Solution-synthesized High Quality Metal Halide Perovskite Nanocrystals For Application In Light-Emitting Devices

As a new type of semiconductor nanocrystalline materials,metal halide perovskite nanocrystals(MHP NCs)have been hotly pursued in recent years.MHP NCs possess unique luminescence properties,such as high photoluminescence quantum yield(PLQY)approaching unity,narrow emission bandwidth,tunable wavelength across the entire visible spectrum,and compatibility with flexible/stretchable electrons.In addition,compared with traditional semiconductor luminescent materials,MHP NCs has the advantage of solution processing,which can be used as high-efficiency emission layers for the preparation of large-area and cost-effective solid-state light-emitting diodes(LED).In the application of LED devices,the synthesis and regulation of high-quality MHP NCs is extremely critical.Recent research progress has shown that the photoluminescence efficiency and stability of MHP NCs can be improved through strategies such as material composition design,synthesis,and surface engineering.At present,LED based on MHP NCs have shown more than 20%external quantum efficiency(EQE)and high luminescence in the green and red range.However,the luminescence and EQE of blue perovskite LEDs are still at a low level.In addition,unstable oleic acid and oleylamine ligand are attached to the surface of MHP NCs,which are easy to fall off and cause the degradation of the nanocrystals,hindering the carrier transport in the device.Therefore,preparing efficient and stable MHP NCs and appling them to solid-state light-emitting devices is a challenging and important research topic of significance.Based on the above research background,this master's thesis focuses on the solution-synthesis of MHP NCs and its application in LED devices.The main research content includes the following two aspects:1.We developed a simple and fast ultrasonic synthesis method to prepare CsPbBr3 nanoplates with high and pure blue emission.The prepared nanoplates have the high light emission efficiency and narrow emission band(PLQY at 462 nm is as high as 72%,full width at half maximum(FWHM)is 17 nm).The stability and fluorescence performance of CsPbBr3 blue nanoplates were further improved by Rb ion doping.Subsequently,the mixed solution of CaBr2-TBPO,a short-chain composite passivator,is used to treat the nanoplates to passivate surface defects.Finally,based on the processed RbxCs1-xPbBr3 nanoplates,a pure blue PeLED with an electroluminescence spectrum at 458 nm,a FWHM of 17 nm and an EQE of 0.29%was fabricated.2.We developed an alcohol amine ligand-assisted strategy to synthesize bright green light emissive colloidal MAPbBr3 nanocrystals with a PLQY of 73%.Due to the interaction between the alcohol amine molecule and MAPbBr3,not only the fluorescence performance is improved,but also the thermal stability of the MAPbBr3 nanocrystal film is improved.This alcohol amine molecule-assisted reprecipitation method provides a new trail for the preparation of high-efficiency luminescent metal halide perovskite nanocrystals.