Selenylation to charge transfer improvement at the counter electrode (CE)/electrolyte interface for nanocrystalline Cu1.8S1−xSex CEs

Abstract

Pt counter electrodes (CEs) have been widely used in dye-sensitized solar cells (DSSCs) due to their high conductivity and electrocatalytic activity. However, industrialization of DSSCs is limited by shortcomings of Pt CEs such as being expensive, and weak corrosion resistance in electrolytes. Reported in this paper is two simple approaches to Pt-free Cu_1.8S_1−xSe_x CEs. Nanocrystalline Cu_1.8S_1−xSe_x CEs were fabricated via two processes, that is, a solvothermal process to Cu_1.8S_1−xSe_x powder followed by CE fabrication, and a solvothermal process and CE fabrication to Cu_1.8S films followed by selenylation to Cu_1.8S_1−xSe_x CEs. Photoelectric conversion efficiencies (PCE) of 4.02% and 4.16% were achieved respectively by the as-fabricated Cu_1.8S_1−xSe_x CEs. Compared with the cells with Cu_1.8S CEs fabricated by the same processes, increases of 19% and 45% were achieved, respectively. The PCE improvement comes from the enhancement of charge transfer at the CE/electrolyte interface induced by the selenylation of the CEs.