Study On The Preparation Of Highly Stable All-Inorganic Perovskite Quantum Dots With Zwitterionic Ligands And Light-Emitting Diodes

All-inorganic metal halide perovskite nanocrystals(QDs),have narrow full width at half-maximum,high color purity,adjustable emission wavelength covering the full visible range,wide color gamut,and fast carrier mobility.Moreover,it has the advantages of solution preparation and other advantages,so it has great research value in photoelectric applications such as light-emitting diodes(LEDs),solar cells,and photodetectors,etc.However,the perovskite QDs reported in literature generally have poor stability due to their ionic properties.So,they are prone to deterioration under the influence of water,oxygen,heat,and light.Furthermore,their performance may be greatly degraded by exposure to antisolvent and centrifugation-redispersion during post-processing of synthesis.Therefore,these are bound to be the major obstacles for perovskite QDs to become ideal optoelectronic materials.The research significance of this dissertation is to find a simple,feasible,environment-friendly,and safe synthesis method to synthesize all-inorganic perovskite QDs with good stability and excellent photoelectric properties.Then high-performance LED using the high-quality QDs obtained by this method was prepared high-performance LED.The main contents of this dissertation are as follows:1.Long-chain zwitterionic ligands have been demonstrated to greatly improve the chemical durability of colloidal CsPbBr₃ QDs by the chelate effect.However,the commonly used Br sources are toxic,and the reaction is too dynamic that it is hard to control the size of the crystal.We propose an eco-friendly strategy to improve the chemical durability of colloidal CsPbBr₃ QDs.Nontoxic,inexpensive,and directly available benzoyl bromine was used as the Br source,and tri-n-octylphosphine oxide was used as the adjuvant to control the reaction kinetics.Uniform,monodispersed QDs with an average size of ?11 nm was obtained.They had high photoluminescence quantum yields(PLQYs)of above 95% and,especially,showed good stability against attack by polar solvents.The PLQY remained 80% even after 12 cycles of purification.Furthermore,after 24 h of continuous radiation by 405 nm laser,the photoluminescence(PL)intensity showed negligible decrease,and the wavelength and full width at halfmaximum(FWHM)of PL had no significant change.2.The synthesis method in Chapter 3 is optimized.The "one-pot method" means feeding at one time,which eliminates the need for the operation of preparing precursor at high temperature.So,the synthesis time is greatly shortened,the difficulty of operation is reduced,and the reaction efficiency is improved.The synthesized QDs have uniform size and distribution,high PLQY(?95.7%),narrow FWHM(?18 nm),and can achieve luminescence in the full range of visible light by anion exchange method.In addition,the hybrid perovskite QDs with near-ultraviolet emission and blue emission can be prepared by thermal injection of mixed halogens.The films of these QDs have excellent stability against water,oxygen and heat and has been successfully used in the preparation of LEDs as a light-emitting layer.The EQE of the obtained green LED and blue LED are as high as 4.61% and 1.15%,respectively.