Hole extraction layer utilizing well defined graphene oxide with multiple functionalities for high-performance bulk heterojunction solar cells

A simple method for synthesizing a series of graphene oxide with precise oxidation (pr-GO) (mild oxidation, moderate oxidation and severe oxidation) has been successfully developed. pr-GOs present multiple functionalities which is an excellent hole extraction material. Moderate oxidated pr-GO-3 as hole extraction layer (HEL) exhibited an improved 3.74% in power conversion efficiency and better air-stability compared to devices with other pr-GOs and conventional PEDOT:PSS HEL.83