A facile fabrication of lead-free Cs2NaBiI6 double perovskite films for memory device application

The environment-friendly Cs2NaBiI6 double perovskite films have been fabricated using a one-step solution spin coating method in air. The X-ray diffraction analyzer, Ultraviolet-visible spectroscopy, scanning electron microscope, and X-ray photoelectron spectroscopy were carried out to characterize the films. The films were used to prepare the memory devices with the structure of Al/Cs2NaBiI6/ITO. The current−voltage characteristics of the devices clearly showed a bipolar resistive switching behavior. The estimated activation energy (~0.11 eV) proves that the conduction mechanism is mainly derived from the migration of iodine vacancies. Moreover, the devices showed the memory performances with an endurance up to 200 cycles, a higher ON/OFF ratio of over 102, a long retention time ~104 s, and outstanding reproducibility. Especially, the devices still keep excellent memory behaviors with the increase of measurement temperatures up to 403 K or after 90 days exposure in the air. The results indicate that the present double perovskite memory devices with a remarkable stability offer a great potential for future applications.