Study On The Functional Layer Modification Of Organic Light-emitting Diodes And The Influence On The Optoelectronic Performance

The research on organic light-emitting diode (OLED) is always in progress sincethe organic electroluminescence (OEL) phenomenon was found. However, there is nosubstantial improvement until Dr. Tang used vacuum vapor deposition method tomanufacture OLED devices based on the material Alq3in1987. Then theopto-electronics performance of fluorescent OLED devices is improved remarkably.Afterward, a lot of companies and research institutes started investing to fight for aplace in this new high-tech field. As there are still some problems in this field thathave not been solved, such as short lifetime, low stability and low quality, OLED stillcannot be used in commercial applications widely. For researchers these problemspresent a direction of research to carry on. In this thesis several main purposes arepresented as follows:(1)In terms of anode modification, firstly, a P-type metal oxide MoO3is used tomodify ITO anode and manufacture devices with the structure ofITO/MoO3/NPB/Alq3/LiF/Al. The changes of feature J-V and L-V of OLED indicateoptoelectronic performance of OLED improves with increasing the thickness of MoO3.Further, the MoO3is treated by using UV-O3and air plasma, and the quantity ofMo/O in MoO3is measured by X-ray photoelectron spectroscopy (XPS). Finally adevice is manufactured to present the effect of using UV-O3and air plasma treatmentfor modifying anode.(2) In terms of cathode modification, firstly, a N-type semiconductor LiF is usedto modify cathode. The changes of feature J-V and L-V of OLED indicate the effectof using LiF to modify cathode. Further, the effect of using LiF or Cs2CO3dopedAlq3as ETL to modify cathode is presented.The study indicates that the electrons injection capability of anode is improvedby using air plasma to treat MoO3, and the electrons injection capability of cathodes isimproved by using Cs2CO3doped Alq3. Then we modify the anode and cathodeseparately and manufacture devices to prove that electrode modification can improvethe opto-electronics performance of OLED devices.