首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Ultrafast Charge Carrier Relaxation and Charge Transfer Dynamics of CdTe/CdS Core-Shell Quantum Dots as Studied by Femtosecond Transient Absorption Spectroscopy
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Ultrafast Charge Carrier Relaxation and Charge Transfer Dynamics of CdTe/CdS Core-Shell Quantum Dots as Studied by Femtosecond Transient Absorption Spectroscopy

机译:飞秒瞬态吸收光谱法研究CdTe / CdS核壳量子点的超快电荷载流子弛豫和电荷转移动力学

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摘要

We are reporting ultrafast charge carrier and charge transfer dynamics of the CdTe quantum dot (QD) and type II CdTe/CdS core-shell QD materials with different shell (CdS) thicknesses. Herein, we have synthesized CdTe and CdTe/CdS core-shell quantum dots by using 3-mercaptopropionic acid as a capping agent. Steady state absorption and emission studies confirmed successful synthesis of CdTe QD and CdTe/CdS core-shell QD materials. Time-resolved emission studies indicate a longer emission lifetime of the CdTe/CdS core-shell as compared to CdTe QD materials, where in both cases only CdTe gets excited. We have carried out femtosecond transient absorption studies of these QD and core-shell materials by exciting them with 400 nm laser light and monitoring the transients in the visible to near-IR region to study charge carrier and charge transfer dynamics in the ultrafast time scale. On laser excitation, electron-hole pairs are generated which are confirmed by induced absorption signal for the charge carriers in the visible and near-IR region and an immediate bleach at excitonic position for both QD and QD core-shell. The carrier relaxation was found to be slower and the carrier lifetime was found to be longer in the QD core-shell as compared to the QD indicating charge transfer from core to shell. Carrier quenching studies have been carried out for both CdTe and CdTe/CdS by using benzoquinone (BQ, electron quencher) and Pyridine (Py, hole quencher) to assign the different relaxation processes. Details about the relaxation of hot carriers and the quenching effect on the relaxation dynamic of the charge carriers have been discussed for both QD and core-shell nanostructures.
机译:我们正在报告具有不同壳(CdS)厚度的CdTe量子点(QD)和II型CdTe / CdS核壳QD材料的超快电荷载流子和电荷转移动力学。本文中,我们使用3-巯基丙酸作为封端剂合成了CdTe和CdTe / CdS核-壳量子点。稳态吸收和发射研究证实了CdTe QD和CdTe / CdS核壳QD材料的成功合成。时间分辨发射研究表明,与CdTe QD材料相比,CdTe / CdS核壳的发射寿命更长,在这两种情况下,只有CdTe会被激发。我们对这些量子点和核壳材料进行了飞秒瞬态吸收研究,方法是用400 nm激光激发它们,并监测可见光到近红外区域的瞬态,以研究超快时间范围内的载流子和电荷转移动力学。在激光激发时,会产生电子-空穴对,这些电子-空穴对通过对可见光和近红外区域中的电荷载流子的感应吸收信号以及对于QD和QD核壳的激子位置处的即时漂白来确认。与QD相比,发现QD核壳中的载流子松弛较慢,载流子寿命更长,这表明QD表示电荷从核转移到壳。通过使用苯醌(BQ,电子猝灭剂)和吡啶(Py,空穴猝灭剂)来指定不同的弛豫过程,已经对CdTe和CdTe / CdS进行了载流子猝灭研究。对于量子点和核壳纳米结构,已经讨论了有关热载流子弛豫和对电荷载流子弛豫动力学的猝灭效应的细节。

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