Synthesis Of Perovskite Based Nanocomposites And Their Optoelectronic Applications

Since the semiconductor nanomaterials were first reported,they have been promoted development in various fields because of their unique characteristics.Among these materials,the perovskite quantum dots?QDs?became one of the most popular exploration directions.Because of their excellent optical properties such as narrow emission bandwidth,high photoluminescence quantum yield,adjustable bandgap in the visible range,etc.,they have been widely used in the field of optoelectronics such as micro-laser,photocatalysis,solar cells.However,the instability of organic-inorganic perovskites and harsh purification procedures of all inorganic perovskites seriously restricted their further commercial application and development.In order to solve the above problems,this thesis describes the method of modifying quantum dots by introducing specific oxides.Based on the improvement of optical charateristics of the perovskite nanocomposites,their potential application on microlaser and photocatalysis were studied.The work of this thesis is mainly described as followed three aspects:?1?The synthesis and design of quantum dot materials.The organic-inorganic hybrid perovskite quantum dot of FAPbBr₃ with high photoluminescence quantum yield and low band gap energy was synthesized by re-deposition method at room temperature.On this basis,the aminated SiO₂ nanospheres were introduced to prepare the FAPbBr₃/SiO₂composite structure.The composite nanomaterial of FAPbBr₃/SiO₂ with higher stability at room temperature was obtained by amine chain-directed growth method.The all-inorganic perovskite CsPbBr₃ quantum dots with excellent stability were synthesized by hot injection method.TiO₂ nanotubes were introduced to successfully solved the problem of purification for quantum dots.?2?The study on the random lasers application of perovskite nanocomposte.This work firstly focused on the organic-inorganic perovskite FAPbBr₃ quantum dots.By comparing the optical properties of pure quantum dots and modified FAPbBr₃/SiO₂composite,it could be concluded that the amino groups could link at the surface of the SiO₂ silica sphere which further suppressed the aggregation of FAPbBr₃ during the nucleation process of the quantum dots.Based on this approach,it could efficiently reduce the re-growth of FAPbBr₃,therefore,the humidity stability of FAPbBr₃/SiO₂nanocomposite under room temperature conditions was greatly improved.Moreover;the fluorescence efficiency of the perovskite nanocomposite was significantly increased as well.As the silicon sphere has a higher refractive index,the light scattering property can be improved by the nanocomposites.The random lasing with a comparable low threshold?540?J/cm²?and a high quality factor?1720?was successfully detected at room temperature when excited by the two-photon femtosecond laser without any optical microcavity.On the other side,the lasing properties of the all-inorganic perovskite CsPbBr₃ quantum dots and CsPbBr₃/TiO₂ nanocompsite were further studied.As the introduced TiO₂ nanotubes could be used as excellent collectors to purify the quantum dots and keep their optical property.And due to the disordered structure of the TiO₂nanotube,the scattered light could be greatly enhanced by the tube.Two-photon random lasing with a comparable low threshold and high quatity factor at room temperature was also achieved.?3?The study on photocatalytic application of perovskite based nanocomposite.The perovskite quantum dots showed excellent optical characteristics of adjustable band gap and high electron mobility,which are the great advantages for photocatalysis.In this chapter,the FAPbBr₃ and FAPbBr₃/SiO₂ nanocomposite were employed for photocatalytic degradation of NO gas under visible light.By comparing the degradation efficiency,we found that the large-scale joint of aminated SiO₂ sphere provided a large numbers of nucleation points for quantum dots.Therefore,the stability of the quantum dots was improved while the activity area with NO gas was increased.And the photocatalytic efficiency was increased by 128%compared with pure QDs.Moreover,under the same intensity of light source and the initial concentration of NO,the photocatalytic efficiency of FAPbBr₃/SiO₂ showed 69.64%,61.21%and 56.21%respectively over the first three cycles,which demonstrating its catalytic stability.