| Summary: | 碩士 === 中原大學 === 應用物理研究所 === 93 === Photoluminescence (PL) and time-resolved PL (TRPL) in colloidal Ⅱ-Ⅵ CdSe/ZnS quantum dots (QDs) were studied at different temperatures and under different atmospheres. The PL intensity shows a biexponential decay at 9 K, consisting a fast component ( ) and a slow component ( ). It is found and increases at temperatures below 200 K. We suggest that the increase of the decay times at higher temperatures is due to a finite spatial phase-coherence effect. Based on the emission energy and temperature dependence of the lifetimes, we suggest that the fast and slow PL decay involves recombination of the delocalized and localized states, respectively.
In addition, we study PL of colloidal CdSe/ZnS QDs in air and oxygen atmospheres. The intensity of PL has been found to enhance as the pressure of gas increases from vacuum to 1 atm. This enhancement is explained by the passivation of the surface defects by oxygen. The lifetimes ( and ) of the PL decay of CdSe/ZnS QDs increase as a function of the air and oxygen pressure. The passivation of the surface defects and the electronic confinement effect is used to account for the increase of and with increasing the gas pressure, respectively.
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