JP6128128B2 - Glass substrate for solar cell and solar cell using the same - Google Patents

Description

  The present invention relates to a glass substrate used for a solar cell in which a photoelectric conversion layer is formed between glass substrates and a solar cell using the same. More specifically, a glass used for a Cu—In—Ga—Se solar cell or a CdTe solar cell in which a Cu—In—Ga—Se photoelectric conversion layer or a CdTe photoelectric conversion layer is formed between glass substrates. The present invention relates to a substrate and a solar cell using the same.

Group 11-13, 11-16 compound semiconductors having a chalcopyrite crystal structure and cubic or hexagonal 12-16 group compound semiconductors have a large absorption coefficient for light in the visible to near-infrared wavelength range. have. Therefore, it is expected as a material for high-efficiency thin film solar cells. Typical examples include Cu (In, Ga) Se ₂ (hereinafter referred to as “CIGS” or “Cu—In—Ga—Se”) and CdTe.

CIGS thin film solar cells (hereinafter also referred to as “CIGS solar cells”) and CdTe thin film solar cells (hereinafter also referred to as “CdTe solar cells”) are inexpensive and have an average coefficient of thermal expansion close to that of CIGS compound semiconductors. Therefore, soda lime glass is used as a substrate, and a solar cell is obtained.
In recent years, glass materials that can withstand high heat treatment temperatures have been proposed as glass substrates for CIGS solar cells (see, for example, Patent Documents 1 to 5).

Japanese Unexamined Patent Publication No. 11-135819 Japanese Unexamined Patent Publication No. 2010-118505 Japanese Patent Laid-Open No. 8-290938 Japanese Unexamined Patent Publication No. 2008-280189 Japanese Unexamined Patent Publication No. 2010-267965

  In a CIGS solar cell, a CIGS photoelectric conversion layer (hereinafter also referred to as a “CIGS layer”) is formed between glass substrates. To produce a solar cell with good power generation efficiency, heat treatment at a higher temperature is required. Preferably, the glass substrate is required to withstand it. However, Patent Documents 1 to 4 propose a glass composition having a relatively high annealing point, but the inventions described in Patent Documents 1 to 4 do not necessarily have high power generation efficiency.

  More specifically, in the inventions described in Patent Documents 2 and 4, solar cell glass having a high strain point and satisfying a predetermined average thermal expansion coefficient is proposed. However, the problem of patent document 2 is ensuring heat resistance and improving productivity, and the problem of patent document 4 is improving surface quality and improving devitrification resistance, both of which solve problems related to power generation efficiency. Not. Therefore, it cannot be said that the inventions described in Patent Documents 2 and 4 have high power generation efficiency.

  Further, in Patent Document 3, there is a proposal of a high strain point glass substrate close to that of Patent Document 2, but this is mainly intended for plasma display applications and has different problems, and the invention described in Patent Document 3 is high. It cannot be said that it has power generation efficiency.

  Furthermore, Patent Document 4 proposes a glass that contains a relatively large amount of boron oxide, has a high strain point, and satisfies a predetermined average thermal expansion coefficient. However, if a large amount of boron is present in the glass, as described in Patent Document 5, boron diffuses into the CIGS layer, which is a p-type semiconductor, and acts as a donor, which may reduce power generation efficiency. Furthermore, there is a problem in that a boron removal facility is required, which tends to increase costs.

  In Patent Document 5, boron in the glass is reduced, but the power generation efficiency is insufficient with the glass composition specifically described, and there is room for improvement in terms of further improvement in power generation efficiency.

On the other hand, in order to prevent peeling during or after the formation of the photoelectric conversion layer (CIGS layer) on the glass substrate, the glass substrate is required to have a predetermined average thermal expansion coefficient.
Furthermore, from the viewpoint of manufacturing and using CIGS solar cells, it is required to improve the strength and weight of the glass substrate, to have good solubility and formability during production of plate glass, and not to devitrify.
However, high power generation efficiency, high alkali diffusibility, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, and high melting during plate glass production in glass substrates used for CIGS solar cells It has been difficult to have a good balance of properties such as properties, good moldability, and good devitrification resistance.

  The present invention has high power generation efficiency, high alkali diffusivity, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, and high solubility during plate glass production, good moldability and good An object of the present invention is to provide a glass substrate that can be suitably used for CIGS solar cells and a solar cell using the same, having a good balance of properties such as anti-devitrification properties.

As a result of intensive investigations for solving the above-mentioned problems, the present inventors have established a specific composition range in the glass substrate for solar cells, so that high power generation efficiency, high alkali diffusibility, high glass transition temperature, predetermined A glass substrate having a good balance of properties such as average thermal expansion coefficient, high glass strength, low glass density, and high solubility, good moldability and good devitrification resistance during plate glass production. I found it.
That is, the present invention is as follows.

(1) In mass percentage display based on the following oxides:
The SiO ₂ 50~65%,
Al ₂ O ₃ 8-15%,
B ₂ O ₃ 0 to 1%
0-10% MgO
1 to 12% CaO,
6-12% SrO,
BaO 0-3%,
The ZrO ₂ 1 to 7%,
2-8% Na ₂ O,
K ₂ O 0-8%
15-30% of MgO + CaO + SrO + BaO is contained,
SrO / Na ₂ O is a glass substrate for a solar cell is 0.8 to 2.5.

(2) The glass substrate for solar cells according to (1), wherein the glass transition temperature is 640 ° C. or higher.
(3) The glass substrate for a solar cell according to (1) or (2), wherein the average thermal expansion coefficient is 70 × 10 ^{−7 to} 90 × 10 ⁻⁷ / ° C.

(4) The temperature at which the viscosity becomes 10 ⁴ dPa · s (T ₄ ) is 1230 ° C. or less, the temperature at which the viscosity becomes 10 ² dPa · s (T ₂ ) is 1650 ° C. or less, the T ₄ and the devitrification temperature (T _The glass substrate for solar cells according to any one of the above (1) to (3), wherein the relationship with _L ) is T ₄ −T _L ≧ −30 ° C.
(5) The glass substrate for solar cells according to any one of (1) to (4), wherein the density is 2.75 g / cm ³ or less.

(6) The glass substrate for a solar cell according to any one of (1) to (5), wherein the content of Al ₂ O ₃ is 8.5 to 14.5%.
(7) The glass substrate for solar cells according to any one of (1) to (6), wherein the content of CaO is 3 to 11%.
(8) The glass substrate for a solar cell according to any one of (1) to (6), wherein the content of CaO is 3 to 10%.

(9) The glass substrate for a solar cell according to any one of (1) to (8), wherein the content of Na ₂ O is 4 to 7%.
(10) The glass substrate for a solar cell according to any one of (1) to (9), wherein the sum of the contents of MgO + CaO + SrO + BaO is 17 to 23%.
(11) The glass substrate for a solar cell according to any one of (1) to (10), wherein the content of BaO is 2% or less.
(12) Any of the above (1) to (11), wherein SiO ₂ and Al ₂ O ₃ are contained in a range of 570% to 840% of the value represented by the formula of 9SiO ₂ + 15Al ₂ O ₃ The glass substrate for solar cells as described in any one.
(13) Any of (1) to (12) above, wherein Na ₂ O and K ₂ O are contained in a range of 14% to 44% in a value represented by a formula of 3Na ₂ O + 2K ₂ O The glass substrate for solar cells as described in one.
(14) A glass substrate, a cover glass, and a Cu—In—Ga—Se photoelectric conversion layer disposed between the glass substrate and the cover glass, and the glass substrate and the cover glass A Cu-In-Ga-Se solar cell in which at least the glass substrate is the glass substrate for a solar cell according to any one of (1) to (13).

(15) A glass substrate, a back plate glass, and a CdTe photoelectric conversion layer disposed between the glass substrate and the back plate glass, and at least the glass substrate of the glass substrate and the back plate glass is The CdTe solar cell which is a glass substrate for solar cells as described in any one of said (1)-(13).

  The glass substrate for solar cells of the present invention has high power generation efficiency, high alkali diffusibility, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, and high solubility during plate glass production, It has a good balance of properties such as good moldability and good devitrification resistance. Moreover, a solar cell with high power generation efficiency can be provided by using the solar cell glass substrate of the present invention. In particular, the glass substrate for a solar cell of the present invention is useful for a Cu—In—Ga—Se solar cell and a CdTe solar cell.

FIG. 1: is sectional drawing which represents typically an example of embodiment of the solar cell (CIGS solar cell) using the glass substrate for solar cells of this invention. FIG. 2 shows a solar cell (a) produced on a glass substrate for evaluation in the example and a cross-sectional view (b) thereof. FIG. 3 shows an evaluation CIGS solar cell on an evaluation glass substrate in which eight solar cells shown in FIG. 2 are arranged. FIG. 4 is a cross-sectional view schematically showing an example of an embodiment of a solar cell (CdTe solar cell) using the solar cell glass substrate of the present invention.

<The glass substrate for solar cells of this invention>
Hereinafter, the glass substrate for solar cells of the present invention will be described.

The glass substrate for solar cell of the present invention is a mass percentage display based on the following oxide,
The SiO ₂ 50~65%,
Al ₂ O ₃ 8-15%,
B ₂ O3 0 to 1%
0-10% MgO
1 to 12% CaO,
6-12% SrO,
BaO 0-3%,
The ZrO ₂ 1 to 7%,
2-8% Na ₂ O,
K ₂ O 0-8%
15-30% of MgO + CaO + SrO + BaO is contained,
SrO / Na ₂ O has a composition of 0.8 to 2.5.

  The glass transition temperature (Tg) of the glass substrate for solar cell of the present invention is preferably higher than the glass transition temperature of soda lime glass, and specifically, preferably 640 ° C. or higher. When the solar cell glass substrate of the present invention is used as a CIGS solar cell or a glass substrate of a CdTe solar cell, a CIGS photoelectric conversion layer (hereinafter referred to as a “CIGS photoelectric conversion layer”) is also simply referred to as a “CIGS layer” at a high temperature. ) Or a CdTe photoelectric conversion layer (hereinafter, “CdTe photoelectric conversion layer” is also simply referred to as “CdTe layer”) to ensure the formation of a glass transition temperature (Tg) of 645 ° C. or higher. More preferably, 650 ° C. or higher is further preferable, and 655 ° C. or higher is particularly preferable. In order not to raise the viscosity at the time of dissolution too much, it is more preferable to set it as 750 degrees C or less. More preferably, it is 720 degrees C or less, Most preferably, it is 690 degrees C or less.

Average thermal expansion coefficient at 50 to 350 ° C. of glass substrate for a solar cell of the present invention is preferably ^{70 × 10 -7 ~90 × 10 -7} / ℃. When the glass substrate for a solar cell of the present invention is used as a glass substrate for 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. Defects such as peeling easily occur. More preferably, it is 85 × 10 ⁻⁷ / ° C. or less.

In the solar cell glass substrate of the present invention, the relationship between the temperature (T ₄ ) at which the viscosity is 10 ⁴ dPa · s and the devitrification temperature (T _L ) is preferably T ₄ −T _L ≧ −30 ° C. . T ₄ The -T _L is lower than -30 ° C., devitrification is likely to occur at the time of sheet glass forming, there is a possibility that the molding of the glass plate becomes difficult. T ₄ -T _L is more preferably -20 ° C. or higher, more preferably -10 ° C. or higher, particularly preferably 0 ℃ or more, and most preferably 10 ° C. or higher. Here, the devitrification temperature refers to 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.

In consideration of moldability of the glass plate, that is, improvement in flatness and productivity, T ₄ is preferably 1230 ° C. or less. T ₄ is more preferably 1220 ° C. or less, and further preferably 1210 ° C. or less.

In addition, the glass substrate for a solar cell of the present invention has a temperature (T ₂ ) at which the viscosity becomes 10 ² dPa · s at 1650 ° C. in consideration of glass solubility, that is, improvement in homogeneity and productivity. The following is preferable. T ₂ is more preferably 1630 ° C. or less, and further preferably 1620 ° C. or less.

The solar cell glass substrate of the present invention preferably has a density of 2.75 g / cm ³ or less. When the density exceeds 2.75 g / cm ³ , the mass of the glass substrate becomes heavy, which is not preferable. The density is more preferably 2.73 g / cm ³ or less, and still more preferably 2.71 g / cm ³ or less. Moreover, when manufacturing a glass substrate 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.

The glass substrate for solar cells of the present invention preferably has a brittleness index value of less than 7000 m ^−1/2 . When the brittleness index value is 7000 m ^−1/2 or more, the glass substrate is easily broken in the production process of the solar cell, which is not preferable. More preferably 6900M ^-1/2 or less, more preferably ^{6800M -1/2} or less, particularly preferably ^{6700M -1/2} or less, and more preferably ^{6600M -1/2} or less. Moreover, when manufacturing a glass substrate 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 5000 m ^<-1/2 > or more normally.
In the present invention, the brittleness index value of the glass substrate for solar cell is obtained as “B” defined by the following formula (1) (J. Seghal, et al., J. Mat. Sci. Lett. , 14, 167 (1995)).
c / a = 0.0056B ^2/3 P ^1/6 ... Formula (1)
Here, P is the indentation load of the Vickers indenter, and a and c are the diagonal length of the Vickers indentation and the length of cracks generated from the four corners (the total length of two symmetrical cracks including the indenter), respectively. The brittleness index value B is calculated using the dimensions of Vickers indentations that have been implanted on the surface of various glasses and the formula (1).

  The reason for limiting to the said composition in the glass substrate for solar cells of this invention is as follows.

SiO ₂ :
SiO ₂ is a component that forms a skeleton of glass, and if it is less than 50% by mass (hereinafter, “mass%” is simply referred to as “%”, the same applies hereinafter), the heat resistance and chemical durability of the glass substrate. May decrease, and the average coefficient of thermal expansion may increase. Preferably it is 52% or more, More preferably, it is 53% or more, Especially preferably, it is 53.5% or more, More preferably, it is 54% 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. If the content is less than 8%, the glass transition temperature may be lowered. Moreover, there exists a possibility that an average thermal expansion coefficient may increase. Preferably it is 8.5% or more, More preferably, it is 9% or more, More preferably, it is 10% or more, Especially preferably, it is 11% or more, More preferably, it is 12% or more.

  However, if it exceeds 15%, the high-temperature viscosity of the glass increases, and the solubility may deteriorate. Further, the devitrification temperature is increased, and the moldability may be deteriorated. Preferably it is 14.5% or less, More preferably, it is 14% or less.

SiO ₂ and Al ₂ O ₃ :
Since SiO ₂ and Al ₂ O ₃ are components that increase the heat resistance of the glass substrate, 9SiO ₂ + 15Al ₂ O ₃ (ie, (SiO ₂ content% × 9) and (Al ₂ O ₃ content%) × The total content of 15) is preferably 570% or more. More preferably, it is 600% or more, More preferably, it is 630% or more, Most preferably, it is 660% or more. However, since SiO ₂ and Al ₂ O ₃ have the effect of increasing the high temperature viscosity of the glass and deteriorating the solubility, it is preferable that 9SiO ₂ + 15Al ₂ O ₃ is contained in a range of 840% or less. More preferably, it is 800% or less, More preferably, it is 760% or less, Most preferably, it is 720% 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 be lowered, or the average thermal expansion coefficient may be reduced, which is not preferable for the process of forming the photoelectric conversion layer. Moreover, devitrification temperature rises and it becomes easy to devitrify, and plate glass shaping | molding becomes difficult. Preferably, the content is 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. The same applies hereinafter.

MgO:
MgO can be contained because it has the effect of reducing the viscosity at the time of melting the glass and promoting the melting. Preferably it is 0.5% or more, More preferably, it is 1% or more. If it is 10% 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 7% or less, More preferably, it is 5%, More preferably, it is 3% or less, Most preferably, it is 2.5% or less.

CaO:
CaO has an effect of reducing the viscosity at the time of melting the glass and promoting the melting, so it can be contained in an amount of 1 to 12%. 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 substrate may increase. In addition, 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 6 to 12% because it has an effect of lowering the viscosity at the time of melting the glass and promoting the melting. Moreover, when using the glass substrate for solar cells of this invention as a glass substrate of a CIGS solar cell by containing SrO in a glass substrate, it accelerates | stimulates a sodium (Na) spreading | diffusion to the CIGS layer on a glass substrate. effective. Preferably it is 6.3% or more, More preferably, it is 6.5% or more, More preferably, it is 7% or more. However, if the content exceeds 12%, the density of the glass substrate increases and the brittleness index value may increase. It is preferably 11% or less, more preferably 10% or less, further preferably 9% or less, and particularly preferably 8.5% or less.

BaO:
BaO can be contained because it has the effect of lowering the viscosity at the time of melting the glass and promoting the melting. However, if it exceeds 3%, the average thermal expansion coefficient of the glass substrate increases, the density increases, and the brittleness index value may increase. In addition, the Young's modulus may be reduced. It is preferably 2.5% or less, and more preferably 2% or less.

ZrO ₂ :
ZrO ₂ has the effect of lowering the viscosity at the time of melting the glass and promoting the melting, so it is contained at 1% or more. If it is 7% 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. 6% or less is preferable, 5% or less is more preferable, and 4.5% or less is more preferable. Further, it is preferably 2% or more, more preferably 2.5% or more, further preferably 3% or more, and particularly preferably 3.5% or more.

TiO ₂ :
Since the inclusion of TiO ₂ devitrification temperature increases, it is preferred that TiO ₂ is not contained. However, the glass substrate for solar cells of the present invention is more likely to produce a bubble layer on the surface of the molten glass when the glass substrate is produced, as compared with ordinary 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 . The titanium compound may be an inorganic titanium compound (for example, 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 reason, TiO ₂ is allowed to be contained in the glass substrate by 0.2% or less as an impurity.

MgO, CaO, SrO and BaO:
About MgO, CaO, SrO and BaO, from the point of decreasing the viscosity at the time of melting the glass and promoting the melting, it may contain CaO and SrO, and may contain at least one selected from the group consisting of MgO and BaO. Their total amount (that is, the total amount of these alkaline earth metal oxides (RO) is also referred to as (MgO + CaO + SrO + BaO)) is 15% or more. However, if the total amount 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, 23% or less is more preferable, 20% or less is further more preferable, and 18% or less is especially preferable.

Na ₂ O:
Na ₂ O is a component that contributes to improving the power generation efficiency of the CIGS solar cell and is an essential component when the glass substrate for a solar cell of the present invention is used as a glass substrate of a CIGS solar cell. Moreover, since there exists an effect which lowers | hangs the viscosity in glass melting temperature and makes it easy to melt | dissolve, it is made to contain 2 to 8%. 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 2%, Na diffusion to the CIGS layer on the glass substrate becomes insufficient, and the power generation efficiency is also low. May be insufficient. The content is preferably 3% or more, and more preferably 4% or more.
If the Na ₂ O content exceeds 8%, 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 7.5% or less, more preferably 7% or less, and even more preferably 6.5% or less.

K ₂ O:
Since K ₂ O has the same effect as Na ₂ O, 0 to 8% is contained. However, if it exceeds 8%, the glass transition temperature is lowered, the average thermal expansion coefficient is increased, and the specific gravity may be increased. When contained, it is preferably 0.5% or more, more preferably 1% or more, and further preferably 3.5% or more. Further, it is preferably 7% or less, more preferably 6% or less, further preferably 5% or less, and particularly preferably 4.5% or less.

Na ₂ O and K ₂ O:
Na ₂ O and K ₂ O are components for contributing to improvement in power generation efficiency of the CIGS solar cell. Moreover, since it has the effect of lowering the viscosity at the glass melting temperature and facilitating melting, 3Na ₂ O + 2K ₂ O (that is, (Na ₂ O content% × 3) and (K ₂ O content% × 2)) The total content is preferably in the range of 14% or more. More preferably, it is 16% or more, further preferably 18% or more, and particularly preferably 20% or more. Since Na ₂ O and K ₂ O tend to increase the average thermal expansion coefficient and lower the glass transition temperature, it is preferable to contain 3Na ₂ O + 2K ₂ O in a range of 44% or less. More preferably, it is 40% or less, more preferably 36% or less, and particularly preferably 32% or less.

SrO to Na ₂ O ratio:
The ratio of SrO to Na ₂ O (SrO / Na ₂ O) is 0.8 or more. If the amount of SrO is small relative to the amount of Na ₂ O, the effect of promoting the diffusion of Na to the CIGS layer on the glass substrate tends to be weakened when a CIGS solar cell is produced. Preferably it is 0.9 or more, More preferably, it is 1.0 or more, More preferably, it is 1.1 or more. However, if it is 2.5 or more, the specific gravity of the glass substrate may be too large. It is preferably 2.1 or less, more preferably 1.8 or less, further preferably 1.6 or less, and particularly preferably 1.4 or less.

A glass substrate for a solar cell of the present invention are essentially 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 The glass mother composition contained in the range described above), but within the range that does not impair the object of the present invention, the following other components are divided by 1% or less, and the above-described TiO ₂ is included in the glass mother composition. You may contain 5% or less in total. 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.

Further, in order to improve the solubility and fining of the glass, a fining agent such as SO ₃ , F, Cl, SnO _{2 is} divided into the glass mother composition, and the total amount is 2%. These raw materials may be added to the mother composition raw material so as to contain at most%.
Further, in order to improve the chemical durability of the glass substrate, Y ₂ O ₃ and La ₂ O ₃ may be contained in the glass in an amount of 2% or less in total with respect to the glass mother composition.

Incidentally, a glass substrate for a solar cell of the present invention, 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 glass mother composition containing K ₂ O in the range described above) With respect to 100 parts by mass, the iron oxide has a content of 0.06 parts by mass or less in terms of Fe ₂ O _3. It is preferably included. 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, when the transmittance is unquestioned (for example, when used as a substrate for a CIGS solar cell), iron oxide is used as the above-mentioned mother from the viewpoint of use of a raw material with a low iron content and ease of heating during melting. The amount is preferably 0.2 parts by mass or less, more preferably 0.15 parts by mass or less, and further preferably 0.12 parts by mass or less based on Fe ₂ O _{3 with} respect to 100 parts by mass of the composition.
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 the present invention, examples of the iron oxide include a valve stem and iron oxide powder.

Further, the glass substrate for a solar cell of the present invention, 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 substrate for solar cells of the present invention is not limited to being formed by the float process, and may be manufactured by forming by the fusion process.

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

In the manufacturing process of 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 the enlargement of the solar cell is used. preferable.
The preferable aspect of the manufacturing method of the glass substrate for solar cells of this invention is demonstrated.

First, a molten glass obtained by melting a predetermined glass raw material is formed into a plate shape. For example, raw materials are prepared so that the obtained glass substrate has the composition described above, 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 pulling out the ribbon-shaped glass plate from the float forming furnace, it is cooled to room temperature by a cooling means, and after cutting, a glass substrate for solar cell is obtained.

<Use of glass substrate for solar cell of the present invention>
The glass substrate for solar cells of the present invention has a predetermined average thermal expansion coefficient, high glass strength, low glass density, and high solubility during plate glass production, good formability and good devitrification prevention, Furthermore, since it has a high glass transition temperature and high alkali diffusibility, it can contribute to power generation efficiency when used in a CIGS solar cell, and is therefore suitably used as a glass substrate for CIGS solar cells.
When the glass substrate for a solar cell of the present invention is applied to a glass substrate of a CIGS solar cell, the thickness of the glass substrate is preferably 3 mm or less, more preferably 2 mm or less, and further preferably 1.5 mm or less.
Further, the method for forming the CIGS layer on the glass substrate is not particularly limited, but since the glass transition temperature is high, the heating temperature for forming the CIGS layer is 500 to 700 ° C., preferably 550 to 700 ° C., more preferably. The temperature may be 580 to 700 ° C, more preferably 600 to 700 ° C, and particularly preferably 620 to 700 ° C.

When using the glass substrate for solar cells of this invention 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 soda lime glass.
When the glass substrate for a solar cell of the present invention is used as a cover glass for a CIGS solar cell, the thickness of the cover glass is preferably 3 mm or less, more preferably 2 mm or less, and further preferably 1.5 mm or less.
Moreover, in the manufacture 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.

When the glass substrate for a solar cell of the present invention is used in combination with a glass substrate and cover glass of a CIGS solar cell, the average thermal expansion coefficient is equivalent, so that thermal deformation or the like at the time of assembling the solar cell does not occur.
Moreover, the glass substrate for solar cells of the present invention has a predetermined average thermal expansion coefficient, high glass strength, low glass density, and high solubility, good moldability and good devitrification resistance during plate glass production. Therefore, it is suitably used as a glass substrate for CdTe solar cells.

Since the glass substrate is exposed to the outside in the super straight structure employed in the CdTe solar cell, the glass substrate for solar cell of the present invention having high glass strength is also suitably used as the glass substrate for CdTe solar cell.
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 substrate for a solar cell of the present invention 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 further preferably 1.5 mm or less. The method for forming the CdTe layer on the glass substrate is not particularly limited, but since the glass transition temperature is high, the heating temperature for forming the CdTe layer is 500 to 700 ° C., preferably 550 to 700 ° C., more preferably 580. -700 degreeC, More preferably, it is 600-700 degreeC, Most preferably, it can be set as 620-700 degreeC.

When using the glass substrate for solar cells of the present invention only for the glass substrate of CdTe solar cells, the back plate glass and the like are not particularly limited. Other examples of the composition of the back plate glass include soda lime glass.
When the glass substrate for a solar cell of the present invention is used 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 further 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 substrate for a solar cell of the present invention is used in combination with a glass substrate and a back plate glass of a 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 of the present invention>
Next, the CIGS solar cell of this invention is demonstrated.
The CIGS solar cell of the present invention has a glass substrate, a cover glass, and a Cu—In—Ga—Se photoelectric conversion layer disposed between the glass substrate and the cover glass, and the glass substrate. Among the cover glasses, at least the glass substrate is the glass substrate for solar cells of the present invention.

Hereinafter, the CIGS solar cell of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the attached drawings.
FIG. 1 is a cross-sectional view schematically showing an example of an embodiment of the CIGS solar cell of the present invention. In FIG. 1, the CIGS solar cell 1 of the present invention has a glass substrate 5, a cover glass 19, and a CIGS layer 9 between the glass substrate 5 and the cover glass 19. It is preferable that the glass substrate 5 is the glass substrate for solar cells of the present invention described above. 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 is _{Cu (In 1-x Ga x} ) 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 minus electrode 15, and if necessary, the gap between the minus electrode and the cover glass is resin-sealed or bonded with a transparent resin for bonding. As the cover glass, the glass substrate for a solar cell of the present invention may be used.
In the present invention, the end of the CIGS layer or the end of the solar cell may be sealed. As a material for sealing, the same material as the glass substrate for solar cells of this invention, other glass, 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.

The CIGS solar cell of the present invention uses the glass substrate for solar cells of the present invention as a glass substrate, and in the second stage of the CIGS layer deposition process, the CIGS layer is formed under heating conditions of 500 ° C. or higher. Higher 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 in the normal CIGS solar cell manufacturing process. .

<CdTe Solar Cell of the Present Invention>
Next, the CdTe solar cell of the present invention will be described.
The solar cell of the present invention 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, and the glass substrate and the back plate glass. Of these, at least the glass substrate is the glass substrate for solar cells of the present invention. Or in the structure of the said solar cell, the solar cell using the back film which has water resistance and oxygen-resistant permeability | transmittance instead of back plate glass may be sufficient.

Hereinafter, a solar cell in the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the attached drawings.
FIG. 4 is a cross-sectional view schematically showing an example of an embodiment of the CdTe solar cell of the present invention.
In FIG. 4, a solar cell (CdTe solar cell) 21 of the present invention has 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 thickness between the glass substrate 22 and the back plate glass 27. A CdTe layer 25 having a thickness of 3 to 15 μm. 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 glass substrate 22 is preferably composed of the glass substrate for solar cells of the present invention described above.
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 (for example, a 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, 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 on the CdTe layer 25, 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. The back plate glass 27 may use the glass substrate for a solar cell of the present invention.

In the present invention, 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 invention, 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.

EXAMPLES Hereinafter, although an Example and a manufacture example demonstrate this invention in more detail, this invention is not limited to these Examples and a manufacture example.
The Example (Examples 1-13, 17-31) and comparative example (Examples 14-16) of the glass substrate for solar cells of this invention are shown.

Table to prepare a raw material of each component so that the glass composition was displayed in 1-4, relative to 100 parts by weight of the raw material of the glass substrate component, 0.1 parts by mass of sulfate converted to SO _3, in the starting material The mixture was added and dissolved by heating at a temperature of 1650 ° C. for 3 hours using a platinum crucible. In Table 1-4, the amount of _Fe 2 _{O 3} is matrix composition _{(SiO 2, Al 2 O 3} , B 2 O 3, MgO, CaO, SrO, BaO, ZrO 2, Na 2 O, and K ₍ Glass mother composition containing ₂ O in the range described above) 100 parts by mass.

In melting, a platinum stirrer was inserted and stirred for 1 hour to homogenize the glass. Next, 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 ), brittleness index value (unit: unit) of the glass plate thus obtained. m ^−1/2 ), temperature at which viscosity becomes 10 ² dPa · s (T ₂ ) (unit: ° C.), temperature at which viscosity becomes 10 ⁴ dPa · s (T ₄ ) (unit: ° C.), devitrification temperature (T _L ) (unit: ° C.), Na diffusion amount, and power generation efficiency were measured and shown in Tables 1 to 4. 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. By processing and polishing the obtained glass plate, a glass substrate can be obtained.

(1) Average thermal expansion coefficient at 50 to 350 ° C .:
This average thermal expansion coefficient was measured using a differential thermal dilatometer (TMA), and was determined from the standard of JIS R3102 (1995).
(2) Tg:
Tg is a value measured using TMA, and was determined according to the standard of JIS R3103-3 (FY2001).

(3) Density:
The density was measured by Archimedes' method for about 20 g of glass lump that did not contain bubbles and was cut out from the glass plate.

(4) Brittleness index value:
For the brittleness index value, the brittleness index value is calculated using the dimensions of the above-described Vickers indentation that has been driven into the surface of the various glass plates and the above formula (1).

(5) Viscosity:
The viscosity is measured using a rotational viscometer, and the temperature T2 when the viscosity η is 10 ² dPa · s and the temperature T ₄ when the viscosity η is 10 ⁴ dPa · s. (Reference temperature for moldability) was measured.
(6) Devitrification temperature (T _L ):
As for the devitrification temperature, 5 g of a glass lump cut out from a glass plate was placed on a platinum dish and held in an electric furnace for 17 hours. The minimum value of the temperature at which crystals were not precipitated on the retained glass lump surface and inside was defined as the devitrification temperature.

(7) Power generation efficiency:
For the power generation efficiency, the obtained glass plate was used for a solar cell substrate, a solar cell for evaluation was produced as shown below, and the power generation efficiency was evaluated using this. The results are shown in Tables 1-4.
The production of the solar cell for evaluation will be described below with reference to FIGS.
The layer configuration of the solar cell for evaluation is substantially the same as the layer configuration of the solar cell shown in FIG. 1 except that it does not have the cover glass 19 and the antireflection film 17 of the solar cell in FIG.
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. On the glass substrate 5a, a Mo (molybdenum) film was formed as a plus electrode 7a by a sputtering apparatus. Film formation was performed at room temperature to obtain a Mo film having a thickness of 500 nm.
On the plus electrode 7a (Mo film), a CuGa alloy layer is formed with a CuGa alloy target by a sputtering apparatus, and then an In layer is formed using an In target, whereby an In—CuGa precursor film is formed. 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 using a RTA (Rapid Thermal Annealing) apparatus in a mixed atmosphere of argon and hydrogen selenide (hydrogen selenide is 5% by volume with respect to argon). First, hold for 10 minutes at 500 ° C. as the first stage, react with Cu, In, Ga and Se, and then hold for another 30 minutes at 580 ° C. to grow a CIGS crystal as the second stage. CIGS layer 9a was obtained. The thickness of the obtained CIGS layer 9a was 2 μm.

A CdS layer was formed as the buffer layer 11a on the CIGS layer 9a by the CBD (Chemical Bath Deposition) method. Specifically, first, cadmium sulfate having a concentration of 0.01M, thiourea having a concentration of 1.0M, ammonia having a concentration of 15M, and pure water were mixed in a beaker. Next, the CIGS layer was immersed in the above mixed solution, and the beaker was placed in a constant temperature bath whose water temperature was previously set to 70 ° C., and a CdS layer was formed to a thickness of 50 to 80 nm.
Further, a transparent conductive film 13a was formed on the CdS layer by a sputtering apparatus by the following method. First, a ZnO layer was formed using a ZnO target, and then an AZO layer was formed using an AZO target (ZnO target containing 1.5 wt% Al ₂ O ₃ ). Each layer was formed at room temperature to obtain a transparent conductive film 13a having a two-layer structure having a thickness of 480 nm.
An aluminum film having a thickness of 1 μm was formed as a U-shaped negative electrode 15a on the AZO layer of the transparent conductive film 13a by EB vapor deposition (where the U-shaped electrode length is 8 mm in length, 4 mm in width, electrode The width is 0.5 mm).

Finally, from the transparent conductive film 13a side to the CIGS layer 9a was scraped by mechanical scribing, and a cell was formed as shown in FIG. Fig.2 (a) is the figure which looked at one photovoltaic cell from the upper surface, FIG.2 (b) is sectional drawing of AA 'in Fig.2 (a). One cell has a width of 0.6 cm and a length of 1 cm, and the area excluding the negative electrode 15a is 0.5 cm ^{2. As} shown in FIG. 3, a total of eight cells are placed on one glass substrate 5a. Obtained.
A positive electrode 7a in which a CIGS solar cell for evaluation (that is, the glass substrate for evaluation 5a produced with the above eight cells) is installed on a solar simulator (Yamashita Denso Co., Ltd., YSS-T80A), and an InGa solvent is applied in advance. The positive terminal (not shown) was connected to the lower end of the U-shape of the negative electrode 15a, and the negative terminal 16a was connected to the voltage generator. The temperature in the solar simulator was controlled at a constant temperature of 25 ° C. with a temperature controller. Pseudo sunlight was irradiated, and after 60 seconds, the voltage was changed from -1 V to +1 V at an interval of 0.015 V, and the current values of each of the eight cells were measured.

The power generation efficiency was calculated by the following formula (2) from the current and voltage characteristics during irradiation. The values of the most efficient cell among the eight cells are shown in Tables 1 to 4 as the value of the power generation efficiency of each glass substrate. The illuminance of the light source used for the test was 0.1 W / cm ² .

Power generation efficiency [%] = V _oc [V] × J _sc [A / cm ² ] × FF [dimensionless] × 100 / illuminance [W / cm ² ] of the light source used for the test Equation (2)

The power generation efficiency is obtained by multiplying the open circuit voltage (V _oc ), the short circuit current density (J _sc ), and the fill factor (FF).
The open circuit voltage (V _oc ) is an output when the terminal is opened, and the short circuit current (I _sc ) is a current when the terminal is short circuited. The short-circuit current density (J _sc ) is I _sc divided by the area of the cell excluding the negative electrode.
The point that gives the maximum output is called the maximum output point, the voltage at that point is called the maximum voltage value (V _max ), and the current is called the maximum current value (I _max ). A value obtained by dividing the product of the maximum voltage value (V _max ) and the maximum current value (I _max ) by the product of the open circuit voltage (V _oc ) and the short circuit current (I _sc ) is obtained as a fill factor (FF). It is done. Using the above values, the power generation efficiency was determined.

(8) Na diffusion amount:
The amount of Na diffusion was measured immediately after the end of the second stage of the heat treatment using the RTA apparatus at the time of producing the solar cell for evaluation in the power generation efficiency evaluation in order to see the effect of the alkali diffusibility of the glass substrate. did. The measurement method is as follows.
After the completion of the second stage of the heat treatment by the RTA apparatus, the integrated intensity of ²³ Na in the CIGS layer is measured for the sample by secondary ion mass spectrometry (SIMS). The values described in Tables 1 to 4 are relative amounts when the glass substrate used in Example 12 is 100.
In addition, about the calculation value of Na diffusion amount in a present Example, about what actually measured Na diffusion amount among this Example, a regression coefficient is calculated | required and calculated by carrying out multiple regression analysis of Na diffusion amount with each composition component. It is a thing.
The residual amount of SO ₃ in the glass was 100 to 500 ppm.

As is clear from Tables 1 to 4, the glass substrates of Examples (Examples 1 to 13 and Examples 17 to 31) have a high glass transition temperature Tg and a large amount of Na diffusion. Therefore, it is considered that the CIGS layer can be formed at a high temperature, whereby the CIGS crystal grows well and the power generation efficiency is increased. Further, the glass substrate of Example (Example 1-9, Example 11 to 13) _is, T 4 -T _L is excellent in devitrification property because it is -30 ° C. or higher, the average thermal expansion coefficient of 70 × ^{10 -7} ~ It is 90 × 10 ⁻⁷ / ° C., the density is 2.75 g / cm ³ or less, it is lightweight, and the brittleness index value is less than 7000 m ^−1/2 , so that it has high strength. It has a good balance of properties.

The glass substrate for a solar cell of the present invention satisfies all of high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, and good devitrification preventing property during plate glass production. I understand. Therefore, the CIGS layer does not peel from the glass substrate with the Mo film, and when the solar cell is further assembled (specifically, when the glass substrate having the CIGS layer and the cover glass are heated and bonded), the glass substrate is Difficult to deform. Furthermore, since T ₂ is 1650 ° C. or lower and T ₄ is 1230 ° C. or lower, the solubility and formability at the time of plate glass production are excellent.

  On the other hand, since the glass substrate of the comparative examples (Examples 14 and 15) has a small amount of Na diffusion when a CIGS solar cell is produced, high power generation efficiency is not obtained.

Moreover, since the glass substrate of a comparative example (Example 16) has a low glass transition temperature, there is a problem in heat resistance. Therefore, it is difficult to form the CIGS layer at a high temperature. Moreover, since the specific gravity is large and the brittleness index value is 7000 m ^−1/2 or more, there is a problem in strength.

The glass substrate for solar cells of the present invention can be suitably used for a glass substrate for CIGS solar cells. Moreover, it is suitable also as a glass substrate for CdTe solar cells.
The glass substrate for a solar cell of the present invention can be used not only for a glass substrate for CIGS solar cells or CdTe solar cells, but also for a cover glass and a back glass, and further used for other solar cell substrates and cover glasses. You can also

The glass substrate for solar cell of the present invention has high power generation efficiency, high glass transition temperature, predetermined average thermal expansion coefficient, high glass strength, low glass density, and high solubility during plate glass production, good moldability and The solar cell can have a good balance of properties such as good devitrification resistance, and a solar cell with high power generation efficiency can be provided by using the solar cell glass substrate of the present invention. In particular, the glass substrate for a solar cell of the present invention is useful for a Cu—In—Ga—Se solar cell and a CdTe solar cell.
The entire contents of the description, claims, drawings and abstract of Japanese Patent Application No. 2012-198334 filed on September 10, 2012 are incorporated herein by reference. .

DESCRIPTION OF SYMBOLS 1 CIGS solar cell 5, 5a Glass substrate 7, 7a Positive electrode 9, 9a CIGS layer 11, 11a Buffer layer 13, 13a Transparent conductive film 15, 15a 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 (15)

In mass percentage display based on the following oxides,
The SiO ₂ 50~65%,
Al ₂ O ₃ of 11-15%,
B ₂ O ₃ 0 to 1%
0-10% MgO
1 to 12% CaO,
6 to 8.5 % of SrO,
BaO 0-3%,
The ZrO ₂ 3.5 ~7%,
2-8% Na ₂ O,
K ₂ O 0-8%
15-30% of MgO + CaO + SrO + BaO is contained,
A glass substrate for a solar cell SrO / Na ₂ O is 0.8 to 2.1.   The glass substrate for solar cells of Claim 1 whose glass transition temperature is 640 degreeC or more. Average thermal expansion coefficient at 50 to 350 ° C. is ^{70 × 10 -7 ~90 × 10 -7} / ℃, a glass substrate for a solar cell according to claim 1 or 2. The temperature (T ₄ ) at which the viscosity is 10 ⁴ dPa · s is 1230 ° C. or lower, the temperature (T ₂ ) at which the viscosity is 10 ² dPa · s is 1650 ° C. or lower, the T ₄ and the devitrification temperature (T _L ) a relationship _T 4 -T _L ≧ -30 ℃, a glass substrate for a solar cell according to any one of claims 1 to 3. The glass substrate for solar cells as described in any one of Claims 1-4 whose density is 2.75 g / cm < ³ > or less. The content of Al ₂ O ₃ is from 11 to 14.5%, a glass substrate for a solar cell according to any one of claims 1 to 5.   The glass substrate for solar cells according to any one of claims 1 to 6, wherein the content of CaO is 3 to 11%.   The glass substrate for solar cells according to any one of claims 1 to 6, wherein the content of CaO is 3 to 10%. The Na ₂ O content is 4-7%, the glass substrate for a solar cell according to any one of claims 1-8.   The glass substrate for solar cells as described in any one of Claims 1-9 whose sum of content of MgO + CaO + SrO + BaO is 17-23%.   The glass substrate for solar cells according to any one of claims 1 to 10, wherein the content of BaO is 2% or less. The SiO ₂ and _{Al 2 O 3, 9SiO 2 +} 15Al 2 value represented by the formula O ₃ is contained in the range 570% ～840%, according to any one of claims 1 to 11 Glass substrate for solar cells. The Na ₂ O and _{K 2 O,} 3Na 2 O + 2K value expressed by ₂ O formula is contained in a range of 14% to 44%, the sun according to any one of claims 1 to 12 Battery glass substrate.   A glass substrate, a cover glass, and a photoelectric conversion layer of Cu-In-Ga-Se disposed between the glass substrate and the cover glass, and at least the glass substrate and the cover glass The Cu-In-Ga-Se solar cell whose glass substrate is the glass substrate for solar cells as described in any one of Claims 1-13.   A glass substrate, a back plate glass, and a CdTe photoelectric conversion layer disposed between the glass substrate and the back plate glass, and at least the glass substrate of the glass substrate and the back plate glass is claimed. The CdTe solar cell which is a glass substrate for solar cells as described in any one of 1-13.

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