Testing New Concepts in Solar Cells Sensitized with Indoline DyesAlkoxysilyl Anchoring Group, Molecular Capping, and Cobalt-Based Electrolyte

Basic photovoltaic parameters of the cells sensitized with a popular indoline D149 dye, containing the carboxyl anchoring group, were compared with those of the cells sensitized with the dye modified by the addition of the alkoxysilyl anchoring moiety. Desorption measurements of both compounds showed that the time constant of this process was longer for the modified dye. Two types of electrolytes were used, and the long-time stability and open-circuit voltage were significantly improved when the iodide electrolyte was replaced by the cobalt–bipyridine one. The dynamics of electron injection and titania–electrolyte recombination processes that occur in different time scales, from femtoseconds to seconds, were monitored by femtosecond transient absorption and electrochemical impedance spectroscopy. Additionally, the effect of molecular passivation by post-sensitization capping was checked. The cells after molecular capping showed better relative photocurrent and longer lifetime of the excited state, which was explained as resulting from the suppressed self-quenching of the dyes