Materials Interface Engineering: Impact of Interfacial Molecular Orientation on Organic Electronic Devices

Abstract Molecular‐based electronic devices exploit the unique properties of single molecules or assemblies to surpass conventional solid‐state systems in miniaturization, efficiency, and functional diversity. Their performance hinges on controlling molecular orientation and packing at interfaces, which dictate charge transport and energy‐level alignment. Molecular orientation describes the directional alignment (e.g., face‐on, edge‐on) of organic semiconductors relative to substrates, while packing involves spatial arrangement, crystallinity, and interactions (π–π stacking, hydrogen bonding). Advanced techniques such as scanning probe microscopy (SPM), grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), and Kelvin probe force microscopy (KPFM) elucidate these structural features, establishing correlations with optoelectronic properties like light absorption, exciton dynamics, and charge carrier mobility. The interplay between orientation and packing governs energy‐level alignment and charge transport via interfacial work function modulation. Emerging computational tools like machine learning (ML) and multiscale simulations enable predictive design of molecular configurations for targeted device functionalities. However, challenges remain in achieving uniform molecular alignment across practical device architectures and establishing robust structure‐property relationships under operational conditions. Addressing these requires integrating experimental characterization, computational modeling, and synthetic innovation. This review highlights the need for multidisciplinary approaches to advance molecular electronics toward practical, high‐performance applications, balancing fundamental insights with scalable fabrication.