Theoretical study on the bridge comparison of TiO2 nanoparticle sensitizers based on phenoxazine in dye-sensitized solar cells

A series of metal-free donor–π-bridge–acceptor dyes based on phenoxazine as the electron donor and cyanoacrylic acid as the electron acceptor groups with different π-spacers were studied by density functional theory (DFT) and time-dependent DFT calculations. The aromatic rings such as benzene, furan, thiophene, pyrrole, thiazole, and silole were used as π-spacer to link the donor and acceptor moieties. All of the dyes with π-spacer exhibited a narrower band gap than the parent molecule without π-spacer due to the π-conjugation expansion. The results showed that the dye with a furan spacer (POXF) is the most efficient sensitizer for dye-sensitized solar cell due to the largest LHE, high Voc, and red-shifted absorption.