Lanthanide-doping enables kinetically controlled growth of deep-blue two-monolayer halide perovskite nanoplatelets

Impurity doping has been widely applied in nanomaterial synthesis for modulating the crystallographic phase, morphology, and size of nanocrystalline materials, but mostly by altering thermodynamic equilibria of final products. Here, we report the use of lanthanide dopants to manipulate the growing kinetics of halide perovskite nanocrystals to enable the preparation of highly anisotropic two-dimensional (2D) CsPbBr3-based nanoplatelets with precisely controlled thickness. We demonstrate that the incorporation of trivalent lanthanides increases the energy barrier in growing three-monolayer (3 ML) CsPbBr3 from a 2 ML intermediate. It enables the growth of thermodynamically unfavorable 2 ML CsPbBr3 products through kinetic control. This finding provides a novel approach for dimensional control of perovskite nanocrystals with strong quantum confinement. It offers opportunities to generate deep-blue emitting (at 430 nm) CsPbBr3:Lu3+ nanoplatelets with good structural- and photo-stabilities potentially useful for many applications including light-emitting, lasers, and photocatalysis.