Epitaxial Electrodeposition of BiI3 and Topotactic Conversion to Highly Ordered Solar Light-Absorbing Perovskite (CH₃NH₃)₃Bi₂I₉
Highly ordered, epitaxial semiconductor thin films have low defect densities and excellent photophysical properties that are desired for optoelectronic devices. In this work, the epitaxial films of BiI3 are electrodeposited onto Au(111) substrates, and these films are removed by epitaxial lift-off to produce free-standing, single-crystal-like foils of BiI3. The two-dimensional (2D) layering of the BiI3 van der Waals solid allows for the epitaxial lift-off, and it provides a pathway to producing other important materials. The epitaxial films of the solar light-absorbing perovskite (CH3NH3)3Bi2I9 are produced in a solution from BiI3 by topotactic transformation. Epitaxially grown BiI3 shows a 2D-nanodisc-like morphology and highly ordered  out-of-plane orientation having the epitaxial relationship with the substrate as BiI3(0001)[1̅1̅20 ± 3°]//Au(111)[1̅1̅2], determined by X-ray pole figures. The lattice mismatch is minimized by the (±)3° rotation of the film relative to the substrate. The X-ray rocking curve shows that single crystal like BiI3 has a mosaic spread with full width at half-maximum (FWHM) of about ∼0.69°. The topotactic transformation of BiI3 produces a highly ordered -oriented epitaxial perovskite (CH3NH3)3Bi2I9.
A. Banik et al., "Epitaxial Electrodeposition of BiI3 and Topotactic Conversion to Highly Ordered Solar Light-Absorbing Perovskite (CH₃NH₃)₃Bi₂I₉," Chemistry of Materials, American Chemical Society (ACS), Sep 2020.
The definitive version is available at https://doi.org/10.1021/acs.chemmater.0c02304
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15 Sep 2020