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

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Flexible quantum-dot light-emitting diodes (QLEDs) require alternatives to brittle indium tin oxide (ITO) transparent electrodes.
• Flexible substrate planarization is crucial for fabricating high-performance flexible QLEDs.

Purpose of the Study:

• To develop and optimize a flexible transparent electrode for high-performance flexible QLEDs.
• To investigate the performance of oxide/metal/oxide (OMO) electrodes on polymer planarization layers.

Main Methods:

• Fabrication of transparent oxide/metal/oxide (OMO) electrodes on polymer planarization layers.
• Co-optimization of OMO electrode and polymer planarization layers (e.g., SU-8).
• Characterization of electrode transmittance, electron supply, and injection properties.
• Integration of OMO electrodes into flexible QLED devices.

Main Results:

• Significantly increased visible transmittance of OMO electrodes on polyethylene terephthalate substrates.
• WO_X/Ag/WO_X and MoO_X/Ag/MoO_X OMO electrodes demonstrated good electron supply and injection.
• Flexible QLEDs fabricated with MoO_X/Ag/MoO_X cathodes achieved a current efficiency of 30.3 cd/A and luminance > 7 × 10⁴ cd/m².
• Achieved higher current efficiency compared to rigid QLEDs with ITO cathodes and previously reported flexible QLEDs using similar materials.

Conclusions:

• The developed OMO electrodes are effective replacements for ITO in flexible QLEDs.
• The MoO_X/Ag/MoO_X electrode combined with an SU-8 planarization layer enables high-performance flexible QLED fabrication.
• This approach offers a promising pathway for advanced flexible optoelectronic devices.