Development of a multi-steps CVD process to produce bi-layers graphene for anode of Organic Light Emitting Diodes

Graphene is one of the most interesting candidates for the next generation of transparent conductive electrodes (TCEs) for electrical devices, because of its unique electronic structure. Furthermore, the optical transparency of graphene films surpasses that of conventional TCEs such as indium tin oxide (ITO) [1]. However, graphene anode for Organic Light Emitting Diodes (OLEDs) still presents several problems owing to its low work function and high sheet resistance [1], which may be related to a poor control of graphene quality. Chemical vapor deposition (CVD) on copper from methane seems to be the most efficient approach to form high quality transferable graphene for opto-electronic applications, due to the potential for commercially viable production at large scale. However, CVD processes need to be optimized for obtaining selective single or bilayers growth, as well as highly crystalline, full coverage, large area domains [2]. Indeed, CVD graphene films are typically composed of relatively small polycrystalline flakes. A high density of grain boundaries degrades the properties of graphene [2]. Thus, it is desirable to prepare large single-crystal graphene to minimize the impact of defects existing at grain boundaries. The most recent studies of the literature show that this objective can be met by using very low concentration of methane (