Highly Flexible Transparent Micromesh Electrodes via Blade-Coated Polymer Networks for Organic Light-Emitting Diodes

The availability of transparent conductive thin films that exhibit mechanical flexibility and are adapted to low-cost and large-area fabrication is a major obstacle for high-performance flexible thin-film optoelectronics. Here, by combining printing, thin-film deposition, and wet-etching processes, interconnected transparent metal micromesh (TMM) electrodes are reported. Blade-coating is used to generate self-assembled polymer micromesh networks on flexible substrates. The network structures are subsequently converted into conductive metal networks. As-fabricated TMM films display a surface roughness of around 20 nm with thickness down to 50 nm. A transmittance of 86% and a conductance of 80 Ω sq^-1 are achieved at the described optimal blade-coating suspension concentration. The electrodes show mechanical flexibility with no conductivity degradation with the smallest bending radius of 1 mm or at repeated bending over 3000 cycles at a bending radius of 15 mm. We successfully demonstrate organic light-emitting diodes (OLEDs) using TMM electrodes via the blade-coating technique. The printed OLEDs have a low turn-on voltage of 3.4 V and can achieve a luminance of over 4000 cd/m² at 6.5 V. At a luminance of 100 cd/m², the OLEDs show a current density of 7.6 mA/cm², an external quantum efficiency (EQE) of 3.6%, and a luminous efficacy of 1.4 lm/W.