Highly stable CsPbBr₃ perovskite phases from new lead β-diketonate glyme adducts

Lead is one of the key metals of the all-inorganic lead halide perovskites. This work tailors novel architectures of lead's coordination sphere using a β-diketone (H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione) and a glyme (monoglyme, diglyme, triglyme, or tetraglyme) ligand. The coordination chemistry and thermal behaviour of these "Pb(hfa)₂·glyme" adducts have been analysed through FT-IR spectroscopy, ¹H and ¹³C NMR analyses, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Single-crystal X-ray diffraction studies provide evidence of the formation of a monomeric Pb(hfa)₂·monoglyme structure. In order to validate the potentiality of these "Pb(hfa)₂·glyme" precursors for the fabrication of Pb-based halide perovskites, a facile, one-step and low-temperature solution approach has been applied to prepare CsPbBr₃ microcrystals with a process carried out in air under atmospheric pressure. Pure stoichiometric CsPbBr₃ powders, obtained using Cs(hfa) and Br₂ as cesium and bromide sources, respectively, show excellent stability under atmospheric conditions. Better results are obtained in terms of yield and stability from the diglyme and tetraglyme lead adducts. Field emission scanning electron microscopy (FE-SEM) indicates a good uniform morphology of cubic grains, while the structure and the 1 : 1 : 3 stoichiometry of Cs : Pb : Br are confirmed by X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX), respectively. Tauc plots derived from absorption spectroscopy point to optical energy band-gaps (E_g) in the 2.21-2.27 eV range, in agreement with literature data. The present research elucidates the potential of these novel "Pb(hfa)₂·glyme" adducts as promising lead precursors for CsPbBr₃ perovskite synthesis, paving the way for their implementation in various technological applications.