Photoresist-guided indirect photopatterning of quantum dots via carbene-mediated ligand thermocrosslinking

Domain: chemistry
Published: 2026-03-19
Editorial outcome: major_revision

Abstract
Colloidal quantum dots (QDs) are leading candidates for next-generation optoelectronics owing to their tuneable bandgaps, narrow emission linewidths, and high luminescence quantum yields. For virtual-, augmented-, and mixed-reality display applications of these materials, patterning full-color QDs at μm-length scales is essential. However, existing photolithographic approaches often degrade QD luminance characteristics by exposing them to harsh processing conditions, or they compromise the structural fidelity of the resulting patterns. Here we report a photoresist-guided indirect (PIN) photopatterning strategy that includes (i) lithographic formation of sacrificial PR patterns, (ii) deposition of a crosslinked QD film on top, and (iii) PR stripping that removes the sacrificial PR, leaving behind crosslinked QD patterns on the substrate. QD crosslinking is mediated by a diazo-based ligand thermocrosslinker, Diazo-4-LiXer. Leveraging low-temperature (110–120 °C)-activated carbene chemistry, Diazo-4-LiXer bridges neighbouring QDs while maintaining their intrinsic photoluminescence and electroluminescence through repeated processing. Moreover, Diazo-4-LiXer enables thermocrosslinking without affecting the underlying photoresist pre-patterns, which serve as structural templates determining the thickness and fidelity of the QD patterns. Using PIN photopatterning, we realize high-fidelity RGB patterns exceeding 4,000 pixels per inch resolution and demonstrate integration-level scalability by fabricating a 10 × 10 passive-matrix full-colour RGB QD–LED array.

Introduction
Displays present digital images, acting as interfaces between human eyes and electronic signals. While conventional displays such as television, monitors, tablets, and smartphones dominate the market, there is a rapidly growing demand for head-mounted displays (HMDs) for powering virtual-reality (VR), augmented-reality (AR), and mixed-reality (MR) experiences. Given the short distance between HMDs and human eyes, the size of these displays is typically limited to a few inches in diagonal (Fig. 1a)1, 2. This limited screen size introduces a challenge called the screen-door effect because subpixel boundaries become noticeable and affect visual quality3. To avoid the screen-door effect, it is essential to fabricate HMDs with ultra-high pixel densities exceeding 3000 pixels per inch (PPI), where subpixels are separated by only a few micrometers4. Achieving such high pixel densities is pivotal not only for eliminating the screen-door effect but also for reducing motion sickness or nausea that is often associated with immersive VR, AR, and MR experiences. Overall, there exists a significant demand for patterning technology to form high-resolution, high-fidelity red/green/blue (RGB) pixels.

Among emissive materials for displays, colloidal quantum dots (QDs) have been researched extensively in recent years owing to their potential for use in optoelectronic devices5-12. These materials exhibit intriguing physical characteristics, including tunable bandgap, narrow bandwidth, high luminous efficiency, and solution processability13-17. However, the development of a suitable patterning process for these solution-processed nanomaterials remains challenging. Photolithography has emerged as one of the most promising techniques among the various patterning methods available to date18-23, especially because photolithography is already a fully established method for producing high-resolution patterns that fulfil industrial requirements15, 24. In conventional photolithography, patterns are formed by physically or chemically etching the target materials along the features of the overlaid photoresist (PR) pre-patterns25-28. In this process, the target materials must withstand harsh etching conditions while preserving their physical properties. However, the luminescence characteristics of nanostructured light-emitting materials such as QDs are likely to degrade during etching owing to the defects generated over their large surface areas. Recently, direct photopatterning has been exploited as a promising lithographic approach for forming patterns through selective chemical conversion of the target layer, followed by an appropriate developing step24, 29-43. This approach excludes the etching step. However, the high-energy irradiation required for chemical conversion in direct photopatterning may potentially degrade the intrinsic luminescence properties of nanostructured light-emitting materials, especially QDs. Additionally, the fidelity of the QD patterns formed by direct photopatterning needs to be improved.

To avoid these challenges, an alternative approach called photolithographic lift-off patterning can be employed. With this approach, one can avoid subjecting the materials to harsh etching conditions and direct UV exposure by reordering the processing steps44-47, as follows. First, sacrificial PR patterns are formed on a substrate. Next, the target materials are deposited onto the pre-patterned PR substrate. The underlying sacrificial PR patterns are then removed (or “lifted-off”) by using a solvent, also called the stripping solvent. As the sacrificial PR patterns are removed, the region of the target materials supported by the PR patterns is simultaneously stripped away. Eventually, patterns of target materials are formed. Despite these advantages, the process must be implemented carefully for patterning QDs . This is because QDs themselves as well as their luminescent characteristics may be susceptible to degradation during stripping of the sacrificial PR patterns. Therefore, strategies to prevent damage to the QD layer are crucial from the perspective of applying photolithographic lift-off patterning to these materials.

Herein, we report non-destructive photoresist-guided indirect (PIN) photopatterning of QDs by using a low-temperature-activatable ligand crosslinker called Diazo-4-LiXer (2,2-bis((2-diazo-2-phenylacetoxy)methyl)propane-1,3-diyl bis(2-diazo-2-phenylacetate)) that contains four diazo functional groups. Diazo-4-LiXer is structurally designed to induce carbene-mediated crosslinking between neighbouring QDs. Such crosslinking is achieved using terminal diazo groups that are thermally activated to generate carbene intermediates at a low temperature of 110 ℃, which leads to the occurrence of C-H insertion reactions with contacting aliphatic ligands48-50. PIN photopatterning can be applied universally for crosslinking various QD systems and even other nanocrystal systems encapsulated by aliphatic ligands. The low-temperature activation of Diazo-4-LiXer is critical for the success of PIN photopatterning because it creates a crosslinking condition that does not affect the structural properties of the underlying sacrificial PR layer, as well as the intrinsic physical properties of QDs (including their photoluminescence (PL) and electroluminescence (EL) characteristics). We demonstrate that μm-scale patterns of light-emitting QDs (CdSe/ZnSe/ZnS QDs, InP/ZnSeS QDs, and ZnSeTe/ZnSe/ZnS QDs), as well as combinations thereof, can be formed readily through PIN photopatterning by using Diazo-4-LiXer. Most importantly, the fidelity of the resulting patterns is the highest among the reported μm-scale QD patterns formed using photolithographic processes. This is attributed to the fact that the pre-formed PR patterns guide the structure of the QD patterns. In terms of the compatibility of PIN photopatterning with the apparatus used in the display industry and the non-destructive nature of the resulting high-fidelity QD patterns, the proposed method facilitates the realization of high-resolution QD-based optoelectronic devices.

Results
Photoresist-guided indirect photopatterning of QDs

PIN photopatterning of colloidal QDs was performed by following the steps illustrated in Fig. 1b. First, sacrificial PR patterns were formed onto a substrate by following conventional protocols, using KL5301 (from KeCmLab Inc.) and DSP-DJ2 (from Dongjin Semichem Co., Ltd.), both of which are commercially available positive PRs capable of forming thin patterns below 100 nm (the significance of PR pattern thickness is discussed below)51. A mixture of red-emitting CdSe/ZnSe/ZnS QDs and low-temperature-activatable ligand crosslinker (Diazo-4-LiXer) was spin-coated onto the substrate with sacrificial PR patterns. Subsequently, the resulting films were thermally annealed, which induced crosslinking between the ligands of neighbouring QDs. Finally, by stripping the sacrificial PR patterns in a stripping solvent bath with ultrasonication, QDs patterns (inverse of the PR patterns) were generated. Notably, PIN photopatterning is a modified photolithographic lift-off process tailored for solution-processed thin-films, in that it involves crosslinking of the target materials. Crosslinking the target materials endows the resulting patterns with chemical and physical stability against the stripping process of the sacrificial PR pre-patterns and the subsequent patterning process of neighbouring patterns, which is also achieved using a solution process. Without crosslinking of the ligands, the QD films were removed easily upon exposure to the stripping solvent (Fig. 1c). To induce the ligand crosslinking reaction, we emphasize that either high-temperature (> 140 ℃) annealing or UV irradiation step should be avoided. This is because the chemical solubility of the underlying PR patterns can be altered by high-temperature annealing or UV irradiation. Fig. 1d shows, for example, the ratio of thickness variation (referred to as the film thickness retention ratio) before and after soaking KL5301 and DSP-DJ2 PR films (annealed at different temperatures for 20 min) in a striping solvent (i.e., acetone). In principle, the PR films should be completely removed by the stripping process, and, therefore, this ratio should equal zero. This was, in fact, only true for these PR films annealed at temperatures below 120 °C. In contrast, the PR films that were annealed at higher temperatures could not be removed completely under the same stripping condition, indicating that the solubility of the resulting PR films changed because of annealing at such temperatures.

Accordingly, we designed a low-temperature-activatable ligand crosslinker based on a diazo functional group, namely 2-diazo-2-phenylacetate. The diazo group can be activated thermally at temperatures below 120 °C to generate carbene species. These carbene species undergo a C-H insertion reaction with adjacent alkyl chains (Fig. 1e)50. Compared to the previously utilized fluorinated phenyl azide (FPA) compounds for crosslinking ligands of QDs through a nitrene-based C-H insertion reaction30, 34, 52, the 2-diazo-2-phenylacetate compound used herein offers several advantages. First, even at the low annealing temperature of 110 °C, the crosslinking efficiency with alkyl chains of the diazo group approaches 76% (see Methods section, Fig. 1f, Supplementary Note 1, Supplementary Table 1, and Supplementary Figs. 1–24). Therefore, the QD films crosslinked using the diazo-based compound are compatible with PIN photopatterning using various PRs, including KL5301 and DSP-DJ2, the solubility of which does not change at such mild temperatures. Second, carbene-based crosslinking leads to better preservation of the luminescent properties of QDs compared to nitrene-based crosslinking52. Third, the carbene intermediate in this compound, which has a terminal phenyl group and an ester linkage to the core, exists in a secondary form. This steric environment likely reduces the accessibility of the reactive carbene to the inorganic QD surface, thereby suppressing undesired surface reactions and helping to preserve the luminescent properties of QDs30. Consequently, the resulting crosslinked QDs are expected to better retain their luminescent characteristics than those that use reactive intermediates in their primary forms.

By using the diazo functional group as the building block, we synthesized tetra-branched structured 2,2-bis((2-diazo-2-phenylacetoxy)methyl)propane-1,3-diyl bis(2-diazo-2-phenylacetate) (Diazo-4-LiXer). The chemical structure of Diazo-4-LiXer is illustrated in Fig. 1f, and its synthesis is described in Methods section (Supplementary Figs. 25–30). The tetra-branched structure with four diazo moieties was used to increase the crosslinking efficiency of neighbouring QDs30, 53. The results of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed that Diazo-4-LiXer was thermally activated while releasing four equivalents of N2 (Fig. 1g). In this study, the carbenes, formed by releasing N2, reacted with the ligands of neighbouring QDs. The Fourier transform infrared (FT-IR) spectra depicted in Fig. 1h were obtained from CdSe/ZnSe/ZnS QD films before and after they were crosslinked using Diazo-4-LiXer at 110 °C for 20 min (the spectra obtained for different annealing times are shown in Supplementary Fig. 31). The peak at 2087 cm-1, assigned to the C=N2 stretching vibration of Diazo-4-LiXer, vanished after the thermal annealing step. In addition, the peak at 1700 cm-1, assigned to the C=O stretching vibration of Diazo-4-LiXer, shifted to 1725 cm-1 after crosslinking of the ligands. This peak shift is attributed to the generation of new carbon-carbon bonds between the alkyl ligands of the QDs and Diazo-4-LiXer48. These results indicate that the QDs were crosslinked using Diazo-4-LiXer.

Fidelity analysis of QD patterns

After confirming the compliance of Diazo-4-LiXer in crosslinking the QD films, we performed PIN photopatterning. The fidelity of the resulting QD patterns was compared to that of the QD patterns produced by direct photopatterning (which relies on a photoinduced change in solubility of the QD film, Supplementary Fig. 32)30, 34, 35, 50. In fact, because the Diazo-4-LiXer can also undergo UV-induced carbene generation (365 nm, 4 mW cm-2, 20 min), which leads to photocrosslinking of the QD ligands (Supplementary Fig. 33), this crosslinker can alternatively be used for the direct photopatterning of QD films. Notably, this UV exposure condition yielded a film thickness retention ratio above 0.9, indicating that the film was sufficiently crosslinked and that the processing condition was equivalent to the thermal process. Therefore, a direct comparative analysis of the QD patterns prepared using these two methods was possible. The CdSe/ZnSe/ZnS QD patterns prepared using the two photolithographic methods are compared in Fig. 2a,b by using atomic force microscopy (AFM) images and cross-sectional profiles, respectively. Here, the PIN photopatterning was done using DSP-DJ2 PR. These patterns were targeted to exhibit a width of 2 μm. Clearly, the PIN photopatterning yielded patterns with sharper edges compared to the alternative method. The quantitative features of the resulting patterns, such as line-edge roughness (LER), vertical line-width roughness (v-LWR, defined as the deviations of the line edges in the top, middle, and bottom of the pattern), and longitudinal line-width roughness (l-LWR, which denotes the variations in the pattern width along the longitudinal direction of the patterns), were characterized (Fig. 2c, d)54. The PIN photopatterning method produced QD patterns with a LER of 43.1 ± 4.4 nm, l-LWR of 62.3 ± 10.9 nm, and v-LWR of 139.3 ± 9.3 nm. Here, the values are the 3 sigma (3σ) value of the deviations, following the standard used in PR community which statistically indicates the range within which 99.7% of the measured deviations are expected to fall. Importantly, all these parameters were smaller than those achieved with the direct photopatterning process, where the LER was 227.0 ± 10.0 nm, l-LWR of 343.6 ± 7.9 nm, and v-LWR of 455.0 ± 42.0 nm. The improved pattern fidelity of the PIN photopatterns is attributed to the role of the pre-formed PR patterns, which provides structural guidance in defining the QD patterns (AFM images and cross-sectional profiles of the pre-formed PR patterns are shown in Fig. 2a,b, and Supplementary Figs. 34–35). The improved pattern fidelity was additionally attributed to the use of stripping solvent (i.e., acetone) in shaping the QD patterns in the PIN photopatterning process (the stripping solvent should strip only the PR patterns and interact poorly with the target materials), compared to the use of developing solvent (i.e., toluene) in direct photopatterning (the developing solvent is intended to remove uncrosslinked QDs from the film, but it can partially dissolve the loosely-crosslinked QDs in the crosslinked patterns owing to the favourable QD–solvent interaction by nature)55. The LER values of ≈40 nm (based on 3σ) achieved herein, are the smallest among the photolithographically obtained QD patterns reported to date and represent a significant improvement over our previous direct photopatterning work when compared on an equivalent statistical basis. (Fig. 2e and Supplementary Tables 2, 3). To highlight the novelty of PIN photopatterning using Diazo-4-LiXer, we constructed radar charts and the corresponding comparison table (Supplementary Fig. 36 and Supplementary Table 4). The radar charts clearly demonstrate that PIN photopatterning exhibits significantly improved performance compared to previously reported studies. Consistently, the improved pattern fidelity of the structures prepared using PIN photopatterning compared to that of the structures prepared using direct photopatterning was evident across different QD patterns in different dimensions prepared using different PRs (Supplementary Figs. 37–39).

We note the critical importance of precise control over the thickness of the pre-formed PR patterns to achieve high-fidelity QD patterns from PIN photopatterning process. In particular, the thickness of the pre-formed PR patterns should be comparable to that of the desired QD patterns. The results presented in Fig. 2a–d were obtained using 16-nm-thick PR patterns, which matches well with the target thickness of the QD patterns (16 nm) considering their application as the emissive layer in EL devices. Here, this thickness was obtained either by using a commercial PR specifically designed for producing such ultrathin patterns (e.g., DSP-DJ2), or even by reactive-ion-etching thicker PR patterns (70 nm thick KL5301) to the desired thickness. When thicker PR patterns (e.g., 70 nm patterns) were directly used instead, undesirable ear-structures were formed at the edge of the patterns owing to the capillary effect or undesired reactions crosslinking involving the photoactive compound in PR with QDs (Supplementary Note 2 and Supplementary Fig. 40).

Fabrication of mono- and multi-colour QD patterns

Fig. 3a,b show sets of line and circle patterns of the red-emitting (R-) CdSe/ZnSe/ZnS QDs, green-emitting (G-) InP/ZnSeS QDs, and blue-emitting (B-) ZnSeTe/ZnSe/ZnS QDs. Patterns with 2 μm feature sizes could be achieved for these QDs. The minimal feature sizes of the QD patterns are constrained to the dimensions of the attainable PR patterns, which is determined by the type of the PR and the specification of the UV irradiation system. For example, when an i-line stepper instead of a mask aligner was used, QD patterns with 0.8 μm feature sizes and a LER of 45.9 nm could be attained (see Supplementary Note 3 and Supplementary Fig. 41). The height profiles of these patterns, as obtained from AFM measurements, demonstrated their vertical sidewalls with no ear-structures (Fig. 3c,d). Importantly, because the resulting QD patterns were chemically crosslinked, they exhibited good structural tolerance against subsequent solution processes, such as the additional spin-coating of different QD layers or PR layers and the stripping process. Therefore, multi-colour QD patterning could be realized by repeating the PIN photopatterning process as needed (Fig. 3e). In addition, previously deposited QD layers were protected from direct UV exposure during this process, ensuring the preservation of their performance (Supplementary Fig. 42). Fig. 3f presents a fluorescence microscopy image of the RGB patterns formed by sequential deposition of R-, G-, and B-QDs. This image demonstrates that RGB QD patterns with pixel densities exceeding 4,000 PPI can be formed using PIN photopatterning. More importantly, the morphology and height profiles of these patterns, as determined using AFM, indicate that the high fidelity of the patterns is well-preserved after multiple rounds of PIN photopatterning to form QD patterns of different colours (Fig. 3g). We also confirmed that QD patterns with complicated geometry could be obtained through PIN photopatterning (Supplementary Fig. 43). In addition, QD patterns with thickness above 2 μm could be prepared (Supplementary Fig. 44). Moreover, we confirmed that the Diazo-4-LiXer-based PIN photopatterning process can be applied universally to various nanocrystal systems (such as CuInS, InAs, and PbS QDs) so long as they are encapsulated with aliphatic ligands (Supplementary Fig. 45).

Luminescence characteristics of crosslinked QD films

Next, the luminescence characteristics of the crosslinked QD films were examined. Initially, the photoluminescence quantum yield (PLQY) and PL spectra of different QD films crosslinked using Diazo-4-LiXer were evaluated (Fig. 4a), and the data were plotted as a function of the film thickness retention ratio. This ratio, defined as the QD film thickness retained after soaking of the crosslinked QD films in toluene (which is the mother solvent used to cast the QD film), reflects the degree of film crosslinking. Increasing the amount of the crosslinker did not significantly deteriorate the PLQY. This contrasts the gradual decrease in the PL characteristics upon the use of photoactivated nitrene-based LiXers52. The milder influence of crosslinking using Diazo-4-LiXer on the PL characteristics is attributed to the carbene-based reaction (compared to the nitrene-based reaction of the FPA-based crosslinkers) and the secondary reactive intermediate-based reaction (vs. primary reactive intermediate-based reaction), as discussed earlier when designing the crosslinker. Fig. 4b depicts the transient PL decay profiles of the pristine and crosslinked R-, G-, and B-QD films. The R- and G-QD films were crosslinked using 5 wt.% Diazo-4-LiXer, and the B-QD films were crosslinked using 20 wt.% Diazo-4-LiXer. Crosslinking using Diazo-4-LiXer did not affect the luminescence characteristics of the QDs noticeably, which is consistent with the results presented in Fig. 4a. Fig. 4c presents a comparison between the PLQYs of the QD films at different stages of the PIN photopatterning process, including post the thermocrosslinking of the films at 110 °C and post the stripping of the PR pre-patterns. The data were normalized against the PLQYs of the respective pristine QD films. No significant degradation in luminescence characteristics was observed, especially for the R- and G-QDs, even after completion of the entire PIN photopatterning process. A slight degradation in the luminescence characteristics of the B-QDs was observed, and it can potentially be alleviated by using more stable ligand-based blue-emitting QDs that will be developed in the future.

Additionally, the EL characteristics of the crosslinked QD layer were investigated using a light-emitting diode (LED) testbed containing the crosslinked R-QD emissive layer (Fig. 4d). The testbed device included a CdSe/ZnSe/ZnS QD layer as the emissive layer, a zinc magnesium oxide nanoparticle (ZnMgO NP) layer as the electron transport layer (ETL), and a 4,4-bis(N-carbazolyl)-1,1-biphenyl (CBP) layer as the hole transport layer (HTL) (Fig. 4d). The energy band diagram of the fabricated QD-LED is presented in Fig. 4e. For comparative analysis, three types of devices were fabricated: Device 1 with pristine red-emitting CdSe/ZnSe/ZnS QD layer (pristine), Device 2 with the same red-emitting QD layer crosslinked using 5 wt.% Diazo-4-LiXer (crosslinked), and Device 3 with the same red-emitting QD layer crosslinked using 5 wt.% Diazo-4-LiXer and underwent the entire PIN photopatterning process (including PR deposition, development, and stripping steps) (PIN photopatterned). It was found that the emission spectrum of Device 3 exhibited no difference compared to that of a reference device, i.e., Device 1, even after the EML underwent the entire PIN patterning process (Fig. 4f). The current density (J)-voltage (V)-luminance (L) profiles of these three devices (Fig. 4g), as well as the external quantum efficiency (EQE)-J profiles (Fig. 4h), were comparable. Likewise, crosslinking green and blue QDs did not degrade their EL characteristics (Supplementary Fig. 46). The well-preserved device characteristics can be attributed not only to the intrinsic PL properties of the QDs being maintained throughout the PIN photopatterning process (Fig. 4c), but also to the sufficient robustness of the underlying ZnMgO NP layer against the sequential processing steps involved in PIN photopatterning (Supplementary Fig. 47). These results confirm that Diazo-4-LiXer-mediated PIN photopatterning is a non-destructive process that preserves the optoelectronic properties of the QD layers. We further fabricate an RGB pixelated full-colour display through consecutive PIN photopatterning of red-, green- and blue-emitting QDs. Step-by-step optical microscopy during the RGB fabrication cycles corroborates the robustness of this approach, revealing high-fidelity formation of sacrificial PR templates and QD patterns (Supplementary Fig. 48). Building on this reliable protocol, we demonstrate device-level applicability by realising a 10 × 10 passive-matrix full-colour RGB QD-LED array. Stable electroluminescence across driving modes, from monochromatic to full-colour emission, underscores the scalability and versatility of this strategy for integrated high-resolution displays (Fig. 4i,j and Supplementary Movies 1, 2).

Methods
Synthesis of crosslinkers and characterization

Materials: Deuterated chloroform (CDCl3) for measurement of 1H-NMR and 13C-NMR spectra was purchased from Cambridge Isotope Laboratories (USA). 2,2-bis(hydroxymethyl)propane-1,3-diol (99%) and 2-phenylacetyl chloride (98%) were purchased from Alfa Aesar. 4-acetamidobenzenesulfonyl azide (p-ABSA, 97%), 2,3,4,6,7,8,9,10-octahydropyrimido[1,2-a]azepine (DBU, 98%), anhydrous acetonitrile (99.8%), anhydrous dodecane (≥99%), anhydrous methanol (99.8%), and anhydrous toluene (99.8%) were purchased from Sigma Aldrich. Anhydrous dodecane for the C-H insertion reaction was degassed by three freeze-pump-thaw cycles. All other solvents were purchased from Daejung (Republic of Korea) and used without further purification.

Characterization: To identify the molecular structures of all the synthesized products, 1H-NMR and 13C-NMR spectra were measured by Agilent 400 MHz FET-NMR with CDCl3 as a solvent. Mass spectra of synthetic materials were obtained by electrospray ionization-mass spectrometry (ESI) technique using AccuTOF 4G+ DART (JEOL, Japan). Fourier transform infrared spectroscopy (FT-IR) spectra of synthetic materials were obtained using Perkin Elmer Spectrum Two FT-IR Spectrometer.

C-H Insertion reaction of Diazo-1-LiXer with dodecane: To verify that the diazo group undergoes thermolysis and C-H insertion at low temperatures, we synthesized a model compound of Diazo-1-LiXer (Fig. 1f) and monitored the C-H insertion reaction between a model compound of Diazo-1-LiXer (a crosslinkable unit of Diazo-4-LiXer) and neat dodecane (representing the aliphatic ligands of QDs). While the reaction using the model compound was conducted in liquid phase where the reactants have greater conformational freedom and larger diffusivity, we still consider that our model system remains highly relevant to the actual patterning chemistry. This is because once Diazo-4-LiXer is cast into a film with QDs, it must be surrounded completely by the alkyl chains of (i.e., QD ligands), just as in the neat solution model reaction. It is likely that the effective packing density of ligands (containing the reactant -CH2- groups) surrounding Diazo-4-LiXer in the solid state might be higher than that of dodecane (containing the reactant -CH2- groups) surrounding Diazo-1-LiXer in solution, due to the restricted molecular mobility in the solid phase. Considering that the diazo functional groups are still surrounded by an excess of reactive C-H bonds in the solid state, the fundamental crosslinking process would not be significantly different from a stoichiometric perspective, even in the solid-state patterning process. A similar approach using a model reaction was conducted in ref.56, to analyze C-H insertion reactions on polymers such as PDMS and PS.

Synthesis of Diazo-1-LiXer

Methyl 2-phenylacetate, compound 2: A mixture of phenylacetyl chloride (compound 1, 200 mg, 1.47 mmol), triethylamine (1309 mg, 12.94 mmol) and anhydrous dichloromethane (10 mL) was stirred at RT for 10 min under argon atmosphere. Anhydrous methanol (415 mg, 12.94 mmol) was added dropwise to the solution. The reaction mixture was stirred at RT for 24 h. The resulting reaction mixture was extracted three times with dichloromethane (20 mL) and deionized water (20 mL). The combined organic layer was dried using anhydrous MgSO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (ethyl acetate: n-hexane, 1:10 v/v) to obtain compound 2 as a clear oil (843 mg, 87%). 1H-NMR (400 MHz, CDCl3) δ: 7.35‒7.26 (m, 5H), 3.69 (s, 3H), 3.63 (s, 2H) (Supplementary Fig. 1).

Methyl 2-diazo-2-phenylacetate, Diazo-1-LiXer: A mixture of compound 2 (843 mg, 5.61 mmol), p-ABSA (2023 mg, 8.42 mmol), and anhydrous acetonitrile (20 mL) was stirred at RT for 10 min under an argon atmosphere. The DBU (1281 mg, 8.42 mmol) was added dropwise to the solution. The reaction mixture was stirred at RT for 2 h. The resulting reaction mixture was extracted three times with dichloromethane (30 mL) and deionized water (30 mL). The combined organic layer was dried using anhydrous MgSO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (ethyl acetate: n-hexane, 1:10 v/v) to obtain Diazo-1-LiXer as an orange oil (534 mg, 54%). 1H-NMR (400 MHz, CDCl3) δ: 7.49‒7.47 (d, J = 8.0 Hz, 2H), 7.41‒7.37 (t, J = 8.0 Hz, 2H), 7.21‒7.17 (t, J = 8.0 Hz, 1H), 3.87 (s, 3H) (Supplementary Fig. 2).

Experimental procedures of C-H insertion between Diazo-1-LiXer and dodecane

To a 20 mL vial with a magnetic bar, Diazo-1-LiXer (256.6 mg, 1.457 mmol) and anhydrous dodecane (6.5 mL, 4.872 g, 28.6 mmol) were added. The vial was tightly closed with a Teflon vial cap, and the gap between the vial and cap was sealed using Teflon tape. The entire vial was wrapped in aluminium foil to insulate and block out light. The reaction mixture was stirred at RT for 10 min. After 10 min, the vial was placed onto a hot plate which was preheated to 150 °C and stirred for 200 min at 150 °C. For reaction monitoring using 1H-NMR and FT-IR, 100 μL of the reaction mixture were collected every 20 min using a micropipette. For 1H-NMR measurements, 50 μL of the collected reaction mixture was diluted in 600 μL of CDCl3. FT-IR measurements were performed using a single drop of the collected reaction mixture. After 200 min, the remaining reaction mixture in the 20 mL vial was directly purified by silica gel column chromatography (ethyl acetate: n-hexane, 1:10 v/v) to remove residual dodecane and separate the C-H insertion products into three fractions. The obtained fractions (218 mg) were dried under vacuum. Finally, fraction A (130 mg, 0.408 mmol, 60%), fraction B (49 mg, 0.210 mmol, 22%), and fraction C (39 mg, 0.189 mmol, 18%) were obtained. Obtained three fractions of A, B, and C were analyzed using electrospray ionization mass spectroscopy (ESI-MS) and 1H-NMR (the corresponding data are as shown in Supplementary Figs. 3‒9). The mole calculations of each fraction are based on the assumption that the fraction A, B, and C are composed of the molecules that reacted one time, two times, and three times, respectively, with Diazo-1-LiXer although each fraction is not completely pure. The reaction yield of Diazo-1-LiXer would be ≈ 55.4% (i.e., (0.408+0.210+0.189)/1.457). Based on this reaction yield of Diazo-1-LiXer, the crosslinking efficiency of Diazo-4-LiXer is 76.4%.

Synthesis of Diazo-4-LiXer

2,2-bis((2-phenylacetoxy)methyl)propane-1,3-diyl bis(2-phenylacetate), compound 3: A mixture of phenylacetyl chloride (compound 1, 1020 mg, 6.60 mmol) and 2,2-bis(hydroxymethyl)propane-1,3-diol (150 mg, 1.10 mmol) was stirred at 140 °C for 18 h under an argon atmosphere. After 18 h, the reaction mixture was cooled down to RT. The resulting reaction mixture was extracted three times with dichloromethane (30 mL) and deionized water (30 mL). The combined organic layer was dried using anhydrous MgSO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (ethyl acetate: n-hexane, 1:4 v/v) to obtain compound 3 as a white solid (483 mg, 72%). 1H-NMR (400 MHz, CDCl3) δ: 7.29‒7.15 (m, 20H), 3.87 (s, 8H), 3.51 (s, 8H) (Supplementary Fig. 25). 13C-NMR (100 MHz, CDCl3) δ: 170.71, 133.46, 129.15, 128.67, 127.27, 62.06, 42.01, 41.10 (Supplementary Fig. 26). ESI-MS m/z Calcd: 631.2308 Found: 631.23 (M + Na) (Supplementary Fig. 27).

2,2-bis((2-diazo-2-phenylacetoxy)methyl)propane-1,3-diyl bis(2-diazo-2-phenylacetate), Diazo-4-LiXer: A mixture of compound 3 (400 mg, 0.66 mmol), p-ABSA (789 mg, 3.28 mmol) and anhydrous acetonitrile (10 mL) was stirred at RT for 10 min under an argon atmosphere. The DBU (670 mg, 4.40 mmol) was added dropwise to the solution. The reaction mixture was stirred at RT for 12 h. The resulting reaction mixture was extracted three times with dichloromethane (15 mL) and deionized water (15 mL). The combined organic layer was dried using anhydrous MgSO4 and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (ethyl acetate: n-hexane, 1:5 v/v). Finally, the resulting product was recrystallized in CHCl3/MeOH, and then filtered to obtain Diazo-4-LiXer as an orange solid (348 mg, 74%). 1H-NMR (400 MHz, CDCl3) δ: 7.43‒7.34 (m, 16H), 7.21‒7.16 (t, J = 8.0 Hz, 4H), 4.41 (s, 8H) (Supplementary Fig. 28). 13C-NMR (100 MHz, CDCl3) δ: 164.22, 129.00, 126.16, 124.81, 124.09, 62.67, 43.01 (Supplementary Fig. 29). ESI-MS m/z Calcd: 735.1928 Found: 735.19 (M+Na) (Supplementary Fig. 30).

Synthesis of quantum dots

Materials: Cadmium oxide (CdO, 99.998%), selenium (200 mesh, 99.999%), sulfur (trace metal basis, 99.98%), oleic acid (OA, 99%), 1-octadecene (ODE, 90%), tri-n-octylphosphine (TOP, 97%), and zinc acetate (Zn(OAc)2, 99.99%) used for the synthesis of red-emitting QDs were purchased from Sigma Aldrich. Green-emitting InP/ZnSeS QD were purchased from Uniam (Republic of Korea). Tellurium (Te, 99.999%) was purchased from Alfa Aesar. Oleic acid (OA, 99%), 1-octadecene (ODE, ≥90%), selenium (Se, 99.9%) and n-trioctylphosphine (TOP, 99%) used for the synthesis of blue-emitting QDs were purchased from Uniam. 1-dodecanethiol (DDT, ≥ 98 %), diphenylphosphine (DPP, 98%) and anhydrous ethanol (> 99.8 %), and all solvents including toluene (anhydrous 99.8%), ethanol (anhydrous ≥ 99.5 %) were purchased from Sigma-Aldrich. All chemicals were used as received.

Synthesis of red-emitting CdSe/ZnSe/ZnS QDs: QD synthesis was performed using Schlenk line techniques under inert conditions. Zinc oleate (0.5 M, Zn(OA)2) was prepared by heating 20 mmol of Zn(OAc)2 with 12 mL of OA at 150 °C for 1 h, which was subsequently diluted with ODE to a total volume of 40 mL. Trioctylphosphine selenium (1 M, TOPSe) and trioctylphosphine sulfur (1 M, TOPS) were prepared by stirring 1 mmol of Se or S with 1 mL of TOP at RT overnight. For red-emitting CdSe/ZnSe/ZnS QDs (r = 3.0 nm, l = 5.0 nm, h = 2.0 nm), a mixture of 0.3 mmol of CdO, 1 mmol of OA, and 6 mL of ODE was loaded into a 3-neck flask and heated up to 300 °C under inert conditions to form a clear solution of Cd(OA)2. Then, 0.5 mL of TOPSe (1 M) was rapidly injected into the reaction flask. After 3 min, 5 mL of Cd, Se stock solution in ODE was injected for the growth of CdSe cores. Next, 20 mL of Zn(OA)2 (0.5 M) and 7 mL of TOPSe were added successively for the growth of the ZnSe shell. Finally, 10 mL of Zn(OA)2 (0.5 M) and 5 mL of TOPS were added for the growth of the ZnS outer shell. The synthesized QDs were purified five times by the precipitation/redispersion (ethanol/toluene) method.

Synthesis of blue-emitting ZnSeTe/ZnSe/ZnS QDs: QD synthesis was performed using Schlenk line techniques under inert conditions. Zn(OA)2 (0.5 M) stock solutions in ODE were prepared for cation precursors. TOPSe (2 M), trioctylphosphine telluride (0.05 M, TOPTe), and diphenylphosphine selenide (0.2 M, DPPSe) were prepared for anion precursors. For Zn(OA)2 preparation, 50 mmol of Zn(Ac)2 and 100 mmol of OA were mixed in a flask, degassed at 130 ℃ for 6 h, backfilled with N2 gas, and then diluted to 0.5 M concentration with ODE. For TOPSe preparation, 100 mmol of Se powder was mixed with 50 mL of TOP at 160 ℃ for 5 h under inert conditions. The same procedure was adopted for preparing TOPTe. For DPPSe, 4 mmol of Se powder was reacted with 2 mL of DPP at 200 ℃ until complete reaction under inert conditions, and diluted to 0.2 M concentration with toluene at RT.

ZnSeTe/ZnSe/ZnS QDs (r = 1.8 nm, l = 1.8 nm, h = 0.6 nm) were synthesized following the previously reported method with minor modifications57. 1.2 mL of Zn(OA)2 (0.5 M) and 10 mL of ODE were stirred and degassed at 110 ℃ in a 3-neck round flask. After 1 h of degassing to remove water and oxygen completely, it was backfilled with N2 gas. Then, the mixture of 1.43 mL DPPSe (0.2 M) and 0.3 mL TOPTe (0.05 M) was injected to synthesize ZnSe0.95Te0.05 cores at 230 ℃ and maintained for 30 min. The temperature was then raised to 300 ℃ for 15 min to ensure complete growth of ZnSe0.95Te0.05 cores (r = 1.8 nm). For further ZnSe shell growth on the core, 2 / 3.4 / 5 mL of Zn(OA)2 (0.5 M) and 0.25 / 0.425 / 0.625 mL of TOPSe (2 M) were injected sequentially at 300 ℃. Additional injection of 10 mL of Zn(OA)2 (0.5 M) and 0.5 mL of DDT results in 0.6 nm thick ZnS shell growth. The synthesized QDs were purified two times by the precipitation/redispersion (ethanol/toluene) method.

Materials for photopatterning of QDs and device fabrication

DSP-DJ2 PR was purchased from Dongjin Semichem Co., Ltd. (Republic of Korea). KL5301 and KL5315 PR were purchased from Kemlab Inc. (USA). AZ 300 MIF developer was purchased from AZ Electronic Materials (USA). ITO patterned glass substrates were purchased from AMG (Republic of Korea). 4,4-Bis(N-carbazolyl)-1,1-biphenyl (CBP, 99.9%) was purchased from OSM (Republic of Korea). Molybdenum oxide (MoO3, 99.95%) and aluminium (Al, 99.999%) metal sources were purchased from Taewon Scientific Co. (TASCO, Republic of Korea).

Photolithography of PR and thickness control

All substrates were cleaned in an ultrasonic bath with acetone and isopropyl alcohol for 10 min each and then dried with nitrogen gun. Selection criteria for compatible photoresists to our PIN photopatterning are provided in Supplementary Note 4. In case of DSP- DJ2, PR was coated through a multi-step spin-coating process (500 rpm for 3 s, 2700 rpm for 25 s, and 500 rpm for 3 s), and the resulting film was soft-baked on a hot plate at 100 ℃ for 110 s. After soft-baking, PR films were irradiated for 2.1 s with a UV light source (365 nm, 9.8 mW cm-2) through a photomask using a mask aligner (AMDA-400LJ, MIDAS system) and were then hard-baked on a hot plate at 110 ℃ for 110 s. Hard-baked PR film was developed for 4 s in AZ 300 MIF developer diluted to 0.15 N (from 0.26 N tetramethylammonium hydroxide (TMAH) solution) and was rinsed with deionized water. The resulting thickness of the PR patterns was 16 nm.

In case of KL5301, PR was coated through a multi-step spin-coating process (500 rpm for 5 s, 4500 rpm for 40 s, and 2000 rpm for 2 s), and the resulting film was soft-baked on a hot plate at 105 ℃ for 1 min. After soft-baking, PR films were irradiated for 9 s with a UV light source (365 nm, 9.8 mW cm-2) through a photomask using a mask aligner (MDA-400LJ, MIDAS system) and then were hard-baked on a hot plate at 115 ℃ for 1 min. Hard-baked PR film was developed in AZ 300 MIF developer for 4 s and was rinsed with deionized water. The resulting thickness of the PR patterns was 70 nm. To reduce the thickness, the patterns were exposed to reactive ion etching (RIE). RIE was performed over PR patterned substrates using Ar/O2 mixed gas (40 cm3 STP min-1 for Ar and 20 cm3 STP min-1 for O2 gas) with 50 W RF power. After the etching process, the resulting thickness of the PR patterns was reduced to 17 nm.

PIN photopatterning of QDs

To form 70 nm-thick CdSe/ZnSe/ZnS QD patterns, Diazo-4-LiXer (5 wt.% relative to QDs) was added to solution of CdSe/ZnSe/ZnS QDs in toluene (55 mg mL-1). The mixture solution was spin-coated (4000 rpm for 30 s) onto the PR pre-patterned substrate (PR thickness = 70 nm), and the resulting film was annealed at 110 ℃ for 20 min to induce crosslinking reaction. PR patterns were then stripped in ultrasonic bath with acetone for 1 min and dried using a nitrogen gun.

To form 20 nm-thick QD patterns, Diazo-4-LiXer was added to QD solutions in toluene (15 mg mL-1) in different loadings (5 wt.% for CdSe/ZnSe/ZnS and InP/ZnSeS QDs, and 20 wt.% for ZnSeTe/ZnSe/ZnS QD). The mixture solution was then spin-coated (4000 rpm for 30 s) onto the PR pre-patterned substrate (PR thickness = 17 nm), and the resulting film was annealed at 110 ℃ for 20 min to induce crosslinking reaction. PR patterns were then stripped in ultrasonic bath with acetone for 1 min and dried using a nitrogen gun.

To create a multi-colour pattern, different QDs were patterned in sequence. Initially, 20-nm thick red-emitting CdSe/ZnSe/ZnS QDs were patterned through the method described above. Subsequently, PR pre-patterns were formed onto the substrate with red-emitting CdSe/ZnSe/ZnS QD patterns. Following, green-emitting InP/ZnSeS QDs were patterned through the method described above. By repeating the above process once again to PR pre-patterns and following the QD layer deposition and PIN photopatterning process, blue-emitting ZnSeTe/ZnSe/ZnS QD patterns could be formed. This process enabled the formation of multi-colour QD patterns based on various types of QDs.

Direct photo-patterning of QDs

Diazo-4-LiXer (5 wt.% relative to QDs) was added to red-emitting CdSe/ZnSe/ZnS QD solutions in toluene (70 nm-thick QD patterns, 60 mg mL-1; 20 nm-thick QD patterns, 15 mg mL-1). The mixture solution was spin-coated (70 nm-thick QD patterns, 2000 rpm for 60 s; 20 nm-thick QD patterns, 4000 rpm for 30 s) onto a substrate. The resulting film was crosslinked via UV (365 nm, 4 mW cm-2, corresponding exposure 4.8 J cm-2) through a photomask. Subsequently, the films were developed using fresh toluene solvent, that could selectively remove the uncrosslinked regimes of QD film and leaves red-emitting CdSe/ZnSe/ZnS QD patterns.

Characterization

UV-visible absorption spectra were recorded using a V-770 UV-Vis-NIR spectrophotometer (JASCO, Japan). Crosslinking reaction in the QD film was verified by using a FT-IR4700 spectroscopy (JASCO) in an attenuated total reflection (ATR) mode using bare Si substrates. Surface morphology and height profile of the patterned QD and PR films were examined using a Park XE7 and an NX10 AFM systems (Park Systems, Republic of Korea) under ambient conditions in a noncontact mode. For structural parameters analysis of the patterns including LER, l-LWR, and v-LWR, data were collected from 5 μm × 5 μm AFM images that were specifically captured with 1024-line scans, yielding an AFM image pixel size ≈5 nm. High-resolution single- and multi-colour patterns of the PR and QDs were fabricated using an MDA-400LJ Mask Aligner (Midas system, Republic of Korea). PLQY of QD films are measured by Quantaurus-QY absolute PL quantum yield spectrometer (Hamamatsu photonics, Japan) at 400 nm excitation wavelength. Time-resolved photoluminescence (TRPL) analysis was carried out using a time-correlated single photon counting (TCSPC) system. Fluorescence spectra were measured using a FS-2 fluorescence spectrometer (Scinco, USRA) at 400 nm excitation wavelength. The electrical properties of the crosslinked QD films were examined by employing a Keithley 236 source measurement unit and a Keithley 2000 multimeter. These instruments were connected to calibrated Si photodiodes for accurate measurements.

Device fabrication

Pre-patterned ITO substrates were cleaned in an ultrasonic bath with deionized water, acetone, and isopropyl alcohol for 10 min each and were dried using a nitrogen gun. Entire QD-LEDs fabrication was carried out under inert conditions. 20 mg mL-1 of ZnMgO NPs were spin-coated onto a pre-patterned ITO substrate at 4000 rpm for 30 s, and the film was annealed at 80 ℃ for 30 min. 15 mg mL-1 of red-emitting CdSe/ZnSe/ZnS QDs (or 15 mg mL-1 of green-emtting InP/ZnSeS QDs, blue-emitting 10 mg mL-1 of ZnSeTe/ZnSe/ZnS QDs) added with 5 wt.% of Diazo-4-LiXer were then spin-coated onto ZnMgO NPs at 4000 rpm for 30 s and the resulting QD film was annealed at 110 ℃ for 20 min. (In case of fabricating the 10 × 10 RGB pixel array, the red-, green-, and blue-emitting QD patterns were subsequently PIN photopatterned including three cycles of PR patterning, QD film casting, thermal annealing, and the PR stripping steps). CBP (60 nm), MoO3 (10 nm) and Al (120 nm) were thermally deposited on the QDs films under the pressure of ≈ 10-7 torr at deposition rate of 0.4-1.0, 0.1-0.2 and 1.0-2.0 Å s-1, respectively. Note that the size of the EML pattern for Device 3 was equivalent to the size of the overlapping area between the top and bottom electrodes (1.4 mm by 1.4 mm), and therefore, the electrical leakage issue was not an issue, despite the use of patterned EML between non-patterned HTL and ETL.

Statistics and reproducibility: Unless otherwise indicated, data were obtained from at least three independently prepared samples. Optical microscopy and AFM images are representative of results obtained from these independent samples.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this manuscript, Lim et al. report the indirect patterning of quantum dot (QD) films, which involves the thermal crosslinking of QD films and the templates formed with conventional photoresists. The indirect patterning approach, coined as PIN, benefits from both the conventional photolithographic patterning with resists and the carbene-based crosslinking chemistry recently developed for direct QD photopatterning. The authors demonstrate the thermal crosslinking of QDs at relatively low temperatures, the patterning of QDs with high resolution (~4000 ppi) and fidelity, the preservation of PLQYs (almost fully preserved for red and green QDs), as well as preliminary demonstration of the performance of QLEDs made from red, CdSe-based QDs. As summarized in Supplementary Table 2, the main advantage of this method is the high patterning quality. The line edge roughness can be as small as 3.7 nm. Overall, it is an interesting work with well-presented results. However, more experimental data and discussions need to be provided to support the patterning chemistry, the adaptability of this patterning approach, and the claim of the ultra-low line edge roughness, etc. Additionally, compared to the recently developed direct photopatterning strategies (some of them developed by the same authors), the applicability of this indirect approach (or PIN) in making high-performance, pixelated QLEDs is unclear. Based on these considerations, I do not think the work meets the criteria of Nature Communications, at least in its current form. Detailed comments are listed below.\n1) On the patterning chemistry, I appreciate the detailed characterizations of the synthesis of diazo-based crosslinkers and the reaction between diazo-1-Lixer and dodecane. FTIR, NMR, and Mass spec data clearly support the reaction between the model molecules (diazo-1-Lixer and dodecane). Similar approaches have been used to characterize the crosslinking reactions for polymers. It is thus clear that the diazo-4-Lixer can effectively crosslink the ligands on QD surface at >110 oC. However, one should note that the model reaction does not fully reflect the real situation during patterning. First, the model reaction occurs in solution while the patterning chemistry occurs in the solid state. Second, the model reaction uses a large excess of dodecane (which also served as the solvent), while the ligands and crosslinkers may have similar molar amount during patterning. Therefore, the products in the model reaction (60% of them are 1:1 adducts of dodecane and diazo-1-Lixer, as shown Suppl. Fig. 1) may be drastically different from those in the patterning. It would be great if the authors can add comments on this in the manuscript and SI to avoid misleading information.\n2) NMR data on the thermal reaction between diazo-1-LiXer and dodecane. In Suppl. Fig. 1b, what is the assignment of the resonance at about 3.62 ppm? In the full spectra in Suppl. Fig. 8, why the group of peaks between 7.4 and 7.6 ppm (presumably related to phenyl groups in diazo-1-LiXer) were almost fully suppressed after 80 min? The phenyl resonance should not disappear? And the suppression of phenyl resonance appears to synchronize with the suppression of the methyl resonance shown in Suppl. Fig. 1b. Please explain this.\n3) A key but missing piece of characterization is the possible crosslinking between the QD ligands and the photoresist (KL5301 in this case). What are the major functional groups in this photoresist? Can we rule out the possibility of reactions between ligands and photoresists? The reaction may not be omitted due to the effective C-H insertion reaction of diazo-based linkers. In PIN, QD films locate on top of and between the “walls” of photoresists. The reaction between QDs and photoresists (especially the sidewall part) may complicate the stripping step and affect the patterning quality. Characterizing the reaction between QD ligands and photoresists in the presence of diazo-based crosslinkers will help to clarify this and also provide more guidance on the compatibility of this indirect patterning chemistry (PIN) with different types of photoresists.\n4) On the choice of photoresists and the applicability of this approach to other photoresists. Related to the discussions in 3), why the authors select KL5301? In conventional photolithographic patterning of QDs, other photoresists (e.g., AZ series, in Journal of the Society for Information Display 26, 121-127 (2018)) were used. What are the selection criteria for the photoresists? Can PIN apply to other types of photoresists? Based on the results, KL 5301 may not be the best choice. For example, it cannot make templates for thin QD films (e.g., 20 nm, suitable for QLEDs) and require additional dry etching. The stripping process of this photoresist also requires ultrasonication. The authors may need to provide evidence on the applicability of PIN to other photoresists.\n5) Fig. 1c compares the quality of QD patterns with or w/o crosslinking. What was the stripping solvent used here? Was it acetone? It is a little surprising to see the poor adhesion of QD layers after acetone treatment. For comparison, solid state ligand exchange or solvent treatment in acetone or alcohols are widely used to change the surface chemistry or ligand density of QD films, for applications in solar cells (as shown by Prof. Sargent and others). QD films remain mostly intact after being immersed in those solvents, because they are “nonsolvents” for QDs. Can the authors explain the poor adhesion of QD films in this case?\n6) On the patterning fidelity of QDs, a key advantage of PIN is the ultra-low line edge roughness of QD patterns, which is several times or one order of magnitude smaller than those for direct optical patterning methods. The low line edge roughness may follow from that of the patterned photoresists. However, based on Suppl. Fig. 27, the line edge roughness of the photoresist (KL 5301) was larger than 10 nm. The patterned QDs derived from the photoresist templates show much improved line edge roughness (about 3.7 nm). As the patterning fidelity is a key advantage for PIN, the authors may need to double check and explain this observation.\n7) Additionally, many photoresists have non-rectangular cross-section profiles. These feature is related to the different degree of photochemistry along the depth of photoresists and thus opposite for positive and negative photoresists. These features, although beneficial for the subsequent lift-off and etching processes in conventional microfabs, may behave as intrinsic limits for the linewidth variation of patterned QD films. KL 5300 series seem to have such non-rectangular cross-section as well (http://www.nm-tech.co.kr/?act=shop.goods_view&GS=26&GC=GD0100). Have the authors observe such effects on the QD patterns? The linewidth variation (270 nm) seems quite large compared to the line edge roughness, probably due to this reason?\n8) Fig. 2c and Suppl. Fig. 28-30 compares the patterning fidelity when using thermal or photoreactions of diazo-4-LiXer. It is convincing that the indirect PIN approach using thermal reactions and photoresist show improved fidelity. However, one may argue the validity of using the direct optical patterning with diazo-4-LiXer as the reference. As shown in Suppl. Fig. 26, this carbene-based cross-linker has low efficiency in photochemical reactions. Even a large UV dose (~5 J/cm2) can only convert a small amount of diazo-4-LiXer into carbene radicals. Consequently, the photopatterned QD films would not be fully cross-linked. It would be better if the authors can provide additional discussions in the text.\n9) Fig. 2c provides the LER, linewidth variation, and surface roughness of ~70 nm-thick films. Could the authors also provide these parameters for ~20 nm-thick patterns, which were used in making QLEDs?\n10) For the full colored pattern (Fig. 3f), the red and green dots look uniform but there are significant defects/irregularity for the blue dots. Was it related to the larger amount of crosslinkers needed for blue QDs?\n11) On the PLQY properties, when comparing diazo- and azide-based crosslinkers, the authors mentioned “Third, the carbene in the compound exists in a secondary form and therefore, undesired surface reactions involving the reactive carbene intermediate that occur directly on the QD surface can be sterically suppressed”, and also similar description in the paragraph on the PLQY properties. What does this mean? Can the authors provide more specific discussion?\n12) On the applicability of PIN in fabricating pixelated QLEDs. An important shortcoming of this method is that it needs some patterning steps hard to be compatible with QLED fabrication procedures. These include the dry etching of photoresists to decrease the height of templates (may deteriorate the underlying layers, ZnO in this device geometry and more severely if using the organic transport layer below QDs), ultrasonication during the lift-off step (may affect the underlying layers). According to the Methods, the QLED device was made without involving the photoresist layers and no pixelated QLEDs were made. The results shown in Fig. 4 indicate that the thermal crosslinking reaction does not affect the performance of QLEDs made from red, CdSe-based QDs. However, the effects of the key steps in making the patterns were not explored. This may be a major concern for the applicability of PIN or similar indirect patterning methods in building high-fidelity, high-performance QLED displays.\n13) Related to 12), Suppl. Table S2 compares PIN with recently reported direct optical patterning methods. PIN shows smaller line edge roughness and comparable preservation of PLQYs (compared to the work by some of the same authors and other groups). However, it is very important to include the status of QLED performance (at least EQEs) of these patterning approach. Compared to previous direct patterning methods, the EQEs reported here is not high and whether PIN (at least when used with KL 5301) is suitable for building pixelated QLED devices remains unclear.\n14) In conventional photolithography of QDs, the photoresists can help making thick QD films for other purposes, such as photodetectors. Is PIN able to make QD films with micrometer-scale thickness?", "reviewer_2": "This manuscript reported a crosslinking-assisted indirect photopatterning of quantum dots using the traditional photolithography method. With the assistance of Diazo-4-LiXer, multi-color features were obtained, and decent device performance was achieved. By using these unique ligands, it seems that it is possible to solve the problems on the technology bench. However, some of the problems may be caused arbitrarily. For example, by using conventional photolithography or lift-off method, the QD patterns were not affected that much, as shown in Fig 1c, even if the pixel size was smaller than 5 μm (ACS Appl. Mater. Interfaces 2021, 13, 36, 43075; Nano Lett. 2016, 16, 6946, Nanotechnology 2014, 25, 175302). To demonstrate the novelty of the method, smaller features (maybe < 1 um) should be prepared because this is really challenging using traditional photolithography. In addition, from a scientific point of view, the present manuscript lacks novelty. The authors failed to demonstrate the uniqueness of the ligands they proposed in this manuscript compared to other ligands. The nitrene- and carbene-based photocrosslinkers are systematically studied. Most of them are both photo-sensitive and thermal-sensitive. What are the advantages of diazo-4-LiXer over them (Angew. Chem. Int. Ed. 2022, 61, e202202633, ACS Nano 2022, 16, 13674)? Why do people use these ligands in conventional lithography if they are inherently capable of non-destructive patterning? The original PR pattern was 70 nm, and the resulting thickness was reduced to 17 nm after the etching process. Will this treatment affect the previous QD layers? What is the device performance of green and blue QLEDs? Suppose the authors claimed that this ion etching technique helps solve conventional lithography problems when patterning quantum dots. In that case, it is particularly important to confirm the performance of quantum dots after processing using the performance of QLED devices. Based on the abovementioned issues, I cannot recommend publishing this manuscript at this stage, but I encourage the authors to improve the quality of their manuscript and resubmit it.", "reviewer_3": "In the manuscript, the authors designed a low-temperature-activatable ligand crosslinker, Diazo-4-LiXer, which can bridge neighboring QDs at low temperature, thereby preserving the luminous properties of QDs. Micrometer-scale QDs patterns with excellent fidelity were formed using crosslinking-assisted, photoresist-guided indirect (PIN) photopatterning. And full-color RGB QD patterns with a resolution exceeding 4000 PPI were obtained by continuously applying PIN photopatterning technology to R-, G-, and B-QD, demonstrating the potential application of low-temperature cross-linking assisted PIN photopatterning in the display industry. I recommend its publication after major revision.\n1. It is recommended to create patterned quantum dot fluorescence microscopy images with complex logos, microdot/diamond/triangle arrays, letters, and line forms to more intuitively display the characteristics of this approach for producing high-resolution and high-fidelity patterns.\n2. In the process of forming multi-color quantum dot patterns, how can the negative impact of UV light and RIE on the performance of quantum dots be mitigated or eliminated?\n3. This approach preserves quantum dot performance during patterning, however, high temperatures will still be encountered in subsequent applications. What are the prospects of employing this strategy?\n4. Why choose the Crosslinking of Diazo-4-LiXer?\n5. The method for photopatterning can be expand for other QDs? Some other QDs may be utilized for assessment."}, "author_response": "[General comment] In this manuscript, Lim et al. report the indirect patterning of quantum dot (QD) films, which involves the thermal crosslinking of QD films and the templates formed with conventional photoresists. The indirect patterning approach, coined as PIN, benefits from both the conventional photolithographic patterning with resists and the carbene-based crosslinking chemistry recently developed for direct QD photopatterning. The authors demonstrate the thermal crosslinking of QDs at relatively low temperatures, the patterning of QDs with high resolution (~4000 ppi) and fidelity, the preservation of PLQYs (almost fully preserved for red and green QDs), as well as preliminary demonstration of the performance of QLEDs made from red, CdSe-based QDs. As summarized in Supplementary Table 2, the main advantage of this method is the high patterning quality. The line edge roughness can be as small as 3.7 nm. Overall, it is an interesting work with well-presented results. However, more experimental data and discussions need to be provided to support the patterning chemistry, the adaptability of this patterning approach, and the claim of the ultra-low line edge roughness, etc. Additionally, compared to the recently developed direct photopatterning strategies (some of them developed by the same authors), the applicability of this indirect approach (or PIN) in making high-performance, pixelated QLEDs is unclear. Based on these considerations, I do not think the work meets the criteria of Nature Communications, at least in its current form. Detailed comments are listed below.\n[Response] We appreciate the Reviewer's constructive and thoughtful comments on our work. In response to the comments, we have revised the manuscript and figures as well as Supplementary Information.\nList of changes made in Manuscript\n- (page 4, line 1) We have updated the references in this sentence to include recently published studies (Refs. #37-43) to better reflect the current state of research on direct photopatterning of quantum dots.\n- (page 5, line 13 – page 5, line 15 / page 5, line 29 – page 6, line 3 / page 8, line 18 / Fig. 1d)\nData and descriptions related to the DSP-DJ2 PR have been added.\n- (page 8, line 15 – page 8, line 16) Crosslinking efficiency of the Diazo-4-LiXer have been\nchanged.\n1\n- (page 8, line 21 – page 8, line 24) Explanation on why forming secondary carbene intermediate\ncan be beneficial for preventing degradation of QDs upon crosslinking is added, along with a\nsupporting citation (Ref. #30).\n- (page 9, line 19 – page 9, line 21) Additional explanations regarding the UV exposure\nconditions in direct photopatterning have been provided.\n- (page 9, line 27 – page 10, line 7) Quantitative analyses of the pattern fidelity, including LER,\nl-LWR, and v-LWR, have been added to compare the performance of PIN and direct\nphotopatterning.\n- (page 10, line 1) An additional reference related to LER and LWR has been added (Ref. #54).\n- (page 10, line 16) An additional reference has been added to support the sentence (Ref. #55).\n- (page 11, line 15 – page 12, line 9 / Fig. 2) We completely rewrote the description on the\nthickness control of Fig. 2 and renewed the data based on QD patterns obtained using DSP-\nDJ2 photoresist.\n- (page 12, line 30 – page 13, line 1) Additional data on micrometer-thick QD patterns formed\nby PIN photopatterning have been included.\n- (page 16, line 3 – page 16, line 19) The paragraph describing the EL performance of devices\nwith various EML conditions has been revised.\n- (page 21, line 3 – page 21, line 6) We added the specific conditions that were used to collect\nAFM images for structural parameters analysis of the patterns including LER, l-LWR, and v-\nLWR in the Methods section.\n- (page 21, line 25 – page 21, line 28) Details related to the pixelated devices have been added\nto the Methods section.\nList of changes made in Supplementary Information\n- (Supplementary Note 1 and 4) The synthesis of crosslinkers and characterization and the\nsynthesis of quantum dots are described in Supplementary Note 1 and Supplementary Note\n4, respectively.\n- (Supplementary Note 2) Additional details on the impact of PR–QD crosslinking on ear\nstructures and pattern fidelity have been provided.\n- (Supplementary Note 5) Selection criteria for photoresists compatible with our PIN\nphotopatterning have been provided.\n- (Supplementary Figs. 14–24) To avoid misunderstanding, we have removed the original 1H-\nNMR spectra (Supplementary Figs. 7–8 in the original SI) and replaced them with new ones\n2\nshown in Fig. R1.1 in full-range including integral values of proton peaks (Supplementary\nFigs. 14–24 in the revised SI).\n- (Supplementary Table 2-3) The experimental data regarding the pattern fidelity (LER, l-LWR,\nand v-LWR) of QD patterns have been revised, and EQE data have been added to\nSupplementary Table 2. In addition, new references related to direct photopatterning have\nbeen added (Ref. #S10-11).\n- (Supplementary Fig. 36) Information of the pre-formed DSP-DJ2 PR patterns has been\nincluded.\n- (Supplementary Fig. 37) The line edge roughness of KL5301 PR pattern (Supplementary\nFig. 37c) used in this study has been revised.\n- (Supplementary Fig. 38-40) The experimental data about the pattern fidelity (LER, l-LWR\nand v-LWR) of QD patterns lifted-off from KL5301 PR have been revised.\n- (Supplementary Fig. 41) The comparison of “ear structures” in QD patterns has been added.\n- (Supplementary Fig. 42) QD patterns with a 1 μm pattern width obtained via PIN\nphotopatterning have been included.\n- (Supplementary Fig. 45) Additional data on micrometer-thick QD patterns formed by PIN\nphotopatterning have been included.\n3\n[Comment #1] On the patterning chemistry, I appreciate the detailed characterizations of the synthesis\nof diazo-based crosslinkers and the reaction between Diazo-1-LiXer and dodecane. FTIR, NMR, and\nMass spec data clearly support the reaction between the model molecules (Diazo-1-LiXer and\ndodecane). Similar approaches have been used to characterize the crosslinking reactions for polymers.\nIt is thus clear that the Diazo-4-LiXer can effectively crosslink the ligands on QD surface at >110 oC.\nHowever, one should note that the model reaction does not fully reflect the real situation during\npatterning. First, the model reaction occurs in solution while the patterning chemistry occurs in the\nsolid state. Second, the model reaction uses a large excess of dodecane (which also served as the\nsolvent), while the ligands and crosslinkers may have similar molar amount during patterning.\nTherefore, the products in the model reaction (60% of them are 1:1 adducts of dodecane and Diazo-1-\nLiXer, as shown Suppl. Fig. 1) may be drastically different from those in the patterning. It would be\ngreat if the authors can add comments on this in the manuscript and SI to avoid misleading information.\n[Response] We appreciate the insightful comments on the differences between the model reaction\nand the actual patterning process. We acknowledge that the model reaction was conducted in\nsolution where the reactants have greater conformational freedom and larger diffusivity, whereas\nthe crosslinking reaction in the patterning process occurs in the solid state. Additionally, we\nrecognize that the molar ratio of reactants differs between these two conditions, as the model\nreaction was performed with an excess of dodecane, while in the solid state, the molar ratio of\nligands and crosslinkers is not closer to 1:1 (which was in fact ~8:1 from our estimation). In addition,\nit was unfortunate that the model reaction experiment using dodecane could not be conducted\ndirectly using Diazo-4-LiXer, Diazo-4-LiXer showed poor solubility in dodecane. Alternatively, we\nutilized Diazo-1-LiXer, which exhibited good solubility in dodecane.\nHowever, we still consider that our model system remains highly relevant to the actual\npatterning chemistry. Once Diazo-4-Lixer is cast into a film with quantum dots (QDs), it must be\nsurrounded completely by the alkyl chains, just as in the neat solution model reaction. Additionally,\nthe effective packing density of ligands surrounding Diazo-4-LiXer in the solid state may be higher\nthan that of dodecane surrounding Diazo-1-LiXer in solution, due to the restricted molecular\nmobility in the solid phase. (Perhaps this is why the time required to attain equivalent degree of\ncrosslinking was shorter (20 min) for the solid-state patterning process compared to that (120 min)\nfor the solution phase model reaction.) Considering that the diazo functional groups are still\nsurrounded by an excess of reactive C-H bonds in the solid state, the fundamental crosslinking\nprocess would not be significantly different from a stoichiometric perspective, even in the solid-\nstate patterning process. Note that a similar approach using a model reaction was conducted\n4\npreviouslyR1, to analyze C-H insertion reactions on polymers such as PDMS and PS.\nReferences\nR1. Lepage, M. L. et al. A broadly applicable cross-linker for aliphatic polymers containing C–\nH bonds. Science 366, 875-878 (2019).\nTo clarify this point and avoid potential misunderstandings, we have added the following\ndiscussions in Supplementary Note 1.\nChanges made in Supplementary Information\nSupplementary Note 1. Synthesis of Crosslinker and Characterization\nC-H Insertion reaction of Diazo-1-LiXer with dodecane: To verify that the diazo group undergoes\nthermolysis and C-H insertion at low temperatures, we synthesized a model compound of Diazo-1-\nLiXer (Supplementary Fig. 1) and monitored the C-H insertion reaction between a model\ncompound of Diazo-1-LiXer (a crosslinkable unit of Diazo-4-LiXer) and neat dodecane\n(representing the aliphatic ligands of QDs).\nWhile the reaction using the model compound was conducted in liquid phase where the\nreactants have greater conformational freedom and larger diffusivity, we still consider that our\nmodel system remains highly relevant to the actual patterning chemistry. This is because once\nDiazo-4-Lixer is cast into a film with QDs, it must be surrounded completely by the alkyl chains of\n(i.e., QD ligands), just as in the neat solution model reaction. It is likely that the effective packing\ndensity of ligands (containing the reactant -CH - groups) surrounding Diazo-4-Lixer in the solid\n2\nstate might be higher than that of dodecane (containing the reactant -CH - groups) surrounding\nthat the diazo functional groups are still surrounded by an excess of reactive C-H bonds in the solid\nstate, the fundamental crosslinking process would not be significantly different from a\nstoichiometric perspective, even in the solid-state patterning process. A similar approach using a\nmodel reaction was conducted previouslyS1, to analyze C-H insertion reactions on polymers such\nas PDMS and PS.\nRef. #S1. Lepage, M. L. et al. A broadly applicable cross-linker for aliphatic polymers containing\nC–H bonds. Science 366, 875-878 (2019).\n5\n[Comment #2] NMR data on the thermal reaction between diazo-1-LiXer and dodecane. In Suppl. Fig.\n1b, what is the assignment of the resonance at about 3.62 ppm? In the full spectra in Suppl. Fig. 8, why\nthe group of peaks between 7.4 and 7.6 ppm (presumably related to phenyl groups in diazo-1-LiXer)\nwere almost fully suppressed after 80 min? The phenyl resonance should not disappear? And the\nsuppression of phenyl resonance appears to synchronize with the suppression of the methyl resonance\nshown in Suppl. Fig. 1b. Please explain this.\n[Response] We appreciate the questions regarding the NMR data. By revisiting the data, we had to\nmodify our interpretation on the reaction from the model reaction.\n1. The resonance at 3.62 ppm: The 3.62 ppm peak is expected to be the H peak of the methyl ester\ngroup in the C-H insertion products, as its intensity increases with the progression of the reaction.\n2. The suppression of phenyl resonances between 7.4 and 7.6 ppm: We acknowledge that the peaks\nat 7.4 and 7.6 ppm correspond to the phenyl group in Diazo-1-Lixer, and their intensity appears\nto decrease after 80 minutes, as observed in the spectra. However, we realized that when\nintegrating the entire aromatic region within the spectra, including a broad background peak,\nwe confirm that the expected total number of aromatic protons (5) remains nearly unchanged.\nTherefore, we interpret that some other reactions (in addition to the dominant C-H insertion\nreaction by the carbene) are included and yield the broad background in the aromatic region.\nOne possible origin of broad peak appearance is that multiple isomers are generated when\nDiazo-1-Lixer reacts with dodecane, leading to slight peak broadening. Another possible\nexplanation is that a small fraction of products arises from side reactions between Diazo-1-Lixer\nmolecules themselves. Specifically, we suspect that a Büchner ring expansion reaction may have\noccurred, i.e. a carbene of an activated Diazo-1-Lixer molecule inserts into the closely-lying\nbenzene ring of a neighboring Diazo-1-LixerR2.\nTo further demonstrate that the aromatic proton peaks did not disappear, we have provided\n1H-NMR spectra with integral values for protons in the aromatic region, confirming that the\nexpected total integral value (5) is preserved (Table R1 and Fig. R1.1). This result clearly\nindicates that the aromatic proton peaks remain present despite changes in peak shape.\n3. Regarding the suppression of phenyl resonance after 80 minutes: The results of monitoring the\nreaction progress in SI indicate that the reaction proceeds rapidly up to 80 minutes, after which\nit is almost complete and progresses slowly. Consequently, after 80 minutes, most of the Diazo-\n1-LiXer has been consumed, resulting in low intensities of the proton peaks associated with\nDiazo-1-LiXer.\"\nR2. Ma, G et al. Recent advances in transition-metal-catalyzed Büchner reaction of alkynes. Org.\nBiomol. Chem., 21, 5150-5157 (2023)\nTable R1. Integral value of the aromatic region and methyl peak region in 1H-NMR spectra of 0 ~\n200 min reaction mixtures. The integral value of the tetramethylsilane (TMS) peak was fixed to 2.\nAromatic region Methyl region Integral value of\nReaction time Integral value of Integral value of Integral value of tetramethylsilane\n8.10 ~ 7.27 ppm 7.24 ~ 6.90 ppm 4.10 ~ 3.10 ppm (TMS)\n0 min 3.94 0.96 3.14\n20 min 3.63 0.91 3.05\n40 min 4.35 1.08 3.50\n60 min 3.92 0.94 3.26\n80 min 4.97 1.05 4.44\n100 min 4.14 1.01 3.80 2.00\n120 min 3.62 0.87 3.38\n140 min 4.25 0.73 3.82\n160 min 3.83 0.89 3.37\n180 min 3.79 0.73 3.26\n200 min 4.13 0.90 3.70\nFigs. 7–8 in the original SI) and replaced them with new ones shown in Fig. R1.1 in full-range\nincluding integral values of proton peaks (Supplementary Figs. 14–24 in the revised SI).\n9\n[Comment #3] A key but missing piece of characterization is the possible crosslinking between the\nQD ligands and the photoresist (KL5301 in this case). What are the major functional groups in this\nphotoresist? Can we rule out the possibility of reactions between ligands and photoresists? The reaction\nmay not be omitted due to the effective C-H insertion reaction of diazo-based linkers. In PIN, QD films\nlocate on top of and between the “walls” of photoresists. The reaction between QDs and photoresists\n(especially the sidewall part) may complicate the stripping step and affect the patterning quality.\nCharacterizing the reaction between QD ligands and photoresists in the presence of diazo-based\ncrosslinkers will help to clarify this and also provide more guidance on the compatibility of this indirect\npatterning chemistry (PIN) with different types of photoresists.\n[Response] KL5301 is a positive photoresist composed of a diazo photoactive compound,\nelectronic-grade propylene glycol monomethyl ether acetate (PGMEA), and mixed cresol novolak\nresin. As noted by the reviewer, there is a finite chance for crosslinking reactions to occur between\nthe QD ligands and the photoresists patterns - methylene bridges in the novolak resin are sp3 carbons,\nwhich can undergo C-H insertion reactions with carbene. Crosslinking between the QD film and\nthe top surface of PR pattern would not cause a serious issue, as the PR patterns, along with the\nQD film on top, are removed during the lift-off step. On the other hand, crosslinking at the sidewall of\nPR pattern could indeed present a problem, as pointed out by the reviewer. This crosslinking could\ncontribute to the formation of undesirable ear-structures, in addition to the capillary effect we\ndescribed in the original manuscript.\nHowever, recall that we controlled the thickness of the PR patterns to be comparable to the\nthickness of the target QD film, which resulted in the disappearance of the ear-structures (Fig. 2a).\nConsequently, the interaction area between the sidewall and the QD pattern could be minimized.\nThis allowed obtaining QD patterns with LER comparable to the original PR patterns. The LER of\nthe KL5301 PR pattern was 40.8 ± 3.9 nm, while the LER of the red CdSe/ZnSe/ZnS QD patterns,\nprepared using the same PR pattern, was 57.6 ± 4.1 nm. The LER of the DSP-DJ2 PR pattern was\n32.9 ± 1.2 nm and the resulting red CdSe/ZnSe/ZnS QD patterns 43.1 ± 1.8 nm. Overall, we\nconclude that the crosslinking reactions at the sidewall do not critically affect the patterning quality\nin the PIN photopatterning processes.\nWe speculate the marginal crosslinking reaction between Diazo-4-LiXer and pre-formed PR\npatterns can be understood from the hydrophilicity/hydrophobicity of the components. The diazo-\nbased crosslinker (Diazo-4-LiXer) is hydrophobic (as it is readily dissolved in toluene mixed with\nQDs), in contrast to the hydrophilic pre-formed PR patterns, such as KL5301. Consequently, from\na nanoscale interfacial perspective, we anticipate that the hydrophobic Diazo-4-LiXers are less\n10\nlikely to interact with the hydrophilic PR sidewalls and that the extent of crosslinking between the\nQD ligands and the PR is minimal under our processing conditions.\nIn response to this comment, we have included a discussion on the impact of PR-QD\ncrosslinking on ear structures and pattern fidelity in Supplementary Note 2.\nChanges made in Supplementary Information\nSupplementary Note 2. Impact of PR-QD Crosslinking on Ear Structures and Pattern Fidelity\nKL5301 and DSP-DJ2 are positive PRs composed of a diazo photoactive compound,\nelectronic-grade propylene glycol monomethyl ether acetate (PGMEA), and mixed cresol novolak\nresin. Therefore, there may be a finite chance for crosslinking reactions to occur between the QD\nligands and the photoresists patterns - methylene bridges in the novolak resin are sp3 carbons,\nwhich can undergo C-H insertion reactions with carbene. Despite the chance, crosslinking between the\nQD film and the top surface of PR pattern would not cause a serious issue, as the PR patterns, along\nwith the QD film on top, are removed during the lift-off step. On the other hand, crosslinking at the\nsidewall of PR pattern could present a problem. This crosslinking could contribute to the formation\nof undesirable ear-structures, in addition to the capillary effect we described in the manuscript.\nHowever, recall that we controlled the thickness of the PR patterns to be comparable to the thickness\nof the target QD film, which resulted in the disappearance of the ear-structures (Fig. 2b and\nSupplementary Fig. 38-41). Consequently, the interaction area between the sidewall and the QD\npattern could be minimized. This allowed obtaining QD patterns with LER comparable to the\noriginal PR patterns. The LER of the KL5301 PR pattern was 40.8 ± 3.9 nm, while the LER of the\nred CdSe/ZnSe/ZnS QD patterns, prepared using the same PR pattern, was 57.6 ± 4.1 nm. The LER\nof the DSP-DJ2 PR pattern was 32.9 ± 1.2 nm and the resulting red CdSe/ZnSe/ZnS QD patterns\n43.1 ± 1.8 nm. Overall, we conclude that the crosslinking reactions at the sidewall do not critically\naffect the patterning quality in the PIN photopatterning processes.\n11\n[Comment #4] On the choice of photoresists and the applicability of this approach to other photoresists.\nRelated to the discussions in 3), why the authors select KL5301? In conventional photolithographic\npatterning of QDs, other photoresists (e.g., AZ series, in Journal of the Society for Information Display\n26, 121-127 (2018)) were used. What are the selection criteria for the photoresists? Can PIN apply to\nother types of photoresists? Based on the results, KL 5301 may not be the best choice. For example, it\ncannot make templates for thin QD films (e.g., 20 nm, suitable for QLEDs) and require additional dry\netching. The stripping process of this photoresist also requires ultrasonication. The authors may need\nto provide evidence on the applicability of PIN to other photoresists.\n[Response] KL 5301 was originally selected based on the following criteria.\n1) It is a commercially available photoresist that allows us to achieve the thinnest possible thickness\n(70 nm) using an established recipe – thin PR patterns were needed to form QD patterns without\near-structure.\n2) It is known to be thermally stable, ensuring the chemical properties of the photoresist remain\nunchanged during the annealing step required for thermally crosslinking the QD films on top.\n3) It is a positive-tone photoresist, generally considered more suitable for lift-off processes,\nparticularly for metals –though this may not be a critical factor in PIN photopatterning of solution\nprocessed QD films.\nAs long as these criteria are met, other photoresists including the AZ series should, in principle,\nbe applicable to this process. With KL5301, the minimal thickness we could reliably attain was 70\nnm. While this is relatively thin, it was not thin enough to form <20 nm QD films for QLED\napplications, as pointed out by reviewer. Consequently, we had to introduce an additional etching\nstep to reduce the photoresist pattern thickness down to 20 nm. Although this approach seemed to\nwork, reviewers raised concerns about involving an etching process, as it could not only reduce the\nphotoresist pattern thickness (as intended) but also damage the underlying HTL.\nTo address this issue, we utilized a different photoresist (DSP-DJ2 from Dongjin Semichem\nCo. Ltd.) for the revision. DSP-DJ2 successfully formed <20 nm thick PR patterns directly without\ninvolving an etching process. Overall, these features of DSP-DJ2 address the concerns raised by the\nreviewer, making it a more suitable option for PIN patterning of QDs.\nIn addition, although our focus here is on <20 nm QD patterning for EML of EL devices, we\nwould like to note that the PIN strategy is also compatible with thicker PR templates. For example,\nin separate experiments for other applications, we have successfully applied the same PIN process\nusing a photoresist such as KL5315, which can form micrometer-scale thick patterns (Fig. R1.2).\nThis demonstrates that PIN is scalable and applicable to a wide range of template thicknesses, from\n12\nsub-20 nm films to ~1 μm structures, depending on the specific application requirements.\nFig. R1.2. PIN photopatterning of 2.5-μm-thick InP/ZnSeS QD patterns using KL5315 PR. a,\nFluorescence microscopic image of the green-emitting QD patterns. b, Height profile of the green-\nemitting QD patterns.\nRegarding this comment, we discussed the following selection criteria for compatible\nphotoresists in our PIN photopatterning in Supplementary Note 5. We also added the data in\nSupplementary Fig. 45 in Supplementary Information.\nChanges made in Manuscript\n(page 5, line 13 – page 5, line 15) First, sacrificial PR patterns were formed onto a substrate by\nfollowing conventional protocols, using KL5301 (from KemLab Inc.) and DSP-DJ2 (from Dongjin\nSemichem Co., Ltd.), both of which are commercially available positive PRs capable of forming\nthin patterns below 100 nm (the significance of PR pattern thickness is discussed below)51.\n(page 5, line 29 – page 6, line 3) Fig. 1d shows, for example, the ratio of thickness variation\n(referred to as the film thickness retention ratio) before and after soaking KL5301 and DSP-DJ2 PR\nfilms (annealed at different temperatures for 20 min) in a stripping solvent (i.e., acetone). In\nprinciple, the PR films should be completely removed by the stripping process, and, therefore, this\nratio should equal zero. This was, in fact, only true for these PR films annealed at temperatures\nbelow 120 °C.\n(page 12, line 30 – page 13, line 1) In addition, QD patterns with thickness above 2 μm could be\nsuccessfully prepared (Supplementary Fig. 45).\nSupplementary Note 5. Selection Criteria for Compatible Photoresists to PIN Photopatterning\n1. Positive-type PRs are preferred to avoid direct UV exposure of the QD layers during patterning,\nthereby preventing photodegradation of the QDs.\n2. Film thickness control is critical, especially for EL device applications where the target QD\nEML thickness is typically below 20 nm. Photoresists capable of forming thin patterns either\ninherently (e.g., DSP-DJ2 without dilution) or through thinning with appropriate solvents (e.g.,\nKL5301) are acceptable.\n3. Thermal stability is essential, as the annealing process should not alter the chemical solubility\nof the PR at the thermolysis temperature of the diazo crosslinker (Diazo-4-LiXer). This ensures\nthat the pattern integrity is maintained during post-processing.\nSupplementary Fig. 45. PIN photopatterning of 2.5-μm-thick InP/ZnSeS QD patterns using\nKL5315 PR. a, Fluorescence microscopic image of the green-emitting QD patterns. b, Height\nprofile of the green-emitting QD patterns.\n14\n[Comment #5] Fig. 1c compares the quality of QD patterns with or w/o crosslinking. What was the\nstripping solvent used here? Was it acetone? It is a little surprising to see the poor adhesion of QD\nlayers after acetone treatment. For comparison, solid state ligand exchange or solvent treatment in\nacetone or alcohols are widely used to change the surface chemistry or ligand density of QD films, for\napplications in solar cells (as shown by Prof. Sargent and others). QD films remain mostly intact after\nbeing immersed in those solvents, because they are “nonsolvents” for QDs. Can the authors explain\nthe poor adhesion of QD films in this case?\n[Response] The stripping solvent used was acetone, which is indeed a nonsolvent for QDs, as the\nreviewer correctly pointed out. The poor adhesion of the QD layers after acetone treatment is\nattributed to the ultrasonication process, which was necessary to effectively remove the photoresist\npatterns. (Ultrasonication of substrate for 60 sec was needed to effectively remove the PR patterns.\nOtherwise, both the QD layer but also the PR patterns remained intact, preventing the formation of\nintended QD patterns). However, QD patterns that were chemically crosslinked using diazo-4-\nLiXer exhibited excellent resistance to the stripping process. Therefore, crosslinking remains\nessential to maintain the integrity of the QD patterns during multilayer processing.\n15\n[Comment #6] On the patterning fidelity of QDs, a key advantage of PIN is the ultra-low line edge roughness of QD patterns, which is several times or one order of magnitude smaller than those for direct optical patterning methods. The low line edge roughness may follow from that of the patterned photoresists. However, based on Suppl. Fig. 27, the line edge roughness of the photoresist (KL 5301) was larger than 10 nm. The patterned QDs derived from the photoresist templates show much improved line edge roughness (about 3.7 nm). As the patterning fidelity is a key advantage for PIN, the authors may need to double check and explain this observation.\n[Response] We acknowledge that an error occurred in our previous calculation of LER metrics,\nand we greatly appreciate this insightful comment regarding the fidelity of QD patterns obtained\nthrough PIN photopatterning, which we consider as a key advantage of this method.\nTo address this comment, we revisited our data and found that some of the LER measurements\nwere derived from AFM images collected at larger scales (e.g., 30 μm x 30 μm images with 512\nline scans, giving a single AFM image pixel of ~60 nm). Such data should not have been used to\nassess LER values in the range of few tens of nm. Recognizing this artifact in our data collection,\nwe repeated the experiments.\nIn the revised experiments, QD patterns were formed using both KL5301 and DSP-DJ2 PRs.\nThis time, all LER data were collected from AFM images captured at smaller scales (i.e., 5 μm x 5\nμm images with 1024-line scans, yielding a AFM image pixel size ~5 nm). To further ensure\nprecision in structural comparisons, we prepared additional PR test patterns alongside the PR\npatterns used for PIN patterning of QDs. These patterns were processed simultaneously under\nidentical conditions, following the same protocol, to thoroughly assess and compare the fidelity of\nthe PR and resulting QD patterns.\nThe corrected data indicates that the LER of QD patterns formed through the PIN process\nranges from 40 to 60 nm (Table R2), which is indeed higher than the LER of the PR templates (40.8\n± 3.9 nm for KL5301 and 32.9 ± 1.2 nm for DSP-DJ2). However, it is crucial to note that even with\nthis revised LER value, the PIN photopatterning method still offers a more than fourfold\nimprovement in fidelity compared to direct optical patterning techniques. We have updated the\nmanuscript and the supplementary information accordingly to reflect this correction and provide\ndetailed data.\nIn addition to LER, we also compared line width roughness (LWR). LWR were defined in two\nways: vertical LWR (v-LWR), which presents deviations of the line edges in the upper, middle, and\nlower parts of the pattern, and longitudinal LWR (l-LWR), which denotes variations in the pattern\nwidth along the longitudinal direction of the patterns. We also note that while the LWR values in\n16\nthe original manuscript was defined as the standard deviation of the data, we adopted the standard\nused in PR community, defining v-LWR and l-LWR as the 3 sigma (3σ) value of the deviations,\nwhich statistically indicates the range within which 99.7% of the measured deviations are expected\nto fall, providing a more comprehensive and statistically significant evaluation of the patterning\nfidelity and roughness.\nWe confirmed that the v-LWR and l-LWR of patterns obtained through PIN photopatterning\nwere smaller than those achieved through direct photopatterning. Notably, the v-LWR and l-LWR\nof the PIN-patterned structures using DSP-DJ2 were both less than 10% of the line width,\ndemonstrating exceptional pattern fidelity which indicates that the fabricated structures maintain\nhighly uniform and precise line dimensions, meeting the stringent quality requirements for\nadvanced display and semiconductor applications. This result underscores the superior precision\nand reliability of PIN photopatterning in achieving high-fidelity patterns compared to previous\nresultsR3-R11.\nTable R2. Comparison of QD patterns (width, 2 μm; spacing, 2 μm; thickness, 20 nm) formed\nby direct and PIN photopatterning method in this study. The values in the parentheses present\nthe ratio of each fidelity factor relative to the pattern width.\nPatterning Activation LER l-LWR v-LER\nPR QDs\nmethod source\nnm nm nm\nDirect UV 227.0 ± 4.1 343.6 ± 3.2 455.0 ± 17.2\n- Red CdSe\nphotopatterning (365 nm) (9.5%) (14.5%) (19.1%)\nPIN Heat 57.6 ± 4.1 84.3 ± 8.2 261.2 ± 9.0\nKL5301 Red CdSe\nphotopatterning (110 ℃) (2.9%) (4.2%) (13.1%)\nPIN Heat 43.1 ± 1.8 62.3 ± 4.4 139.3 ± 3.8\nDSP-DJ2 Red CdSe\nphotopatterning (110 ℃) (2.5%) (3.6%) (8.0%)\nPIN Heat 40.0 ± 2.5 55.8 ± 3.2 121.3 ± 5.0\nDSP-DJ2 Green InP\nphotopatterning (110 ℃) (2.3%) (3.2%) (7.0%)\nReferences\nR3. Maeng, S. et al. Direct photocatalytic patterning of colloidal emissive nanomaterials. Sci.\nAdv. 9, eadi6950 (2023).\nR4. Lee, J. et al. Direct optical lithography of colloidal inp-based quantum dots with ligand pair\ntreatment. ACS Energy Lett. 8, 4210-4217 (2023).\nR5. Yang, J. et al. High-resolution patterning of colloidal quantum dots via non-destructive,\nlight-driven ligand crosslinking. Nat. Commun. 11, 2874 (2020).\nR6. Fu, Z. et al. Direct photo-patterning of efficient and stable quantum dot light-emitting diodes\nvia light-triggered, carbocation-enabled ligand stripping. Nano Lett. 23, 2000-2008 (2023).\nsurface. Nat. Nanotechnol. 17, 952-958 (2022).\nR8. Yang, J. et al. Nondestructive photopatterning of heavy-metal-free quantum dots. Adv. Mater.\n34, 2205504 (2022).\nR9. Cho, H. et al. Direct optical patterning of quantum dot light-emitting diodes via in situ ligand\nexchange. Adv. Mater. 32, 2003805 (2020).\nR10. Lee, J. et al. Photocleavable ligand-induced direct photolithography of InP-based quantum\ndots. ACS Energy Lett. 10, 94-101 (2025).\nR11. Xiao, P. et al. Ligand-engineered direct optical lithography of nanocrystals with industrially\ncompatible solvents. ACS Nano 19, 14509-14520 (2025).\nIn response to this comment, we have updated the manuscript and the supplementary\ninformation accordingly to reflect this correction and provide detailed data.\nChanges made in Manuscript\n(page 9, line 27 – page 10, line 7) The quantitative features of the resulting patterns, such as line-\nedge roughness (LER), vertical line-width roughness (v-LWR, defined as the deviations of the line\nedges in the top, middle, and bottom of the pattern), and longitudinal line-width roughness (l-LWR,\nwhich denotes the variations in the pattern width along the longitudinal direction of the patterns),\nwere characterized (Fig. 2c-d)52. The PIN photopatterning method produced QD patterns with a\nLER of 32.9 ± 1.2 nm, l-LWR of 48.0 ± 0.9 nm, and v-LWR of 120.0 ± 3.2 nm. Here, the values\nare the 3 sigma (3σ) value of the deviations, following the standard used in PR community which\nstatistically indicates the range within which 99.7% of the measured deviations are expected to fall.\nImportantly, all these parameters were smaller than those achieved with the direct photopatterning\nprocess, where the LER was 43.1 ± 1.8 nm, l-LWR of 62.3 ± 4.4 nm, and v-LWR of 139.3 ± 3.8\nnm.\nRef. #54. Levinson, H. J. Principles of lithography Ch 3 (SPIE Press, 2010)\n(page 21, line 3 – page 21, line 6) For structural parameters analysis of the patterns including LER,\nl-LWR, and v-LWR, data were collected from 5 μm x 5 μm AFM images that were specifically\ncaptured with 1024-line scans, yielding an AFM image pixel size ~5 nm.\nSupplementary Fig. 36. Information of DSP-DJ2 PR pattern. a, AFM images of 16-nm thick\nDSP-DJ2 PR patterns. These patterns were targeted to exhibit dimensions of 2 μm in width and 2\nμm in spacing. b, The height profile of the patterns in a). c, Averaged line edge roughness of the PR\nline. Data present averages from more than five separately prepared samples, with the data values\ndetermined as three times the standard deviation (3σ), and the error bar indicating standard error.\nSupplementary Fig. 37. Information of KL5301 PR pattern. a, AFM images of 67-nm thick PR\npatterns. These patterns were targeted to exhibit dimensions of 3 μm in width and 2 μm in spacing.\nb, The height profile of the patterns in a). c, Averaged line edge roughness of the PR line. Data\npresent averages from more than five separately prepared samples, with the data values determined\nas three times the standard deviation (3σ), and the error bar indicating standard error.\nspacing, 2 μm; thickness, 24 nm) from the DSP-DJ2 PR-based PIN photopatterning and the\ndirect photopatterning. a, AFM images of 24-nm-thick InP/ZnSeS QD patterns obtained from the\nPIN photopatterning and the direct photopatterning. These patterns were targeted to exhibit\ndimensions of 2 μm in width. b, Comparison of the height profiles of the patterns in a). c, Averaged\nline edge roughness (left), longitudinal line width roughness (middle), and vertical line width\nroughness (right) of the QD line. Data present averages from more than five separately prepared\nsamples, with the data values determined as three times the standard deviation (3σ), and the\nerror bars indicating standard errors.\nμm; spacing, 2.5 μm; thickness, 70 nm) from the KL5301 PR-based PIN photopatterning and\nthe direct photopatterning. a, AFM images of 20-nm thick CdSe/ZnSe/ZnS QD patterns obtained\nfrom the PIN photopatterning and the direct photopatterning. These patterns were targeted to exhibit\ndimensions of 2.5 μm in width. b, Comparison of the height profiles of the patterns in a). c,\nAveraged line edge roughness (left), longitudinal line width roughness (middle), and vertical line\nwidth roughness (right) of the QD line. Data present averages from more than five separately\nprepared samples, with the data values determined as three times the standard deviation (3σ), and\nthe error bars indicating standard errors.\nSupplementary Fig. 40. Comparison between the pattern fidelity of QD patterns (width, 2.5\nμm; spacing, 1.5 μm; thickness, 20 nm) from the KL5301 PR-based PIN photopatterning and\nthe direct photopatterning. a, AFM images of 20-nm thick CdSe/ZnSe/ZnS QD patterns obtained\nfrom the PIN photopatterning and the direct photopatterning. These patterns were targeted to exhibit\ndimensions of 2.5 μm in width. b, Comparison of the height profiles of the patterns in a). c,\nAveraged line edge roughness (left), longitudinal line width roughness (middle), and vertical line\nwidth roughness (right) of the QD line. Data present averages from more than five separately\nprepared samples, with the data values determined as three times the standard deviation (3σ), and\nthe error bars indicating standard errors.\n21\n[Comment #7] Additionally, many photoresists have non-rectangular cross-section profiles. These\nfeature is related to the different degree of photochemistry along the depth of photoresists and thus\nopposite for positive and negative photoresists. These features, although beneficial for the subsequent\nlift-off and etching processes in conventional microfabs, may behave as intrinsic limits for the\nlinewidth variation of patterned QD films. KL 5300 series seem to have such non-rectangular cross-\nsection as well (http://www.nm-tech.co.kr/?act=shop.goods_view&GS=26&GC=GD0100). Have the\nauthors observe such effects on the QD patterns? The linewidth variation (270 nm) seems quite large\ncompared to the line edge roughness, probably due to this reason?\n[Response] We thank the reviewer for this insightful observation. The KL5300 series, including\nKL5301 used in our study, are positive-tone photoresists that indeed produce patterns with an\novercut cross-sectional profile. We confirmed this feature experimentally for KL5301, as shown in\nSupplementary Fig. 37. However, compared to conventional photoresists that form micrometer-\nscale thick patterns, both KL5301 and DSP-DJ2 used in our work yield photoresist patterns with\nthicknesses on the order of tens of nanometers. As such, the extent of the overcut profile is\nsignificantly reduced and is less likely to contribute as a dominant factor to linewidth variation in\nour case.\nAs noted in our response to Comment #6, we revised our approach to evaluating line edge and\nwidth roughness by adopting the standard definitions commonly used in the photoresist and\nlithography communities. Specifically, we now define vertical line width roughness (v-LWR) and\nlateral line width roughness (l-LWR) using the 3σ standard deviation, which captures 99.7% of\ndeviations and thus provides a more statistically meaningful representation of patterning fidelity.\nWith this update, the LWV originally reported in our manuscript now corresponds to v-LWR.\nFor example, the CdSe/ZnSe/ZnS QD pattern fabricated using KL5301 (2 μm width, 2 μm spacing,\n20 nm thickness) exhibits a v-LWR of 261.2 nm and an LER of 57.6 nm. Likewise, the same QDs\npatterned with DSP-DJ2 show a v-LWR of 139.3 nm and an LER of 43.1 nm. As pointed out by the\nreviewer, the v-LWR values are consistently larger than the LER values. However, there should be\nno theoretical correlation why the two values should be comparable. We also note that, from a\ntheoretical standpoint, LER is more directly comparable to l-LWR than v-LWR. Assuming that the\nroughness on both edges of a line is uncorrelated and statistically similar, l-LWR is expected to be\n√2 times the LER. Our measured values reasonably follow this expected relationship, supporting\nthe internal consistency of our data and suggesting that the observed LWV (corresponding to v-\nLWR in the revised version) arises primarily from edge fluctuations rather than overcut geometry.\nChanges made in Manuscript\n(page 10, line 1 – page 10, line 4) The PIN photopatterning method produced QD patterns with a\nLER of 32.9 ± 1.2 nm, l-LWR of 48.0 ± 0.9 nm, and v-LWR of 120.0 ± 3.2 nm. Here, the values\nare the 3 sigma (3σ) value of the deviations, following the standard used in PR community which\nstatistically indicates the range within which 99.7% of the measured deviations are expected to fall.\n23\n[Comment #8] Fig. 2c and Suppl. Fig. 28-30 compares the patterning fidelity when using thermal or\nphotoreactions of diazo-4-LiXer. It is convincing that the indirect PIN approach using thermal\nreactions and photoresist show improved fidelity. However, one may argue the validity of using the\ndirect optical patterning with diazo-4-LiXer as the reference. As shown in Suppl. Fig. 26, this carbene-\nbased cross-linker has low efficiency in photochemical reactions. Even a large UV dose (~5 J/cm2)\ncan only convert a small amount of diazo-4-LiXer into carbenes. Consequently, the photopatterned QD\nfilms would not be fully cross-linked. It would be better if the authors can provide additional\ndiscussions in the text.\n[Response] We greatly appreciate your valuable guidance. There may be a misunderstanding\nregarding our data. Our objective was to present a comparative analysis of the fidelity of QD\npatterns produced through both PIN photopatterning and direct optical patterning utilizing the same\ncrosslinker of diazo-4-LiXer. To ensure a fair comparison, we optimized the crosslinking conditions\nsuch that both photochemical and thermal processes yielded equivalent film thickness retention\nr thickness retention\nratios above 0.9, which is a proof that the film is sufficiently crosslinked. Specifically, a UV dose\nof up to 5 J/cm² (i.e. photocrosslinking) was necessary to achieve this retention ratio, whereas gentle\nannealing at 110°C for 20 min (i.e. thermal crosslinking) resulted in an equivalent retention ratio.\nBy adopting these respective conditions, we ensured that the pattern fidelity comparison was\nconducted under comparable film stabilization conditions, validating the approach.\nIn response to this comment, we have revised the manuscript to address this comment.\nChanges made in Manuscript\n(page 9, line 19 – page 9, line 21) Notably, the UV exposure condition yielded a film thickness\nretention ratio above 0.9, indicating that the film was sufficiently crosslinked and that the processing\ncondition was equivalent to the thermal process.\n24\n[Comment #9] Fig. 2c provides the LER, linewidth variation, and surface roughness of ~70 nm-thick\nfilms. Could the authors also provide these parameters for ~20 nm-thick patterns, which were used in\nmaking QLEDs?\n[Response] We appreciate the comment. The parameters for the ~20 nm-thick patterns were\noriginally provided in the Supplementary Information; however, as mentioned above in this\nresponse letter to the earlier comment, we have updated our approach to avoid the additional RIE\nstep previously required to achieve sub-20 nm thickness. Specifically, we newly prepared ~20 nm-\nthick QD patterns using DSP-DJ2 photoresist, which does not require post-patterning etching.\nThe corresponding patterning results have now been included in the main manuscript as\nupdated data in Fig. 2, replacing the earlier results based on 70 nm-thick films.\nChanges made in Manuscript\nFig. 2. Fidelity of QD patterns produced using PIN photopatterning and direct\nphotopatterning. a, AFM images of 16-nm-thick DSP-DJ2 PR pattern and 16-nm-thick\nComparison of height profiles of the patterns in a). c, Schematic illustration of a line QD pattern\nwith physical parameters labeled, which include LER, l-LWR, and v-LWR. d, Averaged values of\nLER, l-LWR, and v-LWR. The data present averages from more than five separately prepared\nsamples, with the data values determined as three times the standard deviation (3σ), and the error\nbars indicating standard errors. e, Summary comparing the LER values reported in the literature\nwith the values obtained in this study22,27,28,31-34,38,41. The results from this study are presented by\nthe four blue open-circles. From top to bottom, they correspond to: (1) Supplementary Fig. 38,\n(2) Fig. 2a–b and 2e, (3) Supplementary Fig. 40, and (4) Supplementary Fig. 39, respectively.\n26\n[Comment #10] For the full colored pattern (Fig. 3f), the red and green dots look uniform but there\nare significant defects/irregularity for the blue dots. Was it related to the larger amount of crosslinkers\nneeded for blue QDs?\n[Response] We appreciate the observation. It is correct that a relatively larger amount of crosslinker\nwas required for blue QDs compared to red and green QDs. However, this adjustment was made to\nachieve a similar degree of crosslinking across all QD colors, so we do not believe the higher\ncrosslinker content itself directly caused the observed defects or irregularities in the blue pattern.\nWe suspect that the perceived defects/irregularity could be instead due to the lower optical\nabsorption of blue QDs relative to red and green QDs under the same UV exposure conditions.\nSince the full-color pattern image in Fig. 3f was obtained using a uniform UV exposure across all\nRGB layers, the blue QDs, having lower absorption in the UV region, emitted less light. This lower\nbrightness likely resulted in a dimmer and less well-defined appearance in the photograph, giving\nthe impression of non-uniformity. In fact, the AFM image in Fig. 3g shows that the structural fidelity\nof the blue QD pattern is comparable to that of the red and green patterns, supporting our conclusion\nthat the difference is mainly optical rather than morphological.\n27\n[Comment #11] On the PLQY properties, when comparing diazo- and azide-based crosslinkers,\nthe authors mentioned “Third, the carbene in the compound exists in a secondary form and therefore,\nundesired surface reactions involving the reactive carbene intermediate that occur directly on the QD\nsurface can be sterically suppressed”, and also similar description in the paragraph on the PLQY\nproperties. What does this mean? Can the authors provide more specific discussion?\n[Response] We appreciate the comment. One of the main possible mechanisms of luminescence\ndegradation of QDs during the given crosslinking reaction is the direct interaction of UV-generated\ncarbene with the surface of the inorganic QD core. To suppress this effect, we previously introduced\nbulky isopropyl groups adjacent to the nitrene-generating azide group in an azide-based\ncrosslinkerR12. It was confirmed that the attaching bulky side groups next to the azide group\nsterically suppressed nitrene from directly participating in surface reactions on the inorganic QD\ncore. This led to better preservation of the luminescent characteristics of QDs, including their PLQY,\nduring the nitrene-based crosslinking reaction.\nSimilarly, the sentence in the original manuscript was intended to explain that direct\ninteraction between the carbene and the inorganic QD core surface can be suppressed due to the\nsteric environment of the carbene. Specifically, the carbene in our system, located between the\nphenyl and ester groups, exists in a secondary form. We speculate that the larger steric hindrance of\nthis secondary carbene reduces the likelihood of its penetration through the dense ligand shell to\nreach the inorganic QD core surface. This reduced accessibility may contribute to minimizing\nundesired surface reactions, ultimately helping to maintain the luminescent properties of QDs.\nReferences\nR12. Yang, J. et al. Nondestructive photopatterning of heavy-metal-free quantum dots. Adv.\nMater. 34, 2205504 (2022).\nRegarding this comment, we modified the sentences.\nChanges made in Manuscript\n(page 8, line 21 – page 8, line 24) Third, the carbene intermediate in this compound, which has a\nterminal phenyl group and an ester linkage to the core, exists in a secondary form. This steric\nenvironment likely reduces the accessibility of the reactive carbene to the inorganic QD surface,\nthereby suppressing undesired surface reactions and helping to preserve the luminescent properties\nof QDs30.\nMater. 34, 2205504 (2022).\n29\n[Comment #12] On the applicability of PIN in fabricating pixelated QLEDs. An important\nshortcoming of this method is that it needs some patterning steps hard to be compatible with QLED\nfabrication procedures. These include the dry etching of photoresists to decrease the height of\ntemplates (may deteriorate the underlying layers, ZnO in this device geometry and more severely if\nusing the organic transport layer below QDs), ultrasonication during the lift-off step (may affect the\nunderlying layers). According to the Methods, the QLED device was made without involving the\nphotoresist layers and no pixelated QLEDs were made. The results shown in Fig. 4 indicate that the\nthermal crosslinking reaction does not affect the performance of QLEDs made from red, CdSe-based\nQDs. However, the effects of the key steps in making the patterns were not explored. This may be a\nmajor concern for the applicability of PIN or similar indirect patterning methods in building high-\nfidelity, high-performance QLED displays.\n[Response] We sincerely appreciate the insightful comment and admit that we have previously\noverlooked the potential negative impact of including an etching process while forming PR patterns\non QLED performance. Specifically, we recognize that the etching process used to reduce the height\nof PR templates could degrade the underlying ETL or HTL. Additionally, the ultrasonication step\nduring lift-off may also pose risks to these layers.\nTo mitigate these concerns, we explored alternative methods for forming ~20 nm thick PR\npatterns without involving an etching process. Specifically, we tested two approaches: (i) diluting\nthe KL5301 PR solution with PGMEA (the solvent of the PR solution) or AZ1500 thinner, and (ii)\nutilizing an alternative commercial PR, DSP-DJ2 from Dongjin Semichem, yielding ~20 nm PR\nfilm without an additional dilution step. While both approaches resulted in PR and QD patterns with\ncomparable structural characteristics, the results obtained using DSP-DJ2 were more reliable and\nreproducible. The new data in the revised manuscript is thus based on PIN patterning using DSP-\nDJ2. Using a 20 nm thick DSP-DJ2 pattern allowed us to entirely eliminate the etching step, thereby\npreventing potential damage to the underlying HTL or ETL layers.\nFurthermore, to verify the impact of the PR processing steps (coating, development, and\nstripping) on device performance, we characterized the QLED devices that were fabricated,\nincluding the complete PR process (Fig. R1.3). Importantly, we observed no significant degradation\nin device performance, confirming that the concerns raised by the reviewer regarding these key\nprocessing steps do not present major limitations for the applicability of PIN-based patterning in\nQLED fabrication. The data in Fig. R1.3 is included in the new Fig. 4 in the revised manuscript.\ndevices; Device 1 with pristine red-emitting CdSe/ZnSe/ZnS QD layer, Device 2 with the same red-\nemitting CdSe/ZnSe/ZnS QD layer crosslinked using 5 wt% Diazo-4-LiXer, and Device 3 with the\nsame red-emitting CdSe/ZnSe/ZnS QD layer crosslinked using 5 wt% that underwent the entire PIN\nphotopatterning process (including PR deposition, development, and stripping steps).\nRegarding the absence of fully pixelated QLEDs in this study, we acknowledge that while our\nmethod successfully enables the patterning of the QD emissive layer, achieving pixelated QLEDs\nrequires additional patterning of the ETL, HTL, and the top electrode. Without having patterned\nETL, HTL, and top electrodes, the resulting device cannot avoid significant leakage current and\nelectrical crosstalk, which could degrade the device performance. Despite this issue, we have\nincluded an image in Fig. 4h obtained from a device based on a patterned QD EML, while\nmaintaining common HTL, ETL, and electrode layers. Due to the expected high leakage current in\nthese structures, we believe that a detailed performance analysis of fully pixelated QLEDs without\nfully patterned ETL, HTL, and top electrode is not meaningful at this stage.\nWe note that the data in Fig. 4 is obtained from a device having patterned EMLs, but the size\nof the pattern was the same as that of the top electrode (1.4 mm by 1.4 mm). Therefore, despite the\nuse of non-patterned ETL and HTL, the leakage issue was not an issue in this case. We definitely\nagree that further studies should comprehensively explore the patterning of all functional layers,\nwhich we have initiated exploring into.\nChanges made in Manuscript\n(page 11, line 15 – page 12, line 9) We note the critical importance of precise control over the\nthickness of the pre-formed PR patterns to achieve high-fidelity QD patterns from PIN\nphotopatterning process. In particular, the thickness of the pre-formed PR patterns should be\ncomparable to that of the desired QD patterns. The results presented in Fig. 2a–d were obtained\n31\nusing 16-nm-thick PR patterns, which matches well with the target thickness of the QD patterns (16\nnm) considering their application as the emissive layer in EL devices. Here, this thickness was\nobtained either by using a commercial PR specifically designed for producing such ultrathin\npatterns (e.g., DSP-DJ2), or even by reactive-ion-etching thicker PR patterns (70 nm thick KL5301)\nto the desired thickness. When thicker PR patterns (e.g., 70 nm patterns) were directly used instead,\nundesirable ear-structures were formed at the edge of the patterns owing to the capillary effect or\nundesired reactions crosslinking involving the photoactive compound in PR with QDs\n(Supplementary Note 2 and Supplementary Fig. 41).\n(page 16, line 3 – page 16, line 19) The testbed device included a CdSe/ZnSe/ZnS QD layer as the\nemissive layer, a zinc magnesium oxide nanoparticle (ZnMgO NP) layer as the electron transport\nlayer (ETL), and a 4,4-bis(N-carbazolyl)-1,1-biphenyl (CBP) layer as the hole transport layer (HTL)\n(Fig. 4d). The energy band diagram of the fabricated QD-LED is presented in Fig. 4e. For\ncomparative analysis, three types of devices were fabricated: Device 1 with pristine red-emitting\nCdSe/ZnSe/ZnS QD layer (Pristine), Device 2 with the same red-emitting QD layer crosslinked\nusing 5 wt% Diazo-4-LiXer (Crosslinked), and Device 3 with the same red-emitting QD layer\ncrosslinked using 5 wt% Diazo-4-LiXer that underwent the entire PIN photopatterning process\n(including PR deposition, development, and stripping steps) (PIN photopatterned). It was found that\nthe emission spectrum of Device 3 exhibited no difference compared to that of a reference device,\ni.e. Device 1, even after the EML underwent the entire PIN patterning process (Fig. 4f). The current\ndensity (J)-voltage (V)-luminance (L) profiles of these three devices (Fig. 4g), as well as the external\nquantum efficiency (EQE)-J profiles (Fig. 4h), were comparable. Likewise, crosslinking green and\nblue QDs did not degrade their EL characteristics (Supplementary Fig. 47). Overall, PIN\nphotopatterning based on low-temperature-activated ligand crosslinking reaction of Diazo-4-LiXer\ndid not degrade the electrical and optoelectronic properties of the QD layers. Thus, the entire PIN\nphotopatterning process is non-destructive.\n- Regarding the pixelated device, we did add an image obtained from a device based on a\npatterned QD EML, while maintaining common HTL, ETL, and electrode layers. However, we\ndid not characterize the performance of these devices. In addition, we have specifically added\nthe following comment to the Methods section.\n(page 21, line 25 – page 21, line 28) Note that the size of the EML pattern for Device 3 was\nequivalent to the size of the overlapping area between the top and bottom electrodes (1.4 mm by\n32\n1.4 mm), and therefore, the electrical leakage issue was not an issue, despite the use of patterned\nEML between non-patterned HTL and ETL.\nThe new data is given as\nFig. 4. Luminescence characteristics of crosslinked QD films. a, PLQY of the crosslinked QD\nfilm (relative to that of the pristine QD films) plotted as a function of the film thickness retention\nratio for different QDs with different Diazo-4-LiXer loadings. The numbers in the figure indicate\nthe weight percentage (wt%) of Diazo-4-LiXer relative to those of the respective QDs. The inset\ndata are the PL spectra of pristine (dashed) and crosslinked (solid) QD films. b, Transient PL decay\n33\nprofiles of pristine and crosslinked R-, G-, and B-QD films. The R- and G-QD films were\ncrosslinked using 5 wt% Diazo-4-LiXer, and the B-QD films were crosslinked using 20 wt% Diazo-\n4-LiXer. c, Comparison of the PLQYs of QD films at different stages of the PIN photopatterning\nprocess, including that post thermal crosslinking at 110 °C and that post the PR stripping process.\nThe data are normalized against the PLQYs of the respective pristine QD films. d, Schematic\nillustration of the device structure, and e, energy band diagram of the layers incorporated in the\npristine/crosslinked R-QD EL devices. f, EL spectra, g, J-V-L characteristics, and h, EQE-J\ncharacteristics of three different devices; Device 1 with pristine red-emitting CdSe/ZnSe/ZnS QD\nlayer, Device 2 with the same red-emitting CdSe/ZnSe/ZnS QD layer crosslinked using 5 wt% Diazo-4-LiXer, and Device 3 with the same red-emitting CdSe/ZnSe/ZnS QD layer crosslinked using 5 wt% and underwent the entire PIN photopatterning process (including PR deposition, development, and stripping steps). The inset in h shows an EL image of a device with pixelated EML. Scale bar, 200 μm.\n34\n[Comment #13] Related to 12), Suppl. Table S2 compares PIN with recently reported direct optical\npatterning methods. PIN shows smaller line edge roughness and comparable preservation of PLQYs\n(compared to the work by some of the same authors and other groups). However, it is very important\nto include the status of QLED performance (at least EQEs) of these patterning approach. Compared to\nprevious direct patterning methods, the EQEs reported here is not high and whether PIN (at least when\nused with KL 5301) is suitable for building pixelated QLED devices remains unclear.\n[Response] We appreciate the valuable comment regarding the QLED. In response, we have further\noptimized the device performance and achieved an EQE of 16.6% for red QLEDs (which was 14.8%\nin the original manuscript). This may be considered to be lower than the record red QD devices\nbased on direct patterning methodsR13, R14, R15. However, considering that the main focus of this\npaper is to introduce a novel patterning process of QDs, rather than showing a strategy to fabricate\ndevices with record performance, we consider this value to be appropriate as for now. Importantly,\nthis result is not obtained from a device fabricated merely comprising a crosslinked QD EML, but\nrather from a fully processed device that has undergone the complete PR patterning/removal steps,\ni.e. PIN photopatterning. We believe this is a meaningful result, as it demonstrates that our approach\nmaintains high performance even after the full patterning process.\nIt is also worth noting that using specialized HTL/ETL structures instead of standard transport\nlayers could further enhance device performance. However, the primary focus of this study is on\nthe fabrication process rather than achieving record-breaking efficiency. While we did not\nspecifically optimize materials to push for the highest possible EQE, our results confirm that PIN\ncan produce high-quality QLEDs using commonly used QDs and HTL/ETL materials without\nadditional performance-enhancing engineering strategies. Additionally, as shown in our\nsupplementary results, we have successfully fabricated green and blue QLEDs as well. While the\nabsolute EQE values of these devices are lower than that of the red QLEDs, our results demonstrate\nthat undergoing the crosslinking and PR processes does not lead to a significant deterioration in\ndevice performance. These results support our claim that PIN-based patterning is a viable and\nscalable method for fabricating pixelated QLED displays.\nReferences\nR13. Fu, Z. et al. Direct photo-patterning of efficient and stable quantum dot light-emitting diodes\nvia light-triggered, carbocation-enabled ligand stripping. Nano Lett. 23, 2000-2008 (2023).\nR14. Hahm, D. et al. Direct patterning of colloidal quantum dots with adaptable dual-ligand\nsurface. Nat. Nanotechnol. 17, 952-958 (2022).\nR15. Xiao, P. et al. Ligand-engineered direct optical lithography of nanocrystals with industrially\ncompatible solvents. ACS Nano (2025).\nRegarding this comment, we have included EQE values in the table. We have also updated the\nelectroluminescence characteristics data in Fig. 4, as explained above to Comment #12.\nChanges made in Manuscript\nSupplementary Table 2. Comparison of QD patterns formed using various functional groups.\nMinimum\nLER l-LWR v-LWR PLQY\nPatterning Activation pattern Maximum\n(basis) (basis) (basis) changes of Ref.\nmethod source width EQE\nQDs\nnm nm nm µm\n~3%\ndecrease\n(green CdSe)\n~0%\nUV\ndecrease ~2.2%\nDirect photo- (275 nm 220 600\nThiol-ene N/A 1 (green InP) (green S3\npatterning or (3σ) (3σ)\nCsPbBr )\n365 nm) 3\n~5%\nincrease\n(green\nCsPbBr\n2-(4-\nmethoxystyryl)-\n4,6- ~34%\n~0.5%\nDirect photo- bis(trichlorometh UV 250 decrease\nN/A N/A 1 (green S4\npatterning yl)-1,3,5-triazine (365 nm) (N/A) (PLQY of red\nInP) (MBT), InP)\n(Photo acid\ngenerator)\n~1%\n14.6%\nDirect photo- UV 420 decrease\nAzide N/A N/A 2 (red S5\npatterning (254 nm) (3σ) (PLQY of red\nCdSe) CdSe)\n~10%\ndecrease\n19.1%\n(PLQY of red\n(red\nInP) CdZnSe)\nTriphenylmethyl\n~12%\nchloride 17.5%\nDirect photo- UV 100 decrease\n(TPCl), N/A N/A 4 (green S6\npatterning (254 nm) (N/A) (PLQY of\nCdZnSe\ngreen InP)\n12.0%\n~31%\n(blue\ndecrease\nCdZnSe)\n(PLQY of\nblue ZnSe)\n36\n~2%\n20.0%\nDirect photo- UV 222 297 decrease\nBenzophenenone N/A 0.8 (red S7\npatterning (365 nm) (3σ) (3σ) (PLQY of\ngreen InP)\n~2%\n8.3%\nDirect photo- UV 150 2100 decrease\nAzide N/A 1 (green S8\npatterning (254 nm) (3σ) (3σ) (PLQY of\ngreen InP)\n2-(4-\nmethoxystyryl)-\n4,6- ~25%\n3.6%\nDirect photo- bis(trichlorometh UV 50 decrease\nN/A N/A 1.5 (green S9\npatterning yl)-1,3,5-triazine (365 nm) (N/A) (PLQY of red\nCdSe) CdSe)\n(Photo acid\ngenerator)\n~25%\nDirect photo- Ortho- UV 130 decrease\nN/A N/A 2 N/A S10\npatterning nitrobenzyl ester (365 nm) (N/A) (PLQY of\ngreen InP)\n~3% decrease\n22.0%\n(PLQY of red\n(red\nCdSe) CdSe)\n~3% decrease\n14.4%\nDirect photo- Methacrylate UV 200 (PLQY of\nN/A N/A 1 (green S11\npatterning (MA) (365 nm) (N/A) green CdSe)\nCdSe)\n~17%\n11.4%\ndecrease\n(blue\n(PLQY of\nCdSe)\nblue ZnSeTe)\n~2%\ndecrease\n(PLQY of\nred CdSe)\n~1%\ndecrease 16.6%\nPIN photo- Heat 40.0 55.8 121.3 This\nDiazo 1 (PLQY of (red\npatterning (110 °C) (3σ) (3σ) (3σ) work\ngreen InP) CdSe)\n~7%\ndecrease\n(PLQY of\nblue\nZnSeTe)\nRef. #S10. Lee, J. et al. Photocleavable ligand-induced direct photolithography of InP-based\nquantum dots. ACS Energy Lett. 10, 94-101 (2025).\nRef. #S11. Xiao, P. et al. Ligand-engineered direct optical lithography of nanocrystals with\nindustrially compatible solvents. ACS Nano 19, 14509-14520 (2025).\n37\n[Comment #14] In conventional photolithography of QDs, the photoresists can help making thick QD\nfilms for other purposes, such as photodetectors. Is PIN able to make QD films with micrometer-scale\nthickness?\n[Response] We appreciate this insightful comment. In principle, PIN should be capable of forming\nmicrometer-scale thick QD patterns, provided that an appropriate PR thickness is achieved and thick,\nuniform QD films can be deposited on the PR patterns. As a demonstration, Fig. R1.4 shows ~2.5\nμm-thick green-emitting QD patterns prepared using KL5315 PR. In this case, the QD films were\nblade-coated, but the overall process—PR patterning, QD film casting, thermal crosslinking, and\nPR stripping—was identical to the procedures outlined in the manuscript. Indeed, utilizing PIN to\nfabricate micrometer-thick QD patterns for photodetector applications is a highly promising strategy.\nAt this moment, however, further optimization may be required to achieve the desired patterned\ndimension, structure and thickness. We aim to present these thick QD patterns, particularly tailored\nfor photodetector applications, in the near future.\nFig. R1.4. PIN photopatterning of 2.5-μm-thick InP/ZnSeS QD patterns using KL5315 PR. a,\nFluorescence microscopic image of the green-emitting QD patterns. b, Height profile of the green-\nemitting QD patterns.\nChanges made in Supplementary Information\n- As explained above to Comment #4, we added this data in Supplementary Fig. 45.\nKL5315 PR. a, Fluorescence microscopic image of the green-emitting QD patterns. b, Height profile\nof the green-emitting QD patterns.\n[General comment] This manuscript reported a crosslinking-assisted indirect photopatterning of\nquantum dots using the traditional photolithography method. With the assistance of Diazo-4-LiXer,\nmulti-color features were obtained, and decent device performance was achieved. By using these\nunique ligands, it seems that it is possible to solve the problems on the technology bench.\n[Response] We appreciate the Reviewer for the overall summary and critical assessment of our\nwork. In the revised manuscript and Supplementary Information, we have clarified the distinct\nadvantages of the proposed PIN photopatterning method, reinforced the discussion with additional\ndata and references, and provided further experimental results to address the points raised. A\ndetailed point-by-point response is provided below.\nList of changes made in Manuscript\n- (page 2, line 4 – page 2, line 10 / page 18, line 11 – page 18, line 18) Sentences have been\nrevised to clarify the advantages and novelty of Diazo-4-LiXer over previously reported\ncrosslinkers in the abstract and discussion section.\n- (page 12, line 12 – page 12, line 15) A description of the resolution limitations in QD patterning\nhas been added.\nList of changes made in Supplementary Inforamation\n- (Supplementary Note 3 / Supplementary Fig. 42) Supplementary Note 3 and\nSupplementary Fig. 42 have been added to describe the resolution limitations of the current\nsystem and to demonstrate the formation of 1 μm-linewidth QD patterns via PIN\nphotopatterning.\n- (Supplementary Fig. 47) Optoelectronic characteristics of green- and blue-emitting QD-LEDs\nhave been provided.\n40\n[Comment #1] However, some of the problems may be caused arbitrarily. For example, by using\nconventional photolithography or lift-off method, the QD patterns were not affected that much, as\nshown in Fig 1c, even if the pixel size was smaller than 5 μm (ACS Appl. Mater. Interfaces 2021, 13,\n36, 43075; Nano Lett. 2016, 16, 6946, Nanotechnology 2014, 25, 175302). To demonstrate the novelty\nof the method, smaller features (maybe < 1 um) should be prepared because this is really challenging\nusing traditional photolithography.\n[Response] We appreciate the comment. We successfully achieved a 1 μm minimum size dot pixel\n(Fig. R2.1). It is important to note that in PIN photopatterning, the resolution of the QD patterns is\ninherently determined by the resolution of the PR patterns. Resolution limit for our mask aligner\n(the MD-400LJ Midas system) in a hard contact mode was ~ 1 μm. Under the given constraint, we\nconsider that we have achieved the minimum feature attainable from our equipment. Although\ncurrent results are limited by our fabrication equipment, we believe there is strong potential for our\nmethod to be extended to even finer feature sizes. In particular, we anticipate that employing a high-\nspec i-line stepper and an appropriate photomask will allow achieving sub-1 μm patterns (as small\nas 0.55 μm).\nFig. R2.1. Optical image of the 1 μm-linewidth green-emitting InP/ZnSeS QD patterns formed\nvia PIN photopatterning using KL5301 PR.\nRegarding this comment, we added the following sentences in the manuscript and added\nSupplementary Note 3 in Supplementary Information. We also added Fig. R2.1 in Supplementary\nFig. 42.\nChanges made in Manuscript\n(page 12, line 12 – page 12, line 15) Patterns with 2 μm feature sizes could be successfully achieved\nfor these QDs. The minimal feature sizes of the QD patterns are constrained to the dimensions of\n41\nthe attainable PR patterns, which is determined by the type of the PR and the specification of the\nUV irradiation system (See Supplementary Note 3 and Supplementary Fig. 42)\nChanges made in Supplementary Information\nSupplementary Note 3. Resolution Limitations and Potential for Submicron QD features\nFor G-QDs, patterns with feature sizes as small as 1 μm could be attained. This value\ncorresponds to the resolution limit for our mask aligner (the MD-400LJ Midas system) in a hard\ncontact. Considering that the resolution of the QD patterns in PIN patterning is inherently\ndetermined by the resolution of the attainable PR patterns from the given aligner used, we anticipate\nthat employing an i-line stepper and an appropriate photomask will allow achieving sub-1 μm\npatterns.\nSupplementary Fig. 42. Optical image of the 1 μm-linewidth green-emitting InP/ZnSeS QD\npatterns formed via PIN photopatterning using KL5301 PR.\n42\n[Comment #2] In addition, from a scientific point of view, the present manuscript lacks novelty. The\nauthors failed to demonstrate the uniqueness of the ligands they proposed in this manuscript compared\nto other ligands. The nitrene- and carbene-based photocrosslinkers are systematically studied. Most of\nthem are both photo-sensitive and thermal-sensitive. What are the advantages of diazo-4-LiXer over\nthem (Angew. Chem. Int. Ed. 2022, 61, e202202633, ACS Nano 2022, 16, 13674)?\n[Response] We appreciate the feedback. Before we provide a detailed response to this comment,\nwe would like to clarify a misunderstanding regarding the term \"ligand\" in the reviewer’s comment.\nWe believe that the \"ligand\" mentioned by the reviewer refers to the \"crosslinker\" in our study.\nThe reviewer asked about the advantages of Diazo-4-LiXer compared to previously reported\ncrosslinkers described in two studies (Angew. Chem. Int. Ed. 2022, 61, e202202633; ACS Nano\n2022, 16, 13674). The most important advantage of Diazo-4-LiXer is its ability to enable thermal\ncrosslinking at a low temperature (110 °C) without degrading the performance of QDs as well as\nPR. This novel property makes PIN photopatterning possible and allows for the creation of record-\nhigh-fidelity QD patterns without any performance degradation. Previously reported azide- and\ndiazirine-based crosslinkers exhibited higher thermal crosslinking temperatures compared to Diazo-\n4-LiXer, which made them incompatible with PIN photopatterning. The high annealing temperature\nrequired to activate the azide- and diazirine-based crosslinkers will alter the chemical properties of\nunderlying PR pattern, which would make it difficult to completely remove the pre-formed PR\npatterns during the stripping step. In addition, it should be emphasized that unfortunately, no\nquantitative analysis of the pattern fidelity was provided from both papers, which would have\nprovided a more precise evaluation of the effectiveness of these patterning techniques. However,\nwe expect that the fidelity of the QD patterns obtained from the azide- and diazirine-based\ncrosslinkers through direct photopatterning must have been inferior to what we observed through\nPIN photopatterning that yields pattern structure guided by pre-formed PR (note that we have\nclearly proven the superiority of the PIN photopatterning to the direct photopatterning in this\nmanuscript).\nThese features clearly demonstrate the novelty and advantages of our current work.\nMoreover, the use of 2-bridge-type azide- and diazirine-based crosslinkers resulted in\ndeteriation in the luminescence characteristics after photocrosslinking in the mentioned references.\nMore specifically, in Angew. Chem. Int. Ed. 2022, 61, e202202633, the authors utilized 2-bridge-\ntype azide- and diazirine-based crosslinkers to perform direct photopatterning of QDs. However,\ntheir approach still resulted in a decrease in the PLQY (by ~45% using azide-based crosslinker and\n~10% using diazirine-based crosslinker) of the QDs after crosslinking. In contrast, PIN\n43\nphotopatterning using Diazo-4-LiXer at a low temperature demonstrated negligible performance\ndegradation of QDs even after crosslinking and patterning.\nLastly, another distinct advantage of Diazo-4-LiXer is its structure, which contains four diazo\nfunctional groups. This significantly enhances crosslinking efficiency compared to the previous\ncrosslinkers containing only two azide or diazirine groups. For the crosslinkers to successfully\nbridge the neighboring QDs, at least two functional groups must be activated. For crosslinkers with\ntwo function group, the success ratio can be roughly estimated to be p2 (where p is the chance of\nthe functional group being activated). For crosslinkers with four functional groups, this ratio would\nbe C p2(1-p)2+ C p3(1-p)1+ C p4(1-p)0. The improved crosslinking efficiency contributes to high\n4 2 4 3 4 4\npattern fidelity and strong QD film integrity.\nRegarding this comment, we modified the sentences in the Abstract and Discussion.\nChanges made in Manuscript\n- Abstract (page 2, line 4 – page 2, line 10)\nThe method employs Diazo-4-LiXer, a crosslinker, to bridge neighboring QDs by exploiting\nthe carbene-based reaction of the diazo functional group, which is activated at low temperatures.\nThanks to the sufficiently low processing temperature, the luminous properties of QDs (including\ntheir photoluminescence and electroluminescence characteristics) are preserved and the QD films\nare crosslinked without affecting the underlying photoresist pre-patterns which serve as structural\nguides in during QD pattern formation. By using PIN photopatterning, we form high-fidelity RGB\nQD patterns with pixel densities exceeding 4000 pixels per inch.\n- Discussion (page 18, line 11 – page 18, line 18)\nWe successfully demonstrated non-destructive and high-fidelity PIN photopatterning of QDs\nby using Diazo-4-LiXer, a low-temperature-activatable ligand crosslinker. This crosslinker binds\nthe aliphatic ligands of neighboring QDs. The unique chemical design of Diazo-4-LiXer, featuring\nfour diazo functional groups, facilitates crosslinking without compromising the structural integrity\nof the underlying sacrificial PR layer or the inherent properties of the crosslinked QD layer. By\nusing the proposed method, we achieved the highest-fidelity QD patterns reported to date,\nsurpassing the attainable quality using direct photopatterning.\n44\n[Comment #3] Why do people use these ligands in conventional lithography if they are inherently\ncapable of non-destructive patterning?\n[Response] We appreciate the reviewer’s question. Before addressing the core of the inquiry,\nwe would like to clarify a misunderstanding regarding the term \"ligand\" and the ambiguous phrase\n\"conventional lithography\" in the question. We assume that \"ligand\" refers to a \"crosslinker\" and\nthat \"conventional lithography\" refers to \"direct photopatterning.\"\nIt is important to note that crosslinkers are not necessary when using photoresist (PR)-based\nconventional lithography, which involves a PR patterning step on the QD film, a QD etching step\nto transfer the PR pattern shape onto the underlying QD film, and a PR removal step. Since QDs\nare highly prone to degradation during the physical or chemical etching step, QDs are generally not\nprocessed through PR-based conventional lithography.\nAs for why this non-destructive crosslinker is not widely adopted for direct photopatterning,\nthe primary reason might be that direct photopatterning often results in poor pattern fidelity, as we\ndemonstrated in Fig. 2 of our manuscript. In contrast, our PIN photopatterning method leverages\nthe structural guidance of a PR layer, allowing for the formation of high-fidelity QD patterns. The\nkey advantage of our approach is that it not only enables non-destructive crosslinking but also\nallows us to activate the crosslinking a low-temperature annealing process below 110 °C, making\nit compatible with PR-based patterning techniques. The ability to utilize PR for structural guidance,\nwhile maintaining the integrity of the QDs, is a crucial advantage of our method. For your\ninformation, previous azide- or diazirine-based crosslinkers require a high crosslinking temperature\n(>150 °C) and a long crosslinking period (>60 min, usually 2 or 3 hours at 200 °C from our\nexperimental experience) upon thermal crosslinking. And, the lower crosslinking temperature the\nlonger crosslinking period.\n45\n[Comment #4] The original PR pattern was 70 nm, and the resulting thickness was reduced to 17 nm\nafter the etching process. Will this treatment affect the previous QD layers? What is the device\nperformance of green and blue QLEDs? Suppose the authors claimed that this ion etching technique\nhelps solve conventional lithography problems when patterning quantum dots. In that case, it is\nparticularly important to confirm the performance of quantum dots after processing using the\nperformance of QLED devices. Based on the abovementioned issues, I cannot recommend publishing\nthis manuscript at this stage, but I encourage the authors to improve the quality of their manuscript and\nresubmit it.\n[Response] We sincerely appreciate the critical assessment. We acknowledge that, in our original\nmanuscript, we overlooked the potential impact of the etching process on the underlying HTL/ETL\nlayers and, consequently, on device performance. As the reviewer pointed out, direct ion etching of\nPR could damage these layers, leading to performance degradation.\nTo address this concern, we explored alternative approaches to achieve the required thin PR\nlayer (e.g., 17 nm) without the need for an etching step. As mentioned above, we tested two\nstrategies: (i) diluting the existing KL5301 PR solution to reduce its thickness, and (ii) utilizing\nDSP-DJ2, a commercially available ultra-thin PR designed for fine patterning. Among these, the\nDSP-DJ2-based approach provided more reproducible results, and we used it for further\nexperiments.\nWith this optimized process, we successfully obtained well-defined patterns and fabricated\nQLED devices—all without undergoing any etching steps. Notably, the performance of these\ndevices confirms that our patterning approach does not induce significant degradation. We\nemphasize that all results presented here, including both patterning fidelity and QLED performance,\nwere achieved without ion etching, thereby eliminating the concern of potential damage to\nunderlying layers.\nIn response to this comment, we have added electroluminescence characteristics of green and\nblue QLEDs in Supplementary Fig. 47.\nSupplementary Fig. 47. Electroluminescence characteristics of green and blue QD devices. (a,\nb) J-V-L characteristics and (c, d) EQE-J characteristics of the green-emitting InP/ZnSeS and blue-\nemitting ZnSeTe/ZnSe/ZnS QD EL devices. Black: Pristine QDs; Colored: Crosslinked QDs.\n[General comment] In the manuscript, the authors designed a low-temperature-activatable ligand\ncrosslinker, Diazo-4-LiXer, which can bridge neighboring QDs at low temperature, thereby preserving\nthe luminous properties of QDs. Micrometer-scale QDs patterns with excellent fidelity were formed\nusing crosslinking-assisted, photoresist-guided indirect (PIN) photopatterning. And full-color RGB\nQD patterns with a resolution exceeding 4000 PPI were obtained by continuously applying PIN\nphotopatterning technology to R-, G-, and B-QD, demonstrating the potential application of low-\ntemperature cross-linking assisted PIN photopatterning in the display industry. I recommend its\npublication after major revision.\n[Response] We sincerely appreciate the Reviewer for the encouraging overall evaluation and\nconstructive suggestions. We have carefully addressed each point raised and revised the manuscript\nand Supplementary Information accordingly. A point-by-point response is provided below.\nList of changes made in Manuscript\n- (page 2, line 4 – page 2, line 10 / page 18, line 11 – page 18, line 18) Sentences have been\nrevised to clarify the advantages and novelty of Diazo-4-LiXer over previously reported\ncrosslinkers in the abstract and discussion section.\n- (page 12, line 21 – page 12, line 23) A description of how the QD layers are protected from\nUV light during the sequential patterning process has been added.\nList of changes made in Supplementary Information\n- (Supplementary Fig. 43) Schematic description of subsequent QD PIN photopatterning\nprocess has been provided.\n- (Supplementary Fig. 44) Fluorescence microscopic images of QD patterns in various shapes\nhave been added.\n48\n[Comment #1] It is recommended to create patterned quantum dot fluorescence microscopy images\nwith complex logos, microdot/diamond/triangle arrays, letters, and line forms to more intuitively\ndisplay the characteristics of this approach for producing high-resolution and high-fidelity patterns.\n[Response] We appreciate the comment. We formed various shape patterns as you recommended,\nand the results are shown in Fig. R3.1. We consider that the results help displaying the\ncharacteristics of PIN Photopatterning for producing QD patterns.\nFig. R3.1. Fluorescence microscopic images of InP/ZnSeS QD patterns in various shapes prepared\nvia PIN photopatterning method using KL5301 PR.\nIn response to this comment, we have added the following sentence. We also added these\nmicroscopic images in Supplementary Fig. 44.\nChanges made in Manuscript\n(page 12, line 29 – page 12, line 30) We also confirmed that QD patterns with complicated\ngeometry could be successfully obtained through PIN photopatterning (Supplementary Fig 44).\nChanges made in Supplementary Information\nSupplementary Fig. 44. Fluorescence microscopic images of InP/ZnSeS QD patterns in\nvarious shapes prepared via PIN photopatterning method using KL5301 PR.\n49\n[Comment #2] In the process of forming multi-color quantum dot patterns, how can the negative\nimpact of UV light and RIE on the performance of quantum dots be mitigated or eliminated?\n[Response] We appreciate the important question regarding the potential impact of UV exposure\nand RIE on the performance of QDs during multi-color patterning.\nFirst, we emphasize that RIE is now unnecessary in our process. As pointed out in the\nmanuscript, thickness control of PR was critical to form QD patterns without ear structure.\nConsidering the EL device applications where the target QD EML thickness is typically below 20\nnm, we sought for methods to attain PR patterns at such thickness. Because the thinnest possible\nthickness attainable from a commercially available photoresist using an established recipe was 70\nnm, the thickness of the PR patterns had to be reduced to ~20 nm, and this was done by RIE.\nAlthough this approach seemed to work, the three reviewers raised concerns about involving an\netching process, as it could not only reduce the photoresist pattern thickness (as intended) but also\ndamage the underlying HTL or ETL. To address this issue, we utilized a different photoresist (DSP-\nDJ2 from Dongjin Semichem Co. Ltd.) during the revision. DSP-DJ2 successfully formed <20 nm\nthick PR patterns directly without involving an etching process. Therefore, now the concerns raised\nby the reviewer are eliminated.\nSecond, to prevent QDs from being directly exposed to UV light, we use a positive-type PR.\nThis ensures that the QD films are not directly illuminated during the patterning steps. For example\n(Fig. R3.2), when sequentially processing multiple QD colors, the first patterned QD layers remain\ncovered with PR throughout the subsequent PIN patterning steps. This means that even during the\nPR exposure for the next color patterning, previously deposited QD patterns are not directly\nsubjected to UV exposure. We believe this process design plays a key role in maintaining QD\nperformance, which is reflected in the fact that no significant degradation in device performance\nwas observed after the full multi-color patterning process.\nFig. R3.2. Schematic description of subsequent QD patterning process via PIN photopatterning.\nFig. R3.2 in Supplementary Fig. 43.\nChanges made in Manuscript\n(page 12, line 21 – page 12, line 23) In addition, previously deposited QD layers were protected\nfrom direct UV exposure during this process, ensuring the preservation of their performance\n(Supplementary Fig. 43).\nChanges made in Supplementary Information\nSupplementary. Fig. 43. Schematic description of subsequent QD patterning process via PIN\nphotopatterning.\n51\n[Comment #3] This approach preserves quantum dot performance during patterning, however, high\ntemperatures will still be encountered in subsequent applications. What are the prospects of employing\nthis strategy?\n[Response] We appreciate the insightful question regarding the impact of high temperatures in\nsubsequent applications. The key factor in temperature sensitivity during processing is the presence\nof PR. PR layer can undergo chemical changes at elevated temperatures and therefore development\nor stripping steps may not be executable, which is why we designed our process to operate at\nrelatively low temperatures to ensure stability. However, once the PIN photopatterning process is\ncomplete and the final QD patterns are obtained (i.e., after the PR is fully removed), high\ntemperatures are no longer a concern. From this stage, additional high-temperature processing steps\ncan be applied, as long as this temperature does not degrade the properties of QDs.\n52\n[Comment #4] Why choose the Crosslinking of Diazo-4-LiXer?\n[Response] We appreciate the comment from the reviewer regarding our choice of Diazo-4-LiXer\nas the crosslinker for QDs in this study. The selection of this particular crosslinker was based on its\ndistinct advantages over conventional alternatives, particularly in the context of the PIN\nphotopatterning process.\n1. Low-temperature crosslinking capability: The primary reason for choosing Diazo-4-LiXer is its\nability to undergo heat-induced crosslinking at a relatively low temperature of 110 °C. As\noutlined in the manuscript, the PIN photopatterning process requires that thermal crosslinking\noccur below 140 °C to ensure effective removal of the PR pattern and successful formation of\nthe desired QD pattern. Previously reported azide-based crosslinkers were found to be\nunsuitable for this process because they require significantly higher crosslinking temperatures\n(exceeding 150 °C), which would compromise the photopatterning integrity and QD\nperformance.\n2. Preservation of QD luminescence characteristics based on steric suppression of undesired\nsurface reactions: Diazo-4-LiXer also offers the critical advantage of preserving luminescence\ncharacteristics of QDs. This is attributed to the secondary carbene structure in the crosslinker,\nwhich sterically suppresses unwanted surface reactions involving the reactive carbene\nintermediate that could otherwise interfere with the QD surface. A similar steric suppression\nstrategy was successfully demonstrated in our previous workR12, where we introduced bulky\nisopropyl groups to perfluorinated phenyl azide crosslinkers. This structural modification\neffectively prevented direct interactions between nitrene and the QD surface. A more detailed\ndiscussion of this effect is also provided in our response to Comment #11 of Reviewer 1.\n3. Enhanced crosslinking efficiency via a four-bridge structure: Another important advantage of\nDiazo-4-LiXer is its unique four-bridge molecular design, which integrates four diazo functional\ngroups within a single molecule. This structural feature significantly enhances the crosslinking\nefficiency compared to conventional two-bridge crosslinkers, leading to a more robust\ncrosslinked QD network and improved pattern stabilityR12.\nGiven these advantages—low-temperature process compatibility, QD property preservation\nthrough steric effects, and enhanced crosslinking efficiency—we believe that Diazo-4-LiXer is the\nmost suitable crosslinker for PIN patterning, which could produce QD patterns having both\npreserved luminescence characteristics and excellent fidelity at the same time.\nReferences\n34, 2205504 (2022).\nRegarding this comment, we modified the sentences in the Abstract and Discussion.\nChanges made in Manuscript\n- Abstract (page 2, line 4 – page 2, line 10)\nThe method employs Diazo-4-LiXer, a crosslinker, to bridge neighboring QDs by exploiting\nthe carbene-based reaction of the diazo functional group, which is activated at low temperatures.\nThanks to the sufficiently low processing temperature, the luminous properties of QDs (including\ntheir photoluminescence and electroluminescence characteristics) are preserved and the QD films\nare crosslinked without affecting the underlying photoresist pre-patterns which serve as structural\nguides in during QD pattern formation. By using PIN photopatterning, we form high-fidelity RGB\nQD patterns with pixel densities exceeding 4000 pixels per inch.\n- Discussion (page 18, line 11 – page 18, line 18)\nWe successfully demonstrated non-destructive and high-fidelity PIN photopatterning of QDs\nby using Diazo-4-LiXer, a low-temperature-activatable ligand crosslinker. This crosslinker binds\nthe aliphatic ligands of neighboring QDs. The unique chemical design of Diazo-4-LiXer, featuring\nfour diazo functional groups, facilitates crosslinking without compromising the structural integrity\nof the underlying sacrificial PR layer or the inherent properties of the crosslinked QD layer. By\nusing the proposed method, we achieved the highest-fidelity QD patterns reported to date,\nsurpassing the attainable quality using direct photopatterning.\n54\n[Comment #5] The method for photopatterning can be expand for other QDs? Some other QDs may\nbe utilized for assessment.\n[Response] The Diazo-4-LiXer-based PIN photopatterning method holds universal applicability to\nother quantum dots (QDs), provided they are encapsulated with aliphatic ligands. In our manuscript,\nwe have demonstrated the effectiveness of PIN photopatterning for CdSe, InP, and ZnSeTe QDs.\nAdditionally, the applicability of PIN patterning to CuInS, InAs, and PbS QDs is illustrated in\nSupplementary Fig. 46 (also shown as Fig. R3.3 below).\nFig. R3.3. Optical microscopy images of line patterns for CuInS (left), InAs (middle), and PbS\n(right) QDs obtained from the PIN photopatterning.\n[General comment] In the revised manuscript, the authors have addressed most of the concerns raised\nby the reviewers. Two major improvements are: 1) correction of the overestimated precision of the\nLER. The corrected LER is about 40 nm. Although much lower than the value claimed in the original\nversion, this is still a good value. 2) The authors used a new photoresist that allowed for making resist\nlayer of around 20 nm. This helped eliminating the dry etching step not suitable for QLED fabrication.\nThe authors also showed the performance of RGB QLEDs. Overall, I think the quality of the\nmanuscript has greatly improved. However, I would like to recommend the authors to make the\nfollowing changes before it can be accepted.\n[Comment 1-1] Figure 2e compares the LER of PIN patterned and direct photopatterned QD layers\n(in previous work). The LER of about 40 nm is on par with those achieved in one of the authors'\nprevious work (Adv Mater 2022, 34, 2205504). In the Adv Mater work, the patterning was done by\nusing a 6-branch azide based photocrosslinker. Therefore, it may not be proper to claim in the\nDiscussion that \"By using the proposed method, we achieved the highest fidelity QD patterns reported\nto date, surpassing the attainable quality using direct photopatterning\". In other words, I agree with\nthe authors that the ~40 nm LER made here is a good number but I do not think it is fair to say the\ndirect photopatterning methods cannot achieve this level (may be misleading to researchers not\nfamiliar with this field).\n[Response] We appreciate Reviewer #1’s insightful comments. Reviewer #1 pointed out that the line\nedge roughness (LER) reported in the current manuscript is at a similar level (40 nm) to that of our\nprevious work (Adv. Mater. 2022, 34, 2205504). However, we should point out that there is an\nimportant misunderstanding that need to be clarified. The LER value reported in Adv. Mater.\n2022, 34, 2205504 is based on 1 sigma (which is simply the standard deviation of the data),\nwhereas the LER value reported in this manuscript is based on the 3 sigma. The use of 3 sigma\nvalue for LER is the standard in the photoresist community and represents the range\nencompassing 99.7% of deviations—offering a more rigorous and comprehensive assessment of\npatterning fidelity. We have only realized this standard recently, and, we admit that we have bluntly\nused 1 sigma value in the previous work (And we found that other reports on the QD patterning have\nused 1 sigma). Based on this new standard, there is a sufficient improvement in the fidelity;\n150\nnm (based on 3 sigma value) for our previous work vs 40 nm (also based on 3 sigma value) for\nour current work.\ndemonstrates a clear improvement. In the previous work (Adv. Mater. 2022, 34, 2205504), the line\nwidth variability was reported to be 700 nm (which is based on 1 sigma value, corresponding to\n2100 nm based on 3 sigma value), while in our current manuscript (Figure 2d, right plot), the\nline width roughness is significantly lower at 139.3 nm. (Note that we also changed the name of\n“line width variability” into “line width roughness” to discuss fidelity more specifically.) Therefore,\nour statement that “By using the proposed method, we achieved the highest fidelity QD patterns\nreported to date, surpassing the attainable quality using direct photopatterning” remains fully\nvalid.\nFigure R1.1. (a) Line width and variability as shown in Figure 3d of Adv. Mater. 2022, 34, 2205504.\nThe error bar in this histogram (which is the line width variability) corresponds to the 1 sigma of the\nvariation. (b) Line width roughness as shown in Figure 2d of our manuscript.\nTo prevent confusion and ensure fair comparison, we have revised the text to clarify this distinction\nand removed any potentially misleading claims of superiority. The revised sentence now reads:\n“The LER values of ~40 nm (based on 3σ) achieved herein, are the smallest among the\nphotolithographically obtained QD patterns reported to date and represent a significant improvement\nover our previous direct photopatterning work when compared on an equivalent statistical basis. (Fig.\n2e and Supplementary Table 2-3).” We hope this clarification addresses the reviewer’s concern.\nIn addition, we summarize the improvement we attained from this work compared to the previous\nAdv. Mater. 2022, 34, 2205504, in terms of PLQY and EQE preservation, pattern fidelity parameters,\nand crosslinking conditions.\nMinimum Industrial\nLER v-LWR\nDecrease of Decrease of Pattern compatibility\nRef. (nm) (nm)\nPLQY EQE Size (Crosslinking\n(basis) (basis)\n(µm) condition)\nAdv. Mater. 2022, 34,\nMedium\n150\n2205504 ~2% Nearly identical 2100\n1 (254 nm UV for\n(Our previous work by (green InP) (0.4% decrease) (3σ) (3σ)\ncrosslinking)\ndirect photopatterning)\nThis work Good\n59.6 1040\nby direct N/A N/A 2 (365 nm UV for\n(3σ) (3σ)\nphotopatterning crosslinking)\n40.0 121.3 Good\nThis work by PIN ~1% 2\nNearly identical (or 45.9*) (or 124.3*) (Low temp.\nphotopatterning (green InP) (or 0.8*)\n(3σ) (3σ) crosslinking)\n* This value was obtained from QD patterns prepared using an i-line stepper. Other values with no\nasterisk (if not mentioned specifically) were obtained from QD patterns prepared using a mask aligner.\nFurthermore, please refer to the new Supplementary Fig. S38 and Supplementary Table 4 in the\nrevised draft for fair and comprehensive comparison with the reported results on the 3 sigma basis.\nset based on the values reported in the literature).\nMinimum Industrial\nLER LWR\nDecrease of Decrease of Pattern compatibility\nRef. (nm) (nm)\nPLQY EQE Size (Crosslinking\n(basis) (basis)\n(µm) condition)\nMedium\nNano Lett. 2023, 23, 2000- ~10% Nearly identical 300\n2008 (red InP) (0.7% decrease) (3σ)\ncrosslinking)\nNearly identical Medium\nNat. Commun. 2020, 11, ~1% 420\n(Only EQE plot 2 N/A (254 nm UV for\n2874 (red CdSe) (3σ)\nreported) crosslinking)\nGood\nJ. Am. Chem. Soc. 2024, ~10% Nearly identical 300\n146, 28895 (red InP) (0.1% increase) (3σ)\ncrosslinking)\nNearly identical 297 Good\nNat. Nanotechnol. 2022, ~2% 222\n(Only EQE plot 0.8 (3σ) (365 nm UV for\n17, 952-958 (green InP) (3σ)\nreported) (l-LWR) crosslinking)\nAdv. Mater. 2022, 34, ~2% Nearly identical 150\n1 (3σ) (254 nm UV for\n2205504 (green InP) (0.4% increase) (3σ)\n(v-LWR) crosslinking)\nGood\nACS Nano 2025, 19, ~3% Nearly identical 600\n14509-14520 (red CdSe) (0.5% decrease) (3σ)\ncrosslinking)\nN/A ~5% enhanced\nGood\nACS Nano 2024, 18, (Only PL (HTL-crosslinked\n15915 intesity device. (not QD-\ncrosslinking)\nincluded) crosslinked))\nBad\nN/A\nACS Nano 2022, 16, ~10% (Thermal\n(EL performance ~10 N/A N/A\n13674-13683 (red CdSe) crosslinking using\nnot reported)\nlaser)\n55.8\n(or 75.8*)\n(l -LWR)\n40.0 Good\n~1% 2 121.3\nThis work Nearly identical (or 45.9*) (Low temp.\n(green InP) (or 0.8*) (or\n(3σ) crosslinking)\n124.3*)\n(v-LWR)\n(3σ)\n* This value was obtained from QD patterns prepared using an i-line stepper. Other values with no\nasterisk (if not mentioned specifically) were obtained from QD patterns prepared using a mask aligner.\n4\n[Comment 1-2] Supplementary Table 2. Please double check the maximum EQE listed in the top two\nrows (related to Refs. S3 and S4). According to Ref. S4 (Cho, et al. Adv Mater. 2020, 32, 2003805),\nthe EQE of green Cd-based QLEDs was about 5% (instead of 0.5% for green InP based QDs).\nThe authors should list the highest EQEs of directly photopatterned QLEDs reported in previous work or\nclearly list the EQEs of devices made from different types of QDs (colors and compositions, as they\ndid for the row in Table S2 related to S11) in previous reports, instead of citing a low performance data.\nAdditionally, the authors may also need to cite performance data from other relevant refs using\ndifferent photochemistry, such as Nie, Adv. Funct. Mater. 2025, 2420829 (click chemistry); Fu, J. Am.\nChem. Soc. 2024, 146, 28895(diazirine based crosslinkers); and Seo, Chem. Mater. 2025, 37, 1424\n(dynamic S-S bond), published during the revision of this manuscript.\n[Response] We appreciate Reviewer #1’s suggestions. As suggested by Reviewer #1, we have\nreviewed and corrected the EQE values in Table S2 of the Supplementary Information. We have also\nadded the data from the three references mentioned by the reviewer.\nIt appears that the reviewer may have been confused by some of the references. In our revised\nSupporting Information, Ref. S3 corresponds to “Maeng, S. et al. Direct photocatalytic patterning of\ncolloidal emissive nanomaterials. Sci. Adv. 9, eadi6950 (2023)”, and Ref. S4 corresponds to “Lee, J.\net al. Direct optical lithography of colloidal InP-based quantum dots with ligand pair treatment. ACS\nEnergy Lett. 8, 4210–4217 (2023)”. We would like to clarify that the Cho et al. Adv. Mater. 2020, 32,\n2003805 paper mentioned by the reviewer corresponds to Ref. S9, not S4. In accordance with the\nreviewer’s comment, we have revised the EQE value reported for Ref. S9. We also note that in\nsome papers, the maximum EQE is not explicitly stated in the text and only an EQE plot is\nprovided. In such cases, we tried to read out the maximum EQE value from the plot and added\na label “(only EQE plot reported)” as well.\nThe revised table is shown below.\nSupplementary Table S2. Comparison of QD patterns formed using various functional groups.\nMinimum\nLER l-LWR v-LWR PLQY\nPatterning Activation pattern Maximum\nFunctional group (basis) (basis) (basis) changes of Ref.\nmethod source width EQE\nQDs\nnm nm nm µm\n~3%\n~2.2%\nUV decrease\nDirect (green\n220 600\n(275 nm (green CdSe)\nphoto- Thiol-ene N/A 1 CsPbBr ) S3\nor (3σ) (3σ) 3\npatterning (Only EQE\n365 nm) ~0%\nplot reported)\ndecrease\n5\n(green InP)\n~5%\nincrease\n(green\nCsPbBr\n2-(4-\nmethoxystyryl)-4,6- ~0.5%\n~34%\nDirect bis(trichloromethyl)- 750 a (green\nUV decrease\nphoto- 1,3,5-triazine N/A N/A 1 InP) S4\n(365 nm) (3σ) (PLQY of red\npatterning (MBT), (Only EQE\nInP)\n(Photo acid plot reported)\ngenerator)\n~1%\nDirect 14.6%\nphoto- Azide N/A N/A 2 (red S5\n(254 nm) (3σ) (PLQY of red\npatterning CdSe)\nCdSe)\n~10%\ndecrease\n(PLQY of red 19.1%\nInP) (red CdZnSe)\nTriphenylmethyl\n~12% 17.5%\nDirect chloride 300 a\nUV decrease (green\nphoto- (TPCl), N/A N/A 4 S6\n(254 nm) (3σ) (PLQY of CdZnSe\npatterning (Carbocation\ngreen InP)\ngenerator)\n12.0%\n~31% (blue\ndecrease CdZnSe)\n(PLQY of\nblue ZnSe)\n~20.0%\n~2%\nDirect (red\n222 297\nUV decrease\nphoto- Benzophenenone N/A 0.8 CdSe) (Only S7\n(365 nm) (3σ) (3σ) (PLQY of\npatterning EQE plot\ngreen InP)\nreported)\n~2%\nDirect 8.3%\n150 2100\nUV decrease\nphoto- Azide N/A 1 (green S8\n(254 nm) (3σ) (3σ) (PLQY of\npatterning InP)\ngreen InP)\n2-(4-\nmethoxystyryl)-4,6-\n~25%\nDirect bis(trichloromethyl)- 150 a\nUV decrease 5.08%\nphoto- 1,3,5-triazine N/A N/A 1.5 S9\n(365 nm) (3σ) (PLQY of red (green CdSe)\npatterning (MBT),\nCdSe)\n(Photo acid\ngenerator)\n~25%\nDirect 390 a\nOrtho-nitrobenzyl UV decrease\nphoto- N/A N/A 2 N/A S10\nester (365 nm) (3σ) (PLQY of\npatterning\ngreen InP)\n6\n~3%\ndecrease\n(PLQY of red\n22.0%\nCdSe)\n(red\nCdSe)\n~3%\nDirect 600 a\nUV decrease\nphoto- Methacrylate (MA) N/A N/A 1 14.4% S11\n(365 nm) (3σ) (PLQY of\npatterning (green CdSe)\ngreen CdSe)\n11.4%\n~17%\n(blue CdSe)\ndecrease\n(PLQY of\nblue ZnSeTe)\n~4% increase\n(PLQY of red 20.05% (red\nCdZnSe) CdZnSe)\n~12%\nincrease 15.37%\nDirect\nAlkyne-Azide UV (PLQY of (green\nphoto- N/A N/A N/A 1.2 S12\ncycloaddition (365 nm) green CdZnSe)\npatterning\nCdZnSe)\n~3% increase 8.49%\n(PLQY of (blue\nblue CdZnSe)\nCdZnSe)\n~10%\ndecrease\n(PLQY of red\nInP)\n~13%\nDirect 300 a\nUV decrease 15.3%\nphoto- Diazirine N/A N/A 1 S13\n(365 nm) (3σ) (PLQY of (red InP)\npatterning\ngreen InP)\n~30%\ndecrease\n(PLQY of\nblue ZnSe)\nN/A\nDirect (only PL\nUV\nphoto- Azide N/A N/A N/A 5 intensity N/A S14\n(254 nm)\npatterning plots are\nreported)\n~2%\ndecrease\n40.0 55.8 121.3\n(PLQY of\nHeat (or (or (or\nPIN photo- 2 16.6% This\nDiazo red CdSe) (110 °C) 45.9*) 75.8*) 124.3*) (or 0.8) (red CdSe) work\npatterning (3σ) (3σ) (3σ)\n~1%\ndecrease\n7\n(PLQY of\ngreen InP)\n~7%\ndecrease\n(PLQY of\nblue\nZnSeTe)\naIn cases where the authors did not specify how LER or LWR values were defined, we assumed the\nreported values were based on a 1σ (one standard deviation) definition. For consistent comparison, we\nrecalculated all reported values on a 3σ basis.\n* This value was obtained from QD patterns prepared using an i-line stepper. Other values with no\nasterisk (if not mentioned specifically) were obtained from QD patterns prepared using a mask aligner.\nReferences for Supplementary Table S2.\nS3. Maeng, S. et al. Direct photocatalytic patterning of colloidal emissive nanomaterials. Sci. Adv. 9,\neadi6950 (2023).\nS4. Lee, J. et al. Direct optical lithography of colloidal InP-based quantum dots with ligand pair\ntreatment. ACS Energy Lett. 8, 4210-4217 (2023).\nS5. Yang, J. et al. High-resolution patterning of colloidal quantum dots via non-destructive, light-\ndriven ligand crosslinking. Nat. Commun. 11, 2874 (2020).\nS6. Fu, Z. et al. Direct photo-patterning of efficient and stable quantum dot light-emitting diodes via\nlight-triggered, carbocation-enabled ligand stripping. Nano Lett. 23, 2000-2008 (2023).\nS7. Hahm, D. et al. Direct patterning of colloidal quantum dots with adaptable dual-ligand surface.\nNat. Nanotechnol. 17, 952-958 (2022).\nS8. Yang, J. et al. Nondestructive photopatterning of heavy-metal-free quantum dots. Adv. Mater. 34,\n2205504 (2022).\nS9. Cho, H. et al. Direct optical patterning of quantum dot light-emitting diodes via in situ ligand\nexchange. Adv. Mater. 32, 2003805 (2020).\nS10. Lee, J. et al. Photocleavable ligand-induced direct photolithography of InP-based quantum dots.\nACS Energy Lett. 10, 94-101 (2025).\nS11. Xiao, P. et al. Ligand-engineered direct optical lithography of nanocrystals with industrially\ncompatible solvents. ACS Nano 19, 14509-14520 (2025).\nS12. Nie, Q. et al. Direct Optical Patterning of Quantum Dot Light-Emitting Diodes Based on Ultrafast,\nLow-Energy, Site-Controlled Click Chemistry Reaction. Adv. Funct. Mater. 2420829 (2025).\nS13. Fu, Z. et al. Direct Photopatterning of Colloidal Quantum Dots with Electronically Optimized\nDiazirine Cross-Linkers. J. Am. Chem. Soc. 146, 28895 (2024).\nS14. Seo, H. et al. Direct Photolithography of Colloidal InP-Based Quantum Dots Utilizing the\nPhotoligation Method. Chem. Mater. 37, 1424 (2025).\n[General comment] Despite the authors adding some experimental data during the revision process,\nthese additions unfortunately do not substantially enhance the overall quality of the manuscript. The\nprimary concerns remain unresolved, particularly with regard to the lack of innovation and deficiencies\nin the experimental design. There is also insufficient data to support the practical applicability of this\nstudy. Therefore, the manuscript is not suitable for publication in Nature Communications.\nSpecific comments are outlined as follows:\n[Response] Considering the comments from Reviewer #2, there may have been some\nmisunderstandings regarding the key points of our manuscript. In particular, even when\ncomparing data in the previous literatures including the papers in the Reviewer #2’s comments\nwith our current work, we strongly consider that our manuscript presents a superior approach\nto other previous approaches. Our detailed response is provided below.\nReviewer #2 raised concerns regarding the lack of novelty in our manuscript. To clarify the novelty\nof our work in comparison with previously reported studies, we conducted a comparative\nanalysis using a radar chart (Supplementary Fig. 38) and a summary table (Supplementary\nTable 4). (We note that the paper referenced in [Comment 2-2] by Reviewer #2, i.e. ACS Nano 2024,\n18, 15915, could not be included in the radar chart due to insufficient data provided to construct a\ncomplete polygon. Nevertheless, it is included in the comparison table.)\nThe comparison demonstrates that our PIN photopatterning method clearly outperforms\npreviously-reported results based on both direct photopatterning and thermal patterning\napproaches across all evaluated metrics. We emphasize that novelty and innovation in this\ncontext must be evaluated based on simultaneous achievement of multiple key factors, including\noptical/electrical non-destructiveness, high-resolution patterning capability, pattern fidelity, and\nindustrial compatibility rather than based on achievement of single factor separately. Unlike any\nprior work, our work uniquely demonstrates: i) a non-destructive QD process showing minimal\ndegradation in luminescence characteristics (ΔPLQY < 1%, and ΔEQE <1%), ii) micrometer-scale QD\npatterning (feature size = 0.8 μm), and iii) the highest QD pattern fidelity reported to date (LER < 40\nnm in a 3σ scale), all achieved at the same time through a scalable industry-compatible\nphotolithographic process.\nphotopatterning methods. (B) Comparison between this work and a previous thermal patterning\nmethod. Complete pentagon plot could not be constructed because the data on EQE and fidelity factors\nwere not reported in ACS Nano 2022, 16, 13674.\nset based on the values reported in the literature).\nMinimum Industrial\nLER LWR\nDecrease of Decrease of Pattern compatibility\nRef. (nm) (nm)\nPLQY EQE Size (Crosslinking\n(basis) (basis)\n(µm) condition)\nMedium\nNano Lett. 2023, 23, 2000- ~10% Nearly identical 300\n2008 (red InP) (0.7% decrease) (3σ)\ncrosslinking)\nNearly identical Medium\nNat. Commun. 2020, 11, ~1% 420\n(Only EQE plot 2 N/A (254 nm UV for\n2874 (red CdSe) (3σ)\nreported) crosslinking)\nGood\nJ. Am. Chem. Soc. 2024, ~10% Nearly identical 300\n146, 28895 (red InP) (0.1% increase) (3σ)\ncrosslinking)\nNearly identical 297 Good\nNat. Nanotechnol. 2022, ~2% 222\n(Only EQE plot 0.8 (3σ) (365 nm UV for\n17, 952-958 (green InP) (3σ)\nreported) (l-LWR) crosslinking)\nAdv. Mater. 2022, 34, ~2% Nearly identical 150\n1 (3σ) (254 nm UV for\n2205504 (green InP) (0.4% decrease) (3σ)\n(v-LWR) crosslinking)\nGood\nACS Nano 2025, 19, ~3% Nearly identical 600\n14509-14520 (red CdSe) (0.5% decrease) (3σ)\ncrosslinking)\nN/A ~5% enhanced\nGood\nACS Nano 2024, 18, (Only PL (HTL-crosslinked\n15915 intesity device. (not QD-\ncrosslinking)\nincluded) crosslinked))\nBad\nN/A\nACS Nano 2022, 16, ~10% (Thermal\n(EL performance ~10 N/A N/A\n13674-13683 (red CdSe) crosslinking using\nnot reported)\nlaser)\n55.8\n(or 75.8*)\n(l -LWR)\n40.0 Good\n~1% 2 121.3\nThis work Nearly identical (or 45.9*) (Low temp.\n(green InP) (or 0.8*) (or\n(3σ) crosslinking)\n124.3*)\n(v-LWR)\n(3σ)\n* This value was obtained from QD patterns prepared using an i-line stepper. Other values with no\nasterisk (if not mentioned specifically) were obtained from QD patterns prepared using a mask aligner.\nemphasize that the development of our high-resolution PIN photopatterning method required\nsubstantial time and effort, involving numerous modifications to experimental approaches. Our\napproach leverages commercially available photoresists and i-line light sources, ensuring full\ncompatibility with standard industrial photolithographic tools. Importantly, this method is nearly non-\ndestructive and significantly milder than conventional techniques such as reactive ion etching (RIE)\nor chemical etching, which often degrade the physical properties of QD patterns as well as adjacent\ncharge-transporting layers in devices.\nWhile the photopatterning process may appear simple and straightforward in the manuscript,\nits development involved overcoming several critical challenges. Below, we highlight major technical\nissues we encountered and how we addressed them:\n1. Control of PR Pattern Thickness and Suppression of QD Pattern “Ears”: Initially, the\nconventional lift-off process led to undesirable “ear” formations in the QD patterns, primarily due\nto inadequate control of photoresist (PR) thickness. To mitigate this, we introduced a RIE step to\nrefine the PR thickness, which significantly reduced ear formation. (We have since developed an\nalternative process that eliminates the need for RIE.)\n2. Effective Crosslinking at Low Temperatures: Without effective crosslinking, the patterned QDs\nlacked structural integrity (see Figure 1c). Although we initially used our previously developed\nazide-based crosslinkers (e.g., 2Bx, 4Bx, 6Bx, IP-4Bx, IP-6Bx), these required high activation\ntemperatures (~180 °C), which interfered with the PR lift-off step and left substantial PR residue.\nAfter extensive exploration, we identified the diazo functional group as a low-temperature\nalternative and subsequently developed Diazo-4-LiXer. This crosslinker enabled efficient QD film\ncrosslinking at 110–120 °C, allowing for clean PR lift-off while preserving the QD film’s optical\nand electrical performance. (We would like to emphasize that Diazo-4-LiXer was designed and\nsynthesized entirely based on our own above experience and design strategy, not from reports on\ndiazo functional group-based crosslinkers.)\n3. Development of an RIE-Free Process: During the manuscript revision stage, we were challenged\nto eliminate the RIE step due to concerns over potential damage to underlying functional layers.\nAttempts to dilute the PR solutions with various solvents did not yield satisfactory high-resolution\nPR patterns, despite extensive screening of commercial PRs. Fortuitously, we connected with a\n13\nmanaging director at Dongjin Semiconductor, who generously provided several PR samples.\nIncorporating one of these PRs into our process enabled the desired high-fidelity patterning, thereby\ncompleting a fully RIE-free PIN photopatterning protocol. The finding of an RIE-Free process took\nus more than ayear, which is why the submission of our revised draft took more than an year.\nIn conclusion, while our method may appear conceptually simple, it is the result of rigorous\nexperimental design and systematic troubleshooting. We are now confident that our process is\nnot only effective but also robust, scalable, and compatible with industrial photolithography\nplatforms.\n14\n[Comment 2-1] The authors' strategy of achieving QD patterning via photoresist-assisted lithography\nis relatively conventional. Introducing photo- or thermosensitive molecules while still relying on\nphotoresist renders the approach redundant. According to the authors, the designed molecule itself\nenables direct patterning without the need for photoresist, suggesting that reintroducing photoresist\nadds unnecessary complexity and cost, without offering clear technical advantages.\n[Response] Reviewer #2 pointed out that Diazo-4-LiXer enables direct photopatterning without the\nuse of a photoresist, and thus questioned the rationale for incorporating a photoresist in the PIN\nphotopatterning process, suggesting that it adds unnecessary complexity and cost without clear\ntechnical advantages.\nWe acknowledge the benefits of direct photopatterning in terms of process simplicity and cost\nefficiency. In fact, we were initially captivated by these advantages ourselves, which led us to develop\nand publish several studies based on direct photopatterning strategies. However, through extensive\nexperimentation and critical evaluation, we have identified intrinsic limitations of direct\nphotopatterning that constrain its applicability, particularly in achieving high pattern fidelity\nand reliable vertical profiles—issues that become increasingly significant for multilayer device\nintegration. For example, as discussed in the Introduction and further illustrated in Figures R2.1,\nR2.2, and R2.3 (as well as in the direct photopatterning data included in the current manuscript),\nthe patterns formed via direct photopatterning often exhibit slanted sidewalls and rounded edges.\nThese geometrical limitations hinder precise layer stacking and can compromise device performance.\nIt should also be considered that the achievable thickness of the QD pattern is inherently limited for\ndirect photopatterning, since it is a good UV absorber. The PIN photopatterning method described in\nthe manuscript directly addresses these limitations.\nFigure R2.1 (from our previous work reported in Adv. Mater. 2022, 34, 2205504). B) height\nprofiles of green-emitting InP/ZnSeS QD line patterns crosslinked with 1 wt% of 2-LiXer, IP-4-LiXer,\nand IP-6-LiXer. Both width and spacing of the line patterns are 2 μm. C) Schematic of a line pattern\nwith physical parameters denoted. D) Averaged line edge roughness (left), line width variability\n(middle) and side wall angle (right) of the QD line patterns prepared with 1 wt% of 2-LiXer, IP-4-\nLiXer, and IP-6-LiXer. The data are averaged from more than five samples prepared separately. The\n15\nerror bar represents the standard deviation of the data.\nFigure R2.2 (from our previous work reported in Nat. Commun. 2020, 11, 2874). Optical and\nfluorescence images of QD patterns. Optical and fluorescence (inset) microscopic images and AFM\nimages with height profile of (a) dot (diameter = 2 μm, spacing 3 μm) and (b) line patterns (width = 3\nμm, spacing 4 μm) based on 13-nm sized red-emitting CdSe/CdZnS QDs.\nFigure R2.3 (from our previous work reported in Adv. Optical Mater. 2022, 2200456, Figure f).\nHeight profiles of the Orange PPV patterns crosslinked using 1.0 wt% crosslinkers.\nTo explicitly compare the effectiveness of direct photopatterning and PIN photopatterning,\nwe performed patterning experiments using the same QD material and the same crosslinker for both\nmethods. As shown in Figure 2 of the manuscript, direct photopatterning yields patterns with\nsignificantly lower fidelity compared to those obtained via the PIN photopatterning process.\nWhile the PIN approach involves additional processing steps and associated costs, these are amply\njustified by the substantial improvements in pattern quality and the reliable preservation of QD optical\nperformance.\nOverall, we consider that the additional complexity and cost associated with using a\nphotoresist, as pointed out by Reviewer #2, are not prohibitive and can be well justified by the\nsignificant enhancement in pattern quality achieved through the PIN photopatterning process.\n16\n[Comment 2-2] The molecular structure reported in the manuscript has already been disclosed in\nprevious literature. Similar systems have been presented by the Luscombe group in ACS Nano (2024,\n18, 15915), and by Prof. Wenming Su in a 2022 patent (CN 114478306 A). Thus, the reported\nmolecular design lacks structural novelty.\n[Response] We appreciate the comments regarding the structural novelty of Diazo-4-LiXer, as\ndiscussed in ACS Nano (2024, 18, 15915) and in the 2022 patent (CN 114478306 A). We also became\naware of these references during the course of our manuscript revision.\nWhile we acknowledge that crosslinkers bearing a diazo functional group have been previously\nreported, the central contribution of our work lies not in the molecular structure alone, but in the\nprocess-level innovation that enables a long-standing goal in the field: achieving high-resolution\nQD patterning while preserving QD performance under industry-compatible fabrication\nconditions. Additionally, we present, for the first time, model compound experiments that\nevaluate the thermal reactivity of the diazo group, a crosslinkable chemical unit in the Diazo-4-\nLiXer, with linear aliphatic chains corresponding to the ligand and quantify the corresponding\nreaction yields. These results provide valuable mechanistic insights and practical design\nguidance for future development of diazo-based crosslinkers.\nTaken together, while the diazo motif itself may not be structurally unprecedented, we believe that\nthe combination of novel molecular architecture, thorough characterization, and functional\nvalidation in a practically relevant device-processing context constitutes a meaningful and\noriginal contribution to the field.\nWe also provide a comparative analysis between our current work and the two prior studies\nreferenced by the reviewer.\nBelow, we outline the major differences between our manuscript and the work published in ACS\nNano 2024, 18, 15915:\n(1) The ACS Nano study does not present any experimental data on thermal crosslinking. Our\nmanuscript, by contrast, demonstrates efficient thermal crosslinking of QD films at relatively low\ntemperatures (110–120 °C), which is a key requirement for enabling the PIN photopatterning process.\nTo the best of our knowledge, no prior study has demonstrated QD patterning via thermal crosslinking\nunder such mild conditions.\n(2) According to Figure S15 in the ACS Nano paper, the QD films crosslinked and patterned using X9\nexhibit significant electrical degradation. Each step in the device fabrication process reportedly\nresulted in further performance loss (see our Figure R2.4 for direct comparison). While X9 appears to\nbe a suitable crosslinker for materials like TFB, it does not preserve the electrical properties of QD\n17\nlayers. In contrast, our work demonstrates that R/G/GB QD layers retain excellent electrical\nperformance even after undergoing crosslinking and patterning.\nFigure R2.4 (Figure S15 in ACS Nano 2024, 18, 15915). EL characteristics of QLEDs cross-linked\nwith X9.\n(3) The QD patterns shown in the ACS Nano study exhibit substantially lower fidelity compared to\nthose presented in our manuscript. This discrepancy arises from their use of direct photopatterning via\nphoto-crosslinking, which—as discussed earlier—suffers from limitations in pattern fidelity and\nvertical definition. Moreover, the minimum achievable feature size in the ACS Nano study is ~4 μm\n(Figure R2.5), whereas our PIN photopatterning approach achieves high-fidelity patterns with feature\nsizes down to 1 μm (Supplementary Fig. 42).\nFigure R2.5 (Figure 6d in ACS Nano 2024, 18, 15915). Fluorescence and AFM (inset) images with\na height profile of the line with a width of 4 μm.\nlinewidths fabricated using stepper-based PIN photopatterning. a, Optical microscope image\nshowing uniform 0.8 μm-wide QD line patterns. b, AFM image of the 0.8 μm QD lines. c,\nQuantitative analysis of LER, l-LWR, and v-LWR of the patterned QD lines.\nBelow, we outline the major differences between our manuscript and the work published in CN\n114478306 A patent.:\n(1) The patent primarily describes three-branched diazo crosslinkers. Although a four-branched diazo\ncrosslinker is briefly mentioned in the text, only three-branched structures are disclosed and\ncharacterized in the experimental section. In contrast, our study is the first to report the synthesis and\nfull characterization of a four-branched diazo crosslinker, Diazo-4-LiXer.\n(2) The patent states that the diazo group can be activated by either UV or heat but does not present\nany experimental data demonstrating thermal crosslinking. Our manuscript, on the other hand,\nprovides clear experimental validation of thermal crosslinking at relatively low temperatures (110–\n120 °C), which is a key enabling feature for the PIN photopatterning process.\n(3) The patent focuses exclusively on the crosslinking of hole-transporting polymer layers. It does not\naddress QDs or their patterning. In contrast, our work is centered on achieving high-resolution\npatterning of QD layers while maintaining their optical and electrical properties—an application not\ncovered by the patent.\nTo clearly highlight our work’s novelty compared to the two references cited by the Reviewer #2,\nwe have included a comparative table below summarizing the key differences between our work,\nACS Nano (2024, 18, 15915), and patent CN 114478306 A.\nTable R1. Comparison of important features between the cited references and our work\nResults of Minimum\nChemical LER l-LWR v-LWR PLQY\nCrosslinking Host thermal pattern\nstructures of (basis) (basis) (basis) changes of Ref.\ncondition materials crosslinking width\ncrosslinkers QDs\nstudies nm nm nm µm\n3-Bridged HTL (TFB)\n(Only the PL ACS Nano\nUV Diazo and\nN/A N/A N/A N/A 4 intensity 2024, 18,\n(365 nm) Crosslinker QD (Red and\nwas 15915\n(X9) Green)\nreported)\nN/A\n3 or 4-Bridged (Thermal\nDiazo crosslinking\nCrosslinker was\nUV Patent\n(Only 3- mentioned\n(365 nm) CN\nbridged HTL (TFB) just as a N/A N/A N/A N/A N/A\nor 114478306\nstructures are possibility.\nHeat A\nincluded in the No thermal\nexperimental experiments\nexamples) were\nconducted)\n~1%\ndecrease\n(PLQY of\nred CdSe)\n4-Bridged ~1%\n40.0 55.8 121.3\nHeat\nDiazo QD (Red, decrease\nYes, (or (or (or 2 This\n(110 or\nCrosslinker Green, and (PLQY of\nprovided 45.9*) 75.8*) 124.3*) (or 0.8) work\n120 °C) (Diazo-4-\nBlue) green InP) (3σ) (3σ) (3σ)\nLiXer) ~7%\ndecrease\n(PLQY of\nBlue\nZnSeTe)\n* This value was obtained from QD patterns prepared using an i-line stepper. Other values with no\nasterisk (if not mentioned specifically) were obtained from QD patterns prepared using a mask aligner.\nIn conclusion, the unique property of Diazo-4-LiXer—its ability to enable thermal crosslinking\nat low temperatures (110–120 °C)—has not been specifically exploited for QD patterning in either of\nthe two references cited by Reviewer #2. To the best of our knowledge, there are no prior reports\ndemonstrating QD patterning via thermal crosslinking under such mild conditions. Our\nmanuscript is the first to introduce a patterning strategy—PIN photopatterning—that leverages\nlow-temperature thermal crosslinking to achieve record-high pattern fidelity, while fully\npreserving the optical and electrical performance of the QDs. Therefore, we respectfully argue that\nthe novelty of our work is not diminished by the existence of related diazo-based crosslinkers.\n20\n[Comment 2-3] Although the authors present data for 1 μm patterns, this cannot be considered a valid\nmeasure of lithographic resolution. In standard lithographic evaluation, equal line/space patterns (e.g.,\n1 μm lines with 1 μm spacing) are used to avoid misinterpretation due to over- or underexposure.\nFurthermore, the pattern edge roughness and surface roughness in Figure 42 appears inconsistent with\nthat in Figures 2a and 2e.\n[Response] We appreciate the reviewer’s comments regarding the criteria for evaluating lithographic\nresolution. As described in the Introduction of the manuscript, the primary application target of\nour work is high-resolution microdisplays, such as those used in VR/AR devices, which require\npixel densities exceeding 3000 PPI to eliminate the screen door effect. With our demonstrated\n2 μm patterning, we have already achieved RGB QD pixel arrays corresponding to pixel densities\nover 4000 PPI—well beyond the requirements for the intended application. Therefore, a 1 μm\npattern was not included in the original submission, as it was not essential for the scope of our work.\nIt was added during the first revision solely in response to a reviewer’s suggestion.\nGiven this context, we considered that it is not critical for the 1 μm pattern to serve as a rigorous\nbenchmark of lithographic resolution or fidelity. Realistically, the fabrication of sub-2 μm patterns in\nour laboratory was inherently limited by the capabilities of our mask aligner system, which is\noptimized for ≥2 μm resolution.\nNevertheless, to address the reviewer request, we sought external assistance to perform patterning\nusing a stepper-based photolithography system. Although we were unable to fabricate ideal equal\nline/space patterns due to the lack of a suitable photomask, we note that for sequential RGB\npatterning—as would be implemented in practical display applications—the line-to-space ratio\nis not 1:1 but closer to 1:3 for each color QD patterns. Using the available mask, we have now\nsuccessfully fabricated 0.8 μm-wide QD patterns and confirmed that their shape fidelity is comparable\nto that of our original 2 μm features. Accordingly, we have replaced the previous Supplementary\nFigure 42 with the updated results obtained via stepper lithography, which more clearly demonstrate\nthe sub-micrometer patterning capability and high fidelity of our PIN photopatterning process.\nSupplementary Fig. 42. Characterization of green-emitting InP/ZnSeS QD patterns with 0.8 μm\nlinewidths fabricated using stepper-based PIN photopatterning. a, Optical microscope image\n21\nshowing uniform 0.8 μm-wide QD line patterns. b, AFM image of the 0.8 μm QD lines. c,\nQuantitative analysis of LER, l-LWR, and v-LWR of the patterned QD lines.\nIn the revised manuscript, we added “For example, when an i-line stepper instead of a mask aligner\nwas used, QD patterns with 0.8 μm feature sizes with excellent pattern shape fidelity could be\nsuccessfully attained. (See Supplementary Note 3 and Supplementary Fig. 43)” We also modified\nour discussion in Supplementary Note 3 as follows: Considering that the resolution of the QD patterns\nin PIN photopatterning is inherently limited by that of the PR patterns, submicron QD features can be\nachieved using a UV exposure system that meets the required specification. For instance, when an i-\nline stepper (Nikon NSR2205i11D) was employed, G-QD patterns with feature sizes as small as 0.8\nμm were successfully obtained, exhibiting LER, l-LWR, and v-LWR comparable to those reported in\nthe main text (Supplementary Fig. 43). In contrast, the minimum feature size attainable with our mask\naligner (MD-400LJ, Midas system) was 2 μm. This value corresponds to the resolution limit for our\nmask aligner in a hard contact.\n[Comment 2-4] To support the claimed advantages of the PIN method, the authors present a control\nexperiment showing poor performance in direct optical patterning. However, this result differs\nsignificantly from previously reported strategies, such as in Nature Nanotechnology (2022, Fig. 3a),\nand no explanation is provided for the discrepancy. This undermines the credibility of the comparative\nassessment.\n[Response] We thank the reviewer for this important point. The comparison shown in Figure 2\nwas specifically designed to isolate the effect of the patterning strategy—using the SAME diazo-based\ncrosslinker—so as to fairly evaluate the impact of direct photopatterning versus our PIN method under\ncontrolled conditions. The intent was not to compare with all existing methods, but to focus on a\ncontrolled side-by-side comparison of the two approaches using identical chemistry.\nIn addition to the comparative analysis, we have also compiled and included an extended\ncomparison in Supplementary Table 4, where the pattern fidelity of our approach is evaluated against\nthe results from Nature Nanotechnology (2022, Fig. 3a). This comparison confirms that our PIN\nstrategy provides superior pattern fidelity relative to these methods. As we emphasize throughout\nthe manuscript, this improvement arises from the use of pre-patterned high-resolution PR templates,\nwhich serve as precise structural guides for QD patterning. This structural confinement leads to much\nsharper and more defined patterns than those typically achievable through direct photopatterning alone.\nMinimum Industrial\nLER LWR\nDecrease of Decrease of Pattern compatibility\nRef. (nm) (nm)\nPLQY EQE Size (Crosslinking\n(basis) (basis)\n(µm) condition)\nNearly identical 297 Good\nNat. Nanotechnol. 2022, ~2% 222\n(Only EQE plot 0.8 (3σ) (365 nm UV for\n17, 952-958 (green InP) (3σ)\nreported) (l-LWR) crosslinking)\n55.8\n(or 75.8*)\n40.0 (l-LWR) Good\n~1% 2 121.3\nThis work Nearly identical (or 45.9*) 124.3*) (Low temp.\n(green InP) (or 0.8*) (or\n(3σ) crosslinking)\n(v-LWR)\n(3σ)\n* This value was obtained from QD patterns prepared using an i-line stepper. Other values with no\nasterisk (if not mentioned specifically) were obtained from QD patterns prepared using a mask aligner.\n[Comment 2-5] The authors argue that traditional azide and diazirine-based thermosensitive\ncrosslinkers operate at excessively high temperatures, affecting compatibility with PIN lithography.\nThis claim is not well supported. For example, ACS Nano (2022, 16, 13674–13683) demonstrates that\nthese agents do not exhibit notably higher crosslinking temperatures. Moreover, high-temperature\nprocessing is not necessarily problematic; optimization through alternative photoresists or\nphotocrosslinking techniques can readily mitigate this issue—especially considering that Diazo-4-\nLiXer itself is photosensitive.\n[Response] We appreciate the comment and the reference to ACS Nano 2022, 16, 13674–13683. Upon\ncareful review of this work, we note that Figure 2a of the cited paper clearly shows that the thermal\nactivation of the azide-based crosslinker begins at approximately 140 °C. This observation is consistent\nwith our own experimental findings (Figure R2.6). However, such temperature presents a critical\ncompatibility issue in the context of our PIN photopatterning strategy. As shown in Figure 1d of our\nmanuscript, annealing at 140 °C induces substantial changes in the underlying PR layer. These changes\nlead to severe processing problems, including incomplete PR development and residual PR films that\ncannot be cleanly stripped. Consequently, this temperature is incompatible with commonly used\ncommercial PR systems and prevents clean pattern formation.\nIn this regard, the 30 °C difference between the crosslinking temperature of BisPFPA (~140 °C)\nand that of Diazo-4-LiXer (110–120 °C, as used in our work) is not a trivial matter—it is essential\n23\nfor maintaining the processability and integrity of the overall photopatterning workflow. The mild\ncrosslinking conditions enabled by Diazo-4-LiXer are a key advantage, as they allowed us to\nretain the integrity of both the PR and QD layers without compromising resolution or fidelity.\nTherefore, our claim that traditional azide-based crosslinkers require higher crosslinking\ntemperatures is well supported by both literatures and our experimental data, and this\ntemperature incompatibility is a critical obstacle for the practical implementation of PIN\nphotopatterning. The low-temperature thermal crosslinking capability of Diazo-4-LiXer directly\naddresses this challenge and is thus a central feature of our process innovation.\nFigure R2.6 Thermogravimetric analysis of azide-based crosslinker ehylene bis(4-azido-2,3,5,6-tetra-\nfluorobenzoate (a) reported in the literature (Fig. 2a of ACS Nano (2022, 16, 13674–13683) and we\nobtained from experiment.\nIn addition, the use of BisPFPA as described in ACS Nano (2022, 16, 13674–13683)—as well as\nother azide-based crosslinkers we previously developed—requires prolonged thermal annealing at\n140 °C for over 1 hour (typically ~3 hours) on a hot plate to achieve sufficient crosslinking. Such\nextended high-temperature processing is not desirable for industrial production. We also acknowledge\nthat the ACS Nano paper explored the use of laser-assisted localized heating to induce thermal\ncrosslinking of BisPFPA. However, this approach introduces several limitations: (1) laser systems are\nsignificantly more expensive and complex than standard thermal ovens, and (2) as shown in Figure 4\nof the cited paper, laser-induced crosslinking at 140 °C leads to a clear degradation in the\nphotoluminescence quantum yield (PLQY) of the QDs. In contrast, our diazo-based four-branched\ncrosslinker, Diazo-4-LiXer, enables efficient thermal crosslinking and high-fidelity QD pattern\nformation at a significantly lower temperature of 110 °C. Importantly, this is achieved without any\ndegradation in the luminescent or electrical performance of the QDs. This combination of low-\ntemperature processing, high pattern fidelity, and preservation of QD properties offers a clear\n24\nadvantage in terms of scalability and industrial relevance.\nFigure R2.7 (Figure 4 in ACS Nano 2022, 16, 13674−13683). PL characteristics of TALC-patterned\nQD films. (a) PL spectra of pristine (solid) and patterned (dashed) QD films with blue, green, and red\nemission. (b) Comparison of PLQYs (relative to the pristine sample) after different treatments in TALC,\nincluding films at pristine (original, pure QDs), formulation (QDs+bisPFPA, prior to laser treatment),\nlaser-treated, and developed stages. (c) Corresponding PL decay curves of samples in (b). (d)\nFluorescence microscopic images of line patterns of QDs via TALC and associated relative PL\nintensity profiles, showing high contrast in PL intensity between regions with and without QDs.\nWhile we agree that exploring alternative PR formulations could be viable in some cases, we were\nunable to identify commercially available PR materials that could withstand thermal annealing at\n140 °C without undergoing chemical changes that interfere with development or stripping. Our goal\nwas to develop a universally compatible and scalable process using standard PR materials and process\ntemperatures. Achieving crosslinking at lower temperatures was therefore essential, and this is\nprecisely why we selected a diazo-functionalized ligand that enables efficient thermal crosslinking at\n~110 °C—safely below the threshold that affects the PR integrity. Therefore, the low-temperature\nreactivity of Diazo-4-Bx was crucial to the success of the PIN process, ensuring compatibility\nwith PR-based lithography without compromising QD performance.\n25\n[Comment 2-6] The QLED device used for performance comparison exhibits inferior metrics relative\nto state-of-the-art devices reported in literature (Fig. 4h and Supplementary Fig. 47). Using such a low-\nperformance reference undermines the argument for practical applicability. Benchmarking against\nadvanced QLED architectures is necessary to convincingly demonstrate the method’s real-world\npotential.\n[Response] We appreciate the comment regarding the relatively modest QLED performance metrics\npresented in our manuscript. However, we respectfully note that the primary objective of this study is\nnot to achieve record-breaking QLED device performance, but rather to introduce and validate a new\nQD patterning strategy—PIN photopatterning—that enables high-resolution, high-fidelity pattern\nformation while preserving the intrinsic optical and electrical properties of the QD emitters. Therefore,\nwe believe that the demonstrated device performance, although not at the state-of-the-art level, falls\nwell within the functional range and is sufficient to establish the practical feasibility of our patterning\nprocess. In particular, the electroluminescence data confirm that our method supports multicolor,\noperational QD-LED fabrication without performance degradation during crosslinking or patterning,\nwhich directly supports our central claims.\nTo provide further context, we have compiled a summary (Table R2) of reported QLED\nperformances from leading journals that employed various crosslinking strategies. Our device\nefficiencies are comparable to or exceed those reported in many of these studies, suggesting that\nour results are not unusually low, particularly given the early-stage and platform-level nature of\nour contribution.\nAdditionally, we would like to share that we have had recent technical discussions with major\ndisplay industry leaders, including Samsung Display (Feb. 13, 2025) and Samsung Electronics\n(June 19, 2025). Both teams expressed strong interest in our PIN photopatterning approach and did\nnot raise concerns regarding device performance. In fact, our earlier work (Adv. Mater. 2022, 34,\n2205504) reported even lower EQE values (<10%) yet led to a successful technology transfer to\nSamsung Electronics. In that case, as with our current work, the value of the contribution was\nrooted not in record-breaking efficiency, but in the conceptual advancement of the patterning\nmethodology.\nFinally, we would like to emphasize that impactful scientific contributions are not always\ndefined by peak performance at the time of publication. Our 2020 Nature Communications study\non direct photopatterning, for example, reported relatively modest device efficiencies, yet has since\nbeen cited over 200 times and inspired a wide body of research on ligand-engineered photopatterning\nstrategies. We believe the present study offers a similarly novel and robust platform innovation—one\nthat enables high-resolution, scalable, and non-destructive patterning of QDs with strong potential for\n26\nreal-world applications.\nTable R2. Summary of QLED performance. We note that in much of the previous literature, parameters\nsuch as turn-on voltage (V ), maximum luminance (L ), and current efficiency are not quantitatively\non max\nprovided in the text, and only the J–V–L plots are reported. In such cases, we have marked them as\n“Only report J–V–L plot.”\nEL device Current\nCrosslinking Crosslinking Device V L\non max\nQD efficiency Maximum EQE Ref.\nstrategy condition structure (V) (cd/m2)\ncomposition (cd/A)\nCrosslinkable\nUV 9.5%\nligand Red CdZnSe Inverted 2.5 78821 13.036 R1\n(365 nm) (Patterned QD)\n(Diazirine)\nOnly Only\nCrosslinker UV report report Only report 9.73%\nRed CdZnSe Inverted R2\n(Thiol-ene) (365 nm) J-V-L J-V-L J-V-L plot (Crosslinked QD)\nplot plot\n22% (Red)\nOnly\nCrosslinkable UV Red, Green, (QDs are not\nreport Only report\nligand (254, 365, 405 Blue Conventional ~40000 crosslinked) R3\nJ-V-L J-V-L plot\n(Acrylate) nm) CdSe 14.4% (Green)\nplot\n11.4% (Blue)\n22.45% (Red)\nCrosslinker UV (QDs are not\nRed CdSe Conventional 2.23 29230 31.87 R4\n(Diazo) (365 nm) crosslinked)\n(Crosslinked HTL)\nOnly Only\nCrosslinkable UV report report Only report 8.3% (Green)\nGreen InP Conventional R5\n(Azide) (254 nm) J-V-L J-V-L J-V-L plot (Crosslinked QD)\nplot plot\nOnly Only ~20% (Red)\nCrosslinkable\nUV Red CdSe report report Only report (Crosslinked QD)\nligand Inverted R6\n(365 nm) Green CdSe J-V-L J-V-L J-V-L plot ~15% (Green)\n(Benzophenone)\nplot plot (Crosslinked QD)\nCrosslinkable 20.05% (Red)\nOnly\nligand (Crosslinked QD)\nUV report Only report\n& Red CdZnSe Conventional 166612 15.37% (Green)\n(365 nm) J-V-L J-V-L plot R7\nCrosslinker (Crosslinked QD)\nplot\n(Alkyne-azide) 8.49% (Blue)\n27\n(Crosslinked QD)\nOnly Only\nCrosslinker UV report report Only report 14.6% (Red)\nRed CdSe Inverted R8\n(Azide) (254 nm) J-V-L J-V-L J-V-L plot (Crosslinked QD)\nplot plot\nOnly\nCrosslinker UV report Not report\nGreen InP Conventional 8463 23.04 R9\n(Thiol-ene) (365 nm) J-V-L (Crosslinked QD)\nplot\n39590\n20.2\n(Crossli\n(Crosslinke 15.3% (Red)\n2.1 nked\nCrosslinker UV d QD) (Crosslinked QD)\nRed, Green InP Conventional (Pattern QD) R10\n(Diazirine) (365 nm) 20.8 13.3% (Red)\ned QD) ~4000\n(Patterned (Patterned QD)\n(Pattere\nQD)\nnd QD)\nOnly Only\nCrosslinkable\nUV report report Not report\nligand Red InP Inverted 4.3 R11\n(254 nm) J-V-L J-V-L (Crosslinked QD)\n(Azide)\nplot plot\nPhotoacid\nUV 5.08% (Green)\ngenerator Green CdSe Inverted 3.0 ~22500 13.0 R12\n(365 nm) (Crosslinked QD)\n(MBT)\nOnly Only\nPhotocleavable UV report report Only report\nGreen InP Conventional Not report R13\nQD ligand (275 nm) J-V-L J-V-L J-V-L plot\nplot plot\n13649 21.0 19.1% (Red)\nOnly (Red) (Red) (Crosslinked QD)\nUV Red, Green, report 56918 98.0 17.5% (Green)\nLigand exchange Conventional R14\n(254 nm) Blue CdZnSe J-V-L (Green) (Green) (Crosslinked QD)\nplot 4294 7.9 12.0% (Blue)\n(Blue) (Blue) (Crosslinked QD)\nPhotosensitizer Only\ninduced HTL UV Red CdSe QD report Only report 16.25% (Red)\nConventional 146413 R15\npolymer (365 nm) + TFB J-V-L J-V-L plot (Patterned QD)\ncrosslinking plot\nCrosslinker UV Only Only Only report 11.7% (Red)\nRed CdSe Conventional R16\n(Diazirine) (365 nm) report report J-V-L plot (Crosslinked QD)\nplot plot\n16.8% (Red)\nCrosslinker UV Not\nRed QD Conventional 2.0 22.7 (QDs are not R17\n(Diazo) (365 nm) report\ncrosslinked)\n16.6% (Red)\nOnly Only (Crosslinked QD)\nRed CdSe Only\nHeat\nCrosslinker report report 7.0% (Green)\nGreen InP Inverted report\n(Diazo) (110 °C) J-V-L J-V-L (Crosslinked QD) This\nBlue ZnSeTe J-V-L plot\nplot plot 3.7% (Blue) work\n(Crosslinked QD)\nR1: ACS Nano 2025, 19, 22253–22261\nR2: Nano Letters ASAP. https://doi.org/10.1021/acs.nanolett.5c01926\nR3: ACS Nano 2025, 19, 14509–14520\nR4: ACS Nano 2024, 18, 15915–15924\nR5: Adv. Mater. 2022, 34, 2205504.\nR6: Nat. Nanotechnol. 2022, 17, 952–958.\nR7: Adv. Funct. Mater. 2025, 2420829.\nR8: Nat. Commun. 2020, 11, 2874.\nR9: Small Method 2023, 7, 2300206.\nR10: J. Am. Chem. Soc. 2024, 146, 42, 28895–28905.\nR11: Chem. Mater. 2025, 37, 1424–1431.\nR12: Adv. Mater. 2020, 32, 2003805.\nR13: ACS Energy Lett. 2025, 10, 94–101.\nR14: Nano Lett. 2023, 23, 5, 2000–2008.\nR15: Nano Lett. 2024, 24, 4, 1254–1260.\nR16: Angew. Chem. Int. Ed. 2022, e202202633\nR17: Patent CN 114478306 A\n29\n[Comment 2-7] In the construction of full-color QD patterns, the authors fail to assess how residual\nphotoresist may affect adjacent pixels. For instance, in Figure S43, green QD regions still contain\nphotoresist residues during red QD patterning. This could significantly compromise green QLED\nperformance, yet the manuscript does not provide any discussion or data on this issue.\n[Response] We thank the reviewer for pointing out this concern. However, we believe this is due to a\nmisunderstanding of the patterning sequence illustrated in Figure S43. The PR visible above the\ngreen QD regions during the red QD patterning step is not a residual artifact from the green QD\nprocess, but rather a newly applied photoresist layer intentionally introduced for the second round\nof PIN photopatterning. This resist layer is part of the standard patterning protocol to define the red\nQD regions, and it does not interfere with the green QDs, as it is completely removed during the\nsubsequent stripping step (please refer to Fig. 3e and revised Supplementary Fig. 43).\nTherefore, no residual photoresist remains on or near the green pixels in the final device, and there\nis no cross-contamination or optical/electrical degradation introduced as a result of the multistep\npatterning process (please refer to Fig. 3f and 3g as well as Fig. 4g and 4h).\nSupplementary. Fig. 44. Schematic description of successive G/R QD patterning process via PIN\nphotopatterning. Note that the PR layer introduced in (6) on top of the G-QD patterns are not a\nresidual artifact from the previous G-QD patterning process, but rather a newly applied PR layer\nintentionally introduced for the second round of PIN photopatterning. This resist layer is part of the\nstandard patterning protocol to define the R-QD regions.\nWe have now clarified this sequence in the revised figure. We also added a short note in the caption to\navoid similar confusion.\n[Comment 2-8] To fabricate full-color QLEDs using the proposed method, multiple lift-off steps are\nrequired. These processes may damage previously deposited layers, such as organic charge transport\n30\nlayers, potentially impacting overall device integrity. However, the authors provide no experimental\nvalidation addressing the structural or functional robustness under repeated processing.\n[Response] We thank the reviewer for raising this important point. We totally agree that while our\ncurrent manuscript focuses primarily on the patterning of QD layers, the integrity of underlying\nlayers—particularly those exposed to multiple photolithographic steps—is an essential consideration\nfor practical device fabrication.\nWe note, however, that in our specific device structure, the layer beneath the patterned QD film\nis not an organic charge transport material, but rather a robust inorganic ZnMgO NP layer.\nAlthough we did not conduct an in-depth analysis of previously deposited layers beyond the QDs,\nwe performed a preliminary evaluation of the ZnMgO layer robustness under repeated PIN\nphotopatterning cycles. As shown in Figure R2.8, AFM images depict the surface morphology of the\nZnMgO NP layer before and after undergoing one and three full rounds of photoresist coating,\ndevelopment, and lift-off processing. These images reveal no discernible degradation or roughening\nof the ZnMgO surface, indicating that the layer remains structurally intact even after multiple\npatterning cycles. This suggests that, under the process conditions employed in our study, the\nconcerns raised by the reviewer are not manifested as significant damage in practice.\nWe fully agree that if the device were to adopt a normal architecture—in which organic charge\ntransport layers reside beneath the QD layer—the risk of damage from multiple processing steps would\nbe more critical. However, even in such cases, viable mitigation strategies exist. In particular, it is well\nestablished that organic semiconductors can be chemically crosslinked to enhance their mechanical\nand chemical robustness Once crosslinked, these materials can withstand subsequent solution\nprocessing steps, including photolithography, sonication, development, and lift-off, without structural\nor functional degradation. We and many others have previously demonstrated this approach in the\ncontext of polymer semiconductors for transistors and OLEDs, as well as in small-molecule systems\nfor organic light-emitting devices (please refer to our previous publications: Small Molecules: Light:\nSci. Appl. 2025, ASAP; Small Methods 2025, 2401719; Polymer Semiconductors: Adv. Opt. Mater.\n2022, 10, 2200456; ACS Photonics 2021, 8, 2519-2528; Nat. Commun. 2020, 11, 1520; ACS Nano\n2024, 18, 21957-21965). While our current study does not directly include validation experiments for\ncrosslinked organic transport layers, we believe that the reviewer’s concern can be effectively\naddressed by incorporating such strategies in future implementations, particularly for normal-\nstructured devices. Thus, we consider the issue valid but manageable, and we are confident that the\nPIN photopatterning method remains broadly applicable across different device architectures.\nPIN photopatterning process.\nRegarding this comment, we added “The well-preserved device characteristics can be attributed not\nonly to the intrinsic PL properties of the QDs being maintained throughout the PIN photopatterning\nprocess (Fig. 4c), but also to the sufficient robustness of the underlying ZnMgO NP layer against the\nsequential processing steps involved in PIN photopatterning (Supplementary Fig. 49).” in the revised\nmanuscript. The data in Figure R2.8 is included in the revised manuscript as Supplementary Fig. 49.\n32"}]

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