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Effect of O2 on thickness uniformity of CdTe thin film deposited using CSS

Published online by Cambridge University Press:  31 January 2011

Nirav D Vora  and
Ramesh Dhere
Nirav D Vora
Affiliation:
nirav.vora@nrel.gov, National Renewable Energy Laboratory, 1617 Cole Blvd, Mailstop 3219, Golden, Colorado, 80401, United States, 303-384-7837
Ramesh Dhere
Affiliation:
ramesh.dhere@nrel.gov, National Renewable energy laboratory, National Center for Phoovoltaics, Golden, Colorado, United States
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Abstract

Incorporating O2 in the closed space sublimation (CSS) of CdTe thin film has resulted in improved cell efficiencies. Many studies have been undertaken to understand this effect on cell efficiency. In this work we study the effect of oxygen on lateral uniformity of the deposited CdTe film. A finite element model has been developed to represent the mass and heat transfers involved in the CSS process. The model takes into consideration the effect of O2 by modeling its reaction with Cd vapors in the space between the source and the substrates and with the CdTe source. So a gradient of O2 from the edges to the center of the substrate can result in non-uniform oxidation of the source and subsequently a laterally non-uniform film. A steady state model solved at various temperatures, pressures, and separation distances. O2 concentration gradient was found to depend on the oxidation rate of Cd vapors and thus on temperature, total pressure, and oxygen partial pressure in the system.

Keywords

Cdkineticsoxidation
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1210: Symposium Q – Photovoltaic Materials and Manufacturing Issues II , 2009 , 1210-Q02-03
Copyright
Copyright © Materials Research Society 2010

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