Triangulating Dopant-Level Mn(II) Insertion in a Cs2NaBiCl6 Double Perovskite Using Magnetic Resonance Spectroscopy

Karmakar, A and Bernard, GM and Pominov, A and Tabassum, T and Chaklashiya, R and Han, S and Jain, SK and Michaelis, VK (2022) Triangulating Dopant-Level Mn(II) Insertion in a Cs2NaBiCl6 Double Perovskite Using Magnetic Resonance Spectroscopy. In: Journal of the American Chemical Society, 15 (8). 4485- 4499.

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Abstract

Lead-free metal halide double perovskites are gaining increasing attention for optoelectronic applications. Specifically, doping metal halide double perovskites using transition metals enables broadband tailorability of the optical bandgap for these emerging semiconducting materials. One candidate material is Mn(II)-doped Cs2NaBiCl6, but the nature of Mn(II) insertion on chemical structure is poorly understood due to low Mn loading. It is critical to determine the atomic-level structure at the site of Mn(II) incorporation in doped perovskites to better understand the structure-property relationships in these materials and thus to advance their applicability to optoelectronic applications. Magnetic resonance spectroscopy is uniquely qualified to address this, and thus a comprehensive three-pronged strategy, involving solid-state nuclear magnetic resonance (NMR), high-field dynamic nuclear polarization (DNP), and electron paramagnetic resonance (EPR) spectroscopies, is used to identify the location of Mn(II) insertion in Cs2NaBiCl6. Multinuclear (23Na, 35Cl, 133Cs, and 209Bi) one-dimensional (1D) magnetic resonance spectra reveal a low level of Mn(II) incorporation, with select spins affected by paramagnetic relaxation enhancement (PRE) induced by Mn(II) neighbors. EPR measurements confirm the oxidation state, octahedral symmetry, and low doping levels of the Mn(II) centers. Complementary EPR and NMR measurements confirm that the cubic structure is maintained with Mn(II) incorporation at room temperature, but the structure deviates slightly from cubic symmetry at low temperatures (<30 K). HYperfine Sublevel CORrelation (HYSCORE) EPR spectroscopy explores the electron-nuclear correlations of Mn(II) with 23Na, 133Cs, and 35Cl. The absence of 209Bi correlations suggests that Bi centers are replaced by Mn(II). Endogenous DNP NMR measurements from Mn(II) → 133Cs (<30 K) reveal that the solid effect is the dominant mechanism for DNP transfer and supports that Mn(II) is homogeneously distributed within the double-perovskite structure. © 2023 American Chemical Society.

Item Type:	Journal Article
Publication:	Journal of the American Chemical Society
Publisher:	American Chemical Society
Additional Information:	The copyrights of this article belong to American Chemical Society.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	14 Mar 2023 05:26
Last Modified:	14 Mar 2023 05:26
URI:	https://eprints.iisc.ac.in/id/eprint/80902

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