Design of Hexabenzocoronene Derivatives as Non-Fullerene Acceptors in Organic Photovoltaics by Bridging Dimers and Modulating Structural Twists

Abstract

Non-fullerene small molecule (SM) acceptors possess many advantages, such as simple synthesis and purification, easily modulated spectrums and energy levels compared with fullerenes. Herein, a series of acceptor molecules 1–14 based on halogenated hexabenzocoronene derivative (8F-8Cl-cHBC) dimers, which could be synthesized in experiment, were rationally designed via benzothiadiazole (BT) bridging and closed rings in cHBC to change structural twists. The electronic structures and energy levels related to open circuit voltage (VOC), as well as the absorption spectra related to short circuit current density (JSC) of 1–14 have been systematically investigated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT). Meanwhile, the intermolecular charge transfer rates (kinter-CT) and charge recombination rates (kinter-CR) of the interface α-sexithienyl (6T)/1–14 were investigated by Marcus semi-classical model. The results revealed that bridging 8F-8Cl-cHBC dimers could significantly adjust the energy level, increase the photon collection and form spectral complementarity with donor. The change of closed rings for cHBC units could improve the morphology, adjust π-π interaction, and form three–dimensional (3D) charge transmission, and thus increased interface electronic transmission channel. Therefore, our designed acceptors will provide a theoretical guideline for designing new non-fullerene SM acceptors containing bridged dimers and structural twists.