Comments on abstract, title, references

Abstract: The objective of the present paper is to develop CZTSSe solar cells on the flexible substrate and its scale up on the large areas.

Title: Title is informative and relevant.

References: References are up to date and adequate.

Comments on introduction/background

Introduction: The given paper clearly presents the background and need for the study. Research objectives are clear and sound and appropriately justified.

Comments on methodology

The process of sample selection is clear. The variables are well defined. Though statistics not provided in the manuscript, measurement seems reliable. Various processes for the reproduction of results are adequate.

Comments on data and results

The present work investigates different precursor stack conditions on device performance and its scalability of CZTSSe solar cells developed on flexible substrates. The investigation provides ample data in the form of Figures & Tables describing results obtained via substantial & sufficient characterization. The present work reports the highest efficiency for CZTSSe solar cells on large-area flexible substrates which is significant progress in the field of thin-film photovoltaics. Results confirmed to be reliable, supported by ample statistics provided.

Comments on discussion and conclusions

The conclusion of the study that the multilayer precursor strategy yields better device performance over a large area is in good agreement with objectives and is well supported by experimental investigations & characterizations. As preliminary work, I believe this work has good prospects for the industrial commercialization of CZTSSe solar cells.

Recommendations for further improvements

1. The authors successfully demonstrated the scaleup of CZTSSe solar cells from a small area (0.55 cm2) to large area devices (2.25 cm2). But given fact, most successful commercial thin-film PV technologies (such a CdTe) employ monolithic integration for module development. Authors should briefly discuss pathways (benefits & hurdles) for present work to achieve monolithic integration capability.
2. The readers would be happy if the authors discuss the variation of device performances with different bending cycles. The mechanical properties of polycrystalline thin films of CZTSSee are still not known clearly. It would be interesting to see the impact (either improves/degrades) of bending cycle induced strains on polycrystalline CZTSSe device performance.