Solution‐Based in–situ Synthesis of Transition Metal Sulfides as Efficient Counter Electrodes for Dye‐Sensitized Solar Cells

Transition metal sulfide films Co−S, Mo−S, and Ni−S have been deposited by spin‐coating their precursor solutions followed by a mild thermal treatment. X‐ray diffraction results and X‐ray photoelectron spectrum demonstrate that the solution‐processed Co−S, Mo−S, and Ni−S are composed of CoS 2 , MoS 2 , and NiS with NiS 2 , respectively. Electrochemical characterizations reveal these sulfide films deposited on fluorine doped tin oxide (FTO) glasses as counter electrodes (CEs) show high catalytic activity to I 3 − species and good electrical conductivity compared to that of conventional Pt/FTO. Photo‐electric conversion efficiencies of 6.42 %, 5.82 %, and 5.72 % are obtained for the DSSCs adopting Co−S CE, Mo−S CE, and Ni−S CE, respectively, comparable to the device (6.59 %) employing Pt/FTO CE.