Stabilizing CsPbBr ₃ Nanocrystals by Cotreatment with Inorganic and Organic Ligands

Perovskite nanocrystals (NCs) exhibit intrinsic chemical instability due to their ionic nature. This property renders them susceptible to structural degradation and optical performance deterioration upon exposure to various cations (both inorganic and organic ions). For instance, Cs+ can induce phase transformation and photoluminescence quenching in the CsPbBr3 NCs. In this work, we found that externally introduced metal cations exert diverse effects (classified as three types) on the structure and optical properties of CsPbBr3 NCs. Notably, certain cations, such as Zn2+ and Cd2+, can bind to the surface and shield nanocrystals against the detrimental effects of exogenous cations. The protection effects were observed by both optical spectroscopy and transmission electron microscopy. Pretreatment with both ZnBr2 and CdBr2 significantly enhances the resistance of CsPbBr3 NCs to structurally or optically detrimental exogenous cations (Cs+). Moreover, with didodecyldimethylammonium bromide (DDAB) simultaneously incorporated in this pretreatment, the pretreated CsPbBr3 NCs exhibit enhanced resistance to polar solvents (e.g., ethanol), manifesting as keeping stable and bright even when exposed to 20% (volume percentage) of ethanol. These three components (ZnBr2, CdBr2, and DDAB) exhibit complementary functions for chemical stability. This stability-preserving strategy is expected to enhance the robustness of perovskite NCs against complex chemical conditions encountered during the device fabrication process (solution processing and interlayer interface engineering) and operating environments.