Analyzing the Efficiency of Dye Sensitized Solar Cells Using Single Molecule Spectroscopy

Dye sensitized solar cells (DSSCs) have shown great potential for clean, efficient, and inexpensive solar energy technology. DSSCs produce electricity by electron transfer between a dye and semiconductor. Unfortunately, the complex electron transfer mechanisms of are hypothesized to be a major cause in inefficiency. To model a typical DSSC structure, blinking is used to probe electron transfer between a dye molecule and a semiconductor. Blinking, a phenomenon observed in dye molecules upon photoexcitiation, is transitional jumps between quantum states that can be seen as emissive and non emissive events. We examine the blinking behaviors of two flourophores Rhodamine B(RB) and Rhodamine 6 G(R6G) using single molecule spectroscopy (SMS). These experiments allow for statistical analysis of electron transfer events, giving insight into the underlying photophysics of the dyes. Inconsistent with past studies, power law distributions showed to be insufficient for describing much of the observed blinking behaviors. Instead, lognormal distributions characterize non-emissive events, corresponding to the transition from a dark state to the molecular ground state. Lognormal dispersive kinetics describe a distribution of activation barriers which physical origins are yet to be explored.