Emission variation and spontaneous deformation of CsPbBr3 perovskite nanoplatelets at low concentrations

Abstract

Due to the unique structural and optical anisotropy, colloidal quasi-two-dimensional nanoplatelets (NPLs) have been proposed as an important material platform for realizing quantum information technology. However, the optical and structural instability of emerging perovskite NPLs after rapid dilution is preventing such studies, along with an unknown intermediate evolution process. Herein, we investigate the photoluminescence evolution of CsPbBr₃ NPLs during stepwise dilutions. Upon decreasing the concentration, a red shift of the emission peak can be observed in CsPbBr₃ NPLs with different thicknesses and synthesis methods. The dilution ripening mechanism dominates this red-shifted photoluminescence, in which larger NPLs capture monomers when smaller NPLs are dissolved, and then the accumulated monomers increase the lateral size and thickness of large NPLs. Interestingly, the simple aging treatment can help improve the dilution stability of thicker NPLs of the hot-injection method. Moreover, it is confirmed that the dilution ripening effect can be suppressed by introducing PbBr₂-saturated solution or exchanging pristine ligands with stronger binding ligands such as lecithin.