Study On Preparation,Optical Property And Stability Improvement Of CsPbBr₃ Quantum Dots

Cs Pb Br₃ quantum dots（QDs）have attracted much attention from researchers because of their excellent optical properties such as high fluorescence quantum efficiency,half-peak width and narrow,and have broad application prospects in photoelectric devices such as photodetectors,light-emitting diodes and lasers.However,due to the inherent ionic properties of Cs Pb Br₃ QDs,they are very sensitive to external environments such as temperature,light and water.When they are in these environments,their optical properties will be significantly decrease,which seriously limits their application degraded.Therefore,the poor stability of perovskite quantum dots is the core problem that needs to be solved.In this work,a dual strategy of ion doping and coati ng is proposed to solve the sta bility probl em of Cs Pb Br₃QDs.The main research contents of this work are as follows:（1）The effect of different reaction times and cesium precursors on Cs Pb Br₃ QDs synthesized by hot injection method was investigated.The experimental results show that the particle size of Cs Pb Br₃ QDs can be controlled by changing the reaction time,so as to regulate the optical properties of Cs Pb Br₃ QDs.When the reaction time is 10 s,the optical properties of Cs Pb Br₃ QDs are the best.The obtained Cs Pb Br₃ QDs have uniform grain size（12.2 nm）and dispersion,cubic morphology.In terms of optical properties,the emission peak is 522 nm,the half-peak width is 22.5 nm,and the PLQY is 33.1%.（2）In order to solve the problem of poor stability in Cs Pb Br₃ QDs,the ion doping strategy is selected.Through the concentration gradient experiment,it is concluded that4/6 In/Pb feeding ratio is the optimal feeding ratio.The PLQY of the synthesized In³⁺doped Cs Pb Br₃ QDs increased to 52.1%,which is because the exciton recombination path changed after the introduction of In³⁺,and the surface defects of the QDs were passivated,which increased the probability of radiation recombination.The stability of In³⁺doped Cs Pb Br₃ QDs was improved.After 6 days of UV irradiation,the luminescence intensity of In³⁺doped Cs Pb Br₃ QDs and undoped Cs Pb Br₃ QDs decreased to 46%and 24%of unilluminated samples,respectively.When it is placed at 120℃,its luminescence intensity decreases to 30%and 15%of that at room temperature respectively.The improvement of stability is due to the enhanced Pb-Br interaction after In³⁺doping,and the contraction of[Pb Br₆^4-]octahedron,which improves its structural stability.In³⁺doped Cs Pb Br₃ QDs were used as green luminescent materials to construct white LED devices.The color gambit was 127%of the standard NTSC,luminescence effects was 23.7 lm/W.（3）In order to further improve the stability of In³⁺doped Cs Pb Br₃ QDs,the coating strategy is selected for double protection of quantum dots.In³⁺doped Cs Pb Br₃ QDs were synthesized in situ using two mesoporous materials（silica gel and silica）as microreactors.The results show that PLQY of In³⁺doped Cs Pb Br₃@Silica Gel composite and In³⁺doped Cs Pb Br₃@SBA-15 composite is increased to 53.87%and65.2%,respectively,because mesoporous materials can effectively prevent the agglomeration and self-absorption of quantum dots.In³⁺doped Cs Pb Br₃@Silica Gel composite and In³⁺doped Cs Pb Br₃@SBA-15 composite maintained 38%and 41%of the original luminescence intensity after 16 days of UV irradiation,respectively.When the temperature reaches 120℃,38%and 46%of the original luminous intensity are maintained respectively.After being placed in a humid environment for 12 h,the luminescence intensity decreased slightly,maintaining 86%and 78%of the original luminescence intensity respectively.The stability improvement is mainly due to the fact that the mesoporous material can protect the quantum dots as a protective shell,and can also play a role in separating the quantum dots.In³⁺doped Cs Pb Br₃@Silica Gel composite and In³⁺doped Cs Pb Br₃@SBA-15 composite were used as green luminous materials to construct white LED devices.The color gamutums were 126%and 128%of the standard NTSC,respectively.The luminescence effects were 43.2 lm/W and 83.7lm/W,respectively.