Tunable spectra and charge transfer process of benzodifurandione-based polymer by sulfur substitution

Abstract

The ground state geometry, optical and charge transport properties of benzodifurandione-based PPV (BDPPV) have been studied with density functional theory methods. Firstly, the frontier molecular orbitals, energy gap (Δ_H–L), ionization potentials (IP) and electron affinities (EA), optical absorption spectra of BDPPV were obtained in the framework of DFT and TD-DFT. Reorganization energy and charge transfer integral were estimated to calculate the drift mobility. Thereafter, we further studied the effect of sulfur atoms substitution and external electric fields on the spectra response and charge transport properties. The calculated results showed that for BDPPV, the drift mobility of electrons is higher than that of the holes due to the strong charge coupling strength. The substitution of oxygen by sulfur atoms has a significant influence on the bond length, dihedral angle and the energy levels of the frontier molecular orbitals; at the same time, the absorption wavelengths can be effectively adjusted by controlling the numbers and sites of substituted sulfur atoms. When two pairs sulfur atoms were introduced (such as Su4), it exhibits a good optical response and improves the charge transport ability, suggesting that molecules with two pairs sulfur atoms substituted could be an optimal candidate for optic-electron materials.