期刊
ACS NANO
卷 17, 期 21, 页码 21962-21972出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.3c08377
关键词
band-edge electronic structure; semiconductor core/shellnanocrystal; photochemical doping; charged exciton; single-dot spectroscopy
The electron-hole pair in a CdSe/CdS core/shell nanocrystal shows different behavior under different confinement regimes. The reduction of optical bandgap is mainly caused by the change in the band-edge electron level. Additionally, the shift of electron levels can switch the energy order of transitions. The thermal distribution of electrons follows number-counting statistics.
An electron-hole pair in a cube-shaped CdSe/CdS core/shell nanocrystal exists in the form of dynamic excitons across the strongly and weakly confined regimes under ambient temperatures. Photochemical doping is applied to distinguish the band-edge electron and hole levels, confirming an effective mass model with universal constants. Reduction of the optical bandgap upon epitaxy of the CdS shells is caused by lowering the band-edge electron level and barely affecting the band-edge hole level. Similar shifts of the electron levels, yet retaining the hole levels, can switch the order in energy of the three lowest-energy transitions. Thermal distribution of 1-4 electrons among the two thermally accessible electron levels follows number-counting statistics, instead of Fermi-Dirac distribution.
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