Pyrrole/thiophene π-bridged two triphenylamine electron donor and substituted thiobarbituric electron acceptor for D-π-A-D-featured DSSC applications

We designed a series of organic dyes based on two triphenylamine units (electron donors), pyrrole/thiophene (π-bridge) and N-substituted alkyl thiobarbituric acid (electron acceptors) to construct the D-π-A-D photosensitizer systems. The electronic structures and photophysical properties of the sensitizers were investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). The potential use of the dyes as photosensitizers in DSSCs was explored by calculating the light harvesting efficiency (LHE), electrons driving force injection (ΔG^inject), the open-circuit photovoltage (V_OC), and surface interaction with semiconductor (TiO₂). From alkyl-substituted sensitizers, N-ethyl derivatives TPAA3 and TPAB3 performance for ΔG^inject (−1.69 and −1.65 eV) and V_OC (1.43, and 1.11 eV) was superior to the other dyes. In addition, the anchoring ability of the N-substituted alkyl derivatives was higher than the cyanoacrylic dyes.