Selenol-capped PbS CQDs via Thermal Cleavage for High Performance Short-wavelength Infrared Photodetectors

However, in state-of-the-art devices, performance remains limited by an ineffective hole-transport layer, stemming from the difficulty of controllably and substantially inducing p-type doping in PbS quantum dots. Here, we report a method to obtain PbS CQDs with a chalcogenide-rich stoichiometry using organoselenide ligands such as potassium selenocyanate, benzeneselenol, and 1-hydroselenopropan-2-ol, where the weak Se–C bonds of the ligands dissociate under mild annealing, leaving a Se-passivated CQD surface.

All resulting CQD thin films exhibit significantly enhanced hole mobilities, when compared to state-of-the-art p-type PbS films, reaching a record of 0.15 cm2 V-1 s-1 using the benzeneselenol ligand. Spectroscopic and computational investigations of 1-seleno-2-propanol-capped CQDs provide strong evidence that the controlled Se–C cleavage enables the chalcogen-rich surface stoichiometry, thereby shifting the Fermi level towards the HOMO level, determining an enhanced p-type behavior.