate copolymer) or the like is disposed so as to cover the entire solar cell module 6 and not protrude from the substrate 1. .
A back sheet 24 having a high waterproofing effect is installed on the adhesive filler sheet. In this embodiment, the back sheet 24 has a three-layer structure of PET sheet / Al foil / PET sheet so that the waterproof and moisture-proof effect is high.
An opening through window is provided at the attachment portion of the terminal box 23 of the back sheet 24 to take out the copper foil for current collection. In the opening through window portion, an insulating material is provided in a plurality of layers between the back sheet 24 and the back electrode layer 4 to suppress intrusion of moisture and the like from the outside.
The adhesive sheet (EVA) is cross-linked with the back sheet 24 placed in place while the inside is degassed in a reduced pressure atmosphere with a laminator device and pressed at about 150 ° C to about 160 ° C. , Seal.
The adhesive filler sheet is not limited to EVA, and an adhesive filler having a similar function such as PVB (polyvinyl butyral) can be used. In this case, the processing is performed by optimizing the conditions such as the pressure bonding procedure, temperature and time.

(11) FIG. 5 (a)
The terminal box 23 is attached to the back side of the solar cell module 6 with an adhesive.
(12) FIG. 5 (b)
The copper foil and the output cable of the terminal box 23 are connected by solder or the like, and the inside of the terminal box 23 is filled with a sealing agent (potting agent) and sealed. Thus, the solar cell panel 50 is completed.
(13) FIG. 5 (c)
A power generation inspection and a predetermined performance test are performed on the solar cell panel 50 formed in the steps up to FIG. The power generation inspection is performed using a solar simulator of AM1.5 and solar radiation standard sunlight (1000 W / m ² ). The power generation inspection may be performed after the solar battery panel 50 is completely completed, or may be performed before the aluminum frame frame is attached.
(14) FIG. 5 (d)
Before and after the power generation inspection (FIG. 5C), a predetermined performance inspection is performed including an appearance inspection.

(15) FIG.
An aluminum frame frame that adds strength to the solar cell module 6 and serves as a mounting seat is attached around the solar cell module 6. It is preferable to securely hold the solar cell module 6 and the aluminum frame frames 103L and 103S through rubber gaskets or the like while maintaining elasticity.
Thus, the solar cell panel 50 is completed.

(Smoothness, transparency and sheet resistance)
Example 1
A 0.5 wt% Ga-doped ZnO film (GZO film) was formed on a glass substrate using a DC sputtering apparatus. Before film formation, the film formation chamber was evacuated for 2.5 hours, and then the opening of the variable leak valve was adjusted from the water vapor tank, so that the water vapor partial pressure in the film formation chamber was 0.3%. Then, it formed into a target: Ga dope ZnO sintered compact, discharge gas: Argon and water vapor | steam (0.2 volume%), film thickness: 100 nm, and film forming temperature: 60 degreeC.

Reference example 1
As a discharge gas, oxygen (0.5% by volume) was introduced instead of water vapor, and GZO films having film thicknesses of 50 nm, 70 nm, and 100 nm were formed on a glass substrate. Conditions other than the above were the same as in Example 1.

For Example 1 and Reference Example 1, the surface shape was AFM (Digital Instruments, NanoScope D-3100), viewing angle: 2 μm × 2 μm, resolution: 512 pixels, Z range: 100 nm / div or 500 nm / Two fields of view of the same sample were observed in div and tapping modes. The average value of the surface area increase rate was obtained from the obtained AFM image.

FIG. 7 shows the surface area increase rate of Example 1 and Reference Example 1. In the figure, the vertical axis represents the surface area increase ΔS, and the horizontal axis represents the GZO film thickness. According to FIG. 7, the surface area of Example 1 did not increase as compared with Reference Example 1. From the above results, it was confirmed that the surface smoothness of the GZO film was improved by adding water vapor without adding oxygen as a discharge gas.

Further, for Example 1 and Reference Example 1, the transmittance and the reflectance were measured using a spectrophotometer. In the wavelength region from 400 nm to 1300 nm, the sum of the light transmittance and the light reflectance in Example 1 showed the same value as in Reference Example 1.

Further, for Example 1 and Reference Example 1, the sheet resistance of the GZO film was measured with a 4-terminal resistance measuring instrument. The sheet resistance of the GZO film of Example 1 showed a tendency to be lower than that of Reference Example 1.

(Solar cell performance)
Example 2
Using a glass substrate 1 (140 cm × 110 cm × plate thickness 4 mm), a tandem solar cell was produced according to the above embodiment.
Transparent electrode layer 2: tin oxide film, average film thickness 700 nm
Amorphous silicon p layer: Average film thickness 20 nm
Amorphous silicon i layer: Average film thickness 300 nm
Amorphous silicon n layer: Average film thickness 40 nm
Intermediate contact layer 93: GZO film / average film thickness 50 nm
Crystalline silicon p layer: Average film thickness 30 nm
Crystalline silicon i layer: Average film thickness 2000 nm
Crystalline silicon n layer: Average film thickness 30 nm
Second transparent electrode layer 5: GZO film / average film thickness 100 nm
Back electrode layer 4: Ag film / average film thickness 300 nm

The second transparent electrode layer 5 was formed using a DC sputtering apparatus with a target: Ga-doped ZnO sintered body, a reduced pressure atmosphere: 0.67 Pa, a discharge gas: argon and water vapor, and a film forming temperature: 60 ° C. The water vapor partial pressure in the film forming chamber was measured so that the water vapor partial pressure in the film forming chamber during film formation was 0.1% to 0.9%, and an appropriate amount of water vapor was appropriately introduced.

The back electrode layer 4 was formed by a DC sputtering apparatus at a reduced pressure atmosphere: 0.67 Pa, a target: Ag, a discharge gas: argon, and a film forming temperature: about 135 ° C.

Reference example 2
A tandem solar cell was produced in the same manner as in Example 2 except that the film forming conditions of the second transparent electrode layer 5 were different.
In the film formation of the second transparent electrode layer 5, the water vapor partial pressure in the film formation chamber before film formation is changed from 0.1% to 0.3%, and oxygen (0.5 volume) is used instead of water vapor as a discharge gas. %) Was introduced.

Reference example 3
A tandem solar cell was produced in the same manner as in Example 2 except that the film forming conditions of the second transparent electrode layer 5 were different.
In the film formation of the second transparent electrode layer 5, the film formation chamber is evacuated for 24 hours before film formation, and the water vapor partial pressure in the film formation chamber is reduced to 0.1% or less, and then, instead of water vapor as a discharge gas. Oxygen (1% by volume) was introduced.

For Example 2, Reference Example 2 and Reference Example 3, the short circuit current (Jsc), open circuit voltage (Voc), form factor (FF), conversion efficiency (Eff), and series resistance (Rs) were measured.
The measurement results are shown in FIGS. In FIG. 8, the horizontal axis represents the water vapor partial pressure, and the vertical axis represents Jsc. In FIG. 9, the horizontal axis represents the water vapor partial pressure, and the vertical axis represents Voc. In FIG. 10, the horizontal axis represents the water vapor partial pressure, and the vertical axis represents FF. In FIG. 11, the horizontal axis represents the water vapor partial pressure, and the vertical axis represents Eff. In FIG. 12, the horizontal axis represents the water vapor partial pressure, and the vertical axis represents Rs.

The short circuit current and the shape factor of Example 2, Reference Example 2 and Reference Example 3 showed a tendency to greatly decrease when the water vapor partial pressure exceeded 0.6%. At the open circuit voltage, no significant change depending on the water vapor partial pressure was observed. The conversion efficiencies of Example 2, Reference Example 2 and Reference Example 3 also decreased when the water vapor partial pressure exceeded 0.6%.
Moreover, the series resistance of Example 2, Reference Example 2 and Reference Example 3 showed a tendency to increase when the water vapor partial pressure exceeded 0.6%.
From the above results, it was found that the water vapor partial pressure in the film forming chamber is preferably 0.6% or less.

FIGS. 13 to 16 show graphs in which the vertical axis of FIGS. 8 and 10 to 12 is enlarged. According to FIG. 13, when the water vapor partial pressure was increased within a range of 0.6% or less, there was a tendency for the short-circuit current to increase. Further, in Example 2, Reference Example 2 and Reference Example 3, the short circuit current tended to increase as the amount of oxygen introduced was smaller. In particular, Example 2 produced by controlling the water vapor partial pressure to 0.5% increased 1.04 times compared to Reference Example 3. This is a great value for improving the short circuit current.

FIG. 14 shows that the form factor tends to decrease by increasing the water vapor partial pressure in the range of 0.6% or less. On the other hand, the conversion efficiency increased (FIG. 15). This is considered due to the fact that the short-circuit current value is greatly improved.

FIG. 16 shows that in the range of 0.6% or less, the increase in series resistance can be prevented even if the water vapor partial pressure is increased.

From the above results, it was confirmed that by forming the film according to this embodiment, the second transparent electrode layer having transparency, high surface shape smoothness and low resistance was obtained.

Second Embodiment
The second embodiment is the same as the first embodiment except that the formation conditions of the second transparent electrode layer 5 and the back electrode layer 4 are different.
As the second transparent electrode layer 5, a GZO film is formed by a sputtering apparatus. Film forming conditions are: target: Ga-doped ZnO sintered body, reduced pressure atmosphere: 0.67 Pa, discharge gas: argon, oxygen (0.5% by volume), film thickness: 50 nm to 150 nm, film forming temperature: 60 ° C. or lower It is said.

As the back electrode layer 4, an Ag film having a film thickness of 200 nm or more and 500 nm or less is formed by a sputtering apparatus with a discharge gas: argon, a film forming temperature: 40 ° C. or higher and 110 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower. To do. Alternatively, as the back electrode layer 4, an Ag film: 200 nm to 500 nm, and a Ti film having a high anticorrosive effect as a protective film: 10 nm to 20 nm may be laminated in this order to form an Ag film / Ti film laminated film. good. In this case, the layer structure is such that an Ag film is provided on the substrate side.
After forming the Ag film, annealing is performed in a nitrogen atmosphere at a temperature of 160 ° C. to 220 ° C. and a processing time of 0.5 hour to 2 hours.

(Optical reflection characteristics)
Example 3
A 0.5 wt% Ga-doped ZnO film (GZO film) was formed on a glass substrate using a DC sputtering apparatus. The film forming conditions were as follows: target: Ga-doped ZnO sintered body, film forming temperature: 60 ° C., reduced pressure atmosphere: 0.67 Pa, discharge gas: argon and oxygen (0.5% by volume). Before film formation, the film formation chamber was evacuated, and the water vapor partial pressure in the film formation chamber was set to 0.2%.
On the GZO film, the back electrode layer 4 was formed by a DC sputtering apparatus at a reduced pressure atmosphere: 0.67 Pa, a target: Ag, a discharge gas: argon, and a film forming temperature: 100 ° C. After film formation, annealing was performed at a temperature of 160 ° C., 180 ° C., 200 ° C., or 220 ° C. for 45 minutes in a nitrogen atmosphere.

Reference example 4
It was produced in the same manner as in Example 3 except that the film formation temperature of the back electrode layer 4 was different. The film forming temperature was 135 ° C.

For Example 3 and Reference Example 4, the reflectance at wavelengths from 300 nm to 1500 nm was measured. Example 3 and Reference Example 4 showed substantially the same reflectance. In FIG. 17, the reflectance of Example 3 is shown. According to FIG. 17, in Example 3, there was a tendency that the reflectance was improved as the annealing temperature was higher.

(Solar cell performance)
Example 4
Using a glass substrate 1 (140 cm × 110 cm × plate thickness 4 mm), a tandem solar cell was produced according to the above embodiment.
Transparent electrode layer 2: tin oxide film, average film thickness 700 nm
Amorphous silicon p layer: Average film thickness 20 nm
Amorphous silicon i layer: Average film thickness 300 nm
Amorphous silicon n layer: Average film thickness 40 nm
Intermediate contact layer 93: GZO film / average film thickness 50 nm
Crystalline silicon p layer: Average film thickness 30 nm
Crystalline silicon i layer: Average film thickness 2000 nm
Crystalline silicon n layer: Average film thickness 30 nm
Second transparent electrode layer 5: GZO film / average film thickness 100 nm
Back electrode layer 4: Ag film / average film thickness 300 nm

The second transparent electrode layer 5 uses a DC sputtering apparatus, target: Ga-doped ZnO sintered body, reduced pressure atmosphere: 0.67 Pa, discharge gas: argon and oxygen (0.5% by volume), film forming temperature: 60 ° C. To form a film. Before film formation, the film formation chamber was evacuated, and the water vapor partial pressure in the film formation chamber was set to 0.2%.

The back electrode layer 4 was formed by a DC sputtering apparatus at a reduced pressure atmosphere: 0.67 Pa, a target: Ag, a discharge gas: argon, and a film forming temperature: 100 ° C. After film formation, annealing was performed at a temperature of 160 ° C., 180 ° C., 200 ° C., or 220 ° C. for 45 minutes in a nitrogen atmosphere.

Reference Example 5
A tandem solar cell was produced in the same manner as in Example 3 except that the film formation temperature of the back electrode layer was different. The film forming temperature was 135 ° C.

For Example 4 and Reference Example 5, the short circuit current (Jsc), the open circuit voltage (Voc), the form factor (FF), the conversion efficiency (Eff), and the series resistance (Rs) were measured.
The measurement results are shown in FIGS. In FIG. 18, the horizontal axis represents the annealing temperature, and the vertical axis represents Jsc. In FIG. 19, the horizontal axis represents the annealing temperature, and the vertical axis represents Voc. In FIG. 20, the horizontal axis represents the annealing temperature, and the vertical axis represents FF. In FIG. 21, the horizontal axis represents the annealing temperature, and the vertical axis represents Eff. In FIG. 22, the horizontal axis represents the annealing temperature, and the vertical axis represents Rs.

Compared to Reference Example 5, the short-circuit current was higher in Example 4 regardless of the annealing temperature. The open-circuit voltage and the shape factor were constant in Reference Example 5 regardless of the annealing temperature, but Example 4 showed a maximum at an annealing temperature of 200 ° C. Moreover, the conversion efficiency of Example 4 became maximum at an annealing temperature of 200 ° C. The conversion efficiency of Example 4 produced at an annealing temperature of 200 ° C. was 1.06 times higher than that of Reference Example 5 produced at the same annealing temperature.
The series resistance of Example 4 was minimal at an annealing temperature of 200 ° C. In addition, the variation in series resistance in Example 4 was smaller than that in Reference Example 5.

<Third Embodiment>
It is the same as that of 1st Embodiment except the formation conditions of the back surface electrode layer 4 differing.
In the present embodiment, as the back electrode layer 4, a sputtering apparatus is used to discharge gas: argon, film forming temperature: 40 ° C. or higher and 110 ° C. or lower, preferably 60 ° C. or higher and 100 ° C. or lower, and film thickness: 200 nm or higher and 500 nm or lower. An Ag film is formed. Alternatively, as the back electrode layer 4, an Ag film: 200 nm to 500 nm, and a Ti film having a high anticorrosive effect as a protective film: 10 nm to 20 nm may be laminated in this order to form an Ag film / Ti film laminated film. good. In this case, the layer structure is such that an Ag film is provided on the substrate side.
After forming the Ag film, annealing is performed in a nitrogen atmosphere at a temperature of 160 ° C. to 220 ° C. and a processing time of 0.5 hour to 2 hours.

According to the present embodiment, the Ag film can be prevented from being coarsened by forming the Ag film at an appropriate temperature, and therefore, the Ag film having a surface that follows the surface shape of the second transparent electrode layer 5 can be obtained. it can. Thereby, it is possible to prevent the smoothness of the interface between the second transparent electrode layer 5 and the back electrode layer 4 from being deteriorated.
Further, by annealing the Ag film formed at an appropriate temperature at an appropriate temperature, variation in series resistance can be reduced. Thereby, the conversion efficiency can be stably improved.

In the first to third embodiments, the tandem solar cell has been described as the solar cell, but the present invention is not limited to this example. For example, the present invention can be similarly applied to other types of thin film solar cells such as crystalline silicon solar cells including microcrystalline silicon, silicon germanium solar cells, single type solar cells, and triple type solar cells.

The shape of the surface on the back electrode layer 4 side of the second transparent electrode layer 5 in the solar cell according to the first to third embodiments is such that the back electrode layer 4 is removed by chemical removal or peeling using a chemical, for example. This can be confirmed by exposing the second transparent electrode layer 5 and observing it using AFM or FESEM.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 1st transparent electrode layer 3 Photoelectric conversion layer 4 Back surface electrode layer 5 2nd transparent electrode layer 6 Solar cell module 7 Power generation cell 31 Amorphous silicon p layer 32 Amorphous silicon i layer 33 Amorphous silicon n layer 41 crystalline silicon p layer 42 crystalline silicon i layer 43 crystalline silicon n layer 91 first cell layer 92 second cell layer 93 intermediate contact layer 100 photoelectric conversion device

Claims (4)

A method of manufacturing a photoelectric conversion device in which a first transparent electrode layer, a photoelectric conversion layer, a second transparent electrode layer, and a back electrode layer made of a metal film are sequentially stacked on a substrate,
A method for manufacturing a photoelectric conversion device, wherein a second transparent electrode layer is formed in a film forming chamber in which a water vapor partial pressure is controlled to 0.6% or less. 2. The photoelectric conversion device according to claim 1, wherein after reducing the water vapor partial pressure in the film forming chamber, the water vapor is introduced into the film forming chamber so that the water vapor partial pressure in the film forming chamber is 0.6% or less. Production method. The method for producing a photoelectric conversion device according to claim 1, wherein the back electrode layer is formed at a temperature of 40 ° C. or higher and 110 ° C. or lower and then annealed at a temperature of 160 ° C. or higher and 220 ° C. or lower. A method of manufacturing a photoelectric conversion device in which a first transparent electrode layer, a photoelectric conversion layer, a second transparent electrode layer, and a back electrode layer made of a metal film are sequentially stacked on a substrate,
The manufacturing method of the photoelectric conversion apparatus which anneals at 160 degreeC or more and 220 degrees C or less, after forming the said back surface electrode layer into 40 to 110 degreeC.

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