Electronic Device Module Comprising an Ethylene Multi-Block Copolymer

Abstract

An electronic device module comprises:A. At least one electronic device, e.g., a solar cell, andB. A polymeric material in intimate contact with at least one surface of the electronic device, the polymeric material comprising an ethylene multi-block copolymer.Typically, the polyolefin material is an ethylene multi-block copolymer with a density of less than about 0.90 grams per cubic centimeter (g / cc). The polymeric material can fully encapsulate the electronic device, or it can be laminated to one face surface of the device. Optionally, the polymeric material can further comprise a scorch inhibitor, and the copolymer can remain uncrosslinked or it can be crosslinked.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 826,319 filed Sep. 20, 2006 and U.S. Provisional Application No. 60 / 865,953 filed Nov. 15, 2006.FIELD OF THE INVENTION[0002]This invention relates to electronic device modules. In one aspect, the invention relates to electronic device modules comprising an electronic device, e.g., a solar or photovoltaic (PV) cell, and a protective polymeric material while in another aspect, the invention relates to electronic device modules in which the protective polymeric material is an ethylene multi-block copolymer. In yet another aspect, the invention relates to a method of making an electronic device module.BACKGROUND OF THE INVENTION[0003]Polymeric materials are commonly used in the manufacture of modules comprising one or more electronic devices including, but not limited to, solar cells (also known as photovoltaic cells), liquid crystal panels, electro-luminescent devices ...

AI Technical Summary

Benefits of technology

[0020]In another embodiment, the invention is the electronic device module as described in the two embodiments above except that the polymeric material in intimate contact with at least one surface of the electronic device is a co-extruded material in which at least one outer skin layer (i) does not contain peroxide for crosslinking, and (ii) is the surface which comes into intimate contact with the module. Typically, this outer skin layer exhibits good adhesion to glass. This outer skin of the co-extruded material can comprise any one of a number of different polymers, but is typically the same polymer as the polymer of the peroxide-containing layer but without the peroxide. This embodiment of the invention allows for the use of higher processing temperatures which, in turn, allows for faster production rates without unwanted gel formation in the encapsulating polymer due to extended contact with the metal surfaces of the processing equipment. In another embodiment, the extruded product comprises at least three layers in which the skin layer in contact with the electronic module is without peroxide, and the peroxide-containing layer is a core layer.

[0029]In another variant on these method embodiments, the electronic device is encapsulated, i.e., fully engulfed or enclosed, within the polymeric material. In another variant on these embodiments, the cover layer is treated with a silane coupling agent, e.g., γ-amino propyl tri-ethoxy silane. In yet another variant on these embodiments, the polymeric material further comprises a graft polymer to enhance its adhesive property relative to the one or both of the electronic device and cover layer. Typically the graft polymer is made in situ simply by grafting the ethylene multi-block copolymer with an unsaturated organic compound that contains a carbonyl group, e.g., maleic anhydride.

Problems solved by technology

No one polymeric material delivers maximum performance on all of these properties in any particular application, and usually trade-offs are made to maximize the performance of properties most important to a particular application, e.g., transparency and protection against the environment, at the expense of properties secondary in importance to the application, e.g., cure time and cost.

EVA resins are typically stabilized with ultra-violet (UV) light additives, and they are typically crosslinked during the solar cell lamination process using peroxides to improve heat and creep resistance to a temperature between about 80 and 90 C. However, EVA resins are less than ideal PV cell encapsulating film material for several reasons.

This discoloration can result in a greater than 30% loss in power output of the solar module after as little as four years of exposure to the environment.

EVA resins also absorb moisture and are subject to decomposition.

One of the most fundamental limitations on the efficiency of a solar cell is the band gap of its semi-conducting material, i.e., the energy required to boost an electron from the bound valence band into the mobile conduction band.

Photons with energy higher than the band gap are absorbed, but their excess energy is wasted (dissipated as heat).

Crosslinking, particularly chemical crosslinking, while addressing one problem, e.g., thermal creep, can create other problems.

While this addresses the thermal creep problem, it creates a corrosion problem, i.e., total crosslinking is seldom, if ever, fully achieved and this leaves residual peroxide in the EVA.

Another potential problem with peroxide-initiated crosslinking is the buildup of crosslinked material on the metal surfaces of the process equipment.

Over longer periods of extrusion time, crosslinked material can form at the metal surfaces and require cleaning of the equipment.

The current practice to minimize gel formation, i.e., this crosslinking of polymer on the metal surfaces of the processing equipment, is to use low processing temperatures which, in turn, reduces the production rate of the extruded product.

This thermoplasticity, however, must not be obtained at the expense of effective thermal creep resistance.

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