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Anionic order and band gap engineering in vacancy ordered triple perovskites.
Taylor L Hodgkins1, Christopher N Savory, Kelsey K Bass
1Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA. melot@usc.edu.
Chemical Communications (Cambridge, England)
|February 26, 2019
Summary
We tuned the optical absorption of cesium bismuth bromide (Cs3Bi2Br9) perovskites by replacing bromine with iodine. This substitution shifts the absorption spectrum and helps determine the lowest possible band gap for these materials.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Optical Materials
Background:
- Vacancy-ordered triple perovskites, such as Cs3Bi2Br9, are promising optoelectronic materials.
- Tuning the optical properties of these perovskites is crucial for their application in devices.
- Understanding structure-property relationships is key to designing new materials.
Purpose of the Study:
- To investigate the effect of iodine substitution for bromine in Cs3Bi2Br9 on its optical absorption.
- To maintain the layered structural topology during halide substitution.
- To determine the preferred site occupancy of halide ions and its impact on lattice strain.
Main Methods:
- Synthesis of mixed halide perovskites (Cs3Bi2(Br,I)9).
- Characterization of structural topology using X-ray diffraction.
- Optical absorption spectroscopy to determine band gap and absorption edge shifts.
- Analysis of halide site preference and lattice strain.
Main Results:
- Significant red-shift in optical absorption observed with increasing iodine content.
- Layered structural topology is maintained throughout the substitution.
- Bromine ions preferentially occupy bridging halide positions to minimize lattice strain.
- Quantified the upper limit of iodine incorporation in the layered polymorph.
Conclusions:
- Halide substitution is an effective strategy to tune the optical absorption of Cs3Bi2Br9.
- The observed Br/I site preference provides insights into lattice stability.
- Established the minimum achievable band gap for these Bi-based layered perovskites.
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