Direct-write ultrathin Ag-mesh transparent electrodes by the Chinese brush for high-performance stretchable OLEDs

Flexible optoelectronic devices play a crucial role in the field of wearable electronics. However, their potential and development have been hindered by the lack of high-performance and durable flexible transparent electrodes. Here, we developed ultrathin Ag mesh electrodes using a direct writing technique by a Chinese brush. Through precise control over the writing process, the printed Ag mesh with an ultrathin thickness of ~100 nm and a high width resolution of ~20 µm was achieved. The resulted composite electrodes of Norland Optical Adhesive 63 (NOA63)/Ag mesh/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) possess a low sheet resistance of ~12 Ω/sq and a high transmittance of ~91%. Benefiting from the ultrathin Ag mesh and embedded structure, the composite electrode shows the quite low surface roughness (~0.9 nm), along with exceptional mechanical flexibility with a micrometer-scale bending radius. Furthermore, stretchable organic light-emitting devices (OLEDs) based on this composite electrode present an impressive current efficiency of 88.6 cd/A. Significantly, the OLEDs remain 86% initial current efficiency over 1000 bending cycles, and maintain 88% initial luminance at the 50% strain. Interestingly, this direct writing technique possesses the remarkable capability to print transparent electrodes on curved or uneven substrate surfaces, expanding its potential for universal applications. This work presents a straightforward and general printing method for constructing high-performance flexible transparent electrodes for various flexible electronics.