Dimensionality-dependent electronic–ionic transport in a Cs4PbBr6/CsPbBr3 heterojunction

Lead halide perovskites have emerged as promising mixed electronic–ionic conductors owing to their excellent optoelectronic properties and the presence of mobile ionic defects. Because both electronic and ionic transport are strongly governed by crystal structure and dimensionality, understanding their interplay is essential for the development of iontronic devices. Here, we investigate the transport properties of a Cs₄PbBr₆/CsPbBr₃ heterostructure formed through a post-synthetic surface transformation of a pristine 0D Cs₄PbBr₆ single crystal. Temporal current response measurements reveal a pronounced contrast in transport behavior between the two phases. The isolated octahedral framework of Cs₄PbBr₆ suppresses ionic migration, whereas the interconnected Pb–Br–Pb network in CsPbBr₃ facilitates enhanced ion transport. By integrating these structurally distinct phases into a monolithic heterojunction, we observe strongly polarity-dependent transient responses arising from the interplay between electronic carrier injection and ionic defect dynamics at the interface. These findings demonstrate that dimensionality engineering provides an effective strategy for controlling mixed electronic–ionic transport and offers a new design principle for perovskite-based iontronic devices.