Preparation Of Inorganic Perovskite Nanocrystals And Its Application In Light Emitting Devices

Inorganic perovskite materials are endowed with better stability in structural and optical properties.Moreover,the nano-scale inorganic perovskite materials with quantum size effect have attract great interests due to their narrow full width at half maximum?FWHM?,high quantum yields of up to 90%and adjusted fluorescence spectrum which can be tuned in the entire visible wavelength range.These excellent properties demonstrate their great potential application in a wide variety of optoelectronics,such as light-emitting diodes,photodetectors and lasers.Nevertheless,there are still many problems in practical applications of inorganic perovskite nanomaterials.The synthesis of inorganic perovskite nanomaterials is usually conducted with organic ligands.Therefore,the films of quantum dots contain a large amount of insulating organic ligands,which reduces the charge-transport property of the films when they are applied to optoelectronic devices.What's more,the low environmental stability of inorganic perovskite nanomaterials also limits their diverse applications.Moreover,their potential auxiliary functions in the field of optoelectronics have yet to be explored.Regarding the issues above,this thesis aims to control the ligand density and improve the stability of inorganic perovskite quantum dots.Consequently,the performance of inorganic perovskite quantum dots based light-emitting diodes has been improved by optimizing the post-treatment of inorganic perovskite quantum dots.The stability of inorganic perovskite quantum dots has been enhanced by embedding the quantum dots in a polymer matrix,and flexible white light-emitting diodes based on inorganic perovskite quantum dots have been constructed.In addition,the potential auxiliary function of inorganic perovskite quantum dots in the field of optoelectronics was also explored.Polymer/inorganic perovskite nano hybrid materials were prepared,and high performance polymer light-emitting diodes were obtained.The major results in this thesis are as follows:?1?An optimization strategy for post-treatment of inorganic perovskite quantum dots was proposed,which effectively controlled the density of surface ligands and improved the efficiency of light-emitting diodes based on inorganic perovskite quantum dots.Firstly,CsPbBr₃ quantum dots were synthesized via hot-inject method.High-quality products with highly monodispersity and dense arrangement were obtained.The agglomeration mechanism of CsPbBr₃ quantum dots was discussed and the centrifugation method and solvent combination in the post-treatment process were optimized.The device performance of light-emitting diodes based on CsPbBr₃ quantum dots obtained before and after optimization was compared.After optimization,the maximum luminance and current efficiency of the device are up to 3592 cd/m² and 5.0 cd/A,respectively.The luminance and current efficiency were enhanced 7.1 times and 9.6 times,respectively.This work proved that the performance of CsPbBr₃ quantum dots based light-emitting diodes can be significantly improved via proper post-processing methods.?2?To improve the environmental stability of inorganic perovskite quantum dots,polymer matrix was utilized to protect them,and flexible white light-emitting diodes based on inorganic perovskite quantum dots were constructed.Their applications in flexible electronics were expanded.Firstly,free-standing CsPbX₃ quantum dots/polymer composite films with large area,uniform light emission,transparency,flexibility,adjustable fluorescent color and good hydrothermal stability were prepared by post-packaging method.The composite films exhibit desirable hydrothermal stability.In addition,flexible white LEDs based on inorganic perovskite quantum dots were prepared by integrating self-made flexible blue organic light-emitting diodes as backlight panels and CsPbBr₃/polymer composite films as the color conversion films.?3?A preparation method of conjugated polymer/inorganic perovskite nano-hybrid material was proposed,and high performance polymer light emitting diodes were obtained based on the hybrid material.Inorganic perovskite quantum dots were introduced into poly?9,9-dioctylfluorene??PFO?by physical doping method to prepare PFO/inorganic perovskite nano-hybrid materials.It was proved by UV-visible spectroscopy and fluorescence spectroscopy that the?-phase of PFO was produced in the film of the hybrid material.The content of?-phase of PFO increases as the content of inorganic perovskite quantum dots increases.PLED based on PFO/inorganic perovskite nano-hybrid material containing 40%CsPbBr₃ quantum dots exhibited the best performance.The maximum current efficiency and luminance of the device are up to 5.0 cd/A and 2200 cd/m²,respectively.It is proved that the PFO/inorganic perovskite nano-hybrid material has higher carrier transport capability and the performance of the polymer light-emitting diodes are greatly improved.At the same time,this work also reveals the potential auxiliary function of perovskite quantum dots in the field of optoelectronics.