High-Sensitivity SWIR Photodetector Based on PbS Quantum Dots via Solution-Phase MAPI Ligand Exchange

Area of Science:

• Optoelectronics
• Materials Science
• Nanotechnology

Background:

• Short-wave infrared (SWIR) sensors are vital for LIDAR systems in autonomous transportation, robotics, and security.
• Demand is increasing for eye-safe SWIR sensors operating above 1400 nm.
• Quantum dot (QD)-based SWIR sensors offer tunable wavelengths and selective detection but suffer from low sensitivity due to long organic ligands.

Purpose of the Study:

• To improve the sensitivity and stability of QD-based SWIR photodetectors.
• To replace insulating organic ligands on PbS QDs with conductive inorganic ligands.
• To fabricate and characterize a SWIR photodetector using MAPI-capped PbS QDs.

Main Methods:

• Synthesized lead sulfide quantum dots (PbS QDs).
• Replaced long organic ligands with short inorganic methylammonium lead iodide (MAPI) ligands in solution.
• Fabricated a SWIR photodetector device using the MAPI-capped PbS QDs.

Main Results:

• The MAPI-capped PbS QD photodetector demonstrated high performance in the 1400-1500 nm range.
• Achieved an external quantum efficiency (EQE) of 62%.
• Obtained a responsivity of 0.73 A/W and a detectivity of 2.26 × 10¹¹ Jones.

Conclusions:

• Replacing organic ligands with inorganic MAPI ligands significantly enhances PbS QD photodetector performance.
• The developed SWIR photodetector is suitable for eye-safe LIDAR applications.
• Solution-based fabrication offers a cost-effective and scalable approach for advanced SWIR sensors.