Interface-Enhanced PbS Quantum Dot Short-Wave Infrared Photodetector toward Instant Smoke Detection Applications

Colloidal lead sulfide (PbS) quantum dots (QDs) have emerged as promising materials for short-wave infrared (SWIR) photodetectors (PDs) due to their size-tunable absorption, low-temperature processability, and compatibility with large-area fabrication. However, surface trap states in the electron transport layer (ETL), commonly zinc oxide (ZnO), often lead to increased charge recombination and dark current, limiting device performance. Here, we report a surface modification strategy using (3-aminopropyl)triethoxysilane (APTES) to functionalize ZnO ETLs in PbS QD PDs. This treatment reduces the surface roughness from 8.90 to 6.69 nm and passivates interfacial defects via silane bonding. As a result, the devices exhibit suppressed dark current (from 2155 to 855 nA/cm 2 ), enhanced specific detectivity (from 1.39 × 10 10 to 8.08 × 10 10 Jones), and improved response speed and optimized signal stability. Furthermore, the PD retains over 85% of its photocurrent under SWIR illumination in simulated smoke conditions, whereas the visible light response drops by more than 50%, demonstrating excellent potential for real-time smoke detection. These findings underscore the effectiveness of ETL interface engineering in advancing high-performance, low-cost SWIR PDs for imaging and environmental sensing applications.