A layered (n-C₄H₉NH₃)₂CsAgBiBr₇ perovskite for bipolar resistive switching memory with a high ON/OFF ratio

Lead-based halide perovskites have been proposed as potential candidates for resistive switching memristors due to the high ON/OFF ratio along with millivolt-level low operational voltage. However, lead-free perovskites with 3-dimensional structures, such as Cs₂AgBiBr₆, were reported to suffer from low ON/OFF ratios. We report here that reduction of dimensionality is an effective method to improve remarkably the ON/OFF ratio in lead-free perovskites. Introduction of butylammonium (BA) into the double perovskite Cs₂AgBiBr₆ forms 2-dimensional BA₂CsAgBiBr₇, which is confirmed by the well-developed (00l) peaks from powder X-ray diffraction. A 230 nm thick BA₂CsAgBiBr₇ film is sandwiched in between Ag and Pt electrodes, which demonstrates bipolar resistive switching behavior with a potential ON/OFF ratio up to 10⁷. Reliable and reproducible SET and RESET processes occur at +0.13 V and -0.20 V, respectively. Endurance of 1000 cycles and a retention time of 2 × 10⁴ s are measured. Multi-level storage capability is confirmed by controlling the compliance current. Schottky conduction at the high resistance state (HRS) and ohmic conduction at the low resistance state (LRS) are found to be responsible for resistive switching. The stability test at 85 °C or for 22 days under ambient conditions indicates that BA₂CsAgBiBr₇ is durably operable.