Theoretical Insights into Optoelectronic Properties of Non-Fullerene Acceptors for the Design of Organic Photovoltaics

Organic photovoltaics based on non-fullerene acceptors (NFAs) have gained enormous interest over the past few years. Recent fused-ring systems such as ITIC, IDT, and Y families are particularly promising for several photovoltaic devices. Since the complexity of these molecular designs has grown substantially, the development of materials with specific properties has become a laborious process. Therefore, many studies employ computational modeling, in particular density functional theory (DFT), to anticipate material electronic properties. Such approaches provide useful information about proposed organic semiconductors, such as optical absorption, frontier orbital energy levels, and molecular geometries. However, the accuracy of the common methods for recent organic semiconductors has not been explored. Thus, we herein evaluate a series of DFT functionals and Hartree-Fock (HF) theory for a collection of 14 common NFAs. Computational results are compared with physical properties from cyclic voltammetry, photoelectron spectroscopy, UV-visible absorption spectroscopy, and ellipsometry. By applying empirical corrections from linear fits, mean absolute errors between theoretical and experimental results below 0.05 eV could be achieved for the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies as well as maximum absorption energies. Moreover, all of these experimental results for these 14 common NFAs could be useful for future device optimization.