JP7627111B2 - Paste composition for forming rear reflector layer of PERC type solar cell - Google Patents

Description

The present invention relates to a paste composition for forming a back reflector layer of a PERC type solar cell, and more specifically, to a fired paste composition for forming a back reflector layer that reflects visible light and infrared light between the silicon semiconductor substrate and the back electrode layer of a crystalline PERC type solar cell.

Various research projects are being conducted to improve the conversion efficiency (power generation efficiency) and reliability of crystalline solar cells. Among these, PERC (passivated emitter and rear cell) solar cells, which have a passivation film made of silicon nitride, silicon oxide, aluminum oxide, etc. on the back side of a silicon semiconductor substrate, are considered to be promising in terms of high conversion efficiency.

In solar cells, various structures and reflective layers have been devised to increase the rear reflectance of incident light, as shown below.

For example, Patent Document 1 discloses a solar cell, and describes limiting the thickness of the silicon nitride film formed on the back surface of a silicon single crystal substrate to a specific range. Patent Document 2 discloses a polyimide resin composition for forming a back surface reflective layer of a solar cell and a method for forming a back surface reflective layer of a solar cell using the same, and describes the use of a resin composition containing an organic solvent, a polyimide resin dissolved in the organic solvent, and light-reflective particles (particularly white pigment particles) dispersed in the organic solvent as a polyimide resin composition for forming a back surface reflective layer of a BSF type cell. Patent Document 3 also discloses a composition for forming a reflective film and a reflective substrate using the composition, and describes the use of a composition (fired paste) containing a white pigment, glass, and resin as a composition for forming a reflective film, in which the glass contains zinc borosilicate glass.

JP 2008-172279 A JP 2012-69592 A JP 2012-140479 A

However, the technologies described in Patent Documents 1 and 3 have low reflectance for infrared light (1000 to 1200 nm) and do not achieve sufficient improvement in conversion efficiency. Also, in the technology described in Patent Document 2, the BSF type cell has a significantly inferior conversion efficiency compared to a PERC type cell equipped with a passivation film, and even if it is used as is in a PERC type cell, sufficient adhesion with the passivation film cannot be obtained, and there is a risk of interfacial coagulation and peeling occurring between the passivation film and the white pigment particles (e.g., TiO ₂ ) or between the TiO ₂ and the electrode.

Therefore, the present invention aims to provide a fired paste composition that can form a back reflector layer between the silicon semiconductor substrate and back electrode layer of a PERC solar cell, which can reflect not only visible light but also infrared light (1000 to 1200 nm) and has excellent adhesion to adjacent layers (passivation film and back electrode layer).

As a result of extensive research into achieving the above object, the inventors discovered that the above object can be achieved by forming a back reflective layer using a bakeable paste composition having a specific composition, and thus completed the present invention.

That is, the present invention relates to the following paste composition for forming a back reflector layer of a PERC type solar cell.
1. A bakeable paste composition for forming a back reflector layer between a silicon semiconductor substrate and a back electrode layer of a PERC type solar cell, comprising:
The present invention comprises a white pigment having an average particle size of 0.5 μm or more and 3.1 μm or less, and a white and/or colorless transparent glass powder, the total mass of the white pigment and the glass powder being in the range of 60 mass% or more and 75 mass% or less, and the mass ratio of the white pigment to the glass powder being in the range of 95:5 to 80:20.
A paste composition for forming a rear surface reflective layer, comprising:
2. The paste composition for forming a rear reflection layer according to item 1, wherein the white pigment is at least one selected from the group consisting of aluminum oxide particles, titanium oxide particles, magnesium oxide particles, selenium oxide particles, zinc oxide particles, barium sulfate particles, calcium sulfate particles, calcium carbonate particles, and barium carbonate particles.
3. The paste composition for forming a rear reflector according to item 1 or 2, wherein the glass powder contains at least one selected from the group consisting of lead (Pb), bismuth (Bi), vanadium (V), boron (B), silicon (Si), tin (Sn), phosphorus (P), and zinc (Zn).

According to the paste composition for forming a back reflector layer of a PERC type solar cell of the present invention, by applying and firing the paste composition, a back reflector layer can be formed between the silicon semiconductor substrate and the back electrode layer, which can reflect not only visible light but also infrared light (1000 to 1200 nm) and has excellent adhesion to adjacent layers (passivation film and back electrode layer).

1A and 1B are diagrams showing schematic cross-sectional structures of PERC type solar cells, in which (A) is an example of a conventional PERC type solar cell having no rear reflector layer, and (B) is an example of a PERC type solar cell of the present invention having a rear reflector layer.

The paste composition for forming a back surface reflective layer of a PERC type solar cell of the present invention will be described in detail below. In this specification, the range indicated by "to" means "above or below" unless otherwise specified. In addition, with regard to the positional relationship, the light receiving surface (side) of a PERC type solar cell will be referred to as the "front surface (side)" or "upper surface (side)", and the surface (side) opposite to the light receiving surface will be referred to as the "rear surface (side)" or "lower surface (side)".

First, we will explain an example of the structure of a PERC solar cell.

1. PERC Type Solar Cell Fig. 1(A) is a schematic diagram of a typical cross-sectional structure of a PERC type solar cell. A PERC type solar cell may include, as components, a silicon semiconductor substrate 1, an n-type impurity layer 2, an anti-reflective film (passivation film) 3, a grid electrode 4, a back electrode layer 5, an alloy layer 6, and a p+ layer 7. The back electrode layer 5 and the alloy layer 6 are collectively referred to as a back electrode 8.

In addition, FIG. 1(B), which shows an example of a PERC type solar cell of the present invention, is characterized in that in FIG. 1(A), a rear reflector layer 9 is formed by firing between the passivation film 3 on the rear surface of the silicon semiconductor substrate and the rear electrode layer 5.

As a result, the PERC solar cell of the present invention, which is equipped with a back surface reflective layer formed from the paste composition for forming a back surface reflective layer of the present invention, can reflect not only visible light but also infrared light (1000 to 1200 nm) of incident light, achieving a higher conversion efficiency than conventional products. In addition, the PERC solar cell of the present invention also has excellent adhesion between the back surface reflective layer and its adjacent layers (passivation film and back surface electrode layer).

The silicon semiconductor substrate 1 is not particularly limited, and for example, a p-type silicon substrate with a thickness of 180 to 250 μm is used.

The n-type impurity layer 2 is provided on the light-receiving surface side of the silicon semiconductor substrate 1. The thickness of the n-type impurity layer 2 is, for example, 0.3 to 0.6 μm.

Anti-reflection film 3 and grid electrode 4 are provided on the surface of n-type impurity layer 2. Anti-reflection film 3 is formed of, for example, a silicon nitride film and is also called a passivation film. Anti-reflection film 3 acts as a so-called passivation film, which can suppress the recombination of electrons on the surface of silicon semiconductor substrate 1, thereby making it possible to reduce the recombination rate of generated carriers. This increases the conversion efficiency of the PERC solar cell.

An anti-reflection film (passivation film) 3 is also provided on the back side of the silicon semiconductor substrate 1, that is, on the surface opposite the light receiving surface. In addition, a contact hole (opening) is formed on the back side of the silicon semiconductor substrate 1, penetrating the anti-reflection film (passivation film) 3 on the back side and formed so as to remove a part of the back side of the silicon semiconductor substrate 1. The method of forming the contact hole is not limited, but the so-called LCO (Laser contact opening) method, in which an opening is formed using laser irradiation or the like, is commonly used.

The back electrode layer 5 is formed so as to contact the silicon semiconductor substrate 1 through the contact hole. The back electrode layer 5 is generally a member formed from a paste composition containing conductive powder such as aluminum powder (which may include aluminum alloy powder) and is formed into a predetermined pattern shape. As shown in Figures 1(A) and (B), the back electrode layer 5 may be formed so as to cover the entire back surface of the PERC type solar cell, or may be formed so as to cover the contact hole and its vicinity. The main component of the back electrode layer 5 is generally aluminum, so the back electrode layer 5 is generally an aluminum electrode layer.

The back electrode layer 5 is formed, for example, by applying an aluminum paste composition in a predetermined pattern shape and firing it. The application method is not particularly limited, and examples include known methods such as screen printing. The aluminum paste composition is applied, dried as necessary, and then fired for a short time at a temperature above the melting point of aluminum (about 660°C) to form the back electrode layer 5. When applying the paste composition for forming a back reflector of the present invention, the paste composition for forming a back reflector of the present invention is applied to the back surface of the passivation film on the back surface of the silicon semiconductor substrate, and then a contact hole is formed, followed by applying an aluminum paste composition and further firing the resulting product.

In the present invention, the firing temperature may be any temperature above the melting point of aluminum (approximately 660°C), but is preferably about 750 to 950°C, and more preferably about 780 to 900°C. The firing time can be set appropriately according to the firing temperature within a range in which the desired rear reflector layer 9 and rear electrode layer 5 are formed.

When fired in this manner, the aluminum contained in the aluminum paste composition diffuses into the silicon semiconductor substrate 1. As a result, an aluminum-silicon (Al-Si) alloy layer (alloy layer 6) is formed between the back electrode layer 5 and the silicon semiconductor substrate 1, and at the same time, a p+ layer 7 is formed as an impurity layer due to the diffusion of aluminum atoms. In addition, a back reflector layer 9 is formed by firing.

The p+ layer 7 can prevent electron recombination and improve the collection efficiency of generated carriers, providing the so-called back surface field (BSF) effect.

2. Paste composition for forming a rear surface reflection layer of the present invention The paste composition for forming a rear surface reflection layer of the present invention (also referred to as the "paste composition of the present invention") is a fired paste composition for forming a rear surface reflection layer between a silicon semiconductor substrate and a rear surface electrode layer of a PERC type solar cell,
The composition is characterized in that it contains a white pigment having an average particle size of 0.5 μm or more and 3.5 μm or less, and a white and/or colorless and transparent glass powder, the total mass of the white pigment and the glass powder is in the range of 60 mass % or more and 80 mass % or less, and the mass ratio of the white pigment to the glass powder is in the range of 98:2 to 60:40.

According to the paste composition of the present invention, by applying and baking the paste composition, a back surface reflection layer can be formed between the silicon semiconductor substrate and the back surface electrode layer, which can reflect not only visible light but also infrared light (1000 to 1200 nm) and has excellent adhesion to adjacent layers (passivation film and back surface electrode layer).

The paste composition of the present invention contains at least the white pigment, the glass powder, and an organic vehicle described below as its constituent components. The constituent components of the paste composition of the present invention are described below.

(White pigment)
The white pigment used in the present invention has an average particle size of 0.5 μm or more and 3.5 μm or less. By having the average particle size in the above range, it is possible to exhibit high reflectivity not only for visible light but also for infrared light. This makes it possible to efficiently reflect incident light transmitted through a silicon semiconductor substrate and increase the conversion efficiency of a PERC type solar cell.

The above average particle size refers to the number average particle size. The white pigment (inorganic particles) in the paste composition of the present invention exists in the form of primary particles in which the aggregates are completely loosened, and in the form of secondary particles in which multiple primary particles are aggregated. Here, the particle size of the inorganic particles in the paste composition refers to the particle size of the primary particles that are not aggregated, and the particle size of the aggregates of the primary particles. One method for measuring the average particle size of the inorganic particles in the paste composition is to directly observe the particles with a SEM (scanning electron microscope) and calculate the number average particle size.

Specific examples of the white pigment include at least one selected from the group consisting of aluminum oxide particles, titanium oxide particles, magnesium oxide particles, selenium oxide particles, zinc oxide particles, barium sulfate particles, calcium sulfate particles, calcium carbonate particles, and barium carbonate particles. Among these, at least one of aluminum oxide and titanium oxide (particularly titanium dioxide) is preferred in terms of optical properties such as refractive index, thermal expansion coefficient, and environmental resistance. Note that although white pigments are inorganic particles, as will be clear to those skilled in the art, they are distinguished from glass powder, which will be described later, both in terms of components and concepts.

The shape of the white pigment is not particularly limited, and any suitable shape such as spherical, elliptical, scaly, or irregular can be used.

(Glass powder)
The glass powder in the present invention is white and/or colorless and transparent glass powder. In the paste composition of the present invention, the glass powder imparts adhesion between the white pigments, between the silicon semiconductor substrate and the white pigment, and further between the white pigment and the back electrode layer.

The glass powder preferably contains at least one selected from the group consisting of lead (Pb), bismuth (Bi), vanadium (V), boron (B), silicon (Si), tin (Sn), phosphorus (P), and zinc (Zn). Specifically, glass powder containing lead, or lead-free glass powder such as bismuth-based, vanadium-based, tin-phosphorus-based, zinc borosilicate-based, and alkali borosilicate-based glass powder can be used. In particular, considering the effects on the human body, it is desirable to use lead-free glass powder.

The softening point of the glass powder is preferably 650°C or lower. The volume average particle diameter D50 of the glass particles constituting the glass powder is preferably 1 to 3 μm.

In the paste composition of the present invention, the mass ratio of the white pigment to the glass powder is in the range of 98:2 to 60:40, and preferably in the range of 95:5 to 80:20. This range ensures high reflectance for visible light and infrared light while providing excellent adhesion between the rear reflective layer and adjacent layers (passivation film and rear electrode layer).

(Organic Vehicle)
The paste composition of the present invention further contains an organic vehicle as a binder. As the organic vehicle, a material in which various additives and/or resins are dissolved in a solvent can be used. Alternatively, the organic vehicle may be a resin itself without containing a solvent.

Any known type of solvent can be used, specifically at least one selected from the group consisting of diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, and dipropylene glycol monomethyl ether.

Examples of various additives include one or more of antioxidants, corrosion inhibitors, defoamers, thickeners, tackifiers, coupling agents, electrostatic agents, polymerization inhibitors, thixotropic agents, and anti-settling agents. Specific examples that can be used include polyethylene glycol ester compounds, polyethylene glycol ether compounds, polyoxyethylene sorbitan ester compounds, sorbitan alkyl ester compounds, aliphatic polycarboxylic acid compounds, phosphate ester compounds, amide amine salts of polyester acids, oxidized polyethylene compounds, and fatty acid amide waxes.

As the resin, known types can be used, for example, thermosetting resins such as ethyl cellulose, nitrocellulose, polyvinyl butyral, phenolic resin, melamine resin, urea resin, xylene resin, alkyd resin, unsaturated polyester resin, acrylic resin, polyimide resin, furan resin, urethane resin, isocyanate compound, cyanate compound, etc.; polyethylene, polypropylene, polystyrene, ABS resin, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyimide, polyether sulfone, polyarylate, polyether ether ketone, polytetrafluoroethylene, silicone resin, etc., can be used alone or in combination of two or more types.

The ratio of resin, solvent, and various additives contained in the organic vehicle can be adjusted as desired, and can be, for example, the same component ratio as known organic vehicles.

In the paste composition of the present invention, the total mass of the white pigment and the glass powder is in the range of 60% by mass to 80% by mass, and preferably in the range of 75% by mass to 80% by mass. By being in this range, excellent adhesion between the back surface reflective layer and adjacent layers (passivation film and back surface electrode layer) can be obtained while ensuring high reflectance of visible light and infrared light.

The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples. Examples 1, 2, 5, and 6 are all reference examples.

Example 1
A paste composition for forming a _rear surface reflection layer was prepared _by mixing 36 parts by mass of spherical aluminum oxide powder having an average particle size of 0.5 μm, which is a typical white pigment, 24 parts by mass of white boric acid-based glass powder having the formula B 2 O 3 -Bi ₂ O ₃ -SrO-BaO-Sb ₂ O ₃ = 40/40/10/5/5 (mol %), and 40 parts by mass of a resin solution in which ethyl cellulose was dissolved in butyl diglycol using a known dispersing device (disper).

A PERC type solar cell for evaluation was fabricated using the following procedure. First, a silicon semiconductor substrate with a 180 μm thick passivation film was prepared, as shown in Figure 1, which had a top passivation film and a back passivation film (silicon nitride film). The silicon semiconductor substrate had a resistance of 3 Ω cm and was a known back passivation type single crystal.

Next, the back surface of the silicon semiconductor substrate was completely printed with the paste composition for forming the back surface reflection layer using a screen printer at 0.5 to 0.6 g/cell, and then dried at 100°C for 10 minutes.

Next, a YAG laser with a wavelength of 532 nm was used as a laser oscillator to form a contact hole with a width of 50 μm and a depth of 1 μm relative to the silicon semiconductor substrate on the back surface of the silicon semiconductor substrate by penetrating the coating of the paste composition for forming a back surface reflection layer after drying.

Next, a known aluminum paste was printed using a screen printer at 1.0 to 1.1 g/cell to cover the entire back surface (the surface on which the contact holes are formed), and then dried. Next, an Ag paste made using known technology was printed on the light-receiving surface.

Then, the substrate was sintered in an infrared belt furnace set at 800°C. This sintering formed a back electrode layer, and aluminum diffused into the silicon semiconductor substrate during sintering, forming an Al-Si alloy layer between the back electrode layer and the silicon semiconductor substrate, while at the same time forming a p+ layer (BSF layer) as an impurity layer due to the diffusion of aluminum atoms. This resulted in the creation of a PERC-type solar cell for evaluation.

In the evaluation of the obtained solar cell, those with a Jsc of 37.95 mA/ ^cm2 or more had improved reflectance of visible light and infrared light due to the rear reflective layer, and the reflectance was measured by illuminating infrared light with a wavelength of 1000 to 1200 nm from the light receiving surface side using an integrating sphere spectrophotometer, and the result was 50% or more.

To evaluate adhesion, mending tape (12 mm wide, manufactured by 3M) was applied to the surface of the back electrode layer formed on the silicon semiconductor substrate, with a length of approximately 3 cm, and then the tape was forcefully peeled off at a 45 degree angle to the silicon semiconductor substrate. The ratio of the total area of the part with aluminum attached to the area of the original mending tape was calculated using analysis software capable of binary processing. All adhesion evaluations were performed by the same person with the same posture, angle, force, and constant speed. Mending tape with no aluminum attached at all was rated A (good), and mending tape with even a small amount of aluminum attached was rated B (bad).

For the overall evaluation, a sample that satisfied both the Jsc of 37.95 mA/cm2 or ^more (i.e., the reflectance of visible light and infrared light was improved by the rear reflective layer) and the adhesion evaluation of A (good) was evaluated as A (good), and a sample that did not satisfy either of the criteria was evaluated as B (bad).

Details of each example are shown in Table 1.

Example 2
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 1, except that 42 parts by mass of spherical aluminum oxide powder having an average particle size of 0.8 μm and 18 parts by mass of white boric acid-based glass powder were used.

Example 3
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 1, except that 48 parts by mass of rod-shaped aluminum oxide powder having an average particle size of 1.0 μm and 12 parts by mass of white boric acid-based glass powder were used.

Example 4
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 1, except that 48 parts by mass of spherical aluminum oxide powder having an average particle size of 2.0 μm and 12 parts by mass of white boric acid-based glass powder were used.

Example 5
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 42 parts by mass of spherical titanium dioxide powder having an average particle size of 0.5 μm, 28 parts by mass of white boric acid-based glass powder, and 30 parts by mass of the resin solution were used.

Example 6
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 5, except that 49 parts by mass of spherical titanium dioxide powder having an average particle size of 1.0 μm and 21 parts by mass of white boric acid-based glass powder were used.

Example 7
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 5, except that 56 parts by mass of spherical titanium dioxide powder having an average particle size of 2.2 μm and 14 parts by mass of white boric acid-based glass powder were used.

Example 8
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 5, except that 56 parts by mass of spherical titanium dioxide powder having an average particle size of 3.1 μm and 14 parts by mass of white boric acid-based glass powder were used.

Comparative Example 1
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 1, except that 36 parts by mass of spherical titanium dioxide powder having an average particle size of 0.02 μm and 24 parts by mass of white boric acid-based glass powder were used.

Details of each comparative example are shown in Table 2.

Comparative Example 2
A paste composition for forming a rear reflector layer was prepared and evaluated in the same manner as in Example 1, except that 36 parts by mass of spherical titanium dioxide powder having an average particle size of 0.3 μm and 24 parts by mass of white boric acid-based glass powder were used.

Comparative Example 3
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 35 parts by mass of spherical titanium dioxide powder having an average particle size of 0.5 μm, 24 parts by mass of white boric acid-based glass powder, and 41 parts by mass of the resin solution were used.

Comparative Example 4
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 33 parts by mass of spherical titanium dioxide powder having an average particle size of 0.5 μm, 22 parts by mass of white boric acid-based glass powder, and 45 parts by mass of the resin solution were used.

Comparative Example 5
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 30 parts by mass of spherical titanium dioxide powder having an average particle size of 1.0 μm, 30 parts by mass of white boric acid-based glass powder, and 50 parts by mass of the resin solution were used.

Comparative Example 6
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 59 parts by mass of spherical titanium dioxide powder having an average particle size of 1.0 μm, 1 part by mass of white boric acid-based glass powder, and 40 parts by mass of the resin solution were used.

Comparative Example 7
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 56 parts by mass of spherical titanium dioxide powder having an average particle size of 3.6 μm, 14 parts by mass of white boric acid-based glass powder, and 30 parts by mass of the resin solution were used.

Comparative Example 8
A paste composition for forming a rear surface reflection layer was prepared and evaluated in the same manner as in Example 1, except that 48 parts by mass of spherical titanium dioxide powder having an average particle size of 1.0 μm, 12 parts by mass of black vanadium glass powder, and 40 parts by mass of the resin solution were used.

Comparative Example 9
The evaluation was carried out in the same manner as in Example 1, except that the back reflective layer was not formed.

Comparative Example 10
Similar to the technology described in Patent Document 2, a known aluminum paste was printed on the back surface of a BSF-type silicon single crystal substrate not including a passivation film as an evaluation substrate, a known silver paste was printed on the top surface of the silicon single crystal substrate, and the substrate was fired. After that, the aluminum sintered layer and the Al-Si alloy layer on the back surface were removed by hydrochloric acid etching to prepare a solar cell silicon substrate with an exposed BSF layer.

A paste composition for forming a rear reflector was prepared in the same manner as in Example 1 using 40 parts by weight of spherical titanium dioxide powder with an average particle size of 0.3 μm and 357 parts by weight of a 28% polyimide resin solution. The paste composition was applied in a predetermined pattern to the rear surface of the solar cell silicon substrate, dried at 250°C for 30 minutes, and finally a rear electrode was formed by aluminum deposition, and evaluated.

Comparative Example 11
The paste composition for forming a rear reflector prepared in Comparative Example 10 was applied to the PERC type solar cell for evaluation in Example 1, and an evaluation was performed.

As shown in Table 1, by forming a back reflective layer between the silicon semiconductor substrate and the back electrode layer of a PERC solar cell using the paste composition for forming a back reflective layer of the present invention, it is possible to obtain high reflectance not only for visible light but also for infrared light of 1000 to 1200 nm, and it is also found that adhesion with adjacent layers (passivation film and back electrode layer) is good.

1. Silicon semiconductor substrate 2. n-type impurity layer 3. Anti-reflection film (passivation film)
4. Grid electrode 5. Rear electrode layer 6. Alloy layer 7. p+ layer 8. Rear electrode 9. Rear reflector layer

Claims (3)

A fired paste composition for forming a back reflector layer between a silicon semiconductor substrate and a back electrode layer of a PERC type solar cell, comprising:
The present invention comprises a white pigment having an average particle size of 0.5 μm or more and 3.1 μm or less, and a white and/or colorless transparent glass powder, the total mass of the white pigment and the glass powder being in the range of 60 mass% or more and 75 mass% or less, and the mass ratio of the white pigment to the glass powder being in the range of 95:5 to 80:20.
A paste composition for forming a rear surface reflective layer, comprising: The paste composition for forming a rear reflector layer according to claim 1, wherein the white pigment is at least one selected from the group consisting of aluminum oxide particles, titanium oxide particles, magnesium oxide particles, selenium oxide particles, zinc oxide particles, barium sulfate particles, calcium sulfate particles, calcium carbonate particles, and barium carbonate particles. The paste composition for forming a rear reflector layer according to claim 1 or 2, wherein the glass powder contains at least one selected from the group consisting of lead (Pb), bismuth (Bi), vanadium (V), boron (B), silicon (Si), tin (Sn), phosphorus (P), and zinc (Zn).

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