Efficient and long-lifetime full-color light-emitting diodes using high luminescence quantum yield thick-shell...

Area of Science:

• Materials Science
• Optoelectronics
• Nanotechnology

Background:

• Quantum dots (QDs) are crucial for advanced display technologies.
• Improving the efficiency and stability of QD-based light-emitting diodes (QLEDs) is an ongoing challenge.
• Core/shell QD structures offer enhanced optical properties but require further optimization for practical applications.

Purpose of the Study:

• To develop high-performance, full-color quantum-dot light-emitting diodes (QLEDs).
• To investigate the impact of QD shell thickness on device efficiency and operational lifetime.
• To achieve high external quantum efficiencies (EQEs) and prolonged stability in QLEDs.

Main Methods:

• Fabrication of core/shell quantum dots with significantly increased shell thicknesses (above 5 nm).
• Optimization of the QD emitting layer thickness and hole transport layer (HTL) materials.
• Characterization of QLED performance, including current efficiency, EQE, and operational lifetime (T70) across different colors (red, green, blue).

Main Results:

• QLEDs with thick-shell QDs demonstrated high current efficiencies (up to 53.4 cd A⁻¹) and peak EQEs (up to 15.6% for blue).
• Blue QLEDs achieved a record EQE exceeding 15%, with performance maintained over a wide luminance range (10²–10⁴ cd m⁻²).
• Devices exhibited extended operational lifetimes, with T70 values of 117 h (red), 84 h (green), and 47 h (blue).

Conclusions:

• Increased QD shell thickness effectively suppresses Auger recombination and Förster resonant energy transfer, enhancing device performance.
• Thick-shell QDs are a promising material for realizing next-generation full-color displays and lighting with high efficiency and long lifetimes.
• The developed QLEDs show significant potential for commercial applications due to their improved efficiency and stability.