Fabrication Of Methylamine Lead Bromide Perovskite Polyhedral Microcrystals And Their Lasing Applications

In recent years,organometallic halide perovskites have made important progress in applications such as electroluminescent devices,photovoltaic conversion devices,and light/radiation detection with their excellent photoelectric properties.In particular,as an excellent optical gain medium,the organometallic halide perovskite has the advantages of convenient shape control,simple preparation process,and direct band gap adjustment.How to further improve the performance of perovskite laser devices,such as lowering the laser threshold and adjusting the laser emission mode is one of the main research directions of the current research.In this paper,methylamine lead bromine perovskite?CH₃NH₃PbBr₃?was used as the research object.The perovskite crystal with polyhedral structure was synthesized for the first time by optimized solution method,and the growth mechanism was deeply discussed.And laser performance control.The specific work is as follows:CH₃NH₃PbBr₃ polyhedral particles were synthesized by a solution-precipitation method to make a polyhedral cavity.The polyhedral particles of CH₃NH₃PbBr₃were obtained by dropping a certain concentration of CH₃NH₃ Br solution?solvent:isopropanol,IPA?into PbBr₂solution?solvent:N,N-dimethylformamide,DMF?.Further research shows that the concentration of CH₃NH₃ Br solution plays a key role in the formation of CH₃NH₃PbBr₃polyhedron structure:the ultra-low concentration of CH₃NH₃ Br solution is conducive to the formation of CH₃NH₃PbBr₃crystal polyhedron structure. By changing the mixing way,it was found that CH₃NH₃PbBr₃crystals were more likely to form a cube structure under the condition of violent mixing,which was due to the accelerated reaction rate caused by violent mixing.At the same time,the intense mixing intensifies the erosion of the solution to the crystal,so that some hollow structures are formed.Pumping with a femtosecond laser with a wavelength of 400 nm,the CH₃NH₃PbBr₃polyhedron can achieve laser emission,and the smaller structure can also achieve a single mode laser with a quality factor as high as 1400,which further indicates that the CH₃NH₃PbBr₃polyhedron particles synthesized by solution-precipitation method have higher crystal quality.The polyhedral tapered microwires of CH₃NH₃PbBr₃ were synthesized by an improved anti-solvent vapor phase diffusion crystallization method.The PbBr₂ film was immersed in a relatively high concentration of CH₃NH₃ Br solution to form a CH₃NH₃PbBr₃polycrystalline film.Then the precursor solution was added to the film and the CH₃NH₃PbBr₃polyhedral tapered microwires were grown on the film by the anti-solvent gas-phase diffusion crystallization method.Further,we found that whether the obtained CH₃NH₃PbBr₃polycrystalline film contains PbBr₂plays a crucial role in the morphology of the final CH₃NH₃PbBr₃particles.In addition,CH₃NH₃PbBr₃microwires were synthesized by anti-solvent gas-phase diffusion crystallization method through the regulation of the crystallization process of CH₃NH₃PbBr₃by octylamine.A 400 nm femtosecond laser was used to pump the CH₃NH₃PbBr₃microwires and CH₃NH₃PbBr₃polyhedral tapered microwires,respectively.Under the condition of uniform pumping,the F-P mode priority resonance of CH₃NH₃PbBr₃microwire is usually reflected in multi-mode laser emission.The axial end faces of CH₃NH₃PbBr₃polyhedral tapered microwires are not smooth,which makes the F-P mode suppressed.For CH₃NH₃PbBr₃polyhedral tapered microwires,the WGM laser of transverse section is prior to appear.Due to the small volume of cavity mode,the laser generally has the single mode characteristic.This paper provides the synthesis methods of perovskite polyhedral particles and perovskite polyhedral tapered microwires,reveals the growth mechanism of two different polyhedral perovskite structures,and shows the application of polyhedral perovskite in the field of laser devices.