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

Abstract

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.