Research On Efficient And Stable Quantum Dot Light Emitting Diode Based On Double Electron Transport Layer

Quantum Dot Light-Emitting Diodes(QLEDs)have broad application prospects in the field of new generation lighting and display because of their advantages of solution processing,good stability,high color purity,and continuous adjustment of luminous colors with the size of quantum dots.It has broad application prospects in the field of new generation lighting and display.On this basis,quantum dot light emitting diodes(QLEDs)has attracted more and more attention and has made great progress.It is expected to become next mainstream technology of solid-state lighting and display.However,the efficiency of QLEDs is low and the service life is short,which limits the further commercial application.At present,poly(3,4-ethylenedioxythiophene):polystyrene sulfonate(PEDOT:PSS)is generally used as hole injection layer,TFB as hole transport layer,quantum dots(QDs)as a luminescent layer and zinc oxide nanoparticles(Zn O NPs)as electron transport layer in standard red QLEDs constructed by full solution method.However,the frequently used electron transport layer Zn O NPs has two problems:(1)due to the defective state of Zn O NPs themselves,the leakage hole current is large,and the charge cannot be effectively recombined in the luminescent layer of quantum dots,(2)the energy level barrier between Zn O NPs and QDs light-emitting layer is small,and the excess electrons cause the imbalance of carrier injection.In order to solve the problems in QLEDs optoelectronic devices,this paper proposes to achieve more efficient carrier management through the strategy of two electron transport layers.The inorganic materials of cerium oxide(CeO_x)with suitable energy level and good electrical conductivity were selected as the research object to study the influence of the two-electron transport layer in the optoelectronic device.The inorganic materials of cerium oxide(CeO_x)with suitable energy level and good electrical conductivity were selected as the research object to study the influence of double electron transport layer in optoelectronic devices.In the preparation of optoelectronic devices,Zn Cd Se/Zn S core and shell red quantum dots are used as the light-emitting layer,and CeO_x and Zn O inorganic material laminations are used as the electron transport layer,which improved the defect state of QDs/Zn O interface,appropriately improves the electron injection barrier,promotes the charge injection balance,and improved the performance and stability of optoelectronic devices at the same time.The main work of this paper is summarized as the following two parts:(1)Synthesis of n-type inorganic semiconductor material CeO_xAs an n-type semiconductor material,CeO_x inorganic material not only has the advantages of simple synthesis and green environmental protection,but also has good chemical stability,which can be placed in the environment for a long time and is not easy to be eroded by water and oxygen.CeO_xinorganic material was synthesized by liquid-solid-liquid three-phase solvothermal method and surface modified.Finally,the modified CeO_x inorganic nanoparticle material could be well dispersed in methanol solvent.CeO_xinorganic materials were synthesized and characterized under different reaction conditions.The main characterization methods are x-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),ultraviolet-visible absorption spectroscopy(UV-Vis),transmission electron microscopy(TEM),atomic force microscopy(AFM),and ultraviolet photoelectron spectroscopy(UPS).(2)Application of n-type CeO_x semiconductor materials in QLEDs optoelectronic devicesConsidering CeO_x is an n-type inorganic semiconductor material with good chemical stability,it can be used as electron transport material in QLEDs optoelectronic devices.As QDs is easily eroded by water and oxygen in the environment and there are high density defect states at the QDs/Zn O interface,CeO_x/Zn O laminated structure is adopted as the electron transport layer of QLEDs photoelectric devices.The experiment mainly investigated the effect of CeO_x inorganic film on the device performance under different synthesis conditions,the performance of QLEDs prepared by this method has been improved to a certain extent.After experimental optimization and exploration,the brightness of the optoelectronic device under the final conditions is increased by about 18.3%compared with the standard optoelectronic device,and the EQE of the optoelectronic device under the condition is increased by about 58.9%compared with the standard optoelectronic device.More importantly,the QLEDs optoelectronic devices constructed by the dual electron transport layer have good working stability,and the life of the optoelectronic device under this condition is about 9 times higher than that of the standard optoelectronic device.