First principle theoretical designing of W-shaped Dithienosilole-based acceptor materials having efficient photovoltaic properties for high-performance organic solar cells

Abstract

The key strategy to enhance the intra-molecular push-pull effects by broadening the optial absorption of small molecule based organic photovoltaic (SM-OPV) materials is considered an effective approach to enhance the power conversion efficiencies (PCEs) of SM-OPV devices. However, in case of acceptor materials, the highly desirable molecular modelling strategy of halogenation generally effects in downward-shifting of molecular energy levels, resulting decrease in open-circuit voltages (Voc) in the devices. Herein, we investigate a fluorinated, chlorinated and cyanide (CN) based end-capped acceptor materials, which shows a broader optical absorption phenomenon and exhibited a good voltages than it chlorinated counterparts. These new molecularly engineered SM-OPV were characterize theoretically by density functional theory (DFT) and time-dependent (TD-DFT) approaches. The estimation of electron/hole mobility, and Voc was done by calculating the geometric parameters, electronic structures, frontier molecular orbitals (FMOs), charge transfer rates, and exciton binding energies of the designed OPV materials. The outcomes of these investigations revealed that all newly engineered SM-OPV acceptor materials displays an enhanced exciton dissociation and absorption efficiency and underneath LUMO levels which might be responsible to improve the Voc, reorganization energies, and photo-current density parametrs, resulting enhancement in the PCEs of the organic solar cells (OSC) devices.