Bi Chenghao, Wang Shixun, Kershaw Stephen V, Zheng Kaibo, Pullerits Tönu, Gaponenko Sergey, Tian Jianjun, Rogach Andrey L
Institute for Advanced Materials and Technology University of Science and Technology Beijing 100083 China.
Department of Materials Science and Engineering and Centre for Functional Photonics (CFP) City University of Hong Kong Kowloon Hong Kong S.A.R.
Adv Sci (Weinh). 2019 May 8;6(13):1900462. doi: 10.1002/advs.201900462. eCollection 2019 Jul 3.
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) 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.
胶体全无机钙钛矿纳米晶体因其优异的发光性能，作为一种有前途的材料在基础研究和应用研究中都受到了广泛关注。然而，报道的蓝色发光钙钛矿纳米晶体的光致发光量子产率（PL QYs）相当低，主要是因为这种宽带隙材料的高能激子很容易被带间陷阱捕获，然后以非辐射方式衰减。在这项工作中，展示了如何解决这个问题，即将二维钙钛矿纳米片自组装成更大尺寸（≈50 nm×50 nm×20 nm）的长方体晶体。在这些结构中，通过有机配体在长方体支架内彼此隔离的二维纳米片构成了多个量子阱，其中激子在潜在无序位点上的定位有助于它们绕过其他纳米片中存在的非辐射通道。结果，长方体晶体在以480 nm为中心的发射带中显示出91%的极高PL QY。此外，使用相同的合成方法，制备出了蓝色发射峰在452至470 nm范围内、PL QYs仍在72 - 83%范围内的混合阴离子CsPb(Br/Cl)长方体晶体。
