Dual‐Surface Reaction Enabled Organic–Inorganic Hybrid Photodiodes for Faint Light Detection and Imaging

Organic–inorganic heterojunction photodetectors are garnering significant research interest. The surface‐sensitive nature of nanometer‐thin single‐crystalline semiconductors vis‐à‐vis device performance provides an ideal platform for studying organic contacts. Herein, organic‐Si nanomembrane (SiNM) hybrid photodetectors are demonstrated for probing faint light and self‐powered imaging. Universal approaches to controlling dual‐surface reactions are proposed to achieve high‐performance devices. A 1,4,5,8,9,11‐hexaazatriphenylene hexacarbonitrile (HAT‐CN) organic layer effectively blocks electron injection current by reacting to unpin the SiNM surface Fermi level. A low work‐function ytterbium oxide (YbO x ) (≈2.9 eV) buffer reduces the hole injection. A facile surface reaction process is systematically optimized for HAT‐CN and ytterbium with SiNM to selectively consolidate and deoxidize the natively grown silicon oxide (SiO x ), respectively, thereby minimizing noise. Contact interfaces between various dielectrics are investigated for maximizing device performance. The devices achieve competitive performance among state‐of‐the‐art organic–inorganic photodetectors, notably the low noise (sub‐pA/µm), ultra‐fast microsecond response speed and a high rectification of 3 × 10 7 . Further, an imaging sensor is demonstrated to operate in self‐powered mode. These results provide key insights into interfaces, devices, and system‐level applications in organic–inorganic heterogeneous optoelectronics.