A universal nonfullerene electron acceptor matching with different band-gap polymer donors for high-performance polymer solar cells†
Unlike fullerene derivatives, current nonfullerene n-type organic semiconductor (n-OS) electron acceptors can rarely work efficiently with different band-gap polymer donors in polymer solar cells (PSCs). To address this issue, we designed and synthesized a new n-OS electron acceptor, namely m-MeIC, which is proved to be effective with different band-gap polymer donors including wide band-gap J71, medium band-gap PBDB-T and low band-gap PCE-10. Photovoltaic devices based on J71:m-MeIC and PBDB-T:m-MeIC achieved power conversion efficiencies (PCEs) as high as 12.08% and 10.93%, respectively. The difference in PCEs between the devices based on J71 and PBDB-T is mainly ascribed to the gap of the open circuit voltage. It should be mentioned that the J71-based device exhibited an energy loss of 0.62 eV, which is significantly lower than the most reported energy loss. For the low band-gap polymer donor PCE-10, the device also showed a relatively high PCE of 8.34%. The different device performances are analyzed in depth from charge transport and collection, to recombination loss mechanism and morphology of blend films. This work reveals that the new n-type organic semiconductor is very promising as a universal nonfullerene acceptor, pairing with different band-gap polymer donors.