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Title:Spectroscopic ellipsometry and dielectric modeling of thin film CdTe/CdS photovoltaic devices
Author(s):Darrow, Michael Cole
Advisor(s):Rockett, Angus A
Department / Program:Materials Science and Engineering
Discipline:Materials Science and Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Cadmium telluride (CdTe)
Dielectric modeling
Abstract:Spectroscopic ellipsometry (SE) is a non-contact, non-destructive characterization technique for probing the optical properties of thin films. With the advent of second-generation solar cells, SE has seen use as a method for determining the dielectric function of each layer in heterostructured, thin-film photovoltaic devices. The aim of this thesis is to assess the capability of SE to resolve changes associated with illumination in the dielectric function of the absorbing layer of CdTe/CdS photovoltaic devices. Subsequently, this thesis aims to model the dielectric function of CdTe using critical point parabolic band theory (CPPB) and map the observed modulation to changes in the band structure associated with the photoexcitation of carriers. SE successfully measured the absolute geometry and optical properties of the solar cell, with the parameterization of the absorbing layer corroborating previous research. Small, qualitatively reproducible changes in the raw SE spectra were observed when the device was subject to illumination. Nevertheless, the associated modulation of the dielectric function was too small in comparison to the uncertainty to be of scientific use. Although SE proved unable to resolve the desired modulation, improvements in experimental methodology may allow for greater success in future work.
Issue Date:2017-04-28
Rights Information:Copyright 2017 Michael Darrow
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05

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