Exciton Storage by Mn2+ in Colloidal Mn2+-Doped CdSe Quantum Dots

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• 作者：Ré ; mi Beaulac ; Paul I. Archer ; Jos van Rijssel ; Andries Meijerink ; Daniel R. Gamelin
• 刊名：Nano Letters
• 出版年：2008
• 出版时间：September 10, 2008
• 年：2008
• 卷：8
• 期：9
• 页码：2949-2953
• 全文大小：224K
• 年卷期：v.8,no.9(September 10, 2008)
• ISSN：1530-6992

文摘

Colloidal Mn²⁺-doped CdSe quantum dots showing long excitonic photoluminescence decay times of up to τ_exc = 15 μs at temperatures over 100 K are described. These decay times exceed those of undoped CdSe quantum dots by ∼10³ and are shown to arise from the creation of excitons by back energy transfer from excited Mn²⁺ dopant ions. A kinetic model describing thermal equilibrium between Mn^{2+ 4}T₁ and CdSe excitonic excited states reproduces the experimental observations and reveals that, for some quantum dots, excitons can emit with near unity probability despite being ∼100 meV above the Mn^{2+ 4}T₁ state. The effect of Mn²⁺ doping on CdSe quantum dot luminescence at high temperatures is thus completely opposite from that at low temperatures described previously.