Folie Brendan D, Tan Jenna A, Huang Jianmei, Sercel Peter C, Delor Milan, Lai Minliang, Lyons John L, Bernstein Noam, Efros Alexander L, Yang Peidong, Ginsberg Naomi S
Department of Applied Physics and Materials Science, California Institute of Technology, Pasadena California 91125, United States.
Center for Computational Material Science, Naval Research Laboratory, Washington D.C. 20375, United States.
J Phys Chem A. 2020 Mar 5;124(9):1867-1876. doi: 10.1021/acs.jpca.9b11981. Epub 2020 Feb 25.
Inorganic lead halide perovskite nanostructures show promise as the active layers in photovoltaics, light emitting diodes, and other optoelectronic devices. They are robust in the presence of oxygen and water, and the electronic structure and dynamics of these nanostructures can be tuned through quantum confinement. Here we create aligned bundles of CsPbBr nanowires with widths resulting in quantum confinement of the electronic wave functions and subject them to ultrafast microscopy. We directly image rapid one-dimensional exciton diffusion along the nanowires, and we measure an exciton trap density of roughly one per nanowire. Using transient absorption microscopy, we observe a polarization-dependent splitting of the band edge exciton line, and from the polarized fluorescence of nanowires in solution, we determine that the exciton transition dipole moments are anisotropic in strength. Our observations are consistent with a model in which splitting is driven by shape anisotropy in conjunction with long-range exchange.
无机卤化铅钙钛矿纳米结构有望成为光伏、发光二极管及其他光电器件的活性层。它们在有氧和水的环境中很稳定，并且这些纳米结构的电子结构和动力学可通过量子限域进行调控。在此，我们制备了宽度能导致电子波函数量子限域的CsPbBr纳米线排列束，并对其进行超快显微镜观察。我们直接成像了激子沿纳米线的快速一维扩散，且测得每条纳米线的激子陷阱密度约为一个。利用瞬态吸收显微镜，我们观察到带边激子线的偏振依赖性分裂，并且从溶液中纳米线的偏振荧光，我们确定激子跃迁偶极矩在强度上是各向异性的。我们的观察结果与一个模型相符，在该模型中，分裂是由形状各向异性与长程交换共同驱动的。
