Unique Temperature Dependence and Blinking Behavior of CdTe/CdSe (Core/Shell) Type-II Quantum Dots

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• 作者：Bonghwan Chon ; Jiwon Bang ; Juwon Park ; Cherlhyun Jeong ; Jong Hwa Choi ; Jong-Bong Lee ; Taiha Joo ; Sungjee Kim
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：January 20, 2011
• 年：2011
• 卷：115
• 期：2
• 页码：436-442
• 全文大小：309K
• 年卷期：v.115,no.2(January 20, 2011)
• ISSN：1932-7455

文摘

Temperature dependent photoluminescence (PL) spectroscopy in a range of 5 K to room temperature (RT, 290 K) and single dot blinking behavior were investigated for CdTe/CdSe (core/shell, C/S) quantum dots (QDs). The QDs show type-II characteristics as both of the valence and conduction band levels of the CdTe core are placed higher in energy than those of the CdSe shell. The thickness of the CdSe shell was varied to control the degree of type-II character, and bare CdTe QDs were used as controls. The CdTe/CdSe (C/S) QDs have unique PL properties including (i) high susceptibility to PL thermal quenching with an exciton dissociation energy as small as 18 meV, compared with 46 meV for the CdTe QD, (ii) smaller band gap change showing only half the reduction of the control within the temperature change, and (iii) up to 27% larger PL bandwidth broadening than the control. The unique temperature-dependent properties were enhanced as the type-II character was increased by the thicker CdSe shell. Single dot level PL intermittency characteristics were studied for quasi type-II CdTe/CdSe (C/S) QDs that have alloyed layers at the core鈭抯hell interface. The quasi type-II QDs exhibited more frequent PL intensity intermittence blinking on and off at 290 K when compared with the CdTe QDs. However, the blinking kinetics follows similar universal power law on/off probability distributions with the 伪_on and 伪_off exponents evaluated as 1.57 and 1.38, respectively.