Edge functionalized graphene nanoribbons with tunable band edges for carrier transport interlayers in organic–inorganic perovskite solar cells

Abstract

Organic based graphene nanoribbons (GNRs) can be good candidates as carrier extraction interlayers for organic/inorganic hybrid perovskite solar cells, owing to the possibility of tuning the band edge energy levels through varying the width and the type of edge functionalization. By using the density functional theory (DFT) method, the electronic structures of H or F edge functionalized armchair type GNRs on MAPbI₃(001) are calculated. It is shown that the electronic structure of H- or F-passivated GNRs is almost undisrupted by the non-covalent interaction with the PbI₂ surface layer of MAPbI₃(001), thereby one can tune the width and edge chemistry of GNRs to enhance the carrier extraction or blocking. Especially all H-GNRs five to ten carbon atoms wide exhibit good matching for hole extraction, while F-GNRs require a specific width for electron extraction. Exploiting the unzipping synthesis of carbon nanotubes in the solution phase, our result provides a facile strategy for efficient carrier extraction.