Simple furan-based polymers featuring self-healing function enable efficient eco-friendly organic solar cells with high stability

Herein, two simple furan-based polymers PFO3 and PFO4 grafting oligoethylene glycol (OEG) side chains are developed. PFO3 and PFO4 feature high hole mobility, large dielectric constant and good solubility. Compared to PFO4, PFO3 with shorter side chains demonstrates larger absorption coefficient and deeper electronic energy level. The air- and ethanol/water-processed OSCs based on PFO4:fullerene derivative (PCBO-12) show a modest efficiency of 2.06%. However, PFO3:PCBO-12 OSCs yield a higher efficiency of 3.03% due to the simultaneously enhanced photovoltaic parameters. PFO3- and PFO4-based devices remain 64.5% and 51.2% of their initial efficiency after continuous illumination for 200 h in inert atmosphere, respectively. Surprisingly, the remained efficiency ratio is increased to 81.6% and 69.1% for PFO3- and PFO4-based devices suffering from discontinuous illumination yet with the same soaking time of 200 h in inert atmosphere. However, the above phenomenon is not observed for other three photovoltaic systems without abundant OEG groups when adopting discontinuous illumination. The infrared spectroscopy and X-ray photoelectron spectroscopy unravel that the repaired efficiency of PFO3- or PFO4-based devices should be resulted from the self-healing of hydrogen bonds in photoactive layer. Our work will provide guidance for the future design of donor polymers for eco-friendly OSCs featuring high stability.