Injection and charge transport processes of polymer light emitting diodes

We investigated thianthrene (TH) and 2-(4-biphenyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD), which is known to be a good scintillator dye and have good electron transport properties, separately by cyclic voltammetry in solution. All electrochemical measurements were performed in solutions of N-methylporrolidone in the reduction region and in acetonitrile (for PBD) and dichloromethane (for TH) in the oxidation direction. We also investigated the current-voltage (I-U) characteristics for testing the diode character and capacitance-voltage (C-V) behaviour of different single and double layer structures to describe the function of such devices. For LED fabrication, TH and PBD were mixed with 20% polycarbonate (PC) dissolved in chloroform, so that a mixed single layer with a thickness of 150 nm as an LED blend structure was built up.