¹²⁷I and ²⁰⁷Pb Solid-State NMR Spectroscopy and Nuclear Spin Relaxation in PbI₂: A Preliminary Study

Abstract

Lead iodide is a layered structure that experiences polytypism. The 2H polytype contains high rates of iodine vacancies but retains its stoichiometry. This characteristic feature makes it potentially useful for many practical applications. The hopping of iodine ions among vacancies is the dominant motion in the 2H polytype. We present a preliminary 127 I and 207 Pb solid-state nuclear magnetic resonance (NMR) spectroscopy and spin−lattice relaxation study of the 2H polytype below 400 K. We present reasonable models for the solid-state NMR results in terms of the effects of iodine hopping and lattice vibrations.

The Nature of Ion Conduction in Methylammonium Lead Iodide: A Multimethod Approach

“…A similarly low upper limit for the diffusion coefficient of Pb (4×10 −15 cm 2 s −1 at 343 K) is derived from 207 Pb NMR spectra. The position of the 207 Pb signal in MAPbI 3 at room temperature is in good agreement with what expected for Pb 2+ ions coordinated to iodine and shifted downfield with respect to pure PbI 2 (Figure a). The position of this peak prior to the measurements was estimated by DFT calculations (Supporting Information, Section 14).…”

“…Inset: Spin‐lattice relaxation T 1 as a function of temperature. The dependence is rather weak and is similar to what was reported for pure PbI 2 . b) Temperature dependences of the 207 Pb chemical shift and FWHM.…”

The Nature of Ion Conduction in Methylammonium Lead Iodide: A Multimethod Approach

“…As imilarly low upper limit for the diffusion coefficient of Pb (4 10 À15 cm 2 s À1 at 343 K) is derived from 207 Pb NMR spectra. Theposition of the 207 Pb signal in MAPbI 3 at room temperature is in good agreement with what expected for Pb 2+ ions coordinated to iodine [48] and shifted downfield with respect to pure PbI 2 (Figure 4a). Thep osition of this peak prior to the measurements was estimated by DFT calculations (Supporting Information, Section 14).…”

“…The dependence is rather weak and is similar to what was reported for pure PbI 2 . [48] b) Temperatured ependences of the 207 Pb chemical shift and FWHM. Solid lines are aguide to the eye.…”

Nonexponential 1H spin–lattice relaxation and methyl group rotation in molecular solids

“…The parameter θ or M(0) should still be an adjustable parameter to eliminate the possibility of making significant systematic errors in fitting parameters [64].…”