Influence of the nature of polyaniline-based hole-injecting layer on polymer light emitting diode performances

We have studied the use of water and solvent-based polyaniline (PANI) dispersions as a transparent hole-injecting layer in polymer light emitting diodes (PLEDs). We have investigated the effects of the pH, the conductivity, the work function and the nature of the solvent and the dopant on the hole-injection properties. The water-dispersed PANI at a low pH (pH 1.8) showed an efficiency similar to that of PEDOT-based devices due to its high HOMO level and high conductivity. For the solvent-based PANI dispersions, the influence of the nature of the solvent and the dopant on the crystallinity, the conductivity of the PANIs and on the performances of the light emitting devices is discussed.