JP2002299657A - Photovoltaic module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent Na from a translucent insulating board from entering a photovoltaic element and deteriorating characteristics since the amount of oxygen is large, and to reduce absorption at a long wavelength. SOLUTION: The photovoltaic module 30 has a plurality of photovoltaic elements 31 having the lamination structure of a transparent conductive film 6, an amorphous or a microcrystalline conductive type semiconductor layer 4, and a crystal-based semiconductor substrate 1 from the surface of a light reception surface side at least at the light reception surface side of nearly a plate-like photovoltaic module 31. In the transparent conductive film 6 of the photovoltaic element 31, carrier density is set to less than 6×10<20> /cm<3> . The amount of oxygen is large, thus preventing Na from a translucent insulating board from entering the photovoltaic element and deteriorating characteristics, and reducing the absorption at the long wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photovoltaic module.

[0002]

2. Description of the Related Art The structure of a conventional photovoltaic element is, for example, as follows.
It is disclosed in JP-A-9-129904. This structure has a transparent conductive film (ITO) / p-type amorphous semiconductor film / i-type amorphous semiconductor film / n-type crystalline semiconductor substrate / i
Type amorphous semiconductor film / n-type amorphous semiconductor film / transparent conductive film (ITO) / backside electrode film.

[0003]

The above-mentioned conventional photovoltaic element is constructed by combining a known module structure, that is, a plurality of solar cell elements, with a light-transmitting insulating substrate on a light-receiving surface side and a weather-resistant member on a rear surface side. When a structure in which a solar cell element is interposed therebetween and a sealing resin is filled in an internal gap is used, the following problem occurs.

A constant temperature and humidity (85 ° C. 90
%) At 1000H, some of the characteristics deteriorated.

[0005] As a result of pursuing and analyzing the cause, Na precipitates from a tempered glass having a composition of Na ₂ O · CaO · 5SiO ₂ which is a light-transmitting insulating substrate on the light receiving surface side, and Na precipitates through the sealing resin. It was clarified that the photovoltaic element was reached and the characteristics were lowered. In particular, in the constant temperature / humidity test, moisture penetrates from between the sealing resin and the tempered glass, and decomposes its components on the inner surface of the tempered glass to form Na (or N
It is considered that (a ion) is precipitated.

[0006] The present invention has been made to solve such a problem of the structure, and an object of the present invention is to provide a photovoltaic module having high reliability under constant temperature and humidity.

[0007]

The main constitution of the present invention is as follows.
A plurality of light beams having a laminated structure of a transparent conductive film, an amorphous or microcrystalline conductive semiconductor layer, and a crystalline semiconductor substrate on at least the light receiving surface side of the substantially plate-shaped photovoltaic element from the surface side. A photovoltaic device comprising a photovoltaic element, a light-transmitting insulating substrate on the light-receiving surface side, and a weather-resistant member on the back side, the photovoltaic element sandwiching the solar cell element therebetween, and filling an internal gap with a sealing resin. In the module, the transparent conductive film of the photovoltaic element has a carrier density of less than 6 × 10 ²⁰ / cm ³ .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, the photovoltaic element of this embodiment is a square having a size of about 100 mm square and a thickness of about 1 mm.
A crystalline semiconductor substrate 1 made of n-type single crystal silicon (resistivity = about 0.5 to 4 Ω · cm) having a thickness of 00 to 500 μm is provided. Then, on the front surface of the crystalline semiconductor substrate 1, an amorphous semiconductor intrinsic semiconductor layer 2 (about 50 to 200 °) formed by using a plasma CVD method, and on the back surface of the crystalline semiconductor substrate 1, Amorphous silicon intrinsic semiconductor layer 3 (about 50 to 20) formed by a plasma CVD method.
0Å).

On the intrinsic semiconductor layer 2, a p-type amorphous silicon conductive semiconductor layer 4 (about 50 to 200 °) formed by using a plasma CVD method, and on the back surface of the intrinsic semiconductor layer 3, a plasma CVD method is used. A conductive semiconductor layer 5 of n-type amorphous silicon (approximately 100 to 500 °) formed by using the same is provided.

Although the intrinsic semiconductor layers 2 and 3 and the conductive semiconductor layers 4 and 5 are made of amorphous silicon, microcrystalline silicon may be used.

On the front side, a transparent conductive film 6 made of indium tin oxide (= ITO) formed on the conductive type semiconductor layer 4, and on the back side, indium tin oxide (= ITO) formed on the conductive type semiconductor layer 5. A transparent conductive film 7 made of ITO is provided. In this embodiment, the transparent conductive film 6,
The thickness of No. 7 was set to 1000 °.

Further, as shown in FIG. 2, the photovoltaic element of this embodiment has a collector electrode 10 on the transparent conductive film 6 on the front surface and a collector electrode 20 on the transparent conductive film 7 on the rear surface side. I have. In FIG. 2, the plan view of the collector electrodes 10 and 20 viewed from the back side of the photovoltaic element is a plan view viewed from the front side (= FIG.
(A)), which is not shown.

As shown in the figure, the collector electrodes 10 and 20 are made of silver paste, and are formed by screen printing followed by heat treatment. In consideration of the adverse effect of the heat treatment on the transparent conductive film and the amorphous semiconductor layer, a low-temperature heat treatment type silver paste that can be formed at a heat treatment temperature of about 200 ° C. is used.

More specifically, the collecting electrodes 10 and 20 are composed of two bus electrode portions 11 and 21 (width about 2 mm) extending parallel to the side.
And a plurality of finger electrode portions 12 and 22 (width of about 50 μm, spacing of about 2 to 3 mm) extending orthogonally from the bus electrode portions 11 and 21.

The spectral sensitivity spectrum of the solar cell element having such a structure has a wide spectral sensitivity characteristic in a range of 400 to 1100 nm as disclosed in FIG. 2 of Japanese Patent No. 2614561. Therefore, it is important that the transparent conductive film not only has high transmittance for visible light (about 400 to 650 nm) but also has high transmittance for infrared rays of about 650 to 1100 nm.

FIG. 3 shows the spectral characteristics of the absorptance of the transparent conductive film (ITO). Curve A shows a conventional curve having a carrier density of 6 × 10 ²⁰ / cm ³ and a low resistance of 30 ° at 1000 °.
The transparent conductive film of Ω / □ is shown. It can be understood that absorption is large at a wavelength of 600 nm or more. This conventional transparent conductive film has a carrier density of 6 × 10 ²⁰ / cm.
^{3. The} resistivity was 3.0 × 10 ⁻⁴ Ω · cm.

In this embodiment, a long wavelength of 600 nm
A transparent conductive film having little absorption at the above wavelengths was obtained. The spectral sensitivity characteristics are shown in a curve B (test 1). In particular, absorption is small at a wavelength of 800 nm or more. Note that the transparent conductive film of curve B has a carrier density of 4 ×
10 ²⁰ / cm ³ and resistivity of 3.5 × 10 ⁻⁴ Ω · cm (1
35Ω / □ at 000 °).

Similarly, in the curve C (test 2) of the present embodiment, a transparent conductive film having little absorption at a long wavelength of 600 nm or more was obtained. The transparent conductive film of the curve C has a carrier density of 2 × 10 ²⁰ /
cm ³ and a resistivity of 4.0 × 10 ⁻⁴ Ω · cm (1000 °
40Ω / □).

It was confirmed that such a transparent conductive film having the spectral sensitivity characteristics of curves B and C in FIG. 3 can be achieved by increasing the amount of oxygen in the film. Specifically, the transparent conductive film of the present embodiment is made of an ITO target (In
(Mixture of ₂ O ₃ and SnO ₂ ) by introducing Ar gas and oxygen gas to form a film by sputtering, and by increasing the flow rate of O ₂ gas during the film formation, the oxygen in the transparent conductive film is increased. The amount could be increased. Specifically, the flow rate of oxygen gas during sputtering film formation is set to 2 SCCM (conventionally, curve A), 4
SCCM (test 1, curve B) and 7 SCCM (test 2, curve C) increased the amount of oxygen in the transparent conductive film. When the amount of oxygen is large, although absorption at a long wavelength can be suppressed, oxygen deficiency in the transparent conductive film is eliminated, electric conductivity is deteriorated, and resistance value is increased. This can be confirmed by comparing the physical properties of the transparent conductive film. The amount of oxygen in the transparent conductive film can be determined using the carrier density as an index. As the amount of oxygen increases, the carrier density decreases.

Next, the structure of a photovoltaic module using the plurality of photovoltaic elements 31 will be described. 4A is a plan view of the photovoltaic module, and FIG.
(A) is an AA cross-sectional view, and (c) is a main part enlarged cross-sectional view. In FIG. 4, the photovoltaic module 30 has a substantially rectangular shape in a plan view, and includes a translucent insulating substrate 32 made of tempered glass on a light receiving surface side and a metal foil such as Al on a back surface side formed of a resin film (for example, PVF ( And a three-layer weather-resistant member 33 sandwiched by polyvinyl phthalate)).
The translucent insulating substrate 32 made of tempered glass is made of Na ₂ O.C
It has a composition of aO · 5SiO _2. A plurality of solar cell elements 31 having a rectangular shape in a plan view are arranged between the translucent insulating substrate 32 and the weather-resistant member 33.

The plurality of solar cell elements 31 are sealed with the following structure. Before heating under pressure and vacuum such as PVB or EVA, a plurality of solar cell elements 31 are sandwiched between the sheet-like front sealing resin 34s and the back sealing resin 34r. By performing vacuum heating while applying pressure, the surface sealing resin 34 s and the back surface sealing resin 34 r are softened, and the sealing resin 34
Filled with s and 34r, the structure of FIG. 4 is completed.
Here, a transparent material is employed for the surface sealing resin 34s and the back surface sealing resin 34r. Further, the photovoltaic module 30 can have an outer frame made of a metal material such as aluminum mounted on the outer periphery thereof through a silicone resin or the like.

Next, by increasing the amount of oxygen in the transparent conductive film against the invasion of Na, which is a conventional problem,
A test was conducted to determine what could be prevented. As described above, regarding the deterioration of the characteristics of the photovoltaic element due to the intrusion of Na, the temperature and humidity (85 ° C. 90
%) Although it occurred at 1000H, the following Na acceleration test was adopted to accelerate and investigate the influence of Na intrusion. 0.05% aqueous NaHCO ₃ solution
Apply to the light receiving surface side of the photovoltaic element,
90%) The properties after 3H are evaluated. A photovoltaic element was prepared using each transparent conductive film shown in FIG. 3 described above, and the initial characteristics were compared, and the Pmax degradation rate after the Na acceleration test was compared. Table 1 shows the results.

[0023]

[Table 1]

From Table 1, it can be seen that in Tests 1 and 2 of the present embodiment, the deterioration rate was small due to the increase in the amount of oxygen in the transparent conductive film (the carrier density was reduced) as compared with the conventional test. Thus, a decrease in characteristics due to Na can be suppressed. Therefore, when the photovoltaic module is manufactured using the translucent insulating substrate 32 such as tempered glass containing Na, it is possible to prevent the characteristics of the photovoltaic element from deteriorating.

In the initial characteristics, tests 1 and 2
Can increase Isc and increase Pmax, which is the total output, because although the resistivity is higher than the conventional one (FF decreases), absorption at a long wavelength in the transparent conductive film can be reduced. are doing.

In the present embodiment, the improved transparent conductive film is used on the front and back surfaces of the photovoltaic element. However, even if it is used only on the surface which is the incident surface, the characteristics are sufficiently improved.

[0027]

According to the present invention, a transparent conductive film, an amorphous or microcrystalline conductive semiconductor layer and a crystalline semiconductor are arranged on at least the light receiving surface side of a substantially plate-shaped photovoltaic element from the surface side. Comprising a plurality of photovoltaic elements having a laminated structure of substrates,
A photovoltaic module using a light-transmitting insulating substrate on the light-receiving surface side and a weather-resistant member on the back side, sandwiching a solar cell element therebetween, and filling an internal gap with a sealing resin. The transparent conductive film of the power element has a carrier density of 6 × 10 ²⁰ /
Since the oxygen content is less than cm ^{3 and the} amount of oxygen is large, it is possible to prevent Na from the light-transmitting insulating substrate from entering the photovoltaic element and deteriorating the characteristics. Also, the transparent conductive film is
Since the carrier density is less than 6 × 10 ²⁰ / cm ³ and the amount of oxygen is large, absorption at a long wavelength can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a photovoltaic element in the process of manufacturing according to the present invention, wherein FIG. 1A is a plan view and FIG. 1B is a cross-sectional view taken along line AA in FIG.

FIG. 2 is a diagram showing a photovoltaic device of the present invention, wherein (a)
Is a plan view, (b) is an AA enlarged sectional view in (a),
(C) is an BB enlarged sectional view in (a).

FIG. 3 shows a graph of spectral characteristics.

FIG. 4 is a diagram showing a photovoltaic module of the present invention;
(A) is a top view, (b) is an AA sectional view in (a).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crystalline semiconductor substrate 2, 3 Intrinsic amorphous semiconductor layer 4, 5 Conductivity type amorphous semiconductor layer 6, 7 Transparent conductive film 10, 20 Collector electrode 11, 21 Bus electrode part 12, 22, Finger electrode part 30 Photovoltaic Power module 31 Photovoltaic element 32 Translucent insulating substrate 33 Weatherproof member 14s, 14r Sealing resin

Continued on the front page F term (reference) 5F051 AA02 AA04 AA05 BA18 CA15 CB27 DA04 DA20 FA04 FA10 FA14 GA04 JA03 JA04

Claims (7)

[Claims] 1. A laminated structure of a transparent conductive film, an amorphous or microcrystalline conductive semiconductor layer and a crystalline semiconductor substrate is formed on at least a light receiving surface side of a substantially plate-shaped photovoltaic element from the surface on the surface side. A plurality of photovoltaic elements having a light-transmitting insulating substrate on the light-receiving surface side, and a weather-resistant member on the back side, sandwiching the solar cell element therebetween, and sealing resin in an internal gap. A filled photovoltaic module, wherein the transparent conductive film of the photovoltaic element has a carrier density of less than 6 × 10 ²⁰ / cm ³ . 2. An amorphous or microcrystalline one conductivity type semiconductor layer and a transparent conductive film are laminated on a surface of a crystalline semiconductor substrate,
On the back surface of the substrate, a plurality of photovoltaic elements in which an amorphous or microcrystalline other conductive semiconductor layer is laminated, a light-transmitting insulating substrate on the light receiving surface side and a weather-resistant member on the back surface side are provided. A photovoltaic module in which the solar cell element is interposed therebetween and a sealing resin is filled in an internal gap, wherein the transparent conductive film of the photovoltaic element has a carrier density of 6 × 10 ²⁰ / A photovoltaic module having a size of less than ³ cm ³ . 3. The photovoltaic module according to claim 1, wherein said translucent insulating substrate contains Na. 4. The photovoltaic module according to claim 1, wherein an intrinsic semiconductor layer made of amorphous or microcrystalline is interposed between said semiconductor substrate and said semiconductor layer. 5. The photovoltaic module according to claim 1, wherein the transparent conductive film is made of indium tin oxide. 6. The transparent conductive film has a carrier density of 4 ×.
The photovoltaic module according to claim 1, wherein the photovoltaic module has a density of 10 ²⁰ / cm ³ or less. 7. The transparent conductive film has a resistivity of 3.5 × 1.
The photovoltaic module according to claim 1, wherein the photovoltaic module has a resistivity of 0 ⁻⁴ Ω · cm or more.