Influence of the antennas in starburst triphenylamine-based organic dye-sensitized solar cells: phenothiazine versus carbazole

A new starburst triphenylamine-based organic dye (WD-1) with phenothiazine units as antenna groups was designed and synthesized and the corresponding dye (WD-4) containing carbazole antennas for the purpose of comparison was also synthesized. They were successfully applied in dye-sensitized solar cells (DSSCs). The photophysical and electrochemical properties of the dyes were investigated by UV-vis spectrometry and cyclic voltammetry. Under standard global AM 1.5 solar conditions, the WD-1 sensitized solar cell gave a short circuit photocurrent density (Jsc) of 9.2 mA cm−2, an open circuit voltage (Voc) of 625 mV, a fill factor (ff) of 0.79, corresponding to an overall conversion efficiency η of 4.54%. Under the same conditions, the WD-4 sensitized cell gave a Jsc of 7.3 mA cm−2, an Voc of 603 mV, and a ff of 0.74, corresponding to an overall conversion efficiency of 3.26%. An increase in η of about 39% was obtained from WD-4 to WD-1. Our findings demonstrate that the introduction of phenothiazine units as antennas in triphenylamine-based dyes could improve photovoltaic performance compared with carbazole units as antennas in DSSCs.