Bi2S3microspheres grown on graphene sheets as low-cost counter-electrode materials for dye-sensitized solar cells

Abstract

In this work, we synthesized 3D Bi₂S₃ microspheres comprised of nanorods grown along the (211) facet on graphene sheets by a solvothermal route, and investigated its catalytic activities through I–V curves and conversion efficiency tests as the CE in DSSCs. Although the (211) facet has a large band gap for a Bi₂S₃ semiconductor, owing to the introduction of graphene into the system, its short-circuit current density, open-circuit voltage, fill factor, and efficiency were J_sc = 12.2 mA cm⁻², V_oc = 0.75 V, FF = 0.60, and η = 5.5%, respectively. By integrating it with graphene sheets, our material achieved the conversion efficiency of 5.5%, which is almost triple the best conversion efficiency value of the DSSCs with (211)-faceted 3D Bi₂S₃ without graphene (1.9%) reported in the latest literature. Since this conversion-efficient 3D material grown on the graphene sheets significantly improves its catalytic properties, it paves the way for designing and applying low-cost Pt-free CE materials in DSSC from inorganic nanostructures.