Electrical transport crossovers and thermopower in doped polyaniline conducting polymer

Abstract

We report on both the electrical and thermoelectric transport properties as a function of temperature in polyaniline doped with camphor sulfonic acid (CSA) for a wide range of CSA doping. A transport crossovers diagram illustrating metallic and insulating like behaviors is proposed and seems to result from the interplay between charge doping and disorder. In particular, the one half doping not only leads to an optimal electrical conductivity reaching 120 S/cm at 300 K but also the lowest thermopower slope. The measured thermopower appears closely related to the metallic onset in agreement with a metallic origin of its linear temperature dependence.

Manipulating Carrier Concentration by Self-Assembled Monolayers in Thermoelectric Polymer Thin Films

“…Highly doped conducting polymers (e.g., polyacetylene, polyaniline) are found to show a change from nonmetallic sign (dσ/d T > 0) at low temperatures to metallic sign (dσ/d T < 0) at higher temperatures as the carrier density increases. , The Fermi energy increases with the increase of the charge concentration. Temperature promotes the quantum phase transition of the charge carriers from localization to diffusion, leading to itinerant electronic states at higher temperatures . Therefore, the lower crossover temperatures of the doped films on pristine and CF 3 –SAM-modified substrates could be attributed to their higher charge carrier concentrations.…”

“…Temperature promotes the quantum phase transition of the charge carriers from localization to diffusion, leading to itinerant electronic states at higher temperatures. 44 Therefore, the lower crossover temperatures of the doped films on pristine and CF 3 −SAM-modified substrates could be attributed to their higher charge carrier concentrations. The S values of all the doped films exhibit similar upward trends as the temperature increased, which is widely observed in most highly doped polymeric TE materials.…”

The cross-interface energy-filtering effect at organic/inorganic interfaces balances the trade-off between thermopower and conductivity

“…When the PANI content reaches 30%, a percolation network for carrier transport is established in the PANI coating and results in the highest σ observed in 15% PANI/85% MWCNT, which is 5.56-fold higher than that of the MWCNT network at 100 K. The σ of the MWCNT network shows a “peak” shape dependent on T , corresponding to a transition of the carrier transport from semiconductor-like to metal-like. A similar transition of the carrier transport also occurs in the emeraldine-based PANI with a critical T of 200 K. 39 On the contrary, the σ of PANI/MWCNT is negatively dependent on T , suggesting metal-like carrier behavior. Therefore, the interfacial effect of the PANI/MWCNT interfaces may be the exclusive factor determining the metal-like conductivity of PANI/MWCNT.…”

“…The S of the MWCNT networks increases at first and then decreases with increasing T , while a monotonous increase in S of PANI/MWCNT is obtained with increasing T . Moreover, PANI/MWCNT shows a higher S than the MWCNT network 39 above room temperature; however, an opposite tendency is observed at low T . By speculatively illustrating the decrease in the S of the MWCNT networks after introducing the PANI coating due to the low S of PANI, it is hard to explain the higher S of PANI/MWCNT than that of each constituent above room temperature.…”

“…Both the MWCNT network and PANI/MWCNT possess a positive S value, denoting the dominant contribution of hole carriers. The S of the MWCNT networks increases at first and then decreases with increasing T, while a monotonous increase in S of PANI/MWCNT is obtained with increasing T. Moreover, PANI/MWCNT shows a higher S than the MWCNT network 39 above room temperature; however, an opposite tendency is observed at low T. By speculatively illustrating the decrease in the S of the MWCNT networks after introducing the PANI coating due to the low S of PANI, it is hard to explain the higher S of PANI/MWCNT than that of each constituent above room temperature. As an alternative, the interfacial effect at the PANI/MWCNT interfaces is the key to determining the unusual increase in the S of PANI/MWCNT.…”