Synergistic Two-Step Passivation Enables Defect-Suppressed Inverted PbS Photodetectors for High-Detectivity Shortwave Infrared Sensing

Shortwave infrared (SWIR) detection is pivotal for diverse applications, ranging from depth imaging and autonomous driving to biological sensing. Among various semiconductor candidates, PbS colloidal quantum dots (CQDs) stand out due to their tunable bandgap and solution processability, offering immense potential for integration into next-generation optoelectronic circuits. However, PbS CQD photodetectors with an inverted structure, which is crucial for integration with silicon or organic electronics, still remain underexplored, largely restricted by their poor quantum efficiency, particularly at around 1350 nm. Herein, we demonstrate a high-performance inverted SWIR photodetector with a device configuration of ITO/NiOx/PbS-EDT/PbS-I⁻/ZnO/Al, achieving smooth band alignment and efficient carrier transport. Furthermore, via a two-step passivation process, large-scale and low-defect PbS CQDs were obtained. Consequently, in devices, a high quantum efficiency exceeding 40% at 1350 nm was successfully achieved, accompanied by a high specific detectivity of 1.05 × 10¹³ Jones and a fast response of 470 μs, which demonstrates potential for high-resolution and high-speed SWIR sensing. As a result, the proof of concept in SWIR imaging and fire detection confirms that the constructed PbS CQD detector meets the requirements for practical sensing application.