Space-charge limited conduction in polyaniline films

Polyaniline emeraldine base (PANI-EB) powder was synthesized by oxidative polymerization of aniline. The PANI-EB films were prepared by the solution-casting technique. The temperature-dependent dc conductivity measured in the range 173-303 K suggests that the PANI-EB is a quasi-one-dimensional disordered conductor. The current-voltage characteristics of the PANI-EB films measured in the range 333-383 K showed the SCLC mechanism. The SCLC parameters such as free carrier density (p(0)), trap density (p(t)), the ratio between free carrier density to the total carrier density (theta), mobility (mu) and the effective hole mobility (mu(eff)) were calculated. The activation energy (E-a = 0.32 eV) and the Fermi level (E-F = 0.42 eV) were estimated. As well as these, the trap parameters such as the trap filled limit voltage (V-TFL), the shallow trap density (N-t), the depth of the dominant trap level (E-t - E-v), the density of states within the hole mobility edge (N-v) and the characteristic energy (E-c) were also calculated and presented. The exponential type of traps distribution with large number of traps was found to be due to the disorder and moisture in the polymer films. (C) 2004 Society of Chemical Industry.