Cobalt-nickel based ternary selenides as high-efficiency counter electrode materials for dye-sensitized solar cells

One important challenge in dye-sensitized solar cells (DSSCs) is to design and construct low-cost counter electrodes (CEs) with good electrocatalytic performance. In this work, a one-step solvothermal method was used to prepare cobalt-nickel (Co-Ni) based ternary selenides with different Co and Ni ratios. Co-Ni based ternary selenide films were fabricated by simple spray deposition for applications as low-cost and high-performance CEs in DSSCs. Electrochemical measurements demonstrate that the Co-Ni based ternary selenide CEs exhibit high electrocatalytic activity and strong charge-transfer ability for the reduction of I₃ ⁻ due to the synergistic effect between Co and Ni ions in Co-Ni based ternary selenides. In particular, Co_0.42Ni_0.58Se CE shows the higher electrocatalytic activity than other Co-Ni based ternary selenide CEs and platinum (Pt) CE. Furthermore, the DSSC with Co_0.42Ni_0.58Se CE exhibits photoelectrical conversion efficiency (PCE) of 6.15%, which is considerably higher than that of the DSSC with Pt CE (5.53%).