One of the major challenges confronting organic electronics is the development of high-mobility semiconducting materials, especially n-channel and ambipolar semiconductors. Solution-processable semiconducting polymers have attracted much attention because of their tunable properties and their suitability for the fabrication of large-scale devices. Aza substitution has proven effective in electron-transport small-molecule semiconductors; however, high-performance polymeric semiconductors prepared by aza substitution are still lacking. We started with a computational screening procedure to introduce nitrogen atoms into isoindigo-based polymers and then proceeded with the synthesis and fabrication of field-effect transistors. The resulting 7,7′-diazaisoindigo-based polymers exhibit extensive π conjugation and high crystallinity with hole mobilities exceeding 7 cm 2 V −1 s −1 with bottom-gate/bottom-contact configuration and ambipolar transport properties with top-gate/bottom-contact configuration in air. These properties make diazaisoindigo a promising building block for polymeric semiconductors.

Organic/polymeric semiconductors are mainly composed of aromatic systems including phenyl, vinyl, alkynyl, thienyl, and other isoelectric groups, which are constructed of carbon, hydrogen, and so-called 'hereroatoms' including chalcogen, nitrogen, and halogen atoms etc. The introduction of heteroatoms could yield different electronic properties by influencing the molecular geometry, the HOMO and LUMO energy levels, intermolecular interactions and so on. In this Research News article, we provide a brief review of the effect of heteroatoms and recent developments in heteroatom substituted organic/polymeric semiconductors, focusing especially on their application in field-effect transistors.