Defect-Induced Modulation of Electronic and Optical Properties in Monolayer CsPb₂Br₅: Implications for Fiber-Optic Sensing Applications

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents a well-organized and scientifically meaningful study on the effects of intrinsic vacancy defects on the structural, electronic, and optical properties of monolayer CsPb₂Br₅. The methodology is sound, and the comparison between ds and ss configurations adds valuable insight into the dimensional modulation of perovskite optoelectronics. The manuscript is overall clear and technically robust.

Suggestions for improvement:

1.The connection between the theoretical findings and potential fiber-optic sensor applications is interesting but could be elaborated slightly more in the introduction and conclusion. A few sentences on how the defect-induced optical features could be harnessed in practical fiber-integrated devices would strengthen the context.

2.In Figures 7 and 8, it would be helpful to mark the direct/indirect bandgap transitions explicitly (e.g., with arrows or colored lines) to improve visual clarity for readers.

3.In the band structure figures, could the authors label the VBM and CBM positions explicitly for clarity?

Recommendation: Minor Revision

Author Response

Comment 1: The connection between the theoretical findings and potential fiber-optic sensor applications is interesting but could be elaborated slightly more in the introduction and conclusion. A few sentences on how the defect-induced optical features could be harnessed in practical fiber-integrated devices would strengthen the context.

Response 1: Thank you for this insightful suggestion. We have added a more detailed discussion of how the defect-induced optical features can be utilized in fiber-integrated sensing systems in Section 1 (page 3). We believe this supplement enhances the scientific significance and applicability of the work.

 

Comment 2: In Figures 7 and 8, it would be helpful to mark the direct/indirect bandgap transitions explicitly (e.g., with arrows or colored lines) to improve visual clarity for readers.

Response 2: Thank you for this helpful suggestion. In response to this comment, we have clearly marked the direct and indirect bandgap transitions in all relevant figures (Figures 7 and 8), using arrows and color-coded lines to distinguish the valence band maximum (VBM) and conduction band minimum (CBM). These visual enhancements improve the clarity of the band structures and help readers more easily identify the nature of the bandgap in each configuration. We believe these modifications significantly enhance the readability of the graphical content.

 

Comment 3: In the band structure figures, could the authors label the VBM and CBM positions explicitly for clarity?

Response 3: Thank you for this constructive suggestion. In response, we have explicitly labeled the positions of the valence band maximum (VBM) and conduction band minimum (CBM) in all relevant band structure figures. These labels are now clearly marked with arrows and text annotations to enhance visual clarity and ensure that readers can easily identify the key energy levels. We believe these improvements significantly aid in the interpretation of the electronic structure results.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have conducted a comprehensive DFT-based study that highlights how vacancy defects modulate the optoelectronic properties of CsPb₂Br₅ monolayers. The comparative analysis between ds and ss structures is particularly valuable and the work is well-suited for publication.

Suggestions:

1.The Introduction could briefly include recent applications of 2D halide perovskites in photonic or sensor systems to strengthen the context.

2.The authors mention that V_Br2 introduces shallow defect levels—could a brief comparison be made with similar behavior in CsPbBr₃ or MAPbBr₃?

3.For V_Cs and V_Pb, the bandgap increase is mentioned. Would it be possible to briefly comment on how the structural asymmetry or under-coordination of neighboring atoms contributes to this effect?

Author Response

Comment 1: The Introduction could briefly include recent applications of 2D halide perovskites in photonic or sensor systems to strengthen the context.

Response 1: Thank you for your valuable feedback. In response to your suggestion, we have included a brief overview of recent applications of two-dimensional (2D) halide perovskites in photonic and sensor systems within the Introduction section (page 3). This addition aims to provide a stronger context for the significance of our study in these emerging fields. We believe this enhancement enriches the background and sets a clearer stage for our research contributions.

 

Comment 2: The authors mention that V_Br2 introduces shallow defect levels—could a brief comparison be made with similar behavior in CsPbBr₃ or MAPbBr₃?

Response 2: Thank you for this insightful suggestion. We agree that comparing the defect behavior of V_Br2 in CsPb₂Br₅ with that in well-studied 3D perovskites such as CsPbBr₃ and MAPbBr₃ can provide valuable context for understanding defect tolerance across different perovskite families. In response, we have added a brief comparison in the revised manuscript (Section 3, page 14). We believe this addition strengthens the connection between our findings and the wider perovskite research field.

 

Comment 3: For V_Cs and V_Pb, the bandgap increase is mentioned. Would it be possible to briefly comment on how the structural asymmetry or under-coordination of neighboring atoms contributes to this effect?

Response 3: As suggested, we have added a discussion on how structural asymmetry and under-coordination of neighboring atoms contribute to the band gap increase for V_Cs and V_Pb defects in the revised manuscript (Section 3, page 12).

Reviewer 3 Report

Comments and Suggestions for Authors

The paper entitled 'Defect-Induced Modulation of Electronic and Optical Properties in Monolayer CsPb2Br5: Implications for Fiber-Optic Sensing Applications' is interesting and suitable for publication in a photonics journal after minor revisions.

1. In the paper, VBr and VBr2 represent two types of single Br monovacancy defects, respectively. However, the notation VBr2 is easily misinterpreted as a double Br vacancy defect. Please reconsider their notation.

 

2. It is recommended to include descriptions of necessary computational parameters, such as model size and energy convergence criteria, in the Computational Methods section.

 

3. Regarding the notation for ds-CsPb₂Br₅ and ss-CsPb₂Br₅ in the paper, please unify the usage of the prefixes "ds-" and "ss-".

 

4. Concerning Figure 7d, the authors state that introducing a Pb vacancy still preserves the original indirect bandgap characteristic, which represents a distinct difference compared to other vacancies. Please provide possible explanations for this phenomenon.

Author Response

Comment 1: In the paper, V_Br and V_Br2 represent two types of single Br monovacancy defects, respectively. However, the notation V_Br2 is easily misinterpreted as a double Br vacancy defect. Please reconsider their notation.

Response 1: Thank you for this important suggestion. We agree that the original notation (V_Br and V_Br2) could be misinterpreted, particularly with V_Br2 being potentially confused with a double Br vacancy. To address this concern, we have revised the defect notation in the manuscript: V_Br and V_Br2 are now referred to as V_Br-c and V_Br-b, respectively. The updated notation is consistently applied throughout the text, figures, and table captions. We believe this clarification improves the readability and accuracy of our presentation.

 

Comment 2: It is recommended to include descriptions of necessary computational parameters, such as model size and energy convergence criteria, in the Computational Methods section.

Response 2: Thank you for this constructive suggestion. We agree that providing clear computational details is essential for reproducibility and clarity. As requested, we have enhanced the Computational Methods section in the revised manuscript. We have now explicitly added the supercell size and lattice parameters used in our simulations to provide a more complete description of the computational setup. These additions ensure that the structural models and computational accuracy can be fully assessed by readers.

 

Comment 3: Regarding the notation for ds-CsPb₂Br₅ and ss-CsPb₂Br₅ in the paper, please unify the usage of the prefixes "ds-" and "ss-".

Response 3: Thank you for this suggestion. We agree that consistent notation is important for clarity. In response, we have carefully reviewed the manuscript and unified the usage of the prefixes "ds-" and "ss-" throughout the text, figures, and table captions. This revision ensures a clear and coherent presentation of the two structural models.

 

Comment 4: Concerning Figure 7d, the authors state that introducing a Pb vacancy still preserves the original indirect bandgap characteristic, which represents a distinct difference compared to other vacancies. Please provide possible explanations for this phenomenon.

Response 4: Thank you for this insightful comment. We agree that the preservation of the indirect bandgap character upon introducing a Pb vacancy (as shown in Figure 7d) is an interesting and distinct behavior compared to other vacancy types. In response, we have added a brief explanation in the revised manuscript (Section 3, page 12). We believe these additions provide a clearer understanding of the unique impact of V_Pb on the electronic structure.