Synergistic effect of Ni and Fe in Fe-doped NiS2 counter electrode for dye-sensitized solar cells: Experimental and DFT studies

Uniform Fe-doped NiS2 octahedrons with the size of ∼250 nm have been prepared by a hydrothermal method. The as-synthesized Fe-doped NiS2 octahedrons exhibit excellent electro-catalytic activity for the reduction of triiodide to iodide in dye-sensitized solar cells (DSCs). The DSC with Fe-doped NiS2 octahedrons CE demonstrates a power conversion efficiency (PCE) of 8.01%, higher than those of NiS2 CE (6.90%) and FeS2 CE (4.13%). The enhanced efficiency is attributed to the synergistic effect between Ni and Fe ions in Fe-doped NiS2 octahedrons. Density functional theory (DFT) calculations reveal the adsorption energy of I (EI ad) increases from −0.14 eV (NiS2) to −0.65 eV (Fe-doped NiS2) after Fe doping, leading to an enhanced solar cell performance. This study indicates that the Fe-doped NiS2 octahedron is a promising substitute to develop non-Pt CEs in DSCs.