DFT and molecular dynamics study of the optical and electronic properties of nitrobenzofurazan-based molecules for photovoltaic and nonlinear optical applications

This study explores the properties of small organic conjugated molecules based on nitrobenzofurazan (NBD), incorporating a donor-acceptor (D-A) system, using Density Functional Theory (DFT) and molecular dynamics simulations. These molecules, named NBD-Mi (where i ranges from 1 to 4), were analyzed with DFT and TD-DFT calculations (B3LYP/6-311G(d,p)) in acetonitrile solvent to determine their geometric, electronic, optical, binding energy, and charge transport properties. Radial distribution functions (RDFs) from molecular dynamics (MD) simulations provided insights into the spatial distribution of solvent molecules around NBD-Mi, while intermolecular interactions were modeled using Lennard-Jones and electrostatic potentials. Functionalizing NBD-Mi with suitable donor groups resulted in narrower bandgaps (ranging from 2.12 to 1.69 eV) and increased maximum absorption wavelength (λmax), thereby enhancing light-harvesting efficiency. These compounds exhibited lower binding energies (Eb = 0.299–0.472 eV), which suggests faster exciton dissociation due to significant charge transfer. Charge carrier mobilities for electrons and holes, calculated based on reorganization energy (λe, λh) values, indicate that these materials are effective for electron transport, resulting in solar cells with power conversion efficiencies (PCE) ranging from 7.1 % to 10.5 %. Additionally, the compounds displayed high static dipole moments (μtot), significant linear polarizabilities (αISO and αANISO), and substantial hyperpolarizabilities (β0 and γ0), highlighting their potential as excellent nonlinear optical (NLO) materials.