Nandan Yashaswi, Mehata Mohan Singh
Laser-Spectroscopy Laboratory, Department of Applied Physics, Delhi Technological University, Bawana Road, Delhi, 110042, India.
Sci Rep. 2019 Jan 9;9(1):2. doi: 10.1038/s41598-018-37676-3.
Nanostructured semiconductors have the unique shape/size-dependent band gap tunability, which has various applications. The quantum confinement effect allows controlling the spatial distribution of the charge carriers in the core-shell quantum dots (QDs). Upon increasing shell thickness (e.g., from 0.25-3.25 nm) of core-shell QDs, the radial distribution function (RDF) of hole shifts towards the shell suggesting the confinement region switched from Type-I to Type-II excitons. As a result, there is a jump in the transition energy towards the higher side (blue shift). However, an intermediate state appeared as pseudo Type II excitons, in which holes are co-localized in the shell as well core whereas electrons are confined in core only, resulting in a dual absorption band (excitation energy), carried out by the analysis of the overlap percentage using the Hartree-Fock method. The findings are a close approximation to the experimental evidences. Thus, the understanding of the motion of e-h in core-shell QDs is essential for photovoltaic, LEDs, etc.
纳米结构半导体具有独特的形状/尺寸依赖性带隙可调性，具有多种应用。量子限制效应允许控制核壳量子点（QD）中电荷载流子的空间分布。随着核壳量子点壳层厚度的增加（例如，从0.25 - 3.25nm），空穴的径向分布函数（RDF）向壳层移动，表明限制区域从I型激子转变为II型激子。结果，跃迁能量向更高侧跳跃（蓝移）。然而，出现了一种作为准II型激子的中间态，其中空穴在壳层和核中都共定位，而电子仅限制在核中，通过使用哈特里 - 福克方法分析重叠百分比得出了双吸收带（激发能）。这些发现与实验证据非常接近。因此，理解核壳量子点中电子 - 空穴的运动对于光伏、发光二极管等至关重要。
