Computer aided design and evaluation of benzothiadiazole based non-fullerene acceptors for organic solar cells applications

Abstract

Herein, we report the end-capped modification of the recently reported acceptor CH1007. Considering the importance of non-fullerene acceptors, we theoretically designed a series of benzo-thiadiazole core-based acceptors (MS1-MS8) to enhance the photophysical, and photovoltaic properties of the acceptors. In this study, properties like frontier molecular orbitals, maximum absorption, transition density matrix, open-circuit voltage, binding and excitation energies, dipole moment, and partial density of states were estimated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) using B3LYP functional with bases set 6-31G(d,p). When studied computationally, all engineered compounds exhibited red-shift in the absorption spectrum and λmax lie in the range of 734–900 nm, compared to the reference compound (λmax = 735 nm). The designed acceptors exhibited low reorganizational energies (better charge transfer property), low binding and excitation energies besides narrow HOMO-LUMO bandgap. Moreover, the donor–acceptor complexes of the designed acceptors MS1 and MS4 have been studied with well-known standard donors PTB7-Th & PM6. The distribution of electron density in the resultant donor–acceptor complexes showed successful shift of electron density from donor moiety to acceptor moiety. The results revealed that such type of end-capped modifications in acceptors can lead to better photophysical and optoelectronic properties. So, designed compounds have potential to enhance the capacity of acceptor molecules and are therefore, suggested for the development of more efficient organic solar cells (OSCs).