WO2015076208A1

WO2015076208A1 - Glass sheet

Info

Publication number: WO2015076208A1
Application number: PCT/JP2014/080242
Authority: WO
Inventors: 伸一安間; 裕黒岩; 朋美安部; 川本　泰
Original assignee: 旭硝子株式会社
Priority date: 2013-11-19
Filing date: 2014-11-14
Publication date: 2015-05-28
Also published as: TW201524931A; JPWO2015076208A1

Abstract

　Through the present invention, excellent heat resistance and devitrification characteristics are obtained, and Na diffusion capacity is increased and power generating efficiency is increased when the present invention is used as a glass substrate for a compound semiconductor solar cell. A glass sheet including, by mass percentage based on the oxides below, 45-65% SiO₂, 9-17% Al₂O₃, 0-1% B₂O₃, 0-2% MgO, 1-12% CaO, 1-15% SrO, 1.4-12% BaO, 2-6% ZrO₂, 5-10% Na₂O, and 2-10% K₂O, MgO + CaO + SrO + BaO being 15-30%, and 2(SrO-BaO) + (K₂O-Na₂O) being 11.5% or less.

Description

Glass plate

The present invention relates to a glass plate, and more particularly to a glass plate suitably used for a compound solar cell substrate.

In a solar cell, a semiconductor film is formed on a glass substrate as a photoelectric conversion layer. As semiconductors used in solar cells, 11-13 and 11-16 compound semiconductors having a chalcopyrite crystal structure, and cubic or hexagonal 12-16 group compound semiconductors have wavelengths from visible to near infrared. It has a large absorption coefficient for a range of light. Therefore, it is expected as a material for high-efficiency thin film solar cells. Typical examples include Cu (In, Ga) Se ₂ (hereinafter sometimes referred to as CIGS) and CdTe.

In CIGS solar cells and CdTe solar cells, soda lime glass is used as a substrate and solar cells are obtained because they are inexpensive and have an average thermal expansion coefficient close to that of CIGS compound semiconductors and CdTe semiconductors.
In recent years, glass materials that can withstand high heat treatment temperatures have been proposed as glass substrates for CIGS solar cells (see Patent Documents 1 to 3).

Also, it is known that the photoelectric conversion efficiency of a CIGS solar cell can be increased by using a glass substrate containing an alkali metal, particularly Na, as such a glass substrate for CIGS solar cell. When a CIGS photoelectric conversion layer (hereinafter also referred to as “CIGS layer”) is formed on a glass substrate, the glass substrate is heat-treated in the CIGS layer forming step, so that Na atoms contained in the glass substrate are converted into the glass substrate. It diffuses from the surface to the CIGS layer. As a result, the carrier concentration of the CIGS layer is increased and the photoelectric conversion rate can be increased.

Patent Documents 4 and 5 propose that in a glass plate for a solar cell, Na ₂ O is an effective component for the growth of chalcopyrite crystals in the composition of the glass substrate and increases the photoelectric conversion efficiency.

Japanese Patent Laid-Open No. 11-135819 JP 2010-118505 A JP 2008-280189 A JP 2010-267965 A International Publication No. 2012/153634

In a solar cell, a photoelectric conversion layer is formed between glass substrates. In order to produce a solar cell with high power generation efficiency, it is preferable to heat-treat the photoelectric conversion layer at a higher temperature. Heat resistance that can be tolerated is required.
However, Patent Documents 1 to 3 propose glass compositions having a relatively high annealing point, but the inventions described in Patent Documents 1 to 3 do not necessarily have high power generation efficiency. For example, it is desired to increase the power generation efficiency by diffusion of Na from the glass substrate to the photoelectric conversion layer together with the heat resistance of the glass substrate.

In Patent Document 1, an object is to prevent the deformation and distortion of the glass substrate by controlling the annealing point and the thermal expansion coefficient, but power generation efficiency has not been studied in terms of the amount of Na diffusion.
In Patent Document 2, Na ₂ O is blended for diffusion of Na, but the blending amount of Na ₂ O is limited to prevent a decrease in strain point (see paragraph 0027). Further, there is a problem that in Patent Document 2, the strain point from the viewpoint amount of Al ₂ O ₃ is less lowered.
In Patent Document 3, the blending amount of Na ₂ O is limited in consideration of the strain point, the thermal expansion coefficient, and the warp of the glass substrate, but the power generation efficiency is not examined from the point of Na diffusion amount.

Patent Document 4 proposes that Na ₂ O is added while BaO is less than 1% by mass, so that the mobility of sodium ions is advantageously acted on to increase the efficiency of the solar cell. However, while increasing the mobility of the sodium ions by Na 2 _O, heat resistance and devitrification resistance of the glass substrate is increased only Na 2 _O may be reduced.

In Patent Document 5, Na 2 _O and K _{2 O} is mentioned as a component to increase the photoelectric conversion efficiency. However, since the blending amount of Na ₂ O and K ₂ O is limited in consideration of the strain point, the thermal expansion coefficient, and the devitrification characteristics, there is a problem that the photoelectric conversion efficiency cannot be sufficiently increased.

An object of the present invention is to provide a glass plate that obtains excellent heat resistance and devitrification characteristics, and increases power generation efficiency by increasing the amount of Na diffusion when used as a compound solar cell substrate.

As one aspect of the present invention, SiO ₂ is 45 to 65%, Al ₂ O ₃ is 9 to 17%, B ₂ O ₃ is 0 to 1%, MgO is 0 to 2%, CaO 1-12%, SrO 1-15%, BaO 1.4-12%, ZrO ₂ 2-6%, Na ₂ O 5-10%, K ₂ O 2-10 %, MgO + CaO + SrO + BaO is 15 to 30%, and 2 (SrO—BaO) + (K ₂ O—Na ₂ O) is 11.5% or less.

In the present specification, “to” indicating a numerical range is used in the sense of including the numerical values described before and after it as a lower limit and an upper limit, and unless otherwise specified, Are used with similar meanings.

According to the glass plate of the present invention, excellent heat resistance and devitrification characteristics can be obtained, and the amount of Na diffusion can be increased to increase power generation efficiency. Moreover, the solar cell using this can be provided.

FIG. 1 is a cross-sectional view schematically showing an example of the CIGS solar cell of the present embodiment. FIG. 2 is a cross-sectional view schematically showing an example of the CdTe solar cell of the present embodiment.

<Glass plate>
Hereinafter, the glass plate of one Embodiment of this invention is demonstrated.

Glass plate according to the present embodiment, by mass percentage based on the following oxides, the SiO ₂ 45 - 65%, the _{_{_{Al 2 O 3 9 ~ 17%}}} , the _{B 2 O 3 0 ~ 1%} , MgO 0 to 2%, CaO 1-12%, SrO 1-15%, BaO 1.4-12%, ZrO ₂ 2-6%, Na ₂ O 5-10%, K ₂ O 2-10 %, MgO + CaO + SrO + BaO is 15 to 30%, and 2 (SrO—BaO) + (K ₂ O—Na ₂ O) is 11.5% or less.
In the present specification, unless otherwise specified, the content ratio of the glass composition component is expressed in terms of mass percentage (mass%), and these are also simply referred to as%.

According to the glass plate according to the present embodiment, the glass transition temperature and the devitrification characteristics can be set to the preferred ranges shown below by being in the above composition range. Moreover, by being the said composition range, in CIGS solar cell use, the diffusion amount of Na to the photoelectric converting layer formed on a glass substrate from a glass substrate can be increased, and the efficiency of a solar cell can be improved. it can. Furthermore, it can be set as the preferable range which shows a viscosity characteristic, an average thermal expansion coefficient, and a density by being the said composition range below.

The glass transition temperature (Tg) of the glass plate of this embodiment is preferably higher than the glass transition temperature of ordinary soda lime glass that is widely used in general, and is specifically preferably 640 ° C. or higher. . When using a glass plate as a glass substrate of a CIGS solar cell, the glass transition temperature (Tg) is more preferably 645 ° C. or higher, and more preferably 650 ° C. or higher in order to ensure the formation of the CIGS layer at a high temperature. 655 ° C. or higher is particularly preferable. In order not to raise the viscosity at the time of dissolution excessively, it is more preferable that the temperature be 750 ° C. or lower. More preferably, it is 720 degrees C or less, Most preferably, it is 690 degrees C or less.

In the glass plate of the present embodiment, the relationship between the temperature (T4) at which the viscosity is 10 ⁴ dPa · s and the devitrification temperature (TL) is preferably T4−TL> 0. When T4-TL is 0 ° C. or lower, devitrification is likely to occur during the formation of the sheet glass, and it may be difficult to form the glass sheet. T4-TL is more preferably 5 ° C. or higher, and further preferably 10 ° C. or higher. Here, the devitrification temperature is the maximum temperature at which crystals are not generated on the glass surface and inside when the glass is held at a specific temperature for 17 hours.

Considering the moldability of the glass plate, that is, improvement in flatness and productivity, T4 is preferably 1230 ° C. or lower. T4 is more preferably 1220 ° C. or less, and further preferably 1210 ° C. or less.

In addition, the glass plate of the present embodiment has a temperature (T2) at which the viscosity becomes 10 ² dPa · s is 1650 ° C. or less in consideration of the solubility of the glass, that is, the improvement of homogeneity and the improvement of productivity. Is preferred. T2 is more preferably 1630 ° C. or lower, and further preferably 1620 ° C. or lower.

The average thermal expansion coefficient of the glass plate of this embodiment at 50 to 350 ° C. is preferably 70 × 10 ⁻⁷ to 90 × 10 ⁻⁷ / ° C. When the glass plate of the present embodiment is used as a glass substrate of a CIGS solar cell, if it is less than 70 × 10 ⁻⁷ / ° C. or more than 90 × 10 ⁻⁷ / ° C., the difference in thermal expansion from the CIGS layer becomes too large, and the CIGS layer The CIGS layer may be peeled off during or after the film formation. More preferably, it is 85 × 10 ⁻⁷ / ° C. or less.

The glass plate of the present embodiment preferably has a density of 2.85 g / cm ³ or less. When the density exceeds 2.85 g / cm ³ , the mass of the glass substrate becomes heavy, which is not preferable. The density is more preferably 2.83 g / cm ³ or less. Moreover, when manufacturing a glass plate by normal methods, such as a float process and a fusion method, when it considers setting it as the glass composition range which can be manufactured easily, it is 2.4 g / cm < ³ > or more normally.

As described above, the glass plate according to the present embodiment has the above composition, so that the glass transition temperature is high and excellent heat resistance is obtained, and the T4-TL is large and excellent devitrification characteristics are obtained. Since the amount of diffusion is large, the power generation efficiency can be increased. Furthermore, since the viscosity characteristics, average thermal expansion coefficient, and density of T4 and T2 are in an appropriate range, solubility and moldability can be improved during production of the glass substrate. Accordingly, the glass plate according to the present embodiment has various characteristics in a well-balanced manner, and can be preferably used as a glass substrate for CIGS solar cells or CdTe solar cells.

In the glass plate of the present embodiment, the reason for limiting to the above composition is as follows.

SiO ₂ :
SiO ₂ is a component that forms a glass skeleton. If it is less than 45% by mass, the heat resistance and chemical durability of the glass plate are lowered, and the average thermal expansion coefficient may be increased. Preferably it is 47% or more, more preferably 49% or more, and particularly preferably 51% or more.
However, if it exceeds 65%, the high-temperature viscosity of the glass increases, which may cause a problem that the solubility deteriorates. Preferably it is 63% or less, More preferably, it is 62% or less, More preferably, it is 61% or less, Especially preferably, it is 59% or less, More preferably, it is 57.5% or less.

Al ₂ O ₃ :
Al ₂ O ₃ increases the glass transition temperature, improves weather resistance (solarization), heat resistance and chemical durability, and increases Young's modulus. There exists a possibility that glass transition temperature may fall that the content is less than 9%. Moreover, there exists a possibility that an average thermal expansion coefficient may increase. More preferably, it is 9.5% or more, more preferably 10% or more, particularly preferably 11% or more, and further preferably 12% or more.

However, if it exceeds 17%, the high-temperature viscosity of the glass is increased, and the solubility may be deteriorated. Further, the devitrification temperature is increased, and the moldability may be deteriorated. Preferably it is 16% or less, More preferably, it is 15% or less.

B ₂ O ₃ :
B ₂ O ₃ may be contained up to 1% in order to improve the solubility. If the content exceeds 1%, the glass transition temperature may decrease, or the average thermal expansion coefficient may decrease, which is not preferable for the process of forming a photoelectric conversion layer. Moreover, devitrification temperature rises and it becomes easy to devitrify, and plate glass shaping | molding becomes difficult. The content is preferably 0.5% or less. More preferably, it does not contain substantially.
In addition, “substantially does not contain” means that it is not contained other than inevitable impurities mixed from raw materials or the like, that is, it is not intentionally contained.

MgO:
MgO has the effect of lowering the viscosity at the time of melting the glass and promoting the melting, so it may be contained up to 2%.
If it is 2% or less, a desired average thermal expansion coefficient can be obtained. Further, it is preferable that the devitrification temperature does not increase. Preferably it is 1.5% or less, More preferably, it is 1.0%, More preferably, it is 0.5% or less, Most preferably, it is 0.1% or less.

CaO:
CaO is contained in an amount of 1 to 12% because it has the effect of lowering the viscosity of the glass during melting and promoting the melting. Preferably it is 2% or more, More preferably, it is 3% or more, More preferably, it is 4% or more, Most preferably, it is 5% or more. However, if it exceeds 12%, the average thermal expansion coefficient of the glass plate may increase. Moreover, when using as a glass substrate for solar cells, sodium (Na) is difficult to move in the glass substrate, and power generation efficiency may be reduced. Preferably it is 11% or less, More preferably, it is 10% or less, More preferably, it is 9% or less, Most preferably, it is 8.5% or less.

SrO:
SrO is contained in an amount of 1 to 15% because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. Moreover, when it uses in the glass substrate, when using the glass plate of this embodiment as a glass substrate of a CIGS solar cell, there exists an effect which accelerates | stimulates disperse | distributing sodium (Na) to the CIGS layer on a glass substrate. Preferably it is 1.5% or more, More preferably, it is 2% or more, More preferably, it is 3% or more. However, if the content exceeds 15%, the density of the glass plate may increase. It is preferably 13% or less, more preferably 12% or less, still more preferably 11.5% or less, and particularly preferably 10.5% or less.

BaO:
BaO has an effect of lowering the viscosity at the time of melting the glass and promoting the melting, so it is contained in an amount of 1.4 to 12%. Moreover, when using the glass plate of this embodiment as a glass substrate of a CIGS solar cell by containing BaO in a glass plate, there exists an effect which accelerates | stimulates disperse | distributing sodium (Na) to the CIGS layer on a glass substrate. . Preferably it is 2% or more, More preferably, it is 3% or more, More preferably, it is 3.5% or more, Most preferably, it is 4% or more. However, if the content exceeds 12%, the average thermal expansion coefficient of the glass plate increases, and the density may increase. In addition, the Young's modulus may be reduced. It is preferably 11% or less, and more preferably 10% or less.

ZrO ₂ :
ZrO ₂ has an effect of reducing the viscosity at the time of melting the glass and promoting the melting, so it is contained at 2% or more. If it is 6% or less, the power generation efficiency is good, the devitrification temperature is not increased and devitrification does not occur, and plate glass molding is easy. 5.5% or less is preferable, 5% or less is more preferable, and 4.6% or less is more preferable. Further, it is preferably 2.3% or more, more preferably 2.5% or more, further preferably 3% or more, and particularly preferably 3.5% or more.

Na ₂ O:
Na ₂ O is a component for contributing to the improvement of power generation efficiency of the CIGS solar cell when using the glass plate of the present embodiment as a glass substrate of the CIGS solar cell, and is an essential component. Further, it has the effect of lowering the viscosity at the glass melting temperature and facilitating melting, so it is contained in an amount of 5 to 10%. Sodium (Na) diffuses into the CIGS layer formed on the glass substrate to increase the power generation efficiency. However, if the content is less than 5%, Na diffusion to the CIGS layer on the glass substrate becomes insufficient, resulting in power generation efficiency. May be insufficient. The content is preferably 5.3% or more, more preferably 5.5% or more, and particularly preferably 5.6% or more.
When the Na ₂ O content exceeds 10%, the average thermal expansion coefficient tends to increase, and the glass transition temperature tends to decrease. Or chemical durability tends to deteriorate. Alternatively, the Young's modulus may be reduced. The content is preferably 9% or less, more preferably 8% or less, and even more preferably 7.5% or less.

K ₂ O:
K ₂ O is contained in an amount of 2 to 10% because it has an effect of promoting the diffusion of sodium (Na) into the CIGS layer on the glass substrate. However, if it exceeds 10%, the glass transition temperature is lowered, the average thermal expansion coefficient is increased, and the specific gravity may be increased. The content is preferably 2.5% or more, and more preferably 3% or more. Further, it is preferably 9% or less, more preferably 8% or less, further preferably 7% or less, and particularly preferably 6% or less.

TiO ₂ :
When TiO ₂ is contained, the devitrification temperature rises, so it is preferable not to contain it. However, the glass plate of this embodiment is easy to produce a foam layer on the surface of the molten glass when the glass substrate is manufactured, as compared with normal soda lime glass. When the foam layer is generated, the temperature of the molten glass does not rise, it becomes difficult to clarify, and the productivity tends to deteriorate. In order to thin or eliminate the foam layer generated on the surface of the molten glass, a titanium compound may be supplied as an antifoaming agent to the foam layer generated on the surface of the molten glass. The titanium compound is taken into the molten glass and exists as TiO ₂ . This titanium compound may be an inorganic titanium compound (titanium tetrachloride, titanium oxide, etc.) or an organic titanium compound. Examples of the organic titanium compound include titanic acid esters or derivatives thereof, titanium chelates or derivatives thereof, titanium acylates or derivatives thereof, and oxalic acid titanates. For the above reasons, TiO ₂ is allowed to be contained in the glass substrate at 0.2% or less as an impurity.

MgO + CaO + SrO + BaO (total content of MgO, CaO, SrO and BaO):
MgO, CaO, SrO and BaO are contained in an amount of 15% or more in terms of the total content of MgO, CaO, SrO and BaO from the viewpoint of reducing the viscosity at the time of melting the glass and promoting the melting. However, if the total amount of these alkaline earth oxides exceeds 30%, the devitrification temperature rises and the moldability may be deteriorated. 16% or more is preferable, and 17% or more is more preferable. Moreover, 26% or less is preferable, 25% or less is more preferable, 23% or less is further more preferable, and 21% or less is especially preferable.

SrO + BaO (total content of SrO and BaO):
Both SrO and BaO have the effect of increasing the diffusion of sodium that diffuses into the CIGS layer formed on the glass substrate and increases the power generation efficiency while maintaining the heat resistance of the glass plate. Therefore, it is preferable to contain in the range which SrO + BaO becomes 6% or more. More preferably, it is 6.5% or more, further preferably 7% or more, and particularly preferably 7.5% or more. However, if SrO + BaO is too large, the specific gravity of the glass is increased and the strength as a glass substrate is lowered. Therefore, it is preferable to contain SrO + BaO in a range of 18% or less. More preferably, it is 17% or less, More preferably, it is 16.5% or less, Most preferably, it is 16% or less.

SrO—BaO (a value obtained by subtracting the BaO content from the SrO content):
BaO has a larger effect of increasing the diffusion of sodium while maintaining heat resistance than SrO, so it is preferable to contain BaO in a range where SrO—BaO is 7.5% or less. More preferably, it is 7% or less, more preferably 6.5% or less, and particularly preferably 6% or less.

Na ₂ O + K ₂ O (total content of Na ₂ O and K ₂ O):
Increasing the proportion of Na ₂ O + K ₂ O in the composition has the effect of increasing the diffusion of sodium to increase the power generation efficiency by diffusing into the CIGS layer configured on the glass substrate for CIGS solar cells. It is preferable that Na ₂ O + K ₂ O is contained within a range of 7% or more. More preferably, it is 7.5% or more, More preferably, it is 8% or more, Most preferably, it is 9% or more. However, if Na ₂ O + K ₂ O becomes too large, the glass transition point of the glass is lowered and the heat resistance of the glass substrate is lowered, so that Na ₂ O + K ₂ O is preferably contained in an amount of 15% or less. More preferably, it is 14% or less, more preferably 13.5% or less, and particularly preferably 13% or less.

K ₂ O—Na ₂ O (value obtained by subtracting the content of Na ₂ O from the content of K ₂ O):
Since Na ₂ O has a larger ratio of the effect of increasing the diffusion of sodium to the effect of decreasing the heat resistance than K ₂ O, from the viewpoint of increasing the diffusion of sodium while maintaining the heat resistance, K ₂ O —Na ₂ O is preferably contained within a range of 2% or less. More preferably, it is 1% or less, more preferably 0% or less, particularly preferably -1.3%.

2 (SrO—BaO) + (K ₂ O—Na ₂ O):
Reducing (SrO—BaO) and (K ₂ O—Na ₂ O) has the effect of increasing the amount of sodium diffusion while maintaining heat resistance. Decreasing (SrO—BaO) has a greater effect of increasing the amount of sodium diffusion than reducing (K ₂ O—Na ₂ O). Therefore, when productivity improvement is taken into account, 2 (SrO— BaO) + (K ₂ O—Na ₂ O) is preferably contained within a range of 11.5% or less. More preferably, it is 11% or less, More preferably, it is 10.5% or less, Most preferably, it is 10% or less.

Glass plate of the present embodiment consists essentially of the above matrix composition _{_{_{_{(SiO 2, Al 2 O 3}}}} , B 2 O 3, MgO, CaO, SrO, BaO, ZrO 2, Na 2 O, and _K 2 O) However, as long as the object of the present invention is not impaired, each of the following other components may be contained in an amount of 1% or less, and a total of 5% or less of these added components and the above-described TiO ₂ may be contained. For example, ZnO, Li ₂ O, WO ₃ , Nb ₂ O ₅ , V ₂ O ₅ , Bi ₂ O ₃ , MoO ₃ for the purpose of improving weather resistance, solubility, devitrification, ultraviolet shielding, refractive index, and the like. , P ₂ O ₅ or the like may be contained.

In addition, in order to improve the solubility and clarity of the glass, these raw materials are matrix composition raw materials so that each glass contains 1% or less of SO ₃ , F, Cl, SnO ₂ and 2% or less in total. You may add to.
Further, in order to improve the chemical durability of the glass plate, 2% or less of Y ₂ O ₃ and / or La ₂ O ₃ may be contained in the glass.

Incidentally, the glass plate of the present embodiment, in order to increase the power generation efficiency to ensure the transmittance, the matrix composition _{_{_{_{(SiO 2, Al 2 O 3}}}} , B 2 O 3, MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O, and K ₂ O) are preferably contained in an amount of 0.06 parts by mass or less in terms of Fe ₂ O _{3 with} respect to 100 parts by mass. More preferably, it is 0.055 mass part or less, More preferably, it is 0.05 mass part or less, Most preferably, it is 0.045 mass part or less. However, for solar cells, when the transmittance of the glass substrate is unquestioned (for example, when used as a substrate for a CIGS solar cell), the cost increase of the raw material due to the use of a raw material with less iron content than usual, and From the viewpoint of ease of heating during dissolution, the iron oxide is preferably 0.2 parts by mass or less, more preferably 0.15 parts by mass or less in terms of Fe ₂ O _{3 with} respect to 100 parts by mass of the mother composition. 0.12 parts by mass or less is more preferable.
Further, when the content of the iron oxide is 0.01 parts by mass or more, an industrial raw material in which the mixing of the iron oxide component is unavoidable can be used. Further, when the content of the iron oxide is 0.01 parts by mass or more, the absorption of radiation is remarkably increased at the time of melting, so that the temperature of the molten glass is easily increased and the production is not hindered. More preferably, it is 0.015 mass part or more, More preferably, it is 0.02 mass part or more.
In this embodiment, examples of the iron oxide input raw material include a valve stem and iron oxide powder.

Further, the glass plate of the present embodiment, considering the environmental _burden, it is preferred not to contain _{_{_{As 2 O 3, Sb 2 O}}} 3 substantially. In consideration of stable float forming, it is preferable that ZnO is not substantially contained. However, the glass plate of the present embodiment is not limited to being formed by the float method, and may be manufactured by forming by the fusion method.

<Method for producing glass plate>
The manufacturing method of the glass plate of this embodiment is demonstrated.
When manufacturing the glass plate of this embodiment, a melt | dissolution and clarification process and a shaping | molding process are implemented similarly to the time of manufacturing the conventional glass plate. In addition, since the glass plate of this embodiment is an alkali containing glass substrate containing an alkali metal oxide (Na ₂ O and K ₂ O), SO ₃ can be effectively used as a fining agent, and molding As the method, a float method and a fusion method (down draw method) are suitable.

In the manufacturing process of a glass plate for a glass substrate for a solar cell, as a method for forming glass into a plate shape, a float method capable of easily and stably forming a large-area glass substrate with an increase in the size of the solar cell. Is preferably used.

Hereinafter, the preferable aspect of the manufacturing method of the glass plate of this embodiment is demonstrated.
First, molten glass obtained by melting raw materials is formed into a plate shape. For example, raw materials are prepared so that the obtained glass substrate has the above composition, the raw materials are continuously charged into a melting furnace, and heated to 1550 to 1700 ° C. to obtain molten glass. Then, this molten glass is formed into a ribbon-like glass plate by applying, for example, a float process.
Next, after drawing the ribbon-shaped glass plate from the float forming furnace, it is cooled to room temperature by a cooling means, and after cutting, the glass plate can be obtained.

<Use of glass plate>
The glass plate by this embodiment can be preferably used as a glass substrate for solar cells, a cover glass for solar cells, and a back plate glass for solar cells.

As the photoelectric conversion layer of the solar cell, a 11-13 group or 11-16 group compound semiconductor having a chalcopyrite crystal structure, or a cubic or hexagonal group 12-16 compound semiconductor can be preferably used. Representative examples include CIGS compounds, CdTe compounds, CIS compounds, CZTS compounds, and the like. In addition, as the photoelectric conversion layer of the solar cell, a silicon compound, an organic compound, or the like may be used.

Since the glass plate by this embodiment has the said characteristic, it can be preferably used for a CIGS solar cell.
When applying the glass plate of this embodiment to the glass substrate of a CIGS solar cell, it is preferable that the thickness of a glass substrate shall be 3 mm or less, More preferably, it is 2 mm or less, More preferably, it is 1.5 mm or less.
The method for forming the CIGS layer on the glass substrate is not particularly limited. However, since the glass plate of the present embodiment has a high glass transition temperature, the heating temperature for forming the CIGS layer is 500 to 700 ° C., preferably 550. It can be set to ˜700 ° C., more preferably 580 to 700 ° C., further preferably 600 to 700 ° C., particularly preferably 620 to 700 ° C.

When using the glass plate of this embodiment only for the glass substrate of a CIGS solar cell, a cover glass etc. are not restrict | limited in particular. Other examples of the composition of the cover glass include ordinary soda lime glass that is widely used.
When using the glass plate of this embodiment as a cover glass of a CIGS solar cell, it is preferable that the thickness of a cover glass shall be 3 mm or less, More preferably, it is 2 mm or less, More preferably, it is 1.5 mm or less.
In the production of CIGS solar cells, the method of assembling the cover glass on the glass substrate having the CIGS layer is not particularly limited, but when assembled by heating, the heating temperature is 500 to 700 ° C., preferably 600 to 700 ° C. be able to.

It is preferable to use the glass plate of the present embodiment together with the glass substrate and the cover glass of the CIGS solar cell because the average thermal expansion coefficient is equivalent and thermal deformation or the like during the assembly of the solar cell does not occur.

Further, since the glass plate according to the present embodiment has the above characteristics, it can be preferably used for a CdTe solar cell.

In the super straight type structure adopted in the CdTe solar cell, since the glass substrate is exposed to the outside, the glass plate of the present embodiment having high glass strength is also suitably used as a glass substrate for CdTe solar cells.
In addition, since it has a high glass transition temperature, it can be formed at a high temperature when forming the CdTe layer, which can contribute to the power generation efficiency of the CdTe solar cell.

When the glass plate of this embodiment is applied to a glass substrate of a CdTe solar cell, the thickness of the glass substrate is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1.5 mm or less. The method for forming the CdTe layer on the glass substrate is not particularly limited. However, since the glass substrate of the present embodiment has a high glass transition temperature, the heating temperature for forming the CdTe layer is preferably 500 to 700 ° C. Can be set to 550 to 700 ° C, more preferably 580 to 700 ° C, still more preferably 600 to 700 ° C, and particularly preferably 620 to 700 ° C.

When using the glass plate of this embodiment only for the glass substrate of a CdTe solar cell, back plate glass etc. are not restrict | limited in particular. Other examples of the composition of the back glass include ordinary soda lime glass which is generally used widely.
When using the glass plate of this embodiment as a back plate glass of a CdTe solar cell, the thickness of the back plate glass is preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1.5 mm or less.
In the production of CdTe solar cells, the method of assembling the back glass on the glass substrate having the CdTe layer is not particularly limited, but when assembled by heating, the heating temperature is 500 to 700 ° C., preferably 600 to 700 ° C. Can do.
When the glass plate of this embodiment is used in combination with the glass substrate and the back plate glass of the CdTe solar cell, the average thermal expansion coefficient is equivalent, so that thermal deformation or the like during solar cell assembly does not occur, which is preferable.

<CIGS solar cell>
Next, a CIGS solar cell according to an embodiment of the present invention will be described.
The CIGS solar cell of this embodiment includes a glass substrate, a cover glass, and a Cu—In—Ga—Se photoelectric conversion layer disposed between the glass substrate and the cover glass. At least one of the substrate and the cover glass is the glass plate of this embodiment.

Hereinafter, the CIGS solar cell of this embodiment is demonstrated in detail using attached drawing. The present invention is not limited to the attached drawings.
FIG. 1 is a cross-sectional view schematically illustrating an example of the CIGS solar cell of the present embodiment.

In FIG. 1, the CIGS solar cell 1 of the present embodiment includes a glass substrate 5, a cover glass 19, and a CIGS layer 9 between the glass substrate 5 and the cover glass 19. At least one of the glass substrate 5 and the cover glass 19 is the glass plate of the present embodiment described above. When the glass substrate 5 is the glass plate according to the present embodiment, the effect of Na diffusion can be enhanced. Further, since both the glass substrate 5 and the cover glass 19 are the glass plates according to the present embodiment, it is possible to prevent peeling and the like by matching the thermal expansion coefficients.

The solar cell 1 has the back electrode layer of Mo film which is the plus electrode 7 on the glass substrate 5, and has the CIGS layer 9 on it. The composition of the CIGS _{layer, Cu (In 1-X Gax} ) Se 2 can be exemplified. x represents the composition ratio of In and Ga, and 0 <x <1.

On the CIGS layer 9, as a buffer layer 11, a CdS (cadmium sulfide), ZnS (zinc sulfide) layer, ZnO (zinc oxide) layer, Zn (OH) ₂ (zinc hydroxide) layer, or a mixed crystal layer thereof. Have A transparent conductive film 13 such as ZnO, ITO, or Al doped ZnO (AZO) is provided through the buffer layer 9, and an extraction electrode such as an Al electrode (aluminum electrode) that is a negative electrode 15 is provided thereon. Have. An antireflection film may be provided at a necessary place between these layers. In FIG. 1, an antireflection film 17 is provided between the transparent conductive film 13 and the negative electrode 15.

Further, a cover glass 19 may be provided on the negative electrode 15, and if necessary, the resin between the negative electrode and the cover glass may be sealed with resin or may be bonded with a transparent resin for bonding.
In this embodiment, the edge part of a CIGS layer or the edge part of a solar cell may be sealed. As a material for sealing, the same material as the glass plate of this embodiment, other glass, resin etc. are mentioned, for example.
Note that the thickness of each layer of the solar cell shown in the accompanying drawings is not limited to the drawings.

The CIGS solar cell of the present embodiment uses the glass plate of the present embodiment as a glass substrate, and in the second stage of the CIGS layer deposition process, the CIGS layer is deposited under heating conditions of 500 ° C. or higher. High power generation efficiency can be obtained. The heating temperature in the second stage is preferably 550 ° C. or higher, more preferably 580 ° C. or higher, further preferably 600 ° C. or higher, and particularly preferably 620 ° C. or higher.
Other processes other than the CIGS layer forming process in the CIGS solar cell manufacturing method, for example, the buffer layer and transparent conductive film layer forming process, etc., may be performed in the same manner as the normal CIGS solar cell manufacturing process. it can.

<CdTe solar cell>
Next, a CdTe solar cell according to an embodiment of the present invention will be described.
The CdTe solar cell of this embodiment includes a glass substrate, a back plate glass, and a CdTe photoelectric conversion layer (CdTe layer) disposed between the glass substrate and the back plate glass. At least one of the back plate glasses is the glass plate of the present embodiment.
Alternatively, in the configuration of the CdTe solar cell, a solar cell using a back film having water resistance and oxygen resistance permeability may be used instead of the back glass.

Hereinafter, the solar cell in the present embodiment will be described in detail with reference to the accompanying drawings. The present invention is not limited to the attached drawings.
FIG. 2 is a cross-sectional view schematically showing an example of the embodiment of the CdTe solar cell of the present embodiment.
In FIG. 2, a solar cell (CdTe solar cell) 21 according to this embodiment includes a glass substrate 22 having a thickness of 1 to 3 mm, a back plate glass 27 having a thickness of 1 to 3 mm, and a gap between the glass substrate 22 and the back plate glass 27. A CdTe layer 25 having a thickness of 3 to 15 μm is provided. At least one of the glass substrate 22 and the back plate glass 27 is the glass plate of the present embodiment described above. Further, since both the glass substrate 22 and the back plate glass 27 are the glass plates according to the present embodiment, it is possible to prevent peeling and the like by matching the thermal expansion coefficients.

The CdTe solar cell 21 has a transparent conductive film 23 having a thickness of 100 to 1000 nm on a glass substrate 22. The heating temperature when forming the CdTe layer or the transparent conductive film is 500 ° C. or higher, preferably 550 ° C. or higher, more preferably 580 ° C. or higher, further preferably 600 ° C. or higher, and particularly preferably 620 ° C. or higher.

The transparent conductive film 23, for example, _In 2 _{O 3} or the like doped with doped _In 2 _{O 3} and F of Sn and the like. A buffer layer 24 (eg, CdS layer) having a thickness of 50 to 300 nm is provided on the transparent conductive film 23, and a CdTe layer 25 is provided on the buffer layer 24. Further, on the CdTe layer 25, a back electrode 26 (for example, a carbon electrode doped with Cu or a Mo electrode) having a thickness of 100 to 1000 nm is provided, and a back plate glass 27 is provided on the back electrode 26. The back electrode 26 and the back plate glass 27 are preferably sealed with a resin or bonded with an adhesive resin.

In the present embodiment, the end of the CdTe layer or the end of the solar cell may be sealed. As a material for sealing, the same material as the glass substrate for CdTe solar cells of this embodiment, other glass materials, resin, etc. are mentioned, for example.
In addition, the thickness of each layer of the solar cell shown in the attached drawings is not limited to the drawings.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

Table 1 shows examples (Examples 1 to 5) and comparative examples (Examples 6 to 11) of the glass plate of the present embodiment. In addition, the composition ratio of Table 1 is shown in mass% on the basis of oxide.

The raw materials of each component of the glass were prepared so as to have the glass composition shown in Table 1, and 0.1 part by mass of SO _{3 in} terms of SO ₃ was added to the raw material with respect to 100 parts by mass of the raw material for the glass plate component. Using a platinum crucible, the mixture was heated at 1650 ° C. for 3 hours for dissolution. In Table 1, the blending amount of Fe ₂ O ₃ is based on the mother composition (SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, SrO, BaO, ZrO ₂ , Na ₂ O, and K ₂ O). ) The mass part with respect to 100 mass parts is shown.

In melting, a platinum stirrer was inserted and stirred for 1 hour to homogenize the glass. Subsequently, the molten glass was poured out, formed into a plate shape, and then cooled to obtain a glass plate.

The average thermal expansion coefficient (unit: × 10 ⁻⁷ / ° C.), glass transition temperature Tg (unit: ° C.), density (unit: g / cm ³ ), and viscosity of 10 ² dPa · s of the glass plate thus obtained. Temperature (T2) (unit: ° C.), temperature (T4) (unit: ° C.) at which the viscosity becomes 10 ⁴ dPa · s, devitrification temperature (TL) (unit: ° C.), and Na diffusion amount were measured. .
The results are also shown in Table 1. The measuring method of each physical property is shown below.

In addition, although measured about the glass plate in the Example, each physical property is the same value with a glass plate and a glass substrate. A glass substrate can be obtained by processing and polishing the obtained glass plate.

(1) Average coefficient of thermal expansion at 50 to 350 ° C .: measured using a differential thermal dilatometer (TMA) and determined from JIS R3102 (1995).
(2) Tg: Tg is a value measured using TMA, and was determined according to JIS R3103-3 (fiscal 2001).

(3) Density: About 20 g of glass lump containing no foam, cut out from a glass plate, was measured by Archimedes method.

(4) Viscosity: Measured using a rotational viscometer, temperature T2 (dissolvable reference temperature) when viscosity η is 10 ² dPa · s, and temperature when viscosity η is 10 ⁴ dPa · s T4 (reference temperature for moldability) was measured.
(5) Devitrification temperature (TL): 5 g of glass lump cut out from the glass plate was placed on a platinum dish and held in an electric furnace at a predetermined temperature for 17 hours. The maximum temperature at which crystals were not deposited on the glass lump surface and inside was defined as the devitrification temperature.

(6) Na diffusion amount: The obtained glass plate was used for a solar cell substrate, an evaluation solar cell was prepared as shown below, and the Na diffusion amount was evaluated using the solar cell.
The production of the solar cell for evaluation will be described below with reference to FIG. In FIG. 1, a sample in which the glass substrate 5, the positive electrode 7, and the CIGS layer 9 were formed was prepared and used for evaluating the Na diffusion amount.
The obtained glass plate was processed into a size of 3 cm × 3 cm and a thickness of 1.1 mm to obtain a glass substrate. A Mo (molybdenum) film was formed as a positive electrode 7 on the glass substrate 5 by a sputtering apparatus. Film formation was performed at room temperature to obtain a Mo film having a thickness of 500 nm.
On the positive electrode 7 (Mo film), a CuGa alloy layer is formed with a CuGa alloy target using a sputtering apparatus, and then an In layer is formed using an In target to form an In—CuGa precursor film. A film was formed. Film formation was performed at room temperature. The thickness of each layer was adjusted so that the composition of the precursor film measured by fluorescent X-rays was Cu / (Ga + In) ratio of 0.8 and Ga / (Ga + In) ratio of 0.25. Obtained.

The precursor film was heat-treated in an argon and hydrogen selenide mixed atmosphere (hydrogen selenide is 5% by volume with respect to argon) using an RTA (Rapid Thermal Annealing) apparatus. First, hold at 500 ° C. for 10 minutes as the first stage, react Cu, In, Ga and Se, and then hold at 580 ° C. for another 30 minutes to grow CIGS crystals as the second stage. CIGS layer 9 was obtained. The thickness of the obtained CIGS layer 9 was 2 μm.

After the completion of the second stage of the heat treatment by the RTA apparatus, the sample was measured for the integrated intensity of ²³ Na in the CIGS layer by secondary ion mass spectrometry (SIMS). The value of Na diffusion amount shown in Table 1 is a relative amount when the glass plate used in Example 8 is 118.

As shown in each table, the glass plates of the examples (Examples 1 to 5) have a glass transition temperature (Tg) of 640 ° C. or higher, and have high heat resistance from the result of the glass transition temperature. -TL). Moreover, it is predicted that the amount of Na diffusion is large and the power generation efficiency is high. Moreover, T2 and T4 were low and it was the range suitable for manufacture of a glass plate. Moreover, the average coefficient of thermal expansion and the density were also in a range suitable for the glass plate.
In Examples 1 and 2, 2 (SrO—BaO) + (K ₂ O—Na ₂ O) is limited to 11.5% or less, and by increasing the amount of BaO, a sufficient amount of Na diffusion can be obtained. Heat resistance could be improved.
In Examples 3 and 5, 2 (SrO—BaO) + (K ₂ O—Na ₂ O) is limited to 11.5% or less, and by increasing the amount of Na ₂ O, heat resistance can be sufficiently obtained. , Na diffusion amount could be increased.

In Example 6, the amount of BaO and Na ₂ O were mainly small, and the target Na diffusion amount and devitrification characteristics were not obtained.
In Example 7, the amount of BaO was mainly small and the amount of Na diffusion decreased.
In Examples 6 and 7, the glass transition temperature decreased.
In Example 8 and Example 11, 2 (SrO—BaO) + (K ₂ O—Na ₂ O) exceeded 11.5%, and the devitrification characteristics were deteriorated.
In Examples 9 and 10, 2 (SrO—BaO) + (K ₂ O—Na ₂ O) exceeded 11.5%, the amount of Al ₂ O ₃ was large, and the devitrification characteristics deteriorated.
In Example 10, there was a problem that the amount of SrO was large, Tg was increased, and the meltability of the glass raw material was lowered.

Since the glass plate of the present invention can obtain excellent heat resistance and devitrification characteristics and increase the amount of Na diffusion to increase power generation efficiency, it can be preferably used for a glass substrate for solar cells. Furthermore, a predetermined average coefficient of thermal expansion, glass density, solubility at the time of production of a glass plate and formability are good, and it can be preferably used for a glass substrate for a solar cell.
The entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2013-238666 filed on November 19, 2013 are incorporated herein by reference. .

DESCRIPTION OF SYMBOLS 1 CIGS solar cell 5 Glass substrate 7 Positive electrode 9 CIGS layer 11 Buffer layer 13 Transparent conductive film 15 Negative electrode 17 Antireflection film 19 Cover glass 21 CdTe solar cell 22 Glass substrate 23 Transparent conductive film 24 Buffer layer 25 CdTe layer 26 Back electrode 27 Back plate glass

Claims

In terms of mass percentage based on the following oxide, SiO 2 is 45 to 65%, Al 2 O 3 is 9 to 17%, B 2 O 3 is 0 to 1%, MgO is 0 to 2%, and CaO is 1 to 12%. %, SrO 1-15%, BaO 1.4-12%, ZrO 2 2-6%, Na 2 O 5-10%, K 2 O 2-10%, MgO + CaO + SrO + BaO 15- A glass plate which is 30% and 2 (SrO—BaO) + (K 2 O—Na 2 O) is 11.5% or less.
The glass plate according to claim 1, wherein the content of Na 2 O is 5.6 to 10%.
The glass plate according to claim 1 or 2, wherein SrO + BaO is 6 to 18%.
The glass plate according to claim 1 or 2, wherein SrO-BaO is 7.5% or less.
The glass plate according to claim 1 or 2, wherein Na 2 O + K 2 O is 7 to 15%.
The glass plate according to claim 1 or 2, wherein K 2 O-Na 2 O is 2% or less.
The temperature (T4) at which the viscosity becomes 10 4 dPa · s is 1230 ° C. or lower, the temperature (T2) at which the viscosity becomes 10 2 dPa · s is 1650 ° C. or lower, and the relationship between the T4 and the devitrification temperature (TL) is T4 The glass plate according to any one of claims 1 to 6, wherein -TL> 0 ° C.
The glass plate according to any one of claims 1 to 6, wherein the glass transition temperature is 640 ° C or higher.
The glass plate according to any one of claims 1 to 6, having an average coefficient of thermal expansion of 70 x 10 -7 to 90 x 10 -7 / ° C.