Investigation On The Stability And High Color Rendering Index Warm White Light Emitting Diodes (WLED) Of Inorganic Perovskite CsPbBr₃ Nanocrystals

White light emitting diodes(WLEDs)based on all-inorganic halide(CsPbX₃,X=Cl,Br and I)perovskite quantum dots(QDs)have attracted broad attention due to their exceptional optoelectronic properties.In particular,as luminescent components,green CsPbBr₃ QDs have been incorporated into WLEDs to improve the performance of white emission,due to improving their color purity and high photoluminescence quantum yield(PLQY).Unfortunately,the reported CsPbBr₃ QDs were vulnerable to humidity,oxygen and heat,limiting their practical application seriously.In terms of these issues,this thesis would focus on the stability and high color rendering index of warm WLEDs based on inorganic perovskite CsPbBr₃ nanocrystals.The main contents of this thesis is as follows:(1)It has been found that the red CsPbI₃ QDs suffer poor stability and narrow full-width at half-maximum(FWHM)of the emission spectrum.Thus,the Ag–In–Zn–S QDs with good stability and wide FWHM were selected to replace the red CsPbI₃ QDs and to act as the red component in the warm white spectra.Herein,a novel method was proposed to synthesize Ag-In-Zn-S QDs with high PLQY at low temperature(110?).The FWHM of red Ag-In-Zn-S QDs is?100 nm.By optimizing the amount of Zn incorporation,the obtained highest PLQY of Ag-In-Zn-S QDs was 60%,which was higher than that of Ag-In-S QDs(PLQY=53%).This lays the foundation for high-quality WLEDs.(2)A fast one-step in-situ method under room-temperature in air was proposed to synthesize CsPbBr₃ QDs coated with SiO₂(CsPbBr₃@SiO₂),where the whole process took only 20 s.The obtained CsPbBr₃@SiO₂ QDs were uniformly distributed as monodisperse particles without any aggregation.By optimizing the SiO₂ coating layer,the obtained highest PLQY of CsPbBr₃@SiO₂ QDs was 75%,which was higher than that of pure CsPbBr₃ QDs(PLQY=30%).In addition,the CsPbBr₃@SiO₂ QDs demonstrated excellent stability under the oxygen,moisture,heat and polar solvent.Finally,we incorporated the optimized green CsPbBr₃@SiO₂ QDs and red In-Ag-Zn-S QDs on a blue LEDs to realize warm white light emission.Our WLEDs exhibited the excellent luminescent performance with a CRI of 91,correlated color temperature(CCT)of 3689 K,luminous efficiency(LE)of 40.6 Lm W^-1 and color coordinate of(0.4037,0.411).(3)Subsequently,to further improve the the properties of CsPbBr₃ QDs and WLEDs.Herein,a facile strategy under room-temperature in air was proposed to synthesize CsPbBr₃ QDs treated with didodecyldimethylammonium bromide(DDAB-CsPbBr₃).These ligands were used to replace the original the oleylamine and oleic acid,and then the DDAB-CsPbBr₃ QDs were coated with SiO₂(DDAB-CsPbBr₃/SiO₂ composite nanocrystals).Organic ligand DDAB not only decreased the surface defects of CsPbBr₃ QDs,improved PLQY and reduced agglomeration,but also reduced the damage of alcohol and water to CsPbBr₃ QDs.Finally,the incorporated green DDAB-CsPbBr₃/SiO₂ composite nanocrystals and red In-Ag-Zn-S QDs on a blue LEDs could also realize warm white light emission.The color rendering index and white light purity of WLEDs were improved,which showed a CRI of 94,color coordinates of(0.38,0.41),and CCT of 4017 K.This thesis not only provides an effective strategy for the stability of CsPbBr₃ QDs,but also proposes an effective strategy to improving the CRI of WLEDs,demonstrating its broad future applications in solid-state lighting fields.It would also provide a new research idea for the development of high-efficient perovskite white light LEDs.