Theoretical insights into donor–acceptor energetic alignment, photovoltaic performance, and systematic acceptor matching of D–A–D donors with fullerene and perylene diimide derivatives

In this comprehensive theoretical investigation, five donor–acceptor–donor (D–A–D) structured donor molecules (M1–M5) were examined systematically for their potential in organic photovoltaic applications. These donors were paired with a selection of fullerene-based acceptors (PCBM, bisPCBM, C₇₀, PC₇₀BM, PCBB, PCBO, TCBM, ICBA) and non-fullerene perylene diimide (PDI) derivatives (PDI-I to PDI-V). Critical photovoltaic parameters, including LUMO energy offsets (ΔE_LUMO), open-circuit voltages (V_oc), fill factors (FF), and power conversion efficiencies (PCE), were rigorously calculated. The optimal donor–acceptor pair, M4/PDI-III, demonstrated a predicted PCE of 10.2 %, highlighting favorable electronic alignments and a near-ideal LUMO offset (0.3 eV) critical for efficient exciton dissociation. Detailed structure–property analyses revealed that increased π-conjugation, backbone planarity, and strategically positioned electron-donating and electron-withdrawing substituents significantly influence photovoltaic performance by modulating frontier molecular orbital energies and electronic reactivity. These theoretical insights provide design guidance and outline plausible synthetic approaches.