Electrode Modification And The Research Of Luminescence Dynamics In Organic Electroluminescent Devices

For the past few years,OLED stands out in the field of flat panel display industry and lighting for many advantages,such as wide viewing angle,high brightness,high speed of response,simple preparation process,flexibility and so on.OLED is considered to be the next generation of dream display after the LCD.Relevant theories and technical problems are also break through under the efforts of researchers and significant progress has been made on the practical road.But low efficiency,short service life and difficulty of large size are still the biggest barriers which restricting the industrialization of OLED.Which the carrier injection efficiency directly affect the performance of device.Electrode modification' as one of the main research directions' is an effective way to enhance the efficiency of the carrier injection efficiency.In order to improve the efficiency of the device,the researchers have put forward many electrode modification methods,such as oxygen plasma treatment,introduction of a buffer layer and so on.Simplicity,high efficiency,energy saving,environmental protection of the electrode modification method is the target of the researchers from all over the world.This paper mainly studied the following two contents:The first part we demonstrate an environment-friendly,simple,and low energy cost approach as an alternative to conventional O2 plasma treatment to modify the surface of indium tin oxide(ITO)anodes for use in organic light-emitting diodes(OLEDs).ITO is electrochemically treated in NaCl aqueous solution.A chlorinated ITO(Cl-ITO)electrode with a work function of 5.41 eV was obtained,which is 0.66 eV higher than that of pre-cleaned ITO.The increase of work function is due to the anodic oxidation reactions occurred on the surface of ITO.The power dissipation is only ~3 mW in our approach,which is five orders of magnitude lower than that of O2 plasma treatment(~100W).We fabricated the OLEDs with the configuration of Cl-ITO/NPB(35 nm)/CBP:Ir(ppy)3(15 nm,8 wt%)/TPBi:Ir(ppy)3(10 nm,8 wt%)/TPBi(10 nm)/Bphen(50 nm)/Cs2CO3(2 nm)/Al(100 nm).A maximum power efficiency of 95.0 lm W-1 and external quantum efficiency(EQE)of 24.2 % were achieved,respectively,which was 4% and 5% higher than that of the OLED fabricated on O2-plasma-treated ITO(91.2 lm W-1,EQE=23.1%).The second part a highly efficient inverted organic light emitting diode(OLED)using 1.0 nm-thick ZnIx as a hole-blocking layer is developed.We fabricate devices with the configuration ITO/ZnIx(1.0 nm)/Alq3(50 nm)/NPB(50 nm)/MoO3(6.0 nm)/Al(100 nm).The deposition of a ZnIx layer increases the maximum luminance from 13.4 to 3566.1cd/m2.In addition,the maximum current efficiency and power efficiency are raised by three orders of magnitude,and the turn-on voltage to reach 1cd/m2 decreases from 13 V to 8 V.The results suggest that the electron injection efficiency is not improved by introducing a Zn Ix layer.Instead,the improved device performance originates from the strong hole-blocking ability of ZnIx.This work indicates that layered materials may lead to novel applications in optoelectronic devices.