Roll-to-roll compatible quinoxaline-based polymers toward high performance polymer solar cells†
In this article, two D–A-type quinoxaline-based polymers with multiple fluorine atoms, denoted by PB-QxF and PBF-QxF, were synthesized and tested for polymer solar cells (PSCs). Owing to the excellent optical, electrochemical, and charge transport properties of these polymers, impressive PCEs of 10.99 and 13.96% were achieved by the inverted-type lab-scale spin-coated devices based on PB-QxF and PBF-QxF, respectively, in the presence of a nonfullerene Y6 acceptor. In addition, to evaluate the feasibility of the process for mass production, a scalable roll-to-roll (R2R) slot-die coating process was attempted to fabricate PSCs on flexible substrates. Notably, the best PCE of 9.63% was obtained using an R2R processed additive-free PSC based on PBF-QxF, which is the highest value among all R2R processed PSCs. Moreover, the device with PBF-QxF exhibited good thickness tolerance to PCE up to 350 nm, which is one of the key requirements for R2R compatible materials.