Low‐Dimensional Organic Semiconductor Single‐Crystal Heterojunctions for Next‐Generation Optoelectronic Devices

Abstract Organic semiconductor single‐crystal heterojunctions (OSSCHs) are engineered by integrating complementary organic semiconductor crystals to enable ambipolar transport and multifunctional device performance. This review outlines recent progress in the crystal growth, interface physics, and device applications of OSSCHs, with an emphasis on low‐dimensional structures achieved through controlled crystallization and advanced interface engineering. Innovations in crystallization control, such as integrated self‐assembly and van der Waals epitaxy, have enabled the construction of defect‐minimized heterointerfaces with molecular‐level precision. Emerging strategies in low‐dimensional engineering, including vertically stacked heterostructures and ultrathin 2D molecular crystals, have optimized carrier dynamics while introducing unique optoelectronic properties. The engineered band alignment at heterointerfaces critically governs exciton dissociation efficiency and charge transport pathways, directly enhancing device performance in photovoltaics and light‐emitting systems. These heterojunctions demonstrate promising applications across ambipolar transistors, light‐emitting devices, and neuromorphic electronics by overcoming the inherent limitations of unipolar active layers. The review also highlights current challenges and future research directions, emphasizing the role of OSSCHs in advancing the fields of materials science and optoelectronic device engineering.