Research On The Key Technology Of Electroluminescent Devices Based On Quantum Dots

Quantum dot is a kind of semiconductor nanocrystal that promises narrow emission linewidths,higher color purity,better photochemical stability and size-tunable emission wavelength,which make it of great application value in electroluminescent devices.Light-emitting diodes based on quantum dots(QLED)which utilize quantum dots as emitting layer,have a lot of advantages compared with organic light-emitting diodes(OLED),and they have been widely used in the field of the display industries.This paper aims to improve the performance of QLED devices.Based on the theoretical analysis of the device structure,experimental research,working mechanism and fabrication process of QLED,the key technologies of QLED such as structure-dependent performance of the device were discussed in detail.From the practical demand of improving the luminious performance of QLED,structure design,function layer thickness determination,carrier injection balance and device efficiency were studied extensively and intensively in this paper.The main works and innovations are as follows:1.The models of carrier injection and recombination of bilayer as well as improved bilayer QLED device in ideal state were establised.Influence of thickness ratio of hole transport layer(HTL)to quantum dots layer on injection current density and leakage current density of the two devices,the relationship among recombination current density,efficiency and driving voltage of the improved device were analyzed.The results show that the improved device has a favorable recombination efficiency performance when the thickness ratio of HTL to quantum dots layer is about 3:2.2.The models of carrier injection of trilayer QLED device were established.Through introducing the electron transport layer(ETL),the influence of thickness ratio of HTL to ETL on injection current density was analyzed.The results show that the recombination efficiency of hole and electron is the highest when the thickness ratio of HTL to ETL is less than 2.3.According to the distinct contact barrier between function layers,models based on the Folwer-Nordheim(FN)tunneling injection and space-charge limited current(SCLC)were simulated to analyze the injection current density of the QLED devices with different HTL and ETL thicknesses.And the optimal thickness of each function layer was confirmed.4.The fabrication processes of QLED device were studied.The advantages and disadvantages between vacuum deposition and solution spin-coating were systematically analyzed in the fabrication process of organic,inorganic and metal film.The failure mechanisms were studied and the optimum preparation process of QLED device was confirmed.5.The effects of each function layer thickness on the performance of QLED devices were studied.QLED devices with different thicknesses of HTL,ETL and electron block layer(EBL)were fabricated.The influence of different function layer thickness on current density,current efficiency and spectrum were obtained.QLED devices which used red and green quantum dots as emitting layer were fabricated,the performance of layer-by-layer quantum dots device are better than that of hybrid quantum dots device.6.The polyvinylidene fluoride(PVDF)piezoelectric film was introduced in the structure of QLED device.The QLED devices with different PVDF film thickness were fabricated.And the device has a better current density,luminance and current efficicecy when PVDF film is used as a modifying layer.