Photocrosslinked Organic–Inorganic Hybrid PbS Quantum Dot Avalanche Photodiodes for CMOS-Compatible SWIR LiDAR Sensors

SWIR (1550 nm) LiDAR is attracting increasing interest owing to its superior eye safety and long-range detection capability compared with conventional 905 nm systems. However, the widespread adoption of SWIR sensors is still limited by the high cost and complex fabrication of InGaAs photodetectors. Although PbS quantum dot (QD)-based avalanche photodiodes (APDs) have emerged as promising low-cost alternatives, their performance is often restricted by the instability of exposed {100} facets in large-sized PbS QDs and inefficient charge transport through insulating ligand networks.

Here, we report an organic–inorganic hybrid avalanche platform utilizing an azide-functionalized dithiolane ligand (FPA-S) as a multifunctional interfacial material. The FPA-S ligand selectively passivates the reactive {100} facets of large-diameter PbS QDs while simultaneously forming covalent photocrosslinks with surrounding organic semiconductors. This dual functionality suppresses organic–inorganic phase separation and creates a robust conductive encapsulation network, resulting in enhanced film stability and efficient carrier transport. Consequently, stable avalanche multiplication can be achieved under strong reverse-bias conditions.

The fabricated devices exhibit stable operation beyond −30 V and efficient impact-ionization-driven carrier multiplication. An avalanche gain of ~90 was obtained, while activation energy sign reversal with increasing reverse bias confirmed that the gain originated from impact ionization rather than trap-assisted amplification. These findings demonstrate a viable strategy for realizing low-cost, CMOS-compatible SWIR avalanche photodetectors with high gain and improved operational stability, offering a promising platform for next-generation LiDAR and infrared imaging technologies.