New semi-rigid triphenylamine donor moiety for D-π-A sensitizer: Theoretical and experimental investigations for DSSCs

Four novel dyes featuring new semi-rigid triphenylamine donor groups have been synthesized and successfully employed as sensitizers in dye-sensitized solar cells (DSSCs). Opting for the new semi-rigid triphenylamine (tPA) electron-donating unit yielded a better Voc and Jsc resulting to a power conversion efficiency (PCE) which is 16% higher compared to a reference dye whose electron-donating group is a conventional tPA unit. Density functional theory (DFT) and time-dependent DFT calculations revealed the more favorable charge-transport properties of the dye based on the new semi-rigid donor unit. Among the synthesized dyes, the DSSC device based on Dhkx-4 dye in conjunction with iodine-based electrolyte achieved a PCE of 6.23%, with Voc of 0.661 V, Jsc of 13.31 mAcm−2, and FF of 0.71 under simulated AM 1.5 G condition. Therefore, the novel semi-rigid tPA donor unit presented in this work is a promising donor group for a sensitizer in DSSCs and systematic structural engineering of the presented designs could offer valuable contributions for the development of the photovoltaic devices.