Hole Carrier Regulation And The Mechanisms For High Performance Deep Blue Organic-Light Emitting Devices

At present,organic light-emitting devices(OLEDs)have attracted a great deal of interest between researchers and industry professionals.However,blue organic electroluminescent devices have always been the soft underbelly in the development of OLED full color.In particular,the deep blue fluorescent device required for the current color gamut of the product(requires its color coordinate CIEy<0.06),its performance,lifetime and other properties have been difficult to be comprehensively improved.Therefore how to improve the performance of this type of device is still a critical issue and challenge in this field.Based on the purpose of improving the performance of such devices we have conducted in-depth research on the injection and transmission of carriers and the mechanisms involved.This paper will use the hole injection layer,hole transport layer and electron blocking layer as the target layers to study the influence mechanism of hole carriers on the performance of deep blue OLED devices:1 The effects of different concentration ratios of P-type dopants on hole injection capability and device performance were investigated.The P-dopant concentrations were set to 0%1%,3%,5%,and 7%,respectively.The performance of the device was characterized.It was found that as the P-doping became higher,the device driving voltage decreased the efficiency decreased,the lifetime increased,and the doping concentration was increased.The blue factor BI value of the device with 7%of the device concentration is reduced by 7.4%,and the lifetime of the device LT95 is increased by nearly 42.9%.2.The effect of hole transport materials with different properties on device performance was studied.Using three materials as the hole transport layer to prepare the contrast device,optimize the device level structure matching,characterize the device performance difference,use the carrier balance theory and the position of the composite light-emitting region to study the chromaticity of the device in the process,The change rule of efficiency,life and other properties finally reduced the driving voltage by 0.24V,the highest BI value by 20.8%,and the longest LT97 lifetime by 73.3%,which provided the direction for the selection of the hole transport layer during the debugging process.3.The mechanism of the influence of the electron blocking layer on the device performance was studied.Considering that for the current blue light fluorescent system BH partial electron type,the exciton composite light-emitting region is closer to the HTL layer and is located substantially at the interface between the light-emitting layer and the electron blocking layer,so the electron blocking layer is crucial for the blue fluorescent device.In this research work,we first verified the functionality of the EBL layer,and found that the insertion of EBL can increase the device BI value by 23.5%and the LT95 lifetime by 35.1%.Then,the devices with different characteristics of EBL materials were compared and characterized.Summarize the influence of different material properties of EBL on device performance,and obtain a material with high triplet energy level(T1)and stable structure as EBL layer,which can improve device efficiency and lifetime at the same time.Finally,the thickness of the layer was optimized and it was found that the device performance was optimized when the EBL thickness was set at 5 nm.