Interfacial modification of the photoanode|electrolyte interface using oleic acid (OA) is thoroughly investigated in this present study. The overall photoconversion efficiency of 11.8% was achieved under the illumination of 100 mW cm-2 with an optical filter of AM 1.5 G. OA molecules were meant to be adsorbed on to the vacant areas of the TiO2 and the OA moieties leached out the aggregated C106 dye molecules from the TiO2 surface. There was a strong spectral overlap between the absorption spectrum of donor (OA) and the emission spectrum of acceptor (C106), leading to effective Förster Resonance Energy Transfer (FRET) between OA and C106 and suggested an excellent opportunity to improve the photovoltaic performances of DSSCs. UV-vis DRS and UPS analysis revealed that OA molecules created new surface (mid-gap energy) states (SS) in TiO2 and these SS played a major role in the electron transport kinetics. Mott-Schottky analysis of DSSCs under dark conditions was carried out to find the shift in the flat band potential of TiO2 upon OA modification. Surprisingly, no trade off between V OC and J SC was observed after interfacial modification with OA. The dynamics of charge recombination and electron transport at the photoanode|electrolyte interface were studied in detail using electrochemical impedance spectroscopy.
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