Preparation Of Cesium Lead Halide Perovskite Nanocrystals And Their Application In Light-emitting Displays

Since 2015,cesium lead halide(CsPbX₃,X=Cl,Br,I)all-inorganic perovskite nanocrystals(NCs),as a new type of photovoltaic material,have emerged in the field of optoelectronics,and a series of outstanding research results have been obtained.CsPbX₃NCs show great potential application value in the field of solid-state lighting and display because of high photoluminescence quantum yields(PLQY),narrow emission spectra,tunable energy band covering the whole visible region,as well as the low production cost.Although CsPbX₃NCs exhibit different light colors in the visible region,there are few reports based on pink light emission,which greatly limits the application of CsPbX₃NCs in special lighting field.More importantly,further optimization for the fluorescent efficiency and stability of CsPbX₃NCs is the key to commercial application,and the control of NC surface state is considered as an effective optimization strategy.The studies on the patterning of cesium lead halide NCs are few,so it is urgent to propose a simple,fast and accurate patterning strategy for the integration and miniaturization of CsPbX₃display devices.In view of these,the research works in this paper are as follows:(1)We proposed a straightforward and effective strategy for preparing pink all-inorganic halide perovskite NC phosphors for light-emitting diode(LED)application.The pink perovskite NCs with varying Mn contents could be easily and steadily obtained via postsynthetic ion exchange at room temperature.The dependence of the size and optical properties of pink NCs on dopant content was systematically investigated.The reversible anion exchange processes of pink perovskite NCs were conducted with halide salts containing or excluding Pb.The contrasting results suggested that the irreversibility of energy transfer process was mainly affected by the fully reversible cation exchange between Pb²⁺and Mn²⁺.The pink NCs with better stability of dopant emission and high monodispersity were successfully developed by compounding with silica.A pink LED was further made by using the pink NCs/silica composites as pink phosphors on a 395 nm In Ga N LED chip.This work provides a feasible strategy for the fabrication of pink LEDs,which may have great application prospects in the field of special lighting,like neon lights and plant growth lights.(2)Cs Pb Br₃NCs with different morphological characteristics were prepared by room-temperatureligand-assistedreprecipitationmethodbyusing didodecyldimethylammonium bromide(DDAB)and organic acids with different chain lengths as surfactants,and the effects of the amount of two ligands on the morphology and optical properties of the products were explored.According to the results of time-resolved photoluminescence(PL)and transient absorption(TA)spectra,it was further confirmed that the defect passivation in the as-prepared NCs was achieved,which effectively inhibited the nonradiative recombination,so that the NC solution showed long carrier life and high PLQY.In addition,the stability of the as-obtained NCs was studied by water-and air-stability tests.Finally,the white LED was manufactured by using the green CsPbX₃NC powder.The CIE 1931 color coordinate of the white LED was(0.330,0.329),and the triangle area of the corresponding color gamut on the CIE chromaticity diagram was about128%of the NTSC color gamut.Therefore,the as-prepared NCs have potential application value in the field of solid-state lighting and display.(3)A novel and facile strategy for luminescent patterning technologies of inorganic perovskites was proposed by using 532 nm femtosecond laser pulses.One step implemented in-situ synthesis and arbitrary patterning of cesium lead bromide/polymer nanocomposites on glass substrates under laser irradiation.The localized growth of the nanocomposites benefited from ring-opening polymerization of organic solvent,which was caused by laser-induced non-linear absorption and energy deposition.The power threshold for machining nanocomposites could be reduced significantly by using heat-conducting substrates,providing Cs-based halide perovskites the possibilities to integrate on flexible substrates.Moreover,the resulting nanocomposites exhibited bright fluorescence with a narrow spectral width of 20 nm due to the uniform size,comparable to the perovskite NCs prepared by the conventional liquid-phase method.The repeatable and continuous laser-processed lines with 1.2?m minimum line width were developed successfully.These findings suggest that this patterning strategy has potential application prospects in miniature anti-counterfeiting patterns and light-emitting displays.