Pb deficiency enables the synthesis of CsPbI3 nanosheets with tunable thickness down to two octahedral layers

CsPbX3 (X = Cl, Br, I) nanosheets have emerged as a promising platform for tuning quantum confinement effects and achieving efficient optoelectronic devices. However, synthesizing uniform CsPbX3 nanosheets with monolayer-level thicknesses remains a challenge due to the fast reaction kinetics. Herein, we develop a synthetic strategy that leverages Pb-deficient precursors to control reaction kinetics. Our experimental investigations indicate that Pb deficiency in the precursors decelerates the crystal growth, offering enhanced dimensional control in CsPbX3 systems. This approach enables the synthesis of uniform CsPbI3 nanosheets with tunable thickness down to two octahedral layers, which exhibit a narrowband emission at 563 nm and high stability against spectral drift. This method is readily extended to CsPbBr3 and CsPbCl3 systems for precise size and shape modulation, thus affording full-color emission tuning within mono-halide perovskites. These findings establish a versatile synthetic strategy poised to advance the design and application of CsPbX3 nanomaterials and other colloidal nanocrystals.