Triplet Sensitization by "Self-Trapped" Excitons of Nontoxic CuInS2 Nanocrystals for Efficient Photon Upconversion
Triplet Sensitization by "Self-Trapped" Excitons of Nontoxic CuInS2 Nanocrystals for Efficient Photon Upconversion
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DOI：
10.1021/jacs.9b07033
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发表时间：
2019-08-21
影响因子：
15
通讯作者：
Wu, Kaifeng
中科院分区：
文献类型：
--
作者：
Han, Yaoyao;He, Shan;Wu, Kaifeng
半导体纳米晶体（NCs）的三重态能量转移（TET）最近成为一种新的三重态敏化范式。目前尚不清楚NCs中普遍存在的阱态如何影响TET，也不清楚被捕获的激子是否能进行有效的TET。在这里，我们通过研究来自CuInS2 NCs的TET作为模型系统来部分解决这个问题，因为它们的光生激子已知是由于空穴定位到隙内Cu态而“自捕获”的。我们发现，由于自捕获激子的长寿命（209 +/- 17 ns），尽管TET速率相对较慢（57.1 +/- 1.7 mu s(-1)），但表面锚定蒽可以以接近92.3%的效率提取它们。我们进一步利用这种高效的敏化实现了三重态-三重态湮灭光子上转换（TTA-UC），量子产率为18.6 +/- 0.3%。因此，这项研究不仅证明了捕获的激子也可以进行有效的TET，而且还提出了第一个由无毒nc敏化的TTA-UC系统，这对该技术的实际应用非常重要。
Triplet energy transfer (TET) from semiconductor nanocrystals (NCs) has recently emerged as a new triplet sensitization paradigm. It remains unclear how trap states pervasive in NCs influence TET or whether trapped excitons can undergo efficient TET. Here we partially address this issue by studying TET from CuInS2 NCs as a model system because their photogenerated excitons are known to be "self-trapped" due to hole localization to intragap Cu states. We found that, thanks to the long lifetime (209 +/- 17 ns) of self-trapped excitons, they could be extracted with an efficiency of similar to 92.3% by surface-anchored anthracene despite that the TET rate was relatively slow (57.1 +/- 1.7 mu s(-1)). We further leveraged this efficient sensitization to achieve triplet-triplet-annihilation photon upconversion (TTA-UC) with a quantum yield of 18.6 +/- 0.3%. Thus, this study not only demonstrates trapped excitons can undergo efficient TET as well, but also presents the first TTA-UC system sensitized by nontoxic NCs which is important for the real-life application of this technique.