First-principles exploration of truxene–BODIPY architectures as alternative non-fullerene acceptors in organic photovoltaics

Abstract

In this work, we report for the first time a new class of truxene–BODIPY donor–π–acceptor (D–π–A) architectures as non-fullerene acceptors (NFAs) for organic solar cells (OSCs). This novel molecular design direction integrates a modified truxene core with BODIPY derivatives via π-spacers, providing a rational strategy to develop efficient small-molecule acceptors. A combination of density functional theory (DFT) and time-dependent DFT (TDDFT) was employed to investigate their structural, electronic, optical, and photovoltaic properties. Key descriptors such as ionization potential, electron affinity, dipole moment, reorganization energy, and charge transfer rates were evaluated to understand charge transport behavior. Notably, the analysis of reorganization energy confirmed that all designed molecules preferentially support electron transport, validating their role as effective acceptor materials. Frontier molecular orbital (FMO) and density of states (DOS) analyses revealed favorable donor–acceptor orbital alignment, promoting efficient intramolecular charge transfer. Excited-state absorption studies, carried out in both gas and solvent phases, demonstrated strong and tunable absorption in the visible to near-infrared (NIR) region, with a significant red-shift observed upon donor–acceptor blending. Among all blends, the C4/3p system achieves the highest predicted power conversion efficiency (PCE) of 21.18%, highlighting the critical role of D/A compatibility. Overall, this study illustrates the potential of rationally engineered truxene–BODIPY systems as promising non-fullerene small molecule acceptors for next-generation organic photovoltaics.