# Temperature dependent charge transport mechanisms in carbon sphere/polymer composites

## TL;DR

This study compares charge transport mechanisms in carbon sphere/polymer composites, revealing that electron hopping dominates in CS/PANi while tunneling is prevalent in CS/PEO, with temperature-dependent conductivity behaviors.

## Contribution

It provides a comparative analysis of charge transport in CS/polymer composites using PANi and PEO, highlighting different conduction mechanisms and their temperature dependencies.

## Key findings

- Variable range hopping dominates in CS/PANi.
- Direct tunneling is observed in CS/PEO.
- Different temperature dependence of conductivity in the two composites.

## Abstract

Carbon spheres (CS) with diameters in the range $2 - 10 \mu m$ were prepared via hydrolysis of a sucrose solution at $200^o C,$ and later annealed in $N_2$ at $800^o C.$ The spheres were highly conducting but difficult to process into thin films or pressed pellets. In our previous work, composite samples of CS and the insulating polymer polyethylene oxide (PEO) were prepared and their charge transport was analyzed in the temperature range $ 80 K < T < 300 K. $ Here, we analyze charge transport in CS coated with a thin polyaniline (PANi) film doped with hydrochloric acid (HCl), in the same temperature range. The goal is to study charge transport in the CS using a conducting polymer (PANi) as a binder and compare with that occurring at CS/PEO. A conductivity maxima was observed in the CS/PEO composite but was absent in CS/PANi. Our data analysis shows that variable range hopping of electrons between polymeric chains in PANi-filled gaps between CS takes on a predominant part in transport through CS/PANi composites, whereas in CS/PEO composites, electrons travel through gaps between CS solely by means of direct tunneling. This difference in transport mechanisms results in different temperature dependences of the conductivity.