Bera Suman, Tripathi Akash, Titus Timi, Sethi Nilesh Monohar, Das Rajdeep, Adarsh K V, Thomas K George, Pradhan Narayan
School of Materials Sciences, Indian Association for the Cultivation of Science, Kolkata, West Bengal 700032, India.
Department of Physics, Indian Institute of Science Education and Research, Bhopal, Madhya Pradesh 462066, India.
J Am Chem Soc. 2024 Jul 24;146(29):20300-20311. doi: 10.1021/jacs.4c05803. Epub 2024 Jul 15.
Lead halide perovskite nanocrystals have been extensively studied in recent years as efficient optical materials for their bright and color-tunable emissions. However, these are mostly confined to their 3D nanocrystals and limited to the anisotropic nanostructures. By exploring the Cs-sublattice-induced metal(II) ion exchange with Pb(II), crack CsPbBr perovskite platelet nanocrystals having polar surfaces in all three directions are reported here, which remained different than reported standard square platelets. The crack platelets are also passivated with halides to enhance their brightness. Further, as these crack and passivated crack platelets have defects and polar surfaces, the exciton and biexciton generation in these platelets is investigated using femtosecond photoluminescence and transient absorption measurement at ambient as well as cryogenic temperatures, correlated with time-resolved single-particle photoluminescence spectroscopy, and compared with standard square platelets having nonpolar facets. These investigations revealed that the crack platelets and passivated crack platelets possess enhanced biexciton emission compared to square platelets due to the presence of polar surfaces in all three directions. These results provide insights into not only the design of the anisotropic nanostructures of ionic nanocrystals but also the possibility of tuning the single exciton to biexciton generation efficiency, which has potential applications in optoelectronic systems.
近年来，卤化铅钙钛矿纳米晶体作为高效光学材料因其明亮且可颜色调谐的发射而受到广泛研究。然而，这些大多局限于其三维纳米晶体且限于各向异性纳米结构。通过探索铯亚晶格诱导的金属（II）离子与铅（II）的交换，本文报道了在所有三个方向上具有极性表面的裂纹状CsPbBr钙钛矿片状纳米晶体，其与报道的标准方形片状晶体不同。裂纹片状晶体也用卤化物进行了钝化处理以提高其亮度。此外，由于这些裂纹和钝化的裂纹片状晶体具有缺陷和极性表面，利用飞秒光致发光和在环境温度以及低温下的瞬态吸收测量，并结合时间分辨单粒子光致发光光谱，研究了这些片状晶体中的激子和双激子产生，并与具有非极性晶面的标准方形片状晶体进行了比较。这些研究表明由于在所有三个方向上都存在极性表面，裂纹片状晶体和钝化的裂纹片状晶体与方形片状晶体相比具有增强的双激子发射。这些结果不仅为离子纳米晶体各向异性纳米结构的设计提供了见解，也为调节单激子到双激子产生效率的可能性提供了见解，这在光电子系统中具有潜在应用。
