A graphene quantum dot decorated SrRuO3 mesoporous film as an efficient counter electrode for high-performance dye-sensitized solar cells

Abstract

Hydrothermally synthesized electrically conductive perovskite strontium ruthenate (SrRuO₃) nanoparticles were added into a binder solution and then cast onto fluorine doped tin oxide (FTO) glass to form a mesoporous SrRuO₃ counter electrode (CE) for dye-sensitized solar cells (DSSCs). The high porosity and large specific surface area of the SrRuO₃ CE allows easier and faster diffusion of electrolyte into the pores and involves more triiodide (I₃⁻) in the redox reaction, thereby resulting in a higher power conversion efficiency (PCE, 7.16%) than that of our published research on sputtered SrRuO₃ film CEs (6.48%). Furthermore, graphene quantum dots (GQDs) endowed with excellent intrinsic catalytic activity and high conductivity were decorated onto the SrRuO₃ CE by a dipping technique to form a SRO–GQD hybrid. The synergistic effect of SrRuO₃ and GQDs contributes to more active catalytic sites as well as faster ion diffusion and electron transfer than a pristine SrRuO₃ CE, thereby resulting in increased electrocatalytic ability towards I₃⁻ reduction. As a result, our fabricated DSSCs based on the optimized SRO–GQD CE achieve an impressive PCE of 8.05%, much higher than that of the reference device assembled with a conventional platinum (Pt) CE (7.44%). The SRO–GQD CE also exhibits an excellent long-term electrochemical stability in I₃⁻/I⁻ electrolyte. Overall, the SRO–GQD hybrid can be considered as a highly efficient Pt-free CE for practical applications of DSSCs.