Issue 25, 2022

Cu substitution boosts self-trapped exciton emission in zinc-based metal halides for sky-blue light-emitting diodes

Abstract

Substantial progress has been made in light-emitting diodes (LEDs) based on red- and green-emitting lead halides. However, reducing the lead toxicity of emissive materials and achieving high-efficiency blue-emitting LED beads on lead-free metal halides remains a great challenge. Herein, lead-free zero-dimensional metal halides Cu:(PEA)2ZnX4 (X = Cl, Br) were developed to solve the above bottlenecks. Cu substitution enhanced the photoluminescence quantum yield (PLQY) of (PEA)2ZnBr4 from 3.4% to 55% and that of (PEA)2ZnCl4 from 2.7% to 34.5%. Interestingly, dual emission peaks are observed at low temperatures due to the presence of two excitation structures on the potential energy surface of the triplet state excited states. The self-trapped excitons of Cu:(PEA)2ZnBr4 can cross this potential barrier between the two triplet-state excited states by acquiring thermal energy, but Cu:(PEA)2ZnCl4 cannot overcome the barrier due to the different molecular environments. For the first time, using Cu:(PEA)2ZnX4 as the light-emitting layers, sky-blue LEDs with an external quantum efficiency (EQE) of 0.45% and 0.83% for Cu:(PEA)2ZnCl4 and Cu:(PEA)2ZnBr4 were obtained, demonstrating that broadband light-emitting lead-free metal halides have great potential for sky-blue light-emitting diode applications.

Graphical abstract: Cu substitution boosts self-trapped exciton emission in zinc-based metal halides for sky-blue light-emitting diodes

Supplementary files

Article information

Article type
Paper
Submitted
21 Apr 2022
Accepted
23 May 2022
First published
25 May 2022

J. Mater. Chem. C, 2022,10, 9530-9537

Cu substitution boosts self-trapped exciton emission in zinc-based metal halides for sky-blue light-emitting diodes

M. Ren, S. Zhang, T. Chang, J. Yao, Y. Gao, M. Yuan, S. Cao, J. Zhao, B. Zou and R. Zeng, J. Mater. Chem. C, 2022, 10, 9530 DOI: 10.1039/D2TC01637K

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