CsPbI₃ Perovskite Quantum Dot-Based WORM Memory Device with Intrinsic Ternary States

The migration of mobile ionic halide vacancies is usually considered detrimental to the performance and stability of perovskite optoelectronic devices. Taking advantage of this intrinsic feature, we fabricated a CsPbI₃ perovskite quantum dot (PQD)-based write-once-read-many-times (WORM) memory device with a simple sandwich structure that demonstrates intrinsic ternary states with a high ON/OFF ratio of 10³:10²:1 and a long retention time of 10⁴ s. Through electrochemical impedance spectroscopy, we proved that the resistive switching is achieved by the migration of mobile iodine vacancies (V_Is) under an electric field to form conductive filaments (CFs). Using in situ conductive atomic force microscopy, we further revealed that the multilevel property arises from the different activation energies for V_Is to migrate at grain boundaries and grain interiors, resulting in two distinct pathways for CFs to grow. Our work highlights the potential of CsPbI₃ PQD-based WORM devices, showcasing intrinsic multilevel properties achieved in a simple device structure by rationally controlling the drift of ionic defects.