Two-Dimensional Indium Selenide for Next-Generation Photodetection: Interface Engineering, Device Architectures, and Emerging Applications

Two-dimensional (2D) indium selenide (InSe) has emerged as a compelling semiconductor platform for next-generation photodetection because of its thickness-tunable bandgap, high carrier mobility, and strong light–matter interaction. Moreover, its nonlinear, ferroelectric, piezoelectric, and polarization‑related functionalities can be modulated by phase, layer number, stacking configuration, and device architecture. This Review summarizes the recent advances in InSe-based photodetectors through a structure–property–performance framework. We first discuss the crystal structures, thickness-dependent band evolution, and preparation strategies of InSe and then compare representative device architectures including single-InSe channels, van der Waals heterostructures, ferroelectric-gated devices, asymmetric Schottky contacts, optical microcavities, and plasmonic/metasurface contact designs. Particular attention is paid to contact engineering, interface regulation, dark-current suppression, carrier-extraction acceleration, and polarization-selective detection, which have become central routes for improving sensitivity, speed, stability, and multifunctionality. Recent applications in optical sensing, broadband and polarization-resolved imaging, flexible and wearable electronics, neuromorphic vision, and secure optical communication are further reviewed. Finally, the remaining challenges associated with wafer-scale growth, defect control, environmental stability, standardized benchmarking, complementary metal–oxide–semiconductor (CMOS)-compatible integration, and system-level deployment are critically discussed. By emphasizing both recent progress and unresolved bottlenecks, this Review aims to provide a clearer roadmap for developing practical, high-performance InSe-based optoelectronic technologies.