Preparation of graphene oxide used for flexible electrodes and inverted polymer solar cells

Abstract

Graphene oxide (GO) consists of a two-dimensional (2D) sheet of covalently bonded carbon stoms bearing various oxygen functional groups (e.g., hydroxyl, epoxide and carbonyl groups). GO also has large specific area, excellent electrochemical stability, high conductivity and high mechanical strength; therefore it has been used in many applications such as electrode for supercapacitor, polymer electrolyte fuel cells (PEMFCs) and inverted polymer solar cells (PSCs). Graphene oxide was prepared by modified Hummers method and converted into conductive state by chemically reduction to reduced graphene oxide (RGO). The ratio between graphite powder and potassium permanganate used in the Hummers method to synthesize GO was varied from 1:1, 1:3, 1:5, 1:7 and 1:9 ratios. The 1:7 ratio give the best coating when using the layer-by-layer technique. RGO was reduced by using p-toluenesulfonyl hydrazide (p-TSH) and improved dispersible by adding poly (styrene sulfonate) (PSS). RGO-PSS composite was mixed with PANi-PSS synthesized by interfacial polymerization RGO/PANi composite was use as interfacial layer between PTB7:PC71BM as active layer and Poly (ethylene dioxythiophene) : poly (styrenesulfonate) (PEDOT:PSS) as HTL by RGO/PANI composite in water phase by spin-coating. GO and RGO were characterized by TEM for morphology. The chemical and exfoliated structure was investigated by FTIR and XRD, respectively. PANi-PSS was investigated by UV-Vis spectrophotometer. The electrical conductivity was study by TLM method.