Influence of highly efficient PbS counter electrode on photovoltaic performance of CdSe quantum dots-sensitized solar cells

PbS electrode with high catalytic activity to S_n ^2? reduction certificated by the measurements of electrochemical impedance spectroscopy and cyclic voltammetry was prepared by a simple method. The high catalytic activity makes it be a low-cost alternative counter electrode to platinum (Pt) to be used in quantum dots-sensitized solar cells (QDSSCs) based on polysulfide electrolyte. The photovoltaic performance enhancement of the quantum dots (QDs)-sensitized semiconductor thin films due to the PbS counter electrode was evaluated by fabricating QDSSCs based on CdSe QDs-sensitized ZnO (SnO₂) thin film. CdSe QDs-sensitized ZnO thin film has the lower internal total series resistance and electron transmission time, the higher electron lifetime and electron collection efficiency than the CdSe QDs-sensitized SnO₂ thin film. Replacing the Pt counter electrode with the PbS counter electrode leads to more improvement on the short circuit photocurrent density for QDSSC based on the ZnO thin film than the SnO₂ thin film. Therefore, the process to limit the photovoltaic performance of CdSe QDs-sensitized solar cell and the possible way to improve the photovoltaic performance were analyzed.