Smooth and mechanically robust random metallic mesh electrode modified by thermally transferred PEDOT: PSS for ITO-Free flexible organic light-emitting diodes

Indium-tin-oxide (ITO)-free flexible organic light-emitting diodes (OLEDs) have attracted lots of interest because the flexible ITO is severely restricted by its brittleness and the scarceness of indium. Random metallic mesh (RM) is believed as a competitive alternative for flexible ITO due to its high conductivity, good transparency as well as low cost for scale production. However, the rough surface and the poor mechanical durability still limit the application of RM for flexible OLEDs. Here, we reported an RM-based flexible transparent conductive electrode (FTCE) using a thermally transferred PEDOT: PSS as a modification layer. The transferred PEDOT:PSS modified RM exhibits a low sheet resistance of 10.6 Ω sq⁻¹ with an 82.5% transmittance at 550 nm. The thermally transferring process realized an in-plane structure RM, leading to a smooth surface with root-mean-square roughness of 2.5 nm. Furthermore, benefiting the thermally transferring process-induced polymers interdiffusion at the PEDOT:PSS/PET interface, the PEDOT:PSS modified RM exhibits improved mechanical robustness, achieving a low relative resistance increment of 16.5% after 10⁵ times bending. An ITO-free flexible OLED was demonstrated by using the transferred PEDOT:PSS modified RM, exhibiting a good current efficiency of 54.7 cd/A, which is higher than that of the control device based on flexible ITO.