Study on photo-induced charge transfer in the heterointerfaces of CuInS2/CdS co-sensitized mesoporous TiO2 photoelectrode

Abstract

CuInS2 and CdS quantum dots (QDs) are sequentially assembled onto mesoporous TiO2 film to prepare a CuInS2/CdS co-sensitized photoelectrode for QD-sensitized solar cell (QDSC) application. Our results show that the performance of a QDSC is strongly dependent on the order of CuInS2 and CdS respected to the TiO2. When CuInS2 is in between TiO2 and CdS, the power conversion efficiency could reach 0.90%, while the efficiency decreased dramatically when the CuInS2 QDs were on top of the layer (0.08%). Surface photovoltage (SPV) measurement revealed that the charge transfer from the cosensitizers toward the TiO2 is much more efficient in the TiO2/CuInS2/CdS electrode rather than in the TiO2/CdS/CuInS2 electrode. From the information on time-resolved photoluminescence (TRPL) technique, it was found that the average photoluminescence (PL) lifetime of TiO2/CuInS2/CdS electrode is shorter than that of the TiO2/CdS/CuInS2 electrode, suggesting the higher carrier transfer rates between the heterointerfaces of CuInS2/CdS and TiO2/QDs. This study reported herein propose an innovative route to investigate the role of heterointerface in the carrier transfer mechanism and enable better design of highly efficient QDSCs.