LAUSR

Understanding and optimizing the effects of edge states and nanoflake dimensions on the photon harvesting efficiency in ultrathin transition-metal dichalcogenide (TMD) semiconductor photoelectrodes is critical to assessing their practical viability for solar energy conversion. We present herein a novel filtration-based separation approach to systematically vary the TMD nanoflake dimensions and edge density of solution-processed large-area multiflake WSe2 photocathodes. Photoelectrochemical measurements in both aqueous electrolyte (for water reduction) and a sacrificial redox system, together with a continuum-based charge transport model, reveal the role of the edge sites and the effects of the flake size on the light harvesting, charge transport, and recombination. A selective passivation technique using atomic layer deposition is developed to address detrimental recombination at flake edges. Edge-passivated WSe2 films prepared with the smallest flakes (∼150 nm width, 9 nm thickness) demonstrate an intern...