Unravelling Alkali-Metal-Assisted Domain Distribution of Quasi-2D Perovskites for Cascade Energy Transfer toward Efficient Blue Light-Emitting Diodes

Wanqing Cai; Muhammad Umair Ali; Ping Liu; Miao He; Cong Zhao; Ziming Chen; Yue Zang; Man-Chung Tang; Hong Meng; Hongyan Fu; Guodan Wei; Hin-Lap Yip

doi:10.1002/advs.202200393

Unravelling Alkali-Metal-Assisted Domain Distribution of Quasi-2D Perovskites for Cascade Energy Transfer toward Efficient Blue Light-Emitting Diodes

Adv Sci (Weinh). 2022 Jul;9(20):e2200393. doi: 10.1002/advs.202200393. Epub 2022 May 13.

Authors

Wanqing Cai^{1

2}, Muhammad Umair Ali^{1

2}, Ping Liu^{1

2}, Miao He^{1

2}, Cong Zhao^{1

2}, Ziming Chen³, Yue Zang³, Man-Chung Tang^{1

2}, Hong Meng⁴, Hongyan Fu^{1

2}, Guodan Wei^{1

2}, Hin-Lap Yip^{3

5

6}

Affiliations

¹ Tsinghua-Berkeley Shenzhen Institute (TBSI), Tsinghua University, Shenzhen, 518055, China.
² Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen City, 518055, China.
³ State Key Laboratory of Luminescent Materials and Devices, Institute of Polymer Optoelectronic Materials and Devices, School of Materials Science and Engineering, South China University of Technology, 381 Wushan Road, Guangzhou, 510640, P. R. China.
⁴ School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen City, 518055, P. R. China.
⁵ Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, 999077, Hong Kong.
⁶ School of Energy and Environment, City University of Hong Kong, Kowloon, 999077, Hong Kong.

Abstract

Solution processable quasi-2D (Q-2D) perovskite materials are emerging as a promising candidate for blue light source in full-color display applications due to their good color saturation property, high brightness, and spectral tunability. Herein, an efficient energy cascade channel is developed by introducing sodium bromide (NaBr) in phenyl-butylammonium (PBA)-containing mixed-halide Q-2D perovskites for a blue perovskite light-emitting diode (PeLED). The incorporation of alkali metal contributes to the nucleation and growth of Q-2D perovskites into graded distribution of domains with different layer number <n>. The study of excitation dynamics by transient absorption (TA) spectroscopy confirms that NaBr induces more Q-2D perovskite phases with small n number, providing a graded energy cascade pathway to facilitate more efficient energy transfer processes. In addition, the nonradiative recombination within the Q-2D perovskites is significantly suppressed upon Na⁺ incorporation, as validated by the trap density estimation. Consequently, the optimized blue PeLEDs manifest a peak external quantum efficiency (EQE) of 7.0% emitting at 486 nm with a maximum luminance of 1699 cd m^-2 . It is anticipated that these findings will improve the understanding of alkali-metal-assisted optimization of Q-2D perovskites and pave the way toward high-performance blue PeLEDs.

Keywords: alkali metal halide; domain distribution; perovskite light-emitting diode; quasi-2D perovskite.

Abstract

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