Perovskite nanocrystals have emerged as promising constituents for optoelectronic applications due to their exceptional and tunable properties and their scalable synthesis. However, the integration of perovskite nanocrystals into devices faces challenges such as defects, poor carrier transport, and ligand interference. We present a liquid-in-liquid impingement process that results in the mechanical coalescence of lead-bromide perovskite nanocrystals into large, free-standing flakes under ambient conditions. This approach leverages localized shear forces generated during impingement to achieve nanocrystal sintering, ligand removal, and solvent exchange. Microscopic analysis reveals the formation of large surface-sintered domains that overcome issues of defectiveness and environmental stability. This improvement results in significant improvements of the nanocrystal properties compared to random perovskite assemblies. We demonstrate a significant decrease in trap density leading to enhanced chemical stability, charge transport and radiative charge recombination. Significant improvements in carrier mobility enable the fabrication of photodetectors with exceptional response speed and sensitivity, surpassing conventional methods. These findings highlight the potential of liquid impingement processing for advancing perovskite-based optoelectronics through scalable and efficient nanocrystal assembly.
