We report a facile, solution based, post synthetic colloidal atomic layer deposition (PS-cALD) process to engineer the surface stoichiometry and therefore electronic properties of lead chalcogenide nanocrystal (NC) thin films. Using the stepwise and systematic PS-cALD technique, we introduce a self-limited monolayer shell on lead chalcogenide NCs after their integration as thin films in devices, thereby requiring no further treatment or ligand exchange that unavoidably generates some surface defects. We found that chalcogen enriched NC surfaces are structurally, optically and electronically unstable due to their high surface energy, oxygen sensitivity, and introduction of many midgap and trap states. Lead chloride treatment creates a well-passivated, trap-free shell that stabilizes NCs structurally, optically and electronically, greatly enhancing charge transport. Using PS-cALD of lead chalcogenide NC thin films we demonstrate high electron field effect mobilities of approximately 4.5 cm2/Vs, comparable to record performing devices, without using expensive vacuum-based techniques.
Citation: Nano Letters
Pub Type: Journals
nanocrystals, field-effect transistor, atomic layer deposition