The Effect Of Spacer Layer On The Performance Of OLED Devices

As having advantages of active light emission,wide viewing angles,soft and natural light,green environmental protection,energy saving,flexible display,and radiation-free,Organic light-emitting devices(OLEDs)have received more and more attention and applications.However,the further development of OLED is restricted due to the problems of low device efficiency and poor color stability.In this thesis,we develop a white OLED device with double light-emitting layer structure.By exploring the effect of material properties and thickness of spacer layer on the performance of OLED device,we use a new material SO as spacer layer,to study the performance of hybrid white OLEDs and all-phosphorescent white OLEDs.Finally,the efficiency and color stability of OLED devices are improved.The main works includes:(1)The effect of 4 nm hole-transporting material TAPC and electron-transporting material Bphen as spacer layer on device performance is studied.Compared with OLED device without spacer layer,the experimental results show that spacer layer can improve the device's luminous efficiency and affect light emission color.Different transmission characteristics of spacer layers have different effects on the device:the maximum current efficiency of the device with the TAPC spacer layer is 10.90 cd/A,and the maximum power efficiency of the device with the TAPC spacer layer is 9.61 lm/W,which makes the light color of the device more bluish;the maximum current efficiency of the device with the Bphen spacer layer is 11.76 cd/A,and the maximum power efficiency of the device with the Bphen spacer layer is 8.88 lm/W,which makes the light color of the device more yellowish.(2)The effect of CBP spacer layer with different thicknesses of 2,4,and 6 nm on device performance is studied.Compared with OLED device without spacer layer,the CBP spacer layer is used to improve device performance and color stability.When the thicknesses of CBP is 4 nm,the device has a maximum current efficiency of 45.13 cd/A,a maximum power efficiency of 30.70 lm/W,and the color coordinate change is(0.05,0.04)at a current density of 0.1 mA/cm2-20 mA/cm2.(3)The effects of CBP spacer layer with different thicknesses of 1,2,3,and 4 nm on modified hybrid white OLED device performance is studied.From the experimental results,it can be known that when the CBP thickness is 3 nm,the hybrid white OLED device has a maximum current efficiency of 24.79 cd/A,a maximum power efficiency of 20.12 lm/W.From 5 mA/cm2 to 80 mA/cm2 the color coordinate change is only(0.01,0.01).It has high color stability in a certain current density range.(4)The effect of SO spacer layer with different thicknesses of 1,2,3,and 4 nm on hybrid white OLED device performance is studied.Compared with the optimal device of CBP spacer layer,the experimental results show that SO is an electron transporting material.The device with 1 nm SO spacer layer has the best performance,the maximum current efficiency is 26.55 cd/A,and the maximum power efficiency is 25.06 lm/W.From 0.1 mA/cm2 to 80 mA/cm2 the color coordinate change is(0.03,0.02).Compared with CBP as the spacer layer,SO as the spacer layer has higher performance and color stability.(5)We further doped the electron-transporting material SO with the hole-transporting material TCTA as spacer layer,and keep the thickness at 1 nm.The effect of SO:TCTA four doping ratios of 1:1,7:3,4:1,9:1 hybrid white OLED device performance is studied.When the SO:TCTA doping ratio is 9:1,the maximum current efficiency is 31.60 cd/A,and the maximum power efficiency is 30.16 lm/W.The maximum external quantum efficiency is 11.6%,and the color coordinate change within the current density change of 0.1 mA/cm2 to 80 mA/cm2 is only(0.02,0.01).The color coordinate drift is more smaller and the color stability is more better.(6)We apply SO and SO:TCTA spacer layers to all-phosphorescent white OLED devices.The effect of the thickness of the SO spacers and the doping ratio of the SO:TCTA spacers on the all-phosphorescent white OLED devices are studied in order.As a result,when the thickness of SO:TCTA spacer layer is 1 nm and the doping ratio is 7:3,the maximum current efficiency is 52.92 cd/A,and the maximum power efficiency is 43.97 lm/W,and the maximum external quantum efficiency is 19.88%.The color coordinate change is only(0.01,0.01)within the current density range of 0.1 mA/cm2 to 80 mA/cm2.An all-phosphorescent white OLED device with high color stability is obtained.