JP5254917B2 - Method for manufacturing photoelectric conversion device - Google Patents

Description

  The present invention relates to a photoelectric conversion device, and more particularly to a method for manufacturing a thin-film solar cell in which a power generation layer is formed by film formation, and a solar cell.

  As a photoelectric conversion device that converts sunlight energy into electric energy, plasma CVD is performed on thin films of p-type silicon semiconductor (p layer), i-type silicon semiconductor (i layer), and n-type silicon semiconductor (n layer). 2. Description of the Related Art A thin film silicon solar cell including a photoelectric conversion layer formed by a method or the like is known. Advantages of the thin-film silicon-based solar cell include that the area can be easily increased, the film thickness is as thin as about 1/100 that of a crystalline solar cell, and the material can be reduced. For this reason, the thin film silicon solar cell can be manufactured at a lower cost than the crystalline solar cell.

  Solar cell structures include a superstrate type in which light is incident from the substrate side and a substrate type in which light is incident from the surface opposite to the substrate. In the super straight type solar cell, a transparent electrode layer is formed on a transparent substrate, and a photoelectric conversion layer is formed thereon. The super straight type solar cell has an advantage that it is easy to integrate a large area thin film solar cell and is excellent in productivity. However, reflection loss occurs at the substrate / transparent electrode layer interface and at the transparent electrode layer / photoelectric conversion layer interface due to the refractive index relationship of the material applied to each layer.

  In Patent Document 1, by providing titanium oxide as a refractive index adjusting layer at the interface between the transparent electrode layer (tin oxide) and the photoelectric conversion layer (amorphous silicon), reflection at the interface is reduced. It has been disclosed to improve output current and conversion efficiency.

  Patent Document 2 discloses that an antireflection layer including a titanium oxide layer and a zinc oxide layer is provided between a transparent electrode layer and a photoelectric conversion layer. The zinc oxide layer has a function of preventing the titanium oxide layer from being reduced by the plasma containing hydrogen when the photoelectric conversion layer is formed, and the transmittance of visible light being lowered. In order to achieve both the antireflection function and the reduction prevention function of the zinc oxide layer, the film thickness of the titanium oxide layer of Patent Document 2 is 10 to 100 nm, and the titanium oxide layer is 1 to 50 nm, preferably 5 to 20 nm.

Japanese Patent No. 2939780 (Claim 1, paragraphs [0009] and [0015], FIG. 1) JP 2005-244073 A (Claim 1, paragraphs [0035] [0038] [0039] [0043])

  In the solar cell described in Patent Document 2, the zinc oxide layer is effective as a protective film for the titanium oxide layer, but is not optically present in order to increase reflection at the interface of the titanium oxide layer / zinc oxide layer. Is advantageous. Therefore, the titanium oxide layer has a minimum thickness having a function as a protective film, and suppresses reflection between the transparent electrode layer and the photoelectric conversion layer to increase the output of the solar cell. And it is necessary to design each film thickness of a zinc oxide layer.

  The present invention provides a method for producing a photoelectric conversion device that has good plasma reduction resistance and can suppress reflection loss between the transparent electrode layer and the photoelectric conversion layer, and a photoelectric device with improved battery characteristics. An object is to provide a conversion device.

  The present invention provides a method for manufacturing a photoelectric conversion device, in which a transparent electrode layer, a titanium oxide layer mainly containing titanium oxide, a zinc oxide layer mainly containing zinc oxide, and a photoelectric conversion layer are sequentially formed on a substrate. A weight function that is a product of a spectrum of incident light and a quantum efficiency of the photoelectric conversion layer, a spectrum of light that passes through the titanium oxide layer and the zinc oxide layer having a predetermined thickness, and the calculation The average transmittance of light transmitted through the titanium oxide layer and the zinc oxide layer having the predetermined thickness is calculated from the weight function thus calculated, and the calculated average transmittance and reduction prevention of the titanium oxide layer are calculated. Provided is a method for manufacturing a photoelectric conversion device that determines the thickness of the titanium oxide layer to be formed and the thickness of the zinc oxide layer based on the thickness range of the zinc oxide layer in consideration of the effect.

In order to increase the output of the photoelectric conversion device, particularly in the wavelength region where the quantum efficiency of the photoelectric conversion device is high, the reflection loss between the transparent electrode layer and the photoelectric conversion layer is reduced, and the photoelectric conversion layer is changed from the transparent electrode layer to the photoelectric conversion layer. It is effective to increase the amount of light incident on the light. In the present invention, a weight function that is a product of quantum efficiency and sunlight spectrum is used to calculate the average transmittance of light transmitted through the titanium oxide layer and the zinc oxide layer. That is, the film thicknesses of the titanium oxide layer and the zinc oxide layer determined using the present invention reflect the quantum efficiency and the sunlight spectrum. Therefore, it is possible to accurately obtain a combination of the thicknesses of the titanium oxide layer and the zinc oxide layer that have the plasma reduction resistance and can increase the short-circuit current.
The weight function can be obtained in correspondence with the structure of the photoelectric conversion layer such as a single type, a tandem type, or a triple type and a material used for the photoelectric conversion layer. Therefore, a photoelectric conversion device having various photoelectric conversion layers can be designed and manufactured so as to increase the amount of light incident on the photoelectric conversion layer and increase the short-circuit current to obtain a high output.

  In the said invention, when the reduction | restoration prevention effect of a titanium oxide layer is considered, it is preferable that the film thickness of the said zinc oxide layer shall be 1 nm or more and 20 nm or less.

A reference example of the present invention is a photoelectric conversion device including, on a substrate, a transparent electrode layer, a titanium oxide layer mainly containing titanium oxide, a zinc oxide layer mainly containing zinc oxide, and a photoelectric conversion layer. When the thickness of the zinc oxide layer is 1 nm or more and 20 nm or less and the photoelectric conversion layer is composed of one battery layer, the thickness of the titanium oxide layer is 20 nm or more when the thickness of the zinc oxide layer is 1 nm. 77 nm or less, 3 nm to 19 nm to 73 nm or less, 5 nm to 17 nm to 69 nm or less, 10 nm to 15 nm to 58 nm or less, and 20 nm to 15 nm to 35 nm or less. A photoelectric conversion device is provided. When the photoelectric conversion layer is composed of two battery layers, the thickness of the titanium oxide layer is 28 nm or more and 87 nm or less when the thickness of the zinc oxide layer is 1 nm, and the thickness is 26 nm or more and 82 nm or less when 3 nm. A photoelectric conversion layer value within a range of 25 nm to 77 nm when the thickness is 5 nm and 22 nm to 65 nm when the thickness is 10 nm and 22 nm to 39 nm when the thickness is 20 nm is provided. In the case where the photoelectric conversion layer is composed of three battery layers, the thickness of the titanium oxide layer is 32 nm to 89 nm when the thickness of the zinc oxide layer is 1 nm, and 30 nm to 85 nm when 3 nm, and 5 nm. There is provided a photoelectric conversion device having a range of 28 nm to 80 nm, 10 nm to 25 nm to 69 nm, and 20 nm to 25 nm to 44 nm.

  In the above photoelectric conversion device, reduction of the titanium oxide layer by plasma is prevented, and the amount of light incident on the photoelectric conversion layer is optimized according to the quantum efficiency. This is a photoelectric conversion device.

  According to the present invention, in addition to plasma reduction resistance, the film thickness of the titanium oxide layer and the zinc oxide layer is determined in consideration of the quantum efficiency and the average transmittance reflecting the sunlight spectrum. The device can be obtained reliably. In the present invention, suitable film thicknesses of the titanium oxide layer and the zinc oxide layer can be determined according to the layer structure of the photoelectric conversion layer and the material used.

It is the schematic showing the structure of the photoelectric conversion apparatus which concerns on one Embodiment 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 weight function of a single type amorphous silicon solar battery cell. It is a graph showing the distribution of the change rate of the transmittance | permeability in each film thickness of a titanium oxide layer and a zinc oxide layer about a single type amorphous silicon solar cell. It is a weight function of a tandem solar cell. It is a graph showing the distribution of the change rate of the transmittance | permeability in each film thickness of a titanium oxide layer and a zinc oxide layer about a tandem type solar cell. It is a weight function of a triple type photovoltaic cell. It is a graph showing the distribution of the change rate of the transmittance | permeability in each film thickness of a titanium oxide layer and a zinc oxide layer about a triple type solar cell.

  FIG. 1 is a schematic diagram illustrating a configuration of a photoelectric conversion apparatus according to an embodiment of the present invention. The photoelectric conversion device 100 is a tandem silicon solar cell, and includes a substrate 1, a transparent electrode layer 2, a titanium oxide layer 51, a zinc oxide layer 52, and a first cell layer 91 (amorphous as the solar cell photoelectric conversion layer 3). (Silicon-based) and second cell layer 92 (crystalline silicon-based), intermediate contact layer 5, and 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.

  A method for manufacturing a photoelectric conversion device according to this embodiment will be described by taking a process for manufacturing a solar cell panel as an example. 2 to 5 are schematic views showing a method for manufacturing the solar cell panel of the present embodiment.

(1) FIG. 2 (a)
A soda float glass substrate (for example, 1.4 m × 1.1 m × plate thickness: 3.5 mm to 4.5 mm) is used as the substrate 1. 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 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 transparent electrode layer 2, an alkali barrier film (not shown) may be formed between the substrate 1 and the transparent electrode film in addition to the transparent electrode film. As the alkali barrier film, a silicon oxide film (SiO ₂ ) is formed at a temperature of about 500 ° C. in a thermal CVD apparatus at 50 nm to 150 nm. The transparent conductive layer 2 may be a ZnO film or ITO film doped with Ga or Al.

A titanium oxide layer 51 and a zinc oxide layer 52 are provided on the transparent electrode layer 2.
The titanium oxide layer 51 is a film mainly containing titanium oxide, and may contain a dopant in order to improve conductivity. The titanium oxide layer 51 has a refractive index in the range of 2.9 to 2.2 in the wavelength range of 380 nm to 1100 nm. In order to reduce light absorption loss, the extinction coefficient of the titanium oxide layer 51 is preferably 0.1 or less in the wavelength range of 400 nm to 1100 nm.
The titanium oxide layer 51 is formed by a sputtering method, a CVD method, or the like. When the titanium oxide layer 51 is formed by sputtering, for example, target: TiO ₂ (100% powder) sintered body, reduced pressure atmosphere: 0.4 Pa, substrate temperature: 300 ° C., high frequency power: 13.56 MHz, applied power 1 W / cm ² .

The zinc oxide layer 52 functions as a reduction preventing layer for the titanium oxide layer 51. That is, the titanium oxide layer 51 is prevented from being reduced by hydrogen plasma during the formation of a silicon film (photoelectric conversion layer 3) described later. In addition, when the silicon film and the titanium oxide layer are in contact with each other after film formation, there is an effect of preventing the contact surface of the titanium oxide layer from being reduced by hydrogen contained in the silicon film.
The zinc oxide layer 52 is a film mainly containing zinc oxide, and may contain a dopant such as Ga or Al in order to enhance conductivity. The zinc oxide layer 52 has a refractive index of 2.2 to 1.1 in a wavelength range of 350 nm to 1100 nm in consideration of absorption loss of light having a long wavelength due to an increase in carrier concentration and a difference in refractive index from the titanium oxide layer 51. The range is 9. In order to reduce light absorption loss, the extinction coefficient of the zinc oxide layer 52 is preferably 0.1 or less in the wavelength range of 350 nm to 1100 nm.
The zinc oxide layer 52 is formed by a sputtering method or the like. When forming the zinc oxide layer 52 by sputtering, the conditions are: target: Ga-doped ZnO, reduced pressure atmosphere: 0.4 Pa, substrate temperature: 300 ° C., applied power: 1 W / cm ² . Considering the effect of preventing reduction of the titanium oxide layer by hydrogen plasma, the thickness of the zinc oxide layer 52 is preferably 1 nm or more and 20 nm or less.

Here, each film thickness of the titanium oxide layer 51 and the zinc oxide layer 52 is determined as follows.
First, a weight function that is the product of the spectrum of incident light in a predetermined wavelength region and the quantum efficiency of the solar battery cell is calculated. AM1.5 sunlight spectrum is applied to the incident light spectrum. For example, the quantum efficiency of a tandem solar cell that is not provided with a titanium oxide layer and a zinc oxide layer is applied.

  A transmission spectrum of light transmitted through the titanium oxide layer and the zinc oxide layer is obtained when the titanium oxide layer 51 and the zinc oxide layer 52 have arbitrary thicknesses. The transmission spectrum can be obtained from the light incident side by performing optical thin film multiple interference calculation on a flat film model having a four-layer structure of transparent electrode layer / titanium oxide layer / zinc oxide layer / silicon layer. The optical thin film multiple interference calculation is a calculation method that does not include the absorption in the transparent electrode layer and the silicon layer, and purely obtains the transmission spectrum of the light transmitted through the titanium oxide layer / zinc oxide layer. At this time, the transparent electrode layer and the silicon layer are semi-infinite media, and the incident light is handled as being generated in the transparent electrode layer, and the transmission spectrum can be obtained by obtaining the emitted light emitted to the silicon layer. The calculation can be performed by, for example, the optical thin film calculation software OPTAS-FILM manufactured by Cybernet.

  From the acquired transmission spectrum and the weight function, the average transmittance in the titanium oxide layer and the zinc oxide layer from which the transmission spectrum is obtained is calculated. Specifically, for each wavelength in the absorption wavelength region (350 nm to 1100 nm) of the solar cell, the weighted transmittance is calculated by multiplying the value of the transmittance and the value of the weight function, and the weighted transmittance at each wavelength is calculated. Average transmittance is obtained. Average transmittance is obtained for various combinations of titanium oxide layer thickness and zinc oxide layer thickness. The wavelength interval for calculating the weighted transmittance is preferably set appropriately in consideration of the accuracy required for determining the thickness of the titanium oxide layer and the zinc oxide layer. In this embodiment, on the basis of the average transmittance when the titanium oxide layer and the zinc oxide layer are not provided, the change rate of the average transmittance from the reference may be calculated.

  The film thickness ranges of the titanium oxide layer 51 and the zinc oxide layer 52 that can increase the amount of light transmitted to the photoelectric conversion layer are determined from the average transmittance or the change rate of the average transmittance obtained in the above process. Further, in consideration of the film thickness of the zinc oxide layer 52 that provides the above-described reduction prevention effect, the combination of the film thicknesses of the titanium oxide layer 51 and the zinc oxide layer 52 that can achieve both plasma reduction resistance and increased short circuit current is determined Is done.

(3) FIG. 2 (c)
Thereafter, the substrate 1 is placed 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 to be appropriate 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 so that the substrate 1 and the laser light are moved relative to each other to form the groove 10. And laser etching into 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, the amorphous silicon p layer 31 from the side on which sunlight is incident on the transparent electrode layer 2 at a reduced pressure atmosphere: 30 Pa to 1000 Pa and a substrate temperature: about 200 ° C. Then, an amorphous silicon i layer 32 and an 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.

  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 5 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 achieve current matching. As the intermediate contact layer 5, a GZO (Ga-doped ZnO) film having a thickness of 20 nm or more and 100 nm or less is formed by a sputtering apparatus using a target: Ga-doped ZnO sintered body. Further, the intermediate contact layer 5 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 indicated by an arrow in the figure. Pulse oscillation: 10 kHz to 20 kHz, laser power is adjusted so as to be suitable for the processing speed, and laser etching is performed so that grooves 11 are formed on the lateral side of the laser etching line of the transparent electrode layer 2 from about 100 μm to 150 μm. To do. Further, this laser may be irradiated from the substrate 1 side. In this case, the photoelectric conversion layer is formed by utilizing a high vapor pressure generated by the energy absorbed in the amorphous silicon-based first cell layer of the photoelectric conversion layer 3. Since 3 can be etched, a more stable laser etching process 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)
An Ag film / Ti film is formed as the back electrode layer 4 by a sputtering apparatus at a reduced pressure atmosphere and at a film forming temperature of 150 ° C. to 200 ° C. In this embodiment, an Ag film: 150 nm or more and 500 nm or less, and a Ti film having a high anticorrosion effect: 10 nm or more and 20 nm or less are stacked in this order to protect them. Alternatively, the back electrode layer 4 may have a laminated structure of an Ag film having a thickness of 25 nm to 100 nm and an Al film having a thickness of 15 nm to 500 nm. For the purpose of reducing the contact resistance between the crystalline silicon n layer 43 and the back electrode layer 4 and improving the light reflection, a film thickness of 50 nm or more and 100 nm or less is formed between the photoelectric conversion layer 3 and the back electrode layer 4 by a sputtering apparatus. A GZO (Ga-doped ZnO) film may be formed and provided.

(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 as to be suitable for the processing speed from 1 kHz to 10 kHz, and laser etching is performed so that grooves 12 are formed on the lateral side of the laser etching line of the transparent electrode layer 2 from 250 μm to 400 μm. .

(8) FIG. 3 (c) and FIG. 4 (a)
The power generation region is divided, and the film end portion around the substrate end is laser-etched to prevent a short circuit at the serial connection portion. 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. The laser light is absorbed by the 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 / transparent electrode layer 2 is removed. Pulse oscillation: 1 kHz or more and 10 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) where there is a peripheral film removal region 14 where the layer 3 / transparent electrode layer 2 is polished and removed should appear, but for convenience of explanation of processing to the end of the substrate 1, The insulating groove formed to represent the Y-direction cross section at the 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 exhibits an effective effect in suppressing external moisture intrusion into the solar cell module 6 from the end portion 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. Therefore, it is preferable.

  In addition, although the laser beam in the above process is made into a YAG laser, there exists what can use a YVO4 laser, a fiber laser, etc. similarly.

(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 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 / 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 were removed by cleaning the substrate 1.

(10) FIGS. 5 (a) and 5 (b)
An attachment portion of the terminal box 23 is provided with an opening through window in the back sheet 24 to take out the current collector plate. Insulating materials are installed in a plurality of layers in the opening through window portion to suppress intrusion of moisture and the like from the outside.
Processing so that power can be taken out from the terminal box 23 on the back side of the solar battery panel by collecting copper foil from one end of the photovoltaic power generation cells arranged in series and the other end of the solar power generation cell. To do. In order to prevent a short circuit with each part, the copper foil arranges an insulating sheet wider than the 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 waterproof effect is installed on the EVA. 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.
The EVA with the back sheet 24 arranged in a predetermined position is deaerated inside in a reduced pressure atmosphere by a laminator and pressed at about 150 to 160 ° C., and EVA is crosslinked and brought into close contact.

(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 ).
(14) FIG. 5 (d)
Before and after the power generation inspection (FIG. 5C), a predetermined performance inspection is performed including an appearance inspection.

Although the tandem solar cell has been described as the solar cell in the above embodiment, the present invention is not limited to this example. For example, it can be similarly applied to single-type solar cells such as amorphous silicon solar cells, crystalline silicon solar cells including microcrystalline silicon, silicon-germanium solar cells, and triple-type solar cells.
As a triple solar cell, for example, a photoelectric cell in which an amorphous silicon-based first cell layer, a crystalline silicon-based second cell layer, and a crystalline silicon-germanium-based third cell layer are stacked in this order from the substrate side. A thing provided with a conversion layer is mentioned. In this case, the first cell layer and the second cell layer can be formed by a process similar to that of the tandem solar cell described above. As the third cell layer, a crystalline silicon p layer and a crystalline silicon n layer are formed by the same process as described above. The crystalline silicon germanium i layer is formed using a source gas: SiH ₄ gas, GeH ₄ gas, and H ₂ gas in a reduced pressure atmosphere: 3000 Pa or less, a substrate temperature: about 200 ° C., and a plasma generation frequency: 40 MHz to 100 MHz. . The thickness of the p layer of the third cell layer is 10 nm to 50 nm, the thickness of the i layer is 1 μm to 3 μm, and the thickness of the n layer is 10 nm to 50 nm. An intermediate contact layer may be provided between the battery layers.
In order to determine the film thickness of the titanium oxide layer and the zinc oxide layer in each solar cell, it is preferable to use quantum efficiency corresponding to the structure of the photoelectric conversion layer and the material of the photoelectric conversion layer.

Example 1
For single-type amorphous silicon solar cells, the relationship between the film thickness and transmittance of the titanium oxide layer and the zinc oxide layer was examined by optical thin film calculation.
The weighting function shown in FIG. 6 was used for the calculation. The weight function shown in FIG. 6 was acquired from the quantum efficiency and sunlight spectrum of a single type amorphous solar battery cell.
With respect to a laminate structure model of transparent electrode layer / titanium oxide layer / zinc oxide layer / amorphous silicon layer, transmittance spectra were calculated at predetermined titanium oxide layer and zinc oxide layer thicknesses. In the above structural model, the optical constant of each layer was set as follows. A value at 550 nm was used as the representative wavelength.
Transparent electrode layer (GZO film): refractive index 1.9, extinction coefficient 0.001
Titanium oxide layer: refractive index 2.5, extinction coefficient 0.001
Zinc oxide layer: refractive index 1.9, extinction coefficient 0.001
Amorphous silicon layer: refractive index 4.4, extinction coefficient 0.3
In the wavelength range of 350 nm to 1100 nm, the transmittance value for each wavelength from the wavelength 350 nm to 20 nm was multiplied by the weight function at that wavelength to calculate the weighted transmittance for each wavelength, and the average transmittance was calculated. The change rate of the average transmittance was calculated based on the average transmittance when the titanium oxide layer was 0 nm and the zinc oxide layer was 0 nm (that is, the titanium oxide layer and the zinc oxide layer were not provided).
The change rate of the average transmittance was calculated for combinations of film thicknesses of various titanium oxide layers and zinc oxide layers.

FIG. 7 shows a distribution diagram of the change rate of the average transmittance with respect to the film thickness of the titanium oxide layer and the zinc oxide layer for the single solar cell. In the figure, the horizontal axis represents the thickness of the titanium oxide layer, and the vertical axis represents the thickness of the zinc oxide layer. It can be seen from FIG. 7 that the transmittance is improved in the region where the zinc oxide layer is thin. The short circuit current of the solar battery cell is increased by the increase in the transmittance. For example, when the transmittance is improved by 8% from the reference value, the short-circuit current of the solar battery cell is also improved by 8% with respect to the short-circuit current of the reference solar battery cell. In FIG. 7, the boundary lines where the short-circuit current (transmittance) increases by 8% and 10% and the optimum values are shown in Table 1, respectively, in the range of the zinc oxide layer from 1 nm to 20 nm. The short-circuit current increase rates of 8% and 10% are numerical values derived from the quality grade based on the output value of the solar cell panel. Usually, the quality grade of a solar cell panel is classified by discrete output values. If an increase of 8% or 10% in the short-circuit current value can be realized, the grade of the panel is improved and the unit price is increased, which is an industrially significant increase.

  Considering the distribution diagram of FIG. 7 and the film thickness (1 nm to 20 nm) of the zinc oxide layer from which the reduction prevention effect is obtained, the region where the reduction prevention effect of the zinc oxide layer is obtained while improving the transmittance is the short-circuit current 8 In the case of% or more, the region is surrounded by a thick line in FIG. 7, and in the case where the short circuit current is 10% or more, the region is surrounded by a thick broken line. If the combination of the thickness of the titanium oxide layer and the zinc oxide layer is selected within the region surrounded by the thick line or the thick broken line, the reflection loss between the transparent electrode layer and the photoelectric conversion layer is reduced, and the single type The output can be increased by increasing the short-circuit current of the solar battery cell. In particular, with the combination of film thicknesses shown as the optimum values in Table 1, the output of the single solar cell can be maximized.

(Example 2)
Regarding the tandem solar cell, the relationship between the film thickness and transmittance of the titanium oxide layer and the zinc oxide layer was examined by optical thin film calculation.
The weighting function shown in FIG. 8 was used for the calculation. The weighting function shown in FIG. 8 was obtained from the quantum efficiency and solar spectrum of tandem solar cells (first cell layer: amorphous silicon system, second cell layer: crystalline silicon system).
In the same manner as in Example 1, the average transmittance was calculated in the wavelength range of 350 nm to 1100 nm using the transmission spectrum obtained from the laminated structure model. Furthermore, the change rate of the average transmittance was calculated based on the average transmittance when the titanium oxide layer was 0 nm and the zinc oxide layer was 0 nm (that is, the titanium oxide layer and the zinc oxide layer were not provided).

FIG. 9 shows a distribution diagram of the change rate of the average transmittance with respect to the film thickness of the titanium oxide layer and the zinc oxide layer for the tandem solar cell. In the figure, the horizontal axis represents the thickness of the titanium oxide layer, and the vertical axis represents the thickness of the zinc oxide layer. In FIG. 9, the boundary lines where the short-circuit current (transmittance) increases by 8% and 10% and the optimum values in the range of the zinc oxide layer from 1 nm to 20 nm are shown in Table 2, respectively.

  In consideration of the distribution diagram of FIG. 9 and the film thickness (1 nm to 20 nm) of the zinc oxide layer from which the reduction prevention effect is obtained, the region where the reduction prevention effect of the zinc oxide layer is obtained while improving the transmittance is the short-circuit current 8 In the case of% or more, the region is surrounded by a thick line in FIG. 9, and in the case where the short circuit current is 10% or more, the region is surrounded by a thick broken line. If a combination of the thicknesses of the titanium oxide layer and the zinc oxide layer is selected within a region surrounded by a thick line or a thick broken line, reflection loss between the transparent electrode layer and the photoelectric conversion layer can be reduced. As a result, the output can be increased by increasing the short-circuit current of the tandem solar cell. In particular, with the combination of film thicknesses shown as the optimum values in Table 2, the output of the tandem solar cell can be maximized.

(Example 3)
For the triple solar cell, the relationship between the film thickness and transmittance of the titanium oxide layer and the zinc oxide layer was examined by optical thin film calculation.
For the calculation, a weight function shown in FIG. 10 was used. The weighting function shown in FIG. 10 shows the quantum efficiency of the triple solar cell (first cell layer: amorphous silicon type, second cell layer: crystalline silicon type, third cell layer: crystalline silicon germanium type) and Obtained from the solar spectrum.
Using the transmission spectrum obtained from the laminated structure model in the same manner as in Example 1, the average transmittance was calculated in the wavelength range of 350 nm to 1100 nm. The change rate of the average transmittance was calculated based on the average transmittance when the titanium oxide layer was 0 nm and the zinc oxide layer was 0 nm (that is, the titanium oxide layer and the zinc oxide layer were not provided).

FIG. 11 shows a distribution diagram of the change rate of the average transmittance with respect to the film thickness of the titanium oxide layer and the zinc oxide layer for the triple-type crystalline silicon germanium solar battery cell. In the figure, the horizontal axis represents the thickness of the titanium oxide layer, and the vertical axis represents the thickness of the zinc oxide layer. In FIG. 11, the boundary lines where the short-circuit current (transmittance) increases by 8% and 10% and the optimum values in the range of the zinc oxide layer from 1 nm to 20 nm are shown in Table 3, respectively.

  Considering the distribution diagram of FIG. 11 and the film thickness (1 nm to 20 nm) of the zinc oxide layer from which the reduction prevention effect is obtained, the region where the reduction prevention effect of the zinc oxide layer is obtained while improving the transmittance is the short-circuit current 8 In the case of% or more, the region is surrounded by a thick line in FIG. 11, and in the case where the short circuit current is 10% or more, the region is surrounded by a thick broken line. If a combination of the thicknesses of the titanium oxide layer and the zinc oxide layer is selected within the region surrounded by the thick line or the thick broken line, the reflection loss between the transparent electrode layer and the photoelectric conversion layer is reduced. In particular, in the combination of film thicknesses shown as the optimum values in Table 3, the output of the triple-type crystalline silicon germanium solar cell can be maximized.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Transparent electrode layer 3 Photoelectric conversion layer 4 Back electrode layer 5 Intermediate contact layer 6 Solar cell module 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 51 Titanium oxide layer 52 Zinc oxide layer 91 First cell layer 92 Second cell layer 100 Photoelectric conversion device

Claims (1)

On the substrate, a transparent electrode layer, a titanium oxide layer mainly containing titanium oxide, a zinc oxide layer mainly containing zinc oxide, and a photoelectric conversion layer for producing a photoelectric conversion layer,
Calculate a weight function that is the product of the spectrum of incident light and the quantum efficiency of the photoelectric conversion layer,
Light transmitted through the titanium oxide layer and the zinc oxide layer having the predetermined film thickness from the spectrum of light transmitted through the titanium oxide layer and the zinc oxide layer having a predetermined film thickness and the calculated weight function. The average transmittance of
Create a distribution map of the change rate of the calculated average transmittance with respect to the thickness of the titanium oxide layer and the zinc oxide layer,
The range of the rate of change of the average transmittance in consideration of the rate of increase in the short-circuit current read from the distribution chart, and the thickness range of the zinc oxide layer in consideration of the effect of preventing the reduction of the titanium oxide layer from 1 nm to 20 nm. Based on the above, obtain a combination range of the thickness of the titanium oxide layer and the zinc oxide layer that can increase the short-circuit current,
The manufacturing method of the photoelectric conversion apparatus which determines the film thickness of the said titanium oxide layer and zinc oxide layer which form from the said combination range.

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