How the Nature of Triphenylamine-Polyene Dyes in Dye-Sensitized Solar Cells Affects the Open-Circuit Voltage and Electron Lifetimes

Three donor-linker-acceptor triphenylamine-based cyanoacrylic acid org. dyes used for dye-sensitized solar cells (DSCs) were examd. with respect to their effect on the open-circuit voltage (Voc). The previous study showed a decrease in Voc for DSCs based on dyes with increased mol. size (increased linker conjugation). The authors study the origin of Voc with respect to (a) conduction band (ECB) positions of TiO2 and (b) degree of recombination between electrons in TiO2 and electrolyte acceptor species at the interface. These parameters were studied as a function of dye structure, dye load, and I2 concn. Two types of behavior were identified: the smaller polyene dyes show a surface-protecting effect preventing recombination upon increased dye loading, whereas the larger dyes enhance the recombination. How the different dye structures affect the recombination is discussed in terms of dye surface blocking and intermol. interactions between dyes and electrolyte acceptor species.