A transparent nickel selenide counter electrode for high efficient dye-sensitized solar cells

Highlights: • Ni_0.85Se was obtained by hydrothermal way and the film was gained by spin-coating. • Ni_0.85Se film has good conductivity and excellent electrocatalytic activity. • DSSC based on transparent Ni_0.85Se counter electrode obtains PCE of 8.96%. • The PCE reaches 10.76% when putting a mirror under Ni_0.85Se counter electrode. - Abstract: Nickel selenide (Ni_0.85Se) was synthesized by a facile one-step hydrothermal reaction and Ni_0.85Se film was prepared by spin-coating Ni_0.85Se ink on FTO and used as counter electrode (CE) in dye-sensitized solar cells (DSSC). The Ni_0.85Se CEs not only show high transmittance in visible range, but also possess remarkable electrocatalytic activity toward I⁻/I₃⁻. The electrocatalytic ability of Ni_0.85Se films was verified by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization curves. The DSSC using Ni_0.85Se CE exhibits a power conversion efficiency (PCE) of 8.96%, while the DSSC consisting of sputtered Pt CE only exhibits a PCE of 8.15%. When adding a mirror under Ni_0.85Se CE, the resultant DSSC exhibits a PCE of 10.76%, which exceeds that of a DSSC based on sputtered Pt CE (8.44%) by 27.49%.