JP2012059886A - Photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-film silicon-based photoelectric conversion device which is capable of efficiently collecting currents, exhibits low optical absorption loss, and has high light reflectivity on the rear-surface electrode side.SOLUTION: A photoelectric conversion device 100 comprises, in the order from the light incident side: a transparent electrode layer 2; a silicon-based photoelectric conversion layer 3 formed by deposition; a rear-surface transparent electrode layer 4 consisting essentially of a transparent conductive oxide; a comb-shaped rear-surface metal electrode layer 5 consisting essentially of a metal, or a rear-surface metal electrode layer having a thickness of 10 to 100 nm; and a reflective layer 6 consisting essentially of barium sulfate.

Description

  The present invention relates to a photoelectric conversion device, and more particularly to a thin film silicon solar cell using thin film silicon as a power generation layer.

  A solar cell is known as a photoelectric conversion device that receives light and converts it into electric power. Among solar cells, for example, a thin-film silicon solar cell in which a thin-film silicon layer is stacked on a power generation layer (photoelectric conversion layer) is easy to increase in area, and the film thickness is about 1/100 that of a crystalline solar cell. There are advantages such as thin and less material. For this reason, the thin film silicon solar cell can be manufactured at a lower cost than the crystalline solar cell. However, a disadvantage of the thin-film silicon solar cell is that the conversion efficiency is lower than that of the crystal system.

  Solar cells using a silicon-based photoelectric conversion layer have a small absorption coefficient for long-wavelength light with a wavelength of 500 nm or more. Therefore, incident light is reflected in the solar cell to increase the optical path length, and light absorption by silicon. The amount needs to be increased. For this reason, in the super straight type in which sunlight is incident from the transparent substrate side, improvement of the back surface structure on the side opposite to the light incident side with respect to the power generation layer has been studied.

  Patent Document 1 discloses a crystalline solar cell in which fine powder of Al oxide is formed as an irregular reflection film on a photoelectric conversion layer made of crystalline silicon as a back surface structure, and Ag is vacuum-deposited thereon as a back electrode. ing. In Patent Document 2, a transparent conductive oxide film and a translucent sealing resin layer are formed on a photoelectric conversion layer made of amorphous silicon, and a white plate having a light scattering surface is laminated thereon. A thin film amorphous silicon solar cell is disclosed.

Japanese Patent No. 2690963 (right column on page 2, lines 4-5, lines 43-47) JP-A-2-106077 (Claim 1, page 2, lower left column, lines 4 to 20)

  A crystalline silicon solar cell and a thin film silicon solar cell have different structures for extracting current generated in the photoelectric conversion layer. In the crystalline silicon solar cell of Patent Document 1, an insulating irregular reflection film is disposed between the photoelectric conversion layer and the back electrode, and a contact hole is provided in a part of the irregular reflection film to extract current. ing. However, in a thin-film silicon solar cell, generally, an insulating layer is not disposed between the photoelectric conversion layer and the back electrode, and the back electrode also uses a conductive layer. When applying an irregular reflection film to a thin film silicon solar cell, it is necessary to apply an irregular reflection film having conductivity. The irregular reflection film described in Patent Document 1 is a fine powder of aluminum oxide, barium sulfate, and fluorocarbon, and has no electrical conductivity. Therefore, it is difficult to apply the invention described in Patent Document 1 to a thin film silicon solar cell as it is.

In Patent Document 2, a transparent conductive oxide film is used as the back electrode. The transparent conductive oxide film has a larger sheet resistance than a metal electrode such as Ag or Al. For this reason, when a transparent conductive oxide film is used as the back electrode as in the thin film silicon solar cell described in Patent Document 2, it is necessary to reduce the sheet resistance in order to extract current and integrate it with adjacent cells. In order to reduce the sheet resistance, it is common to increase the film thickness of the transparent conductive oxide film. However, if the thickness of the transparent conductive oxide film is increased, the transparency is lowered. Therefore, light absorption when sunlight passes through the transparent conductive oxide film and re-reflects to return to the photoelectric conversion layer. The problem of increased loss arises.
Moreover, in patent document 2, the resin layer for sealing is provided as a layer which connects between the transparent conductive oxide which is a back surface electrode, and a white board, and it heats by pressure bonding. This sealing resin layer is translucent, but is formed from ethylene vinyl acetate (EVA) or the like. Therefore, it is considered that there is a light absorption loss when light passes through the resin layer.
Moreover, in patent document 2, since the improvement of a solar cell characteristic other than a short circuit current is not acquired, it is thought that the room for improvement is left.

  The present invention has been made in view of such circumstances, and improves the short-circuit current by using a back electrode with a high light reflectance that is effective for reuse in the photoelectric conversion layer, and is transparent. An object of the present invention is to provide a thin film silicon-based photoelectric conversion device that can suppress light absorption loss due to a conductive film and can efficiently collect a short-circuit current.

  In order to solve the above problems, the present invention comprises, on a substrate, in order from the light incident side, a transparent electrode layer, a thin-film silicon-based photoelectric conversion layer, a back surface transparent electrode layer mainly composed of a transparent conductive oxide, Provided is a photoelectric conversion device including a back metal electrode layer mainly made of metal and formed in a comb shape or a back metal electrode layer having a thickness of 10 nm to 100 nm and a reflective layer mainly made of barium sulfate.

According to the above invention, by providing the comb-shaped back surface metal electrode layer on the back surface transparent electrode layer, the current generated in the photoelectric conversion layer can be efficiently extracted without increasing the thickness of the back surface transparent electrode layer. Will be able to. Thereby, the absorption loss by the back surface transparent electrode layer of sunlight can be reduced. Since the back metal electrode layer is formed in a comb shape, most of the sunlight that is not absorbed by the photoelectric conversion layer is reflected by the reflective layer. Since the reflective layer is mainly composed of barium sulfate, it has high light reflection performance and light scattering performance. By providing such a reflective layer, more light can be returned to the photoelectric conversion layer.
Further, instead of the comb-shaped back surface metal electrode layer, an Ag, Al layer may be provided on the entire surface as a thin back surface metal electrode layer having a thickness of 10 nm to 100 nm. As a forming method, vapor deposition or sputtering is used. A similar effect can be obtained by setting the film thickness so that the transmittance is 50% or more.

According to one aspect of the invention, it is preferable that the reflective layer includes a resin that can be bonded to the back transparent electrode layer. Moreover, it is preferable that the said resin is polyvinyl alcohol.
By including such a resin, since the bonding force between the reflective layer and the back surface transparent electrode layer is increased, the reflective layer is hardly peeled off. Therefore, it is not necessary to use a resin layer as described in Patent Document 2.

  According to the present invention, by providing the comb-shaped back surface metal electrode layer and the reflective layer, the current generated in the photoelectric conversion layer can be efficiently collected, and the light absorption loss due to the back surface transparent electrode layer is reduced, and the photoelectric conversion layer The light reflectivity on the back side of can be increased. Moreover, since it is not necessary to separately provide an adhesive layer between the reflective layer and the back surface transparent electrode layer, light absorption loss due to the adhesive layer can be reduced. Accordingly, a thin film silicon photoelectric conversion device with high power generation efficiency is obtained. In particular, the present invention has a remarkable effect in a thin film silicon photoelectric conversion device in which large irregularities are formed in the transparent electrode layer.

It is the schematic which shows the structure of the photoelectric conversion apparatus which concerns on 1st Embodiment. It is a top view of the comb-shaped back surface metal electrode layer of the photoelectric conversion apparatus which concerns on 1st Embodiment. It is a figure which shows the relationship between series resistance and a form factor. It is the schematic which shows the structure of the photoelectric conversion apparatus which concerns on 2nd Embodiment. It is the schematic which shows the structure of the photoelectric conversion apparatus which concerns on 3rd Embodiment.

<First Embodiment>
FIG. 1 is a schematic diagram illustrating a configuration of a photoelectric conversion apparatus according to the present embodiment. The photoelectric conversion device 100 is a single-type thin film silicon solar cell, and includes a substrate 1, a transparent electrode layer 2, a photoelectric conversion layer 3 (first power generation cell layer 91), a back transparent electrode layer 4, and a comb-shaped back metal electrode layer 5. And a reflective layer 6. The photoelectric conversion layer 3 can be used by either amorphous silicon type or crystalline silicon type. 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 the photoelectric conversion device according to the first embodiment will be described.
As the substrate 1, a large soda float glass substrate (for example, 1.4 m × 1.1 m × plate thickness: 3.0 mm to 4.5 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.

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.

As the photoelectric conversion layer 3 (first power generation 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, a reduced pressure atmosphere: 30 Pa to 1000 Pa, a substrate temperature: about 200 ° C., an amorphous silicon p layer on the transparent electrode layer 2 from the side on which sunlight is incident, An amorphous silicon i layer and an amorphous silicon n layer are formed in this order. The amorphous silicon p layer is mainly composed of amorphous B-doped silicon and has a thickness of 10 nm to 30 nm. The amorphous silicon i layer has a thickness of 200 nm to 350 nm. The amorphous silicon n layer is mainly P-doped silicon containing microcrystalline silicon in amorphous silicon and has a thickness of 30 nm to 50 nm. Instead of the amorphous silicon n layer, a crystalline silicon film may be formed, or a laminated structure of an amorphous silicon film and a crystalline silicon film may be used. A buffer layer may be provided between the amorphous silicon p layer and the amorphous silicon i layer in order to improve interface characteristics.

The back surface transparent electrode layer 4 is made of a transparent conductive film mainly composed of a transparent conductive oxide such as SnO ₂ , ZnO, or ITO. In this embodiment, as the back transparent electrode layer 4, a transparent conductive film having a film thickness of 100 nm or more and 1000 nm or less is formed of a ZnO film doped with Ga or Al, and a target: a Ga-doped ZnO sintered body or an Al-doped ZnO sintered body. Is formed by a sputtering apparatus.

The comb-shaped back surface metal electrode layer 5 is made of a metal film mainly composed of a metal such as Ag or Al, and is formed in a predetermined comb shape. FIG. 2 shows a plane of the comb-shaped back surface metal electrode layer of the photoelectric conversion device. In FIG. 2, the reflective layer 6 is omitted in order to make the comb-shaped back surface metal electrode layer 5 easier to see. The comb shape and size are not restricted by the shape of FIG. The comb-shaped back surface metal electrode layer 5 is disposed in order to efficiently collect the current generated in the photoelectric conversion layer 3. It is preferable that the total area of the comb-shaped back metal electrode layer 5 is set to be small as long as the current generated in the photoelectric conversion layer 3 can be collected.
In this embodiment, as the comb-shaped back metal electrode layer 5, an Ag film: a film thickness of 150 nm or more and 500 nm or less is formed into a predetermined comb shape in a reduced pressure atmosphere and a substrate temperature: 150 ° C. to 200 ° C. by a sputtering apparatus. .
The comb-shaped backside metal electrode layer 5 may be formed by vapor deposition after masking the backside transparent electrode layer 4 so as to be formed in a predetermined comb shape instead of the sputtering method. Moreover, you may form the comb-shaped back surface metal electrode 5 using the screen printing which does not use a vacuum device.

  The reflective layer 6 is mainly composed of barium sulfate and has a thickness of 0.6 mm or more. The substantial upper limit of the thickness of the reflective layer 6 is 2 mm. Since the reflective layer mainly composed of barium sulfate reflects light while transmitting light, it can be a layer having a reflectance close to 100% by setting the thickness to 0.6 mm or more. When the thickness is 2 mm or more, it takes time to dry after coating. Therefore, the thickness is desirably 2 mm or less. The reflective layer 6 preferably contains a resin that can be bonded to the back transparent electrode layer 4 as a connecting material. In this embodiment, polyvinyl alcohol (PVA) is used as the resin. PVA is preferably contained at 0.1% by mass to 5% by mass with respect to barium sulfate. PVA can be chemically combined with a transparent conductive oxide.

  A method for forming the reflective layer 6 will be described. First, PVA and barium sulfate are dispersed in a suitable solvent (such as ethanol) in a volume of 50 to 1000 times, and applied onto the back transparent electrode layer 4 and the comb-shaped back metal electrode layer 5. At this time, PVA mixed with water may be used. After application, the reflective layer 6 is formed by drying by annealing. As shown in FIG. 1, the reflective layer 6 may be formed so as to cover the side surfaces of the photoelectric conversion layer 3 and the transparent electrode layer 2.

Example 1
Using a glass substrate 1 (5 cm × 5 cm × plate thickness 1 mm or 4 mm), an amorphous silicon solar battery cell having the following layer configuration in which the photoelectric conversion layer 3 is amorphous silicon-based was produced.
Transparent electrode layer 2: tin oxide film, average film thickness 500 nm
Amorphous silicon p layer: Average film thickness 10 nm
Amorphous silicon i layer: Average film thickness 200 nm
Crystalline silicon n layer: Average film thickness 30 nm
Back surface transparent electrode layer 4: GZO film / average film thickness 700 nm
Comb-shaped back metal electrode layer 5: Ag film / average film thickness 300 nm
Reflective layer 6: film thickness of 0.6 mm to 1.0 mm

The back transparent electrode layer 4 was formed using a target: Ga-doped ZnO sintered body (Ga-doped amount: 0.5 mass%) at a reduced pressure atmosphere: 70 Pa and a substrate temperature: 135 ° C.
The comb-shaped backside metal electrode layer 5 was formed in a predetermined comb-shaped shape with an Ag film: a film thickness of 300 nm at a reduced pressure atmosphere and a substrate temperature: 150 ° C. by a sputtering apparatus. Here, as shown in FIG. 2, the predetermined shape is composed of five parts (2.5 mm × 0.1 mm) corresponding to the comb and one center line (5.5 mm × 0.2 mm). Therefore, the film-forming area ratio which the comb-shaped back surface metal electrode layer 5 occupies is 7% of the back surface transparent electrode layer 4.
For the formation of the reflective layer 6, a solution in which a PVA solution in which PVA and water were mixed at a mass ratio of 1: 1 was dispersed in 200 times ethanol together with barium sulfate was used. The above solution was applied to a laminate in which the comb-shaped backside metal electrode layer 5 was laminated, and then annealed at 160 ° C. for 30 minutes in the atmosphere.
The reflective layer 6 is coated with a PVA-containing barium sulfate solution dispersed in ethanol so as to cover the side surface of the laminate from the top of the laminate laminated to the comb-shaped backside metal electrode layer 5 and dried at 160 ° C. for 30 minutes. It was.

(Reference Example 1)
An amorphous silicon solar battery cell was produced in which the back surface metal electrode layer was formed on the entire surface of the back surface transparent electrode layer without providing the reflective layer 6.
Transparent electrode layer 2: tin oxide film, average film thickness 500 nm
Amorphous silicon p layer: Average film thickness 10 nm
Amorphous silicon i layer: Average film thickness 200 nm
Crystalline silicon n layer: Average film thickness 30 nm
Back surface transparent electrode layer: GZO film / average film thickness 70 nm
Back surface metal electrode layer 5: Ag film / average film thickness 300 nm

  For the comb-shaped back surface metal electrode layer 5, a metal film made of an Ag film was formed on the entire surface of the back surface transparent electrode layer 4 by a sputtering apparatus.

Using the amorphous silicon solar battery cells of Example 1 and Reference Example 1, the short-circuit current (Jsc), open-circuit voltage (Voc), form factor (FF), and conversion efficiency in the initial stage after film formation (before photodegradation) (Eff.) Was measured.
Table 1 shows the results of the above measurements. The numerical values shown in Table 1 are based on the case where the transparent electrode layer and the photoelectric conversion layer (amorphous silicon cell) in Reference Example 1 are amorphous silicon solar cells having the same configuration as in Example 1. It is a relative value based on the measured value.

  According to Table 1, Example 1 improved all of the short circuit current, the open circuit voltage, the form factor, and the conversion efficiency as compared with Reference Example 1. It is considered that this is because the reflectance is improved so that the reflective layer 6 is provided so as to be effectively used for the photoelectric conversion layer 3 on the back surface side. Further, the comb-shaped back surface metal electrode layer 5 is a region that directly reflects light passing from the back surface transparent electrode layer 4 to the reflective layer 6, but the effect of collecting current is greatly improved because the shape factor FF is improved. It was confirmed that the current generated in the photoelectric conversion layer 3 was collected efficiently.

  FIG. 3 shows the relationship between the series resistance and the form factor of the amorphous silicon solar cells of Example 1 and Reference Example 1. In the figure, the horizontal axis represents series resistance and the vertical axis represents form factor. According to FIG. 3, compared with the group of Reference Example 1, Example 1 has a low series resistance. Further, as shown in FIG. 3, the form factor tended to improve as the series resistance decreased. From this, it is considered that in Example 1, the combination of the comb-shaped back surface metal electrode layer 5 and the reflective layer 6 resulted in an improvement in the form factor as a result of a decrease in series resistance.

Second Embodiment
FIG. 4 is a schematic diagram illustrating a configuration of the photoelectric conversion apparatus according to the present embodiment. The photoelectric conversion device 200 is a tandem-type thin-film silicon solar cell, except that the photoelectric conversion layer 3 includes a first cell layer 91 (amorphous silicon cell) and a second cell layer 92 (crystalline silicon cell). It is set as the structure similar to 1 embodiment.

  The photoelectric conversion layer 3 includes a first cell layer 91 (amorphous silicon cell) and a second cell layer 92 (crystalline silicon cell). As the first cell layer 91, as in the first embodiment, a p layer, an i layer and an n layer made of an amorphous silicon thin film are formed on the transparent electrode layer 2 by a plasma CVD apparatus.

  A crystalline silicon p layer 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 to 100 MHz. Then, a crystalline silicon i layer and a crystalline silicon n layer are sequentially formed. The crystalline silicon p layer is mainly composed of B-doped microcrystalline silicon and has a thickness of 10 nm to 50 nm. The crystalline silicon i layer is mainly microcrystalline silicon and has a film thickness of 1.2 μm or more and 3.0 μm or less. The crystalline silicon n layer is mainly P-doped microcrystalline silicon and has a film 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 serving as a semi-reflective film may be 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 an intermediate contact layer, 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.

(Example 2)
Using a glass substrate 1 (5 cm × 5 cm × plate thickness 1 mm or 4 mm), a tandem thin-film silicon solar cell having the following layer configuration in which the photoelectric conversion layer 3 is amorphous silicon and crystalline silicon was produced. .
Transparent electrode layer 2: tin oxide film, average film thickness 500 nm
Amorphous silicon p layer: Average film thickness 10 nm
Amorphous silicon i layer: Average film thickness 200 nm
Crystalline silicon n layer: Average film thickness 30 nm
Crystalline silicon p layer: Average film thickness 20 nm
Crystalline silicon i layer: Average film thickness 2 μm
Amorphous silicon n layer: Average film thickness 30 nm
Back surface transparent electrode layer 4: GZO film / average film thickness 700 nm
Comb-shaped back metal electrode layer 5: Ag film / average film thickness 300 nm
Reflective layer 6: Average film thickness of 0.6 mm to 1.0 mm

  The back transparent electrode layer 4, the comb-shaped back metal electrode layer 5, and the reflective layer 6 were formed in the same manner as in Example 1.

(Reference Example 2)
The transparent electrode layer and the photoelectric conversion layer (amorphous silicon cell, crystalline silicon cell) have the same configuration as in Example 2, on which the GZO average film thickness is 70 nm as the back transparent electrode layer, and the Ag film as the back metal electrode A tandem-type thin film silicon solar cell was manufactured by laminating a thickness of 300 nm.

Using the tandem thin-film silicon solar cells of Example 2 and Reference Example 2, the short-circuit current (Jsc), open-circuit voltage (Voc), form factor (FF), and conversion efficiency in the initial stage after film formation (before photodegradation) (Eff.) Was measured.
Table 2 shows the results of the above measurement. The numerical values shown in Table 2 are relative values based on the measured values of Reference Example 2.

  According to Table 2, in Example 2, all of the short-circuit current, the open-circuit voltage, the form factor, and the conversion efficiency were equal to or higher than those of Reference Example 2. This is considered to be because the reflectance on the back surface side was improved by providing the reflective layer 6. Moreover, it was confirmed that the comb-shaped back surface metal electrode layer 5 was able to efficiently collect the current generated in the photoelectric conversion layer 3.

<Third Embodiment>
FIG. 5 is a schematic diagram illustrating a configuration of the photoelectric conversion apparatus according to the present embodiment. The photoelectric conversion device 300 is a triple thin film silicon solar cell, and the photoelectric conversion layer 3 includes a first cell layer 91 (amorphous silicon), a second cell layer 92 (crystalline silicon), and a third cell. The configuration is the same as that of the first embodiment except that a layer (including crystalline silicon germanium is included in the i layer) is provided.

  The photoelectric conversion layer 3 includes a first cell layer 91 (amorphous silicon-based), a second cell layer 92 (crystalline silicon-based), and a third cell layer (i-layer includes crystalline silicon germanium). As the first cell layer 91, as in the first embodiment, a p layer, an i layer and an n layer made of an amorphous silicon thin film are formed on the transparent electrode layer 2 by a plasma CVD apparatus. As the second cell layer 92, as in the second embodiment, a p layer, an i layer, and an n layer made of a crystalline silicon thin film are formed on the first cell layer 91 by a plasma CVD apparatus.

  A crystalline silicon p layer as the third cell layer 93 is formed on the second cell layer 92 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 to 100 MHz. Then, a crystalline silicon germanium i layer and a crystalline silicon n layer are sequentially formed.

The crystalline silicon p layer is mainly composed of B-doped microcrystalline silicon and has a thickness of 10 nm to 50 nm.
The crystalline silicon germanium i layer is mainly microcrystalline silicon germanium and has a film thickness of 1.0 μm to 3.0 μm. The germanium concentration is 5 atomic% to 15 atomic%.
The crystalline silicon n layer is mainly P-doped microcrystalline silicon and has a film thickness of 20 nm to 50 nm. The crystalline silicon n layer may be replaced with an amorphous silicon n layer.

  An intermediate contact layer serving as a semi-reflective film may be provided between the second cell layer 92 and the third cell layer 93 in order to improve the contact property and achieve current matching. As an intermediate contact layer, 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.

Example 3
A triple-type thin-film silicon solar cell in which the third cell layer 93 having the following configuration was inserted between the second cell layer 93 and the back transparent electrode layer 4 of Example 2 was produced (Example 3). Further, Example 3 and the transparent electrode layer, photoelectric conversion layer (amorphous silicon cell, crystalline silicon cell) except that the reflective layer 6 was not provided and the back metal electrode layer 5 was formed on the entire surface of the back transparent electrode layer. The crystalline silicon germanium cell) has a similar configuration, and a triple thin film silicon solar cell in which a GZO average film thickness of 70 nm is laminated as a back transparent electrode layer and an Ag film thickness of 300 nm is laminated as a back metal electrode is referred to as Reference Example 3. did.
Using the triple-type thin film silicon solar cells of Example 3 and Reference Example 3, the short-circuit current (Jsc), open-circuit voltage (Voc), form factor (FF), and conversion efficiency in the initial stage after film formation (before photodegradation) (Eff.) Was measured.

Table 3 shows the results. The numerical values described in Table 3 are relative values based on the measured values of Reference Example 3.

  According to Table 3, in Example 3, all of the short-circuit current, the open-circuit voltage, the shape factor, and the conversion efficiency were equal to or higher than those of Reference Example 3. This is considered to be because the reflectance on the back surface side was improved by providing the reflective layer 6. Moreover, it was confirmed that the comb-shaped back surface metal electrode layer 5 was able to efficiently collect the current generated in the photoelectric conversion layer 3.

  In the first to third embodiments, the comb-shaped back surface metal electrode layer is used. Alternatively, a thin back surface metal electrode layer may be provided on the entire surface of the back surface transparent electrode layer. The back metal electrode layer is made of Ag or Al and has a thickness of 10 nm to 100 nm. As a method for forming the back surface metal electrode layer, vapor deposition or sputtering is used. By setting the film thickness so that the transmittance is 50% or more, the same effect as that obtained when the comb-shaped back surface metal electrode layer is provided can be obtained.

  The present invention can be similarly applied to a solar cell manufactured on a non-light-transmitting substrate such as a metal substrate or the like, on which light is incident from the side opposite to the substrate.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent electrode layer 3 Photoelectric conversion layer 4 Back surface transparent electrode layer 5 Comb-shaped back surface metal electrode layer 6 Reflective layer 91 1st cell layer (amorphous silicon cell)
92 Second cell layer (crystalline silicon cell)
93 Third cell layer (crystalline silicon germanium cell)
100, 200, 300 Photoelectric conversion device

Claims (3)

In order from the light incident side,
A transparent electrode layer;
A thin-film silicon-based photoelectric conversion layer;
A back surface transparent electrode layer mainly composed of a transparent conductive oxide;
A back metal electrode layer mainly composed of metal and formed in a comb shape or a back metal electrode layer having a thickness of 10 nm to 100 nm,
A reflective layer mainly composed of barium sulfate;
A photoelectric conversion device comprising:   The photoelectric conversion device according to claim 1, wherein the reflective layer includes a resin that can be bonded to the back metal electrode layer. The photoelectric conversion device according to claim 2, wherein the resin is polyvinyl alcohol.

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