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Anion Exchange and Lateral Heterostructure Formation in Ferromagnetic PEA 2 Cr(Cl,Br) 4 Two-Dimensional Perovskites.

Authors :
Walsh KM
Smith RT
Gamelin DR
Source :
Journal of the American Chemical Society [J Am Chem Soc] 2024 Oct 23; Vol. 146 (42), pp. 29159-29168. Date of Electronic Publication: 2024 Oct 09.
Publication Year :
2024

Abstract

Postsynthetic vapor-phase anion exchange in the ferromagnetic two-dimensional (2D) hybrid metal-halide perovskite, PEA <subscript>2</subscript> CrCl <subscript>4</subscript> (PEA <superscript>+</superscript> = phenethylammonium), is reported. Anion exchange using vaporous trimethylsilyl bromide (TMS-Br) is shown to drive complete conversion of solution-processed PEA <subscript>2</subscript> CrCl <subscript>4</subscript> polycrystalline thin films to PEA <subscript>2</subscript> CrBr <subscript>4</subscript> . Low-temperature magnetic circular dichroism spectroscopy indicates ferromagnetic ordering in these PEA <subscript>2</subscript> CrCl <subscript>4</subscript> and PEA <subscript>2</subscript> CrBr <subscript>4</subscript> films. Via partial anion exchange of exfoliated flakes of PEA <subscript>2</subscript> CrCl <subscript>4</subscript> single crystals, we demonstrate that it is possible to generate abrupt lateral PEA <subscript>2</subscript> CrCl <subscript>4</subscript> /PEA <subscript>2</subscript> CrBr <subscript>4</subscript> magneto-heterointerfaces. Kinetic studies reveal that lateral heterostructure formation is dictated by rapid edge-site halide exchange followed by slower intralayer bromide diffusion, and there is negligible interlayer (3D) bromide or TMS-Br diffusion. The importance of the bulky PEA <superscript>+</superscript> interlayer cation in suppressing 3D diffusion is highlighted by parallel anion-exchange experiments on MA <subscript>2</subscript> CrCl <subscript>4</subscript> (MA <superscript>+</superscript> = methylammonium), which instead show 3D exchange. Comparison of anion-exchange reactions in PEA <subscript>2</subscript> CrCl <subscript>4</subscript> , PEA <subscript>2</subscript> MnCl <subscript>4</subscript> , and PEA <subscript>2</subscript> PbCl <subscript>4</subscript> shows that 2D bromide diffusion is slowest in PEA <subscript>2</subscript> CrCl <subscript>4</subscript> , attributed to the antiferrodistortive ordering found in this composition. In addition to demonstrating both postsynthetic composition control and heterostructure formation in ferromagnetic Cr-based 2D perovskites for the first time, these results also advance our fundamental understanding of ion-exchange processes in this relatively unexplored family of 2D perovskites, broadening opportunities for investigation and control of novel spin effects in low-dimensional metal-halide perovskites.

Details

Language :
English
ISSN :
1520-5126
Volume :
146
Issue :
42
Database :
MEDLINE
Journal :
Journal of the American Chemical Society
Publication Type :
Academic Journal
Accession number :
39383483
Full Text :
https://doi.org/10.1021/jacs.4c11490