Structural Stability, Vibrational Properties, and Photoluminescence in CsSnI3 Perovskite upon the Addition of SnF2

• Published in: Inorganic chemistry Vol. 56; no. 1; pp. 84 - 91
• Main Authors: Kontos, Athanassios G, Kaltzoglou, Andreas, Siranidi, Eirini, Palles, Dimitrios, Angeli, Giasemi K, Arfanis, Michalis K, Psycharis, Vassilis, Raptis, Yannis S, Kamitsos, Efstratios I, Trikalitis, Pantelis N, Stoumpos, Constantinos C, Kanatzidis, Mercouri G, Falaras, Polycarpos
• Format: Journal Article
• Language: English
• Published: American Chemical Society 03-01-2017
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.6b02318

The CsSnI3 perovskite and the corresponding SnF2-containing material with nominal composition CsSnI2.95F0.05 were synthesized by solid-state reactions and structurally characterized by powder X-ray diffraction. Both materials undergo rapid phase transformation upon exposure to air from the black orthorhombic phase (B-γ-CsSnI3) to the yellow orthorhombic phase (Y-CsSnI3), followed by irreversible oxidation into Cs2SnI6 within several hours. The phase transition occurs at a significantly lower rate in the SnF2-containing material rather than in the pure perovskite. The high hole-carrier concentration of the materials prohibits the detection of Raman signals for B-γ-CsSnI3 and induces a very strong plasmonic reflectance in the far-IR. In contrast, far-IR phonon bands and a rich Raman spectrum are observed for the Y-CsSnI3 modification below 140 cm–1 with weak frequency shift gradients versus temperatures between −95 and +170 °C. Above 170 °C, the signal is lost due to B-α-CsSnI3 re-formation. The photoluminescence spectra exhibit residual blue shifts and broadening as a sign of structural transformation initiation.