Park Young-Shin, Lim Jaehoon, Klimov Victor I
Chemistry Division, Los Alamos National Laboratory, Los Alamos, NM, USA.
Centre for High Technology Materials, University of New Mexico, Albuquerque, NM, USA.
Nat Mater. 2019 Mar;18(3):249-255. doi: 10.1038/s41563-018-0254-7. Epub 2019 Jan 7.
The application of colloidal semiconductor quantum dots as single-dot light sources still requires several challenges to be overcome. Recently, there has been considerable progress in suppressing intensity fluctuations (blinking) by encapsulating an emitting core in a thick protective shell. However, these nanostructures still show considerable fluctuations in both emission energy and linewidth. Here we demonstrate type-I core/shell heterostructures that overcome these deficiencies. They are made by combining wurtzite semiconductors with a large, directionally anisotropic lattice mismatch, which results in strong asymmetric compression of the emitting core. This modifies the structure of band-edge excitonic states and leads to accelerated radiative decay, reduced exciton-phonon interactions, and suppressed coupling to the fluctuating electrostatic environment. As a result, individual asymmetrically strained dots exhibit highly stable emission energy (<1 meV standard deviation) and a subthermal room-temperature linewidth (~20 meV), concurrent with nearly nonblinking behaviour, high emission quantum yields, and a widely tunable emission colour.
将胶体半导体量子点用作单量子点光源仍需克服若干挑战。最近，通过在厚保护壳中封装发光核心，在抑制强度波动（闪烁）方面取得了显著进展。然而，这些纳米结构在发射能量和线宽方面仍表现出相当大的波动。在此，我们展示了克服这些缺陷的I型核/壳异质结构。它们是通过将具有大的、方向各向异性晶格失配的纤锌矿半导体组合而成的，这导致发光核心受到强烈的不对称压缩。这改变了带边激子态的结构，导致辐射衰减加速、激子 - 声子相互作用减少，并抑制了与波动静电环境的耦合。结果，单个不对称应变量子点表现出高度稳定的发射能量（标准偏差<1 meV）和亚热室温线宽（~20 meV），同时具有几乎不闪烁的行为、高发射量子产率和广泛可调的发射颜色。
