Naphthalene-fused octacyclic electron-donating central core constructs non-fullerene acceptors for organic solar cells

To develop new central core structure, we designed and synthesized a naphthalene-fused octacyclic electron-rich block, named as NITT. With the NITT ladder-type core and two distinct terminal groups (IC-2F and CPTCN-Cl), two novel A-D-A-type non-fullerene acceptors (NFAs), namely NITT-BF and NITT-ThCl, were constructed. Two NFAs exhibit broad and intense absorption and high electron mobility due to the coplanar architecture. When blended with polymer donor PM6, NITT-BF-based device acquires more favorable morphology, higher exciton dissociation and charge collection efficiency, and higher and more balanced hole/electron mobilities, resulting in the significantly improved short-circuit current density (JSC) of 18.08 mA cm(-2) and fill factor (FF) of 72.38%. Additionally, both NITT-BF- and NITT-ThCl-based devices deliver very high open-circuit voltages (VOCs) (0.94 V for NITT-BF-based device and 0.97 V for NITT-ThCl-based device). Therefore, PM6:NITT-BF-based device yields an optimal PCE of up to 12.30%, which is much higher than that of PM6:NITT-ThCl-based device (9.58%). Notably, the high PCE of 12.30% is one of the best values for naphthalene-fused NFAs in organic solar cells (OSCs). These results indicate that the linear ladder-type NITT is a promising electron-donating core for constructing high-performance NFAs and terminal strategy is a good way to further boost the photovoltaic performance of OSCs.