Long-range order enabled stability in quantum dot light-emitting diodes

• Published in: Nature (London) Vol. 629; no. 8012; pp. 586 - 591
• Main Authors: Wang, Ya-Kun, Wan, Haoyue, Teale, Sam, Grater, Luke, Zhao, Feng, Zhang, Zhongda, Duan, Hong-Wei, Imran, Muhammad, Wang, Sui-Dong, Hoogland, Sjoerd, Liao, Liang-Sheng
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16.05.2024; Nature Publishing Group
• Subjects: 639/925/357/1017; 639/925/927/1007; Acids; Aniline; Anion exchange; Anion exchanging; Calcium Compounds - chemistry; Carrier injection; Charge transport; Chemical treatment; Conductivity; Electric Conductivity; Humanities and Social Sciences; Ligands; Light; Light emitting diodes; Long range order; Low voltage; Luminance; multidisciplinary; Narrowband; Oxides - chemistry; Perovskites; Quantum dots; Quantum Dots - chemistry; Quantum efficiency; Science; Science (multidisciplinary); Semiconductors; Stability; Titanium - chemistry
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-024-07363-7

Light-emitting diodes (LEDs) based on perovskite quantum dots (QDs) have produced external quantum efficiencies (EQEs) of more than 25% with narrowband emission 1 , 2 , but these LEDs have limited operating lifetimes. We posit that poor long-range ordering in perovskite QD films—variations in dot size, surface ligand density and dot-to-dot stacking—inhibits carrier injection, resulting in inferior operating stability because of the large bias required to produce emission in these LEDs. Here we report a chemical treatment to improve the long-range order of perovskite QD films: the diffraction intensity from the repeating QD units increases three-fold compared with that of controls. We achieve this using a synergistic dual-ligand approach: an iodide-rich agent (aniline hydroiodide) for anion exchange and a chemically reactive agent (bromotrimethylsilane) that produces a strong acid that in situ dissolves smaller QDs to regulate size and more effectively removes less conductive ligands to enable compact, uniform and defect-free films. These films exhibit high conductivity (4 × 10 −4  S m −1 ), which is 2.5-fold higher than that of the control, and represents the highest conductivity recorded so far among perovskite QDs. The high conductivity ensures efficient charge transportation, enabling red perovskite QD-LEDs that generate a luminance of 1,000 cd m −2 at a record-low voltage of 2.8 V. The EQE at this luminance is more than 20%. Furthermore, the stability of the operating device is 100 times better than previous red perovskite LEDs at EQEs of more than 20%. Improving the long-range order of the quantum dots in perovskite LEDs can markedly enhance their operational stability.