Controlled Optical Performance And Application Of Highly Efficient Fluorescent Perovskite Quantum Dots

All inorganic lead halide perovskite quantum dots（CsPbX₃PQDs,X=Cl,Br,I）possess many advantages,such as tunable bandgaps,high surface tolerance to defects and high carrier mobility,etc.,and it has been considered as the potential optical materials in the light-emitting diodes（LEDs）,solar cells and photodetectors and so on.However,low photo-luminescent quantum yields（PLQYs）and the loss of optical performances resulted from poor stability still impede their practical application.Thus,to meet the requirement of application,it is currently an important issue for us to control their optical properties.The main research contents of the thesis were as follows:（1）The synthesis and photoluminescence kinetics of highly efficient CsPbI₃PQDs were studied.Ce³⁺-doped CsPbI₃PQDs were successfully synthesized via hot injection method,and the PLQYs of the production was as high as 99%.Transient absorption spectra and DFT calculations were used to study the process of the photoluminescence kinetics of CsPbI₃PQDs.It was found out that the Ce³⁺ions could not only increase the density of excitonic states closed to the high energy excitonic states（HES）,but also fill the defects caused by Pb²⁺vacancies and further improved the radiative recombination rates.It meant that the dopant provided more emissive channels,thus resulting in the improvement of the PLQYs of CsPbI₃PQDs.（2）The emission spectra of CsPbBr₃PQDs was controlled.By designing a new two-step saturated recrystallization method,the sizes of CsPbBr₃PQDs were limited within 2.8nm so as to make them generate strong quantum confinement effects（the exciton radius of the CsPbBr₃was ca.7 nm）.Thus,the spectral of the CsPbBr₃PQDs was successfully transferred from the green-emitting region to the blue one,and the PLQYs of the blue-emitting CsPbBr₃PQDs was as high as 87.20%.（3）The optical stability and application of blue-emitting CsPbBr₃PQDs were con-trolled.To solve the loss of optical performances resulted from the poor stability of blue-emitting PQDs,they were incorporated with PMMA to efficiently improve the stability of the blue-emitting CsPbBr₃-PMMA films,and the mechanism of it was studied.（4）The optical stability and application of the green-emitting CsPbBr₃PQDs were controlled.With aluminum stearate（Al St₃）matrix used as the coating layer,the optical stability of the green-emitting CsPbBr₃PQDs was controlled.The results illustrated that Al St₃not only provided hydrophobic matrix to protect the PQDs from the external envi-ronment,but also passivated the surface of the PQDs via the coordination bond of St-Cs,St-Pb,as well as the bond of the Al³⁺and Br^-ions.Thus,the CsPbBr₃-Al St₃composites possessed long-term stability in the presence of the water.With CsPbBr₃-Al St₃compos-ites used as the luminescent materials,the LED with excellent optical performances was successfully fabricated.Starting from the controlled synthesis,surface passivation and internal doping strate-gies,etc.,the routes of the controlled optical performances of PQDs were studied,The as-synthesized high quality PQDs had been successfully applied to fabricate blue and white LEDs,which revealed the excellent optical performances of these fluorescent PQDs.