CdS quantum dots sensitized single-crystalline TiO₂ nanowire array films: photovoltaic performance and photoelectron transport properties

摘要

Single-crystalline rutile TiO2 nanowires were synthesized in situ on transparent conductiveoxide (TCO) glass substrate and CdS quantum dots (QDs) were deposited on nanowires toform a TiO2/CdS heterojunction structure. The orientation growth, single-crystallinestructure of TiO2 nanowire and the core-shell structure of TiO2/CdS were confirmed byXRD, SAED and HR-TEM measurements. The QD sensitized solar cells (QD-SSCs) wereassembled and the optical, photoelectrical properties of QD-SSCs were investigated. Theresults showed that CdS QDs enhanced the optical absorbance of TiO2 in the visible region,therefore greatly improved the photovoltaic performance of solar cells. Under optimumparameters, a power conversion efficiency of 1.72% was achieved. Electron impedancespectroscopy measurement was also carried out to investigate the kinetics of chargetransfer and recombination in QD-SSCs. The effects of amount of QDs and photoelectrontransport properties of QD-SSCs on the cell efficiency were analyzed. It was proved thatthe amount of QDs was more important factor than electron lifetime and transfer rate forcell efficiency when the coverage of QDs on TiO2 was not high enough.