Study On Performance Optimization Of Quantum Dot Light Emitting Diodes

Due to the advantages of adjustable luminescence spectrum,excellent luminescent color purity,high photoluminescence efficiency,favorable photochemical stability,and good thermal stability,colloidal semiconductor quantum dot materials have been used widely in display fields.Utilizing quantum dots as emitting layer,quantum dot light-emitting diodes(QLEDs)have more advantages than organic light-emitting diodes(OLEDs)such as wider color gamut,higher color rendering index(CRI),better solution processability and so on,which present a promising application in the new generation solid state light source for information display and illumination.At present,the external quantum efficiency(EQE)of QLEDs approaches to that of state-of-the-art OLEDs.Moreover,some well-known companies engaged in illumination and display at home and abroad,such as Samsung(Sumsung)and BOE(BOE),have stated that they have achieved QLEDs-based display screen samples successfully.Therefore,it is of great significance to study the optimization of QLEDs device performance and the improvement of the preparation process,which will help speed up the commercializing application.In this thesis,in order to improve the performance of QLEDs devices,the influence of electrode,device structure,preparation process of the quantum dot electroluminescent devices are discussed systematically.While the preparation and application of high performance transparent electrodes,the optimizing device structure design and the improving device efficiency are discussed in this thesis.The main research contents of this paper are as follows:1.High-performance Al-doped Zn O(AZO)transparent conductive films were prepared by magnetron sputtering(MST)and applied for the first time to green QLEDs with inverted structures.Compared to commercial ITO,AZO acts as a cathode and the Zn O nanoparticle layer as an electron transport layer are easier to form ohmic contacts and enhance the efficiency of electron injection.This conclusion has been asserted by using space charge-limited current theory,energy band and electronic state test results of UPS and XPS.2.For the first time,the top-emission green-emitting QLEDs with Al as the bottom electrode were realized by the all-solution process.High-quality anode hole injection(HIL)interface layers and functional layers were prepared by using the solution process.After weakening the microcavity effect,the emission of the near-Lambertian radiator is achieved.The emission performance of the top emission device is excellent and is applied in the modular digital display sample of the active luminescence.3.The red and blue QLEDs are prepared for developing three primary colors device.A laminated transparent film(Sn O2/Ag/Sn O2)is manufactured by SMT,and the red QLEDs employing this laminated electrode demonstrate a great improvement in electroluminescence.Blue QLEDs are developed by inverted structure and some preliminary results are achieved.4.The flexible QLEDs based on PET has been explored and studied.The green flexible QLEDs with better performance have been also prepared by the full solution processing method and its flexural properties have been studied.At the same time,this thesis explored the preparation of the new perovskite light emitting diode.The inorganic perovskite light emitting diode is prepared by solution method.The maximum brightness of the device is over 55000 cd/m2,the maximum current efficiency is over 20 cd/A,and the comprehensive performance is superior.