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

Top Cited Papers
Publisher Website
Google Scholar
Abstract
Three donor−linker−acceptor triphenylamine-based cyanoacrylic acid organic dyes used for dye-sensitized solar cells (DSCs) have been examined with respect to their effect on the open-circuit voltage (Voc). Our previous study showed a decrease in Voc for DSCs based on dyes with increased molecular size (increased linker conjugation). In the present study, we investigate the origin of Voc with respect to (i) conduction band (ECB) positions of TiO2 and (ii) 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 concentration. 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 intermolecular interactions between dyes and electrolyte acceptor species.