期刊
NANO LETTERS
卷 13, 期 3, 页码 925-932出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl400141w
关键词
Nanocrystal; quantum dot; multiexciton; charged nanocrystal; radiation detection; cathodoluminescence
类别
资金
- Los Alamos National Laboratory LDRD program
- Chemical Sciences, Bioscience and Geosciences Division of the Office of Basic Energy Sciences (BES), Office of Science, U.S. Department of Energy
- Center for Nanoscale Materials, a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility [DE-AC02-06CH11357]
Using a combination of transient photoluminescence and transient cathodoluminescence (trCL) we, for the first time, identify and quantify the distribution of electronic excitations in colloidal semiconductor nanocrystals (NCs) under high-energy excitation. Specifically, we compare the temporally and spectrally resolved radiative recombination produced following excitation with 3.1 eV, subpicosecond photon pulses, or with ionizing radiation in the form of 20 keV picosecond electron pulses. Using this approach, we derive excitation branching ratios produced in the scenario of energetic excitation of NCs typical of X-ray, neutron, or gamma-ray detectors. Resultant trCL spectra and dynamics for CdSe NCs indicate that all observable emission can be attributed to recombination between states within the quantum-confined nanostructure with particularly significant yields of trions and multiexcitons produced by carrier multiplication. Our observations offer direct insight into the transduction of atomic excitation into quantum-confined states within NCs, explain that the root cause of poor performance in previous scintillation studies arises from efficient nonradiative Auger recombination, and suggest routes for improved detector materials.
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