Long-range order enabled stability in quantum dot light-emitting diodes

Area of Science:

• Materials Science
• Nanotechnology
• Optoelectronics

Background:

• Perovskite quantum dot (QD) light-emitting diodes (LEDs) offer high external quantum efficiencies (EQEs) and narrowband emission.
• However, their limited operating lifetimes are attributed to poor long-range order in QD films, hindering carrier injection and stability.
• This instability necessitates high bias voltages for light emission.

Purpose of the Study:

• To develop a chemical treatment for improving the long-range order and conductivity of perovskite QD films.
• To enhance the operating stability and efficiency of perovskite QD-LEDs.
• To achieve record-low operating voltages for high-luminance red perovskite QD-LEDs.

Main Methods:

• A synergistic dual-ligand chemical treatment was applied to perovskite QD films.
• This involved using aniline hydroiodide for anion exchange and bromotrimethylsilane for size regulation and ligand removal.
• Characterization of film order, conductivity, and device performance.

Main Results:

• The chemical treatment increased the diffraction intensity of QD film repeating units threefold, indicating improved long-range order.
• Film conductivity increased 2.5-fold to 4 × 10^-4 S m^-1, the highest recorded for perovskite QDs.
• Red perovskite QD-LEDs achieved 1,000 cd m^-2 luminance at a record-low 2.8 V, with >20% EQE.
• Device operating stability improved 100-fold compared to previous red perovskite LEDs at >20% EQE.

Conclusions:

• Improved long-range order in perovskite QD films via chemical treatment enhances conductivity and charge transport.
• This leads to significantly improved performance and stability in perovskite QD-LEDs.
• The developed method offers a pathway to highly stable and efficient perovskite QD-LEDs for next-generation displays and lighting.