The effect of gold quantum dots/grating-coupled surface plasmons in inverted organic solar cells

We studied the effect of gold quantum dots (AuQDs)/grating-coupled surface plasmon resonance (GC-SPR) in inverted organic solar cells (OSCs). AuQDs are located within a GC-SPR evanescent field in inverted OSCs, indicating an interaction between GC-SPR and AuQDs' quantum effects, subsequently giving rise to improvement in the performance of inverted OSCs. The fabricated solar cell device comprises an ITO/TiO2/P3HT : PCBM/PEDOT : PSS : AuQD/silver grating structure. The AuQDs were loaded into a hole transport layer (PEDOT : PSS) of the inverted OSCs to increase absorption in the near-ultraviolet (UV) light region and to emit visible light into the neighbouring photoactive layer, thereby achieving light-harvesting improvement of the device. The grating structures were fabricated on P3HT:PCBM layers using a nanoimprinting technique to induce GC-SPR within the inverted OSCs. The AuQDs incorporated within the strongly enhanced GC-SPR evanescent electric field on metallic nanostructures in the inverted OSCs improved the short-circuit current and the efficiency of photovoltaic devices. In comparison with the reference OSC and OSCs with only green AuQDs or only metallic grating, the developed device indicates enhancement of up to 16% power conversion efficiency. This indicates that our light management approach allows for greater light utilization of the OSCs because of the synergistic effect of G-AuQDs and GC-SPR.

1. The authors ascribed the device performance enhancement to "AuQDs acted as effective photosensitizers for absorbing light in the UV region and the photoactive layer harvested the emitted visible light". Why the introduction of gold quantum dots results in the IPCE enhancement in the whole spectrum? 2. The down-conversion efficiency of gold quantum dots is unclear. How many ultraviolet photons absorbed by gold quantum dots can be converted to emitted photons? 3. Why the gold quantum dots boost the hole transporting in PEDOT:PSS rather than trapping the carriers? 4. According to Figure 4, the reflectivity of flat device is below 0.1 around 520 nm, while the G-AuQDs/DVD-R grating-based device has a value around 0.15 that indicating poorer light harvesting. Why the increased reflectivity leads to the increase in IPCE?
Decision letter (RSOS-210022.R0) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below. The editor assigned to your manuscript has now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Subject Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Reviewer: 2
Comments to the Author(s) Kuntamung et al. used gold quantum dots and grating to enhance the light-harvesting of organic solar cells. By incorporating the down-conversion property of gold quantum dots and surface plasmon resonance of gratings, the authors obtained a 16% increase in power conversion efficiency. The obtained simulation results have a certain significance in light manipulation in photovoltaic devices. This article can be considered publishing on Royal Society Open Science after addressing the following questions: 1. The authors ascribed the device performance enhancement to "AuQDs acted as effective photosensitizers for absorbing light in the UV region and the photoactive layer harvested the emitted visible light". Why the introduction of gold quantum dots results in the IPCE enhancement in the whole spectrum? 2. The down-conversion efficiency of gold quantum dots is unclear. How many ultraviolet photons absorbed by gold quantum dots can be converted to emitted photons? 3. Why the gold quantum dots boost the hole transporting in PEDOT:PSS rather than trapping the carriers? 4. According to Figure 4, the reflectivity of flat device is below 0.1 around 520 nm, while the G-AuQDs/DVD-R grating-based device has a value around 0.15 that indicating poorer light harvesting. Why the increased reflectivity leads to the increase in IPCE?
Author's Response to Decision Letter for (RSOS-210022.R0) See Appendix A.

Do you have any ethical concerns with this paper? No
Have you any concerns about statistical analyses in this paper? No

Recommendation?
Accept as is Comments to the Author(s) Interesting work! Hope it can be published successfully!

Review form: Reviewer 2
Is the manuscript scientifically sound in its present form? Yes

Are the interpretations and conclusions justified by the results? Yes
Is the language acceptable? Yes

Comments to the Author(s)
The influences of AuQDs on optical/electrical properties of devices and corresponding mechanisms have been clarified in the revised manuscript. I think the current manuscript is acceptable.

Decision letter (RSOS-210022.R1)
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Thank you for your fine contribution. On behalf of the Editors of Royal Society Open Science and the Royal Society of Chemistry, I look forward to your continued contributions to the Journal. We have revised the manuscript in accordance with the comments and suggestions by reviewers. We have addressed these comments on a point-by-point basis. A revised version is enclosed for review.
We hope the revised version is now acceptable for publication in Royal Society Open Science and we are looking forward to hearing from you in due course. We appreciate the comments of the reviewers and hereby submit a revised and improved manuscript. We have addressed these comments and have incorporated the necessary changes on the manuscript. All the major revisions on the text are shown in RED. In the case of conventional structure, AuQDs cannot be located within the grating-coupled surface plasmon evanescent field [Ref. 31 in a manuscript). Therefore, in this study, we would like to explore the effect of AuQDs which is located in grating-coupled surface plasmon evanescent field using an inverted OSCs. This explanation is included in an introduction part in a manuscript.
2. Again, to verify its universality, it's better to add at least one more material system, whose photovoltaic performance is improved through this synergistic effect of AuQDs and GC-SPR.
Reply: Recently, we have constructed conventional OSCs by an introduction of AuQDs and plasmonic grating structures [Ref 29 and 31 in a manuscript] into the conventional OSCs system. Inthese case, we explored the synergistic effect of AuQDs and gold nanoparticles and also AuQDs and GC-SPR. As mentioned above, in the case of conventional OSCs structure, the AuQDs cannot be located within the strongly enhanced GC-SPR evanescent field. Therefore, we attempt to develop inverted devices using materials and structures mentioned above. As shown in Table 2