End-group modulation of phenazine based non-fullerene acceptors for efficient organic solar cells with high open-circuit voltage

Phenazine-based non-fullerene acceptors (NFAs) have demonstrated great potential in improving the power conversion efficiency (PCE) of organic solar cells (OSCs). Halogenation is known to be an effective strategy for increasing optical absorption, refining energy levels, and improving molecular packing in organic semiconductors. Herein, a series of NFAs (PzIC-4H, PzIC-4F, PzIC-4Cl, PzIC-2Br) with phenazine as the central core and with/without halogen-substituted (dicyanomethylidene)-indan-1-one (IC) as the electron-accepting end group were synthesized, and the effect of end group matched phenazine central unit on the photovoltaic performance was systematically studied. Synergetic photophysical and morphological analyses revealed that the PM6:PzIC-4F blend involves efficient exciton dissociation, higher charge collection and transfer rates, better crystallinity, and optimal phase separation. Therefore, OSCs based on PM6:PzIC-4F as the active layer exhibited a PCE of 16.48% with an open circuit voltage (V_oc) and energy loss of 0.880 V and 0.53 eV, respectively. Accordingly, this work demonstrated a promising approach by designing phenazine-based NFAs for achieving high-performance OSCs.