One-step hydrothermal synthesis of In2.77S4 nanoparticles doped graphene oxide hybrids as efficient counter electrodes in dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have become a potential alternative to photovoltaic devices, which can convert solar energy into electrical energy. As an essential component of DSSCs, counter electrode (CE) materials play an important role in determining the performance of DSSCs. Thus, research should seek for a cost-effective and high-activity CE materials. In this work, we explored an efficient, low-cost (platinum (Pt)-free) CE made of hybrids of In_2.77S₄ nanoparticles and reduced graphene oxide (RGO) for DSSCs. In_2.77S₄-RGO hybrids were facilely synthesized via a one-step hydrothermal approach without template or complicated precursor. Especially during synthesis, glacial acetic acid was added to prevent the precipitation of In³⁺ ions. Thus, free In³⁺ and S²⁻ ions can readily absorb onto the graphene oxide (GO) surface by electrostatic forces. Finally, In_2.77S₄ nanoparticle-doped GO hybrids were obtained under hydrothermal conditions. Based on electrochemical measurement in cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization curve tests, the as-prepared mesoporous In_2.77S₄-RGO hybrids exhibited remarkable electrocatalytic properties, charge–transfer capabilities, and electrochemical stabilities. As a result, the DSSCs assembled with In_2.77S₄-RGO hybrid CE exhibited a powder conversion efficiency of 6.72%, which is superior to that with Pt CE (6.30%). These findings suggest that In_2.77S₄-RGO hybrids can be used as a promising alternative CE in DSSCs.