MXene/AgNWs/MXene Sandwich-Structured Transparent Electrode for High-Performance Flexible OLEDs.

Herein, sandwich-structured hybrid flexible transparent conductive electrodes (FTCEs), implemented by sandwiching silver nanowire (AgNWs) networks between 2D Ti3C2Tx MXene layers and applying pressure treatment is proposed. The synergistic effect of MXene flakes and mechanical pressure promotes efficient welding of wire-to-wire junctions, resulting in a flexible electrode with a low sheet resistance of 20.5 Ω sq-1 and a high transmittance of 92.3%. Thanks to strong hydrogen bonding interactions between MXene layers and the PET substrate, combined with effective embedding of AgNWs into the substrate, the pressure-treated MXene/AgNWs/MXene FTCE exhibits outstanding thermal stability, remarkable mechanical durability, and chemical stability (Sheet resistance only slightly changes after annealed at 160 °C for 3.5 h or 1000 bending tests). As a consequence, the resulting sandwich-structured FTCE-based green phosphorescent organic light-emitting diode (OLED) achieves state-of-the-art electroluminescence performance with a maximum external quantum efficiency (EQE) of 22.9% and a current efficiency of 81.4 cd A-1, which is significantly higher than those of ITO-based reference device. Most interestingly, the flexible red OLED demonstrates an EQE reaching 24.6%, extremely small efficiency roll-off (23.1% at 2144 cd m-2), and a large-area 25 × 25 mm2 panel with uniform light emission, which represents the best performance reported to date for flexible red-wavelength OLEDs.