Achieving 10% efficiency in non-fullerene all-small-molecule organic solar cells without extra treatments

摘要

Non-fullerene all-small-molecule organic solar cells (ASM-OSCs) have attracted considerable attention for industrial application owing to their well-defined molecular structure, high purity and good batch-to-batch reproducibility. However, nearly all the high power conversion efficiencies (PCEs) of ASM-OSCs rely heavily on the extra treatment of their active layers. Herein, two A-pi-D-pi-A-type benzodithiophene trimer (3BDT)-based large planar conjugated rigid small molecules (3BDT-4 and 3BDT-5) were successfully designed and synthesized. When blended with a non-fullerene acceptor (Y6), the 3BDT-4 and 3BDT-5-based solution-processed bulk heterojunction OSCs exhibited PCEs of 5.8% and 10.4% under 1.5G illumination without extra treatment, respectively. To the best of our knowledge, 3BDT-5 is the first small molecule-based OSC device with Y6 as an acceptor to exhibit a PCE breaking 10% without thermal annealing, solvent vapor annealing, or use of additives. More importantly, when using post-treatments on the 3BDT-5:Y6 blend film, the PCEs of the devices did not change obviously. Thus, the excellent photovoltaic properties of 3BDT-5 make it an alternative material for the industrial large-scale fabrication of high-performance OSCs. This result demonstrates that the molecular design method can be a very effective strategy for controlling the active layer morphology.