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Structure–Band Gap Relationships in Hexagonal Polytypes and Low-Dimensional Structures of Hybrid Tin Iodide Perovskites
Abstract
The present study deals with the structural characterization and classification of the novel compounds <b>1</b>–<b>8</b> into perovskite subclasses and proceeds in extracting the structure–band gap relationships between them. The compounds were obtained from the employment of small, 3–5-atom-wide organic ammonium ions seeking to discover new perovskite-like compounds. The compounds reported here adopt unique or rare structure types akin to the prototype structure perovskite. When trimethylammonium (TMA) was employed, we obtained TMASnI<sub>3</sub> (<b>1</b>), which is our reference compound for a “perovskitoid” structure of face-sharing octahedra. The compounds EASnI<sub>3</sub> (<b>2b</b>), GASnI<sub>3</sub> (<b>3a</b>), ACASnI<sub>3</sub> (<b>4</b>), and IMSnI<sub>3</sub> (<b>5</b>) obtained from the use of ethylammonium (EA), guanidinium (GA), acetamidinium (ACA), and imidazolium (IM) cations, respectively, represent the first entries of the so-called “hexagonal perovskite polytypes” in the hybrid halide perovskite library. The hexagonal perovskites define a new family of hybrid halide perovskites with a crystal structure that emerges from a blend of corner- and face-sharing octahedral connections in various proportions. The small organic cations can also stabilize a second structural type characterized by a crystal lattice with reduced dimensionality. These compounds include the two-dimensional (2D) perovskites GA<sub>2</sub>SnI<sub>4</sub> (<b>3b</b>) and IPA<sub>3</sub>Sn<sub>2</sub>I<sub>7</sub> (<b>6b</b>) and the one-dimensional (1D) perovskite IPA<sub>3</sub>SnI<sub>5</sub> (<b>6a</b>). The known 2D perovskite BA<sub>2</sub>MASn<sub>2</sub>I<sub>7</sub> (<b>7</b>) and the related all-inorganic 1D perovskite “RbSnF<sub>2</sub>I” (<b>8</b>) have also been synthesized. All compounds have been identified as medium-to-wide-band-gap semiconductors in the range of <i>E</i><sub>g</sub> = 1.90–2.40 eV, with the band gap progressively decreasing with increased corner-sharing functionality and increased torsion angle in the octahedral connectivity- Text
- Journal contribution
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- structure types
- band gap
- IMSnI 3
- prototype structure perovskite
- face-sharing octahedral connections
- 2 D perovskite BA 2 MASn 2
- compounds EASnI 3
- halide perovskites
- perovskite IPA 3 SnI 5
- octahedral connectivity
- corner-sharing functionality
- perovskite subclasses
- reference compound
- ACA
- TMASnI 3
- Low-Dimensional Structures
- IPA 3 Sn 2
- Hexagonal Polytypes
- 3 b
- ammonium ions
- 6 b
- perovskites GA 2 SnI 4
- face-sharing octahedra
- crystal structure
- halide perovskite library
- perovskite-like compounds
- medium-to-wide-band-gap semiconductors
- study deals
- Hybrid Tin Iodide Perovskites
- E g
- crystal lattice
- torsion angle