Graphene‐based Intrinsically Stretchable Two‐Dimensional‐Contact Electrodes for Highly Efficient Organic Light‐Emitting Diodes

Intrinsically stretchable organic light-emitting diodes (ISOLEDs) are becoming essential components of wearable electronics. However, the efficiencies of the ISOLEDs have been highly inferior to their rigid counterparts, which is due to the lack of ideal stretchable electrode materials that can overcome the poor charge injection at one-dimensional metallic nanowire/organic interfaces. We demonstrate highly-efficient ISOLEDs that use graphene-based two-dimensional-contact stretchable electrodes (TCSEs) that incorporate a graphene layer on top of embedded metallic nanowires. The graphene layer modifies the work function, promotes charge spreading, and impedes inward diffusion of oxygen and moisture. The work function (WF) of 3.57 eV is achieved by forming a strong interfacial dipole after deposition of a newly-designed conjugated polyelectrolyte with crown ether and anionic sulfonate groups on TCSE; this is the lowest value ever reported among ISOLEDs, which overcomes the existing problem of very poor electron injection in ISOLEDs. Subsequent pressure-controlled lamination yielded a highly efficient fluorescent ISOLED with an unprecedently high current efficiency of 20.3 cd/A, which even exceeds that of an otherwise-identical rigid counterpart. Lastly, a three-inch five-by-five passive matrix ISOLED was demonstrated using convex stretching. This work can provide a rational protocol for designing intrinsically stretchable high-efficiency optoelectronic devices with favorable interfacial electronic structures. This article is protected by copyright. All rights reserved