A novel non-conjugated small-molecule electrolyte was invented as cathode interlayer in PTB7:PC71BM-based polymer solar cells(PSCs).We discovered a significant synergy effect for improving device efficiency between methanol treatment and the interlayer.Methanol treatment mainly attributed to the open-circuit voltage,while the interlayer primarily enhanced short-circuit current and fill factor.Under the effective synergy effect power conversion efficiencies(PCEs)of PTB7:PC71BM-based PSCs were largely improved from 3.89%to 9.79%for the conventional PSCs and from 7.34%to 9.10%for the inverted PSCs.Our findings break a new path of interfacial modification for highly efficient PSCs.