LAUSR

A highly stable p-type PbS-QDs ink is prepared using a single-step biphasic ligand exchange route, overcoming instability encountered in previous reports. Chemical characterization of the ink reveals 3-mercaptopriopionic acid (MPA) capped QDs stable in benzylamine solvent over a period of weeks or longer. The film resistivity, 1.45 kΩ cm, is an order magnitude lower and surface roughness, ∼ 0.5 nm, is superior vs. PbS films reported so far, and proof of concept photovoltaic devices showed efficiency > 5.5%.