The effect of shell modification in iron oxide nanoparticles on electrical conductivity in polythiophene-based nanocomposites

Abstract

In the field of organic electronics, the energy level alignment between the components of a device is crucial for its final performance. Improvement in the final properties can be achieved using hybrids made of organic and inorganic materials. In highly defected systems, like polymers or nanoparticles, every charge carrier matters, and the potential barriers or possible defects must be considered when designing a hybrid consisting of such components. However, the difference in the interface modification in such materials and its influence on final conductivity were never studied before. This paper shows how modification of the medium in iron oxide nanoparticle synthesis can increase the hole transportation efficiency without altering the morphology, magnetic properties, and chemical composition of the obtained nanoparticles. We found that a six-time increase of conductivity can be achieved, mainly due to the shift in the hole injection barrier which was reduced from 1.7 eV for pristine P3HT to 1 eV for materials made of nanoparticles and P3HT, and also by lack of the diffusion barrier between the nanoparticles and conducting polymer. Until now, research on such systems has mainly focused on the dispersity and stability of nanoparticles, which led to the isolation of components in the final product caused by capping agents at the surface of the additive. Our results demonstrate how surface functionalization of iron oxide nanoparticles can reduce the barrier at the nanoparticle/polythiophene interface and influence the energy level alignment, hence improving the electrical conductivity of the final material.