Role of Thiophene-Based Halogenated Non-Fused Ring Containing Acceptor Molecules for Efficient Organic Photovoltaics

Halogenated nonfused rings containing molecular acceptors are considered widely owing to their potential to be lightweight, and flexible, and improve the electron mobility and overall charge transfer process in organic solar cells (OSCs). Herein, we designed a new series of nonfused ring acceptors ATH1-ATH11 by modulating the synthetic reference molecule ATH-R. Incorporating CN, NO 2 , COOCH 3 , F and Cl atoms greatly impacts the molecular structures and electronic properties, which could potentially enhance [Formula: see text]-[Formula: see text] stacking, electron mobility and overall charge transfer phenomenon. This designed series (ATH1-ATH11) along with the synthetic reference ATH-R is characterized by advanced quantum chemical simulations using various density functional theory (DFT) and time-dependent DFT (TD-DFT) approaches. The incorporation of those end-capped functionals helps in narrowing the energy gap of the designed series and also enhances the absorption characteristics from synthetic reference 709.62 nm to designed ATH-5 832.05 nm. The dispersion of frontier molecular orbitals reveals the formation of lower HOMO levels, when coupled with a relatively minor reduction in LUMO levels, can facilitate the narrowing of the energy gap in the materials. Moreover, the designed ATH1-ATH11 series shows reduced exciton binding energy and excitation energy in contrast to the synthetic reference ATH-R molecule. The reduced values of reorganization energy revealed that these molecules could be efficiently employed as efficient molecular acceptors. The charge transfer analysis of the donor: acceptor blend (PTB7-Th: ATH5) displayed a good charge transfer phenomenon at the donor–acceptor interface. Furthermore, a newly designed series (ATH1-ATH11) shows the improved optoelectronics and photovoltaic characteristics of the molecules rather than the synthetic reference ATH-R molecule. These outcomes revealed the potential of molecular modeling of halogenated nonfused rings to improve the photovoltaic performances of OSCs.