Surface Engineering Regulation And Excited State Dynamics Of Perovskite Quantum Dots

Recently,perovskite quantum dots（QDs）have been widely applied in various fields,such as solar cells,lasers and so on.However,perovskite QDs still have some problems,such as instability,low luminescence efficiency and low carrier transport efficiency,which hinder their application in optoelectronic devices.For the scientific problems outlined above,this thesis carried out a series of surface regulation works from the perspective of surface engineering to regulate the optical properties,stability and excited dynamics.The main contents are as follows:1.The photoluminescence regulation of perovskite quantum dots via defect passivation and lattice distortion by potassium bromide dopingDifferent proportion potassium bromide（KBr）doped CH₃NH₃PbBr₃（CH₃NH₃⁺=MA⁺）QDs were prepared and characterized.We further systematically studied the photoluminescence（PL）law and found that lattice distortion results from the QDs average size decreased,and surface passivation can improve the PLQY and fluorescence lifetime.The synergistic effect of surface passivation and lattice distortion caused the PL intensity of doped perovskite QDs to be initially prompted by the KBr doping and then inhibited with further growing doping amount.That is,there exists an optimal doping ratio.Meantime,the stability of these synthesized QDs was significantly improved by inhibiting phase separation and passivating the surface defect states.2.Surface amino acid ligand modulated perovskite quantum dots for fluorinion detection（L/D）Ala-MAPbBr₃QDs with high stability were successfully prepared by introducing amino acid molecule as the surface ligand.The introduction of amino acid ligands could change the morphology and size of QDs,which can regulate the steady-state spectral range.The result of femtosecond transient absorption spectra indicated that the introduction of amino acid ligands lead to increased exciton density of the conduction band edge and facilitated radiative recombination processes.Therefore,it further resulted in higher PLQY.Based on the interaction between amino acid ligands and fluorinion as well as the large O-H…F bond energy,（L/D）Ala-MAPbBr₃QDs can sensitively and selectively detect the fluorinion.3.Surface functional dye ligand enhanced photoluminescence and chirality transfer of perovskite quantum dotsBased on the KBr doped QDs work,（R/S）AQ-K_0.23MA_0.77PbBr₃QDs were successfully prepared by designing and synthesizing chiral functional molecules（R/S-AQ）as surface ligands.Using the electronic interaction between the chiral molecule and the QDs lattice,the chirality transfer from the chiral ligand to the perovskite QDs was realized,chiral perovskite materials were successfully obtained.Excited dynamic analysis exhibited that the introduction of chiral ligands reduced the possibility of trapping excitons and promoted more excitons to the ground state through the radiative recombination process,which lead to these modified QDs with higher PLQY.4.Ionic liquid assisted preparation of highly stable core-shell perovskite quantum dots and light-emitting diodes applicationA series of C_n-QDs@SiO₂（n=4,10,16）QDs were successfully prepared by introducing ionic liquids（ILs）with different alkyl chain lengths as surface ligands and simultaneously utilizing tetramethoxysilane（TMOS）hydrolysis.With the increase of the ILs alkyl chain length,the blue-shifted wavelength value and the time of reaching the maximum PL intensity for these C_n-QDs@SiO₂QDs were decreased.It indicated that the increased alkyl chain ILs could accelerate the TMOS hydrolysis rate.Because of the ILs surface passivation effect,the PLQY of the C_n-QDs@SiO₂QDs was reached 92.83%and these QDs exhibited excellent stability.Based on the excellent optical properties and stability of QDs,they were successfully applied to white light-emitting diodes（WLEDs）.