Photoluminescence study and observation of unusual optical transitions in Cu2ZnSnSe4/CdS/ZnO solar cells

Abstract

In this paper, we examine photoluminescence spectra (PL) of Cu2ZnSnSe4/CdS/ZnO solar cells, based on an absorber layer fabricated by selenization of sputtered Cu, Zn, Sn multilayers, via temperature-dependent and illumination power-dependent measurements. We observe anomalous emission behavior: the PL peak initially decreases with increasing temperature (red shift) in the temperature range 10-60 K, followed by a blue shift at higher temperature in the range 60-180 K. A recombination model is proposed that is able to explain both temperature dependent PL as well as power-dependent PL The important aspect of the proposed model is taking into account the presence of strong potential fluctuations in the absorber layer, which can also contribute to the low V-oc values generally observed in Cu2ZnSnSe4, based solar cells. (C) 2014 Elsevier B.V. All rights reserved.