Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60628-3113, United States.
ACS Nano. 2011 Mar 22;5(3):2026-35. doi: 10.1021/nn2002689. Epub 2011 Mar 1.
A combination of transient absorption (TA) and time-resolved photoluminescence (TRPL) spectroscopies performed on solution-phase samples of colloidal CdSe quantum dots (QDs) allows the construction of a time-resolved, charge carrier-resolved map of decay from the first excitonic state of the QD. Data from TA and TRPL yield the same six exponential components, with time constants ranging from ∼1 ps to 50 ns, for excitonic decay. Comparison of TA signals in the visible and near-infrared (NIR) spectral regions enables determination of the relative contributions of electron and hole dynamics to each decay component, and comparison of TA and TRPL reveals that each component represents a competition between radiative and nonradiative decay pathways. In total, these data suggest that the QD sample comprises at least three distinct populations that differ in both the radiative and nonradiative decay pathways available to the excitonic charge carriers, and provide evidence for multiple emissive excitonic states in which the hole is not in the valence band, but rather a relaxed or trapped state.
对胶体 CdSe 量子点 (QD) 的溶液相样品进行瞬态吸收 (TA) 和时间分辨光致发光 (TRPL) 光谱学的组合，允许构建来自 QD 的第一激子态的衰减的时间分辨、载流子分辨的图谱。来自 TA 和 TRPL 的数据对于激子衰减产生相同的六个指数分量，时间常数范围从约 1 ps 到 50 ns。可见和近红外 (NIR) 光谱区域中的 TA 信号的比较能够确定电子和空穴动力学对每个衰减分量的相对贡献，并且 TA 和 TRPL 的比较表明每个分量代表辐射和非辐射衰减途径之间的竞争。总的来说，这些数据表明，QD 样品至少包含三种不同的群体，它们在激子载流子可用的辐射和非辐射衰减途径方面存在差异，并为多个发射激子态提供了证据，其中空穴不在价带中，而是处于弛豫或俘获状态。
