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Title:Single crystal and polycrystalline copper indium selenide deposited by the hybrid sputtering and evaporation method for photovoltaic devices
Author(s):Yang, Li-Chung
Doctoral Committee Chair(s):Rockett, Angus A.
Department / Program:Materials Science and Engineering
Discipline:Materials Science and Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Electronics and Electrical
Engineering, Materials Science
Abstract:The results presented here impact the CuInSe$\sb2$ solar cells community in three areas: (1) fundamental understanding of CuInSe$\sb2$ growth and properties, (2) development and optimization of a potentially scalable deposition technique, and (3) improvement in solar cell performance based on a novel adhesion-promoting back contact layer. Each of these impacts on the general problem of irreproducibility in production of high-performance CuInSe$\sb2$ solar cells.
The work presented in this thesis has shown that second phase separation is more rapid and film uniformity is greater at high deposition temperatures than at low temperatures in polycrystalline layers deposited by physical vapor deposition processes. Furthermore, the preferred orientation of common polycrystalline CuInSe$\sb2$ has been shown to result from minimization of the surface free energy rather than the substrate orientation. The combined results indicate that air heat treatment which is critical to optimized performance in most physical-vapor-deposited CuInSe$\sb2$ is probably due to passivation of high energy surfaces. The resistivity data collected from single crystals explains the preference for In-rich CuInSe$\sb2$ for devices and the implications of segregated layers at grain boundaries on device performances.
The composition of device layers not only affects their performance directly, but also was found in the process being used in this thesis to affect performance indirectly through adhesion failures. A novel contact design was demonstrated, including a unique metastable-phase precipitation, for improved adhesion. The rate limited supply of Cu precipitating from the substrate, dissolves in the CuInSe$\sb2$ layer modifying the chemistry at the back of the CuInSe$\sb2$ and improving the adhesion.
The integrated understanding resulting from the results presented here allowed the deposition process, back contact, and device fabrication to be optimized. This resulted in a 3% increase in the best performance and dramatic improvement in performance uniformity of solar cells incorporating on CuInSe$\sb2$ produced by the hybrid process.
Issue Date:1994
Rights Information:Copyright 1994 Yang, Li-Chung
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI9503359
OCLC Identifier:(UMI)AAI9503359

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