Quantum-Dot Light-Emitting Diodes with Long Lifetime at High Brightness
huaibin shen a
a Key Laboratory for Special Functional Materials of Ministry of Education
nanoGe Perovskite Conferences
Proceedings of International online conference on Hybrid materials and optoelectronic devices (HYBRIDOE)
Online, Spain, 2020 December 15th - 17th
Organizers: Xueqing Xu, Baomin Xu, Hin-Lap (Angus) Yip and Xinhua Zhong
Invited Speaker, huaibin shen, presentation 025
DOI: https://doi.org/10.29363/nanoge.hybridoe.2020.025
Publication date: 4th December 2020

Quantum dot light-emitting diodes (QLEDs) have been considered to be the most potential candidate of light sources for applications in displays due to their potentials in good color saturation, high brightness, spectral tunability, and low processing cost. Recent advances in luminance and external quantum efficiency (EQE) and even operation lifetime of QLEDs have already satisfied the requirements for low-light-level displays (Indoor displays) . However, the short operation lifetime under high brightness and efficiency limits the application of QLEDs in outdoor displays and lightings. So far, the only work that has achieved the long lifetime under high brightness but low EQE is in red QLEDs, which have a T95 operation lifetime of more than 2300 h with an initial brightness of 1000 cd m−2. However, there have been no corresponding reports of green or blue ones. Compared with red quantum dots (QDs), green or blue ones have a larger band gap, which increases the energy barrier during carrier transport. This inherent nature, bringing the problems such as the electron-hole imbalance and heating in QLEDs, has become a major obstacle to fabricate green and blue QLEDs with long operation lifetime for high brightness applications.

In this talk, we will demonstrate that this obstacle of green QLEDs has been overcome. Specifically, we report a breakthrough discovery in green QLEDs, by achieving record long operation lifetime of T95 > 2500 h at 1000 cd m-2 simultaneously with record high EQE of 23.9% among all green QLEDs reported. We qualitatively attribute these major advances to the use of ZnCdSe/ZnSe/ZnSeS/ZnS core/shell QDs, which involves a compositional graded interlayer. The specially designed QDs are fabricated by using the approach of low-temperature core and high-temperature shell growth, exhibiting the high photoluminescence quantum yield (PL QY) of > 95%, high stability, single-exponential PL decay dynamics, and suppressed non-radiative Förster resonance energy transfer (FRET) and Auger recombination.

 

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