New benzoselenadiazole-based D-A-π-A type triarylamine sensitizers for highly efficient dye-sensitized solar cells

Three new D-A-π-A configuration organic dyes (LC-6, LC-7 and LC-8) based on triphenylamine as the electron donor, benzoselenadiazole (BSD) as the auxiliary acceptor, either thiophene or benzene as the π spacer and cyanoacetic acid as the anchoring group have been designed and synthesized for dye-sensitized solar cells (DSCs). Introduction of octyloxy chain on the triphenylamine unit was found to be able to redshift the absorption spectra and suppress the charge recombination. It was also found that using the benzene instead of thiophene as π spacers and using CDCA coadsorbent could help to improve the Jsc and Voc values of the cell. Under standard global AM 1.5 solar light conditions, a DSC employing a dye with a 1,4-phenylene unit with CDCA gave the best photovoltaic performance with a Jsc of 13.21 mA cm−2, a Voc of 734 mV, a FF of 0.69 and an overall PCE of 6.72%. These results suggest that the BSD unit can be a promising electron-withdrawing candidate in D-A-π-A type sensitizers for further exploration DSCs.