The Role of the Bottom Oxide Layer in Oxide-Metal-Oxide (OMO) Electrode for Stretchable Organic Light-Emitting Diodes

The challenges for stretchable organic light-emitting diodes (SOLEDs) have led research into advanced manufacturing processes. Several electrodes have been researched to replace conventional indium tin oxide in SOLEDs due to its brittleness, indium scarcity in earth, and poor deformation capabilities. Oxide-metal-oxide (OMO) electrodes are promising alternatives for flexible/stretchable electronics owing their excellent charge injection and optical transparencies, including mechanical compliance. In this study, two oxides (i.e., MoO3 and V2O5) with different surface energies in an OMO structure to effectively inhibit the island growth of the ultra-thin Au (5 nm) metal is incorporated. The morphology and interfacial coordinate covalent bonds between the seed layer and ultra-thin Au film are extensively studied. The improved ultra-thin Au growth in OMO structure together with figure-of-merit have been employed as the anode for a phosphorescent SOLED structure. The SOLEDs with OMO electrode under V2O5 as bottom oxide remain stable after peeling-off and sustain a >50% uniaxial strain with a negligible reduction in luminance and current efficiencies. The surface energy and interface of the bottom oxide in the OMO structure are crucial for thin metals to attain superior optical, structural, electronic, and mechanical stability in SOLEDs.