Synthesis-on-substrate of quantum dot solids

• Published in: Nature (London) Vol. 612; no. 7941; pp. 679 - 684
• Main Authors: Jiang, Yuanzhi, Sun, Changjiu, Xu, Jian, Li, Saisai, Cui, Minghuan, Fu, Xinliang, Liu, Yuan, Liu, Yaqi, Wan, Haoyue, Wei, Keyu, Zhou, Tong, Zhang, Wei, Yang, Yingguo, Yang, Jien, Qin, Chaochao, Gao, Shuyan, Pan, Jun, Liu, Yufang, Hoogland, Sjoerd, Sargent, Edward H., Chen, Jun, Yuan, Mingjian
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 22.12.2022; Nature Publishing Group
• Subjects: 639/301/1005; 639/301/357/1017; 639/624/1020; Adsorption; Coupling; Crystallization; Electrostatic properties; Humanities and Social Sciences; Ligands; Light emitting diodes; multidisciplinary; Nanoparticles; Perovskites; Quantum confinement; Quantum dots; Quantum efficiency; Science; Science (multidisciplinary); Steric hindrance; Substrates; Synthesis
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-022-05486-3

Perovskite light-emitting diodes (PeLEDs) with an external quantum efficiency exceeding 20% have been achieved in both green and red wavelengths 1 – 5 ; however, the performance of blue-emitting PeLEDs lags behind 6 , 7 . Ultrasmall CsPbBr 3 quantum dots are promising candidates with which to realize efficient and stable blue PeLEDs, although it has proven challenging to synthesize a monodispersed population of ultrasmall CsPbBr 3 quantum dots, and difficult to retain their solution-phase properties when casting into solid films 8 . Here we report the direct synthesis-on-substrate of films of suitably coupled, monodispersed, ultrasmall perovskite QDs. We develop ligand structures that enable control over the quantum dots’ size, monodispersity and coupling during film-based synthesis. A head group (the side with higher electrostatic potential) on the ligand provides steric hindrance that suppresses the formation of layered perovskites. The tail (the side with lower electrostatic potential) is modified using halide substitution to increase the surface binding affinity, constraining resulting grains to sizes within the quantum confinement regime. The approach achieves high monodispersity (full-width at half-maximum = 23 nm with emission centred at 478 nm) united with strong coupling. We report as a result blue PeLEDs with an external quantum efficiency of 18% at 480 nm and 10% at 465 nm, to our knowledge the highest reported among perovskite blue LEDs by a factor of 1.5 and 2, respectively 6 , 7 . Ultrasmall monodisperse perovskite quantum dots are synthesized in situ on a substrate via ligand structure regulation, yielding the highest external quantum efficiency blue perovskite LEDs reported so far.