Deposition of CsFAPbI₃ thin films by single source flash evaporation

Abstract

Formamidinium-cesium lead iodide (CsFAPbI3) is a promising perovskite material for photovoltaic applications with a suitable bandgap of 1.45 eV and excellent optoelectronic properties. In this work, CsFAPbI3 perovskite thin films were deposited by single-source flash evaporation on glass substrates using presynthesized crystalline powders as the source material in which the source challenges of simultaneously controlling the evaporation of organic and inorganic sources are avoided. The structural properties of the powders were evaluated by X-ray diffraction, thermal properties by TGA analysis and optical properties by UV-Vis absorption. We find that the formation of mixed phases is inevitable in flash evaporation of thin films. This undesirable phase could reduce the optical bandgap and the thermal stability which can affect the performance of the thin films. To obtain the cubic phase, a post-annealing process should be employed. We carried out structural, morphological, and optical characterizations to determine the phase purity in the films. These preliminary results suggest that flash evaporation deposition parameters can be optimized to understand the formamidinium evaporation and condensation dynamics for improve the properties of CsFAPbI3 perovskite thin films.