Improving the electrocatalytic activity and stability of spinel sulfide counter electrodes by trimetallic synergy effects for quantum dot sensitized solar cells

Abstract

Spinel trimetallic sulfide M_0.5Ni_0.5Co₂S₄ (M = Cu and Mn) nanostructures are designed and synthesized for the first time via a facile one-pot solvothermal strategy and used as efficient counter electrodes (CEs) for quantum dot sensitized solar cells (QDSSCs). Electrochemical tests show that the interface charge transfer resistance (R_ct) of Cu_0.5Ni_0.5Co₂S₄ is only 0.79 Ω, which is less than half of the R_ct of NiCo₂S₄ (2.04 Ω). The best power conversion efficiency of QDSSCs assembled with the TiO₂/CdS/CdSe/ZnS photoanode and Ti-mesh substrate Cu_0.5Ni_0.5Co₂S₄ CE reaches 5.20%. The superior electrocatalytic activity toward S_n²⁻ reduction is attributed to the synergy effects of multiple transition metal heteroatoms, and the outstanding stability may stem from the distorted structures of spinel trimetallic sulfides. This work exhibits the potential of spinel trimetallic sulfides to be competitive CE material candidates for efficient QDSSCs.