Ultrathin Cs3Bi2I9 Nanosheets as an Electronic Memory Material for Flexible Memristors

Methylammonium lead halide (MAPbX 3 ) perovskites have attracted tremendous attention due to their remarkable performances in solar cells, light‐emitting diodes, photodetectors, lasers, and electronic memories. However, the issue of toxicity still greatly restricts their further large‐scale applications. Here, this study presents a series of nontoxic and stable methylammonium (or cesium) bismuth halides A 3 Bi 2 I 9 (A = Cs + and MA + ) nanosheets for using in flexible memories. The ultrathin A 3 Bi 2 I 9 nanosheets can be easily prepared by a dissolution–recrystallization process. This is the first attempt that reports the ultrathin bismuth halides and explores their potential applications in flexible electronic devices. The flexible memristors based on such ultrathin Cs 3 Bi 2 I 9 nanosheets exhibit typical bipolar resistive switching behavior and remarkable characteristics such as high R on / R off ratio (≈10 3 ), very low working voltage (≈0.3 V), and long data retention (>10 4 s), as well as excellent endurability, reproducibility, environmental stability, and flexibility. With such appealing characteristics, the cesium bismuth halide memristors have great potential for practical applications. The results of this work demonstrate that cesium bismuth halide ultrathin nanosheets will be promising candidates for more emerging applications in electronics and optoelectronics such as memories, photodetectors, photovoltaics, and light‐emitting diodes.