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Determination of Composition and Phase Depth-Profiles in Multilayer and Gradient Solid Solution Photovoltaic Films Using Grazing Incidence X-ray Diffraction

Published online by Cambridge University Press:  06 March 2019

B. L. Ballard
Affiliation:
University of Denver, Engineering Department, DenverColorado 80208
X. Zhu
Affiliation:
University of Denver, Engineering Department, DenverColorado 80208
P. K. Predecki
Affiliation:
University of Denver, Engineering Department, DenverColorado 80208
D. Albin
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
A. Gabor
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
J. Turtle
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
R. Noufi
Affiliation:
National Renewable Energy Laboratory, Golden, CO 80401
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Abstract

A method for using grazing incidence x-ray diffraction (GIXD) for profiling composition changes with depth of photovoltaic quality thin films is presented. The average thickness of the first layer in a multi-layer film of CuIn2Se3.5/CuInSe2/Mo and the variation in solid solution composition of a Cu(In1-xGax)Se2 (CIGS) film with depth are solved using this method. The phase volume fraction and the phase composition profiles are developed from peak intensity and d-spacing measurements respectively at a series of fixed incident angles corresponding to a set of increasing 1/e penetration depths, τ. Inverse Laplace and numerical methods are applied to the τ profiles converting them to true depth profiles. Vegard's law is applied to the d-spacing vs z-profile to obtain x in the formula Cu(In1-xGax)Se2. The results show that an ∼1 μm thick layer of CuIn2Se3.5 is present on the surface of the multi-layer film and that the CIGS film consists of a Ga rich surface layer ∼2000 Å thick followed by a gradual decrease in Ga content with increasing depth. This gradient appears to be desirable for producing photovoltaic quality CIGS films.

Type
III. Applications of Diffraction to Semiconductors and Films
Copyright
Copyright © International Centre for Diffraction Data 1994

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