Synthesis and Characterization of Chalcogenide Perovskites
Chalcogenide perovskites are both an old and new group of materials. First synthesized in 1957, chalcogenide perovskites are generally sulfur and selenium compounds which contain a 3D network of corner-sharing octahedra. Not until 2015 was this material class recognized as being suitable for any app...
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Massachusetts Institute of Technology
2022
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| Online Access: | https://hdl.handle.net/1721.1/139111 https://orcid.org/0000-0002-6182-8341 |
| Summary: | Chalcogenide perovskites are both an old and new group of materials. First synthesized in 1957, chalcogenide perovskites are generally sulfur and selenium compounds which contain a 3D network of corner-sharing octahedra. Not until 2015 was this material class recognized as being suitable for any application. Their strong light absorption in the visible to near-IR wavelengths makes them of interest as photovoltaic absorber materials. The potential to deliver on the promise of low-cost thin film photovoltaics is reason enough to study chalcogenide perovskites. Additionally, their structural similarity to lead-halide and oxide perovskites offers a new opportunity to study related questions in those fields such as defect tolerance in lead-halide perovskites and ferroelectricity in oxides. The following projects represent advances in both synthesis and characterization of chalcogenide perovskites.
I used computational software to calculate phase diagrams for chalcogenide perovskites. These phase diagrams were calculated in ultra-high vacuum conditions to serve as guides for thin film deposition techniques. I also attempted to synthesis the predicted ferroelectric compound ZnSnS3 by molecular beam epitaxy and solid phase epitaxy. Here I also report on the application of the new “cold sintering process” technique applied to densification of BaZrS3. I explored multiple sintering aides, including organic solvents, sulfur and iodine. I achieved high densification with iodine as a sintering aid.
I characterized the dielectric and electronic properties of BaZrS3 and Ba3Zr2S7 single crystals. I used impedance spectroscopy on single crystals to measure their low-frequency relative dielectric constants. I used pump-probe IR reflectivity to measure mobility anisotropy in Ba3Zr2S7 single crystals. I used a Drude model to estimate the ambipolar carrier mobility from IR reflectivity in the <110> and <001> directions of Ba3Zr2S7.
This body of work advances the emerging field of chalcogenide perovskites by providing practical guides for thin film synthesis, lessons from thin film and bulk synthesis work, as well and basic property measurements on bulk material, critical for the design of future thin film devices. |
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