n-Type conjugated electrolytes cathode interlayer with thickness-insensitivity for highly efficient organic solar cells

Two novel amphipathic small molecular conjugated electrolytes (SMCEs) with self-doping effect were successfully synthesized by incorporating diketopyrrolopyrrole (DPP) as n-type backbone and amine-based groups as polar pendants. In favor of the n-type backbone and amine-based groups, an obvious n-type doping was obtained, resulting in the dramatically improved conductivity of the SMCEs. The formation of the polar group induced dipoles at the SMCEs/Al interface to provide a favorable energy for cathode. Subsequently, the two small molecule electrolytes as cathode interlayers have been successfully applied in the polymer solar cells (PSCs) with a wide thickness range from 7–33 nm. A notable power conversion efficiency (PCE) of 10.2% for PSCs were achieved. And the two SMCEs also showed a good universality with substantial performance. These findings indicate that these small molecular conjugated electrolytes are promising candidates as cathode interlayers for highly efficient polymer solar cells.