Cyclopentadithiophene bridged organic sensitizers with different auxiliary acceptor for high performance dye-sensitized solar cells

Abstract

A series of triphenylamine-based dye sensitizers were designed by modifying the auxiliary acceptors and their positions for the potential use in dye-sensitized solar cells (DSSCs). The geometrical structures, photoinduced charge transfer character together with optical properties for these dyes adsorbed on (TiO2)6 have been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The effects of auxiliary units and their positions on the optoelectronic properties of the dyes are demonstrated. The results illustrate that the dyes with auxiliary acceptors close to the cyanoacrylic acid show very narrow band gap (HOMO-LUMO), leading to an obvious red-shifted absorption band in contrast to the dyes with additional acceptors next to the donor part. Further analyses of the dye-(TiO2)6 systems manifest that there has strong electronic coupling between the dyes and the (TiO2)6 surface. The results are expected to provide a useful reference to the future design and optimization for new highly efficient metal-free organic dyes.