Effect Of Electrode Modification On Performance Of Organic Light-Emitting Devices

Organic light-emitting devices?OLEDs?have many advantages such as self-emitting,wide viewing angle,fast response time,and a wide operating temperature range,and considered to be the most promising new generation of display technologies and have been rapidly developed.Although OLEDs have practical applications,there is still large space to improve their efficiency and lifespan.Electrode modification is a method that can effectively improve the efficiency and lifetime of the device.For this reason,the main research this article is as follows:1.Organic p-n junction composing of PEDOT:PSS?MoO₃?/Bphen:Cs₂CO₃ is introduced as electron injection layer?EIL?in the bottom-emission inverted organic light-emitting diodes?BIOLEDs?.The devices with PEDOT:PSS/Bphen:Cs₂CO₃ or MoO₃/Bphen:Cs₂CO₃ as EIL achieve maximum current efficiency of 87.3 cd/A and 86.6 cd/A,respectively,which are higher than that79.8 cd/A of the device with the n-doping Bphen:Cs₂CO₃ as EIL,and 51%and 55%improvement in the half operational lifetime.The results show that the organic p-n junctions as EIL can effectively improve the efficiency and lifetime of the devices.2.The effect of the thin layer metals Au,Ag,Al as electron injection layers,or inserted them in the organic p-n junctions of HAT-CN/Bphen:Cs₂CO₃,MoO₃/Bphen:Cs₂CO₃,MoO₃:NPB/Bphen:Cs₂CO₃ on the performance of the devices were studied.The organic p-n junctions inserted with thin-layer metal used as an electron injection layer can enhance the ability of the electron injection effectively.The maximum current efficiency of the decives were 86.00 cd/A and 83.51 cd/A when thin metal Ag was inserted in organic p-n junction HAT-CN/Bphen:Cs₂CO₃,MoO₃:NPB/Bphen:Cs₂CO₃,respectively.The operation voltage was also reduced by 0.1 V.The result shows that the thin metal Ag can impede the mutual diffusion of the p-type material and the n-type material in the p-n junction and improve the charge generation capability of the p-n junction.Therefore,the electron injection capability,the efficiency and lifetime of the device have been improved effectively3.The hole injection ability of the devices based on Au,Ag and Al was studied.The efficiency of device based on Au reaches 83.92 cd/A because of that Au can increase the hole injection ability of the device effectively.The effect of the n-p junction LiF/metal/MoO₃ and Bphen:Cs₂CO₃/metal/MoO₃ as hole injection layers on device performance was also investigated.The maximum current efficiency of the devices used n-p junction LiF/metal/MoO₃ and Bphen:Cs₂CO₃/metal/MoO₃ are 85.70 cd/A and 84.58cd/A,respectively,which is better than that of device using MoO₃ as the hole injection layer.