Facet-Selective Multidentate Passivation for Suppressing Defects in PbS Colloidal Quantum Dot Photodiodes

Abstract

Lead sulfide (PbS) colloidal quantum dots (CQDs) are highly promising materials for short-wave infrared (SWIR) optoelectronics, but their performance is frequently limited by facet-dependent surface defects and energetic disorder. Specifically, the (100) facets prevalent in larger quantum dots are highly susceptible to ligand stripping and trap formation, which induce nonradiative recombination and limit device efficiency. In this work, we demonstrate a facet-selective supplementary passivation strategy, utilizing 2,6-bis(aminomethyl)pyridine (DAMP) to specifically target undercoordinated lead-rich sites on PbS (100) surfaces. Acting synergistically with conventional halide treatments, the multidentate DAMP molecules selectively anchor to the exposed (100) facets, significantly suppressing band-edge energetic disorder and defect-assisted leakage pathways. Consequently, our DAMP-passivated PbS CQD photodiodes exhibit a 2.5-fold reduction in dark current density at a reverse bias of −0.5 V and achieve an improved specific detectivity of 1.86 × 1012 Jones. Furthermore, we successfully integrate this surface engineering strategy into a 640 × 512 focal plane array (FPA). This imaging array exhibits high-resolution short-wave infrared (SWIR) capability, enabling precise material identification and subsurface defect detection, as demonstrated by distinguishing similar solvents, revealing internal defects in biological samples, and differentiating visually indistinguishable substances. Ultimately, this facet-aware passivation approach provides a highly effective and scalable pathway for realizing high-sensitivity, next-generation SWIR optoelectronic technologies.