Synergistic Ligand and Composition Control for Bright and Stable CsPbBr3/Cs4PbBr6 Core/Shell Colloidal Perovskite Nanocrystals

Abstract

Lead halide colloidal perovskite nanocrystals (CPNCs) have emerged as promising candidates for next-generation optoelectronics owing to their outstanding optical properties; however, their intrinsic instability against environmental stimuli remains a critical bottleneck. Herein, we report the synthesis of highly stable, colloidally dispersible CsPbBr3/Cs4PbBr6 single core/single shell CPNCs via a synergistic approach that combines an oleylamine-driven surface phase transition with a controlled Cs-rich environment. To overcome the sensitivity of the core/shell formation to interdependent synthesis parameters, we employ a machine-learning-assisted workflow. A random forest classifier is utilized to identify the optimal synthesis window with a prediction accuracy of 97.3%, enabling the precise regulation of shell growth. The resulting core/shell CPNCs exhibit a uniform rhombohedral morphology and maintain a Type-I band alignment, which preserves the excellent optical properties of the CsPbBr3 CPNC core while confining charge carriers for efficient radiative recombination. Furthermore, the Cs4PbBr6 shell acts as a robust barrier, providing superior stability against harsh conditions, including exposure to polar solvents (acetone), high temperature (85 °C), and high humidity (85% RH). These CsPbBr3/Cs4PbBr6 core/shell CPNCs retain high colloidal dispersibility, offering a solution-processable material for robust perovskite-based optoelectronic devices.