| With the flourishing development of nanotechnology,a variety of new nanomaterials have become the basis of nanotechnology research and promote the progress of other disciplines and industrialization.Perovskite nanomaterials are favored by scientists because of their advantages such as relatively tunable bandgaps,narrow emission spectra,high fluorescence quantum efficiency,and wide color gamut.In particular,the development of methylammonium lead halide perovskite materials in solar cells has made rapid progress in a short time,and the photoelectric conversion efficiency has reached an industrial level.However,due to the water-oxygen sensitivity of the organic group in methylammonium perovskite nanostructure,the stability of the device has become the major bottleneck of the current industrialization.Therefore,the studies of more stable new types of perovskite nanomaterials have become the key to resolving this problem.Up to now,there are few researches about new types of perovskite nanomaterial systems.Based on these requirements,this paper would focus on the synthesis and performance of more stable perovskite nanomaterials.1.The synthesis of perovskite nanomaterials: The simple solution method is used to synthesize colloidal perovskite quantum dots(FAPb X3,X=Cl,Br,I)with good crystallinity,uniform size,and high fluorescence efficiency.By regulating the proportion of halogen elements in the precursor,the bandgaps of these perovskite quantum dots can be controlled covering the visible light range finally.By using a facile “hot injection” method,the colloidal inorganic perovskite quantum dots(Cs Pb X3,X=Cl,Br,I)with good crystallinity,uniform size,and high fluorescence efficiency can be synthesized.The morphology are and structure of quantum dots are analyzed with some characterizations.Furthermore,the tunable fluorescence can be tuned by adjusting the ratio of halogen anions in Cs Pb X3.2.Material control: By changing the ratio of organic ligands,the nanocrystalline morphology of perovskite FAPb X3 can be controlled from sphere nanoparticles to nanoplate.The growth mechanism of large-size perovskite nanocrystals has been studied.It is found that the content of organic ligands on the surface of perovskites can lead the asymmetric crystal growth in perovskite nanocrystals.By controlling the ligand content and reaction time,all-inorganic perovskite nanocrystals with different morphology have been synthesized and the growth mechanism of large-size perovskite crystals has been studied.In addition,in order to remove the influence of surface ligands during the synthesis process,a two-step method for synthesizing all-inorganic perovskite films has been developed.Finally,high-quality perovskite films are synthesized to follow-up calcium.All of these nanocrystals provide a solid foundation for advanced optical properties of perovskite in the follow-up works3.The enhanced stability of perovskite quantum dots: We use silica coating perovskite nanocrystals to enhance the stability of perovskite.While perovskite crystallize in colloidal solution,the silica precursor is added in situ without affecting the perovskite crystallinity.According to some characterizations,we demonstrate the perovskite quantum dots have been protected in silica sphere,which have a big size.Furthermore,the functional groups on the surface of the silica spheres can increase the hydrophilicity of the perovskite nanocrystals.In comparison with pure perovskite quantum dots,it has been demonstrated that this method does not affect the crystallization and optical performance of perovskite quantum dots.The isolation of air and water by silica can effectively improve the thermal stability of perovskite nanocrystals.The silica sphere also can suppress the ion exchange between the different halogen anions in colloidal perovskite solution.With the passivating surface,the surface defect states are reduced,carrier non-irradiation binding is suppressed,leading the suppressed blinking performance of perovskite nanocrystals.All of these results prove perovskite nanocrystals can be used as single photon emission source in single photon detection.4.The optical properties of perovskite nanocrystals: The synthesized colloidal perovskite nanocrystals have high photoluminescence efficiency,narrow half-width emission,tunable emission,which have great potential as optical gain media in nanolasers.In this work,we construct ultra-fast femtosecond system using one-photon and two-photon pump,to study the spontaneous emission,amplified spontaneous emission of perovskite nanocrystals and the temperature-dependent amplified spontaneous emission.Then a micro-area laser testing system is built with one-photon and two-photon femtoseconds lasers as pump.Finally,constructing a simple resonant cavity for perovskite quantum dots,we obtain up-conversion lasing action from perovskite quantum dots.Lasing action with different lasing mode also have been demonstrated in large-size perovskite nanocrystals with regular topography and smooth end faces.It indicates that when the pump intensity increases above the threshold,these perovskite nanocrystals can be regard as optical gain media and resonant cavity at the same time,leading lasing action.These results provide a new platform for the stable application of perovskite materials in optoelectronic devices,especially the two-photon frequency up-conversion nanolasers. |
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