Quasi-2D Halide Perovskite Memory Device Formed by Acid–Base Binary Ligand Solution Composed of Oleylamine and Oleic Acid

Organometal halide perovskite materials are receiving significant attention for the fabrication of resistive-switching memory devices based on their high stability, low power consumption, rapid switching, and high ON/OFF ratios. In this study, we synthesized 3D FAPbBr3 and quasi-2D (RNH3)2(FA)1Pb2Br7 films using an acid–base binary ligand solution composed of oleylamine (OlAm) and oleic acid in toluene. The quasi-2D (RNH3)2(FA)1Pb2Br7 films were synthesized by controlling the protonated OlAm (RNH3+) solution concentration to replace FA+ cations with large organic RNH3+ cations from 3D FAPbBr3 perovskites. The quasi-2D (RNH3)2(FA)1Pb2Br7 devices exhibited nonvolatile write-once read-many (WORM) memory characteristics, whereas the 3D FAPbBr3 only exhibited hysteresis behavior. Analysis of the 3D FAPbBr3 device indicated operation in the trap-limited space-charge-limited current region. In contrast, quasi-2D (RNH3)2(FA)1Pb2Br7 devices provide low trap density that is completely filled by injected charge carriers and then subsequently form conductive filaments (CFs) to operate as WORM devices. Nanoscale morphology analysis and an associated current mapping study based on conductive atomic force microscopy measurements revealed that perovskite grain boundaries serve as major channels for high current, which may be correlated with the conductive low-resistive-switching behavior and formation of CFs in WORM devices.