Study And Regulation Of The Fluorescence Properties In Organometallic MAPbBr₃ Perovskite Single Crystals

The perovskite materials,as a new kind of photoactive materials,own excellently optical and electeical properties due to the special crystal structure.Therefore,they have been widely utilized in a large amout of key equipment needing the photoactive materials in various fileds,such as photoelectric detection,photovoltaic devices,light emitting diodes,and photoelectric catalysis,etc.The perovskite crystal material can be grown by the convenient and cheap solution method.So it has huge potential and advantages in both commercialization and large-scale device applications.Indeed,the traditional methods of solution growth methods,including inverse temperature crystallization method,slow evaporation crystallization method and inverse solvent crystallization method,can synthesize high quality perovskite crystal materials.However,these traditional methods have some limitations in studying the energy conversion process and kinetic process of perovskite crystals growth.But the laser,as a kind of energy source with focused energy and easily adjustable parameters,has potential application prospect in studying the crystal growth process and synthesizing high quality perovskite crystal materials.Based on the above research status and prospects,firstly this research mainly studies the experimental methods of laser assisting synthesis of perovskite crystal and its energy conversion mechanism.Furthermore,this research studies the dynamic mechanism of laser assisting synthesis of perovskite and its applications in wide band photoelectric detection.The main research work in this paper is as follows:1.Study on the theory of perovskite crystal nucleation based on laser assisting synthesis of CsPb Br₃ nanocrystals.Based on the second law of thermodynamics,this research studies the change of Gibbs free energy in the process of perovskite crystals nucleation and the critical conditions for the formation of stable crystal nuclei are studied.An energy conversion model for pulsed laser assisted synthesis of CsPb Br₃ quantum dots is established.The energy conversion process in laser-assisted nucleation of perovskite nanocrystals is quantitatively studied.A device for the synthesis of CsPb Br₃ nanocrystals by laser-assisted reverse temperature crystallization（LA-ITC）method is established,and high-quality monodisperse cubic CsPb Br₃ nanocrystals are synthesized.Controllable synthesis of perovskite nanocrystals is achieved by adjusting laser parameters.In addition,perovskite nanocrystals can be synthesized to meet different application requirements by controlling the synthesis conditions and precursor solution components.2.Study on laser-assisted synthesis of MAPb X₃ polycrystalline thin film and single crystal thin film and its mechanismBased on the interface dynamics theory,the growth dynamics model of cubic phase perovskite crystal is studied.A device for laser-assisted annealing（LA-AC）of perovskite polycrystalline thin film and laser-assisted reverse temperature crystallization（LA-ITC）of perovskite single crystal thin film is established.High quality MAPb I₃ polycrystalline thin film and MAPb Br₃ single crystal thin film are synthesized by this method.Compared with the traditional heat auxiliary annealed polycrystalline thin film method,LA-AC method utilizes the energy of the focused laser energy source.The interface and internal stress caused by synchronous growth of multiple embryos and thermal expansion coefficient difference between the perovskite film and the substrate can be avoided,which is against carrier transmission.High quality single crystal wafer of MAPb Br₃ is synthesized by combining space limited method and the LA-ITC method.The research results show that the spatial size of synthesized single crystal wafer can be adjusted from tens of microns to millimeters,and the thickness can also be adjusted from hundreds of nanometers to ten microns by controlling the laser power,the action time and the concentration of the precursor solution.The high quality synthesized single crystal wafers have a great prospect in the application of photodetectors.3.Study on the application of Ag₂S-QDIP heteroperovskite crystals synthesized by LA-ITC method in wide-band response photodetectorsSilver sulfide（Ag₂S）quantum dot doped MAPb Br₃ perovskite single crystal（Ag₂S-QDiP）is synthesized by laser-assisted reverse temperature crystallization（LA-ITC）method.Based on the synthesized Ag₂S-QDiP doped single crystal,a horizontal structure wide band responsive photodetector is prepared.We have observed that the absorption spectrum of perovskite single crystal material can be widened to near infrared band after adding Ag₂S QDs.And the introduction of Ag₂S QDs can balance the generation and transport of electrons and holes in Ag₂S-QDiP matrix.The mobility of the electron decreases about 1%,and the mobility of the hole increases by a factor of one.The mobility of the tuned matrix can be attributed to an increase in the scattering probability of defects.The carrier migration properties of equilibrium have potential for the development of bipolar electronic devices based on heterogeneous single crystals.The as prepared photodetector,based on the Ag₂S-QDiP heterocrystal wafer,shows good photoresponse characteristics in the visible band（532 nm）and near infrared band（1064 nm）.In summary,this paper elaborates the process of energy conversion and growth kinetics during the course of the perovskite crystal nucleation and growth starting from the prespective of second law of thermoelynamics and and the dynamics theory of the interface.Sencondly,this paper elaborates the thermodynamic and kinetic models of laser-assisted perovskite crystal nucleation and growth have been established by three-dimensional conduction model simulating the laser energy and temperature distribution models.The device for synthesizing various morphs perovskite materials such as quantum dots,polycrystalline thin films and single crystals is established in this paper.A doping strategy is elaborated based on the LA-ITC method in this paper,and the synthesized Ag₂S-QDiP matrix shows vis-NIR broadband photoresponsive property.Most valuable of all,the paper provides a new strategy for the preparation of high quality perovskite materials and photodetectors.