Energy-Level Interpretation of Carbazole Derivatives in Self-Assembling Monolayer

Round 1

Reviewer 1 Report

1.     The introduction of the paper contains many small paragraphs, and it is recommended to categorize and integrate them.

2.     The measured work function in the paper differs from the results cited in the references (Adv Energy Mater 2022, 12, doi:10.1002/aenm.202202503). Please explain the reasons.

3.     The authors cited literature that has already characterized the work function and energy levels of all the materials used in this paper, as well as conducted simulation calculations. Additionally, they have demonstrated that the self-assembled materials can act as hole transport layers. Therefore, the novelty of this paper is relatively low.

4.     PES method can be used as a highly effective tool for investigating both organic materials and the ITO/SAM interface need more evidences.

Author Response

We sincerely appreciate the reviewer for providing valuable comments and suggestions.

1. The introduction of the paper contains many small paragraphs, and it is recommended to categorize and integrate them.

The revisions have been implemented in the Introduction section.

2. The measured work function in the paper differs from the results cited in the references (Adv Energy Mater 2022, 12, doi:10.1002/aenm.202202503). Please explain the reasons.

The authors of the paper mentioned that the energy levels were measured using UPS and KPS methods. However, it is unclear from the paper which specific energy levels are being referenced. In our study, it is crucial to distinguish between the energy level of modified ITO and the ionization energy of the molecule. Therefore, we were unable to utilize the energy levels provided in the paper titled "Adv Energy Mater 2022, 12, doi:10.1002/aenm.202202503."

3. The authors cited literature that has already characterized the work function and energy levels of all the materials used in this paper, as well as conducted simulation calculations. Additionally, they have demonstrated that the self-assembled materials can act as hole transport layers. Therefore, the novelty of this paper is relatively low.

The cited papers present these SAM as hole transport layer and at the same time talk about the modification of ITO work function with the simulations related to the modification of the ITO work function. Basically, the authors mixed ionisation energy of molecule with the modification of ITO work function. In our paper we separated these two energies (the modified ITO work function and ionisation energy of molecule) and analysing each energy influence on the performance of solar cells. To our best knowledge no one has done it till now.

The novelty of the paper is:

1) The energy levels of self-assembled monolayer (SAM) layers can be accurately measured using the spectral dependence of photoelectron emission.

2) The spectral dependence of photoelectron emission can be described as a combination of two signals. One signal is related to changes in the work function of the electrode, while the other signal is associated with the ionization energy of SAM molecules.

3) The impact of SAM molecules' ionization energy on device performance is greater than the modification of the electrodes work function by the SAM. Consequently, SAM molecules that possess an active moiety in the spacer can be more effectively characterized as hole transport materials.

4. PES method can be used as a highly effective tool for investigating both organic materials and the ITO/SAM interface need more evidences.

There are several papers that show that PES can be used for determination of ionisation energy of the organic materials and possible organic material interaction with metal or organic material.

Few of the papers:

doi:10.1016/j.orgel.2011.11.024

doi:10.7567/APEX.6.025801

doi:10.1016/j.jpcs.2016.03.010

doi:10.1117/12.2227823

Reviewer 2 Report

The manuscript offers valuable insights into the correlation between the work function of surface monolayers/thin films and the ionization energy of surface molecules. The scientific content of the study is commendable; however, there are areas that necessitate improvement, as outlined below:

1. There's repeating using of abbreviations: SAM is referred to different terms in line 46-47 "self-assembling monolayer (SAM)" and line 54 "Surface-anchored monolayer (SAM)". 

2. Abbreviation "indium tin oxide (ITO)" was declared on line 170. It should be declared at its first appearance at line 107. 

3. Caption of Figure1: it's hard to distinguish circle/square/triangles. Better label the compounds with colors. 

4. Line 228, unit of surface resistivity ohms/sq is not correctly rendered. 

5. How is the thickness of the monolayer being determined? Is the same measurement (dektak150) as used for the thin film being applied?

6. Absolute value of HOMO energy from ab initio calculations has no physical meaning. As it doesn't involve the discussion, it should not be reported in the Table 1.

It's suggested to get the logic flow smoothed e.g. line 40-42 "Modifying the molecule ..." should declare the relationship of "the molecule" to the "materials" in the previous contents. Fine tuning of language and paragraph is strongly recommended.

Author Response

Thank you to the reviewer for providing valuable feedback and suggestions for improving the manuscript.

The manuscript offers valuable insights into the correlation between the work function of surface monolayers/thin films and the ionization energy of surface molecules. The scientific content of the study is commendable; however, there are areas that necessitate improvement, as outlined below:

1. There's repeating using of abbreviations: SAM is referred to different terms in line 46-47 "self-assembling monolayer (SAM)" and line 54 "Surface-anchored monolayer (SAM)". 

We have corrected the disagreement of the terms in manuscript.

2. Abbreviation "indium tin oxide (ITO)" was declared on line 170. It should be declared at its first appearance at line 107. 

Abbreviation ITO is now declared at line 107.

3. Caption of Figure1: it's hard to distinguish circle/square/triangles. Better label the compounds with colors. 

The colors of the curves for the different compounds were added in the caption.

4. Line 228, unit of surface resistivity ohms/sq is not correctly rendered. 

Surface resistivity units was corrected.

5. How is the thickness of the monolayer being determined? Is the same measurement (dektak150) as used for the thin film being applied?

The SAM layer thickness was taken from the literature.

Reference:

29. Magomedov, A.; Al-Ashouri, A.; Kasparavičius, E.; Strazdaite, S.; Niaura, G.; Jošt, M.; Malinauskas, T.; Albrecht, S.; Getautis, V. Self-Assembled Hole Transporting Monolayer for Highly Efficient Perovskite Solar Cells. Adv Energy Mater 2018, 8, 1801892, doi:10.1002/aenm.201801892.

6. Absolute value of HOMO energy from ab initio calculations has no physical meaning. As it doesn't involve the discussion, it should not be reported in the Table 1.

The correlation between HOMO energy level and ionization energy from PES is emphasized that proves the measured electron origin form highest occupied molecular orbital.

It's suggested to get the logic flow smoothed e.g. line 40-42 "Modifying the molecule ..." should declare the relationship of "the molecule" to the "materials" in the previous contents. Fine tuning of language and paragraph is strongly recommended.

Better clarification was done by changing “material” to “compound” and explained that modification is done to the structure of molecule. The changes were added to manuscript. Paragraph was restructured and language rechecked.

Round 2

Reviewer 1 Report

The author has answered all my questions, so the paper can be accepted.

Author Response

Thank you for accepting the manuscript. We have made some language and style corrections based on the recommendations of the other reviewer.

Reviewer 2 Report

The revision to the results and description is acceptable.

The logic flow still needs minor improvement.

For example, in the revised manuscript line 40 it reads "Both factors are dependent on the chosen compound..."

It's necessary to declare "the compound" before this sentence, otherwise how does the reader know what does this "compound" refers to?

Author Response

Thank you, reviewer, for your additional suggestions regarding the language used in the document. The manuscript has been reviewed by an individual who had not previously read it. We hope that the changes made by this person will enhance the clarity of the manuscript.