Field and temperature dependent transport properties of undoped and doped polyaniline films

The low and high electric field conductivity measurements were carried out in undoped and (+/-)-10-camphorsulfonic acid (CSA) doped polyaniline (PANI) film samples in the temperature range 173 T <= 303 K and 303 <= T <= 383 K, respectively. In the undoped and doped polyaniline films one and three dimension variable range hopping (VRH) type is identified, respectively, at low electric field (1 x 10(3) V/cm) in the temperature range 173 <= T <= 303 K. The VRH parameters such as localization length (alpha(-1)), hopping range (R-hop) and hopping energy (R-hop) are calculated and the influence of doping on these parameters is discussed. The current-voltage (I-V) characteristics studied at high field (< 10(4) V/cm) for the undoped and doped polyaniline films in the temperature range 303 <= T 383 K exhibit the space charge limited current (SCLC) conduction mechanism. The activation energy (E-alpha) calculated from the plot in theta versus T-1 of the doped sample is reduced to nearly half of the undoped. The hole mobility (mu) value 7.06 x 10(-8) m(2)V(-1) s(-1) for UP and 2.37 x 10(-9) m(2)V(-1) s(-1) for DP calculated at 303 K are well within the limits of reported conjugated polymers. A high value of trap density (N-t = 1.28 x 10(21) m(-3)) is found for doped polyanifine film supports the 1D variable hopping in DP film. The trap parameters such as the trap filled limit voltage (V-TFL), the depth of the dominant trap level (E-t-E-v), the density of states within the hole mobility edge (N-v) are also calculated and their dependence on doping is discussed. The traps exponentially distributed in energy and a single discrete trapping level is found for undoped and doped polyanifine films respectively.