Study On The Performance Of Absorption,Dispersion And Photoluminescence Emission Of CdSe/ZnS Quantum Dots Doped In Uv Glue

In recent years, semiconductor nanocrystal quantum dots (QDs) become a research hotspot in semiconductor science field. It becomes the focus of attention due to unique optical and electronic properties, especially the performance of absorption, dispersion and photoluminescence (PL) emission.In this dissertation for the Science Master, CdSe/ZnS QD solution is prepared choosing ultraviolet (UV) glue as the background material with a rotary evaporation and ultraviolet curing method. As the primary optical properties of the QDs, i.e. absorption, dispersion and PL emission are investigated by absorption-spectrum method and discussed by analyzing the experimental data.(1) The absorption coefficient of CdSe/ZnS QDs doped in UV glue is measured by absorption spectra in the range of450-700nm wavelength with different doping concentrations. An empirical formula is suggested for the absorption coefficient as a function of wavelength and doping concentration. Besides, according to the classical scattering theory of harmonic oscillator model, a theoretical formula is deduced for the absorption coefficient as a function of wavelength and doping concentration. Comparing such theoretical and empirical formulas mentioned above, the resonance frequency and damping constant of CdSe/ZnS QDs are determined in Chapter3.(2) We measure the refractive index of QDs in the visible wavelength with different doping concentrations. An analytical expression is given for the refractive index as a function of wavelength and doping concentration. The refractive index of full QDs is also estimated using such an expression. Further, an empirical formula of the absorption coefficient as a function of refractive is presented according to the measured results. As a result, we determine the nonlinear relationship between the absorption coefficient and the refractive index.(3) The CdSe/ZnS QDFs are prepared in laboratory by using hollow fibers and vacuum pumping method. PL spectra of the QDFs were measured in different doping concentrations and fiber lengths by using fluorescence spectrometer. The measured PL spectra show that there is a single emission peak related with the doping concentration and the fiber length, which can be explained by fluorescent spectroscope. The wavelength of PL-peak has a red shift with the increasing doping concentration and the fiber length, which can be interpreted by the secondary absorbent-emission. Finally, we present an empirical formula of the PL-peak wavelength as a function of doping concentration and fiber length to describe the phenomenon of red shift.As an initial research of the primary performance of CdSe/ZnS QDs, the study in this dissertation is significant to the applications of CdSe/ZnS QDs used in optical amplifier, sensor and laser.