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The Mechanism of J-V “Roll-Over” in CdS/CdTe Devices

Published online by Cambridge University Press:  01 February 2011

Jie Zhou
Affiliation:
Jie_zhou@nrel.gov, National Renewabel Energy Lab, Electronic Materials and Device Division, 1617 Cole Blvd, Golden, CO, 80401, United States
Xuanzhi Wu
Affiliation:
xuanzhi_wu@nrel.gov, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80401, United States
Yanfa Yan
Affiliation:
yanfa_yan@nrel.gov, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80401, United States
Sally Asher
Affiliation:
sally_asher@nrel.gov, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80401, United States
Juarez Da Silva
Affiliation:
juarez_DaSilva@nrel.gov, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80401, United States
Suhuai Wei
Affiliation:
suhuai_wei@nrel.gov, National Renewable Energy Lab, 1617 Cole Blvd, Golden, CO, 80401, United States
Lothar Weinhardt
Affiliation:
weinhard@unlv.nevada.edu, University of Nevada, Las Vegas, Department of Chemistry, Las Vegas, NV, 89154, United States
Marcus Bar
Affiliation:
baerm2@unlv.nevada.edu, University of Nevada, Las Vegas, Department of Chemistry, Las Vegas, NV, 89154, United States
Clemens Heske
Affiliation:
heske@unlv.nevada.edu, University of Nevada, Las Vegas, Department of Chemistry, Las Vegas, NV, 89154, United States
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Abstract

The “roll-over” phenomenon in current-voltage (J-V) curves of CdS/CdTe devices is recognized as a result of the formation of a higher back barrier. When Cu has not been intentionally added to the back contact, roll-over is understandable. However, the mechanism was unclear for forming J-V roll-over in a CdTe cell with a back contact containing Cu. We did extensive characterizations, including XRD, XPS, SIMS, TEM, and EDS, and “recontact” experiments to understand this phenomenon. The results show that the roll-over comes from the formation of Cu-related oxides at the back side of the device during processing, rather than the diffusion of Cu to the front side of the device. Discussions related to the J-V roll-over mechanisms will also be presented.

Type
Research Article
Copyright
Copyright © Materials Research Society 2007

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