Photon assisted conducting atomic force microscopy study of nanostructured additives in P3HT:PCBM

Abstract

One of the ways of improving the efficiency of polymer solar cells is to increase the conductive paths in the photoactive layer. The present work focuses on the study of the effect of additives (silver nanoparticles (Ag NPs) and graphene (Gr)) in photoactive poly-3-hexyl thiophene:phenyl-C₆₁-butyric acid methyl ester (P3HT:PCBM). The morphology and localised photocurrent obtained using Photon Assisted Conducting Atomic Force Microscopy reflect the role of these additives in the photocurrent produced by the active layer. The study depicts that the morphology of a P3HT:PCBM film changes completely with Gr additives, whereas a very small change occurs with the addition of Ag NPs. A localised photocurrent measurement exhibits that the space charge limited conduction (SCLC) phenomenon could be the dominant process of charge conduction in the P3HT:PCBM film with additives. The study also demonstrates that the carrier mobility is enhanced by more than an order of magnitude with Gr as the additive. This is a significant change for achieving efficient charge separation and transportation in polymer solar cell application.