Study On Synthesis And Optoelectronic Application Of Lead Halide Perovskite Nanomaterials

As a new type of luminescent material,halide perovskite has the characteristics of broadly adjustable photoluminescence（PL）ranges from the ultraviolet（UV）to the near-infrared region,narrow full width at half maximum（FWHM=12-40 nm）,high PL quantum yield（PLQY）,high defect tolerance,and simple synthesis process,which make it very suitable for application in the fields of luminescent solar concentrators（LSCs）and liquid crystal displays（LCD）.However,halide perovskite is an ionic salt that is very sensitive to the surrounding environment including light,heat,water,and oxygen,which would limit its practical application.So,it is great necessary to find a strategy that can improve the stability of lead halide perovskite while maintaining its excellent optical properties.In this thesis,three strategies including optimization of synthesis route,ligand exchange,and polymer encapsulation are used to improve the PLQY of perovskite nanomaterials and the stability of light,heat,humidity,and air,so as to realize the applications in LSCs and LCDs.The main contents of this thesis are as follows:（1）A novel triphenylphosphine（TPP）treatment strategy was developed to prepare near-infrared emission Cs Pb I₃ nanocrystals-polymer composite thin-film LSCs featuring high absolute photoluminescence quantum yield（PLQY）,low reabsorption and high stability.The PL emission of centered at about 700 nm with 99.4±0.4%of PLQY,and narrow FWHM of 75 me V（30 nm）.Compared with the LSCs prepared with classic Cs Pb I₃ NCs,the water stability and light stability of the LSCs after TPP treatment has been greatly improved,even after 30 days of immersion in water and strong mercury-lamp irradiation（50 m W/cm²）,which is mainly due to the strong coordination ability and oxygen removal ability of TPP.In addition,TPP can also be used as a photoinitiator because of the lone pair of electrons on the phosphorus atom,as-prepared films show higher PLQY and stability than the films fabricated by the other common initiators.Large-area（ca.75 cm²）infrared LSCs were achieved with a high optical conversion efficiency of 3.1%at a geometric factor of 10.（2）We employed lauryl methacrylate（LMA）as a solvent,replacing the commonly used ODE,to synthesize green-emitting Cs Pb Br₃ NCs by a modified hot-injection method.As-synthesized nanocrystals stock solution is directly mixed with oligomer and photoinitiator to fabricate Cs Pb Br₃ NCs polymer composite film by ultraviolet light polymerization.Compared with the classical hot injection method（octadecene as a solvent）,the nanocrystals prepared by LMA as a solvent did not need the process of centrifugation,separation,and dispersion.Significantly,as-prepared NCs-polymer composites film shows a higher fluorescence quantum yield（85%-90%）,while the PLQY of NCs polymer composites films prepared by the classic method is only 54%.Meanwhile,the LMA-Cs Pb Br₃ nanocrystals polymer films show good stability against light,moisture,and heating.Peak shape and PLQY of the LMA-Cs Pb Br₃ film didn’t have obvious change after aging in water at 50°C for 200 hours.Finally,as-prepared stable and bright green-emitting Cs Pb Br₃ NCs polymer film and red-emitting phosphor（KSF）were used as the down-converting fluorescent material of the blue light-emitting diode in the liquid crystal backlight to construct a prototype display device,showing a wider color gamut of 115%（CIE 1931）,which is better than traditional cadmium-based quantum dot display devices.（3）We have developed a simple yet effective method to prepare FAPb Br₃perovskite NCs directly in aqueous solution at room temperature without the protection of inert gas using polyvinylpyrrolidone PVP as ligands.High-quality two-dimensional FAPb Br₃ perovskite NCs were successfully prepared by optimizing reaction conditions.As-synthesized perovskite NCs exhibited excellent optical properties,with an emission peak position at 542 nm,a narrow FWHM of 18 nm,a small stokes shift of 11 nm,and a high PLQY of 93.3%.Then,a fluorescent metal ion probe based on FAPb Br₃perovskite nanocrystals is prepared for detecting Cu²⁺,and as-prepared copper ion fluorescent probe shows higher sensitivity and good selectivity.As-fabricated photoluminescence ion probe based on FAPb Br₃ perovskite nanocrystalline show high sensitivity and good selectivity to Cu²⁺.