Photo‐enhanced catalytic activity of spray‐coated Cu₂SnSe₃ nanoparticle counter electrode for dye‐sensitised solar cells

Abstract

Cu2SnSe3 nanoparticles are synthesised using oleylamine as both a solvent and capping agent and spray coated to form dye‐sensitised solar cell (DSSC) counter electrodes (CEs) using earth‐abundant elements. The film requires annealing at only 400 °C in nitrogen, which is a lower temperature than previous reports of both Cu2SnSe3and Cu2ZnSnSe4 films, also avoiding the use of Se gas. The composition and phase of the material is confirmed to be kesterite Cu2SnSe3. DSSCs using Cu2SnSe3 CEs give a power conversion efficiency of 4.87%, compared to 5.35% when using Pt. Electrochemical impedance spectroscopy indicates that the performance of the Cu2SnSe3 CE is enhanced under illumination, leading to a drop in the charge transfer resistance. This illumination‐induced enhancement of the catalytic activity provides a novel mechanism for the enhancement of CE performance in DSSCs. Photo‐excitation of the nanostructured Cu2SnSe3 counter electrode provides a higher overpotential for electrolyte reduction, giving improved catalytic performance.