Synthesis of triphenylamine-based thiophene-(N-aryl)pyrrole-thiophene dyes for dye-sensitized solar cell applications

Two new triphenylamine-based metal-free organic dyes (TPTDYE-1 and TPTDYE-2) containing 1-(2,6-diisopropylphenyl)-2,5-di(2-thienyl)pyrrole as a new π-conjugated chromophore were synthesized for dye-sensitized solar cell (DSSC) applications. TPTDYE-1 containing three donor groups around the acceptor group was found to show relatively narrow absorption band from 300 nm to 470 nm while TPTDYE-2 having extended π-π delocalization between the donor and acceptor group showed broad absorption band from 300 nm to 550 nm. The electrochemical studies indicate that the HOMO-LUMO energy gap of TPTDYE-1 is considerably wider than that of TPTDYE-2. The dye-sensitized solar cell performance of each dye was investigated, and the TPTDYE-2-sensitized cell was found to show a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 75%, a short-circuit photocurrent density (Jsc) of 13.50 mA/cm2, an open-circuit voltage (Voc) of 0.72 V, and a fill factor (FF) of 0.69, corresponding to an overall conversion efficiency of 6.71% under simulated AM 1.5 irradiation (100 mW/cm2). Under the same condition the TPTDYE-1-sensitized cell showed the same IPCE value of 75% with a promising conversion efficiency of 6.00%, a Jsc of 11.11 mA/cm2, a Voc of 0.76 V, and a FF of 0.71.