Microfluidic synthesis of hollow CsPbBr₃ perovskite nanocrystals through the nanoscale Kirkendall effect

All inorganic metal halide perovskite nanocrystals (NCs) have attracted much attention for their outstanding optoelectronic properties, which can be tuned by the composition, surface, size and morphology in nanoscale. Herein, we report the microfluidic synthesis of hollow CsPbBr₃ perovskite NCs through the nanoscale Kirkendall effect. The formation mechanism of the hollow structure (Kirkendall void) controlled by the temperature, flow rate, ratios of precursors and ligands was investigated. Compared with the solid CsPbBr₃ NCs of the same size, the hollow CsPbBr₃ NCs exhibit blue shifts in ultraviolet−visible (UV−vis) absorption and photoluminescence (PL) spectra, and remarkably longer PL average lifetime (~ 98.2 ns). Quantum confinement effect, inner surface induced additional trap states and lattice strain of the hollow CsPbBr₃ NCs were discussed in understanding their unique optoelectronic properties. The hollow CsPbBr₃ NC based photodetector exhibits an outstanding negative photoconductivity (NPC) detectivity of 8.9 × 10¹² Jones. They also show potentials in perovskite NC based photovoltaic and light emitting diodes (LEDs).