High Efficiency Cadmium And Zinc Telluride Based Thin Film Solar Cells Annual Subcontract Report 1 March 1990 28 February 1991

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ISBN 13 :
Total Pages : 82 pages
Book Rating : 4.:/5 (685 download)

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Download or read book High-efficiency Cadmium and Zinc-telluride-based Thin-film Solar Cells. Annual Subcontract Report, 1 March 1990--28 February 1991 written by and published by . This book was released on 1992 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes research into polycrystalline CdTe solar cells grown by metal-organic chemical vapor deposition. Efficiencies of (approximately)10% were achieved using both p-i-n and p-n structures. A pre-heat treatment of CdS/SnO2/glass substrates at 450°C in hydrogen atmosphere prior to the CdTe growth was found to be essential for high performance because this heat treatment reduces oxygen-related defects from the CdS surface. However, this treatment also resulted in a Cd-deficient CdS surface, which may in part limit the CdTe cell efficiency to 10% due to Cd vacancy-related interface defects. Preliminary model calculations suggest that removing these states can increase the cell efficiency from 10% to 13.5%. Photon absorption in the CdS film also limits the cell performance, and eliminating this loss mechanism can result in CdTe efficiencies in excess of 18%. Polycrystalline, 1.7-e, CdZnTe films were also grown for tandem-cell applications. CdZnTe/CdS cells processed using the standard CdTe cell fabrication procedure resulted in 4.4% efficiency, high series resistance, and a band-gap shift to 1.55 eV. The formation of Zn-O at and near the CdZnTe surface is the source of high contact resistance. A saturated dichromate each prior to contact deposition was found to solve the contact resistance problem. The CdCl2 treatment was identified as the cause of the observed band-gap shift due to the preferred formation of ZnCl2. 59 refs.