Graphene-Supported Small-Sized FeSe₂ Nanoparticles As Efficient Counter Electrode Catalysts for Dye-Sensitized Solar Cells

Designing cost-effective counter electrode (CE) catalysts for the triiodide reduction reaction (IRR) in dye-sensitized solar cells (DSSCs) is of significant importance for the development of photovoltaic technology, yet it remains a challenge. Herein, FeSe2/G composites with a well-defined intimate interface were controllably synthesized by immobilizing small-sized FeSe2 nanoparticles on graphene. As expected, the as-prepared FeSe2/G composites exhibited a remarkable photovoltaic performance of 8.69%, superior to that of FeSe2 nanoparticles (6.75%), graphene (7.11%), and traditional Pt-based devices (7.70%) as well as higher than that of most previously reported works. The theory calculation and work function results demonstrated that the accelerated kinetics process due to the optimized electronic structure around catalytic active centers further enhanced the interaction between Fe 3d orbitals and I 5p orbitals. They also demonstrated that the intrinsic catalytic activity of FeSe2 and the conductive platform properties of graphene endow the FeSe2/G composites with an impressive photovoltaic performance. The simple synthesis process and admirable performance aid in not only achieving the substitution of Pt but also establishing the structure–performance relationship to guide the synthesis of CE catalysts.