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Published on: October 9, 2012
Exciton storage by Mn(2+) in colloidal Mn(2+)-doped CdSe quantum dots
Rémi Beaulac1, Paul I Archer, Jos van Rijssel
1Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, USA.
Nano Letters
|August 14, 2008
Summary
Manganese-doped Cadmium Selenide (CdSe) quantum dots exhibit significantly longer photoluminescence decay times than undoped dots. This is due to energy transfer from manganese ions, enhancing exciton emission at higher temperatures.
Area of Science:
- Materials Science
- Quantum Dot Technology
- Nanotechnology
Background:
- Colloidal semiconductor quantum dots (QDs) are crucial in optoelectronics.
- Understanding photoluminescence (PL) dynamics in QDs is key for device applications.
- Manganese (Mn2+) doping in CdSe QDs can alter their optical properties.
Purpose of the Study:
- To investigate the photoluminescence decay times of Mn2+-doped CdSe quantum dots at elevated temperatures.
- To elucidate the mechanism behind the observed long decay times.
- To compare the high-temperature doping effect with previously reported low-temperature effects.
Main Methods:
- Synthesis of colloidal Mn2+-doped CdSe quantum dots.
- Time-resolved photoluminescence spectroscopy at temperatures above 100 K.
- Development and application of a kinetic model to analyze energy transfer dynamics.
Main Results:
- Observed excitonic photoluminescence decay times up to 15 microseconds at temperatures > 100 K.
- Decay times are approximately 1000 times longer than in undoped CdSe QDs.
- Back energy transfer from excited Mn2+ ions to CdSe excitons is identified as the cause.
- Kinetic model confirms efficient exciton emission despite being energetically higher than Mn2+ states.
Conclusions:
- Mn2+ doping in CdSe QDs leads to significantly prolonged photoluminescence decay at high temperatures.
- The mechanism involves thermal equilibrium and back energy transfer between Mn2+ and CdSe excitonic states.
- The effect of Mn2+ doping on CdSe QD luminescence at high temperatures is opposite to that at low temperatures.
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