A molecular route to fluoro-perovskite materials: synthesis of CsCaF3 films through a sol–gel/spin-coating process

Fluoride perovskites have recently attracted great attention due to their unique optical properties. The present study reports for the frst time the fabrication of fuoride-based perovskite, CsCaF3, in form of thin flms through a combined sol–gel/spin-coating approach using β-diketonate fuorinated precursors. The entire sol–gel process has been carried out in ethanol solution under acid-catalyzed conditions starting from the β-diketonate complexes, Cs(hfa) and Ca(hfa)2•diglyme•H2O (Hhfa=1,1,1,5,5,5-hexafuoro-2,4-pentanedione; diglyme=2–Methoxyethylether), which act as single sources for metal ions and fuorine. A careful optimization of the process parameters, such as molar ratio of the starting mixture, aging time and annealing temperature, has allowed to produce for the frst time, selectively and reproducibly, transparent and pure CsCaF3 flms. Field-emission scanning electron microscopy and energy dispersive X-ray analyses highlight the formation of flms with compact morphologies having a 1:1 stoichiometric ratio of Cs:Ca, uniform throughout the flm and compatible with the CsCaF3 phase identifed through X-ray difraction analysis.