A hybrid-ligand exchange strategy for high-performance PbSe quantum dot short-wave infrared photodetectors†

Lead selenide (PbSe) colloidal quantum dots (CQDs) are promising candidates for short-wave infrared (SWIR) photodetectors due to their low-cost fabrication and solution processability. However, conventional ligand exchange strategies, such as treatment with 1,2-ethanedithiol (EDT), usually lead to incomplete defect passivation and undesirable doping characteristics. Here, we developed a hybrid-ligand strategy by combining EDT and zinc iodide (ZnI₂) to simultaneously passivate surface defects and modulate the doping type of PbSe CQD films. As a result, the photodetector responsivity improves from 0.04 A W⁻¹ to 0.40 A W⁻¹, and the specific detectivity increases from 3.4 × 10¹⁰ Jones to 2.8 × 10¹¹ Jones at 500 Hz under zero bias. The optimized device exhibits a wide linear dynamic range exceeding 114 dB and a fast response time of 7.3 μs. Finally, the infrared imaging applications of PbSe CQD photodetectors were successfully demonstrated. This work highlights the importance of synergistic surface passivation and doping modulation in enhancing the performance of CQD photodetectors.