Facet-dependent activity of bismuth sulfide as low-cost counter-electrode materials for dye-sensitized solar cells

Abstract

Via density functional theory computation and experimental validation, we have compared the catalytic activities of different facets within Bi₂S₃, as counter-electrode (CE) materials for dye-sensitized solar cells (DSSCs). The (130) facet has the largest surface energy, the best electronic conductivity, and the highest position of conduction band minima, indicating the most effective electron transfer from CEs to I⁻₃ and the highest catalytic activities of Bi₂S₃ with (130) facets. To testify the computations, we also synthesized flower-like Bi₂S₃ nanostructures with dominantly exposed (130) and (211) facets, respectively, and investigated their catalytic activities through impedance spectra, I–V curves and conversion efficiency tests. DSSCs with (130) and (211) faceted Bi₂S₃ CEs exhibited conversion efficiencies of 3.5% and 1.9%, respectively, which further confirmed the superiority of (130) facets within Bi₂S₃. The findings provide some clues for designing and applying low-cost Pt-free DSSC CE materials from inorganic nanostructures.