A Polyanionic Strategy to Modify the Perovskite Grain Boundary for a Larger Switching Ratio in Flexible Woven Resistive Random-Access Memories

The intergranular interface modification of organic–inorganic hybrid perovskites (OHP) is an important issue to regulate the flexibility, stability, and resistive switching (RS) performance of resistive random-access memories (RRAMs). A novel strategy of polymer additives for OHP intergranular interface modification is explored in this work with the polyanionic backbone to improve the distribution of cage-shaped cavity molecules at the perovskite grain boundaries. Specifically speaking, poly(1-adamantylammonium acrylate) (PADAm) is first synthesized through the acid–base reaction of polyacrylic acid with 1-adamantylamine to simultaneously realize the introduction of a cage-shaped cavity molecule and the polyanionic backbone. Herein, organic ammonium cations 1-adamantylammonium (ADNH3+) in PADAm are applied as the cage-shaped cavity molecules to tune the dielectric property by being anchored at the perovskite grain boundaries. Meanwhile, polyacrylic anions in PADAm play the role of the polyanionic backbone to produce the more uniform distribution of ADNH3+. Simultaneously, the flexibility and stability of OHP RRAM devices are also improved due to the introduction of the polyanionic backbone. Consequently, the 4% ADNH3I-modified planar device exhibits the stable nonvolatile RS behavior with an on/off ratio of ∼104, even with one-month exposure under an ambient environment. Importantly, the introduction of PADAm in the flexible fibrous crosspoint of functional fiber Al@MAPbI3:PADAm and bare Al fiber further increases the on/off ratio to 108 due to the effectively improved distribution of hollow cage-shaped ADNH3+ at the perovskite intergranular interfaces together with the application of the fibrous crosspoint device configuration. Especially, these excellent crosspoint RRAM devices can be integrated into the woven fibrous RRAM array in the thermal plastic packaging configuration. In addition, the excellent multilevel RS behavior can also be realized in the woven fibrous RRAM array, indicating potential high-density data storage. This work provides a novel strategy of polymer additives bearing the polyanionic backbone to improve the flexibility, stability, and RS performance of perovskite RRAM devices.