Effective surface passivation on CsPbBr3 nanocrystals via post-treatment with aromatic carboxylic acid

Surface defects on CsPbX3 nanocrystals (NCs) commonly lead to the degeneration of photoluminescence emission and stability of CsPbX3 NCs. Defect passivation by surface engineering provides an effective route to improve the optical properties and stability. In this work, a series of aromatic carboxylic acids were explored to modify the as-synthesized CsPbBr3 NCs. The surface defects of CsPbBr3 NCs are found to be effectively passivated via the binding of carboxyl group with uncoordinated Pb2+ on the surface of CsPbBr3 NCs. The coordination ability of carboxyl groups with Pb2+ can be regulated by the electron effect generated by different groups at the para-position of carboxyl groups, thereby adjusting the passivation of surface defects. Benefitting from the effective passivation of surface defects, the PL emission and stability of the CsPbBr3 NCs can be effectively enhanced. Among them, the CsPbBr3 NCs modified with the softest 4-(trifluoromethyl)benzoic acid show near-unity photoluminescence quantum yields, a single-exponential photoluminescence decay kinetics and excellent stability. •Aromatic carboxylic acids were used as surface ligands to modify CsPbBr3 NCs.•The binding of carboxyl group with uncoordinated Pb2+ can passivate the surface defects of CsPbBr3 NCs.•Among modified CsPbBr3 NCs, TFBA-CsPbBr3 NCs have near-unity PLQYs and excellent stability.