Application Of Poly(3,4-ethylenedioxythiophene) In Organic Light-emitting Diode

Poly(3,4-ethylenedioxyth) is one of the most promising conductive polymer in organic optoelectronical devices. The mixture of Poly(3,4-ethylenedioxyth) and poly (styrenesulfonate) is soluble in water. With simple processing methode, such as dip coating, spin coating, ink-jet printing etc, it can form conductive film with good transparency. In order to further improve the conductivity of PEDOT:PSS film and to further apply to PLED devices, I carried out the following research work:1 Improving conductivity of PEDOT:PSS by doping.By doping ethylene glycol, isopropanol or DMSO,the conductivity of PEDOT:PSS(doping) is dramatically enhanced, from 1 to 1500 s/cm. Using Four Point Probe, the conductivity film of PEDOT:PSS(doping) is respectively measured under different ratio of PEDOT:PSS and isopropanol, PEDOT:PSS and DMSO, and PEDOT:PSS and ethylene glycol,. The best ratio is (PEDOT:PSS):IS:DMSO=16:5:0.8. The conductivity of the film of PEDOT:PSS(doping) is influenced by different temperatures and different treatment time for films.The optimum condition is 150℃for 55 minutes, while the conductivty of the film treated 200℃for 55 minutes is reduced.In a word,a bit of doping remained of the film is in favor of conductivty.2...Polymer light-emitting diode with highly conductive polymer as anode layerPolymer light emitting diodes are fabricated by using PEDOT:PSS(doping) film as anode. When the thickness of high conductivity PEDOT:PSS(doping) film is 240nm, its performance as anode is as good as ITO.The efficiency of 240nm device is 1.7cd/A.and The efficiency of ITO device is 1.9 cd/A.3 MEH-PPV:PEO as active layer in PLED.The emission peak of MEH-PPV shows red shift from 580nm to 625nm when adding with PEO,which may be because of producing a exciplex. Adding a little PEO to MEH-PPV, the performance of the PLED is improved.When the The ratio of MEH-PPV:PEO is 12:1.the efficiency of PLEDis 2cd/A; But the efficiency of PLED without PEO is 0.044cd/A.So adding a small amount of PEO to MEH-PPV can improve electron injection to furtherly balance electron and hole injection, and to improve film and to reduce interface effect between films and to reduces deficiency of the MEH-PPV film possibly.