Department of Applied Chemistry for Environment, Kwansei Gakuin University, 1 Gakuen Uegahara, Sanda, Hyogo 669-1330, Japan.
J Phys Chem Lett. 2023 Mar 9;14(9):2441-2447. doi: 10.1021/acs.jpclett.3c00059. Epub 2023 Mar 2.
Emission photon statistics of semiconductor nanocrystal quantum dots (QDs), including lead halide perovskite nanocrystals (PNCs), are important fundamental and practical optical properties. Single QDs exhibit high-probability single-photon emission owing to the efficient Auger recombination between generated excitons. Because the recombination rate depends on QD size, single-photon emission probability should be size-dependent. Previous studies have researched QDs smaller than their exciton Bohr diameters (twice the Bohr radius of excitons). Here, we investigated the relationship between the single-photon emission behavior and size of CsPbBr PNCs to elucidate their size threshold. Simultaneous single-nanocrystal spectroscopy and atomic force microscopy observations on single PNCs with approximately 5-25 nm edge length showed that those smaller than approximately 10 nm, which had size-dependent photoluminescence (PL) spectral shifts, exhibited high-probability single-photon emissions, which decreased linearly with PNC volume. Novel single-photon emission, size, and PL peak correlations of PNCs are important for understanding the relationship between single-photon emission and quantum confinement.
半导体纳米晶量子点（QDs）的发射光子统计特性，包括卤化铅钙钛矿纳米晶（PNCs），是重要的基本和实际光学性质。由于激子产生的高效俄歇复合，单个 QD 表现出高概率的单光子发射。由于复合速率取决于 QD 的尺寸，因此单光子发射概率应该是尺寸依赖性的。以前的研究已经研究了小于激子玻尔直径（激子玻尔半径的两倍）的 QD。在这里，我们研究了单光子发射行为与 CsPbBr PNC 尺寸之间的关系，以阐明其尺寸阈值。通过对具有约 5-25nm 边缘长度的单个 PNC 进行同时单纳米晶体光谱学和原子力显微镜观测，我们发现那些小于约 10nm 的 PNC 具有尺寸依赖性的光致发光（PL）光谱位移，表现出高概率的单光子发射，其随 PNC 体积呈线性下降。PNC 的单光子发射、尺寸和 PL 峰的新关联对于理解单光子发射与量子限制之间的关系很重要。
