Influence of hidden halogen mobility on local structure of CsSn(Cl1−xBrx)3 mixed-halide perovskites by solid-state NMR. Issue 9 (20th January 2021)

• Record Type: Journal Article
• Authors: Karmakar, Abhoy; Bhattacharya, Amit; Sarkar, Diganta; Bernard, Guy M.; Mar, Arthur; Michaelis, Vladimir K.
• Is Part Of: Chemical science. Volume 12:Issue 9(2021)
• Page Start: 3253
• Page End: 3263
• Publication Date: 2021-01-20
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0sc05614f
• Languages: English
• ISSNs: 2041-6520

Abstract

Abstract : Unravelling the atomic-level chemical structure, slow phase conversion or degradation pathways and rapid halogen hopping of cesium tin(ii ) halide perovskites using solid-state 119 Sn and 133 Cs NMR spectroscopy. Abstract : Tin halide perovskites are promising candidates for lead-free photovoltaic and optoelectronic materials, but not all of them have been well characterized. It is essential to determine how the bulk photophysical properties are correlated with their structures at both short and long ranges. Although CsSnCl3 is normally stable in the cubic perovskite structure only above 379 K, it was prepared as a metastable phase at room temperature. The transition from the cubic to the monoclinic phase, which is the stable form at room temperature, was tracked by solid-state 133 Cs NMR spectroscopy and shown to take place through a first-order kinetics process. The complete solid solution CsSn(Cl1− x Br x )3 (0 ≤ x ≤ 1) was successfully prepared, exhibiting cubic perovskite structures extending between the metastable CsSnCl3 and stable CsSnBr3 end-members. The NMR spectra of CsSnBr3 samples obtained by three routes (high-temperature, mechanochemical, and solvent-assisted reactions) show distinct chemical shift ranges, spin-lattice relaxation parameters and peak widths, indicative of differences in local structure, defects and degree of crystallinity within these samples. Variable-temperature 119 Sn spin-lattice relaxation measurements reveal spontaneous mobility of Br atoms in CsSnBr3 . The degradation of CsSnBr3, exposed to an ambient atmosphere for nearly a year, was monitored by NMR spectroscopy and powder X-ray diffraction, as well as by optical absorption spectroscopy.