OLEDs on Down-Converting Fabric by Using a High Scalable Planarization Process and a Transparent Polymeric Electrode

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In this paper, the author proposed a planarization process designed for textile-based electronic devices. This technique involves depositing a liquid resin at the textile interface and a "guide substrate" through a blade coating method. Subsequently, the deposited resin undergoes cross-linking via UV radiation, resulting in the formation of a solid polymeric layer on the fabric's surface. This method facilitates the creation of a uniform and level surface on the textile, enhancing the overall stability and performance of electronic components integrated into the fabric. The present work is generally well-described and written. I recommend improving the article with minor revisions before it is accepted for publication. My comments are the following;

1.     Please include a comparison of the survey to those previously reported in the form of a table for better clarity.

2.     The conclusion must present some drawbacks of this study, future work scope, and quantitative research findings.

3.     The author should work on the introduction and explain why this work provides new knowledge or innovation to the field. Overall, it is quite simple and not clear.

 

4.     Lack of pictures to support the experiment. Include clear schematic diagrams of the measurement setup, especially OLED fabrication. Provide a more detailed explanation of the test system.

Comments on the Quality of English Language

NA

Author Response

Thank you very much for taking the time to review our manuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

 

Reviewer's comments: 

In this paper, the author proposed a planarization process designed for textile-based electronic devices. This technique involves depositing a liquid resin at the textile interface and a "guide substrate" through a blade coating method. Subsequently, the deposited resin undergoes cross-linking via UV radiation, resulting in the formation of a solid polymeric layer on the fabric's surface. This method facilitates the creation of a uniform and level surface on the textile, enhancing the overall stability and performance of electronic components integrated into the fabric. The present work is generally well-described and written. I recommend improving the article with minor revisions before it is accepted for publication. My comments are the following.

 

1. Please include a comparison of the survey to those previously reported in the form of a table for better clarity.

We have added a comparative table (Table 1) in the revised version of the manuscript by highlighting the planarization method used, the device architecture, the related deposition techniques and finally the device performance. As can be seen, although planarization methods based on UV-curing resins and using guide substrates to improve the properties of the planarized fabric have been used in the past, this is the first time that an easily industrially scalable deposition method such as the blade coating has been used.

Moreover, most of the previously reported fabric-based OLEDs have a top emitting architecture and only a recent work shows a transparent OLED with stable operation for 1000 bending cycles. In our work, we obtained a fabric-based transparent OLED by using a polymeric anode with a stable operation for 1000 cycles at a bending radius of 5 mm.

We believe that the combination of industrially scalable planarization method and the new transparent device architecture represent a new achievement in the field of fabric-based OLEDs.

 

2. The conclusion must present some drawbacks of this study, future work scope, and quantitative research findings.

 We have updated the conclusions by highlighting some critical aspects of our planarization method that we will investigate further in future work. In particular, we have added the following paragraph: “On the other hand, the proposed planarization method, although capable of transferring a good surface morphology to the planarization film, presents a limiting issue related to the generalization of the technique on any type of fabric. In fact, if the weft and warp of the fabric are too dense (reduced presence of voids), during the curing phase a large part of the UV radiation would be absorbed by the fabric itself and the polymerization of the resin might not take place completely. To overcome this issue, a transparent substrate (i.e. glass) could be used as a guide substrate instead of silicon, although a solution would have to be found to minimize the surface roughness of glass, which is known to be higher than that of silicon wafers. The improvement and generalization of the planarization technique proposed here will be investigated in future work, with the aim of developing a process that is not limited by the type of woven fabric used.”

 

3. The author should work on the introduction and explain why this work provides new knowledge or innovation to the field. Overall, it is quite simple and not clear.

 We thank the reviewer for the suggestion. We modified the introduction in order to give a more specific vision of innovative aspects of the present work. In particular, the comparative table added to the manuscript is really useful to highlight the advantages of our approach. We added the following paragraphs to the revised manuscript:

“Table 1 summarizes all the planarization methods mentioned, together with the device architecture, deposition techniques and performance. As can be seen from such a table, most of the planarization methods are not fully industrially scalable because they involve multi-step processes and/or laboratory scale deposition (e.g. spin coating).”

“In addition, the fabricated OLEDs are fully transparent, since they exploit a PEDOT:PSS anode and an Ag/WO₃ transparent bilayer as cathode. Fabric-based transparent devices can be particularly interesting from an aesthetic point of view and in our case, we combined them with fluorescent fabrics to down-convert the colour emitted by the device. Such an approach could be very useful to achieve white emission from a very simple structure.

Therefore, considering all these features, the advantages/innovations of our fabric-based OLEDs are the following:

-     industrial scalable planarization method based on blade-coating deposition;

-     fully transparent OLEDs that exploit a polymeric anode;

-     down-converting approach to easily tune the colour emitted by the device.”

 

4. Lack of pictures to support the experiment. Include clear schematic diagrams of the measurement setup, especially OLED fabrication. Provide a more detailed explanation of the test system.

 Thanks for the advice, we have added new diagrams and pictures to better clarify the manufacturing and characterisation process, and included more details about the test system in the Experimental section. In particular:

• We replaced Figure 1 with an updated version, in order to make the planarization process clearer;
• We have added a block diagram in Figure 4 to better clarify the fabrication and characterization processes, also including schematic representation of the involved sub-processes (O₂ plasma, anode spin-coating, thermal evaporation of organic stack and cathode, electro-optical characterization using a calibrated CCD);
• We have added a sketch in Figure 6 to show the method we used for the bending test;
• We include more detailed info about the bending test.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors report a blad-coated planarization method for the fabrication of OLED on polyester fabrics. A UV-curable liquid resin is used as a planarization layer.  The device shows high luminance (>1000 cd/m2) and current efficiency values, even after 1000 bending cycles. Thus, I would suggest publication after revision.

1. all the figure resolutions should be increased for a clearer view.

2. how about the device stability after long-term storage?

3. how is RMS roughness obtained by the AFM test, which is needed?

Comments on the Quality of English Language

The English needs to be polished again.

Author Response

We thank the referee for taking the time to review ourmanuscript. Please find the detailed responses below and the corresponding revisions highlighted in the re-submitted files.

 

Reviewer's comments

 The authors report a blad-coated planarization method for the fabrication of OLED on polyester fabrics. A UV-curable liquid resin is used as a planarization layer. The device shows high luminance (>1000 cd/m2) and current efficiency values, even after 1000 bending cycles. Thus, I would suggest publication after revision.

 

1. All the figure resolutions should be increased for a clearer view.

 Thanks for the advice, we have updated all the figures, increasing their resolution and clarity. We also checked and fixed the format of some plots, which were different from the others.

  

2. How about the device stability after long-term storage?

 We thank the reviewer for raising this issue, but we believe that it is not strictly related to our work. The manuscript describes the planarization process of the fabric and the subsequent fabrication of an OLED device on its top to test the quality of the innovative flexible substrate. In particular, the flexibility of the planarized fabric and the mechanical stability of the device was tested by monitoring its performance after several bending cycles, which is a fundamental aspect with respect to devices on fabric. As for the long-term stability in standard conditions (without mechanical deformation) after long-term storage, this is not influenced by the type of substrate, but by the architecture and materials used, as well as the encapsulation process, which is not mentioned in this case. We therefore believe that this question can be left to future research.

  

3. How is RMS roughness obtained by the AFM test, which is needed?

 With regard to the surface properties of the planarized fabrics, we have included two figures in the supporting information showing the profilometer scans of the fabric before and after the planarization process and the AFM images of the two fabrics with the best planarization method (NOA 65/NOA 61).

The profilometer scans of the pristine fabrics (Figures S1a and S1c) show the textile structure visible in the SEM images, with a height difference between the valleys and peaks of about 80 µm.

Looking at the profilometer scans of the planarized fabrics, all resins are able to strongly reduce the above mentioned height difference in the range of hundreds/thousands of nm. In particular, fabrics planarized with NOA 61 and NOA 65 show a significant wavy structure and defects due to fibres not completely covered by the resin. Fabrics planarized with NOA 68 and NOA 65/NOA 61 are almost comparable, with a smooth wavy structure and absence of defects and such characterisation confirms the suitability of such planarized fabrics for the fabrication of OLED devices.

As a further confirmation, Figure S2 shows the AFM images of the two different fabrics planarized with NOA 65/NOA 61 and as can be seen, the roughness is very low.

We added the following paragraph to the revised manuscript:

“The profilometer scans of the planarized fabrics (Figure S1b and S1d) confirm what was deduced from the SEM images. Indeed, all resins are able to strongly reduce the valleys-peaks height typical of the fabrics in the range of hundreds/thousands of nm. In particular, fabrics planarized with NOA 61 and NOA 65 show a significant wavy structure and defects due to fibres not completely covered by the resin. Fabrics planarized with NOA 68 and NOA 65/NOA 61 are almost comparable, with a smooth wavy structure and absence of defects and such characterisation confirms the suitability of such planarized fabrics for the fabrication of OLED devices. The AFM pictures and associated roughness values shown in Figure S2 further confirm the possibility of fabricating OLED devices on such planarized fabrics.”

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I am satisfied with the answers and additional explanations of authors in the revised version of this manuscript and I suggest to be accepted.

Comments on the Quality of English Language

NA

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed my concerns, it can be accepted now.