Synergistic passivation of high stability CsPb(Br/I)3 perovskite quantum dots with double ligands for WLEDs

The all-inorganic perovskite CsPbI3 quantum dots are difficult to achieve pure red stable luminescence due to their poor lattice thermodynamic stability and non-radiative recombination loss caused by surface halide vacancies. Therefore, the pure red perovskites are usually achieved by mixing the composition of halides (Br and I). In this work, CsPb(Br/I)3 quantum dots (QDs) were synthesized by the hot-injection method under the synergistic effect of homophthalic acid (HA), 2-bromoethanesulphonic acid sodium salt (SBES), and oleylamine (OAm). By adjusting the molar ratio of passivates, the synergistic effect of multiple ligands can not only passivate the unliganded Pb2+-related defects on the surface of NCs, but also increase the formation energy of halide vacancies. Meanwhile, due to the bidentate structure of HA, smaller size of perovskites nanocrystals were obtained. Eventually, synergistic boost in device performance is achieved for color-by-blue white light-emitting diodes (WLEDs) with CIE coordinates of (0.3319, 0.3297) and have an external quantum efficiency (EQE) of 10.13%. This strategy paves an efficient way for improving the efficiency and stability of CsPb(Br/I)3 NCs.