Interfacial Tunneling Enables High-Gain SWIR Photodetection in Asymmetric n-i-n PbS Quantum Dot Devices

Short-wave infrared (SWIR) sensing at 1500 nm is essential for eye-safe LiDAR and night vision. Conventional detectors fail in photon-starved environments due to systemic readout noise. Realizing photomultiplicative gain without amplifying noise or sacrificing response speed remains a bottleneck for colloidal quantum dot (CQD) detectors. Here, we report an asymmetric n-i-n CQD architecture that breaks this trade-off via interfacial band engineering. Integrating a C60 molecular interlayer establishes an energetically asymmetric junction that suppresses dark leakage while localizing accumulation of photogenerated holes. This accumulation acts as a dynamic gate, enhancing the local electric field and narrowing the electron-injection barrier to enable tunneling-mediated photomultiplication. The devices achieved a maximum external quantum efficiency (EQE) of over 1400% under -3.2 V and 300% at 1520 nm under -1.6 V, with a response time of 33 µs, and a dark-current density of 8×10-4 mA cm–2 at -0.5 V. Crucially, we monolithically integrated this architecture with a CMOS readout integrated circuit to demonstrate a 640×512-pixel focal-plane imaging under low-light conditions. These findings establish interfacial tunneling engineering as a promising strategy for combining high photomultiplicative gain, fast response, and CMOS-compatible integration in next-generation SWIR imaging systems.