A Conjugated Polymer Containing a B ← N Unit for Unipolar n‑Type Organic Field-Effect Transistors

Solution-processed organic field-effect transistors (OFETs) have great potential for next-generation “plastic electronics”. The development of n-type polymer semiconductors still lags far behind that of p-type polymer semiconductors, including material number and device performance. Moreover, the reported high-performance n-type polymer semiconductors are mostly based on amide and imide units. To enrich the family of n-type polymers and promote the development of OFETs, we have proposed using a boron–nitrogen coordination bond (B←N) to develop n-type polymer semiconductors. In this work, we report a B←N-containing conjugated polymer, PBN-13, which is an alternating polymer of a double B←N-bridged bipyridine unit and a 5,6-difluoro-4,7-di­(thiophen-2-yl)­benzo­[c]­[1,2,5]­thiadiazole unit. This polymer exhibits strong aggregation ability in solution and good crystallinity in a thin film, which are very desirable for achieving good electron-transporting properties. The OFET device based on PBN-13 shows unipolar n-type behavior with an electron mobility of 0.19 cm² V^–1 s^–1. The electron mobility is enhanced ∼10-fold compared to those of other n-type polymer semiconductors containing a B←N unit. This study thus not only provides an efficient n-type polymer semiconductor but also proves that the B←N unit is a promising candidate for the development of n-type polymer materials for OFETs.