Photoluminescence Intensity Fluctuations and Temperature-Dependent Decay Dynamics of Individual Carbon Nanotube sp3 Defects
Photoluminescence Intensity Fluctuations and Temperature-Dependent Decay Dynamics of Individual Carbon Nanotube sp3 Defects
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DOI：
10.1021/acs.jpclett.8b03732
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发表时间：
2019-03-21
影响因子：
5.7
通讯作者：
Htoon, Han
中科院分区：
文献类型：
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作者：
Kim, Younghee;Velizhanin, Kirill A.;Htoon, Han
最近通过单壁碳纳米管的 sp(3) 缺陷产生室温、电信波长单光子的演示将这些缺陷确立为一类新型量子材料。然而，它们在量子光源开发中的实际应用需要显着改善其不完美的量子产率（QY 类似于 10-30%）。还需要消除一些缺陷所观察到的 PL 强度波动。为了获得解决这些关键问题所需的基本理解，我们研究了（6,5）、（7,5）和（10,3）单壁碳纳米管（SWCNT）的芳基sp（3）缺陷在300至4 K的温度范围内的PL强度波动和PL衰变动力学。通过将缺陷态PL强度波动与PL衰变动力学的变化（或缺乏变化）相关联，我们确定了捕获效率的随机变化E-11带边激子（可能是由于缺陷附近存在波动势垒所致）是导致缺陷PL强度波动的主要机制。此外，通过基于光学允许和禁止（亮和暗）缺陷态对激子的捕获和去捕获的动力学模型分析PL强度的温度依赖性和单个缺陷的衰变动力学，我们估计势垒的高度在3-22 meV范围内。我们的分析还进一步证实了最近的 DFT 模拟结果，即发射性 sp(3) 缺陷态伴随着能量较高的光学禁制（暗）激子态。
Recent demonstration of room temperature, telecommunication wavelength single photon generation by sp(3) defects of single wall carbon nanotubes established these defects as a new class of quantum materials. However, their practical utilization in development of quantum light sources calls for a significant improvement in their imperfect quantum yield (QY similar to 10-30%). PL intensity fluctuations observed with some defects also need to be eliminated. Aiming toward attaining fundamental understanding necessary for addressing these critical issues, we investigate PL intensity fluctuation and PL decay dynamics of aryl sp(3) defects of (6,5), (7,5), and (10,3) single wall carbon nanotubes (SWCNTs) at temperatures ranging from 300 to 4 K. By correlating defect-state PL intensity fluctuations with change (or lack of change) in PL decay dynamics, we identified random variations in the trapping efficiency of E-11 band-edge excitons (likely resulting from the existence of a fluctuating potential barrier in the vicinity of the defect) as the mechanism mainly responsible for the defect PL intensity fluctuations. Furthermore, by analyzing the temperature dependence of PL intensity and decay dynamics of individual defects based on a kinetic model involving the trapping and detrapping of excitons by optically allowed and forbidden (bright and dark) defect states, we estimate the height of the potential barrier to be in the 3-22 meV range. Our analysis also provides further confirmation of recent DFT simulation results that the emissive sp(3) defect state is accompanied by an energetically higher-lying optically forbidden (dark) exciton state.