18% efficiency of ternary organic solar cells enabled by integrating a fused perylene diimide guest acceptor

Constructing ternary organic solar cells (OSCs) has been the widely used and effective strategy to further enhance photovoltaic performance. Here, a novel perylene diimide (PDI) derivative, FPDI-2PDI, was developed by attaching two PDI chromophores to the bay-position of fused PDI dimer. The wide bandgap FPDI-2PDI was used as a guest electron acceptor in the classic PM6:Y6 system. The top-performing ternary device achieved simultaneously increased open-circuit voltage (V_oc) of 0.848 V, short-circuit current density (J_sc) of 27.47 mA cm^-2 and fill factor (FF) of 77.20%, yielding a significantly improved power conversion efficiency (PCE) of 18.00%, which is much higher than PCE of 16.63% of the control PM6:Y6 binary device. The incorporation of FPDI-2PDI is conducive to improving solar energy utilization, suppressing charge recombination, facilitating exciton dissociation and charge collection while enhancing the blend morphology, thus leading to increased photovoltaic performance in the corresponding ternary device. This work indicates that proper molecular design will make the PDI derivatives to be very competitive guest acceptors to construct high-efficiency ternary OSCs.