Rational design non-fullerene acceptor-based high efficiency BHJ polymer solar cells through theoretical investigations

Abstract The development of organic solar cells (OSCs) based on non-fullerene acceptors (NFAs) is a potential way to conquer the dilemma of OSCs based on fullerene derivatives acceptors (FAs). In this article, four promising NFAs, two excellent polymers and eight donor/acceptor (D/A) interfaces based on NFAs and polymers are theoretically investigated using DFT and TD-DFT. Geometric structures, electronic and optical absorption properties of NFAs and polymers were studied in details. By calculating the frontier molecular orbital (FMO) levels, exciton binding energies, optical absorptions and analyzing density-of-states (DOS) and charge difference density (CDD), the roles of NFAs (or polymers) in the FMO energy levels and optical absorptions of D/A interfaces were revealed, and the relationship between exciton binding energy and characteristic of charge separation was uncovered. The obtained charge separation/recombination rates of D/A interfaces prove that all designed D/A interfaces have great potentials for application in OSCs, and this work of optical absorption of D/A interfaces under external electric fields offers a considerable method for tuning the performance of OSC device. We hope our investigation can provide a useful guideline for enhancing the performance of OSCs.