Controlling Electronic-Ionic\nKinetics via Size Engineering\nin CsPbBr<sub>3</sub> Perovskite Nanocrystals

Owing to the exceptional photovoltaic and optoelectronic\nproperties\nof metal halide perovskites, they have sparked an intensive interest\nin the research community. CsPbBr<sub>3</sub> perovskite nanocrystals\n(NCs) have come into sight due to their versatile properties that\ncan be achieved through structural modification. While the prior research\non perovskite nanocrystals has focused mainly on tuning optical and\nelectronic properties, the understanding of their electronic-ionic\nkinetics still remains a significant research gap. In this work, we\nexplore how the size of CsPbBr<sub>3</sub> NCs impacts their electronic-ionic\nproperties by using electrochemical impedance spectroscopy (EIS).\nWe systematically tune NC size and investigate the resulting dielectric\nproperties, conductivity, and capacitance. Notably, larger NCs exhibit\nanomalous behavior similar to that of perovskite polycrystalline thin\nfilms in the range of 0.4–0.6 V, indicating strong electronic-ionic\ncoupling. Conversely, smaller NCs display weak electronic-ionic coupling\ndue to ion localization. Additionally, this study sheds light on the\nelectronic-ionic behavior of NCs approaching quantum confinement with\na size reduction, suggesting opportunities for defect engineering.\nUltimately, this work will pave the way for developing advanced electronic\ndevices utilizing perovskite nanocrystals.