Highly Stable and Efficient Light-Emitting Diodes Based on Orthorhombic γ-CsPbI3 Nanocrystals

Jie Guo; Min Lu; Xiaoyu Zhang; Siqi Sun; Ce Han; Yu Zhang; Xuyong Yang; Stephen V Kershaw; Weitao Zheng; Andrey L Rogach

doi:10.1021/acsnano.3c00789

Highly Stable and Efficient Light-Emitting Diodes Based on Orthorhombic γ-CsPbI₃ Nanocrystals

ACS Nano. 2023 May 23;17(10):9290-9301. doi: 10.1021/acsnano.3c00789. Epub 2023 May 1.

Authors

Jie Guo¹, Min Lu², Xiaoyu Zhang¹, Siqi Sun², Ce Han¹, Yu Zhang², Xuyong Yang³, Stephen V Kershaw⁴, Weitao Zheng¹, Andrey L Rogach⁴

Affiliations

¹ Key Laboratory of Automobile Materials MOE, School of Materials Science & Engineering, and Jilin Provincial International Cooperation Key Laboratory of High-Efficiency Clean Energy Materials, Jilin University, Changchun 130012, People's Republic of China.
² State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, People's Republic of China.
³ Key Laboratory of Advanced Display and System Applications of Ministry of Education, Shanghai University, Shanghai 200072, People's Republic of China.
⁴ Department of Materials Science and Engineering and Centre for Functional Photonics (CFP), City University of Hong Kong, Hong Kong SAR 999077, People's Republic of China.

PMID: 37126487
DOI: 10.1021/acsnano.3c00789

Abstract

Orthorhombic γ-CsPbI₃ possesses the highest structural stability among the optically active (light-emissive) CsPbI₃ perovskites. Here, we make use of a seed-assisted heteroepitaxial growth to fabricate seed/core/shell CaI_x/γ-CsPbI₃/CaI₂ nanocrystals. Ultrasmall CaI_x nanoparticles serve as seeds to template the Pb-centered octahedral arrangement which enables the formation of the γ-CsPbI₃ phase and at the same time inhibit lattice strain by blocking the force transfer that otherwise leads to an octahedral twist and so improve the structural stability of the resulting nanocrystals. An outer shell composed from the same material, CaI₂, isolates the formed γ-CsPbI₃ nanocrystals from the environment, which also significantly improves their stability under ambient conditions. Optical and electrical studies indicate that the seed/core/shell CaI_x/γ-CsPbI₃/CaI₂ structure possesses a shallower set of trap states as compared to cubic α-CsPbI₃ nanocrystals. Light-emitting diodes utilizing these γ-CsPbI₃ nanocrystals show a record high external quantum efficiency of 25.3%, high brightness of over 13600 cd/m², and an operational lifetime of ∼14 h before reaching 50% of their initial luminance. These devices can repeatedly be illuminated over 650 times at ∼500 cd/m² with no decline of brightness, which indicates their great commercial potential.

Keywords: CaI2 nanoparticles; core; light-emitting diode; orthorhombic γ-CsPbI3 phase; seed; shell nanostructure; stable light-emitting devices.