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Making Higher Efficiency Solar Cells With Polycrystalline Si Films

IP.com Disclosure Number: IPCOM000083809D
Original Publication Date: 1975-Jul-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Brodsky, MH: AUTHOR

Abstract

A method is proposed which will improve the photovoltaic conversion efficiency of PN junction solar cells made with polycrystalline silicon films.

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Making Higher Efficiency Solar Cells With Polycrystalline Si Films

A method is proposed which will improve the photovoltaic conversion efficiency of PN junction solar cells made with polycrystalline silicon films.

The figure illustrates schematically the present state of the art. The top and/or bottom metal contacts are semitransparent to the solar spectrum or are arranged in a noncontinuous fashion, to let light through to the active silicon layers.

Although the most efficient Si cells (about 15%) to date are single crystal devices, polycrystalline cells offer advantages in ease and cost of fabrication. However, they have the disadvantage of lower conversion efficiencies (about 1%). The lower efficiencies result from recombination of the photogenerated carriers at the grain boundaries and interfaces, before the carriers can be swept out by the electric fields in the junction region.

It has been suggested the silicon grains be oriented by preferred growth with their large dimensions aligned perpendicular to the junction plane. The method described offers an alternative or a further efficiency improvement. Hydrogen is incorporated into the silicon layers to quench the recombination mechanisms. It is known that hydrogen helps passivate Si-SiO(2) interfaces in planar integrated circuit technology. Properly incorporated, hydrogen will work to passivate the polycrystalline grain boundaries for useful polycrystalline silicon photovoltaic energy converters.

Ways of inco...