Ultralow Roll-Off Quantum Dot Light-Emitting Diodes Using Engineered Carrier Injection Layer

Zebing Liao; Kumar Mallem; Maksym F Prodanov; Chengbin Kang; Yiyang Gao; Jianxin Song; Valerii V Vashchenko; Abhishek K Srivastava

doi:10.1002/adma.202303950

Ultralow Roll-Off Quantum Dot Light-Emitting Diodes Using Engineered Carrier Injection Layer

Adv Mater. 2023 Nov;35(47):e2303950. doi: 10.1002/adma.202303950. Epub 2023 Oct 20.

Authors

Zebing Liao^{1

2}, Kumar Mallem^{1

2}, Maksym F Prodanov^{1

2}, Chengbin Kang^{1

2}, Yiyang Gao^{1

2}, Jianxin Song^{1

2}, Valerii V Vashchenko^{1

2}, Abhishek K Srivastava^{1

2}

Affiliations

¹ State Key Laboratory of Advanced Displays and Optoelectronics Technologies, Department of Electronics and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.
² Centre for Display Research, Department of Electronics and Computer Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

PMID: 37749922
DOI: 10.1002/adma.202303950

Abstract

Quantum dot (QD) light-emitting diodes (QLEDs) have attracted extensive attention due to their high color purity, solution-processability, and high brightness. Due to extensive efforts, the external quantum efficiency (EQE) of QLEDs has approached the theoretical limit. However, because of the efficiency roll-off, the high EQE can only be achieved at relatively low luminance, hindering their application in high-brightness devices such as near-to-eye displays and lighting applications. Here, this article reports an ultralow roll-off QLED that is achieved by simultaneously blocking electron leakage and enhancing the hole injection, thereby shifting the recombination zone back to the emitting QDs layer. These devices maintain EQE over 20.6% up to 1000 mA cm^-2 current density, dropping only by ≈5% from the peak EQE of 21.6%, which is the highest value ever reported for the bottom-emitting red QLEDs. Furthermore, the maximum luminance of the optimal device reaches 320 000 cd m^-2 , 2.7 times higher than the control device (L_max : 128 000 cd m^-2 ). A passive matrix (PM) QLED display panel with high brightness based on the optimized device structure is also demonstrated. The proposed approach advances the potential of QLEDs to operate efficiently in high-brightness scenarios.

Keywords: displays; hole transporting layers; light-emitting diodes; quantum dots; roll-off.

Abstract

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