Characterization of tellurium back contact layer for CdTe thin film devices
Date
2018
Authors
Moffett, Christina, author
Sampath, W. S., advisor
Sites, James, committee member
Popat, Ketul, committee member
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Abstract
Cadmium Telluride (CdTe) thin film photovoltaic technology has shown favorable progress due to inexpensive and efficient processing techniques. However, efficiencies have yet to reach the overall projected CdTe device efficiency, with the back contact being a main source of CdTe performance limitations. Tellurium (Te) applied as a back contact has led to significant increases in fill factor and an overall progress in device efficiency. Devices deposited with Te show significant improvement in uniformity, even without intentional Cu doping, when compared to devices without Te. In current - density measurements, Te shows stability even at low temperatures, which is indicative of a low barrier developed at the CdTe/Te interface. X-ray and ultra-violet photoelectron spectroscopy were carried out to examine the valence band offset at the CdTe/Te back contact interface. The valence band offset was shown to be highly dependent on the Te thickness and was largely affected by oxidation and contamination at the surface. Capacitance measurements were carried out to study the effect Te has on the absorber depletion width. Data indicate a decreased depletion width with Te applied at the back of thin film CdTe devices, which agrees with increased device performance. Te thickness was varied in all studies to understand the effect of application thickness on device performance and material characteristics. With a thicker Te layer leading to overall improvement in device performance and favorable device characteristics.
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Subject
back contact interface
photovoltaics
thin film
cadmium telluride
back contact
tellurium