Incorporation of benzothiadiazole into the backbone of 1,2,5,6-naphthalenediimide based copolymers, enabling much improved film crystallinity and charge carrier mobility

Abstract

By incorporating benzothiadiazole units into the main chain of 1,2,5,6-naphthalenediimide (iso-NDI) and thiophene based copolymers, we report herein a new high performance donor–acceptor (D–A) polymer, P(iso-NDI-TBT), with much improved film crystallinity and charge carrier mobility. The optical, electrochemical, and charge transport properties as well as the photovoltaic performance were investigated. Bottom-gate bottom-contact organic field-effect transistors (OFETs) based on the thin films of P(iso-NDI-TBT) show a high hole mobility of up to 0.82 cm² V⁻¹ s⁻¹, which is a record value for the 1,2,5,6-NDI based polymers. In addition, the photovoltaic performance of P(iso-NDI-TBT) was also studied, affording a power conversion efficiency (PCE) of 1.5% with a high open-circuit voltage (V_oc) of 0.9 V. Our work provides important clues for designing high performance D–A polymeric semiconductors and also demonstrates that 1,2,5,6-NDIs are promising building blocks for constructing new polymer semiconductors.