Study On Metal Oxide Materials And Structure Optimization Of Quantum Dot Light Emitting Diodes

As a part of nanocrystalline semiconductors,colloidal quantum dots are characterized by their adjustable energy bands,narrow spectral half widths,wide illumination wavelengths,and high fluorescence quantum yields,and they have been widely used in the fields of solar cells,photodiodes,light emitting diodes,biological labels,and biological detection.Quantum dot light-emitting diodes(QLED)based on quantum dot semiconductor materials inherit the unique photoelectric properties of quantum dot materials,with high color purity,high resolution,wide color gamut,and full-band illumination,it is the most promising display technology after LCD and OLED.In order to improve the luminous efficiency of QLED devices,the dissertation studies the optimization of electron transport layer,transition metal oxides as hole injection layer and light extraction technology.The main work and innovation of the thesis are as follows.1.A novel hybrid electron transport layer consisting of zinc oxide and zinc magnesium oxide nanoparticles was developed,which increased external quantum efficiency of the QLED to 13.5%.And they were 1.29and 1.33 times that of pure zinc oxide and zinc magnesium oxide devices,respectively.The brightness was also increased to 22100 cd/m~2.By measuring the current density-voltage relationship of the single electron devices and transient fluorescence spectra of quantum dots,it was found that the hybrid electron transport layer performed better than conventional zinc oxide and magnesium-doped zinc oxide nanoparticle layers.2.Molybdenum oxide nano-particles were successfully prepared using a low-temperature solution method,and used as hole injection layer of the QLED.The experimental results show that the molybdenum oxide film exhibits an energy level matching with poly-TPD at an annealing temperature of 100°C.The molybdenum oxide can significantly improve the hole injection.The highest external quantum efficiency of the device was 11.6%.At a bias of 10 V,the maximum brightness of the device reached 27100 cd/m~2.3.A simple,low-cost,and repeatable wet chemical etching process was used to roughen the surface of the ITO glass substrate,resulting in a large number of pit microstructures.The rough substrate surface reduced the interfacial reflective pattern of the substrate/air and suppressed light waveguide mode.Compared with non-etched devices,QLED with rough surfaces had a 12%increase in the maximum external quantum efficiency,a 1.8-fold increase in maximum brightness,and a half reduction in edge-emission light.