Memory properties of (110) preferring oriented CH3NH3PbI3 perovskite film prepared using PbS-buffered three-step growth method

We proposed a PbS-buffered method to fabricate the (110)-textured CH3NH3PbI3 (MAPbI3) film by three-step conversion (PbS → PbI2 → MAPbI3). The PbS buffer layer comprised numerous polyhedron particles was prepared on top of the Glass/indium tin oxide (ITO) via a chemical bath deposition process. Firstly, the PbS was converted to PbI2 by I2 gas annealing that caused a dense and (001)-preferred PbI2. Secondly, the PbI2 was turned into a MAPbI3 film by MAI vapor annealing, of which the degree of preferring orientation of the (110) face was higher and the micrometer grains was more compact than that was prepared by the conventional two-step (PbI2 → MAPbI3) spin-coated MAPbI3. The dense and (001)-textured PbI2, which was converted from the PbS with an appropriate condition, was the key to obtain the (110)-preferred MAPbI3 with a good quality. For comparative study, the memory devices (Glass/ITO/MAPbI3/poly methyl methacrylate (PMMA)/Al) made by the PbS-buffered MAPbI3 and the spin-coated MAPbI3 were both studied. As a result, both of them showed bipolar resistive switching behaviors with an ON/OFF ratio of ~102; whereas the leakage current of the PbS-buffered MAPbI3 sample was 3 orders lower than that of the spin-coated one. The large crystalline grain, high-compact structure and (110) preferred texture of the PbS-buffered MAPbI3 were believed to contribute to such a low leakage current, which is beneficial for the memory application.