Flexible CdSe/ZnS Quantum-Dot Light-Emitting Diodes with Higher Efficiency than Rigid Devices

Fabrication of high-performance, flexible quantum-dot light-emitting diodes (QLEDs) requires the reliable manufacture of a flexible transparent electrode to replace the conventional brittle indium tin oxide (ITO) transparent electrode, along with flexible substrate planarization. We deposited a transparent oxide/metal/oxide (OMO) electrode on a polymer planarization layer and co-optimized both layers. The visible transmittance of the OMO electrode on a polyethylene terephthalate substrate increased markedly. Good electron supply and injection into an electron-transporting layer were achieved using WO_X/Ag/ WO_X and MoOx/Ag/MoO_X OMO electrodes. High-performance flexible QLEDs were fabricated from these electrodes; a QLED with a MoO_X/Ag/ MoO_X cathode and an SU-8 planarization layer had a current efficiency of 30.3 cd/A and luminance more than 7 × 10⁴ cd/m². The current efficiency was significantly higher than that of a rigid QLED with an ITO cathode and was higher than current efficiency values obtained from previously reported QLEDs that utilized the same quantum-dot and electron-transporting layer materials as our study.