Research On The Properties Of All Inorganic Perovskite Quantum Dots And Light Emitting Diodes

Perovskite quantum dots（QD）have been widely studied and applied in recent years for their excellent characteristics such as high fluorescence quantum yield,high color purity,narrow half-wave width and so on,scientists have made series of research progress in this field.However,there are many defects on the surface of perovskite quantum dots,which is one of the main limiting factors for their application.In addition,the overall performance of Light-Emitting Diodes（LED）based on perovskite as the light-emitting layer is still at a low level,in which the charge injection as well as the quality of the light-emitting layer are the key limiting factors to improve the improvement the device performance,thus it can be optimized from device manufacturing technology and its structure.This thesis focused on the excellent luminescent properties of Cs Pb Br₃perovskite quantum dots,and studied the improvement of performance of Quantum Dots light-emitting Diodes（QLED）devices from the preparation process and device structure,and then,fabricated perovskite QLED devices with high efficiency and brightness.The main research content were as follows:1.Preparation process of quantum dot and device:Cs Pb Br₃ quantum dots were synthesized by Ligand-assisted Reprecipitation（LAPR）at room temperature.The average size of the obtained quantum dots was approximately 5 nm,and the quantum yield was85%.Through the cleaning times of the quantum dots and the annealing process of the light-emitting layer of the device,the perovskite QLED with the device structure of ITO/PEDOT:PSS/PTAA/Cs Pb Br₃ QD/TPBi/Li F/Al was prepared.The results showed that the stability of the solution and charge injection could be balanced by 2 cleaning times of quantum dots,and the emitting layer was not annealed which made the devices had good performance.The maximum brightness of the perovskite QLED was 1405cd·m^-2 and its external quantum efficiency was 0.6%.The results above laid a foundation for further improving the performance of perovskite quantum dot light-emitting devices.2.Study on Hole Transport layer（HTL）materials and emitting layer thickness:green perovskite QLED with the structure of ITO/PEDOT:PSS/HTL/Cs Pb Br₃QD/TPBi/Li F/Al were prepared by using 3 common hole transport layers:PVK,PTAA and TFB,and then compared the advantages and disadvantages of them.The results showed that PTAA has excellent performance in charge transfer and low turn-on voltage,so PTAA was used as the hole transport layer to optimize the thickness of the light-emitting layer.The maximum brightness of the optimized perovskite QLED was4531 cd·m^-2,the current efficiency was 14.4 cd·A^-1,the power efficiency was 14.1lm·W^-1,and the external quantum efficiency was 4.28%.3.Study on solution modification treatment of hole injection layer:Toluene and ethylene glycol solution were used to treat the hole injection layer,PEDOT:PSS film.It was found that toluene treatment improved the ability of hole transport,while ethylene glycol treatment showed improved conductivity but hydrophobicity,which was not conducive to the spin-coating of the next layer.The structure of ITO/PEDOT:PSS/PTAA/Cs Pb Br₃ QD/TPBi/Li F/Al perovskite QLED devices were prepared.The results showed that the maximum luminance and external quantum efficiency of PEDOT:PSS devices treated with toluene reached 31140 cd·m^-2 and 4.98%,respectively,which are 48%and 19%higher than that of untreated devices.However,the performance of devices treated with ethylene glycol was lower than that of untreated devices in all aspects.