Enhancing the efficiency of CdS quantum dot-sensitized solar cells via electrolyte engineering

Quantum dot-sensitized solar cells (QDSSCs) are one kind of promising photovoltaic devices for harvesting solar energy. Previous reports have studied various photoanode materials in order to achieve a high photoelectric performance, while little attention has been paid to the electrolyte system inside the QDSSCs. In this report, a polysulfide (S^2-/S_x^2-) electrolyte system was investigated and optimized based on a CdS quantum dot/ZnO nanowire solar cell and a CdSe/CdS co-sensitized QDSSC. Water-methanol mixed solution was taken as the solvent for this polysulfide electrolyte, considering simultaneously the penetration ability and the ion dissociation of the electrolyte. Electrochemical impedance spectra (EIS) measurement was used to investigate the impedance of the electrons recombination with the electrolyte at the photoanode/electrolyte interface. With the measured efficiency of the CdS-QDSSCs, the optimal composition of the electrolyte can be obtained. The work facilitates the development of highly-efficient electrolyte in the general field of quantum dot-sensitized solar cells.