Abstract
Frequency dependent (ac) and independent (dc) conductivity measurements have been carried out on polyaniline (PANI) films deposited by solution casting technique. Under low electric field (1 × 103 V/cm) condition, the dc conductivity measured in the temperature range of 173–303 K obeys the three-dimensional variable range hopping (3D VRH) formalism. The Mott parameters such as localization length (α−1 ≈ 7 Å), density of states [N(E F ) = 1.04 × 1019 states/eV cm3], hopping range (R hop = 60 Å) and hopping energy (W hop = 0.38 eV) are computed. The ac conductivity measured in the frequency range 10 kHz–5 MHz and in the temperature range 150–380 K follow a power-law dependence σ ac ∼ ω s, typical for charge transport by hopping or tunnelling processes. Therefore, the experimental results are analyzed with reference to various theoretical models based on quantum-mechanical tunnelling and classical hopping over barriers. The observed minimum in the temperature dependence of the frequency exponent s strongly suggests that tunnelling of large polarons is the dominant transport process. The polaron radius (r p ≈ 25 Å) and barrier height for infinite site separation (W HO ≈ 0.22 eV) are evaluated. The density of states [N(E F)] and tunnelling distances (R ω ) are estimated and discussed in terms of frequency and temperature.
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Abbreviations
- PANI:
-
polyaniline
- VRH:
-
variable range hopping
- EB:
-
emeraldine base
- XPS:
-
X-ray photoelectron spectroscopy
- QMT:
-
quantum mechanical tunnelling
- CBH:
-
correlated hopping over a barrier
- OLPT:
-
overlapping large polaron tunnelling.
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Prem Nazeer, K., Thamilselvan, M., Mangalaraj, D. et al. Direct and High Frequency Alternating Current Conduction Mechanisms in Solution Cast Polyaniline Films. J Polym Res 13, 17–23 (2006). https://doi.org/10.1007/s10965-005-9007-9
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DOI: https://doi.org/10.1007/s10965-005-9007-9