Microampere-level piezoelectric energy generation in Pb-free inorganic halide thin-film multilayers with Cu interlayers

Although asymmetric perovskite halides are known to possess viable piezoelectricity, their performance of energy harvesting has been limitedly reported. Herein, we propose the first Pb-free inorganic halide-based thin film harvester having strong capability of power-generation, particularly with additional efforts to enhance the device performance using an unprecedented multilayer structure incorporated with metallic interlayers. Representative high-quality CsSnI₃ thin films were prepared by one-step spin coating, and up to four layers were stacked with alternating Cu interlayers. Impressive piezoelectric energy harvesting characteristics of ~22.9 V and ~1233 nA were attained for the four-layered halide structure after poling, which are highest values recorded thus far for perovskite halide thin films. The origin of the enhanced energy-generation is believed to be directly associated with the increased SnI₆-octahedra distortion (with off-centering of Sn atoms) by poling and the extra space-charge polarization by Cu interlayers.