Dimensionality-Driven Decoupling of Electronic-Ionic Transport in a Cs4PbBr6/CsPbBr3 Heterojunction

Abstract

Harnessing the interplay between electronic and ionic transport in lead halide perovskites is pivotal for advancing next-generation iontronics. Here, we demonstrate a pronounced disparity in charge transport dynamics enabled by the post-synthetic chemical transformation of a 0D Cs₄PbBr₆ single crystal surface into a 3D CsPbBr₃ phase via controlled Prussian blue treatment. Temporal response measurements reveal a fundamental divergence in transport behavior: while the pristine 0D crystal exhibits high activation barriers and restricted ionic activity due to its isolated octahedral framework, the chemically transformed 3D surface facilitates facile ion migration through continuous Pb-Br-Pb percolative pathways. Leveraging this structural mismatch, we construct a monolithic Cs4PbBr6/CsPbBr3 heterojunction that exhibits strongly polarity-dependent transient responses, characteristic of a memristive diode. We elucidate that this unidirectional ion regulation arises from asymmetric carrier injection at the heterointerface, where the reversible charge neutralization of mobile ions (V_Br⁺+e⇄V_Br⁰) under reverse bias effectively gates the ionic current. These findings establish chemically engineered all-inorganic perovskite heterostructures as a versatile platform for solid-state memory, ionic gating, and neuromorphic computing applications.