BN-embedded electron-deficient aromatics: from molecular engineering to multifunctional optoelectronic devices

n-Type organic semiconductors are indispensable components of organic optoelectronic devices and are central to the advancement of flexible electronics, bioelectronics and integrated organic circuits. Despite substantial progress, the development of high-performance acceptor building blocks and their corresponding n-type polymers remains fundamentally challenged by the difficult balance among frontier molecular orbital energetics, charge-transport capability and synthetic accessibility. In this context, boron-nitrogen (BN) motifs, including three-coordinate B-N bonds and four-coordinate B ← N bonds, have emerged as versatile molecular design elements for engineering electron-deficient π-conjugated systems. Owing to their unique isoelectronic characteristics and intrinsic bond polarization, BN units can effectively lower lowest unoccupied molecular orbital energy levels, enhance electron deficiency, and modulate intermolecular interactions while preserving favourable backbone planarity. As a result, they offer broad opportunities for simultaneously tuning optical bandgaps, charge-transport properties and environmental stability. In this review, we provide a comprehensive overview of BN-embedded electron-deficient small molecules and conjugated polymers, with particular emphasis on molecular design principles, synthetic methodologies and emerging structure-property relationships. We further discuss representative applications of these materials in five major optoelectronic device platforms, highlighting how BN structural characteristics govern electronic structure, solid-state organization and device performance. Finally, we outline the key challenges that remain in this rapidly evolving field and present perspectives on the future development of BN-enabled n-type organic semiconductors. This review aims to offer a unified framework and practical guidance for the rational design of next-generation high-performance n-type organic electronic materials.