Design and computational analysis of nitrobenzofurazan-based non-fullerene acceptors for organic solar cells: A DFT and molecular dynamics simulation study

Abstract

This study explores the design of innovative nitrobenzofurazan (NBD)-based non-fullerene acceptors (NFA), labeled as Ai (i = 1–5), using density functional theory (DFT) and molecular dynamics (MD) simulations in acetonitrile. These donor-acceptor small molecules incorporate nitro or fluorine substituents into the NBD core to enhance non-fullerene organic solar cells (NF-OSCs) performance. The electron-withdrawing nature of these groups reduces frontier orbital energy levels, improving electronic properties critical for device efficiency. Intermolecular energies, including electrostatic and Lennard-Jones interactions, were calculated for Ai/acetonitrile mixtures, providing insight into interaction potentials. DFT and TD-DFT analyses revealed the molecules’ geometric structure, optoelectronic features, optical behavior, and charge transport properties of the designed molecules. These compounds exhibit narrower band gaps ranging from 2.25 to 1.67 eV, along with high absorption maximum (λ_max between 463 and 472 nm). Furthermore, the lower binding energies (E_b = 0.48–0.55 eV), indicate enhanced exciton dissociation efficiency, driven by significant charge transfer from donor to acceptor, as confirmed by FMOs, PDOS, MEP, and TDM analyses. The designed molecules exhibit remarkable photovoltaic performance, including higher open-circuit voltages (V_oc) and large fill factors (FF). Among these, A₄ emerges as the most promising candidate due to its reduced optical bandgap, maximum absorption wavelength, and superior electronic and photovoltaic properties. Blending A₄ with an NBD-based donor highlights efficient charge transfer dynamics, reinforcing its strong potential for practical applications in OSCs. This work highlights the potential of NBD-based NFAs in advancing NF-OSC technology, providing a platform for designing efficient, high-performance photovoltaic materials.