A Facile Aqueous Solution Route for the Growth of Chalcogenide Perovskite BaZrS3 Films
, Wanyi Nie 3, Aiping Chen 3, Hao Zeng 2 and Quanxi Jia 1,*Round 1
Reviewer 1 Report
The manuscript presents a new facile method for synthesizing BaZrS3 perovskite films and investigates the resistivity-temperature relations in their sample. However, there are several areas that can be further improved to enhance the overall quality of the manuscript. Therefore, I recommend major revisions addressing the following comments:
1. The research focuses on developing an easier synthesis method for BaZrS3, and thus, a thorough characterization of the sample is required to prove that it is indeed BaZrS3 and to compare it with samples made using traditional methods. To achieve this, please consider including:
a. SEM images to visualize the surface morphology and measure grain sizes of the sample, which can impact the material's performance.
b. TEM and/or EDX analysis to obtain a more comprehensive characterization of the material structure, which can provide more convincing evidence than only presenting XRD
c. Absorbance spectrum, which can be in the SI.
d. Tauc plot to quantify the bandgap of the material in a more rigorous manner.
2. As the paper introduces a novel synthesis method, a schematic diagram illustrating the synthetic process is needed to help readers understand the procedure.
3. A better explanation of why this PAD method is helpful is required to improve the soundness of this research. Please consider creating a graph showing the role of the polymer in the formation process of BaZrS3 perovskites and provide more details about the mechanism or relevant citations on the PAD method.
4. Stability is crucial for perovskite materials, and it is one of the advantages of BaZrS3 over other perovskite materials. As synthesis methods may impact stability, it is essential to evaluate it and compare it to samples made by vapor deposition or PLD. Please consider conducting stability tests and presenting the results in the manuscript.
5. Defects are another critical factor affecting the performance of perovskite materials. It would be interesting to investigate the effects of different deposition methods on defects to attract more interest in this study.
6. Besides conductivity, there are other parameters such as carrier lifetime, mobility, and diffusion length that can be used to evaluate the performance of perovskite materials. Please consider analyzing some of these parameters to improve the significance of this study.
7. In line 94, the manuscript mentions the use of ICP analysis. Please describe the instrument used to perform the ICP analysis in the experimental methods section and present the results in the SI.
8. Please clarify whether the beam of LED was focused on the sample and provide information on the beam size used in the study.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors reported a very interesting work about the growth of a sulfide BZS perovskite thin film using an aqueous polymer assisted deposition process. This paper is well-written, and the work is very organized. The perovskite solar cell is a very hot area nowadays. The novelty of this work is also high. However, there are still some flaws in the paper. Therefore, a revision must be made before I can reconsider it for publication.
1. The PDF card ICDD 00-015-0327 should be added in Figure 1a to compare with the experiment data.
2. I strongly suggest the authors draw a materials synthesis scheme in the main text to help the reader understand the process
3. Is that possible to perform the XPS to see the elements and the binding of the material?
4. More introduction about the perovskite-type materials should be added to give the readers a bigger picture. Those include but not limited to briefly introduce what are perovskite, the advantages, and applications (photocatalysis, solar cell etc.). The following paper about perovskite applications must be cited( https://doi.org/10.1021/acsmacrolett.0c00232; https://doi.org/10.1002/ange.202208241; https://doi.org/10.1021/acsmaterialslett.1c00785).
5. Some sentences need references, for example, “Moreover, synthesis of the chalcogenide perovskites such as BZS often involves the use of H2S, a toxic, flammable, and corrosive gas.”
Author Response
We are grateful to the reviewer for the very positive review and for giving us the opportunity to improve our manuscript.
1) The reviewer has a good point. We have added ICSD Card no. 01-073-0847 as a stick pattern, together with the x-ray diffraction pattern of the BZS film.
2) We thank the reviewer’s suggestion. In the revised manuscript, we have added Figs. 1(b) and (c) to show the material synthesis scheme.
3) We would love to carry out XPS measurements to see the elements and binding energy. Unfortunately, we are having limited access to the machine at this moment. It is our goal to fully characterize the materials for our ongoing study of epitaxial BZS films.
4) We thank the reviewer’s suggestion. In the revised manuscript, we have added an introduction about the perovskite-type materials (see the following) and cited more references [1-12] related to perovskites, including the references [11-13] the reviewer has suggested.
“Perovskite is a compositionally diverse class of materials with a prototypical formula of ABX3, where A and B are positively charged cations and X is a negatively charged ion. The crystal structure of perovskites consists of corner-sharing [BX6] octahedra, where the A cation sits in the cubo-octahedral void between the octahedra. Oxide and halide perovskites have been extensively studied for their multifunctional properties such as ferroelectricity, ferromagnetism, superconductivity, ionic conductivity, catalytic activity, and semiconductive as well as optoelectronic properties 1-12. The ideal structure of a perovskite ABX3 is cubic, where the geometry and symmetry of the crystal structure are affected by the relative size of the comprising ions.”
5) We thank the reviewer for the suggestions. Three references [19, 35, 36] have been added right after the statement in the revised manuscript. We have also added more references as needed in other places.
Reviewer 3 Report
The authors developed a liquid-phase precursor-based synthesis method for BZS perovskite films, and performed basic material characterizations to the resultant samples. Although the novel growth method showed promising future applications in devices, we think more experiments and results deserve to be conducted and collected in this work before being considered for publication.
1. It is suggested that the authors include the schematic of the crystal structure as well as any optical microscopy images of the samples in Figure 1.
2. It is suggested that the authors conduct electron diffraction or similar characterizations to confirm the single crystallinity of their samples.
3. Are there any special reasons for using RBS as the tool to detect the chemical composition? In our knowledge it is not a quite common technique for similar purposes. Instead, the authors are suggested to consider methods such as EDS, ToF-SIMS, et al.
4. In Figure 2(b), it seems that there are at least two emission peaks in the PL spectrum. Can the authors perform peak fitting to the spectrum and identify the individual emission peaks?
Author Response
We are grateful to the reviewer for the positive review and for giving us the opportunity to improve our manuscript.
1) We appreciate the reviewer’s suggestion, and have added the schematic of the crystal structure (Fig. 1a) in the versed manuscript. We have added an SEM image of the film in the Supplementary Information.
2) We thank the reviewer for raising this question. We should make our statements clear and concise. To avoid confusion, we added ‘polycrystalline’ right after ‘single-phase’ in the revised manuscript. In other words, the films synthesized are single-phase and polycrystalline. The growth of epitaxial single crystalline BaZrS3 films is not possible on c-plane sapphire due to a lack of appropriate lattice matching. Two groups have recently demonstrated epitaxial growth of BZS films on lattice (001) LaAlO3 substrates by MBE and PLD techniques. Our effort is underway to grow epitaxial BZS films on a lattice-matched substrate by PAD.
3) We thank the reviewer to ask this question. There is no specific reason to use RBS to evaluate the chemical composition of the films. RBS has been widely used to determine the chemical compositions of a range of complex metal oxide films. RBS is more accurate than EDS while also allowing for the estimation of thickness. Currently, we don’t have the access to ToF-SIMS capability. To satisfy the reviewer’s suggestion, we have conducted EDS measurement and added EDS results in Supplementary Information. The Atomic ratio of Ba:Zr:S was found to be 1.00:1.09:3.05, quite similar to the results from RBS analysis.
4) We thank the reviewer for raising this question. We have indeed tried to identify the weak peaks from the PL spectrum. Given the sharp spike nature of the peaks, we are reluctant to assign these peaks to certain impurity phases. We hope the reviewer agrees with us.
Round 2
Reviewer 1 Report
I have reviewed the author's response to my initial review report and I am satisfied with the revisions that have been made. The authors have done an excellent job addressing the concerns raised and have provided clear and comprehensive responses to all of the points raised. I appreciate their attention to detail and their efforts in improving the manuscript.
Reviewer 2 Report
The revised version is very good and it is ready to publish
Reviewer 3 Report
We do not have further comments and would like to recommend that this manuscript be accepted.
