Highly Responsive, Solution-Based Al/PbS and Au-Ti/PbS Schottky Photodiodes for SWIR Detection

We realized two PbS colloidal quantum dot (CQD) based Schottky photodetectors, formed of indium tin oxide anode, the photosensitive PbS layer, and a Schottky contacts of titanium-gold (Ti-Au) stack for higher longer lifetime and aluminum (Al) for higher responsivity. Long capping ligands of PbS QDs were replaced with shorter ones and layer-by-layer deposition method was applied to form pinhole-free and uniform PbS CQD films, enabling better responsivity and longer lifetime. In Al/PbS, under 2 V reverse bias and 5 mW/cm² illumination at 1550 nm, 0.195 A/W responsivity, 15.6% quantum efficiency, and 8.19 ×10¹⁰ Jones normalized detectivity is achieved. In Au-Ti/PbS, under 3 V reverse bias and 5 mW/cm² illumination, 0.667 A/W responsivity, 53.3% quantum efficiency, and 2.12 ×10¹⁰ Jones normalized detectivity is achieved.