Chenghao Bi,Shixun Wang,Stephen V. Kershaw,Kaibo Zheng,Tönu Pullerits,Sergey Gaponenko,Jianjun Tian,Andrey L. Rogach
Colloidal all-inorganic perovskite nanocrystals have gained significant attention as a promising material for both fundamental and applied research due to their excellent emission properties. However, reported photoluminescence quantum yields (PL QYs) of blue-emitting perovskite nanocrystals are rather low, mostly due to the fact that the high energy excitons for such wide bandgap materials are easily captured by interband traps, and then decay nonradiatively. In this work, it is demonstrated how to tackle this issue, performing self-assembly of 2D perovskite nanoplatelets into larger size (≈50 nm × 50 nm × 20 nm) cuboid crystals. In these structures, 2D nanoplatelets being isolated from each other within the cuboidal scaffold by organic ligands constitute multiple quantum wells, where exciton localization on potential disorder sites helps them to bypass nonradiative channels present in other platelets. As a result, the cuboid crystals show an extremely high PL QY of 91% of the emission band centered at 480 nm. Moreover, using the same synthetic method, mixed-anion CsPb(Br/Cl) 3 cuboid crystals with blue emission peaks ranging from 452 to 470 nm, and still high PL QYs in the range of 72–83% are produced.
CsPbX 3 (X = Cl, Br, I) nanocrystals (NCs) are competitive materials for a wide range of applications because of their outstanding optoelectronic properties. Ion doping has been demonstrated as one powerful method for improving the optical properties of CsPbX 3 NCs. However, the conventional ion-doping approaches are tedious, and generally performed under an inert atmosphere and high temperature. In this work, a one-step ultrasonic-assisted approach is demonstrated to prepare doped CsPbX 3 NCs. To demonstrate the universality of the ultrasonic-assisted ion-doping approach, three ion-doped perovskite NCs are prepared, which represent three common improvements effects of ion doping on perovskite NCs, namely improved stability, PL emission, and photoluminescence quantum yields (PLQYs) of perovskite NCs. Sr-doped CsPbI 3 NCs showed improved phase stability. Mn-doped CsPbCl 3 NCs showed dual-color emissions at 406 and 580 nm. The PLQYs of the as-prepared Ni-doped CsPbCl 3 NCs are greatly improved, from 10.1% to 71%. Such a simple and versatile ion-doping approach may promote the practical applications of all-inorganic perovskite NCs.
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