Photo-activated luminescence of CdSe quantum dot monolayers
Photo-activated luminescence of CdSe quantum dot monolayers
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DOI：
10.1021/jp001771s
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发表时间：
2000-12-28
影响因子：
3.3
通讯作者：
Buratto, SK
中科院分区：
文献类型：
--
作者：
Cordero, SR;Carson, PJ;Buratto, SK
我们表明，CdSe 量子点单层的发光会受到表面吸附的水分子相互作用的强烈影响。吸收水后光引起的表面态变化导致量子点发生准可逆的发光变化。在空气中（真空后）照明的前 200 秒内，激子 QY 增加了 20 倍，然后在 5000 秒后稳定下降至真空参考值的 6 倍。在 1 小时的照射下，激子发射呈现出近 16 nm (60 meV) 的指数蓝移。在此期间，线宽在前 100 秒内减小 10%，然后在 5000 秒后缓慢增加至真空参考线宽的 96%。我们的模型表明，吸附在量子点表面的水分子会钝化表面陷阱，从而导致发光增加，类似于大块 CdSe 表面众所周知的效应。此外，吸附的水分子会氧化量子点的表面，导致激子发射蓝移，最终引入新的表面缺陷，从而降低发光。正是这两个过程之间的竞争导致了发光 QY 的复杂动力学。
We show that the luminescence from CdSe quantum dot monolayers can be strongly influenced by the interaction of water molecules adsorbed on the surface. Light-induced alterations in the surface states following adsorption of water, results in quasi-reversible luminescence changes in che quantum dot. The excitonic QY increases by a factor of 20 during the first 200 s Of illumination in air (post vacuum) and then steadily decreases to a level 6 times that of the vacuum reference after 5000 s. The exciton emission exhibits an exponential blue shift of nearly 16 nm (60 meV) over 1 h of illumination. During this time, the line width decreases by 10% during the first 100 s and then slowly increases to 96% of the vacuum reference line width after 5000 s. Our model suggests that water molecules adsorbed on the surface of the quantum dot act to passivate surface traps, which results in increased luminescence, similar to an effect well-known for bulk CdSe surfaces. In addition, adsorbed water molecules act to oxidize the surface of the quantum dot, which results in the blue shift of the exciton emission and eventually introduces new surface defects that lower the luminescence. It is the competition between these two processes that is responsible for the complex kinetics of the luminescence QY.