Study On The Optical Properties Regulation Of All-inorganic Perovskite Quantum Dots For Light-emitting Diodes Applications

All-inorganic cesium lead-halogen perovskite quantum dots?QDs?has become the ideal material for a new generation of luminescent devices because of its full-spectra adjustable emission wavelength,high fluorescence quantum yield and high color purity.At present,most of the high-quality quantum dot light-emitting diodes?QLEDs?reported so far are based on traditional lead halide perovskite QDs,and the material has poor stability in air and contains heavy metal lead.Therefore,it is particularly important to explore high-luminescence,stable low-lead or lead-free perovskite QDs.This thesis focuses on improving the stability of perovskite QDs and reducing their toxicity as the research theme,and conducts systematic research on its preparation,performance and its application in light emitting diodes.The specific conclusions are summarized as follows:?1?High-quality CsPbBr₃ QDs were prepared by thermal implantation to serve as the light-emitting layer of the LED.ZnO nanoseeds were prepared by magnetron sputtering and the sol-gel method.By combining the CsPbBr₃ QDs with the n-ZnO nanorod/p-GaN,the blue-green dual-wavelength light-emitting diodes were realized,and the effect of ZnO nanoseeds on the p-GaN/n-ZnO nanorod/CsPbBr₃ quantum dots LED performance is deeply investigated.The results show that the magnetron sputtering ZnO nanoseeds can induce regular vertical ZnO nanorod arrays,and the corresponding device presents better electroluminescence performance.?2?We used more soluble cesium acetate instead of cesium carbonate,and synthesized high-quality CsPbBr₃ QDs by an improved thermal injection method;then we used 3-aminopropyltriethoxysilane?APTES?as a ligand and SiO₂ source to synthesize high stability CsPbBr₃ QDs@SiO₂ material.The results showed that CsPbBr₃ QDs@SiO₂ has good crystallinity and excellent luminescence properties.The SiO₂ protects the delicate QDs from air and water contact and suppresses the common anion exchange reactions between the QDs,which makes the stability of QDs enhanced.Subsequently,WLED were fabricated by compounding the obtained CsPbBr₃ QDs@SiO₂ with the red CsPbBrI₂ QDs@SiO₂ and matching with commercial blue chips.The prepared WLED has excellent optical performance and stability.The CIE color coordinates were?0.3511,0.3437?at a current of 20 mA and emission peaks of the WLED was stable after working continuously for 16 h.?3?We introduced a facile one-pot strategy to synthesize highly stable CsPb_0.7Mn_0.3Br_0.75Cl_2.25.25 QDs@SiO₂ with strong orange-yellow photoluminescence.The microstructure characterization indicates that the CsPb_0.7Mn_0.3Br_0.75Cl_2.25quantum dots were effectively encapsulated by the SiO₂.The CsPb_0.7Mn_0.3Br_0.75Cl_2.25QDs@SiO₂ show higher humidity stability and thermal stability than the CsPb_0.7Mn_0.3Br_0.75Cl_2.25 quantum dots without SiO₂ coating.The WLED were obtained by coating orange-yellow CsPb_0.7Mn_0.3Br_0.75Cl_2.25.25 QDs@SiO₂ and blue CsPbBrCl₂ QDs@SiO₂ quantum dots on the ultraviolet gallium nitride light-emitting diode chip.The as-prepared WLED show bright white light emission with a color coordinate of?0.3347,0.2825?,color rendering index is up to 82 and correlated color temperature of 5329 K.