Polymerization‐Induced Direct Photolithography of Quantum Dots

ABSTRACT

The development of high‐resolution displays has driven the exploration of quantum dot (QD)‐based patterning techniques, ranging from inkjet printing to direct photolithography. Among these methods, direct photolithography stands out as a promising technique for creating high‐resolution QD patterns without the need for a photoresist layer. This approach relies on photochemical reactions that induce solubility changes in target materials when exposed to specific wavelengths of light. While various patterning strategies have been reported, polymerization‐induced network formation offers a straightforward yet effective approach for fabricating QD patterns, simultaneously inheriting the advantageous physical and chemical properties of polymers. This review categorizes and discusses the photochemical reactions that enable polymerization according to their underlying mechanisms. Recent examples utilizing these reactions for direct photolithography of QDs are classified and summarized based on reactive functional groups—alkene, alkane, alkyne, and disulfide—involved in the polymerization process. Finally, we propose future directions for advancing this technology, including improvements in material compatibility, device integration, and the introduction of new functionalities, which could further expand the potential applications of QD‐based optoelectronic devices.

We present a comprehensive overview of photochemical polymerization strategies for direct lithographic patterning of colloidal quantum dots (QDs). Reaction mechanisms are categorized by functional group type, and their application is discussed in terms of pattern fidelity, photostability, and environmental robustness, highlighting the potential of polymer‐based approaches for high‐resolution, solution‐processable QD architectures in next‐generation optoelectronics.

1. Introduction

With the rapid expansion of high‐resolution display markets and the advancement of next‐generation optoelectronic applications, colloidal quantum dots (QDs) have become indispensable materials due to their exceptional optical tunability, narrow emission bandwidth, and high photoluminescence quantum yield (PLQY) [1, 2, 3, 4, 5]. Their compatibility with solution‐based fabrication also enables scalable and low‐cost manufacturing, supporting applications in both large‐area and flexible electronics. These properties have driven the adoption of QDs in various display architectures, including QD‐enhanced liquid crystal displays (QD‐LCDs) and electroluminescent QD displays [6, 7, 8, 9].

In early display configurations such as QD‐LCDs, red and green QDs are dispersed uniformly within polymer films that are placed in front of blue LED backlights [10, 11, 12]. This down‐conversion approach significantly enhances color gamut and purity, but since all subpixels are illuminated by a shared backlight, pixel‐level patterning of QDs is not required. These unpatterned QD films, while effective, suffer from spectral cross‐talk caused by unwanted Förster resonance energy transfer, particularly between green and red QDs, which can broaden and redshift emission spectra [13, 14]. Moreover, the underlying limitations of LCDs—such as low contrast ratios, narrow viewing angles, and the reliance on color filters—remain unresolved.

To address these issues, hybrid QD‐OLED displays were introduced. In this configuration, a blue OLED serves as the excitation source, while red and green QDs are selectively deposited to form QD color converters for each subpixel [15, 16, 17]. This architecture requires spatially resolved QD layers, and in commercial displays, inkjet printing has been adopted to deposit red and green QDs directly onto designated subpixels. This arrangement offers improvements in optical efficiency, color accuracy, and subpixel alignment over conventional OLEDs with organic color filters. However, QD‐OLEDs still inherit the material instability of OLEDs, particularly the rapid degradation of blue emitters under high luminance conditions, leading to limited operational lifetime and persistent image retention artifacts [18, 19].

Fully electroluminescent QD displays (QD‐ELs) have emerged as a promising alternative by positioning QDs as the active emissive material [20, 21, 22]. This architecture eliminates the need for external light sources and intermediate layers, enabling advantages such as ultra‐high contrast, wide viewing angles, and integration into thin and flexible form factors. Despite these benefits, QD‐ELs face several key challenges—including limited charge injection efficiency, unstable blue QDs, and difficulty in achieving high‐resolution RGB patterning essential for commercial full‐color display panels [23, 24, 25].

Particularly as display technologies advance toward ultra‐high resolution and extreme miniaturization, achieving precise QD patterning remains a critical bottleneck for the commercialization of self‐emissive QLEDs. The rapid evolution of extended reality (XR)—encompassing augmented reality (AR), virtual reality (VR), and mixed reality (MR)—has intensified the demand for advanced QD patterning techniques, as subpixel dimensions shrink to 2–3 µm or less. Unlike conventional displays, where larger subpixel pitches are acceptable, XR devices place displays in close proximity to the eye, necessitating exceptionally high pixel densities to avoid visible pixilation and preserve image fidelity. Patterned QDs are ideally suited for this purpose, offering narrow emission spectra, high brightness, and precise color control at the subpixel level. However, traditional deposition techniques such as inkjet printing and transfer printing often fall short in terms of resolution, film uniformity, and multicolor patterning precision. As a result, the development of high‐resolution, high‐fidelity QD patterning methods has emerged as a pivotal research focus in next‐generation optoelectronics.

The emergence of these new architectures has placed increasing emphasis on QD patterning technologies that allow precise, sub‐micrometer resolution while maintaining QD integrity. A variety of approaches have been developed to meet this need (Figure 1). Inkjet printing offers additive processing and direct pixel formation without masking steps, making it attractive for large‐area displays [26, 27, 28]. However, the low resolution of printed droplets and difficulties in controlling spreading behavior limit its scalability to microdisplays. Transfer printing enables accurate material placement and multicolor patterning but suffers from process complexity and scalability issues, especially in multilayered or flexible device integration [29, 30, 31]. Conventional photolithography delivers excellent resolution and alignment precision using photoresist and etching steps adapted from semiconductor processing [32, 33, 34]. However, these steps often involve solvents and thermal/chemical treatments that compromise the stability of QDs, damaging surface ligands and reducing PLQY [35, 36].

FIGURE 1.

Schematic illustrations of QD patterning techniques. (a) Inkjet printing, (b) transfer printing, (c) conventional photolithography, and (d) direct photolithography.

Among emerging patterning strategies, direct photolithography techniques have gained increasing attention for enabling pattern formation directly from QD‐containing films without relying on sacrificial resist layers or post‐etching [37, 38, 39]. These approaches typically involve modifying the QD layer itself—either chemically or physically—in a spatially controlled manner upon light exposure. By utilizing QDs as photosensitive materials, this approach simplifies the patterning process while minimizing the adverse effects associated with conventional lithographic techniques. Because direct lithography eliminates the use of photoresists, it avoids the pattern distortion often associated with traditional resist‐based approaches, enabling the formation of more uniform and precise patterns [40]. Importantly, this advantage extends beyond resolution at the microscale [41]. In the context of large‐area device manufacturing, direct lithography facilitates better pattern uniformity across wide substrates by reducing variability introduced during multistep processing [42, 43]. The simplified process flow and fewer material interfaces contribute to higher reproducibility and scalability, making direct lithography particularly attractive for applications such as large‐area displays or wafer‐scale integration of QD‐based components. Additionally, the absence of residual impurities helps preserve critical optoelectronic properties [44] such as charge carrier mobility, conductivity, and luminescent characteristics. Compared to traditional methods, direct photolithography offers enhanced resolution, improved process efficiency, and better QD material integrity, making it a promising strategy for next‐generation optoelectronics. Depending on the underlying mechanism, direct photolithography can proceed through ligand cleavage, phase transformation, or chemical crosslinking [44]. Each route offers distinct advantages in spatial resolution, process simplicity, and material compatibility.

Within this framework, polymerization‐induced direct photolithography has shown particular promise due to its compatibility with solution‐processed QDs and its ability to simultaneously immobilize materials and define high‐resolution patterns. This method utilizes light‐activated chemical reactions—such as radical polymerization, thiol‐based coupling, cycloaddition, or ring‐opening reactions—to construct crosslinked polymer networks directly from QD films or QD–polymer composites [38, 45, 46]. By incorporating photo‐reactive functional groups into QD surface ligands or matrix polymers, patterning and chemical fixation can be achieved in a single step, minimizing damage to QDs and simplifying processing [43].

Recent advances have demonstrated a wide range of photochemical reactions applicable to this direct photolithography approach, tailored to various ligand structures and photoinitiation conditions. These polymerization‐based methods not only support high‐fidelity patterning but also enhance the environmental stability and mechanical robustness of QD layers, aligning with the stringent demands of next‐generation displays. Motivated by these developments, this review provides a focused and mechanistic overview of polymerization‐enabled QD patterning strategies, with particular emphasis on the role of surface ligand design, photochemical reaction mechanisms, and their integration into direct photolithographic processes. Section 2 introduces the key classes of photoinduced reactions that enable the formation of crosslinked polymer networks compatible with QD systems. Section 3 highlights how these chemistries have been implemented in high‐resolution direct photolithography, evaluating their process compatibility, pattern fidelity, and implications for future optoelectronic device fabrication. Section 4 summarizes the advantages of polymerization‐induced direct photolithography and discusses future directions for its application in QD‐based optoelectronic devices.

2. Photochemical Reactions for Constructing Polymeric Networks

The use of light to drive the formation of polymeric materials represents a highly versatile and powerful strategy in polymer science, offering several unique advantages over other energy sources [47, 48]. At first, photoinitiation allows reactions that typically require high temperatures or harsh conditions to proceed rapidly at ambient conditions because the energy in a mole of photons at 365 nm is 130 times greater than the thermal energy (kT) at 25°C. This feature enables reaction mixtures to remain stable and unreactive under normal conditions until activated by specific wavelengths of light, thus providing precise temporal control simply by turning the illumination on or off. Second, reaction kinetics and duration can be easily adjusted by varying the irradiation power and exposure time, facilitating straightforward modulation of reaction conditions. Finally, photochemical reactions provide exceptional spatial control in noncontact and remote environments, as they can be selectively triggered in two or three dimensions through targeted or patterned illumination.

As described in the previous section, polymerization‐enabled direct photolithography offers a promising strategy for high‐resolution QD patterning, providing compatibility with solution‐processable materials and preserving QD optical properties [49]. Central to this approach are photochemical reactions that enable spatially controlled immobilization or solubility modulation of QD‐containing layers through light‐induced crosslinking or polymeric network formation. This section reviews the diverse classes of photochemical reactions—thiol‐based chemistry, free radical polymerization, cycloaddition, alkyne bridging, C─H insertion, and disulfide ring‐opening polymerization— hat have been adapted for such applications.

Thiol compounds, characterized by their relatively weak sulfur–hydrogen (S─H) bonds, readily undergo diverse chemical transformations under mild conditions. Among these, the thiol‐ene reaction represents one of the most extensively studied and widely applied photochemical processes (Figure 2a). Upon UV irradiation, the reaction proceeds through a radical‐mediated step‐growth mechanism, initiated by the addition of a thiyl radical to a carbon–carbon double bond to form a carbon‐centered radical intermediate. This intermediate subsequently abstracts a hydrogen atom from another thiol molecule, thereby regenerating the thiyl radical and forming a thioether linkage [50, 51]. A closely related reaction is the thiol‐yne reaction, which follows a similar radical addition pathway but involves an alkyne moiety. The alkyne undergoes two sequential additions with two thiol groups, where the first reaction with a single thiol forms a vinyl sulfide, followed by a subsequent reaction with a second thiol to yield 1,2‐disubstituted product (Figure 2b) [52].

FIGURE 2.

Diverse photochemical reaction pathways for constructing polymeric networks. (a) Thiol‐ene reaction. (b) Thiol‐yne reaction. (c) Free radical polymerization of alkenes and termination by combination. (d) Alkyne‐alkyne bridging. (e) [2+2] Cycloaddition of alkenes. C─H insertion via (f) benzophenone, (g) azide, and (h) azirine. (i) C─H Breakage and dehydrogenation. (j) Oxidation of dithiols to disulfide. (k) Ring‐opening polymerization of dithiolane.

Instead of thiol‐based additives, a photoinitiator can be introduced that undergoes homolytic cleavage to produce free radicals after light absorption. These free radicals attack a vinyl molecule, producing a carbon‐centered radical. Subsequently, this carbon‐centered radical propagates to other vinyl monomers and develops polymer chains via a chain‐growth process (Figure 2c). This chain‐growth reaction can be terminated either through the combination of two radicals to form an inactive species or through radical transfer to other molecules, which initiates the formation of a new reactive species [53]. Following a comparable mechanism, this free radical polymerization can be applied in the case of alkyne groups, as the free radical transfer breaks the π bond. Alkyne‐alkyne bridging reaction can also be proceeded with a similar mechanism, where free radicals generated from photoinitiator propagate the crosslinking between alkyne moieties (Figure 2d) [26]. In addition, alkenes can not only participate in polymerization but also undergo a [2+2] cycloaddition via a pericyclic reaction under UV irradiation. An initial π* excitation of alkene forms a complex with another ground‐state alkene, which determines the orientation in the final product. This exciplex collapses to a 1,4‐biradical structure, which can subsequently cyclize to form a cyclobutane structure (Figure 2e) [54, 55, 56].

Alkane groups, the most common type of hydrocarbon, exhibit much lower reactivity compared to alkenes as they consist solely of strong σ bonds. However, certain photoactive functional groups can induce C─H insertion reactions, making them useful for photocrosslinking in patterning processes. Notable examples include benzophenone, azide, and azirine groups. Benzophenone undergoes a transformation under UV irradiation where the carbonyl group abstracts a hydrogen atom from an adjacent hydrocarbon group, forming a ketyl radical. The hydrogen‐depleted hydrocarbon generates a carbon‐centered radical, which reacts with the ketyl radical, leading to the formation of a covalent C─C bond (Figure 2f) [57, 58, 59, 60]. Unlike the C─H insertion reaction with benzophenone which involves a mutual reaction between two radicals, the C─H insertion reactions with azide and azrine proceed via a different mechanism, where nitrene or carbene intermediates attack the hydrocarbon and construct covalent C─C bond. In detail, azide moiety is activated upon UV irradiation, leading to the formation of nitrene intermediate through the release of nitrogen gas. This nitrene intermediate then attacks the hydrogen carbon and abstracts a hydrogen atom, forming a C─N covalent bond and resulting in the formation of a secondary amine structure (Figure 2g) [23, 61]. Diazirine moiety also releases nitrogen gas upon UV irradiation, generating a carbene intermediate that leads to the formation of a covalent C─C bond [62, 63]. The resulting carbene species can exist in either singlet or triplet states and can undergo C─H insertion via three distinct pathways: (1) concerted or direct insertion through a triangular activated complex; (2) stepwise hydrogen abstraction followed by recombination, involving a radical or ion‐pair intermediate; and (3) coordination leading to ylide formation. While singlet carbenes can follow any of these pathways, triplet carbenes predominantly undergo insertion via the stepwise abstraction–recombination mechanism (pathway 2) [64]. Accordingly, mechanism 2 was depicted as the representative pathway in Figure 2h, since it is accessible to both singlet and triplet carbenes.

Recently, direct crosslinking reactions between alkane groups have been explored without these UV‐active additives by employing strong energy sources. Notably, electron beam and X‐ray beam irradiations are commonly used for this purpose [65, 66]. Upon exposure to these high‐energy sources, C─H bond cleavage occurs, followed by dehydrogenation, which leads to the formation of carbon‐carbon double bonds and subsequently induces crosslinking (Figure 2i).

While all of the photochemical reactions described above rely on the direct participation of carbon‐based functional groups, recent advances have demonstrated the potential of sulfur‐based functional groups as photoreactive sites. For instance, thiol groups can be transformed into disulfide bonds via photocatalytic oxidation using metal nanocrystals as catalysts. When the highest occupied molecular orbital of the thiol group is located above the valence band maximum of the metal nanocrystal, the thiol group captures the photogenerated holes and constructs a disulfide bond (Figure 2j) [67]. Disulfides are generally regarded as dynamic covalent bonds, capable of reversible cleavage and reformation under specific stimuli [68, 69]. Particularly, 1,2‐dithiolane, which is a five‐membered cyclic disulfide structure, has been exploited to prepare polymers with stimuli‐responsive and dynamic architectures. The photo‐induced polymerization process of 1,2‐dithiolane was described by Calvin et al. [70] Upon irradiation with long‐wavelength UV light, the disulfide bonds undergo homolytic cleavage to generate thiyl radicals, which propagate through reaction with other cyclic disulfides, relieving ring strain and ultimately forming a polydisulfide structure without additional radical initiators (Figure 2k) [71].

3. Applications of Photo‐Induced Polymerization for Direct Lithography

Direct photolithography enables high‐resolution QD patterning through spatially confined photochemical reactions, eliminating the need for sacrificial photoresist layers or wet/dry etching steps. This approach relies on photo‐induced polymerization or crosslinking, which modifies the solubility or mechanical properties of QD‐containing films, allowing selective material retention in light‐exposed regions. It typically involves three steps: 1) formulating a homogeneous QD solution containing photo‐reactive ligands or additives, followed by spin‐coating onto a substrate; 2) site‐specific light exposure through a photomask to induce chemical transformation; and 3) selective removal of unreacted regions by solvent development. These photochemical processes result in the formation of crosslinked polymeric networks through reactions involving ligand‐ligand, ligand‐polymer, or polymer‐polymer linkages. In this section, we review recent strategies for polymerization‐induced QD lithography, classified by the primary functional groups involved—namely, alkene, alkane, alkyne, and disulfide moieties—as discussed in Section 2.

3.1. Alkene (C═C Bond)‐Based Lithography

Unlike alkanes, which consist solely of σ bonds, alkenes feature an additional π bond with high electron density and relatively low bond energy. This structural characteristic enhances their reactivity, particularly toward electron‐deficient molecules. The elevated energy state of the π electrons facilitates a range of photo‐induced electrophilic addition reactions, including thiol‐ene coupling, free‐radical polymerization, and cycloaddition. This section introduces recent photopatterning strategies utilizing the reactivity of alkenes.

3.1.1. Thiol‐ene Reaction

Among the various alkene‐based photochemical reactions, the thiol‐ene reaction, a type of click chemistry introduced by Sharpless [72], is one of the most powerful and versatile strategies. This reaction proceeds in a regio‐ and chemo‐selective manner and is efficiently induced by UV irradiation, making it a simple yet high‐yielding photo‐induced process. When a molecule with two or more thiol groups is employed as crosslinker, dense crosslinked networks are readily formed with unsaturated hydrocarbons without producing byproducts. These advantages have garnered significant attention in the field of direct photolithography [46, 73, 74, 75, 76, 77].

In one representative example, thiol‐ene crosslinking was utilized to fabricate CdSe/CdZnS QD films via photochemical coupling between oleic acid (OLA) ligands and 4,4’‐thiobisbenzenethiol (TBBT) additive (Figure 3a) [73]. Here, the TBBT molecule not only functioned as a crosslinker but also acted as a hole‐transporting component, facilitating the extraction of photogenerated holes from the QDs and suppressing charge recombination. This dual‐functionality led to a significant increase in photoluminescence (PL) intensity up to 132.8% in blended films and 121.9% in crosslinked ones while maintaining constant absorption and PL peak positions. Furthermore, high‐resolution patterns down to 2 µm were achieved by direct UV irradiation (365 nm) through a photomask. Shin et al. expanded the thiol‐ene ligand crosslinking strategy by incorporating a tetrathiol molecule, pentaerythritol tetrakis(3‐mercaptopropionate) (PETMP), as a crosslinker (Figure 3b) [74]. The increased number of thiol functional groups enhanced the crosslinking density of the resulting QD films, thereby showing exceptional solvent resistance even after immersion in toluene. High‐resolution photo‐patterns with feature sizes ranging from 50 to 5 µm were successfully demonstrated (Figure 3c). Notably, the incorporation of PETMP led to an increase in the relative PL quantum yield (PLQY) from 112.7% (before crosslinking) to 122.9% (after UV‐induced crosslinking), based on the normalized PLQY of pristine InP QDs set as 100%, without affecting spectral properties. Furthermore, PETMP‐crosslinked QD films exhibited improved charge transport properties, resulting in a peak current efficiency of 23.04 cd·A⁻¹, approximately 58% higher than that of standard InP‐QD LEDs.

FIGURE 3.

Photopatterning approaches based on thiol‐ene chemistry. Schematic illustrations of thiol‐ene reactions between OA ligands and (a) TBBT crosslinker [73] or (b) PETMP crosslinker [74]. (c) Photograph of crosslinked InP QD fims prepared from PETMP crosslinkers [74]. Reproduced with permission [73]. Copyright 2024, Wiley–VCH GmbH. Reproduced with permission [74]. Copyright 2023, Wiley–VCH GmbH. (d) Photopatterning procedure of PQD precursors followed by in‐situ crystallization, and (e) resulting patterned images. Reproduced with permission under the term of CC–BY license [46] Copyright 2022, The Authors, published by Springer Nature. (f) QD/siloxane ink formulation for photocrosslinking reaction. Reproduced with permission [77]. Copyright 2019, American Chemical Society.

A similar strategy was extended to perovskite nanocrystals (PNCs) with OLA and oleylamine (OLAm) as surface ligands [75]. Strong photocatalytic activity of PNCs enabled the efficient generation of thiyl radicals from PETMP under low‐energy UV exposure, allowing for precise and nondestructive patterning of nanocrystals with sub‐micron resolution (down to 560 nm) via thiol‐ene chemistry. In addition to enhanced structural stability, the patterned films exhibited an approximately 5% increase in PLQY, attributed to effective surface passivation by PETMP. The versatility of this crosslinking chemistry was also demonstrated with various emissive materials, including CdSe‐based QDs, InP‐based QDs, and conjugated polymers containing alkene moieties either in their molecular structure or surface ligands.

This photocatalytic effect was further adapted for in situ synthesis and patterning of PQDs using lead bromide precursors. Zhang et al. developed a perovskite precursor resist (PPR) incorporating lead bromide as photocatalysts to initiate photopolymerization, with trimethylolpropane tris(3‐mercaptopropionate) (TTMP) and triallyl isocyanurate (TAIC) as monomers [46]. UV exposed areas underwent thiol‐ene photopolymerization, followed by subsequent annealing to convert the patterned lead complexes into luminescent PQDs under relatively mild conditions compared to conventional hot‐injection synthesis (Figure 3d). This in situ approach eliminates the need for pre‐synthesized PQDs, thereby ensuring uniform and residual‐free PQDs within the polymer matrix and reducing processing complexity. By controlling the UV exposure and annealing temperature, the researchers achieved tunable emission across the visible spectrum, enabling direct patterning of red, green, and blue PQD pixels (Figure 3e). The resulting PQD‐polymer composite patterns exhibited high resolution (up to 2450 pixels per inch, PPI), excellent fluorescence uniformity, and structural integrity. Building upon this concept, Wei et al. introduced a photoinitiator‐grafted photoresist system to further refine the thiol‐ene based direct photopatterning of PQDs [76]. This design allowed precise localization of free radical generation, thereby minimizing edge roughness and improving pattern fidelity. High‐resolution multicolor PQD pixel arrays were successfully fabricated on both rigid and flexible substrates, while maintaining high PLQY by in situ formation of PQDs after patterning.

The photopatternability as well as the long‐term stability of QDs were introduced by making composites with methacrylate functionalized siloxane resin (Figure 3f) [77]. Pentaerythritol tetrakis(3‐mercaptobutylate) (KarenzMT PE1) was employed as a crosslinker to form a strong network and enhance the mechanical stability of the patterned QD films upon UV irradiation. This strategy not only provided high‐resolution photopatterning but also significantly improved the solvent resistance and long‐term stability of QD films. The siloxane layers on the QD surfaces effectively suppressed ligand detachment and aggregation, preserving the optical and structural integrity of QDs even under harsh environmental conditions. Furthermore, the incorporation of alkene‐functionalized siloxane chemistry enabled precise and scalable multi‐color pixel patterning, making it highly suitable for next‐generation QD display technologies.

3.1.2. Free Radical Polymerization

Among various photopatterning approaches, the thiol‐ene reaction was introduced as the first example to utilize alkene groups present in conventional ligands such as OLA and OLAm. A key ingredient in this process is a thiol‐based crosslinker that generates thiyl radicals upon UV irradiation and a network structure is produced via addition reactions with the unsaturated hydrocarbons. Therefore, by substituting thiol crosslinkers with alternative radical‐generating additives under UV, a chain growth polymerization is enabled with unsaturated hydrocarbon ligands. Shin et al. successfully achieved free radical polymerization of the unsaturated bonds in the ligands by introducing a photoinitiator instead of a thiol additive (Figure 4a) [78]. Upon UV irradiation at 365 nm, acetophenone‐type molecules generate free radicals that initiate polymerization by attacking the C═C bonds of the ligands. The resulting radical species propagate through neighboring unsaturated ligands and the polymerization is proceeded. The efficiency of this photopolymerization was highly dependent on the position of the C═C moieties in the ligands. While OLA, which contains a double bond in the middle of the alkyl chain, exhibited limited reactivity due to steric hindrance, olefin‐terminated ligands such as 9‐decenoic acid (DeA) showed more efficient polymerization. This is attributed to the increased accessibility of terminal C═C bonds with active radical species. These findings suggest that the critical influence of ligand architecture on patterning efficiency and highlight the importance of rational ligand design for enhancing the precision and fidelity of PNC photopatterning.

FIGURE 4.

Other alkene‐based photo‐crosslinking reactions in PNC and QD composites. (a) Ligand crosslinking via free radical polymerization under UV irradiation. Reproduced with permission [78]. Copyright 2022, Elsevier B.V. (b) Crosslinking induced by electron beam irradiation. Reproduced with permission under the term of CC–BY license [79]. Copyright 2022, The Authors, published by American Chemical Society. (c) Cinnamate‐functionalized polymer ligand employed for multicolored PNCs. Reproduced with permission [80]. Copyright 2021, American Chemical Society. (d) [2+2] Cycloaddition of PVCN enabling solvent‐resistant PQD composites. Reproduced with permission [81]. Copyright 2022, The Royal Society of Chemistry.

By exploiting the relatively weak nature of the π bond, reactive species can be generated through direct exposure to high‐energy electron beam irradiation without requiring chemical additives (Figure 4b) [79]. In this study, the incident high‐energy electrons produced free electrons across a wide range of energy spectrum and induced molecular excitations, along with generation of reactive holes, ionized species, and radicals. These reactive intermediates directly modified the surface ligands of PNCs, initiating covalent bond formation between adjacent PNCs. Although some degradation in PLQY occurred due to the high energy of e‐beam, high‐resolution PNC patterns with feature sizes down to 100 nm were successfully achieved.

3.1.3. Cycloaddition Reaction

Although the possibility of cycloaddition between two alkene groups present in OLA and OLAm ligands has been proposed [79], these molecules can undergo a variety of photochemical reactions including cycloaddition, C─H insertion, and free radical polymerization depending on the specific reaction conditions. In contrast, cinnamoyl groups preferentially undergo [2+2] cycloaddition under UV irradiation, where this reaction pathway competes primarily with trans‐cis isomerization [55]. Leveraging the photo‐crosslinking capability of cinnamoyl groups, multifunctional polymeric ligands were synthesized by atom transfer radical polymerization of 2‐cinnamoyloxyethyl methacrylate (CEMA). Ammonium halide (NH₃X) was introduced as the terminal functional group to facilitate efficient ligand exchange with PNCs (Figure 4c) [80]. By replacing conventional OLA and OLAm ligands with the cinnamoyl‐containing polymer ligands (PCEMA‐NH₃X), direct photopatterning of PNCs was achieved through photo‐induced cycloaddition between adjacent cinnamoyl moieties, forming a crosslinked polymer shell around the PNCs. This encapsulating polymer network significantly enhanced the solvent resistance and long‐term environmental stability of patterned PNC structures against polar solvents, oxygen, and moisture. Additionally, RGB micropatterns with feature sizes as small as 10 µm × 40 µm were successfully demonstrated.

Rather than solely relying on surface ligand crosslinking, poly(vinyl cinnamate) (PVCN) was introduced as a resin matrix to fabricate photo‐patternable PQD‐based nanocomposites (Figure 4d) [81]. The cinnamate moieties in PVCN undergo UV‐induced [2+2] cycloaddition reactions to form a crosslinked polymer network that effectively immobilizes the embedded PQDs. Notably, the good solubility of PVCN in nonpolar solvents such as toluene avoids exposure of PQDs to polar environments, which are known to desorb the surface ligands and potentially degrade the perovskite cores. Utilizing this strategy, high‐resolution micropatterns with feature sizes as small as 3.86 µm were fabricated, while exhibiting superior optical properties and enhanced environmental stability.

3.1.4. Acrylate polymerization

Acrylate represents a prominent class of alkene‐based monomers widely employed in polymerization and crosslinking reactions. The carbonyl group adjacent to the alkene forms a conjugated structure that helps stabilize the radical intermediate when a free radical is added to the double bond. This conjugated structure also reduces the activation energy barrier of the transition state, thereby accelerating the overall reaction rate [86]. Owing to these characteristics, acrylate‐type monomers readily undergo efficient free radical or photo‐initiated polymerization, as well as crosslinking reactions.

Ong and coworkers designed a multifunctional bidentate ligand comprising two carboxylic acids and two acrylate groups (Figure 5a) [82]. The incorporation of dicarboxylic acids moieties enabled strong surface binding to PNCs and promoted favorable substitutions of native monodentate ligands. The photosensitive acrylate groups underwent free radical polymerization with exposure to UV light (365 nm) and an insoluble polymer network is produced among adjacent PNCs. Notably, the use of this bidentate ligand significantly mitigated the reduction in PL quantum efficiency (PLQE) after repetitive washing processes due to its enhanced surface passivation compared to labile OLA and OLAm ligands. By using direct laser writing, well‐defined green and red luminescent patterns with feature sizes as small as 20 µm were obtained. In a similar approach, a methacrylate‐functionalized zwitterionic ligand was developed for PNCs [87]. Both cationic and anionic groups from the ligand allowed effective passivation, improving optical properties as well as colloidal and chemical stability. Solubility issues associated with zwitterionic structures were addressed by introducing aliphatic chains with optimized length into the middle of the ligand structure. The methacrylate groups at the end of the ligand enabled UV‐induced crosslinking at 365 nm, and robust PNC arrays with a minimum resolution of 4 µm were produced with excellent long‐term optical stability in the air.

FIGURE 5.

Utilization of acrylates for direct photolithography (a) Design of bidentate acrylate ligands and their applications for crosslinked PNC composites. Reproduced with permission [82]. Copyright 2024, Wiley‐VCH GmbH. (b) UV‐polymerizable PQD ink synthesized via siloxane chemistry and its patterning procedure. Reproduced with permission [83]. Copyright 2023, Elsevier Inc. (c) One‐pot synthesis of UV‐crosslinkable PQDs with acrylate monomers. Reproduced with permission [84]. Copyright 2024, Tsinghua University Press. (d) Polymerization of acrylate ligands using ultrafast femtosecond laser irradiation. Reproduced with permission under the term of CC–BY license [85]. Copyright 2025, The Authors, published by IOP Publishing Ltd on behalf on the IMMT.

Photocrosslinkable methacrylate moieties can be introduced not only on ligands but also on the surface passivation layers of NCs. For instance, PQDs were initially encapsulated with SiO₂ shells to improve their environmental stability, then 3‐(trimethoxysilyl)propyl methacrylate (TMSPMA) was attached to the SiO₂ surface. Simultaneously, O₂ plasma‐treated polydimethylsiloxane (PDMS) substrates were chemically modified with TMSPMA to facilitate the adhesion of the PQD inks (Figure 5b) [83]. This strategy was further extended to construct QD pocket architectures where QDs are fully embedded within a resin matrix [88]. Specifically, methacrylate functionalized CdSe/CdS@SiO₂ nanoparticles were blended with a commercial UV‐curable resin, and a tri‐layered QD pocket structure was fabricated through sequential deposition of blank resin, QD‐loaded resin, and blank resin. This configuration resulted in a QD‐rich core encapsulated by blank resin layers, effectively shielding the QDs from external environmental factors including oxidation and moisture. The critical role of SiO₂ passivation layers was further validated in the development of one‐pot synthesized UV‐crosslinkable PQDs [84]. Initially, untreated‐PQDs (UT‐PQDs) were synthesized and mixed with isobornyl acrylate (IBOA) and dimethylol propane tetracrylate (DI‐TMPTA) to form a solution‐processed PQD film. However, these UV‐crosslinked films exhibited a low PLQY of 60%, attributed to substantial optical loss from insufficient surface passivation. This limitation was addressed by introducing a SiO₂ protective shell via silane chemistry. The UT‐PQD solution was treated with tetramethoxysilane (TMOS), TMSPMA, and 3‐aminopropyltrimethoxysilane (APTMS), forming a conformal SiO₂ shell that enhanced both the surface stability and the compatibility with acrylate‐based monomers (Figure 5c)​. As a result, the modified PQD films exhibited significantly improved PLQY up to 91.2%. This one‐pot synthetic method eliminates complex purification and ligand post‐treatment steps, ensuring enhanced environmental stability and solution processability.

Beyond conventional UV light source, acrylates can be polymerized using different light sources under appropriate conditions. One promising approach involves ultrafast femtosecond lasers, particularly utilizing multiphoton absorption processes. For instance, acrylate‐functionalized hybrid precursors containing QDs, acrylate‐functionalized polyhedral oligomeric silsesquioxane (POSS), and a photoinitiator can undergo localized‐crosslinking upon irradiation with a femtosecond laser at a wavelength of 1030 nm, leading to sub‐100 nm resolution through a nonlinear threshold effect (Figure 5d) [85]. This approach necessitates the presence of photoinitiators such as Irgacure 369, which efficiently generates radicals required for crosslinking acrylic functional groups under high‐intensity laser conditions. An alternative approach employs a mode‐locked femtosecond Ti:Sapphire laser at a wavelength of 780 nm [89]. In this system, a dithiolane ligand containing a vinyl group was anchored to the surface of In(Zn)P/ZnS QDs to facilitate strong binding to the QDs while enabling covalent integration into an acrylate‐based urethane matrix via radical polymerization. A catalytic amount of highly efficient two‐photon absorbing photosensitizers was added to enhance radical generation under laser exposure. This approach enables fabrication of hierarchical polymer arrays with microscale resolution and uniform QD dispersion within the polymeric network, as confirmed by confocal fluorescence microscopy. Although a slight decrease in photoluminescence intensity was observed after ligand exchange, the QDs maintained their stable emission characteristics in the patterned structures.

3.2. Alkane (C─C Bond)‐Based Lithography

Alkane bonds are prevalent in organic materials, yet their low reactivity makes them challenging to utilize in direct crosslinking reactions, in contrast to the more reactive alkene or acrylate groups commonly employed in polymerization. Recent advancements in C─H activation and radical‐mediated functionalization have opened new avenues for alkane‐based crosslinking, providing promising strategies for high‐resolution patterning and enhanced material stability.

3.2.1. C─H Breakage and Dehydrogenation

Low‐flux X‐ray lithography was introduced to demonstrate direct patterning and enhance the stability of CsPbX₃ PNCs [66]. This technique leverages X‐ray irradiation to induce C─H bond cleavage and subsequent C═C bond formation, effectively crosslinking adjacent surface ligands and stabilizing the NC film (Figure 6a). X‐ray lithography had previously been underutilized for PNC patterning due to concerns over radiation‐induced degradation, particularly under high‐flux conditions that generate trap states and suppress PL. However, this study demonstrated that carefully controlled, low‐dose X‐ray exposure (10¹¹ photons/mm²·s for ≤ 30 min) can induce efficient ligand crosslinking without causing perovskite structural degradation. The resulting PNC films exhibited improved pattern fidelity and long‐term stability. These findings suggest that X‐ray lithography can be optimized by precisely controlling the irradiation dose, achieving efficient crosslinking while minimizing photoluminescence quenching, thereby making it a viable alternative to conventional photolithography.

FIGURE 6.

Crosslinking chemistries applicable to alkane‐based ligands. (a) C─H breakage and dehydrogenation of saturated aliphatic compounds induced by X‐ray irradiation. Reproduced with permission [66]. Copyright 2015, American Chemical Society. (b) C─H insertion mechanism of benzophenone‐functionalized ligands. Reproduced with permission [57]. Copyright 2022, The Authors, under exclusive licence to Springer Nature Limited. (c) Representative examples of azide‐based crosslinkers. Reproduced with permission [39]. Copyright 2022, Wiley‐VCH GmbH. (d) C─H insertion mechanisms involving azide‐ and azirine‐based crosslinkers. Reproduced with permission [90]. Copyright 2022, Wiley‐VCH GmbH.

3.2.2. Benzophenone‐Mediated C─H Insertion

Benzophenone moieties, which are mostly utilized for photoinitiators [76], can also serve as built‐in C─H activation and crosslinking sites. Hahm et al. developed a benzophenone‐mediated ligand crosslinking strategy that enables direct photopatterning of QDs via C─H insertion chemistry without requiring additional photoinitiators [57]. They introduced a dual‐ligand system, consisting of photo‐crosslinkable ligands (PXLs) bearing benzophenone functionalities and dispersing ligands (DLs), allowing precise control over QD surface chemistry and solution stability (Figure 6b). Upon UV‐A (365 nm) exposure, the benzophenone units generate ketyl radicals, which abstract hydrogen atoms from neighboring aliphatic DL chains. This radical‐mediated hydrogen abstraction induces covalent C─H crosslinking between QDs. As a result, a highly stable and solvent resistant QD network is produced while maintaining more than 95% of its initial PLQY.

3.2.3. Azide‐ and Azirine‐Mediated C─H Insertion

Yang et al. first introduced bisazide crosslinkers as an effective strategy for the photopatterning of colloidal QDs [23]. In this study, ethane‐1,2‐diyl bis(4‐azido‐2,3,5,6‐tetrafluorobenzoate) was synthesized as a highly efficient crosslinking reagent. Upon UV exposure, nitrene radicals are generated and readily insert into the C─H bonds of native alkyl ligands to form a covalently crosslinked QD network. Compared to conventional ligand exchange methods, this strategy preserved the original surface chemistry of QDs, thereby minimizing PL quenching. High‐resolution RGB QD micropatterning with a feature size of 3 µm (∼1400 ppi) was achieved while preserving luminescence and charge transport properties. Notably, the photopatterned QD‐LEDs exhibited an external quantum efficiency (EQE) of 14.6%, comparable to pristine QD films. Additionally, this process was compatible with inkjet printing and scalable photolithography, highlighting its potential for large‐area QD display manufacturing. Similar bisazide crosslinkers have been utilized for direct photopatterning of PNCs [91]. The resulting PNC patterns retained up to 60% of the initial PLQY at a resolution of down to 5 µm. A post‐patterning ligand passivation step further improved absolute PLQY to 76% to render this method viable for electroluminescent (EL) applications. Indeed, the device achieved a maximum EQE of 6.8% and luminance exceeding 20 000 cd·m⁻², highlighting its potential for next‐generation display technologies.

Crosslinking efficiency and material stability can be enhanced by designing branched multi‐azide crosslinkers containing 4 and 6 azide groups (4‐LiXer and 6‐LiXer, respectively) (Figure 6c) [39]. Compared to bisazide systems, these multi‐azide variants significantly increased crosslinking densities, leading to improved solvent resistance and mechanical robustness, as evidenced by film thickness retention measurements (FRR). The steric hindrance of the branched architecture also suppressed lateral diffusion of reactive intermediates, thereby enhancing photopatterning fidelity to submicron resolution (≈1 µm). Furthermore, QD‐LEDs employing IP‐6‐LiXer crosslinked emissive layers exhibited enhanced operational stability, retaining 90% of the initial luminance (900 cd·m⁻²) after 156 h, compared to only 15 h for un‐crosslinked QD films. Although EQE remained unchanged (∼8.3%), the enhanced charge injection uniformity reduced localized current concentrations and mitigated potential degradation. These results demonstrate the critical role of crosslinker architecture in the reliability of QD‐based optoelectronic devices.

While azide‐based crosslinking has been applied successfully, Lu et al. introduced an alternative C─H insertion chemistry using azirine‐functionalized ligands [90]. Two distinct photoreactions were compared: nitrene insertion from azide crosslinkers and carbene radical insertion from azirine moieties (Figure 6d). The azirine‐derived carbenes exhibited reaction rates 2–3 orders of magnitude faster than nitrenes, due to their different electronic configurations. The sp²‐hybridization of singlet phenyl carbene favor the σ²‐configuration of the two electrons in the same orbital. As a result, the empty p‐orbitals facilitate the rapid addition to C─H bonds. In contrast, the sp‐hybridization of singlet phenyl nitrene leads to the σ¹‐π¹‐configuration, placing two electrons in different p‐orbitals with opposite spin directions. In addition, the low energy gap for intersystem conversion of spin states of carbene indicates that highly reactive single carbenes can be reserved as the triplet carbene state, enabling rapid and efficient C─H insertion crosslinking. This fast reactivity reduced trap state formation and enhanced charge injection in QD‐LEDs so that the fabricated devices exhibited an EQE value approaching 12% and an extended operational lifetime of over 4800 h. Diazirine‐based crosslinkers were also employed for direct photopatterning of PNC [92]. Nondestructive patterns at ultra‐high resolution of 4000 ppi were obtained with PLQY retention up to 90%. PNC‐LED devices fabricated using this method exhibited the maximum EQE of 16% and luminance exceeding 60 000 cd·m⁻², further advancing scalable patterning for high‐resolution display applications.

Despite the superior kinetics of carbene‐based systems, their oxygen sensitivity remained a major barrier to commercial‐scale photopatterning. To solve this limitation, Fu et al. designed electronically optimized diazirine crosslinkers featuring electron‐donating groups (EDGs) to stabilize singlet carbenes and suppress the formation of oxygen‐sensitive triplet states [93]. This allowed fully air‐compatible, nondestructive QD patterning via standard i‐line photolithography, achieving an ultrahigh resolution of >13,000 ppi while maintaining ∼100% (CdSe‐based QDs) and ≈90% (InP‐based QDs) of initial PLQY. The devices fabricated under ambient conditions showed a peak EQE of 15.3% and a maximum luminance exceeding 40 000 cd·m⁻², demonstrating that electronic stabilization of carbenes offers a viable path for integrating high‐performance QD‐LEDs into commercial display fabrication.

3.3. Alkyne (C≡C Bond)‐Based Lithography

Unlike alkene‐ or alkane‐based ligand crosslinking, alkynes have received comparatively little attention in crosslinking chemistry. The high bond dissociation energy and the lower reactivity of the C≡C triple bonds compared to the C═C double bonds make direct free‐radical polymerization less efficient. However, recent studies have explored thiol–yne click chemistry and photo‐initiated alkyne bridging to develop chemically stable and high‐resolution patterned QD and PNC films.

3.3.1. Thiol‐yne Reaction

Stewart et al. demonstrated the use of thiol‐yne chemistry for incorporating alkyne‐functionalized ligands into polymerizable QD nanocomposites (Figure 7a) [94]. In this study, alkyne‐terminated dihydrolipoic acid (DHLA) ligand was synthesized and introduced onto the QD surface through ligand exchange, as the dithiol group in DHLA ligand acts as binding site. The terminal alkyne moieties on the surface of QDs were incorporated with additional thiol crosslinker (PTMP) enabling thiol–yne chemistry under UV irradiation. Unlike traditional thiol–ene chemistry, thiol–yne reactions provide additional crosslinking points, enabling higher network density and improved mechanical stability. In addition, the resulting QD–thiol–yne nanocomposites retained their photoluminescence properties, and exhibited high transparency and flexibility, making them promising candidates for display and optical applications.

FIGURE 7.

Alkyne‐based photo‐crosslinking reactions. (a) Thiol‐yne crosslinking. Reproduced with permission [94]. Copyright 2018, American Chemical Society. (b) Alkyne‐alkyne bridging with simplified reaction scheme. Reproduced with permission [26]. Copyright 2021, Wiley‐VCH GmbH.

3.3.2. Alkyne to Alkyne Bridging Reaction

Building on the concept of alkyne‐based ligand crosslinking, direct alkyne‐alkyne bridging was demonstrated with commercially available alkynoic acid (Figure 7b) [26]. A crosslinkable ligand system containing alkyne groups was designed to address the chemical instability of PQDs. The ligand structure consisted of a carboxyl head group, which ensures strong surface binding, an alkyl spacer that controls diffusion kinetics, and an alkyne tail group that facilitates UV‐induced crosslinking, driving the covalent C─C bond formation process. The alkynoic acid ligands with photoinitiator not only effectively prevent moisture‐assisted ligand dissociation but also enhance PLQY value from 70% to 88% due to the in situ crystalline reconstruction of QDs. This enhanced stability with photopatterning capabilities enabled the fabrication of high‐resolution PNC films demonstrating its potential for precise nanoscale device structuring.

3.4. Disulfide (S─S)‐Based Lithography

Alongside carboxylate coordination, thiol functional groups have been widely utilized as binding ligands in QD and PNC systems. Although thiol‐terminated ligands bind strongly to metal and metal oxide surfaces through chemisorption, thiol groups are transformed to disulfide bonds via UV‐induced oxidation, which can be utilized as photoinduced desorption strategies. This concept was demonstrated by functionalizing TiO₂ surfaces with mercaptohexadecanoic acid (MHDA) and selectively oxidizing terminal thiol groups into disulfides under UV exposure [95]. Desorption of disulfide‐bound ligands allowed for the selective site deposition of CdSe QDs, achieving microscale patterning via a photocatalytic lithography approach. While this study successfully employed photoinduced disulfide formation for QD patterning, the method relied on a two‐step process—patterning via ligand desorption followed by QD attachment. Thus, it does not represent direct photolithography of QDs but a patterning‐assisted self‐assembly approach. To achieve direct lithography, subsequent studies have explored the photo‐reactive properties of disulfide‐containing ligands for in situ QD and PNC crosslinking.

Liu et al. introduced a laser direct writing technique called photoexcitation‐induced chemical bonding for 3D nanoprinting of QDs [67]. In this study, CdSe/ZnS core/shell QDs were functionalized with 3‐mercaptopropionic acid, where the thiol group formed Zn─S bonds with the ZnS shell, leaving the carboxylate group exposed. Under laser excitation, electron‐hole pairs were generated within the CdSe core, and the resulting holes migrated to the surface, oxidizing thiol groups into disulfides. This oxidation caused ligand desorption, exposing active Zn bonding sites, which facilitated carboxylate‐mediated interparticle crosslinking and enabled direct QD assembly (Figure 8a).

FIGURE 8.

Disulfide‐related chemical reactions for crosslinked QD assemblies. (a) Photooxidation of thiol‐containing ligands to form disulfide bonds. Reproduced with permission [67]. Copyright 2022, The American Association for the Advancement of Science. (b) Ring‐opening polymerization of cyclic disulfide ligands. Reproduced with permission under the term of CC–BY‐NC‐ND license [45]. Copyright 2025, The Authors, Advanced Materials published by Wiley‐VCH GmbH.

Unlike conventional thiol‐functionalized ligand crosslinking approaches, a novel ring‐opening polymerization (ROP) strategy for QD patterning has been recently introduced [45]. In this study, lipoic acid (LA) was functionalized onto QD surfaces, where its carboxylate group ensured strong surface attachment, while its cyclic disulfide structure enabled ring‐opening polymerization (ROP) upon UV exposure (Figure 8b). This process enabled the fabrication of high‐resolution, full‐color QD patterns with a feature size of ≈3 µm and a pixel density exceeding 3788 ppi, making it suitable for next‐generation microdisplays. Notably, the ROP process was reversible, allowing for QD pattern flexibility, self‐healing properties, and material recyclability. Additionally, this reversible crosslinking mechanism facilitated the recovery and reuse of QDs, addressing sustainability concerns in display technology. Compared to traditional ligand crosslinking strategies, this study demonstrates the potential of ROP‐based photopatterning as a versatile and scalable method for QD assembly, paving the way for ultra‐high‐resolution optoelectronic devices, AR/VR displays, and flexible electronics.

4. Summary and Outlook

Polymerization‐induced direct photolithography has emerged as a powerful tool for patterning QDs with sub‐micrometer precision, offering a unified platform that combines photochemical crosslinking, surface immobilization, and pattern definition into a single process. This review comprehensively examined the foundational chemistries underlying this approach, with particular emphasis on diverse functional groups—alkenes, alkynes, alkanes, and disulfides—that can be activated under light exposure to form robust polymeric networks (Table 1). In Section 2, we outlined the mechanistic pathways of photochemical reactions such as thiol‐ene/yne click coupling, free radical polymerization, cycloaddition, C─H insertion, and ring‐opening polymerization. These mechanisms enable dynamic control over network formation, solubility modulation, and interfacial binding, all critical for high‐resolution patterning. Section 3 provided an in‐depth analysis of how these reactions have been implemented for QD lithography across a range of compositions, including CdSe‐, InP‐, and perovskite‐based QDs. We discussed the influence of ligand architecture, monomer design, photoinitiator efficiency, and light source configuration on pattern fidelity, photoluminescence retention, environmental stability, and device integration. Through numerous examples, it became clear that polymerization‐based lithographic approaches not only enable fine feature resolution, but also impart desirable characteristics such as solvent resistance, mechanical integrity, and long‐term operational stability to QD‐based films. In particular, ring‐opening polymerization of cyclic disulfides, acrylate‐functionalized hybrid systems, and C─H insertion crosslinking chemistry were shown to offer advanced functionalities such as reversibility, self‐healing, and compatibility with stretchable substrates.

TABLE 1.

Classification of polymerization‐induced photolithographic methods based on photoactive functional groups and reaction mechanisms.

Polymerization chemistry		Composite type	QD	Cross‐linker	Light source	Reference
Alkene (C═C)	Thiol‐ene	Ligand polymerization	CdSe/CdZnS QD	TBBT	365 nm	[73]
			InP‐based QD	PETMP	365 nm	[74]
			Perovskite nanocrystal	PETMP	365 nm	[75]
		Polymer coated QD	Perovskite QD	TTMP	365 nm	[46]
			Perovskite QD	PETMP	365 nm	[76]
			CdSe/CdZnS QD	PE1	365 nm	[77]
	Free Radical Polymerization	Ligand polymerization	CsPbBr3 nanocrystal	X	365 nm	[78]
			CsPbBr3 nanocrystal	X	E‐beam	[79]
	Cycloaddition	Ligand polymerization	CsPbBr3 nanocrystal	X	365 nm	[80]
		Polymer coated QD	FAPbBr3 nanocrystal	X	4W compact UV lamp	[81]
	Acrylate	Ligand polymerization	CsPbBr3 nanocrystal	X	365 nm	[82, 87]
			CsPbBr3 QD@SiO2	X	365 nm	[83]
			CdSe/CdS QD@SiO2	UV resin	385 nm	[88]
			CsPbBr3 (LTP‐PQD)	IBOA, DI‐TMPTA	365 nm	[84]
			CdSe/ZnS QD	X	1030 nm (femtosecond lase)	[85]
			In(Zn)P/ZnS alloy QD	SCR‐500	780 nm laser	[89]
Alkane (C─C)	C─H breakage and dehydration	Ligand polymerization	CsPbBr3 nanocrystal	X	X‐ray	[66]
	C─H insertion (Benzophenone)	Ligand polymerization	InP/ZnSexS1‐x QD, CdxZn1‐xS/ZnS QD	X	365 nm	[57]
	C─H insertion (Azide)	Ligand polymerization	CdSe/CdZnS QD	LiXer	254 nm	[23]
			CsPbBr3 nanocrystal	BisFPA	365 nm	[91]
			InP/ZnSeS QD, ZnSe/ZnS QD	4‐LiXer, 6‐LiXer	254 nm	[39]
			CdSe NC	bisPFPA‐based	365 nm	[90]
	C─H insertion (Azirine)	Ligand polymerization	CdSe NC	PF‐TAD	365 nm	[90]
			CsPbBr3, FAPbBr3 NC	PF‐TAD	365 nm	[92]
			InP/ZnSe/ZnS QD	Tris‐TAD, O‐TAD, EP‐TAD	365 nm	[93]
Alkyne (C≡C)	Thiol‐alkyne	Ligand polymerization	CdSe/ZnS QD	PETMP	365 nm	[94]
	Alkyne‐Alkyne bridging	Ligand polymerization	CH3NH3PbBr3 QD	X	254 nm	[26]
Disulfide		Ligand polymerization	CdSe/ZnS QD	X	780 nm femtosecond laser	[67]
			InP QD	BPA‐LA	365 nm	[45]

While polymerization‐induced direct photolithography has shown remarkable potential for achieving high‐resolution, chemically stable QD patterning, several challenges remain to be addressed for broader applicability. In particular, despite advances in monomer and initiator systems, there is still a lack of in‐depth understanding regarding the complex interplay between QDs and ligand exchange processes during photopatterning. This often results in undesirable losses of optical properties, such as photoluminescence quenching or spectral shifts, during or after exposure and curing. Moreover, achieving uniform feature quality over large areas, minimizing QD degradation under UV exposure, and expanding the scope of compatible monomer‐QD systems are ongoing concerns. To overcome these barriers, future research should focus on the development of novel photoresist chemistries specifically tailored for QD stability, low‐energy lithographic techniques that reduce photodamage, and ligand architectures engineered to retain or even enhance QD functionality throughout the patterning process.

Beyond high‐resolution pattern definition, the practical advantages of this strategy extend into multiple domains of material and device performance, as illustrated in Figure 9:

• 1)Mechanical Flexibility

FIGURE 9.

Schematic summary of the key advantages offered by polymerization‐enabled direct photolithography for QD patterning. This strategy imparts (i) mechanical flexibility, enabling stretchable and bendable QD films for deformable electronics; (ii) multilayer integration, supporting orthogonal patterning processes across stacked layers with high registration accuracy; (iii) environmental stability, where encapsulation and surface passivation protect against oxygen and moisture; and (iv) dynamic reconfigurability, allowing reversible crosslinking and self‐healing through stimulus‐responsive chemistries.

Polymerization‐induced direct photolithography enables the construction of covalently crosslinked QD‐polymer networks that exhibit outstanding mechanical flexibility and durability. Unlike brittle inorganic passivation strategies, the use of elastic and ductile polymer frameworks allows the resulting QD films to sustain substantial mechanical strain, including stretching, bending, and twisting, without delamination or degradation in photoluminescence performance [96, 97]. This mechanical compliance is particularly advantageous for integration into wearable electronics, foldable displays, and epidermal devices, where materials are subject to frequent deformation. Moreover, the molecular‐level control over crosslinking density and topology enables tunability in mechanical properties, offering pathways to design materials with custom strain tolerance while preserving optical functionality. Such attributes are difficult to achieve through conventional photolithographic or printing‐based patterning methods, underscoring the transformative potential of polymer network‐based lithographic strategies.

• 2)Multilayer Integration

A key strength of polymerization‐induced direct photolithography lies in its compatibility with vertically stacked device architectures. The chemical orthogonality of photo‐reactive components—such as mutually inert thiol‐ene, acrylate, or azide‐based systems—allows for sequential layer‐by‐layer patterning of QDs without cross‐contamination or layer damage [98, 99]. This capability is essential for constructing multilayered structures in advanced optoelectronic systems, such as full‐color vertically stacked QD‐LEDs, multi‐junction photodetectors, and integrated photonic circuits. Because crosslinking reactions can be selectively activated by spatially confined light exposure, each QD layer can be patterned with precise registration and minimal interdiffusion, even when multiple emission colors or functionalities are involved. Furthermore, the use of mild, solvent‐free, or orthogonal development conditions minimize disruption to pre‐existing layers, overcoming one of the main challenges associated with conventional solution‐based fabrication. As display and photonic technologies increasingly require complex 3D integration—whether for resolution enhancement, spectral multiplexing, or functional stacking—polymerization‐based lithography provides a scalable and chemically tunable route to fabricate hierarchical structures with nanoscale control.

• 3)Environmental Stability

Polymerization‐induced direct photolithography inherently provides a robust encapsulation framework for QDs by generating dense, covalently crosslinked polymer matrices during the patterning process [100]. These polymer networks act as effective barriers that protect embedded QDs from environmental degradants such as moisture, oxygen, and ultraviolet radiation. Such passive encapsulation is particularly important for preserving the photophysical properties of QDs under ambient or accelerated aging conditions. Moreover, the compatibility of this process with room‐temperature and solvent‐free fabrication minimizes thermal and chemical stress during device integration. This is crucial for environmentally sensitive nanocrystals such as perovskite QDs, which are prone to rapid degradation. As a result, photopolymerization not only enables high‐resolution patterning, but simultaneously improves the operational reliability and shelf‐life of QD‐based optoelectronic devices in practical settings.

• 4)Dynamic Reconfigurability

One of the most forward‐looking aspects of polymerization‐enabled QD patterning is its capacity for dynamic reconfigurability [45]. By introducing dynamic covalent bonds—such as disulfide exchange or reversible cycloaddition—and incorporating stimuli‐responsive monomers, the resulting polymer networks can exhibit unique properties including self‐healing, reversible crosslinking, and controlled degradation. These chemistries allow QD films to autonomously recover from mechanical damage, be reprocessed or reconfigured on demand, and even degrade in response to environmental triggers such as light, heat, or pH. Such functional adaptability supports the development of transient electronics, recyclable display systems, and smart sensors that respond to external stimuli. Beyond sustainability, this dynamic behavior also facilitates advanced manufacturing concepts such as modular assembly, repairable interfaces, and function‐on‐demand optoelectronic platforms—establishing a new paradigm for reconfigurable nanomaterial systems.

As polymerization‐induced direct photolithography moves toward practical device integration, material‐level considerations such as solubility and photostability of QDs become increasingly critical. The solubility of QDs in polymer matrices directly impacts the homogeneity, optical clarity, and reproducibility of QD–polymer hybrid films—particularly during solution processing. However, for display applications centered on color conversion, long‐term light stability is arguably even more vital. Continuous exposure to high‐intensity excitation light can cause photobleaching, spectral shifts, and degradation of emission efficiency, ultimately compromising display performance. Therefore, enhancing the photostability of QD–polymer composites through advanced surface passivation, oxygen‐ and moisture‐barrier encapsulants, and photochemically inert matrix design should be a top priority. Addressing both solubility and light stability in tandem will be essential to unlock the full commercial potential of this technology in real‐world optoelectronic environments.

Looking forward, several research directions will be pivotal to expand the capabilities of polymerization‐induced lithography. These include:

• The development of visible‐ or near‐IR‐activated photoinitiators for compatibility with sensitive QDs and low‐energy processing.

• Precision engineering of functional ligands that combine strong binding affinity with orthogonal reactivity.

• The integration of smart monomer systems capable of modulating optical, mechanical, or electronic properties post‐patterning.

Moreover, as optoelectronics continue to evolve toward flexible, biocompatible, and hybrid systems, the unique versatility of this technique—its ability to simultaneously define structure and function—makes it ideally positioned to drive progress across disciplines, including stretchable photonics, neuromorphic engineering, and bio‐integrated devices.

In conclusion, polymerization‐induced direct photolithography is not merely a tool for high‐resolution patterning, but a comprehensive material design framework that unites precision fabrication with advanced functionality. Its role in next‐generation QD integration is likely to grow, not only in conventional display technologies, but also in emerging domains where reliability, adaptability, and sustainability are essential.

Conflicts of Interest

The authors declare no conflict of interest.

Biographies

Taehyung Kim is a postdoctoral researcher at the Electronic Hybrid Materials Research Center of the Korea Institute of Science and Technology (KIST). He received his B.S. and Ph.D. from the Department of Energy Engineering at the Ulsan National Institute of Science and Technology (UNIST), Republic of Korea, in 2017 and 2022 under the supervision of Prof. Byeong‐Su Kim. He was a postdoctoral researcher in Prof. Byeong‐Su Kim's group at Yonsei University. His research interests include the design and synthesis of polymeric materials with dynamic covalent bonds, such as covalent organic framework and covalent adaptable networks, along with their application in lithium‐ion batteries and photocatalyst.

Namyoung Gwak is a postdoctoral researcher in the Division of Materials Science and Engineering at Hanyang University. She received her Ph.D. in Materials Science and Engineering from Hanyang University, in 2025. Her research focuses on the synthesis and optical characterization of quantum dots and various nanoparticles, with an emphasis on tailoring their properties through controlled chemical methods. She has also explored the fabrication and analysis of quantum dot/polymer composites, aiming to enhance their applicability in optoelectronic and photonic devices.

Nuri Oh is an assistant professor in the Division of Materials Science and Engineering at Hanyang University. He received his Ph.D. in Materials Science and Engineering from the University of Illinois at Urbana‐Champaign in 2016, where his research focused on the synthesis and optical characterization of nanomaterials. Following this, he conducted postdoctoral research at the University of Pennsylvania from 2016 to 2018. His research interests include the synthesis and optical property analysis of quantum dots and nanoparticles, patterning and array fabrication of these nanomaterials, and their integration into optoelectronic devices.

Tae Ann Kim is a principal researcher at the Electronic Hybrid Materials Research Center of the Korea Institute of Science and Technology (KIST) and an Associate Professor in the Division of Energy & Environment Technology at Korea University of Science and Technology (UST). He received his Ph.D. in Materials Science and Engineering from the University of Illinois at Urbana‐Champaign in 2018, where his research focused on mechanochromic reactions within polymer matrices. Prior to this, he earned both his Master's and Bachelor's degrees in Materials Science and Engineering from Seoul National University. His research interests are centered on the development and application of advanced polymeric materials, particularly emphasizing mechanoresponsive polymers, dynamic covalent networks, and sustainable high‐performance composites.

Kim T., Gwak N., Oh N., and Kim T. A., “Polymerization‐Induced Direct Photolithography of Quantum Dots.” Macromol. Rapid Commun. 46, no. 18 (2025): e00372. 10.1002/marc.202500372