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All-CSS processing of CdS/CdTe thin-film solar cells with thin CdS layers

Published online by Cambridge University Press:  01 February 2011

Alan Davies ,
J. R. Sites ,
R. A. Enzenroth ,
W. S. Sampath  and
K. L. Barth
Alan Davies
Affiliation:
daviesar@lamar.colostate.edu, Colorado State University, Physics, 1875 Campus Delivery, Fort Collins, CO, 80523, United States
J. R. Sites
Affiliation:
sites@lamar.colostate.edu, Colorado State University, Physics, 1875 Campus Delivery, Fort Collins, CO, 80523, United States
R. A. Enzenroth
Affiliation:
alenz@engr.colostate.edu, Colorado State University, Mechanical Engineering, Fort Collins, CO, 80523, United States
W. S. Sampath
Affiliation:
sampath@engr.colostate.edu, Colorado State University, Mechanical Engineering, Fort Collins, CO, 80523, United States
K. L. Barth
Affiliation:
barth@engr.colostate.edu, Colorado State University, Mechanical Engineering, Fort Collins, CO, 80523, United States
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Abstract

Cadmium Sulfide/Cadmium Telluride (CdS/CdTe) thin-film solar cells were fabricated by an in-line, close-space-sublimation (CSS) process at Colorado State University. Source temperature control was used to reduce the deposited CdS thickness. Quantum efficiency (QE) showed CdS thicknesses that varied over a range from 250 to 10 nm. Current-Voltage (J-V) measurements showed increased Jsc as CdS was thinned. Thin CdS resulted in reduced voltage (800 mV to 350 mV) and fill factor, which offset gains in current, and caused efficiencies to drop from 12.6% for thick CdS layers to 4.5% for devices with the thinnest CdS. These performance trends are consistent with calculations assuming parallel junctions of CdS/CdTe and SnO2/CdTe. Localized weak-junction formation was characterized by high-resolution laser-beam-induced current (LBIC) mapping. Greater incidence of spatial non-uniformities in photocurrent response accompanied thinning of the CdS layer, with 638-nm spectral response varying spatially by 4.5% for thin CdS devices compared to variations less than 1% for devices with thicker CdS. Non-uniformities of cells with thin CdS are highly sensitive to voltage bias and are likely indicative of parallel p-n and Schottky-type junctions.

Keywords

II-VIphotovoltaicCd
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1012: Symposium Y – Thin-Film Compound Semiconductor Photovoltaics-2007 , 2007 , 1012-Y03-23
Copyright
Copyright © Materials Research Society 2007

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