KR20200054563A - Backsheet for solar cell and solar cell module comprising the same - Google Patents

Abstract

Provided is a backsheet for a photovoltaic cell with high weather resistance. The backsheet for a photovoltaic cell comprises: an outer layer including a modified olefin resin; an intermediate layer including an unmodified olefin resin; and an inner layer including at least one of the unmodified olefin resin and the modified olefin resin. The outer layer, the intermediate layer, and the inner layer are formed to directly contact each other. The intermediate layer comprises a carbon black having an average particle diameter (D50) of more than 0 nm and 40 nm or less in an amount of 0.1 to 10% by weight in the intermediate layer, and a UV stabilizer in an amount of 0.1% to 3% by weight in the intermediate layer.

Description

Back sheet for solar cell and solar cell module including the same {BACKSHEET FOR SOLAR CELL AND SOLAR CELL MODULE COMPRISING THE SAME}

The present invention relates to a solar cell backsheet and a solar cell module comprising the same.

Recently, interest in solar cells has rapidly increased due to problems such as resource depletion and environmental pollution. The solar cell may sequentially include an upper layer, an upper sealing material layer, a solar cell layer, a rear sealing material layer, and a back sheet layer from the front to the rear.

The backsheet for solar cells mainly protects the solar modules from moisture. Backsheets for solar cells typically contain multiple layers formed from different materials, and each material and layer can serve a different purpose.

As the influence of UV irradiation has recently increased, the solar cell module is also forced to be affected by UV irradiation. When the back sheet for solar cells is deformed by UV irradiation, it cannot function properly to protect the solar cells, so the output of the solar cells may drop or the service life may decrease. Therefore, there is a need to develop a backsheet for solar cells that has excellent weather resistance even under the complex effects of external moisture and UV irradiation.

Background art of the present invention is disclosed in Korean Patent Publication No. 2013-7006390 or the like.

An object of the present invention is to provide a solar cell back sheet with high weather resistance.

Another object of the present invention is to provide a backsheet for a solar cell having a high elongation retention rate even when irradiated with UV in both the outer layer and the inner layer for a long period of time at high temperature and high humidity.

Another object of the present invention is to provide a backsheet for solar cells capable of minimizing the loss of reflectivity between the outer and inner layers.

Another object of the present invention is to provide a backsheet for solar cells having high reflectivity in both the outer and inner layers.

The solar cell back sheet of the present invention comprises an outer layer comprising a modified olefin resin; An intermediate layer comprising an unmodified olefin resin; And an unmodified olefin resin and an inner layer including at least one of a modified olefin resin, and the outer layer, the intermediate layer, and the inner layer are formed to be in direct contact with each other, and the intermediate layer has an average particle diameter (D50) greater than 0 nm and less than 40 nm. The carbon black of 1 to 10% by weight of the intermediate layer, UV stabilizer may include 0.1 to 3% by weight of the intermediate layer.

In one embodiment, the carbon black may have an average particle diameter (D50) of more than 0 nm and 20 nm or less.

In one embodiment, the UV stabilizer may include one or more of HALS-based, UV absorbers.

In one embodiment, the modified olefin resin of the outer layer may include an olefin resin is inserted rubber.

In one embodiment, the unmodified olefin resin of the intermediate layer may include 0% to 60% by weight of the unmodified polyethylene resin, and 40% to 100% by weight of the unmodified polypropylene resin.

In one embodiment, the non-modified olefin resin of the inner layer is a non-modified ethylene-based polyolefin resin, and the modified olefin resin of the inner layer may include a modified propylene-based polyolefin resin or a modified ethylene-based polyolefin resin.

In one embodiment, the solar cell backsheet may have an elongation retention ratio of Equation 1 below 50%:

<Equation 1>

Elongation retention rate = A / B x 100

(Equation 1 above,

B is the elongation of the solar cell backsheet before UV irradiation on the solar cell backsheet,

A is the elongation of the back sheet for solar cells after UV irradiation for 300 hours on the back sheet for solar cells at 85 ° C and relative humidity of 85%)

The solar cell module of the present invention may include a solar cell and a backsheet for the solar cell of the present invention disposed on one side of the solar cell.

The present invention provides a solar cell back sheet with high weather resistance.

The present invention provides a backsheet for a solar cell having a high elongation retention even when UV is irradiated from both the outer layer and the inner layer for a long period of time at high temperature and high humidity.

The present invention provides a solar cell backsheet capable of minimizing the loss of reflectivity between the outer and inner layers.

The present invention provides a solar cell backsheet having high reflectivity in both the outer and inner layers.

1 is a cross-sectional view of a solar cell back sheet according to an embodiment of the present invention
Figure 2 shows the elongation retention rate according to the UV irradiation time when UV irradiation from the outer layer side of the solar cell back sheet in the experimental example of the present invention.

The present invention will be described in more detail with reference to the accompanying drawings and embodiments of the present application. However, the technology disclosed in the present application is not limited to the drawings and embodiments described herein, and may be embodied in other forms. However, the embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete and that the spirit of the present application is sufficiently conveyed to those skilled in the art. In order to clearly describe the present invention, parts not related to the description are omitted. The length of each component described in the drawings is to better describe the present invention, and the present invention is not limited to the length and size.

Hereinafter, a back sheet for a solar cell according to an embodiment of the present invention will be described with reference to FIG. 1. 1 is a cross-sectional view of a solar cell backsheet according to an embodiment of the present invention.

Referring to FIG. 1, the solar cell backsheet is composed of a three-layer structure including sequentially formed outer layer 100, intermediate layer 200, and inner layer 300.

The outer layer 100, the intermediate layer 200, and the inner layer 300 are formed in direct contact with each other. The “direct contact” means that no other adhesive layer, adhesive layer or point adhesive layer is interposed between the outer layer 100 and the intermediate layer 200, and between the intermediate layer 200 and the inner layer 300. As described in detail below, the solar cell backsheet including the outer layer 100, the intermediate layer 200, and the inner layer 300 may be formed by triple coextrusion.

The outer layer 100 may protect the solar cell including the intermediate layer and the inner layer by being disposed on the outer layer, that is, the outer layer when the solar cell backsheet is mounted on the solar cell.

The outer layer 100 may be a single layer resin layer containing a modified olefin resin.

The modified olefin resin may include a modified olefin resin in which rubber is inserted between non-modified homo or random olefin resins. Rubber is embedded in a modified olefin resin, which can help improve the weather resistance of the solar cell backsheet. The rubber may be a C2-Rich system (copolymer system having a high ethylene content), but is not limited thereto. The rubber may be included in 60% to 80% by weight of the outer layer, preferably 70% to 80% by weight. Within the above range, weather resistance can be improved without affecting the efficiency of the solar cell.

The homo or random olefin resin may include at least one of low density, medium density or high density polyethylene resin and polypropylene resin, preferably polypropylene (PP) resin.

Preferably, the modified olefin resin may be a modified polypropylene (PP) resin.

The outer layer 100 may have a thickness of 25 μm to 300 μm, preferably 25 μm to 150 μm. In the above range, it is difficult to pass external UV and moisture, so that a crack or discoloration of the solar cell does not occur, and there may be no problem of rising manufacturing cost and difficulty in processing and handling.

Although not particularly limited, in one embodiment, the outer layer may not contain carbon black or UV stabilizers.

The intermediate layer 200 is formed between the outer layer 100 and the inner layer 300, and supports the outer layer and the inner layer while integrating the outer layer and the inner layer with each other.

The present invention has an average particle diameter (in the middle layer disposed between the outer layer and the inner layer) rather than the outer layer and the inner layer which are relatively affected by external UV irradiation and moisture in the back sheet for a solar cell having three layers of outer layer, intermediate layer and inner layer ( D50) It was possible to improve the weather resistance of the solar cell backsheet by including carbon black of more than 0 nm and 40 nm or less in an amount of 1 wt% to 10 wt% and a UV stabilizer in 0.1 wt% to 3 wt%. This will be described in detail.

The intermediate layer 200 includes carbon black having an average particle diameter (D50) of 0 nm to 40 nm. In the above range, even when UV is irradiated from both the outer layer and the inner layer for a long period of time at high temperature and high humidity, the elongation retention rate is high and the weather resistance is excellent, and the loss of reflectivity of the backsheet for solar cells in both directions of the outer layer and the inner layer can be minimized. The "average particle size (D50)" means a particle size corresponding to 50% by weight in the particle size distribution curve of carbon black, and can be measured by a conventional method known to those skilled in the art.

In one embodiment, the backsheet for a solar cell may have an elongation retention rate of 50% or more, for example, 50% to 80%, represented by Formula 1 below. Within the above range, even if the solar cell is exposed to an external environment (moisture or UV) for a long time, the output power of the solar cell may not be caused to be caused:

<Equation 1>

Elongation retention rate = A / B x 100

(Equation 1 above,

B is the elongation of the solar cell backsheet before UV irradiation on the solar cell backsheet,

A is the elongation of the back sheet for solar cells after UV irradiation for 300 hours on the back sheet for solar cells at 85 ° C and relative humidity of 85%)

The UV irradiation may include irradiating with a metal halide lamp at 1000 W / m ² . The UV irradiation may be performed on the inner layer side or the outer layer side of the solar cell backsheet.

Preferably, the carbon black may have an average particle diameter (D50) of more than 0 nm and 20 nm or less.

Carbon black is contained in 1% to 10% by weight of the intermediate layer. In the above range, even when UV is irradiated from both the outer layer and the inner layer for a long period of time at high temperature and high humidity, the elongation retention rate is high and the weather resistance is excellent, and the loss of reflection of the backsheet for the solar cell in both directions of the outer layer and the inner layer can be minimized and dispersed in the middle layer There can be no problems with sex. Preferably, the carbon black may be included in 1% to 5% by weight of the intermediate layer.

The intermediate layer contains 0.1 to 3% by weight of UV stabilizer. In the above range, even when UV is irradiated from both the outer layer and the inner layer for a long period of time at high temperature and high humidity, the weather resistance is high and the elongation retention rate is excellent. Preferably, the UV stabilizer may be included in 0.1% to 2% by weight of the intermediate layer.

UV stabilizers may include conventional UV stabilizers known to those skilled in the art, but may preferably include one or more of HALS-based, UV absorbers.

The intermediate layer 200 includes the above-described carbon black and UV stabilizer in the non-modified olefin resin. When the above-mentioned modified olefin resin is used in place of the non-modified olefin resin in the intermediate layer, there may be a problem of increased manufacturing cost and a decrease in heat resistance.

The unmodified olefin resin is 0% to 60% by weight of the unmodified polyethylene (PE) resin, preferably 30% to 60% by weight, preferably 40% to 100% by weight of the unmodified polypropylene (PP) resin It may include a weight% to 70% by weight. In the above range, adhesion between the intermediate layer and the inner layer can be maximized.

The intermediate layer 200 may have a thickness of 25 μm to 300 μm, preferably 150 μm to 300 μm. In the above range, it is difficult to pass external UV and moisture, so that a crack or discoloration of the solar cell does not occur, and there may be no problem of rising manufacturing cost and difficulty in processing and handling.

The inner layer 300 is disposed on the cell side of the solar cell to protect the solar cell.

In one embodiment, the inner layer 300 may include at least one of a non-modified olefin resin and a modified olefin resin. The non-modified olefin resin may include a non-modified ethylene-based polyolefin resin (eg, a non-modified polyethylene resin), and the modified olefin resin is a modified propylene-based polyolefin resin (eg, a modified polypropylene resin) or a modified ethylene-based polyolefin resin (eg : Modified polyethylene resin).

The modified polypropylene-based olefin resin may be grafted polypropylene-based, and modified polyethylene-based olefin resin may be Ethylene octene rubber or Ethylene butene rubber, but is not limited thereto.

Preferably, the inner layer may be an unmodified polyethylene resin.

The inner layer 300 may have a thickness of 25 μm to 300 μm, preferably 25 μm to 100 μm. In the above range, the adhesion between the EVA encapsulant and the intermediate layer 200, the adhesion between the intermediate layer 200 and the inner layer 300 And excellent durability.

Although not particularly limited, in one embodiment, the inner layer may not include carbon black or UV stabilizers.

The outer layer, the intermediate layer, and the inner layer may each further contain conventional additives such as antioxidants and flame retardants.

The solar cell back sheet may have a thickness of 200 μm to 500 μm, preferably 220 μm to 400 μm. In the above range, it can be used as a back sheet for solar cells.

Hereinafter, a method of manufacturing a solar cell back sheet will be described.

The backsheet for solar cells can be formed by triple coextrusion to form the above-described inner layer, middle layer and outer layer structures. Specifically, each composition forming an inner layer, an intermediate layer, and an outer layer is formed, and each composition is extruded in a molten form through various sheet-forming dies. In the case of coextrusion, the die and feed block are molded so that the extrudate leaving the die cools to form a multi-layer solar cell backsheet. Each composition may be extruded at 130 ° C to 280 ° C, preferably 160 ° C to 250 ° C, but is not limited thereto.

Hereinafter, the solar cell module of the present invention will be described.

The solar cell module may include a solar cell and a back sheet for a solar cell of the present invention.

The solar cell may include a conventional solar cell that can convert light into electrical energy. For example, silicon-based solar cells (c-Si-based or mc-Si-based solar cells) may be included. The solar cell module may further include the above-described sealing material layer.

Hereinafter, the configuration and operation of the present invention through embodiments of the present invention will be described in more detail. However, the following examples are intended to help understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Example  One

As the composition for forming the outer layer, a modified polypropylene resin (including C2-Rich rubber) was used.

As a composition for forming an intermediate layer, a mixture containing 40% by weight of unmodified polyethylene resin and 60% by weight of unmodified polypropylene resin, carbon black (average particle diameter (D50) 20nm), HALS series as UV stabilizer (SABO®STAB UV62, SONGWON) It includes, and based on the solid content, the carbon black in the composition contains 1% by weight, and the UV stabilizer contains 1.5% by weight.

An unmodified polyethylene resin was used as a composition for forming an inner layer.

The prepared outer layer forming composition, intermediate layer forming composition, and inner layer forming composition were injected into each sheet-forming die and coextruded to prepare a back sheet for a solar cell having a three-layer structure thickness of 300 μm.

Example  2 to Example  3

A solar cell back sheet was prepared in the same manner as in Example 1, except that the average particle diameter and content of carbon black in the composition for forming an intermediate layer in Example 1 were changed as shown in Table 1 below.

Comparative example  One

In Example 1, a solar cell backsheet was prepared in the same manner as in Example 1, except that the carbon stabilizer and TiO ₂ (average particle diameter (D50): 37 nm) were not included according to Table 1, without carbon black. .

Comparative example  2

In Example 1, a solar cell backsheet was prepared in the same manner as in Example 1 except that carbon black was not included and UV stabilizer and talc (average particle diameter (D50): 40 nm) were included according to Table 1 below.

Comparative example  3

Modified polypropylene resin (including C2-Rich-based rubber), carbon black (average particle diameter (D50) 20 nm) as a composition for forming an outer layer, HALS series (SABO® STAB UV62, SONGWON) as a UV stabilizer, and based on solid content In the composition, carbon black contains 1% by weight and UV stabilizer contains 1.5% by weight.

The composition for forming the intermediate layer comprises a composition comprising 40% by weight of unmodified polyethylene resin and 60% by weight of polypropylene resin. Includes. Carbon black and UV stabilizers are not included in the composition for forming the intermediate layer.

An unmodified polyethylene resin was used as a composition for forming an inner layer.

A backsheet for a solar cell was prepared in the same manner as in Example 1 using the composition for forming an outer layer, a composition for forming an intermediate layer, and a composition for forming an inner layer.

The physical properties of Table 1 below were evaluated for the solar cell backsheets prepared in Examples and Comparative Examples, and the results are shown in Table 1 and FIG. 2.

(1) Elongation retention rate (unit:%): The elongation retention rate of the solar cell back sheet was evaluated. The prepared solar cell backsheet was irradiated with UV at an intensity of 1000 W / m ² using a metal halide lamp at 85 ° C. and 85% relative humidity. At this time, UV irradiation was performed on the outer and inner layers of the solar cell backsheet, respectively. Elongation retention was calculated according to the UV irradiation time. The elongation of the solar cell back sheet before UV irradiation was measured, and the elongation of the solar cell back sheet after UV irradiation was calculated according to Equation 1 above. Table 1 shows the elongation retention rate after 300 hours of UV irradiation. The elongation was measured according to ASTM D882.

(2) Reflectance (unit:%): The reflectance was measured on the inner and outer layers, respectively, using a reflectometer, Solidspec-3700 (SHIMADZU), at a wavelength of 550 nm for the solar cell backsheet.

(3) Shrinkage (unit:%): A sample was prepared by cutting the solar cell back sheet to the size of MD x TD (10 cm x 10 cm). The prepared specimen was left at 150 ° C for 30 minutes. The length shrinkage was calculated according to the following Equation 2 by measuring the lengths of MD and TD before standing at 150 ° C for 30 minutes and after standing at 150 ° C for 30 minutes.

<Equation 2>

Length shrinkage = (C-D) / C x 100

(Equation 2 above,

C is the length before leaving the back sheet for the solar cell at 150 ° C for 30 minutes,

D is the length after leaving the back sheet for the solar cell at 150 ° C for 30 minutes)

(4) Surface temperature (unit: ° C): The surface temperature of the solar cell back sheet was evaluated. The manufactured solar cell backsheet was irradiated with UV at the outer layer side of the solar cell backsheet at an intensity of 1000 W / m ² using a metal halide lamp at 85 ° C. and 85% relative humidity. After 300 hours of UV irradiation, the surface temperature of the outer layer was measured.

Example Comparative example One 2 3 One 2 3 Carbon black (＠ middle layer) D50 20 35 40 - - - content One One 10 0 0 0 UV stabilizer (＠middle layer) 1.5 1.5 1.5 1.5 1.5 0 TiO ₂ (＠ middle layer) 0 0 0 14 0 0 Talc (＠middle layer) 0 0 0 0 14 0 Carbon black (outer layer) D50 - - - - - 20 content 0 0 0 0 0 One UV stabilizer (outer layer) 0 0 0 0 0 1.5 Elongation retention rate Inner layer investigation 75 58 71 One One 74 Outer layer investigation 77 62 72 One 2 32 reflectivity Inner layer 88.5 88.9 87.9 90.2 91.7 89.1 Outer layer 89.1 89.7 88.2 90.7 92.0 4.7 Shrinkage MD 0.42 0.45 0.39 0.52 0.43 0.42 TD 0.45 0.47 0.49 0.59 0.49 0.44 Surface temperature 95.7 95.6 96.8 93.2 93.9 103.6

As shown in Table 1, the backsheet for solar cells of the present invention has a high elongation retention rate even when irradiated with UV in both the outer and inner layers for a long period of time at high temperature and high humidity, and minimizes the loss of reflectivity between the outer and inner layers to minimize the loss of reflectivity between the outer and inner layers. The reflectance was high and the degree of surface temperature rise was low even under long-term UV irradiation at high temperature and high humidity. As shown in Figure 2, the solar cell back sheet of the present invention had a high elongation retention when irradiated with UV in the outer layer direction for a long time at high temperature and high humidity.

On the other hand, as shown in Table 1 and Figure 2, Comparative Example 1 and Comparative Example 2, which does not contain carbon black and UV stabilizer in the intermediate layer, and Comparative Example 3, which includes carbon black and UV stabilizer in the outer layer, are used for a long period of time at high temperature and high humidity. When UV was irradiated in both directions of the outer layer and the inner layer, elongation retention was low in at least one of the outer layer and the inner layer.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (8)

An outer layer comprising a modified olefin resin;
An intermediate layer comprising an unmodified olefin resin; And
It consists of an inner layer containing at least one of a non-modified olefin resin and a modified olefin resin, and the outer layer, the intermediate layer and the inner layer are formed to directly contact each other,
The intermediate layer is an average particle diameter (D50) of more than 0nm and less than 40nm carbon black is 0.1 wt% to 10 wt% of the interlayer, and a UV stabilizer is 0.1 wt% to 3 wt% of the interlayer, the solar cell backsheet .
The method of claim 1, wherein the carbon black has an average particle diameter (D50) of more than 0nm and 20nm or less, a solar cell backsheet.
The method of claim 1, wherein the UV stabilizer is HALS-based, A solar cell backsheet comprising one or more of the UV absorbers.
The back sheet for solar cells according to claim 1, wherein the modified olefin resin of the outer layer includes an olefin resin in which rubber is inserted.
The backsheet for a solar cell according to claim 1, wherein the non-modified polyolefin resin of the intermediate layer comprises 0% to 60% by weight of the non-modified polyethylene resin and 40% to 100% by weight of the non-modified polypropylene resin.
The back sheet for a solar cell according to claim 1, wherein the non-modified olefin resin of the inner layer is a non-modified ethylene-based polyolefin resin, and the modified olefin resin of the inner layer is a modified propylene-based polyolefin resin or a modified ethylene-based polyolefin resin.
The method of claim 1, wherein the solar cell backsheet, the elongation retention rate of the following formula 1 is 50% or more, solar cell backsheet:
<Equation 1>
Elongation retention rate = A / B x 100
(Equation 1 above,
B is the elongation of the solar cell backsheet before UV irradiation on the solar cell backsheet,
A is the elongation of the solar cell back sheet after UV irradiation for 300 hours on the solar cell back sheet at 85 ° C and relative humidity of 85%).
A solar cell module comprising a solar cell and a backsheet for any one of claims 1 to 7 disposed on one side of the solar cell.

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