Photoelectric Property Regulation Of CsPbI₃ Quantum Dots And Its White Led/pd Device Construction

In recent years,perovskite quantum dots have become a hot spot in the field of optoelectronic device research due to their strong spectral tunability,high color purity,excellent luminous efficiency,and low processing cost.They are widely used in solar cells,photodetectors,Light-emitting diodes and other fields.After continuous research and development,the performance of light-emitting diodes with the three primary colors of red,green,and blue has been greatly improved.However,the high-efficiency red light-emitting diodes are constructed based on mixed halogens.The CsPbI₃ quantum dot light-emitting diodes with high color purity are still low inefficiency.This is mainly reflected in the unstable phase state of the CsPbI₃ quantum dots.Conversion,this conversion will damage its photoelectric performance and limit its application.Therefore,the stability optimization and photoelectric performance improvement of CsPbI₃ have become the top priority of research.Although researchers have used ion doping,passivation,and other methods to improve its performance,the mechanism of the introduction of cations and other related issues are still unclear.Further exploration and elaboration are needed.The improvement method still lacks specific theoretical guidance.Therefore,studying the mechanism of action of different cations and additives in the synthesis process is of great significance for the synthesis and regulation of high-quality perovskite quantum dots.On the other hand,some studies have reported the use of the combination ofδphase with poor luminescence performance andαto realize the application of a single material wide-spectrum electroluminescence,which not only brings breakthroughs in the field of luminescence display but also the realization of white light illumination and visible light communication brings new opportunities.Accordingly,this dissertation has conducted in-depth research and discussion on the above two aspects.The main research results are summarized as follows:（1）Aiming at the role of Zn I₂ in the synthesis of CsPbI₃ quantum dots,the mechanism of Zn I2 affecting hydrolysis in the reaction system was innovatively proposed.It was found that directly mixing Zn I₂ and Pb I_2,as the precursor solution could not introduce Zn²⁺introduced into the CsPbI₃ lattice.However,the addition of Zn I₂ would cause changes in the Lewis acid-base in the system;trigger the protonation of oleylamine,and combine with the additional iodide ion on the surface.The passivation of lead vacancies can effectively improve optical performance.Comparing different Zn I₂ additions,it is found that when the Zn I₂ addition is 30%,the synthesized CsPbI₃ quantum dots have an obvious passivation effect on the surface defects and have more excellent photoelectric properties.The light-emitting diode device constructed by it can achieve compared with the absence of Zn I₂.The efficiency of the synthesized CsPbI₃quantum dot device is improved by more than 200%.（2）Use the passivation effect of thiocyanate in NH₄SCN to optimize the surface defects of quantum dot materials,introduce different doses of NH₄SCN to further improve the optical properties of the material,improve the crystallinity of CsPbI₃quantum dots,and regulate the size and distribution of quantum dots.The passivation mechanism of CsPbI₃ quantum dots by thiocyanate is discussed.Based on the synergistic effect of Zn I₂ and thiocyanate,CsPbI₃quantum dots with excellent optical properties with low surface defect density and PLQY as high as 88.1%were prepared.Light-emitting diode devices were constructed with them as the light-emitting layer,and more than 1250 cd/m² were obtained.The ultra-high brightness and the photoelectric conversion efficiency of more than 8%effectively realize the further improvement of material performance and device performance.（3）Construct optoelectronic devices to be used in the field of visible light communication.By adjusting the humidity and processing time,the CsPbI₃ two-phase mixed film was finely adjusted to theαandδmixed phases,and successfully constructed a warm white perovskite diode light emitting device with emission of about 4531 K,and obtained more than 1600 cd/m²the high-brightness emission.In addition,when it is used in a photodetector device,the extreme value of detection responsivity is about 1.4 A/W,the average responsivity is above 0.4 A/W,and the specific detection rate is about the order of 10¹⁰ Jones.The dual function integration of the device was successfully realized.In addition,through Hex Editor Neo,FPGA,qt,etc.,a visible light communication system based on dual-function devices of light-emitting diodes and photodetectors has been constructed.The signal transmission of picture information is realized,and its application in the field of visible light communication is demonstrated.A luminescence mechanism based onα/δ-CsPbI₃ broad-spectrum emission derived from exciton emission in the transport layer is proposed.