The application of single-layer graphene modified with solution-processed TiOx and PEDOT:PSS as a transparent conductive anode in organic light-emitting diodes

Abstract

There are many challenges for a direct application of graphene as the electrodes in organic electronics due to its hydrophobic surfaces, low work function (WF) and poor conductance. The authors demonstrate a modified single-layer graphene (SLG) as the anode in organic light-emitting diodes (OLEDs). The SLG, doped with the solution-processed titanium suboxide (TiOx) and poly(3,4-ethylenedio-xythiophene)/poly(styrene sulfonic acid) (PEDOT:PSS), exhibits excellent optoelectronic characteristics with reduced sheet resistance (Rsq), increased work function, as well as over 92% transmittance in the visible region. It is notable that the Rsq of graphene decreased by ∼86% from 628Ω/sq to 86Ω/sq and the WF of graphene increased about 0.82eV from 4.30eV to 5.12eV after a modification by using the TiOx–PEDOT:PSS double interlayers. In addition, the existence of additional TiOx and PEDOT:PSS layers offers a good coverage to the PMMA residuals on SLG, which are often introduced during graphene transfer processes. As a result, the electrical shorting due to the PMMA residues in the device can be effectively suppressed. By using the modified SLG as a bottom anode in OLEDs, the device exhibited comparable current efficiency and power efficiency to those of the ITO based reference OLEDs. The approach demonstrated in this work could potentially provide a viable way to fabricate highly efficient and flexible OLEDs based on graphene anode.