Kundu Kaushik, Acharyya Paribesh, Maji Krishnendu, Sasmal Ranjan, Agasti Sarit S, Biswas Kanishka
New Chemistry Unit and School of Advanced Materials, Bangalore, 560064, India.
Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Jakkur P.O., Bangalore, 560064, India.
Angew Chem Int Ed Engl. 2020 Jul 27;59(31):13093-13100. doi: 10.1002/anie.202005966. Epub 2020 Jul 7.
Two-dimensional (2D) lead-free halide perovskites have generated enormous perception in the field of optoelectronics due to their fascinating optical properties. However, an in-depth understanding on their shape-controlled charge-carrier recombination dynamics is still lacking, which could be resolved by exploring the photoluminescence (PL) blinking behaviour at the single-particle level. Herein, we demonstrate, for the first time, the synthesis of nanocrystals (NCs) and 2D nanosheets (NSs) of layered mixed halide, Cs Bi I Cl , by solution-based method. We applied fluorescence microscopy and super-resolution optical imaging at single-particle level to investigate their morphology-dependent PL properties. Narrow emission line widths and passivation of non-radiative defects were evidenced for 2D layered nanostructures, whereas the activation of shallow trap states was recognized at 77 K. Interestingly, individual NCs were found to display temporal intermittency (blinking) in PL emission. On the other hand, NS showed temporal PL intensity fluctuations within localized domains of the crystal. In addition, super-resolution optical image of the NS from localization-based method showed spatial inhomogeneity of the PL intensity within perovskite crystal.
二维（2D）无铅卤化物钙钛矿因其迷人的光学性质在光电子学领域引起了极大关注。然而，目前仍缺乏对其形状控制的电荷载流子复合动力学的深入理解，这可以通过在单粒子水平上探索光致发光（PL）闪烁行为来解决。在此，我们首次展示了通过溶液法合成层状混合卤化物CsBiICl的纳米晶体（NCs）和二维纳米片（NSs）。我们应用单粒子水平的荧光显微镜和超分辨率光学成像来研究它们的形态依赖的PL性质。二维层状纳米结构表现出窄发射线宽和非辐射缺陷的钝化，而在77K时可识别出浅陷阱态的激活。有趣的是，发现单个NCs在PL发射中表现出时间间歇性（闪烁）。另一方面，NS在晶体的局部区域内显示出时间PL强度波动。此外，基于定位方法的NS超分辨率光学图像显示了钙钛矿晶体内PL强度的空间不均匀性。
