Vacuum-Deposited Cesium Tin Iodide Thin Films with Tunable Thermoelectric Properties.

Most current thermoelectric materials have important drawbacks, such as toxicity, scarceness, and peak operating temperatures above 300 °C. Herein, we report the thermoelectric properties of different crystalline phases of Sn-based perovskite thin films. The 2D phase, CsSnI, is obtained through vacuum thermal deposition and easily converted into the black β phase of CsSnI (B-β CsSnI) by annealing at 150 °C.