High-performance polymer solar cells with radiation-induced and reduction-controllable reduced graphene oxide as an advanced hole transporting material

We demonstrate that radiation-induced reduced graphene oxide (RrGO) can efficiently function as a hole transporting layer (HTL) for polymer solar cells (PSCs). The solutionprocessable RrGO was simply obtained by γ-ray irradiation of a graphene oxide (GO) solution dispersed in ethanol and water. Changes in the chemical composition, conductivity, work-function, and morphology in RrGO films that resulted from the increase in absorbed dose amounts were systematically investigated. In addition, GO, a conventional hydrazinebased GO (CRGO), and the RrGOs were also studied as HTLs in PSCs, and as a result, the RrGO-based PSC showed more enhanced PSC performance than those of GO and CRGO due to better conductivity than GO and better film morphology and work function than CRGO. More importantly, the best RrGO-based PSC showed comparable cell performance to the conventional poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-based PSC and better stability than PEDOT:PSS, indicating that the use of the RrGO is more desirable as an efficient HTL than the PEDOT:PSS for high-performance and high-stability PSCs.