Pyridyl anchored indolium dyes for the p-type dye sensitized solar cell

Three new thiophenyl bridged triarylamine-donor based dyes with pyridyl anchoring groups and indolium acceptors have been synthesized and studied as sensitizers for the p-type dye-sensitized solar cell (p-DSSC). Compared to known dicyano and pyridinium dyes with the same triarylamine cores, these new sensitizers have broadened and red-shifted UV–vis absorption spectra, with high extinction coefficients and absorption extending beyond 700 nm. TD-DFT calculations on the indolium family indicate that these dyes combine strong donor acceptor communication, with a high degree of charge separation in the excited state – an ideal combination for sensitizer dyes. The phenylpyridyl anchored bis-indolium gives the highest power conversion efficiency (0.097%) through a short circuit photocurrent (JSC) of 3.04 mA cm−2, open circuit voltage (VOC) of 97 mV and fill factor of 36%. This exceeds the performance of the P1 reference dye in this study, and represents the best performance so far for a cationic, pyridine anchored p-DSSC dye.