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

Abstract

Herein, two simple polymers PFO3 and PFO4 based on furan-3-carboxylate and 3-alkylfuran are developed. PFO3 and PFO4 feature high hole mobility, large dielectric constant and good solubility. Compared to PFO4, PFO3 with shorter oligoethylene glycol (OEG) side chains demonstrates a larger absorption coefficient and deeper electronic energy level. The air- and ethanol/water-processed OSCs based on the 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 retain 64.5% and 51.2% of their initial efficiency after continuous illumination for 200 h in an inert atmosphere, respectively. Surprisingly, the retained 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 an inert atmosphere. However, the above phenomenon is not observed for three other photovoltaic systems without abundant OEG groups when adopting discontinuous illumination. Infrared spectroscopy and X-ray photoelectron spectroscopy unravel that the repair efficiency of PFO3- or PFO4-based devices should have resulted from the self-healing of hydrogen bonds in the photoactive layer. Our work will provide guidance for the future design of donor polymers for eco-friendly OSCs featuring high stability.