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.