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Chalcogenide perovskites have recently attracted significant attention for renewable energy applications due to their predicted combination of air, moisture, and thermal stability, which has been experimentally validated, along with their excellent optoelectronic properties, which are still under experimental investigation. While historically requiring high synthesis temperatures, some solution-processed routes have recently emerged for synthesizing chalcogenide perovskites, such as BaZrS3 and BaHfS3, at temperatures below 600 °C. This study discusses several experimental challenges associated with the moderate-temperature synthesis of solution-deposited chalcogenide perovskites. Firstly, we identify Ruddlesden–Popper (RP) phases as thermodynamically stable competing secondary phases in perovskite synthesis. High sulfur pressures favor the formation of BaZrS3 or BaHfS3, whereas lower sulfur pressures result in a mixture of perovskite and RP phases. Additionally, we briefly discuss the mechanism of moderate-temperature synthesis of chalcogenide perovskites, including some of the morphological and optoelectronic challenges it presents, such as grain overgrowth, secondary phase contamination entrapment, and the presence of mid-band gap emissions. Finally, we address the importance of substrate selection and the potential presence of Ca- and Na-based impurities originating from cation out-diffusion from glass substrates. Addressing these challenges will be crucial as these unique materials continue to be investigated for applications in optoelectronic devices.
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A Low-temperature Growth Mechanism for Chalcogenide Perovskites
Chalcogenide perovskites have attracted increasing research attention in recent years due to their promise of unique optoelectronic properties combined with stability. However, the synthesis and processing of these materials has been constrained by the need for high temperatures and/or long reaction times. In this work, we address the open question of a low-temperature growth mechanism for BaZrS3. Ultimately, a liquid-assisted growth mechanism for BaZrS3 using molten BaS3 as a flux is demonstrated at temperatures ≥540 °C in as little as 5 min. The role of Zr-precursor reactivity and S(g.) on the growth mechanism and the formation of Ba3Zr2S7 is discussed, in addition to the purification of resulting products using a straightforward H2O wash. The extension of this growth mechanism to other Ba-based chalcogenides is shown, including BaHfS3, BaNbS3, and BaTiS3. In addition, an alternative vapor-transport growth mechanism is presented using S2Cl2 for the growth of BaZrS3 at temperatures as low as 500 °C in at least 3 h. These results demonstrate the feasibility of scalable processing for the formation of chalcogenide perovskite thin-films. (DOI: 10.1021/acs.chemmater.3c00494)
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- PAR ID:
- 10420169
- Date Published:
- Journal Name:
- Chemistry of materials
- ISSN:
- 1520-5002
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.chemmater.3c00494
