University of Illinois Urbana-Champaign

Spectroscopic ellipsometry and dielectric modeling of thin film CdTe/CdS photovoltaic devices

Darrow, Michael Cole

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DARROW-THESIS-2017.pdf

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https://hdl.handle.net/2142/97503

Description

Title
Spectroscopic ellipsometry and dielectric modeling of thin film CdTe/CdS photovoltaic devices
Author(s)
Darrow, Michael Cole
Issue Date
2017-04-28
Director of Research (if dissertation) or Advisor (if thesis)
Rockett, Angus A.
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Date of Ingest
2017-08-10T19:16:18Z
Keyword(s)
  • Ellipsometry
  • Cadmium telluride (CdTe)
  • Dielectric modeling
  • Photovoltaics
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.
Graduation Semester
2017-05
Type of Resource
text
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http://hdl.handle.net/2142/97503
Copyright and License Information
Copyright 2017 Michael Darrow

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