Perylene Diimide-based Non-fullerene Acceptors With A-D-A'-D-A Architecture For Organic Solar Cells.

The vinylene-bridged helical PDI dimer (PDI2) has been an alternative PDI building block for non-fullerene acceptor (NFAs). However, the development of PDI2 derivatives still lag behind, and most of PDI2 derivatives based organic solar cells (OSCs) only achieved a moderate power conversion efficiencies (PCE) of less than 8%. In this contribution, an acceptor-donor-acceptor-donor-acceptor (A-D-A'-D-A) architecture was introduced to facilitate the improvement of photovoltaic properties. Two acceptors named diIDTIC-PDI2 and diFIDTIC-PDI2 were designed and synthesized, in which a PDI2 moiety flanked with two indacenodithiophene (IDT) units was employed as the D-A'-D core and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) or fluorinated IC (IC2F) acted as terminal groups, respectively. The photovoltaic performances of these two acceptors were explored using PM1 as the electron donor. Compared to diIDTIC-PDI2, the fluorinated diFIDTIC-PDI2 based OSCs obtained enhanced photovoltaic performance with the best PCE of 9.77%, a V OC of 0.957 V, J SC of 13.58 mA cm -2 and FF of 75.1%. These results illustrate that engineering terminal groups is a robust strategy of enhancing the efficiency of PDI based acceptors with A-D-A'-D-A architecture.