Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, Netherlands.
Small. 2011 Dec 16;7(24):3493-501. doi: 10.1002/smll.201101819. Epub 2011 Oct 21.
The optical properties of PbSe/CdSe core/shell quantum dots with core sizes smaller than 4 nm in the 5-300 K range are reported. The photoluminescence spectra show two peaks, which become increasingly separated in energy as the core diameter is reduced below 4 nm. It is shown that these peaks are due to intrinsic exciton transitions in each quantum dot, rather than emission from different quantum dot sub-ensembles. Most likely, the energy separation between the peaks is due to inter-valley coupling between the L-points of PbSe. The temperature dependence of the relative intensities of the peaks implies that the two emitting states are not in thermal equilibrium and that dark exciton states must play an important role.
本文报道了粒径小于 4nm 的 PbSe/CdSe 核壳量子点在 5-300K 温度范围内的光学性质。光致发光谱显示出两个峰，随着核直径减小到 4nm 以下，它们在能量上的分离越来越明显。结果表明，这些峰是由于每个量子点中的本征激子跃迁引起的，而不是来自不同量子点亚群的发射。很可能，峰之间的能量分离是由于 PbSe 的 L 点之间的谷间耦合引起的。峰的相对强度的温度依赖性表明，两个发射态不在热平衡中，暗激子态必须发挥重要作用。
