Synthesis and Crystal Structure Evolution of Co-Evaporated Cs2AgBiBr6 Thin Films upon Thermal Treatment

Lead-free, highly stable, inorganic double perovskites such as Cs2AgBiBr6 promise to solve two of the main issues that currently hold back the wide-scale application of perovskite-based opto-electronic devices: a lack of stability and the use of toxic lead. Recently, Cs2AgBiBr6 has been shown to be a very promising material for the use in UV and X-ray detectors. In this work, we analyze the film formation of Cs2AgBiBr6 thin films with time-resolved crystal structure analysis using in situ X-ray diffraction (XRD). We present an all-vacuum process for the preparation of Cs2AgBiBr6 thin films via multisource coevaporation followed by thermal annealing. The successful synthesis of the double perovskite phase was confirmed by analysis with XRD and Raman spectroscopy. Our in situ XRD setup allows us to conduct an extensive temperature-dependent analysis of the phase evolution during annealing of the films during synthesis and also during thermal decomposition. We find a decomposition temperature for the Cs2AgBiBr6 thin films at roughly 300 degrees C, in between that of MAPbBr(3) and CsPbBr3.