Low-Dimensional Halide Perovskite Structure:Controllable Synthesis And Its Photoelectric Applications

The novel halide perovskite materials have achieved worldwide attention and become the next generation due to their outstanding photoelectric performance in solar cells,light-emitting diodes（LEDs）,photoelectric detection,and many other photoelectric fields.One of the most competitive optoelectronic semiconductor materials.Compared with traditional semiconductor materials,the development time of halide perovskite materials is still short,and its actual application still faces many problems.For example,perovskite due to its ionic crystal characteristics and rapid growth kinetics during synthesis,It brings great challenges to the dimensional control and controllable synthesis of its crystal structure.In addition,this ionic characteristic also provides a key factor for the instability of the perovskite structure.The ion migration and phase transition of the perovskite material during work The problem is the current bottleneck restricting the application of perovskite materials.Therefore,it is very important to study the controlled synthesis of perovskite materials,and to design and control the morphology and structure of perovskite materials according to the needs of different optoelectronic devices,not only is conducive to the improvement of device performance,but also maximizes the material’s own Performance advantages,and further deepen the understanding of new materials,which is of great value for accelerating the practical application of new perovskite materials;in addition,solving the problem of material stability is also a key element to promote the new materials to production applications.This dissertation took all-inorganic halide perovskite as the research object,developed several low-dimensional perovskite nanomaterials,studied their controllable synthesis methods and photoelectric properties,and used different low-dimensional materials’structure and performance characteristics Explored and developed its application in optoelectronic devices with different functions,and also proposed a strategy to improve the stability of perovskite materials.The main research results are as follows:（1）Synthesis of all-inorganic perovskite two-dimensional nanosheets and application of flexible photodetectors.The two-dimensional all-inorganic perovskite nanosheets were synthesized for the first time by the improved heat injection method.They have high crystalline quality,uniform morphology and size,and are large and thin.The side length can reach more than 1μm and the average thickness is only 3.3 nm,and has good dispersion in organic solvents,suitable for various solution processes to build various optoelectronic devices.This ultra-large and thin two-dimensional sheet structure is not only conducive to carrier transport,but also very advantageous in flexible electronic devices.We used a solution process to construct a flexible photodetector based on ultra-thin CsPbBr₃ nanosheets,showing calcium The application potential of titanium ore two-dimensional nanosheet materials in various large-area flexible optoelectronic devices processed in the future.（2）Synthesis of perovskite one-dimensional nanotubes and the application of miniature photodetectors.A self-template synthesis method was proposed.For the first time,a one-dimensional halide perovskite nanotube structure with a diameter of about 300 nm and a maximum length of 100μm was prepared.By constructing a visible light detector based on a single nanotube,the potential of its application in microelectronic devices or array devices was discovered.In addition,the unique hollow tubular structure of nanotubes is beneficial for loading other nanoparticles to enhance or develop new properties.By loading Au particles and PbS nanoparticles,we have further enhanced the detection performance of single nanotube detectors.（3）The synthesis of perovskite one-dimensional nanorods and the application of electroluminescent LEDs.A room temperature synthesis process is proposed to synthesize a single morphology and uniform size CsPbBr₃ nanorod structure in one step,which solves the problem of the difficulty in directly synthesizing the perovskite nanorod structure.The synthesized CsPbBr₃ nanorod has a PL half-width of only 18 nm,and PLQY can reach more than 90%,and the spectrum of the entire visible light range can be obtained through anion exchange,showing excellent luminescent properties.The electro-LED constructed with CsPbBr₃ nanorods as the luminescent layer can achieve a device EQE of 9.1%,the highest The brightness is 1815 cd/m² and the maximum current efficiency is 31 cd/A.It shows excellent photoelectric performance and also shows the huge application potential of one-dimensional perovskite nanorod materials in light-emitting diodes.（4）Aiming at the problem of poor stability of perovskite materials,a 0-dimensional perovskite structure Cs₄PbBr₆ natural stable structure is used to propose a perovskite two-phase structure system CsPbBr₃@Cs₄PbBr₆ to improve the stability,and by coating more stable Si O₂The shell layer further improves its storage stability,light stability and thermal stability.It still maintains good luminous behavior when stored in the atmospheric environment for more than two months,and it only appears weak fluorescence attenuation after repeated heating and cooling 50 times between RT and 150℃.The improved stability of the CsPbBr₃@Cs₄PbBr₆/Si O₂ composite structure exhibits some unique optical properties,which can not only be excited by ultraviolet light to exhibit down-conversion luminescence characteristics,but also can be excited by near-infrared femtosecond lasers based on two-photon Absorbing up-conversion luminescence characteristics,and due to its thermal stability,it shows a reversible disappearance-recovery response to temperature rise-fall changes.We use these interesting fluorescence characteristics to develop perovskite materials in multiple The application of fluorescent anti-counterfeiting,its security is greatly improved compared to traditional fluorescent anti-counterfeiting materials.