Towards single molecule interfacial charge transfer dynamics in a dye-sensitized solar cell model

摘要

Using confocal fluorescence microscopy under ultrahigh vacuum conditions, we investigate the heterogeneousinteractions between a perylene bisimide fluorophore and single crystalline Al203 (0001) at the single molecule level.We find that the dye molecules undergo reversible transitions to long-lived dark states, with bright and dark periodslasting from several hundred milliseconds to many tens of seconds. These periods are power-law distributed and pointtowards charge tunneling processes from the molecule to the substrate. The fluorescence intensity levels show a bimodaldistribution, indicating different classes of adsorption sites on the sapphire surface. This study is aimed at obtaining abetter understanding of interfacial structure and dynamics in order to address ultimately both the growth of organicsemiconductor films on inorganic surfaces and the heterogeneous nature of charge transfer in excitonic solar cells.