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

ABSTRACT:Poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most important conducting polymer. The solution of PEDOT doped by PSS has notable properties in electrical conductivity and optics, which is always used to make as the electrode of the devices. It can realize the light of the devices through from the both side. This paper mainly studies the application of the conductive polymer PEDOT:PSS in optical-electrical device. Including:1:First of all, we studied the conductivity of PEDOT:PSS, which can be highly improved by doping organic alcohols. In the experiment we find that the conductivity of the film made by PEDOT:PSS solution which is doped by DMSO is the highest. The conductivity of film is improved from 0.33s/cm to 60.6s/cm. Finally we chose the dimethyl sulfoxide (DMSO) for the electrode of the devices.2:Organic light-emitting diode are fabricated by using PEDOT:PSS film as anode and ITO as the cathode. The structure of the device is D-PEDOT/TiO2/MEH-PPV/ITO. We use MEH-PPV as light emitting layer and fabricate the organic light-emitting diodes with the Al electrode. Compared with the devices of Al electrode, the luminance of the devices with PEDOT electrode is 30cd/m2 and the efficiency is 0.015cd/A. The luminance of the devices with Al electrode is 220cd/m2 and the efficiency is 0.021cd/A. We can find that the property of the devices with PEDOT electrode is too worse than the devices with Al electrode. We analysis the probable reason of the difference. One is the conductivity of the D-PEDOT is worse than that of ITO. The other is that the work function of ITO is too high to inject electron from the cathode. So we fabricate the LEC of which the work function is not important.3:We fabricate organic light emitting electrochemical cell (LEC) using the PEDOT:PSS electrode. Because of the difference of OLEC and OLED in light emitting mechanism, the work function of the electrode is not very important to devices. We fabricate the LEC devices with the structure of ITO/MEHPPV+PEO+LiCF3SO3/TiO2/D-PEDOT. The luminance is 450cd/m2,and the efficiency is 0.43cd/A.Compared with the OLED devices of same structure,the property of the devices apparently improved.