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International Journal of Photoenergy
Volume 2015, Article ID 583058, 8 pages
http://dx.doi.org/10.1155/2015/583058
Research Article

Effects of CdS Buffer Layers on Photoluminescence Properties of Cu2ZnSnS4 Solar Cells

1Department of Materials Science and Milano-Bicocca Solar Energy Research Center (MIB-SOLAR), University of Milano-Bicocca, Via Cozzi 55, 20125 Milan, Italy
2RSE S.p.A., Via R. Rubattino 54, 20134 Milan, Italy

Received 17 December 2014; Revised 16 February 2015; Accepted 19 February 2015

Academic Editor: Yanfa Yan

Copyright © 2015 A. Le Donne et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Cu2ZnSnS4 (CZTS) absorber layers grown by sputtering were investigated by photoluminescence before and after the chemical bath deposition of CdS in order to evaluate the possible passivation of point defects by Cd atoms at the absorber/buffer layer interface. According to the literature, a broad emission around 1.21 eV was observed at low temperature under above bandgap excitation of the as-grown CZTS samples. Broad bands at 1.075 eV and 0.85 eV were detected for the first time under below bandgap excitation of the as-grown CZTS samples at low temperature, which were explained in terms of radiative transitions involving point defect-related levels determined in the literature by first-principles calculations. The emissions observed in the as-grown samples were monitored by both above and below bandgap excitations also in standard CZTS solar cells produced on the same layers. The obtained results suggest that, as in the case of Cu(In, Ga)Se2, Cd atoms passivate point defects at the absorber/buffer layer interface also in CZTS.