18.4% efficiency achieved by the cathode interface engineering in non-fullerene polymer solar cells

•A novel cathode interlayer SME1 can be synthesized through simple one-step Suzuki coupling reaction between two commercialized monomers with nearly no batch differences.•One of top PCEs of 18.4% (the third-party certification is 17.9%) has been achieved in single-junction binary devices.•The valid doping effects endow SME1 with the first-class electron-transport capability.•SME1 can also extract electrons from polymer donors due to the matched energy levels alignment.•SME1 possesses the excellent universality in varied non-fullerene systems.