Temporal development of occupations of sublevels in a CdS QD with a radius of (its energy band gap is ). The excitation power , the phonon-electron scattering related parameter , and excitation photon energy , correspond to a two-photon excitation.
Schematic diagram of transition processes. (a) Electron picture. Black dots are electrons. (b) Electron-hole picture. Black dots in the conduction band (CB) are electrons. They are holes in the valence band (VB).
Optical spectra of photon emissions from 20 QDs. (a) Nonradiative processes are included. (b) Excluding nonradiative processes. The dashed lines are obtained by broadening every emitted photon count by using a Lorentzian function (with a full width at the half maximum of ). The QD radius , excitation optical power , the phonon-electron scattering related parameter , and excitation photon energy , correspond to a two-photon excitation.
Optical spectra of core-multishell QD. (a) Solid line: Theoretical absorption spectrum. Dashed line: Experimental result. (b) Optical emission spectra after counting. , the excitation photon energy is , corresponds to multiphoton excitation.
Multiphoton-excited optical spectra of 1400 QDs after counting by a laser pulse in the form of , , the phonon-electron scattering related parameter , , , and excitation photon energy is , correspond to multiphoton excitation.
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