Enhancement of the carrier mobility of conducting polymers by formation of their graphene composites

Conducting polymers (CP) with high charge carrier mobility are crucial for flexible organic electronic devices. However, the inherent carrier mobility of these polymers is very low. Therefore, methodologies need to be explored to improve the carrier transport in these polymers so that they can be efficiently used in organic electronic devices. Graphene, due to its exceptional electrical and mechanical properties, is a promising material to be examined for its possible incorporation in CP matrix to achieve the objective. We have prepared graphene composites of the conducting polymers following an optimized procedure and these were investigated for their charge transport properties. The mobility values were measured using electric field induced second harmonic generation (EFISHG) and field effect transistor (FET) transfer characteristics. Both the transient and average mobilities were found to increase significantly with the inclusion of graphene. This enhancement in mobility has been attributed to an ordered packing of the thinner and smaller graphene sheets with polymer chain and interfacial p-p interaction. To substantiate its usefulness in device applications, the effect of graphene inclusion was also investigated for polymer solar cells and it was observed that despite of reduction in open circuit voltage, device fabricated using graphene composites yielded about 20% higher efficiencies as compared to pristine conducting polymer devices.