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 Ti₃C₂T_x 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.