Fibrous FAPbI₃ Perovskite Resistive Random Access Memory

With the rapid development of information technology,a huge amount of data needs to be processed urgently,so the capability of data storage and processing with memory devices has put forward higher requirements.With the advent of post-Moore era and the entry of complementary metal oxide semiconductor（CMOS）technology into the nanometer scale,the further reduction in the size of traditional silicon-based memory devices faces both physical and technical bottlenecks.Resistive random access memory,as a new type of non-volatile memory,has become a hot research topic in recent years because of its simple structure,fast read/write speed,high cycle tolerance,long data retention time,good size reduction and multi-level storage.Amongst,the resistance random access memory based on organic-inorganic hybrid perovskite materials is expected to become the next generation of nonvolatile storage technology due to the advantage of easy low-temperature solution preparation.However,the poor environmental stability and flexibility restrict its commercial development.The device flexibility can be improved by adding the flexible polymer additives into organic-inorganic hybrid perovskite materials.In this paper,the fibrous FAPbI₃ perovskite resistive random access memory with excellent flexibility was prepared.In this work,the long-chain flexible polymer polyvinylamine iodate（PVAm·HI）were introduced as the perovskite nucleation site and crystallization template,which can improve the environmental stability and flexibility of the device.Finally,a woven resistive random access memory device with excellent performance was obtained.（1）In this work,a fibrous resistive random access memory device with the structure of Al@FAPbI₃/Al（FCPe-RRAM）was prepared by a simple solution dip-coating method.The crystallization behavior of FAPbI₃ on Al fiber was investigated by SEM,XRD and FTIR.The optimal preparation process conditions for dense and uniform fibrous FAPbI₃ film were achieved,together with the results of AFM,I-V test.At the same time,the intersection position,voltage scanning direction,bending angle,test temperature were investigated,indicating that the optimized fiber resistive random access memory device shows the excellent resistive switching performance.The optimized device exhibits the bipolar resistance behavior,with the maximum ON/OFF ratio of 10⁷,the data retention time of 10⁴ s and the cycle tolerance test of 500 cycles,suggesting the good resistance storage performance.The I-V fitting analysis shows that the resistance behavior is caused by the formation and fracture of iodine vacancy conductive filaments derived from thermal-electron emission mechanism.（2）FAPbI₃ perovskite was modified by adding long chain flexible polymer PVAm·HI to prepare the fibrous Al@FAPbI₃:PVAm·HI/Al devices.The I-V test results show that with the increase of PVAm·HI content,the ON/OFF ratio first increases and then decreases,which reaches the maximum value of 10⁹ at the doping ratio of 2%.In here,the polymer plays the role of nucleation site and crystallization template.Notably,the ON/OFF ratio is increased about two orders of magnitude compared to the unmodified devices.The resistance behavior can still be maintained after 20 days in air,indicating the improvement of environmental stability.The improved environmental stability is attributed to the structure and morphology of the polymer.（3）The 2%PVAm·HI modified Al@FAPbI₃:PVAm·HI/Al fibers and bare Al fibers were woven into 5×5 arrays.The results showed that the resistive switching performance is still maintained in array even after 100 consecutive folds at a fold radius of 10 mm,indicating good flexibility.It is promising to expand the array/layer to achieve the huge storage amount.