Ternary non-fullerene polymer solar cells with 13.51% efficiency and a record-high fill factor of 78.13%

Non-fullerene polymer solar cells (NF PSCs) have attracted much attention in recent years due to their rapidly increasing power conversion efficiency (PCE). In this work, two highly efficient ternary NF PSCs with FFs over 78% and PCEs up to 13.52% and 12.70% are demonstrated by adding a strongly aggregating polymer P1 into the classic PBDB-T:IT-M and PBDB-T:ITIC non-fullerene blends. The addition of P1 significantly enhances the crystallization of the blend film, while maintaining the desired morphology. The ternary devices show highly improved charge extraction and suppressed charge recombination in comparison to the binary mixture. The PCE of the PBDB-T:ITIC based NF PSC was found to increase from 10.82% to 12.70% and the FF from 71.85% to 78.07% after adding P1. For the PBDB-T:IT-M based NF PSC, the PCE increases from 11.71% to 13.52% and the FF from 72.07% to 77.83%. The high FFs and PCEs are the best results reported for ternary NF PSCs to date.