Luminous Thermal Stability And Photoluminescence Quenching Mechanism Of Perovskite Quantum Dots

Perovskite quantum dots(QDs)as a class of new optoelectronic materials show great potential for applications in lighting and display,because of their high photoluminescence(PL)quantum efficiency(>90%),narrow linewidth(12-40 nm),wide color gamut,solution synthesis and processing characteristics.In this thesis,all-inorganic CsPbBr3 and organic-inorganic hybrid perovskite CH3NH3PbBr3 QDs have been synthesized by hot-injection approach and ligand assisted precipitation,respectively.The size of the QDs is controlled by adjusting the reaction temperature and time to change the emission wavelength.The structure and morphology of perovskite QDs were characterized by X-ray diffraction(XRD)and transmission electron microscopy(TEM).The luminescent properties of perovskite QDs and their emission quenching caused by the interaction between the QDs and organic charge transporting materials were studied by steady-state and time-resolved PL spectroscopy.Then the PL thermal stability of perovskite QD films was discussed via temperature-dependent PL spectroscopy.The main points are as follows:(1)The PL properties of the all-inorganic perovskite CsPbBr3 QDs in the temperature range of 80-360 K were studied by the temperature-dependent PL spectroscopy.The experimental results indicated inorganic perovskite QDs exhibited a thermal PL quenching in the temperature range of 80-300 K and a thermal degradation at temperatures above 300 K.The linewidths,peak energies,and lifetimes of PL emissions for the QD films as a function of temperature were discussed in detail to analyze the luminescence mechanism of CsPbBr3 QDs(2)The effect of organic charge transporting materials on the luminescent properties of all-inorganic CsPbBr3 perovskite QDs was studied by means of steady-state and time-resolved PL spectroscopy.It was confirmed that the PL quenching of the CsPbBr3 QDs via the electron transporting material(TPBi)and hole transporting material(CBP)was mainly caused by the static quenching.The PL quenching efficiency was dependent on the size of the CsPbBr3 QDs.,which was consistent with the type I energy level alignment between the QDs and the organic charge transporting materials.(3)The PL properties and luminous thermal stability of organic-inorganic hybrid perovskite CH3NH3PbBr3 QDs were investigated.By comparing the temperature-dependent PL spectra of the CH3NH3PbBr3 QD films and QD/PMMA mixed thin films,the mixed film exhibited better PL thermal stability,which suggested that PMMA was possessed of obvious passivation effect on the surface defects of QDs.