In situ direct growth of single crystalline metal (Co, Ni) selenium nanosheets on metal fibers as counter electrodes toward low-cost, high-performance fiber-shaped dye-sensitized solar cells

Abstract

Highly crystalline metal (Co, Ni) selenium (Co_0.85Se or Ni_0.85Se) nanosheets were in situ grown on metal (Co, Ni) fibers (M–M_0.85Se). Both M–M_0.85Se (Co–Co_0.85Se and Ni–Ni_0.85Se) fibers prove to function as excellent, low-cost counter electrodes (CEs) in fiber-shaped dye-sensitized solar cells (FDSSCs) with high power conversion efficiency (Co–Co_0.85Se 6.55% and Ni–Ni_0.85Se 7.07%), comparable or even superior to a Pt fiber CE (6.54%). The good performance of the present Pt-free CE-based solar cell was believed to originate from: (1) the intrinsic electrocatalytic properties of the single-crystalline M–M_0.85Se; (2) the enough void space among M_0.85Se nanosheets that allows easier redox ion diffusion; (3) the two-dimensional morphology that provides a large contact area between the CE catalytic material and electrolyte; (4) in situ direct growth of the M_0.85Se on metal fibers that renders good electrical contact between the active material and the electron collector.