Cs ₂ SnI ₆ : A Perovskite‐Based Electromagnetic Wave Absorbing Material

Lead halide perovskites and carbon‐based materials are interesting, high‐performing electromagnetic wave absorbing materials. However, only a few studies have been carried out to examine in detail the electromagnetic wave absorption properties of these materials. Moreover, because most perovskites contain lead and have low structural stabilities, concerns exist about the potential environmental and biological toxicity impacts associated with their use. In this effort, we demonstrate for the first time that the novel, non‐toxic, and lead‐free inorganic halide perovskite Cs 2 SnI 6 absorbs electromagnetic waves. Specifically, we show that the SnI 4 ‐derived Cs 2 SnI 6 perovskite can be synthesized by using a one‐step solution‐based method and that it has an effective absorption bandwidth of 6.4 GHz at a thickness of 1.9 mm. The outstanding performance profile of this material is attributed to dipole‐like oscillation of cations and anions within Cs 2 SnI 6 under alternating electromagnetic wave fields caused by mismatched motion of phases having different charges and masses that leads to dipole polarization. Furthermore, an investigation of sources for this effect provides valuable insights into the interrelationship that exists between impedance matching characteristics and electromagnetic wave absorption performance, which should highly benefit future designs of novel halide perovskite‐based absorbing materials.