High-Entropy Metal Sulfides (CdCuCoMnZn)S_x as High-Performance Counter Electrode for Quantum Dot-Sensitized Solar Cells

The photovoltaic performance parameters of QDSSCs fabricated using low-entropy metal sulfide and medium-entropy metal sulfide catalysts as counter electrodes (CEs) are not satisfactory, thus further limiting the industrial application of QDSSCs. Considering the excellent mechanical, catalytic, and conductive performance due to the synergistic effect of high-entropy metal sulfide can effectively deal with the above issues, hence, the (CdCuCoMnZn)S x catalyst as CE was prepared by a simple solvothermal method and successfully applied in the field of QDSSCs. Various characterization methods show that the (CdCuCoMnZn)S x catalyst presents a nanoparticle structure with a larger specific surface area, which provides more active sites, facilitates electron transfer, promotes catalytic performance, and ultimately accelerates the reduction reaction between the CE and the polysulfide electrolyte interface. Additionally, electrochemical tests indicate that the (CdCuCoMnZn)S x catalyst has much lower charge transfer resistance, diffusion resistance, and series resistance. This suggests that this high-entropy metal sulfide has good electron transfer characteristics and electrocatalytic activity, which is likewise conducive to the reduction reaction. Eventually, the (CdCuCoMnZn)S x catalyst as a CE displays outstanding photovoltaic performance parameters including J sc = 25.60 mA·cm –2, V oc = 0.665 V, FF = 0.49, and PCE = 8.33%, all of which are conspicuously superior to CuS and (CuCo)S x catalysts. The above results provide the method and theoretical foundation for similar research, especially the application of high-entropy metal sulfides in the field of QDSSCs.