ChemInform Abstract: 81Br NQR and 119Sn Moessbauer Study for MSnBr3 (M: Cs and MeNH3).

Abstract

The title compounds, for which successive structural phase transitions are observed by means of 81Br NQR and DTA are isomorphous and have typical cubic perovskite structure at 20 °C. Especially in the case of MeNH3SnBr3 the 81Br NQR and 119Sn Moessbauer spectra change markedly with decreasing temp. suggesting a change of the tin environment from a regular octahedron at 20 °C to a markedly distorted one at 77 K. These finding are interpreted on the basis of the three‐center‐four‐electron bond model.

Local Structure and Dynamics in Methylammonium, Formamidinium, and Cesium Tin(II) Mixed-Halide Perovskites from 119Sn Solid-State NMR

“…Experimentally, we observe that the 119 Sn resonances become narrower as the temperature increases (Figure 7a and Table S1), which shows that T 2 increases with temperature. Since determining the relaxation regime for the quadrupolar partner is not straightforward in this case due to its very large quadrupole coupling constant, 110 we employ the determined activation energy as a constraint to identify the relevant relaxation mechanism. Plotting ln( 119 Sn T 1 /s) as a function of the inverse temperature yields an Arrhenius plot (Figure 7b) from which we determine the activation energy of the process driving the relaxation (Table 1 and Table S2).…”

Phase Evolution in Methylammonium Tin Halide Perovskites with Variable Temperature Solid-State 119Sn NMR Spectroscopy

“…Also, when exposing plants to the maximum safety level of perovskites in soil, most of them revealed signs of lead toxicity and plant death, suggesting that the safety level for lead needs to be lowered. To circumvent these degradation and environmental concerns, some researchers have shifted their focus to lead-free Sn-variants as new solar absorbing materials. − To date, these materials have received far less attention primarily because of their initial weaker photoconversion efficiencies and the tendency of Sn 2+ to readily oxidize to Sn 4+ , ultimately impacting the perovskite structure and optical properties. − However, studies have shown that tin halide perovskites with a cesium cation produce tunable photoluminescence via halide exchange, as well as photocurrents exceeding 22 mA/cm 2 when CsSnI 3 is used as the absorber in perovskite solar cells. , Using a mixed Sn–Pb B-site, a research team reported a hybrid perovskite solar cell with a 50:50 ratio of Sn:Pb (CH 3 NH 3 Sn 0.5 Pb 0.5 I 3 ) with a tailorable band gap and a 4.18% photoconversion efficiency . Despite the challenges faced with tin-based perovskites, in 2014, CH 3 NH 3 SnI 3– x Br x and CH 3 NH 3 SnI 3 were successfully used as light harvesters; demonstrating the vast potential of tin-based perovskites as potential next-generation, environmentally-friendly solar cell materials. , …”