Controllable Synthesis Of One-dimensional Inorganic Perovskite Nanocrystals And Their Photoluminescence Properties

In recent years,all-inorganic perovskite CsPbX₃(X=Br,Cl,I)nanocrystals have shown extremely high application potential in solar cells,light-emitting diodes,photodetectors and other fields due to their excellent photoelectric properties.Among various forms of semiconductor materials,one-dimensional(1D)nanostructures often have unique advantages,such as long carrier lifetime,low exciton loss,efficient carrier transport,and anisotropic light emission.The controllable synthesis of 1D inorganic perovskite nanocrystals,in-depth study on the formation process of the 1D nanocrystals,and the realization of luminescence regulation on these nanocrystals will greatly promote the development of perovskite materials and accelerate the practical application of perovskite materials.In this thesis,we have realized the controllable synthesis of 1D inorganic perovskite nanocrystals(nanorods and nanowires)by a solvothermal method.The influence of the synthesis process on the photoluminescence(PL)properties of the nanocrystals have been studied in detail.The application of as-prepared nanowires in the field of optoelectronics have also been explored.The main contents are as follows:(1)The controllable synthesis of ultrafine CsPbI₃ perovskite nanorods has been achieved by a solvothermal method.The PL properties of the CsPbI₃nanorods have also been studied.The as-prepared CsPbI₃nanorods have ultrafine diameters(?4.6 nm)with uniform sizes,which show narrow full width at half maximum(?29 nm)and good luminous efficiency.The effects of solvothermal reaction times and temperatures on the morphology and PL properites of nanocrystals are studied in detail.By changing of the solvothermal reaction times,precise regulation on the sizes and PL properties of the nanorods can be achieved more effectively.Due to the strong quantum confinement effect,the slight change in the diameters of the nanorods would cause a large change in their PL emission(609-627 nm).In addition,the stability of the nanorods have also been tested.The structural transformation of the sample after the removal of ligands indicates the importance of the presence of surface ligands for the structural stability of CsPbI₃ nanorods.(2)CsPbBr₃ nanowires with high aspect ratio have been synthesized by a solvothermal method.The effects of reaction time,amounts of ligands,and types of ligands on the nanocrystalline structure,morphology,and PL properties of the samples have been studied in detail.The dimensional regulation of CsPbBr₃ nanocrystals(nanowires,nanoparticles,microflakes)could be achieved by changing the amount of oleic acid and oleamine ligands.By using short-chain ligands(dodecylamine)insteading of oleylamine ligands,nanowires with downsized diameters(?10 nm)can be synthesized.The studies on the ligands have shown that the use of ligands with appropriate amounts plays a decisive role on the formation of perovskite structures and the 1D directional growth of nanocrystals.(3)Flexible photodetectors based on CsPbBr₃ nanowires have been constructed by using two different kinds of fabrication processes(spinning process and spinning process).The current-voltage(I-V)test,time response(I-t)test and flexibility test are carried out for the photodetectors,and the performance parameters such as detectivity,switching ratio and response speed of the photodetectors are obtained.The photodetector prepared by the spin coating process shows the detectivity of 1.9×10¹¹ Jones,switching ratio of 2.2×10²,and fast response time of less than 3 ms.In addition,the device has good resistance to bending.Interestingly,the photodetector prepared by the spinning process shows significantly enhanced photoelectric performance.The highest detectivity rate is 4.5×10¹¹ Jones,and the switching ratio reaches 2.3×10³,which can be attributed to the more efficient carrier transport brought by the aligned alignment of the nanowires.