Cesium lead bromide perovskite nanocrystals synthesized via supersaturated recrystallization at room temperature: comparison of one-step and two-step processes

Abstract

Over more than a decade, lead halide perovskites (LHPs) have been popular as a next-generation semiconductor for optoelectronics. Later, all-inorganic CsPbX₃ (X = Cl, Br, and I) nanocrystals (NCs) were synthesized via supersaturated recrystallization (SR) at room temperature (RT). However, compared to the hot injection (HI) method, the formation mechanism of NCs via SR-RT has not been well studied. Hence, this study will contribute to elucidating SR-RT based on the LaMer model and Hansen solubility parameter. Herein, we also demonstrate the entropy-driven mixing between two dissimilar polar-nonpolar (DMF–toluene) solvents. Next, we find that, in a poor solvent (toluene ≫ DMF in volume), ∼60 nm sized CsPbBr₃ NCs were synthesized in one step, whereas in a marginal solvent (toluene ≈ DMF), ∼3.5 nm sized NCs were synthesized in two steps, indicating the importance of solvent polarity, specifically the ‘solubility parameter’. In addition, in the presence of a CuBr₂ additive, high-quality cubic NCs (with ∼3.8 nm and ∼21.4 nm edge sizes) were synthesized. Hence, through this study, we present a ‘solubility parameter-based nanocrystal-size control model’ for SR-RT processes.