Colloidal Quantum Dot Solid-Based Infrared Optoelectronics Enabled by Solution-Phase Ligand Exchange

This study explores the rational strategy to build lead sulfide (PbS)-based colloidal quantum dots (CQDs) solid for high performance photodetection and solar energy conversion in the near- and short-wave infrared spectra. We demonstrated a facile engineering process from CQD synthesis to infrared CQD devices fabrication. By controlling the monomer concentration, we effectively tuned the infrared absorption characteristics and the solution-phase surface ligand exchange resulted in highly concentrated CQD ink, facilitating the formation of uniform, and thick CQD solids, which is crucial for high absorption efficiency. The CQD-based infrared photodetector achieved a specific detectivity of approximately 10¹¹ Jones and fast response times under 100 ns. Furthermore, optimized PbS CQDs were utilized in solar cells and achieved high quantum efficiency across visible to infrared spectrum, indicating a significant potential for 2-terminal tandem structures with perovskite front cells.