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Study of the Electronic Properties of Matched Na-Containing and Reduced-Na CuInGaSe2 Samples Using Junction Capacitance Methods

Published online by Cambridge University Press:  01 February 2011

Peter T Erslev ,
Adam Halverson ,
William Shafarman  and
J. David Cohen
Peter T Erslev
Affiliation:
perslev@darkwing.uoregon.edu, ., ., ., ., OR, ., United States
Adam Halverson
Affiliation:
ahalvers@uoregon.edu, University of Oregon, Physics Department, Eugene, OR, 97405, United States
William Shafarman
Affiliation:
wns@udel.edu, Institute of Energy Conversion, Newark, DE, 19716, United States
J. David Cohen
Affiliation:
dcohen@uoregon.edu, University of Oregon, Physics Department, Eugene, OR, 97405, United States
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Abstract

Junction capacitance methods were used to examine a matched pair of CuInGaSe2 (CIGS) thin film solar cells, one with Na incorporated into the absorber and the other with a diffusion barrier to inhibit the Na incorporation from the soda-lime glass. Typical cells showed a 50% increase in efficiency with the addition of Na. Forward biased admittance spectroscopy revealed a large defect density located near the CdS/CIGS heterojunction in the reduced Na samples not present in the higher Na samples. This may be responsible for the lower Voc, contributing to the loss in efficiency when Na is not added. Drive-level capacitance profiles revealed free carrier densities of 3×1014cm-3 and 1.1×1014cm-3 for the higher and reduced Na samples, respectively. Transient photocapacitance spectra indicated a slight improvement in absorber properties with the addition of Na, but not enough to account for the large loss in efficiency.

Keywords

photovoltaicNapassivation
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1012: Symposium Y – Thin-Film Compound Semiconductor Photovoltaics-2007 , 2007 , 1012-Y12-30
Copyright
Copyright © Materials Research Society 2007

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