Small Molecules Based on Benzo[1,2-b:4,5-b']dithiophene Unit for High-Performance Solution-Processed Organic Solar Cells

摘要

Small molecules, namely, DCAO_3TBDT and DR3TBDT, with 2-ethylhexoxy substituted BDT as the central building block and octyl cyanoacetate and 3-ethylrhodanine as different terminal units with the same linkage of dioctyltert-thiophene, have been designed and synthesized. The photovoltaic properties of these two molecules as donors and fullerene derivatives as the acceptors in bulk heterojunction solar cells are studied. Among them, DR_3TBDT shows excellent photovoltaic performance, and power conversion efficiency as high as 7.38% (certified 7.10%) under AM 1.5G irradiation (100 mW cm~(-2)) has been achieved using the simple solution spin-coating fabrication process, which is the highest efficiency reported to date for any small-molecule-based solar cells. The results demonstrate that structure fine turning could cause significant performance difference and with that the performance of solution-processed small-molecule solar cells can indeed be comparable with or even surpass their polymer counterparts.