Flexible OLEDs with graphene electrodes on renewable cellulose platforms

Abstract

Graphene shows great potential as a transparent conducting material (TCM) for organic light emitting diodes (OLEDs), particularly in what concerns flexible devices. In this context, a lot of attention has been dedicated to the optimization of the graphene electrodes, to improve their electrical conductivity while maintaining high optical transparency. Moreover, for the development of flexible and sustainable devices, the choice of an appropriate substrate is a critical task. Here, we describe, for the first time, the development of OLEDs employing chemical vapour deposition (CVD) graphene anodes on cellulose nanocrystal (CNC) membranes and cellulose rolling papers. These transparent biodegradable materials provide a more environmentally conscious alternative to the conventional synthetic polymers commonly used as flexible OLED substrates. By stacking multiple graphene layers on these cellulose-based substrates, followed by the evaporation of MoO₃, we improve the electrical conductivity of graphene, allowing us to fabricate third generation solution processed OLEDs, with external quantum efficiencies (EQE) of up to 0.34% and maximum brightness reaching ∼400 cd m⁻². This proof-of-concept demonstration paves the way for novel environmentally friendly flexible OLEDs, realizing the synergic potential of both graphene and cellulose-based materials.