Efficient designing of half-moon-shaped chalcogen heterocycles as non-fullerene acceptors for organic solar cells

One key strategy to further improve the power conversion efficiency (PCE) of organic solar cells (OSCs) is to incorporate various complementary functional groups in a molecule. Such strategies proved attractive for tuning the photovoltaic performances of the materials and can show a much higher absorption phenomenon with narrower band gaps. Despite the outstanding benefits, materials selection and their efficient modeling is also an extremely challenging job for the development of OSCs materials. In this manuscript, we proficiently developed an efficient series of small molecule-based non-fullerene acceptors (SM-NFAs) SN1-SN9 for OSCs and characterized by density functional theory (DFT) and time-dependent DFT (TD-DFT). The characteristics required to estimate electron and hole mobility, and open-circuit voltage (V-oc) were investigated by optimizing the geometrical parameters, absorption spectra, exciton binding energy, frontier molecular orbitals (FMOs), electronic structures, and charge transfer rates. The outcomes of these materials showed that all newly constructed small-molecule-based non-fullerene acceptors exhibit broader and better absorption efficiency (lambda(max) = 761 to 778 nm) and exciton dissociation, while much lower LUMO energy levels which may help to enhance the reorganizational energies. Further, a narrow bandgap also offers better photovoltaic properties. Hence, the designed molecules exhibited narrow bandgap values (E-g = 2.82 to 2.98 eV) which are lower than that of the reference molecule (3.05 eV). High V-oc and photocurrent density values with lower excitation and binding energies eventually increase the PCEs of the OSC devices. The obtained results have shown that designed molecules could be effective aspirants for high-performance OSCs.

Automated summary

One key strategy to improve the power conversion efficiency of organic solar cells is to incorporate various functional groups in a molecule. In this study, a series of small molecule-based non-fullerene acceptors were developed for organic solar cells. The materials were characterized using density functional theory and time-dependent density functional theory. The results showed that these materials exhibited higher absorption efficiency and lower energy levels, which could enhance the performance of the solar cells.