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.