Double passivation of alkali metal ion and organic ligand towards enhanced photoluminescence and stability of Cs3Cu2X5 (X Cl, Br and I) nanocrystals

Intrinsic and surface defects are the crucial factors that affect the stability and luminescence efficiency of nanocrystals (NCs). Ion-doping and surface passivation are considered as the most effective strategies to suppress the intrinsic and surface defects of NCs, respectively. Herein, an efficient and facile double passivation process, simultaneously realizes ion-doping and surface passivation, for Cs3Cu2X5 (XCl, Br and I) NCs is developed by using potassium oleate (K-OA) as passivator. K ion is used as ion-doping passivation and OA ion is used as the organic ligand for surface passivation of NCs. Compared to the free passivated NCs, the Photoluminescence quantum yield (PLQYs) of dual-passivated Cs3Cu2X5 (XCl, Br and I) NCs increase significantly from 2.87%, 11.6% and 49.4–31%, 69.9%, and 97.2%, respectively. Moreover, the stability of proposed NCs is greatly improved (Cs3Cu2Cl5 NCs maintain 63% of PL efficiency after 100 h, Cs3Cu2Br5 and Cs3Cu2I5 NCs maintain 65% and 97% of PL efficiency after 100 days, respectively) at 50–86% relative humidity and room temperature under ambient atmosphere.