Ni3S2/Ni–P Bilayer Coated on Polyimide as a Pt- and TCO-Free Flexible Counter Electrode for Dye-Sensitized Solar Cells

In this study, we reported an efficient, flexible, and low-cost (Pt-free and transparent conducting oxide (TCO)-free) counter electrode (CE) made of a polyimide (PI) substrate coated with a Ni3S2/Ni-P bilayer for dye-sensitized solar cells (DSCs). The bilayer Ni3S2/Ni-P hybrid film was deposited on a PI plastic substrate via a series of wet chemical/electrochemical processes. The bottom Ni-P layer was deposited on a PI to replace conventional TCO as a conductive layer, and the top Ni3S2 layer was employed as the electrocatalyst for I3(-) reduction. On the basis of the extensive electrochemical measurments, the as-prepared Ni3S2/Ni-P coated PI flexible CE demonstrated a Pt-like electrocatalytic for I3(-) reduction. As a result, the DSC assembled with the Ni3S2/Ni-P coated PI flexible CE exhibited an impressive photovoltaic conversion efficiency of 6.28% accompanied by a fill factor of 0.63 under 1 sun illumination (100 mW cm(-2), AM 1.5), which is comparative to that of the DSC based on the Pt coated indium tin oxide/polyethylene naphthalate (ITO/PEN) CE.