Controlled Synthesis of Asymmetric Lead Halide Perovskite Nanocrystals with Excellent Stability

Nanoplatelets (NPLs) share excellent luminescent properties with their symmetric quantum dots counterparts, and entail special characters benefiting from the shape, like the thickness-dependent bandgap and anisotropic/polarized luminescence. However, the mechanism under formation of asymmetric perovskite NPLs is unclear, and thus the modification for high-quality perovskite NPLs is still unsatisfying. Here, we unveil the intrinsic parameters for synthesizing asymmetric NPLs and report stable CsPbI₃ NPLs obtained by accelerating the crystallization process. By this kinetic control, we tune the rectangular NPLs into quasi-square NPLs, where enlarged width endows the NPLs with a lower surface-area-to-volume ratio (S/V ratio), leading to lower surficial energy and thus improved endurance against NPL fusion (cause for spectral shift or phase transformation). The accelerated crystallization is enabled by preparing a precursor with complete transformation of PbI₂ into intermediates (PbI₃^-), through an additional iodide supplier (<i>e.g.</i>, zinc iodide). The excellent color stability of our materials remains in the light-emitting diodes under various bias stress.