Effect of alkali metal nitrate treatment on the optical properties of CsPbBr3 nanocrystal films

•CsPbBr3 nanocubes films are fabricated by layer-by-layer deposition.•The films are treated with alkali metal nitrates salts in solution.•The alkali metal ions passivate defects and improving optical properties of films.•The analysis shows potential impact for fabricating future generation devices. Colloidal cesium lead bromide (CsPbBr3) perovskite nanocrystals (NCs) are fabricated as densely packed thin films using doctor blade method through a layer-by-layer assembly approach. It is found that the optical properties of the CsPbBr3 NC films are significantly improved after a ligand exchange of oleic acid (OA) and oleylamine (OAm) by sodium and potassium nitrate in ethyl acetate. Ligand-induced surface defects are passivated by the sodium and potassium cations and nitrate, which leads to the improvement in photoluminescence (PL) and life-time properties. Compared with pristine OAm-OA capped CsPbBr3 NC film, Alkali-metal nitrate salts treated films are showing higher PL intensity and longer carrier-lifetime, evidencing their potential use to achieve defect-free inorganic perovskite NC films.