Exciton Wavefuction Confiment And Optical Properties Of Quantum Dots

Colloidal quantum dots(QDs)are semiconductor nanocrystals with quantum confiment and synthesized in solution.The luminescence properties of QDs are size dependent due to quantum confinement,which makes them as promising emitters and photoelectric materials for important applications.This work puts forward the new concept of exciton wavefunction confiment,and studies photophysical and photochemical properties of new type fluorescence and phospherescence QDs.In the regime of fluorescence QDs,we introduced ZnCdS uniform alloy shell to maximize wavefunction confinement and meanwhile maintain good morphology and crystal structure.As a result,we extended the emission window of non-blinking QDs beyond red colors to cover almost whole visible colors.On the basis of on-time fraction,we introduced charging rate to evaluate blinking more precisely.Utlizing the developed method for studying single dot bleaching,we confirmed that both blinking and bleaching were suppressed via exciton wavefunction confiment on maximum extent.We studied the bi-exciton quantum yield of three types of QDs(uniform and gradient alloy CdSe/ZnCdS,and CdSe/CdS core/shell QDs)through a new established liquid film PL saturation method,and acquired the novel reslut that QDs with lower bi-exciton quantum yield owned better suppressed blinking.We conclued that wavefunction confiment(rather than Auger effect)played the key role in blinking from the direct relationship between bi-exciton quantum yield and Auger effect.In the regime of phospherescence QDs,we studyed basic optical properties of Mn-dopped ZnSe/ZnS core/shell QDs with varying pHs and temperatures,and the Mn:ZnSe/ZnS QDs presented great stability.And we studyed the peculiar PL saturaion via micro liquid film method.By analogy with the saturation reason of fluoresence QDs-Auger recombination,we explained the phenomenon using Auger ionization quantitatively.Utlizing the tunable lifetime and ambient stability of Mn:ZnSe/ZnS QDs,we completed the optimal application of lifetime imaging under the excitation power of saturation point.