Efficient Photoluminescence of Mn2+ Ions in MnS/ZnS Core/Shell Quantum Dots

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• 作者：Jinju Zheng ; Xi Yuan ; Micho Ikezawa ; Pengtao Jing ; Xueyan Liu ; Zhuhong Zheng ; Xianggui Kong ; Jialong Zhao ; Yasuaki Masumoto
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：October 1, 2009
• 年：2009
• 卷：113
• 期：39
• 页码：16969-16974
• 全文大小：238K
• 年卷期：v.113,no.39(October 1, 2009)
• ISSN：1932-7455

文摘

We have studied the mechanism of photoluminescence (PL) from MnS/ZnS core/shell quantum dots (QDs) synthesized via hot solution phase chemistry using a nucleation−doping strategy. Efficient PL of the Mn²⁺ ions with a quantum yield (QY) of over 35% is demonstrated in the resulting QDs coated with a thick ZnS shell on the MnS core. The MnS/ZnS core/shell QDs with a thick shell exhibit PL enhancement with increasing temperature in the range between 140 and 300 K, resulting from the thermal activation of charge carriers localized at the interface between the MnS core and the ZnS shell. The PL decays of the Mn²⁺ ions in the core/shell QDs consist of three exponential components with time constants on the scales of 1−2 ms, hundreds of μs, and tens of μs. Surprisingly, the PL lifetimes of Mn²⁺ ions show a very weak dependence on the shell thickness, which is clearly different from that of the PL QY of the QDs. The experimental results indicate that the mechanism for improving the PL QY in MnS/ZnS QDs can be understood in terms of a significantly enhanced energy transfer from the ZnS shell to Mn²⁺ ions and a slightly decreased nonradiative relaxation rate from Mn²⁺ ions to surface states/traps of the ZnS shell by the surface passivation of the QDs with a thick ZnS shell.