CdS quantum dots pre-deposition for efficiency enhancement of quantum dot-sensitized solar cells

Abstract

Here we report a general study on the effect of various semiconductor sensitizers i.e. CdS, CdSe, CdS/CdSe, and PbS/CdS on the performance of quantum dot sensitized solar cells (QDSCs). The electron life time in the cells is investigated by applied bias voltage decay method. We clearly indicate that the electron life time could be considerably enhanced by CdS pre-deposition in CdS/CdSe QD sensitized cells.The charge transfer properties of cells are investigated by impedance spectroscopy and it is shown that a clear downward shift in TiO2 conduction band take place through CdS QDs sensitizer pre-deposition. According to the results, type and the sequence of QDs deposition has a clear effect on the recombination resistance in cells. Here the efficiency of solar cells was improved to 3.63% by CdS pre-deposition which is more than 25% improvement in comparison to CdSe sensitized cells (2.84%). This general study indicates that tuning the sensitizer type can be systematically used in QDSCs to increase the electron life time and consequently the cells’ performance in a simple and cost effective way.