Decoding non-fullerene acceptors for organic solar cells: a theoretical structure-property-performance perspective.

Organic solar cells (OSCs) have become promising next-generation photovoltaic technologies because of their flexibility, solution processability, and light weight. However, the use of traditional fullerene-based acceptors has been hampered by poor absorption, poor tunability, and energy losses that require the fabrication of sophisticated materials like non-fullerene acceptors (NFAs). The purpose of this review is to provide multi-faceted theoretical insight into the structure-property-performance relationship in NFAs with emphasis on how electronic structure, optical behavior, charge transport and eventual device efficiency can be impacted under the influence of molecular design. It is analyzed systematically through theoretical and computational methods such as density functional theory (DFT), time-dependent DFT (TD-DFT), molecular dynamics simulations and machine learning (ML) methods. Such techniques are used to measure important descriptors including HOMO-LUMO energy levels, bandgap, reorganization energy, dipole moment, exciton binding energy and molecular packing. The work shows that optoelectronic properties can be accurately tuned using rational molecular engineering