Formulations for preparing optical metal oxide layers

Abstract

The present invention relates to a formulation for preparing an optical metal oxide layer, the formulation comprising a polyoxometallate (POM) complexed to metal oxide nanoparticles (NPs), a method for preparing an optical metal oxide layer using the formulation, and an optical device comprising the optical metal oxide layer.

Description

[Technical Field]

[0001] The present invention relates to a formulation for preparing an optical metal oxide layer, the formulation comprising a polyoxometalate (POM) complexed to metal oxide nanoparticles (NPs), a method for preparing the optical metal oxide layer, and an optical device comprising the optical metal oxide layer. The formulation and method according to the present invention are particularly suitable for preparing metal oxide optical layers for optical applications or devices, such as diffraction gratings for augmented reality (AR) and / or virtual reality (VR) devices. The metal oxide layer exhibits (a) favorable optical properties, such as a high refractive index (RI) of greater than 1.7, preferably greater than 2.0, at wavelengths of 520 nm or less, and / or low absorption of less than 0.1%, and / or low haze formation; (b) favorable mechanical properties, such as low shrinkage; (c) favorable coating properties, such as dense layers and flat one-sided structures; and (d) favorable filling properties, such as uniform filling of topographical features on patterned substrates.

[0002] Embodiments of the present invention enable the preparation of optical metal oxide layers on the surfaces of both patterned and unpatterned substrates. The metal oxide layers can form a variety of structures, such as layers covering the surface of unpatterned substrates and / or fillers covering topographical features, such as gaps, on the surface of patterned substrates, thereby providing highly refractive optical structures. In particular, embodiments of the present invention enable the preparation of advanced optical gap filling with low overburden, thereby enabling easy and cost-effective mass production of complex optical devices by avoiding typical problems that arise when layer deposition or gap filling is performed by physical vapor deposition (PVD) or chemical vapor deposition (CVD) techniques, such as incomplete or excessive gap filling due to unfavorable deposition and layer growth characteristics, such as reduced or increased deposition or growth rates at corners and edges.

[0003] Embodiments of the present invention are particularly suitable for preparing optical metal oxide layers with high refractive index for optical devices such as, for example, diffraction gratings in AR and / or VR devices.

[0004] Finally, the present invention provides an optical device, preferably an AR and / or VR device, comprising an optical metal oxide layer obtainable by the method according to the present invention or prepared by using the formulation according to the present invention. [Background technology]

[0005] State-of-the-art optical devices typically include optical gratings made from composite materials with a substrate as a support and a complex, interlaced pattern thereon, the pattern being composed of different layers or stacks of layers. The creation of such complex, interlaced patterns typically requires a structuring process, which becomes increasingly difficult as the size of the prepared structure dimensions decreases.

[0006] In addition to their wide range of potential uses in various application areas, such as spectroscopy or optical storage systems (CDs, DVDs, etc.), diffraction gratings are a core component of so-called XR devices, which are primarily made of glass. In this context, R stands for "reality," while X denotes different attributes, such as virtual, augmented, or composite. Thus, diffraction gratings form part of the core of the so-called optical engine in XR devices, specifically augmented reality and mixed reality glasses. Virtual reality glasses, when constructed as head-mounted displays, often consist of conventional liquid crystal (LC) organic light-emitting diode (OLED) displays embedded in the device and therefore do not necessarily require a diffraction grating. In contrast, augmented reality and mixed reality glasses are designed to enable consumers to obtain the best visual impression of their environment, as if they were not wearing glasses at all. However, they also allow for the provision and support of digital information and the projection of it into an individual's field of vision. Additional digital information is collected from recognizing and analyzing the environment, allowing the individual to examine or view their current view. To transmit supporting digital information and project it into an individual's eye, augmented reality or mixed reality glasses include an information supply unit coupled to an optical waveguide system that transmits optically encoded supporting information directly to the glasses' lenses. Here, the information passes through a diffraction grating that couples incident light into the lens and splits it according to its angular information and its spectral band by diffraction. After light incoupling, the lens functions as a waveguide that allows light to be transmitted to and within the individual's pupil. The location of the light incoupling is independent of any preferred location and, therefore, independent of the influence of technical needs. The transverse direction of light within the lens is determined by the diffraction grating, which diffracts or splits the light. At specific locations within the lens, second and third diffraction gratings function to change the transverse direction of the light, thereby projecting it into the user's pupil. Light traversal within the glasses is achieved by total internal reflection (TIR) ​​of light, which bounces several times between glass interfaces until it reaches another diffraction grating that changes the internal TIR direction of the light (see Figure 2).The second and third gratings can be geometrically aligned in different directions relative to the first and incoupling gratings, for example, by a specific angular distortion of the longitudinal axis, thus changing the propagation direction of the totally internally reflected light. Needless to say, the lens itself or the material from which it is made must not be absorbing. Otherwise, the auxiliary information will not reach the user's pupil, or will only reach it with a significantly reduced light intensity. This process works regardless of whether a reflective or transmissive grating is used. Typically, lenses are equipped with both types of gratings to properly guide the light. It should also be noted that there are differences in the optical performance of reflective and transmissive gratings, but these are not of any further importance in the context of the present invention. The basic structure of the gratings is very similar, which is more important in this regard.

[0007] Nevertheless, there are different designs and structures for achieving waveguides, such as surface relief (SR) or volume phase holographic (VPH) gratings. Both types are very similar in appearance. In the simplest case, the grating is somehow attached to the surface of a waveguide material, here a lens. The grating itself consists of an array of microstructures, primarily, but not limited to, trenches in a first material type, material O1, with a refractive index RI01. The trench geometries can range from rectangular to V-shaped trenches, U-shaped trenches, etc. The width, including structures with different widths, the geometry of the trenches, their pitch, as well as their depth, including different depths, are specifically designed to affect the diffraction pattern of the diffracted incident light.

[0008] In the case of SR gratings (SRGs), trenches or structures of a first material type (Material O1) with a refractive index (RI01) are filled with a second material type (Material O2) with a refractive index (RI02), where RI02 is incrementally different from RI01 (see Figures 1 and 3). For completeness, it should be mentioned that Material O1 or Material O2 may be composed of a stack of structured layers, each containing different material compositions with different refractive indices, stacked on top of each other, thereby forming Material O1 or Material O2 with an effective or graded refractive index RI01 or RI02, respectively. Note that the (effective or graded) refractive indices RI01 and RI02 depend on the refractive index of the waveguide or lens material of the eyeglasses. When glass lenses with a high refractive index (n03 > 1.46) are used, the (effective or graded) refractive indices of Material O1 and Material O2 are considered higher than the refractive index of the lens itself, thereby allowing an RI value of 2.0 to be reached or exceeded. High performance gratings, particularly SR type high performance gratings, can be fabricated using standard lithography and deposition techniques known from microfabrication, for example, integrated circuit manufacturing.

[0009] Such standard techniques typically involve physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes and often suffer from incomplete gap filling due to unfavorable deposition and / or layer growth characteristics, including increased deposition and / or growth rates at corners and edges. Such incomplete gap filling results in the formation of voids within the structures filled by the PVD and CVD materials. In addition to the formation of voids, the surface of the substrate is covered by a PVD and / or CVD layer that is approximately as thick as the maximum depth of the deepest structure filled by the deposited gap-fill material (see FIGS. 4 and 5). However, depending on the application, it may be necessary to expose the surface of the substrate and make it available for further processing. As a result, the undesired overburden layer from PVD or CVD must be removed, for example, by chemical mechanical planarization (CMP), without harming the underlying original substrate surface. While CMP is very well established in integrated circuit manufacturing processes, CMP is a time-consuming and expensive process that can be considered a potential economic drawback for the mass production of cutting-edge optical devices, particularly diffraction gratings. Therefore, it is desirable to have a solution for advanced, cost-effective fabrication of optical gratings where gap filling does not require CMP (see FIG. 6).

[0010] The present invention addresses various shortcomings of the techniques for preparing optical gratings for state-of-the-art optical devices as described above, with a focus on improved optical properties, improved mechanical properties, improved coating properties, and improved filling properties.

[0011] Means to solve the problem It is an object of the present invention to provide formulations and methods for preparing optical metal oxide layers, which are particularly suitable for optical applications and can be used in optical devices, such as diffraction gratings for AR and / or VR devices. The resulting optical metal oxide layers exhibit (a) favorable optical properties, such as a high refractive index (RI) greater than 1.7, preferably greater than 2.0, at wavelengths of 520 nm and shorter, low absorption, and low haze formation, (b) favorable mechanical properties, such as low shrinkage, (c) favorable coating properties, such as a dense layer and a smooth surface structure, and (d) favorable filling properties, such as uniform filling of topographical features on patterned substrates.

[0012] It is a further object of the present invention to provide a formulation and a method that allows for the easy and cost-effective preparation of optical metal oxide layers.

[0013] It is a further object of the present invention to enable the preparation of optical metal oxide layers on the surface of patterned or unpatterned substrates, which can form a variety of structures, such as, for example, a layer covering the surface of an unpatterned substrate and / or a filler covering topographical features, such as, for example, gaps, on the surface of a patterned substrate, thereby providing highly refractive optical structures.

[0014] It is therefore an object of the present invention to provide formulations and methods for preparing optical metal oxide layers, which methods allow the preparation of high optical gap filling with low overburden, thus enabling easy and cost-effective mass production of complex optical devices.

[0015] A further object of the present invention is to provide a method for preparing optical metal oxide layers, which avoids typical problems that arise when layer deposition or gap filling is performed by PVD or CVD techniques, such as unfavorable deposition and layer growth characteristics, such as incomplete or excessive gap filling due to reduced or increased deposition or growth rates at corners and edges.

[0016] It is an object of the present invention that the metal complexes and formulations are particularly suitable for the preparation of metal oxide optical layers with high refractive index and at the same time low absorption (light loss) for optical devices such as, for example, diffraction gratings in AR and / or VR devices.

[0017] Finally, it is an object of the present invention to provide an optical device, preferably an AR and / or VR device, comprising an optical metal oxide layer obtainable by the method according to the present invention or prepared by using the formulation according to the present invention, thereby exhibiting the beneficial effects mentioned above. Summary of the Invention

[0018] The inventors have surprisingly found that the above objects are achieved individually or in any combination by a formulation for preparing an optical metal oxide layer, said formulation comprising: (i) a polyoxometallate moiety of formula (Ia), and [Q l ] n+ [X z Y p O y ] n- (Ia) Nanoparticles of formula (Ib), M i M' j M'' f O k (Ib) [In the formula, each Q independently represents a cation, preferably the cation is selected from the group consisting of ammonium cation, alkali metal cation, alkaline earth metal cation; l is any number ranging from 1 to 20, preferably from 1 to 10; n is the total positive charge n+ of l cations Q and polyanion [X z Y p O y ] is a number representing the corresponding negative charge n-.

[0019] X is a heteroatom such as B, Si, Ge, P, Al, As, or Sb; Y is a metal, preferably a transition metal; z is 0 to 20; p is 1 to 100; y is 2 to 400; M, M', and M'' are each independently a metal; i, j, and f are each independently an integer or fractional number from 0 to 10, with the proviso that at least one of l, j, and f is not 0; k is any number ranging from 1 to 20, preferably from 1 to 5. and a complex comprising (ii) one or more formulation vehicles.

[0020] Additionally, there is provided a method for preparing an optical metal oxide layer, the method comprising the following steps (a) to (c): (a) (i) a complex comprising a polyoxometallate moiety of formula (Ia) and a nanoparticle of formula (Ib); (ii) providing a formulation comprising one or more formulation vehicles; (b) applying the formulation onto the surface of the substrate; (c) converting the formulation into an optical metal oxide layer on the surface of the substrate.

[0021] Further provided is an optical device comprising an optical metal oxide layer obtainable or obtainable by a method according to the above-described preparation method.

[0022] The present invention further relates to the use of the above formulations for forming optical metal oxide layers.

[0023] Preferred embodiments of the invention are described below and set out in the dependent claims. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic cross-sectional view of an SR grating having material 01 and material 02, where the refractive index IR01 of material 01 is incrementally different from the refractive index IR02 of material 02.

[0025] [Figure 2] Schematic cross-section of an SR grating, which allows for optical diffraction, including propagation of diffracted light within a waveguide (e.g., a lens) by total internal reflection.

[0026] [Figure 3] FIG. 1 is a schematic cross-sectional view of an SR grating providing gaps (trenches) that are filled with a high refractive index material (material 02), where the refractive index of material 02 is incrementally different from the refractive index of material 01 adjacent to the gaps (trenches).

[0027] [Figure 4] Schematic of a PVD or CVD mediated gap filling process and removal of unwanted overburden.

[0028] [Figure 5] Schematic of a PVD or CVD mediated gap-fill process that creates and leaves voids in the gap and deposited layer.

[0029] [Figure 6] Schematic of a gap-filling process using a formulation containing a metal complex of the present invention or the formulation being converted to a metal oxide.

[0030] [Figure 7A] A comparison of the UV-Vis spectrum of a diluted sample of the supernatant solution (A) with the UV-Vis spectrum of a diluted sample of the lysis product obtained using the standard method and the solvent method (B) is shown. [Figure 7B] A comparison of the UV-Vis spectrum of a diluted sample of the supernatant solution (A) with the UV-Vis spectrum of a diluted sample of the lysis product obtained using the standard method and the solvent method (B) is shown.

[0031] [Figure 8] FT-IR spectra of dried samples of products obtained using purification methods 1 and 2 are shown.

[0032] [Figure 9] 1 shows the reaction mixture with the product precipitating over time after adding 10% (v / v) solvent.

[0033] [Figure 10] Figure 1 shows a pure solution of K8Nb6O19 in a mixed solvent system of additive solvent, isopropanol, and water.

[0034] [Figure 11] Figure 1 shows the refractive index dependence on the PW-TiO2 weight fraction for PW-TiO2 / PW-SnO2 mixtures.

[0035] [Figure 12] 1 shows the refractive index of blends PW-TiO2 and PW-A as a function of measured PW-TiO2 weight percent content on thin films deposited on Si substrates and cured at 300° C.

[0036] [Figure 13] Figure 1 shows the refractive index of PW-TiO2 and PW-SnO2 mixtures (PW-TiO2 weight fraction 0.94) as a function of the weight fraction of various amounts of PW-A added.

[0037] [Figure 14] Figure 1 shows surface feature filling after spin-coating a 5 wt% PW-SnO2 formulation, soft-baking at 100°C for 1 minute, and hard-baking at 300°C for 10 minutes.

[0038] [Figure 15A] Figure 1 shows surface feature filling after drop casting 10 wt% PW-SnO2 and 0.5 wt% BYK348 in H2O, soft firing at 100°C for 1 minute, and firing at 300°C for 10 minutes.

[0039] [Figure 15B] Feature filling after spin-coating 10 wt% PW-SnO2 and 0.5 wt% BYK348 in H2O, soft-baking at 100°C for 1 minute, and baking at 200°C for 10 minutes.

[0040] [Figure 16] Feature filling is shown after spin-coating the mixture of Example T3 (PW-SnO2 / PW at a 1.8 / 1 weight ratio), soft-baking at 100°C for 1 minute, and hard-baking at 300°C for 10 minutes.

[0041] [Figure 17A] Figure 17 shows the surface feature filling after spin-coating the mixture NbO-SnTiO+NbO-A and pre-baking at 100 °C for 1 minute. Two trench widths are shown: 114 nm (Figure 17A) and 87.5 nm (Figure 17B). [Figure 17B] Figure 17 shows the surface feature filling after spin-coating the mixture NbO-SnTiO+NbO-A and pre-baking at 100 °C for 1 minute. Two trench widths are shown: 114 nm (Figure 17A) and 87.5 nm (Figure 17B).

[0042] [Figure 17C] Figure 1 shows surface feature filling after spin-coating the mixture NbO-Sn0.25Ti0.75O2+NbO-A and hard-baking at 300°C for 10 minutes, followed by soft-baking at 100°C for 1 minute. A trench width of 84 nm is shown.

[0043] [Figure 18A] The surface feature filling is shown after spin-coating the mixture NbO-SnO2\TiO2 25 / 75%+NbO, soft-baking at 100 °C for 1 minute, and hard-baking at 300 °C for 10 minutes. The trench widths are 114 nm (Figure 18A) and 131 nm (Figure 18B). [Figure 18B] The surface feature filling is shown after spin-coating the mixture NbO-SnO2\TiO2 25 / 75%+NbO, soft-baking at 100 °C for 1 minute, and hard-baking at 300 °C for 10 minutes. The trench widths are 114 nm (Figure 18A) and 131 nm (Figure 18B).

[0044] [Figure 18C] Two layers of the mixture NbO-SnO2\TiO2 25 / 75% + NbO-A were spin-coated without soft-baking between layers, and after spin-coating the second layer, a final soft-baking at 100°C for 1 minute was performed. After the soft-baking, a hard-baking at 300°C for 10 minutes was performed. Surface feature filling is shown.

[0045] [Figure 19A] 1 shows an exemplary scheme of POM complexed to nanoparticles.

[0046] [Figure 19B] To illustrate the calculation of the core radius, we show the packaging of POM on the surface of an NP, where the radius of the NP is much larger than the radius of the POM.

[0047] List of Reference Numbers 1 Material with RI02 2 Materials with RI0101 3. Substrate (e.g., glass) 4 Diffraction of incident light represented by thick arrows 5 Total Internal Reflection (TIR) ​​of Light 6 Waveguide 7 Structured layer stack with gaps (trench) 8. Substrate (e.g., glass or silicon) 9 Overburden of materials (e.g., high refractive index materials or highly etch-resistant materials) 10. Materials that provide gap filling (e.g., high refractive index materials or highly etch resistant materials) 11. Void 12 Formulations (e.g., inks) of high refractive index materials (e.g., metal oxide precursors) 13 High refractive index materials (e.g., metal oxides) that provide gap filling with arbitrary concave shapes 14 Overburden layer (optional) 15 Energy 100 nanoparticles (NP) 102 Polyoxometalate (POM) 104 Projection of POM onto the NP sphere 106 radius R DETAILED DESCRIPTION OF THE INVENTION

[0048] definition In the context of the present invention, the term "formulation medium" or the plural "formulation medium" as used herein means one or more compounds that act as a solvent, suspending agent, carrier and / or matrix for the complex and any other ingredients contained in the formulation. A formulation medium is generally an inert compound that does not react with the complex and the other ingredients. A formulation medium may be a liquid compound, a solid compound, or a mixture thereof. A preferred formulation medium is water.

[0049] In this specification, when a numerical range is indicated using "to", it is intended to include both ends of the range. For example, 1 to 10 means 1 or more and 10 or less.

[0050] As used herein, the term "surfactant" refers to an additive that reduces the surface tension of a given formulation.

[0051] As used herein, the term "wetting and dispersing agent" refers to an additive that increases the diffusivity and permeability of a given formulation, thus reducing the tendency of molecules to stick together.

[0052] As used herein, the term "adhesion promoter" refers to an additive that increases the adhesion of a given formulation.

[0053] As used herein, the term "coordinating surfactant" refers to an additive that coordinates metal ions and acts as a surfactant.

[0054] As used herein, the term "viscosity enhancer" refers to an additive that increases the viscosity of a given formulation.

[0055] As used herein, the term "optical device" refers to a device containing one or more optical components for shaping a light beam, including, but not limited to, gratings, lenses, prisms, mirrors, optical windows, filters, polarizing optics, UV and IR optics, and optical coatings. Preferred optical devices in the context of the present invention are augmented reality (AR) glasses and / or virtual reality (VR) glasses.

[0056] As used herein, the term "metal" includes alkali metals, alkaline earth metals, transition metals, rare earth elements, post-transition metals, actinide elements, metalloids, and lanthanide elements.

[0057] As used herein, the term "post-transition metal" relates to Al, Ga, In, Sn, Ti, Pb, Bi, Nh, Fl, Mc, and Lv.

[0058] As used herein, the term "metalloid" refers to B, Si, Ge, As, Sb, Te, and Po.

[0059] As used herein, the cation "Q" can be a proton, an ammonium cation, an alkali metal cation, and an alkaline earth metal cation.

[0060] As used herein, the term "nanoparticle" or "NP" refers collectively to an individual unit having a structure with at least one dimension on the nanometer scale (i.e., from 1 nm to 1 μm). The term "nanoparticle" includes quantum dots, spherical and pseudo-spherical particles, faceted particles, nanorods, nanowires, tetrapods, anisotropic particles, nanoplatelets, and other suitable particles. Furthermore, the term "nanoparticle" includes single-crystalline nanoparticles (i.e., nanocrystals), polycrystalline nanoparticles, and amorphous nanoparticles. The nanoparticles referred to herein are those having the formula (Ib): M i M' j M'' f O k (Ib) wherein M, M', and M'' are each independently a metal; i, j, and f are each independently an integer or fractional number from 0 to 10, with the proviso that at least one of l, j, and f is not 0; and k is any number ranging from 1 to 20, preferably from 1 to 5.

[0061] Polyoxometallates or "POMs" as referred to herein are those having the formula (Ia): [Q l ] n+ [X z Y p O y ] n- (Ia) [In the formula, each Q independently represents a cation, preferably the cation is selected from the group consisting of ammonium cation, alkali metal cation, alkaline earth metal cation; l is any number ranging from 1 to 20, preferably from 1 to 10; n is the total positive charge n+ of l cations Q and polyanion [X z Y p O y ] is a number representing the corresponding negative charge n-.

[0062] X is a heteroatom such as B, Si, Ge, P, Al, As, or Sb; Y is a metal, preferably a transition metal; z is 0 to 20; p is 1 to 100; and y is 2 to 400.

[0063] The complexes referred to herein relate to metal oxide nanoparticles complexed to a POM, which acts as a ligand. Figure 15A shows a schematic diagram of such a complex comprising a polyoxometallate moiety according to Formula Ia and a nanoparticle according to Formula Ib. In some instances, a single M, M', and M'' of the nanoparticle can be considered part of the polyoxometallate, e.g., Na[PW] complexed to TiO2 when the polyoxometallate is a lacunary polyoxometallate. 11 O39 The polyoxometalate moiety of [PW 11 O 39 Ti]-O - It should be understood that when reference is made herein to POM complexed to NPs, the foregoing depiction is also encompassed.

[0064] The use of POM as a protective ligand complexed to NPs to obtain POM-NP-isolatable water-soluble nanostructures is known from the following literature: (1) Y. Wang, I. Weinstock, Chem. Soc. Rev., 2012, 41, 7479-7496.

[0065] (2) M. Raula, G. Gan Or, M. Saganovich, O. Zeiri, Y. Wang, M Chierotti, R. Gobetto, I. Weinstock, Angew. Chem. Intl. Ed. 2015, 54, 12416-12421.

[0066] (3) Anna Llordes, Aaron T. Hammack, Raffaella Buonsanti, Ravisubhash Tangirala, Shaul Aloni, Brett A. Helmsa and Delia J. Milliron, J. Mater. Chem., 2011, 21, 11631-11638.

[0067] Preferred Embodiments Formulations for preparing optical metal oxide layers In a first aspect, there is provided a formulation for preparing an optical metal oxide layer, the formulation comprising: (i) a polyoxometalate moiety of formula (Ia), and [Q l ] n+ [X z Y p O y ] n- (Ia) Nanoparticles represented by formula (Ib), M i M'j M'' f O k (Ib) [In the formula, each Q independently represents a cation, preferably the cation is selected from the group consisting of ammonium cation, alkali metal cation, alkaline earth metal cation; l is any number ranging from 1 to 20, preferably from 1 to 10; n is the total positive charge n+ of l cations Q and polyanion [X z Y p O y ] is a number representing the corresponding negative charge n-; X is a heteroatom such as B, Si, Ge, P, Al, As, or Sb; Y is a metal, preferably a transition metal; z is 0 to 20; p is 1 to 100; y is 2 to 400; M, M', and M'' are each independently a metal; i, j, and f are each independently an integer or fractional number from 0 to 10, with the proviso that at least one of l, j, and f is not 0; k is any number ranging from 1 to 20, preferably from 1 to 5. and a complex comprising (ii) one or more formulation vehicles.

[0068] Preferably, the TiO2 nanoparticles are complexed with (Na7[α-PW 11 O 39 ]), Na3[PMo complexed with TiO2 12 O 40 ], K6[P2W complexed with TiO2 18 O 62 ], K6[P2Mo complexed with TiO2 18 O 62 ], or Q complexed to TiO2 l [SiW 11 O 39 ] are excluded from the formulation according to the first aspect.

[0069] In some embodiments, the complex has formula (I): ([Q l ] n+ [POM] n- ) m (NP) r (I) [In the formula, l is any number ranging from 1 to 40; POM is a polyoxometalate ligand represented by formula (Ia); n is the total positive charge of Q + and the corresponding negative charge n of the polyoxometalate ligand - where n can be any number ranging from 2 to 20; NP is a nanoparticle represented by formula (Ib); m represents the number of polyoxometalate ligands per nanoparticle and is any number ranging from 1 to 5000; and r is any number ranging from 1 to 20,000 and represents the experimental metal oxide units in the nanoparticles.

[0070] In formula (I) or (Ia), each Q independently represents a cation selected from the group consisting of a proton, an ammonium cation, an alkali metal cation, and an alkaline earth metal cation. In a preferred embodiment, each Q independently represents an alkali metal, such as Na or K.

[0071] Polyoxometalates (POMs) can be viewed as generally anionic clusters formed from monomeric oxo species of transition metals bearing one or more bridging oxygen atoms. The basic POM backbone is referred to herein as "Y p O y " where p and y are the total amount of metal ions and oxygen ions, respectively. Such POMs are also called isopolyanions or isopolyoxometalates. Apart from Y and O, other elements, labeled X herein, can be part of the POM framework. As a general rule, the X element is either tetracoordinated or hexacoordinated, and Y p O yAt the center of the shell or cage (X may also be called the "core heteroatom"). When X is present, the POM may be called a heteropolyanion or heteropolyoxometalate, which means that [X z Y p O y ] n- where z>0. In some embodiments, the POM may be represented by, for example, [PW 11 O 39 ] 7- and other Lacunary POMs.

[0072] "X" is sometimes referred to as the primary heteroatom or central heteroatom. Generally, there are no strict physical requirements for this position, so any element can participate as X in a POM cluster. Exemplary "X"s include, but are not limited to, B, Si, Ge, P, Al, As, Sb, etc. "Y" is sometimes referred to as a secondary atom, peripheral atom, or adduct atom. Y may be one or more different metals. Typically, only certain metals are found in such compounds. In anions where more than one Y adduct type is present in the framework, the molecule is sometimes referred to as a mixed adduct cluster. Exemplary "Y"s include, but are not limited to, W, Nb, V, Ta, Ti, Zr, Hf, Mo, Zn, In, or Sn.

[0073] In some embodiments, the POM is a heteropolyoxometalate, preferably [Q7][PW 11 O 39 ], for example, [Na7][PW 11 O 39 In some embodiments, the POM is an isopolyoxometalate, preferably [Q][NbO 19 ], for example, [K8][Nb6O 19 ].

[0074] In some embodiments, Z is 0. In preferred embodiments, X is P, Si, or Al, and / or Y is W, Nb, V, Ta, Ti, Zr, Hf, Mo, Zn, In, or Sn. In particularly preferred embodiments, the POM is a heteropolyoxotungstate or an isopolyoxoniobate. Particularly preferred heteropolyoxotungstates are Q7[PW 11 O 39 ], where each Q is individually Na or K, preferably where Q is Na. A particularly preferred isopolyoxoniobate is Q8[Nb6O 19 wherein each Q is individually Na or K, preferably wherein Q is K.

[0075] Each nanoparticle may contain "r" units of Formula Ib. The number of POMs complexed to the NP, "m," may increase with increasing r as a function of crystalline form. "m" may be any number ranging from 1 to 5,000, and r may be any number ranging from 1 to 20,000. The complex may include a POM covalently complexed with the NP.

[0076] In some embodiments, the nanoparticles represented by Formula Ib are crystalline and are referred to herein as nanocrystals.

[0077] In some embodiments, M, M', and M" are each independently Ba, Sr, Ti, Zr, Nb, Hf, Ta, Zn, Al, In, Sn, or Ce, optionally in a higher oxidation state. In preferred embodiments, M, M', and M" are each independently Ba(II), Sr(II), Ti(III), Ti(IV), Zr(IV), Nb(V), Nb(III), Hf(IV), Ta(V), Zn(II), Al(III), In(III), Sn(II), Sn(IV), or Ce(IV).

[0078] In particularly preferred embodiments, M' is Ti, optionally Ti(IV), and / or M is Sn, optionally Sn(IV).

[0079] In further preferred embodiments, f is 0. In even more preferred embodiments, f is zero and either k or j is also 0, or k is less than 1 and j is 1-k. In some embodiments, i and j are each individually a fraction of 1. In some embodiments, the nanoparticles represented by Formula 1b are, for example, Sn i T 1-i O2, where i is any fraction between 0 and 1, e.g., 0.05, 0.12, 0.15, 0.20, 0.25, 0.35, 0.75. The term "fraction of 1" refers to any fraction between 0 and 1, e.g., 0.01, 0.008, 0.12, 0.17, 0.23, 0.28, 0.30, 0.35, 0.36, 0.41, 0.47, 0.50, 0.62, 0.77, 0.81, 0.98, or 0.99. Non-limiting examples of mixed metal oxides include Sn 0.13 Ti 0.87 O2, Sn 0.54 Ti 0.46 O2, Sn 0.25 Ti 0.75 O2 and Sn 0.5 Ti 0.5 O2. Mixed metal oxide nanoparticles are also referred to herein as doped metal oxide nanoparticles. For example, Sn 0.13 Ti 0.87 O2 is sometimes called Sn-doped titanium oxide nanoparticles. Mixed metal oxide nanoparticles, such as Sn 0.13 Ti 0.87 O2 may make it possible to adjust the refractive index by adjusting the ratio between M and M', for example the ratio between Sn and Ti, to find the optimum ratio.

[0080] In some embodiments, the nanoparticles are SnO2, CeO2, ZrO2, TiO2, NbO2, HfO2, or Ta2O5.

[0081] In a preferred embodiment, the complex according to formula (I) is a heteropolyoxotungstate, such as ([Na7][PW 11 O 39]), and TiO2NPs or SnO2NPs, or mixed metal oxide NPs, e.g., Sn x T 1-x In a further preferred embodiment, the complex according to formula (I) is a polyoxoniobate, such as ([K][NbO 19 ]) and TiO2NPs or SnO2NPs, or mixed metal oxide NPs, e.g. Sn x T 1-x Complexed to O2NP.

[0082] In a preferred embodiment, the complex according to formula (I) is complexed to SnO2 nanoparticles ([Na7][PW 11 O 39 ]), complexed to SnO2 nanoparticles ([K8][Nb6O 19 ]), Sn 0.5 Ti 0.5 O2 nanoparticles complexed with ([K8][Nb6O 19 ]), Sn 0.25 Ti 0.75 O2 nanoparticles complexed with ([K8][Nb6O 19 ]), Sn 0.13 Ti 0.87 O2 nanoparticles complexed with ([K8][Nb6O 19 ]), complexed to TiO2 nanoparticles (K8[Nb6O 19 ]), Sn 0.54 Ti 0.46 O2 complexed to (K8[Nb6O 19 ]), or Na7[PW complexed to TiO2 nanoparticles 11 O 39 ].

[0083] In a preferred embodiment, the complex according to formula (I) is ([Na7][PW 11 O 39 ]) m (SnO2) r , ([K8][Nb6O 19 ]) m (SnO2) r , (K8[Nb6O 19 ]) m (Sn 0.5 Ti 0.5O2) r , ([K8][Nb6O 19 ]) m (Sn 0.25 Ti 0.75 O2) r , ([K8][Nb6O 19 ]) m (Sn 0.13 Ti 0.87 O2) r , ([K8][Nb6O 19 ]) m (Sn 0.54 Ti .46 O2) r , ([K8][Nb6O 19 ]) m (TiO2) r , or ([Na7][PW 11 O 39 ] m (TiO2) r In the formula, preferably, m is any number in the range of 1 to 5,000, and r is any number in the range of 1 to 20,000, and more preferably, m is any number in the range of 1 to 1,000, and r is a number in the range of 1 to 6,000.

[0084] In some embodiments, the formulation further comprises (iii) one or more additives, each of which may be individually selected from the group consisting of a further complex comprising a polyoxometalate represented by Formula (Ia) and a nanoparticle represented by Formula (Ib), a polyoxometalate represented by Formula (Ia), a wetting agent, a dispersing agent, an adhesion promoter, a polymer matrix, and a surfactant.

[0085] The presence of one or more additives in the formulation according to the invention can improve the properties of the optical metal oxide layer obtained or obtainable by said formulation, such as material hardness, shrinkage, refractive index, transparency, absorbance, and haze suppression.

[0086] In some embodiments, the formulation further comprises a polyoxometalate represented by formula (I) as an additive. l )[PW 12 O 40 ] or (Ql )[NbO 19 is a preferred additive. In some embodiments, the polyoxometallate comprises the same elements as the polyoxometallate portion of the complex of formula (I).

[0087] In particularly preferred embodiments, each Q independently represents an alkali metal cation, preferably K or Na.

[0088] In a further preferred embodiment, the formulation comprises (i) a first complex represented by formula (I), (ii) one or more formulation vehicles, and (iii) a second complex represented by formula (I), wherein the first and second complexes of formula (I) are not the same.

[0089] In a further preferred embodiment, the formulation comprises (i) a first complex represented by formula (I), (ii) one or more formulation vehicles, and (iii) a second complex represented by formula (I), wherein the first and second complexes of formula (I) are different.

[0090] In a preferred embodiment, the formulation comprises: (i) Complexed to SnO2 nanoparticles ([Na7][PW 11 O 39 ]), and (ii) one or more formulation vehicles; (iii) ([Na7][PW 11 O 39 ]), and optionally, Na3PW 12 O 40 * and a further complex comprising HO.

[0091] In a preferred embodiment, the formulation comprises: (i) heterooxopolytungstates, such as those complexed to nanoparticles according to formula (Ib) ([Q7][PW 11 O 39 ]) or isopolyoxoniobates, such as Q8[NbO 19 and a complex comprising (ii) one or more formulation vehicles; (iii) polyoxometalates, preferably ([Q l ][PW 12 O 40 ]) or ([Q l ][NbO 19 ]) and,

[0092] Preferred surfactants are surface-active materials, preferably comprising surface-active metal oxides and / or surface-active organic compounds, which may include nonionic surfactants, anionic surfactants, and amphoteric surfactants, which may be coordinating or non-coordinating.

[0093] Examples of nonionic surfactants include those selected from one or more members of the group consisting of polyoxyethylene alkyl ethers, such as polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and polyoxyethylene cetyl ether; polyoxyethylene fatty acid diesters; polyoxyethylene fatty acid monoesters; polyoxyethylene polyoxypropylene block polymers; acetylene alcohols; acetylene glycols; polyethoxylates of acetylene alcohols; and acetylene glycol derivatives, such as polyethoxylates of acetylene glycol. Fluorine-containing surfactants, such as FLUORAD (trade name, manufactured by Sumitomo 3M Limited), MEGAFAC (trade name, manufactured by DIC Cooperation), and SURFLON (trade name, manufactured by Asahi Glass Co., Ltd.), or organosiloxane surfactants, such as KP341 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), are also included. Examples of the acetylene glycol include 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,5-dimethyl-1-hexyn-3-ol, 2,5-dimethyl-3-10hexyne-2,5-diol, and 2,5-dimethyl-2,5-hexanediol.

[0094] Examples of anionic surfactants include ammonium salts or organic amine salts of alkyldiphenyletherdisulfonic acids, ammonium salts or organic amine salts of alkyldiphenylethersulfonic acids, ammonium salts or organic amine salts of alkylbenzenesulfonic acids, ammonium salts or organic amine salts of polyoxyethylene alkylethersulfonic acids, and ammonium salts or organic amine salts of alkylsulfuric acids.

[0095] Examples of amphoteric surfactants include 2-alkyl-N-carboxymethyl-N-20 hydroxyethylimidazolium betaine, lauric acid amidopropyl hydroxysulfone betaine, and the like.

[0096] Preferred surface-active metal oxides are selected from the list consisting of aluminum oxide, calcium oxide, silica, and zinc oxide. Such surface-active metal oxides are preferably present as fine powders, more preferably as nanoparticles, which are optionally surface-treated.

[0097] Preferred surface-active organic compounds are surface-active non-polymeric compounds or surface-active polymeric organic compounds, the surface-active non-polymeric compounds being preferably selected from the list consisting of alcohols, alkoxylates, aromatics, ketones, esters, modified ureas, silanes, siloxanes, and soap-based foam stabilizers, optionally functionalized and / or modified, and the surface-active polymeric compounds being preferably selected from the list consisting of hydroxy polyesters, maleic acid resins, polyacrylates, polyethers, polyesters, polysilanes, silicone resins, and waxes, optionally functionalized and / or modified, and optionally present as copolymers. In a preferred embodiment, the surface-active organic compounds are used as a solution.

[0098] Preferred silanes are polyether-modified silanes, polyester-modified silanes, and polyether-polyester-modified silanes. Preferred siloxanes are polyether-modified siloxanes, polyester-modified siloxanes, and polyether-polyester-modified siloxanes.

[0099] Preferred polyacrylates are modified polyacrylates, preferably silicone-modified polyacrylates, polyether macromer-modified polyacrylates, and optionally silicone- and polyether macromer-modified polyacrylates present as copolymers.

[0100] Preferred polysilanes are polyether-modified polysilanes (for example, PEG-silanes 6 to 9), polyester-modified polysilanes, and polyether-polyester-modified polysilanes.

[0101] Preferred silicone resins are polyether-modified polysiloxanes, preferably polyether-modified polydialkylsiloxanes, more preferably polyether-modified polymethylalkylsiloxanes, most preferably polyether-modified polydimethylsiloxanes and polyether-modified hydroxy-functional polydimethylsiloxanes; polyester-modified polysiloxanes, preferably polydialkylsiloxanes, more preferably polyester-modified polymethylalkylsiloxanes, most preferably polyester-modified polydimethylsiloxanes and polyester-modified hydroxy-functional polydimethylsiloxanes; polyether-polyester-modified polysiloxanes, preferably polyether-polyester-modified polydialkylsiloxanes, more preferably polyether-polyester-modified polymethylalkylsiloxanes, most preferably polyether-polyester-modified polydimethylsiloxanes and polyether-polyester-modified hydroxy-functional polydimethylsiloxanes; epoxy-functional polysiloxanes, preferably epoxy-functional polydialkylsiloxanes, more preferably epoxy-functional polymethylalkylsiloxanes, most preferably Preferably, epoxy-functional polydimethylsiloxane; acrylic-functional polysiloxane, preferably acrylic-functional polydialkylsiloxane, more preferably acrylic-functional polymethylalkylsiloxane, most preferably acrylic-functional polydimethylsiloxane; polyether-modified acrylic-functional polysiloxane, preferably polyether-modified acrylic-functional polydialkylsiloxane, more preferably polyether-modified acrylic-functional polymethylalkylsiloxane, most preferably polyether-modified acrylic-functional polydimethylsiloxane; polyester-modified acrylic-functional polysiloxane, preferably polyester-modified acrylic-functional polydialkylsiloxane, more preferably polyester-modified acrylic-functional polymethylalkylsiloxane, most preferably polyester-modified acrylic-functional polydimethylsiloxane; and aralkyl-modified polysiloxane, preferably aralkyl-modified polydialkylsiloxane, more preferably aralkyl-modified polymethylalkylsiloxane, most preferably aralkyl-modified polydimethylsiloxane, optionally present as a copolymer.

[0102] Preferred surfactants are commercially available from BYK-Chemie GmbH (Wesel, Germany) and are offered as surface additives. Preferred surfactants include BYK-300, BYK-301, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315N, BYK-320, BYK-322, BYK-323, BYK-325N, BYK-326, BYK-327, BYK-329, BYK-330, BYK-331, BYK-332, BYK-333, BYK-342, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-350, BYK-352, BYK-353, BYK-354, BYK-355, BYK-356, BYK-357, BYK-358, BYK-359, BYK-360, BYK-361, BYK-362, BYK-363, BYK-364, BYK-365, BYK-366, BYK-367, BYK-368, BYK-369, BYK-370, BYK-371, BYK-372, BYK-373, BYK-374, BYK-375, BYK-376, BYK-377, BYK-378, BYK-379, BYK-380, BYK-381, BYK-382, BYK-383, BYK-384, BYK K-354, BYK-355, BYK-356, BYK-358N, BYK-359, BYK-360P, BYK-361N, BYK-364P, BYK-366P, BYK-368P, BYK370, BYK375, BYK-377, BYK-378, B YK-381, BYK-390, BYK-392, BYK-394, BYK-399, BYK-2616, BYK-3400, BYK-3410, BYK-3420, BYK-3450, BYK-3451, BYK-3455, BYK-3456, BYK-3 480, BYK-3481, BYK-3499, BYK-3550, BYK-3560, BYK-3565, BYK-3566, BYK-3750, BYK-3751, BYK-3752, BYK-3753, BYK-3754, BYK-3760, BYK -3761, BYK-3762, BYK-3763, BYK-3764, BYK-3770, BYK-3771, BYK-3780, BYK-3900P, BYK3902P, BYK-3931P, BYK3932P, BYK-3933P, BYK-8020 , BYK-8070, BYK-9890, BYK-DYNWET800, BYK-S706, BYK-S732, BYK-S740, BYK-S750N, BYK-S760, BYK-S780, BYK-S782, BYK-SILCELAN3700, B YK-SILCLEAN3701, BYK-SILCLEAN3710, BYK-SILCLEAN3720, BYK-UV3500, BYK-UV3505, BYK-UV3510, BYK-UV3530, BYK-UV3535, BYK-UV3570,BYK-UV3575, BYK-UV3576; DISPERBYK (hereinafter "BYK") surfactants selected from the BYKETOL series, such as BYKETOL-AQ, BYKETOL-OK, BYKETOL-PC, BYKETOL-SPECIAL, BYKETOL-WA, and the NANOBYK series, such as NANOBYK-3603, NANOBYK-3605, NANOBYK-3620, NANOBYK-3650, NANOBYK-3652, and NANOBYK-3822.

[0103] The wetting and dispersing agents used in the present invention are additives that provide both wetting and / or stabilizing effects to formulations containing fine solid particles. They provide a fine and uniform distribution of solid particles in the formulation medium, preferably a liquid formulation medium, ensuring the long-term stability of such systems. The formulation medium may include water and any organic solvent of various polarities. Furthermore, they provide improved wetting of solids and prevent particle aggregation by various mechanisms (e.g., electrostatic effects, steric effects, etc.).

[0104] Preferably, the wetting and dispersing agent is an organic polymer or copolymer having polar functional groups selected from amino groups, amide groups, carbamate groups, carbonate groups, acidic groups (preferably boric acid groups, boronic acid groups, carboxylic acid groups, sulfate groups, sulfonic acid groups, phosphoric acid groups, phosphonic acid groups, and phosphinic acid groups), ester groups (preferably boric acid ester groups, boronate ester groups, carboxylic acid ester groups, sulfate ester groups, sulfonic acid ester groups, phosphoric acid ester groups, phosphonic acid ester groups, and phosphinic acid ester groups), ether groups, hydroxy groups, keto groups, and urea groups. The organic polymer or copolymer may be present as a complex, derivative, and / or salt, preferably as a salt. Preferred salts are ammonium salts, alkylammonium salts, alkylolammonium salts, or alkali metal salts, such as Li, Na, K, and Rb salts. The polar functional groups may also be referred to as pigment- or filler-affinity groups. In a preferred embodiment, the wetting and dispersing agent is used as a solution.

[0105] More preferably, the wetting and dispersing agent is an organic polymer or copolymer selected from acrylates, amides, carboxylic acids, and esters, and the organic polymer or copolymer may be present as a complex, derivative, and / or salt, preferably as a salt, which may be further functionalized with one or more polar functional groups as described above. Preferred salts are ammonium salts, alkylammonium salts, alkylolammonium salts, or alkali metal salts, preferably Li, Na, K, and Rb salts. In a preferred embodiment, the wetting and dispersing agent is used as a solution.

[0106] The wetting and dispersing agent may be present in a mixture, preferably with a polysiloxane copolymer.

[0107] Preferred wetting and dispersing agents are commercially available from BYK-Chemie GmbH (Wesel, Germany). Suitable wetting and dispersing agents include ANTI-TERRA-202, ANTI-TERRA-203, ANTI-TERRA-204, ANTI-TERRA-205, ANTI-TERRA-210, ANTI-TERRA-250, ANTI-TERRA-U, ANTI-TERRA-U80, ANTI-TERRA-U100, BYK-151, BYK-153, BYK-154, BYK-155 / 35, BYK-156, BYK-220S, BYK-1160, BYK-1162, BYK-1165, BYK-9076, BYK- 9077, BYK-GO8702, BYK-GO8720, BYK-P104, BYK-P104S, BYK-P105, BYK-SYNERGIST2100, BYK-SYNERGIST2105, BYK-W900, BYK-W903, BYK-W907, BYK-W908, BYK-W909, BYK-W940, BYK-W961, BYK-W966, BYK-W969, BYK-W972, BYK-W974, BYK-W980, BYK-W985, BYK-W995, BYK-W996, BYK-W9010, BYK-W9011, BYK-W9012, BYKJET-9131, BYKJET-9132, BYKJET-9133, BYKJET-9142, BYKJET-9150, BYKJET-9151, BYKJET-9152, BYKJET-9170, BY KJET-9171, BYKUMEN, DISPERBYK, DISPERBYK-101N, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-107, DISPERBYK-108, DISPE RBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-115, DISPERBYK-118, DISPERBYK-130, DISPERBYK-140, DISPERBYK-142, DISPERBYK-1 45, DISPERBYK-161, DISPERBYK-162, DISPERBYK-162TF, DISPERBYK-163, DISPERBYK-163TF, DISPERBYK-164, DISPERBYK-165, DISPERBYK-166,DISPERBYK-167、DISPERBYK-167TF、DISPERBYK-168、DISPERBYK-168TF、DISPERBYK-169、DISPERBYK-170、DISPERBYK-171、DISPERBYK-174、DISPERBYK-180、DISPERBYK-181、DISPERBYK-182、DISPERBYK-184、DISPERBYK-185、DISPERBYK-187、DISPERBYK-190、DISPERBYK-190BF、DISPERBYK-191、DISPERBYK-192、DISPERBYK-193、DISPERBYK-194N、DISPERBYK-199、DISPERBYK-199BF、DISPERBYK-2000、DISPERBYK-2001、DISPERBYK-2008、DISPERBYK-2009、DISPERBYK-2010、DISPERBYK-2012、DISPERBYK-2013、DISPERBYK-2014、DISPERBYK-2015、DISPERBYK-2015BF、DISPERBYK-2018、DISPERBYK-2019、DISPERBYK-2022、DISPERBYK-2023、DISPERBYK-2025、DISPERBYK-2026、DISPERBYK-2030、DISPERBYK-2050、DISPERBYK-2055、DISPERBYK-2059、DISPERBYK-2060、DISPERBYK-2061、DISPERBYK-2062、DISPERBYK-2070、DISPERBYK-2080、DISPERBYK-2081、DISPERBYK-2096、DISPERBYK-2117、DISPERBYK-2118、DISPERBYK-2150、DISPERBYK-2151、DISPERBYK-2152、DISPERBYK-2155、DISPERBYK-2155TF、DISPERBYK-2157、DISPERBYK-2158、DISPERBYK-2159、DISPERBYK-2163、DISPERBYK-2163TF、DISPERBYK-2164、DISPERBYK-2190、DISPERBYK-2200、DISPERBYK-2205、DISPERBYK-2290、DISPERBYK-2291、DISPERPLAST-1142, DISPERPLAST-1148, DISPERPLAST-1150, DISPERPLAST-1180, DISPERPLAST-I, and DISPERPLAST-P.

[0108] Preferred adhesion promoters are block copolymers, preferably high molecular weight block copolymers; copolymers having functional groups, preferably hydroxy-functional copolymers having acidic groups, styrene-ethylene / butylene-styrene block copolymers (SEBS) functionalized with maleic anhydride, carboxylated SEBS functionalized with maleic anhydride, SEBS functionalized with glycidyl methacrylate, polyolefin block copolymers functionalized with maleic anhydride, and ethylene octene copolymers functionalized with maleic anhydride; and polymers having functional groups, preferably polymers having acidic groups, and polypropylene functionalized with maleic anhydride. In a preferred embodiment, the adhesion promoter is used as a solution.

[0109] Preferred adhesion promoters are commercially available from BYK-Chemie GmbH (Wesel, Germany). Preferred adhesion promoters are BYK-4500, BYK-4509, BYK-4510, BYK-4511, BYK-4512, BYK-4513, SCONA TPKD8102PCC, SCONA TSIN4013GC, SCONA TSPOE1002GBLL, SCONA TPPP2112FA, SCONA TPPP2112GA, SCONA TPPP8112GA, SCONA TSKD9103, SCONA TPPP8112FA, SCONA TPKD8304PCC, and SCONA TSPP10213GB.

[0110] Preferred polymer matrices are polymethyl methacrylate, polyvinylpyrrolidone, polycarbonate, polystyrene, polymethylpentene, and silicone.

[0111] In some embodiments, one or more formulation media are solution media and / or dispersion media. In preferred embodiments, one or more formulation media are selected from water, amides, aromatic hydrocarbons, non-aromatic hydrocarbons, alcohols, carboxylic acids, esters, ethers, ketones, diketones, lactones, and mixtures thereof. In particularly preferred embodiments, one formulation medium is water. In even more particularly preferred embodiments, the formulation medium is water.

[0112] The total content of the complexes in the formulation is preferably in the range of 0.1 to 25 wt. %, preferably 0.5 to 20 wt. %, and more preferably 1 to 12 wt. %, based on the total weight of the formulation. The total content of the complexes in the formulation may include one, two, three, four, five, or more different complexes. For example, the total content of the complexes in the formulation may include a first complex of formula (I) and a second complex of formula (I), where the first complex of formula (I) and the second complex of formula (I) are not the same complex. The first complex of formula (I) and the second complex of formula (I) may be present in equal amounts. The mass ratio (w / w) between the first complex of formula (I) and the second complex of formula (I) may be in the range of 1:100 to 100:1, preferably 1:10 to 10:1, and more preferably 1:5 to 5:1.

[0113] In a preferred embodiment of the invention, the formulation is an ink formulation suitable for inkjet printing. Typical requirements for an ink formulation are a surface tension in the range of 20 mN / m to 30 mN / m, and a viscosity in the range of 5 mPa·s to 10 mPa·s.

[0114] Manufacturing method According to a second aspect, there is provided a method of producing a formulation comprising a complex as described herein above, the method comprising: a) providing an aqueous solution comprising the complex described herein above, wherein the complex is present in an amount ranging from 0.1 to 10% by weight based on the total amount of the aqueous solution; b) Q l X p [In the formula, X is a halide, such as F, Cl, Br, I, preferably Cl; Q is an ammonium cation, an alkali metal cation, or an alkaline earth metal cation, preferably Q is Na or K; l is any number in the range of 1 to 20, preferably 1 to 10; p is any number ranging from 1 to 20, preferably from 1 to 10, optionally to a final salt concentration of about 1 M to reversibly precipitate the complex; c) centrifuging to obtain the precipitated complex as a pellet; d) adding water to the pellets; Optionally, e) repeating steps b), c), and d) one or more times to obtain a slurry; f) filtering; g) repeating steps b), c), and d) to obtain a slurry; h) subjecting the slurry obtained in step g) to dialysis to obtain a concentrated solution of the complex, wherein the complex is present in the range of 0.1 to 5% by weight, preferably 0.5 to 2.5% by weight, based on the total weight of the formulation.

[0115] In some embodiments, the method further comprises step h) of further concentrating the solution obtained or obtainable in step g) using a gentle stream of compressed air.

[0116] In some embodiments, the solution obtained or obtainable in step g) is centrifuged to form a lower layer and an upper layer, wherein the lower layer is redissolved using one or more formulation media to obtain a final concentration of the complex in the range of 2.5 to 25% by weight, preferably 5 to 20% by weight, based on the total weight of the formulation.

[0117] According to an alternative second aspect, there is provided a method of producing a formulation comprising a complex as described hereinabove, the method comprising: a) providing an aqueous solution comprising the complex described herein above, wherein the complex is present in an amount ranging from 0.1 to 10% by weight based on the total amount of the aqueous solution; b) adding an anti-solvent, such as DMSO, DMF, acetone, isopropanol, methanol, preferably methanol; c) centrifuging (and / or filtering) to obtain the precipitated complex as a pellet; d) adding water to the pellets; e) optionally repeating steps b), c), and d) one or more times to obtain a purer slurry. Advantageously, the use of an anti-solvent, especially methanol, allows for more efficient purification by reducing the number of steps required. In addition, methanol can be easily removed, for example, under reduced pressure. Preferably, the dialysis step can be omitted.

[0118] And it is believed that a good anti-solvent selected, such as DMSO, DMF, acetone, isopropanol, methanol, preferably the above-mentioned methanol, will precipitate the product but not the residual precursors and by-products, and the anti-solvent will be easily removed, for example, by evaporation.

[0119] Method for preparing optical metal oxide layers In a third aspect, there is provided a method for preparing an optical metal oxide layer, the method comprising the following steps (a) to (c): (a) (i) providing a formulation comprising: a complex comprising a polyoxometalate of formula (Ia) and nanoparticles of formula (Ib); and one or more formulation vehicles; (b) applying the formulation to the surface of the substrate; (c) converting the formulation into an optical metal oxide layer on the surface of the substrate.

[0120] In a preferred embodiment of the present invention, the formulation provided in step (a) of the method for preparing an optical metal oxide layer is an ink formulation suitable for inkjet printing. Typical requirements for an ink formulation are a surface tension in the range of 20 mN / m to 30 mN / m and a viscosity in the range of 5 mPa·s to 10 mPa·s.

[0121] In a preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, the formulation is applied to the surface of the substrate in step (b) by a deposition method. Preferred deposition methods are drop casting, coating, or printing. More preferred coating methods are spin coating, spray coating, slit coating, or slot die coating. More preferred printing methods are flexographic printing, gravure printing, inkjet printing, EHD printing, offset printing, or screen printing. Most preferred are spray coating and inkjet printing.

[0122] Depending on the specific problem to be solved, the formulation needs to be deposited as a homogeneous, dense thin layer covering the entire surface of the substrate by a coating method, or the formulation needs to be deposited locally in a structured manner, hence the need for a printing method. Both coating and printing methods require the formulation to be formulated in an appropriate manner to suit the physicochemical needs of the respective coating and printing method, as well as the specific needs regarding the surface of the substrate to be coated or printed.

[0123] For example, depending on the solids content and trench volume, step (b) may be performed one or more times, for example, two, three, four, five, six, etc. times.

[0124] In a preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, the surface of the substrate is pretreated by a surface cleaning process. Preferred surface cleaning processes are those described in W. Kern, "The Evolution of Silicon Wafer Cleaning Technology," J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892, and "New Process Technologies for Microelectronics," RCA Review 1970, 31, 2, 185-454. Such silicon wafer cleaning processes include wet cleaning processes using cleaning solvents (e.g., isopropanol (IPA)); wet etching processes using hydrogen peroxide solutions (e.g., piranha solution, SC1, and SC2), choline solutions, or HF solutions; dry etching processes using chemical vapor etching, UV / ozone treatment, or glow discharge techniques (e.g., O2 plasma etching); and mechanical processes using brush scrubbing, fluid jets, or ultrasonic techniques (sonification). The surface of the substrate can also be pretreated by silanization or atomic layer deposition (ALD) processes. Pretreatment of the substrate surface helps to modify the hydrophobicity / hydrophilicity of the surface, which can improve the adhesion and packing properties of the photometal oxide layer on the substrate surface.

[0125] In more preferred embodiments, a wet cleaning process involving a cleaning solvent (e.g., isopropanol (IPA)) is combined with one or more of the following: a wet etching process involving a hydrogen peroxide solution (e.g., piranha solution, SC1, and SC2), a choline solution, or an HF solution; a dry etching process involving chemical vapor etching, UV / ozone treatment, or glow discharge techniques (e.g., O2 plasma etching); and a mechanical process involving brush scrubbing, a fluid jet, or ultrasonic techniques (sonification).

[0126] In the most preferred embodiment, a wet cleaning process involving a cleaning solvent (e.g., isopropanol (IPA)) is combined with a mechanical process involving brush scrubbing, fluid jets, or ultrasonic techniques (sonification), and a wet etching process involving a hydrogen peroxide solution (e.g., piranha solution, SC1, and SC2), a choline solution, or an HF solution. In a preferred embodiment of the present invention, step (b) of the method for preparing an optical metal oxide layer is carried out several times in succession, preferably 2 to 20 times, more preferably 2 to 10 times, most preferably 2, 3, 4 or 5 times.

[0127] In a preferred embodiment of the method for preparing an optical metal oxide layer according to the invention, the formulation is converted in step (c) into an optical metal oxide layer on the surface of the substrate by exposure to a heat treatment and / or an irradiation treatment.

[0128] A preferred heat treatment involves exposure to elevated temperatures of up to 1200°C, preferably up to 600°C, more preferably up to 550°C, and most preferably up to 500°C. The heat treatment is not limited to any particular heat treatment method or time. Depending on the type of substrate and formulation, one skilled in the art can determine the appropriate heat treatment method and time.

[0129] Preferred irradiation treatments include exposure to infrared (IR) light, visible (Vis) light, and / or ultraviolet (UV) light. IR light has a wavelength of more than 800 nm. Vis light has a wavelength of 400 to 800 nm. UV light has a wavelength of less than 400 nm and may include EUV (extreme UV). The irradiation treatment is not limited to any particular irradiation treatment method or time. Those skilled in the art can determine the appropriate irradiation treatment method and time depending on the type of substrate and formulation.

[0130] In a more preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, the formulation is converted into an optical metal oxide layer on the surface of the substrate in step (c) by pre-firing (soft firing) at a temperature of 40-150°C, preferably 50-120°C, more preferably 60-100°C, and then firing (hard firing, sintering or annealing) at a temperature of 150-600°C, preferably 250-550°C, more preferably 300-500°C.

[0131] The soft bake (also called pre-bake) serves the purpose of removing volatile and low-boiling components, such as volatile and low-boiling formulation vehicles or additives, from the drop-cast, coated, or printed film. The soft bake is preferably carried out for 1 to 10 minutes. After the soft bake, a substrate-adherent film layer of metal oxide precursor or metal oxide precursor mixture is obtained. The film may further contain residual formulation vehicles or additives.

[0132] In an alternative more preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, the soft firing can be omitted, so that the formulation is directly converted into an optical metal oxide layer on the surface of the substrate in step (c) by firing (hard firing, sintering or annealing) at a temperature of 150-600°C, preferably 250-550°C, more preferably 300-500°C.

[0133] The calcination (hard calcination, sintering, or annealing) serves the purpose of converting the metal oxide precursor or metal oxide precursor mixture layer on the substrate into a metal oxide layer. The calcination process may also adjust the properties of the final metal oxide layer. The calcination is preferably carried out for 1 to 300 minutes, preferably 1 to 60 minutes, to achieve a refractive index (RI) of greater than 1.8.

[0134] The soft and hard bakes may be performed under ambient or increased oxygen content atmospheres to decompose undesired organic components, which may result in lower activation energies when the metal oxide layer is formed.

[0135] In a preferred embodiment of the method for preparing an optical metal oxide layer according to the present invention, the substrate is a patterned substrate comprising topographical features, and the metal oxide forms a coating layer that covers the surface of the substrate and fills the topographical features, so that the topographical features are filled and planarized by the metal oxide.

[0136] Preferred topographical features include, for example, gaps, grooves, surface relief gratings, trenches, and vias. The topographical features may be uniformly or non-uniformly distributed across the surface of the substrate. Preferably, they are arranged on the surface of the substrate as an array or grid. The topographical features preferably have different lengths, widths, diameters, and different aspect ratios. The topographical features preferably have an aspect ratio of 1:20 to 20:1, more preferably 1:10 to 10:1. The aspect ratio is defined as the width of the structure relative to its height (or depth). In terms of size, the depth of the topographical features is preferably in the range of 10 nm to 10 μm, more preferably 50 nm to 5 μm, and most preferably 100 nm to 1 μm.

[0137] It is also preferred that the topographical features are sloped at a particular angle, such as an angle of 10 to 80 degrees, preferably 20 to 60 degrees, more preferably 30 to 50 degrees, and most preferably about 40 degrees. Such sloped topographical features are also referred to as beveled or blazed topographical features.

[0138] It may be necessary to locally fill topographical features completely or to a certain level with an optical metal oxide layer, but not cover adjacent surfaces of the substrate where the topographical features to be filled are not available.

[0139] Therefore, the method for preparing an optical metal oxide layer according to the present invention comprises the following step (d): Preferably, the method further comprises (d) removing a portion of the optical metal oxide layer overlying a topographical feature, thereby obtaining a filled topographical feature, wherein the overburden of the optical metal oxide layer on top of the topographical feature is reduced to an overburden of preferably between 0 and 100 nm, more preferably between 0 and 50, and most preferably between 0 and 20 nm.

[0140] Step (d) is performed after steps (a) to (c) of the method according to the present invention. Preferably, removing the portion of the photometal oxide layer overlying the topography in step (d) is performed using a surface cleaning process as described above. Preferred surface cleaning processes are those described in W. Kern, *The Evolution of Silicon Wafer Cleaning Technology*, J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892, and *New Process Technologies for Microelectronics*, RCA Review 1970, 31, 2, 185-454. Such silicon wafer cleaning processes include wet etching processes using hydrogen peroxide solutions (e.g., piranha solution, SC1, and SC2), choline solutions, or HF solutions; dry etching processes using chemical vapor etching, UV / ozone treatment, or glow discharge techniques (e.g., O2 plasma etching); and mechanical processes using brush scrubbing, fluid jets, or ultrasonic techniques.

[0141] The substrate is preferably a substrate for an optical device. Preferred substrates are made of inorganic or organic-based materials, preferably inorganic-based materials. Preferred inorganic-based materials include materials selected from the list consisting of ceramic, glass, fused silica, sapphire, silicon, silicon nitride, quartz, and transparent polymers or resins. The shape of the substrate is not particularly limited, but is preferably a sheet or wafer.

[0142] In step (b) of the method for preparing an optical metal oxide layer, the formulation is applied onto the surface of a substrate, which may be either the surface of the base material of the substrate or the surface of a layer of a material different from the base material of the substrate, such layer being formed prior to applying the formulation.

[0143] In this way, a sequence of different layers (layer stacks) can be formed on top of one another. Such layer stacks may be structured, and such structures typically have nanometer-scale dimensions, at least in terms of diameter, width and / or aspect ratio.

[0144] Use of the formulation In a fourth aspect, the present invention relates to the use of a formulation for preparing an optical metal oxide layer, said formulation comprising: (i) a polyoxometallate moiety represented by formula (Ia), and ([Q l ] n+ [X z Y p O y ] n- (Ia) Nanoparticles represented by formula (Ib), M i M' j M'' f O k (Ib) [In the formula, each Q independently represents a cation, preferably the cation is selected from the group consisting of ammonium cation, alkali metal cation, alkaline earth metal cation; l is any number in the range of 1 to 20, preferably 1 to 10; n is the total positive charge n+ of l cations Q and polyanion [X z Y p O y ] is a number representing the corresponding negative charge n-; X is a heteroatom such as B, Si, Ge, P, Al, As, or Sb; Y is a metal, preferably a transition metal; z is 0 to 20; p is 1 to 100; y is 2 to 400; M, M', and M'' are each independently a metal; i, j, and f are each independently an integer or fractional number from 0 to 10, with the proviso that at least one of l, j, and f is not 0; k is any number ranging from 1 to 20, preferably from 1 to 5; (ii) one or more formulation vehicles.

[0145] Optical Devices In a fifth aspect, there is provided an optical device comprising an optical metal oxide layer obtainable or obtained by the method for preparing an optical metal oxide layer according to the present invention as described above, preferably an augmented reality (AR) and / or virtual reality (VR) device.

[0146] Preferred Embodiments Embodiment 1. A formulation for preparing an optical metal oxide layer, the formulation comprising: (i) a polyoxometallate moiety represented by formula (Ia), and (Q l ) n+ [X z Y p O y ] n- (Ia) Nanoparticles represented by formula (Ib), M i M' j M'' f O k (Ib) [In the formula, each Q independently represents a cation, preferably the cation is selected from the group consisting of ammonium cations, alkali metal cations, and alkaline earth metal cations; l is any number in the range of 1 to 20, preferably 1 to 10; n is the total positive charge n+ of l cations Q and polyanion [X z Y p O y] is a number representing the corresponding negative charge n-; X is a heteroatom, preferably B, Si, Ge, P, Al, As, or Sb, etc. Y is a metal, preferably a transition metal; z is 0 to 20; p is 1 to 100; y is 2 to 400; M, M', and M'' are each independently a metal; i, j, and f are each independently an integer or fractional number from 0 to 10, with the proviso that at least one of l, j, and f is not 0; k is any number ranging from 1 to 20, preferably from 1 to 5; (ii) one or more formulation vehicles.

[0147] Embodiment 2. The complex is Na7[PW complexed to TiO2 11 O 39 ], Na3[PMo complexed with TiO2 12 O 40 ], K6[P2W complexed with TiO2 18 O 62 ], K6[P2Mo complexed with TiO2 18 O 62 ], or Q complexed to TiO2 l [SiW 11 O 39 ], preferably the complex is Na7[PW complexed to TiO2 11 O 39 2. The complex of embodiment 1, wherein the complex is not:

[0148] Embodiment 3. However, when formula Ib is TiO2, formula Ia is Na7[PW 11 O 39 ], Na3[PMo 12 O 40 ], K6[P2Mo 18 O 62 ], K6[P2W 18 O 62 ] or Q l [SiW 11 O 39 ], and preferably formula Ia is Na7[PW 11 O39 ]. The formulation of embodiment 1, wherein

[0149] Embodiment 4. The complex has the formula (I): ([Q l ] n+ [POM] n- ) m (NP) r (I) [In the formula, POM is a polyoxometalate represented by formula (Ia); NPs are metal oxide or mixed metal oxide nanoparticles represented by formula (Ib); m represents the number of polyoxometalate ligands per nanoparticle and is any number ranging from 1 to 5000; 4. The formulation of any one of embodiments 1 to 3, wherein r is any number ranging from 1 to 20,000 and represents the empirical metal oxide units in the nanoparticles.

[0150] Embodiment 5. The formulation of any one of embodiments 1-4, wherein M, M', and M'' are each independently Ba, Sr, Ti, Zr, Nb, Hf, Ta, Zn, Al, In, Sn, or Ce, preferably Ba(II), Sr(II), Ti(III), Ti(IV), Zr(IV), Nb(V), Nb(III), Hf(IV), Ta(V), Zn(II), Al(III), In(III), Sn(II), Sn(IV), or Ce(IV).

[0151] Embodiment 6. The formulation of any one of embodiments 1-5, wherein M' is Ti and / or M is Sn.

[0152] Embodiment 7. The formulation of any one of embodiments 1 to 6, wherein i is <1, j is 1-i, and f is 0.

[0153] Embodiment 8. A formulation according to any one of embodiments 1 to 6, wherein the nanoparticles are SnO2, CeO2, ZrO2, TiO2, NbO2, HfO2, or Ta2O5, preferably the nanoparticles are SnO2 or TiO2.

[0154] Embodiment 9. The nanoparticles are mixed nanoparticles, for example Sn 0.5 Ti 0.5 O2, Sn 0.25 Ti 0.75 O2, Sn 0.54 Ti 0.46 O2 or Sn 0.13 Ti 0.87 8. The formulation of any one of embodiments 1-7, wherein the compound is O2.

[0155] Embodiment 10. A formulation according to any one of embodiments 1 to 9, wherein X is P, Ar, Sb, S, Si, Ge, B, Be, Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, or absent, preferably X is P, Si, Al, or absent.

[0156] Embodiment 11. A formulation according to any one of embodiments 1 to 10, wherein Y is W, Nb, V, Ta, Ti, Zr, Hf, Mo, Zn, In, or Sn, preferably Y is W or Nb.

[0157] Embodiment 12. The polyoxometalate moiety is a heteropolyoxotungstate or polyoxoniobate, preferably the polyoxometalate moiety is Na7[PW 11 O 39 ] or K8[Nb6O 19 12. The formulation of any one of embodiments 1 to 11, wherein:

[0158] Embodiment 13. The formulation of any one of embodiments 1-12, wherein the formulation comprises (iii) one or more additives.

[0159] Embodiment 14. The one or more additives are each individually a further complex according to any one of embodiments 1 to 12, Na3PW 12 O 40 * nH2O, K8NbO 19 *14. The formulation of any one of embodiments 1-13, wherein the additive is selected from the group consisting of nH2O, wetting agents, dispersing agents, adhesion promoters, polymer matrices, and surfactants.

[0160] Embodiment 15. Na3PW 12 O 40 * nH2O or K8Nb6O 19 * 15. The formulation of any one of embodiments 1-14, further comprising nH2O, and optionally a surfactant such as a polyether-modified siloxane.

[0161] Embodiment 16. Further complexes include Na7[PW 11 O 39 ]-TiO2.

[0162] Embodiment 17. A formulation according to any one of embodiments 1 to 16, wherein the formulation medium is water.

[0163] Embodiment 18. Use of a formulation according to any one of embodiments 1 to 16 for preparing an optical metal oxide layer.

[0164] Embodiment 19. A method for preparing an optical metal oxide layer, comprising the steps of: (a) providing a formulation according to any one of embodiments 1 to 17; (b) applying the formulation to the surface of the substrate; (c) converting the formulation into an optical metal oxide layer on the surface of the substrate.

[0165] Embodiment 20. An optical device, preferably an augmented reality and / or virtual reality device, comprising an optical metal oxide layer, the layer being obtained by the method of embodiment 19.

[0166] The present invention is further illustrated by, but not limited to, the following examples. Those skilled in the art will recognize that various modifications, additions, and variations can be made to the present invention without departing from the spirit and scope of the invention, as defined in the appended claims. [Example]

[0167] List of Abbreviations NP nanoparticles POM Polyoxymetallate ·Conc. Concentration Cald. Calculated RI refractive index n

[0168] Materials and Methods material: ·K7[PW 11 O 39 ] * nH2O was prepared according to a known procedure (Haraguchi et al., Inorg. Chem. 2002, 33(6):1015-1020). K8[Nb6O 19 ] * nH2O was prepared according to a known procedure (Kong, X., Hu, D., Wen, P., Ishii, T., Tanaka, Y., & Feng, Q. (2013). Dalton Transactions, 42(21), 7699-7709. DOI: 10.1039 / C3DT00062A.). ·Na3[PW 12 O 40 ] * nH2O was prepared according to a known procedure (Phillips, MA (1950), The preparation of phosphotungstic acid and of sodium and barium phosphotungstates. J. Chem. Technol. Biotechnol., 69:282-284. https: / / doi.org / 10.1002 / jctb.5000690906). A 25 wt% BYK348 aqueous solution was prepared by adding 0.375 g (0.375 mL) of ultrapure water (Milli-Q) to 0.125 g (0.118 mL) of BYK348. BYK348 was purchased from BYK-Chemie GmbH. ·10wt%Na3PW 12 O 40 * The nH2O aqueous solution (PW-A) was prepared by dissolving 4.5g of water in 0.5g of Na3PW 12 O 40 * It was prepared by adding to nH2O. ·10wt%K8Nb6O 19 * A 10 wt% nH2O aqueous solution (NbO-A) was prepared by dissolving 4.5 g of water in 0.5 g of K8Nb6O 19 * It was prepared by adding to nH2O. Cellulose dialysis membranes (Spectra / Por 1 Dialysis Membrane MWCO: 6-8,000, nominal flat width 40 mm) were pretreated before use according to the manufacturer's instructions.

[0169] General methods of detection and characterization 1) Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) Data were acquired using a SPECTRO ARCOS FHM22 instrument (AMETEK®) equipped with a vertical plasma torch box (SOP) and analyzed using Smart Analyzer Vision software. Samples were diluted to fit the instrument's concentration range and measured without further processing.

[0170] 2) Ellipsometry Ellipsometry was used to determine the layer thickness, refractive index (n), and absorptivity (k) of the metal oxide layer. Measurements were performed using a J.A. Woollam alpha SE ellipsometer at three different angles of incidence (65°, 70°, and 75°). The measurement data was analyzed using J.A. Woollam CompleteEase software, which applied Cauchy fitting to obtain the refractive index (n) and absorptivity (k), assuming either complete or near-complete transparency above a wavelength of 600 nm. Optical constants were averaged from three different points measured on either the soft-baked or hard-baked samples.

[0171] Film preparation: For ellipsometry measurements, materials were deposited onto Si substrates (untreated or piranha-treated) by spin-coating from aqueous solutions at 2000 RPM for 25 seconds, soft-baked at 100 °C for 1 minute, and then hard-baked at 300 °C for 10 minutes.

[0172] Film thicknesses typically ranged from 35 to 300 nm.

[0173] Scanning electron microscope (SEM) SEM images were recorded using either a HR-SEM Sirion or an Extra-High Resolution Scanning Electron Microscope Magellan 400L (ThermoFisher, formerly FEI).

[0174] 3) Calculation of the estimated diameter of POM-NPs Figure 15A is a schematic diagram of an NP (100) with radius R (106) complexed to m POMs (m = 9). Several projections (104) of the POMs onto the NP sphere are also shown. In Figure 15B, the same projections are shown where the NP radius is much larger than the POM radius, and the NP is shown as a plane to illustrate the packing of the POM spheres.

[0175] The following calculations provide an estimate of the nanoparticle (core) effective radius using the following notation and assumptions: [Table 1] a For the mixed oxide cores, a weighted average of the molecular weights was used.

[0176] b For NP, this includes: SnO2 (cassellite) only, ρ is 6.95g / cm 3 It was thought that (e.g., Example 1, Example 2); TiO2 (anatase) only, ρ is 3.78g / cm 3 It was thought that (e.g., Example 9a, Example 9b); TiO2 (amorphous) only, ρ is 3.00 g / cm 3 It was thought that (e.g., Example 6, Example 7); Mixed Sn / TiO2NP, ρ average value 4.23 g / cm 3 was assumed (for example, Example 3, Example 4, Example 5, Example 8).

[0177] c POM effective radius r POM , were used based on values ​​obtained from Weinstock et al. J. Am. Chem. Soc. 2009, 131, 47, 17412-17422; and Nyman et al., J Clust Sci, 2006, 17:197-219.

[0178] The following assumptions are made: 1. The core (NP) is spherical. 2. The number of POMs covering the NP is less than the number of "core formula units" (e.g., TiO2). 3. The curvature of the core NP is not considered in the geometric modeling 4. All metal atoms are in the form of metal oxides and are part of the NP core 5. All POM transition metal atoms are in the form of POM and attached to the surface of the NPs First, the mass of the NP is calculated using equation (i), assuming a spherical structure with radius R and density ρ of the associated crystal structure.

number

[0179] The number of core formula units, r, is then calculated by dividing the mass by the molecular weight, MW, using equation (ii).

number

[0180] The core radius is larger than the POM radius (R>r POM ), assuming that the curvature of the NP is ignored, we derive the formula for the NP radius below.

[0181] The number of NPs in 1 liter is calculated by dividing the concentration [M] of the metal element (e.g., Ti) by the number r of elements in a single core.

[0182] The number of NPs in 1 liter is given by [M] / r.

[0183] The number of POMs per liter is given by equation (iii). (iii) [POM] = m × [M] / r Equation (iii) can be used to calculate m by inserting (i) and (ii).

number

[0184] The surface area of ​​the NP is A = 4πr 2 and the area of ​​the projection of a single POM on the core is given by,

number

[0185] The total area of ​​the projection of the POMs on the surface of the NP is calculated by multiplying the area of ​​the POMs by the number of POMs per NP, as shown in equation (iv).

number

[0186] The total projected surface area of ​​the core is also given by multiplying the surface area of ​​the core by the packing factor, which describes the coverage efficiency of a collection of closed packs of circles on a given area. Surface of NP × (filling ratio) = (sum of projections of POM on NP) and using the formula above:

number

[0187] Finally, R is given by the following formula:

number

[0188] The size of the nanoparticles is not uniform in this synthesis and may vary depending on the exact composition and synthesis method. Therefore, this calculation assumes that average parameters, including the radius of the NPs, are considered. In addition, various approximations are made as described above, and there is experimental error in measuring the values ​​of [POM] and [M]. Therefore, the average radius is expected to be within ±30% of the calculated value, and a wider variance in the distribution can be expected.

[0189] General method of preparation 1) Surface pretreatment and compound deposition To prepare the piranha-treated substrates, the substrates were immersed in a 3:1 mixture of concentrated HSO and 30% HO for 20 min, then washed with distilled water (at least 9 times) until the pH of the wash water was neutral. The substrates were dried using an air gun.

[0190] Coating of wafers (square Si / SiO2, AF45 glass, or 18 x 18 mm Si / SiN structured substrates) was performed using an Ossila spin coater. The spin coating process using flat substrates was as follows: 0.1 mL of coating was deposited onto the wafer, followed by spinning at 2000 rpm for 25 seconds. The coating procedure for structured substrates was as follows: 0.1 mL of coating was deposited onto the wafer, with a holding time of 1 minute, followed by spinning at 2000 rpm for 25 seconds. After spin coating, the coated substrates underwent a soft bake at 100°C for 1 minute to drive off solvent residues, followed by high-temperature curing. Typically, but not exclusively, the coated layers were hard baked at 300°C, 400°C, and 500°C for 10 minutes. The soft bake and layer curing were performed using a high-temperature hotplate, which allowed temperatures up to 500°C to be reached.

[0191] 2) Substrate with trench structure The structured substrate, typically a silicon wafer, was used as a square die with an edge length of 1.5 cm to 2 cm. The wafer die was cut and cleaved from a parent wafer, typically with a diameter of 8 inches. The structure was then fabricated using SiO2 / SiN x The structures were fabricated and arranged in a layer stack consisting of: (1) a silicon nitride film (SiO 2 ) and (2) a silicon nitride film (SiO 3 ). The dimensions of the structures (e.g., trench cross-sectional width and length) were referenced to the Sematech Mask 854 architecture. Typically, but not exclusively, cross-sectional cleaves perpendicular to the trench arrays providing widths of 40 nm to 50 nm were used as the trench structures of primary interest to study their filling with metal oxides. In addition to the above, cross-sections of arrays of trenches with widths of 100 nm and 150 nm were used to study trench filling with metal oxides.

[0192] The structured wafer dies were coated by spin coating unless otherwise noted. To this end, a volume of typically 0.1 mL per die of the coating formulation was pipetted and cast onto the surface of the wafer. The wafer dies were spun at 2000 rpm for 25 seconds. The soft bake and hard bake conditions for the structured wafer dies were selected to be similar or identical to those previously described for the non-trench substrates.

[0193] Preparation of POM composite nanoparticles Example 1: [α-PW] complexed to SnO2 nanoparticles 11 O 39 ] 7- Preparation of SnCl4·5H2O (926 mg, 2.64 mmol) was added as a solid to deionized water (198 mL). The pH was adjusted to 4.5 by adding aqueous LiOH (160 mM, approximately 66 mL, 10.6 mmol), followed by K7[α-PW 11 O 39 Aqueous solution of [α-PW] (20 mM, 66 mL, 1.32 mmol) was added. The reaction mixture was stirred at 25 °C for 2 h, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated in an oven (120 °C, 24 h), and then cooled to room temperature on the bench. [α-PW] complexed to SnO nanoparticles was 11 O 39 ] 7- An optically clear solution containing

[0194] Isolation. Saturated NaCl solution was added to the cooled reaction mixture to a final salt concentration of 1 M, reversibly precipitating complex 1. The cloudy solution was centrifuged (6000 rpm, 5 min), after which the supernatant was discarded and the pellet redissolved in water. Two additional isolation cycles of salt addition, centrifugation, and pellet redissolution were performed. The solution was then filtered using a Millex-HV Syringe Filter Unit (0.45 μm, PVDF, 33 mm) to remove any large impurities. An additional isolation cycle was performed using a minimal amount of water to dissolve the pellet and release the [α-PW] complexed to SnO2 nanoparticles containing excess NaCl. 11 O 39] 7- A slurry containing the following was prepared.

[0195] Purification: The slurry was transferred to a treated cellulose membrane bag, which was then placed in a 1 L water bath for dialysis (16 h, with one water change after 1 h). [α-PW] complexed to SnO2 nanoparticles was then purified. 11 O 39 ] 7- A purified, fully dissolved, and concentrated (approximately 1% w / v) solution containing

[0196] Concentration: The dialyzed solution was further concentrated to a concentration of 8.5% (wt%) using a gentle stream of compressed air.

[0197] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0198] Example 2. [NbO] complexed to SnO nanoparticles 19 ] 8- Preparation of Solid SnCl 5HO (938 mg, 2.68 mmol) was added to deionized water (342 mL). The pH was adjusted to 10.5 by adding KOH (400 M, approximately 26.9 mL, 10.8 mmol), followed by KNbO 19 An aqueous solution (20 mM, 66 mL, 1.32 mmol) was added. The reaction mixture was stirred at 25 °C for 2 h, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated in an oven (120 °C, 24 h), and then cooled to room temperature on the bench. [NbO 19 ] 8- An optically clear solution containing

[0199] [NbO 19 ] 8- Isolation, purification, and concentration of was carried out as described above for complex 1, except that a saturated solution of KCl was used instead of NaCl and concentrated to a final concentration of 12 wt %.

[0200] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0201] Example 3. Sn 0.5 Ti 0.5 [NbO 19 ] 8- Preparation of SnCl4·5H2O (18.4 mg, 52.5 μmol) was added as a solid to deionized water (12.0 mL), followed by aqueous KOH (400 mM, 0.23 mL, 91 μmol). A freshly prepared solution of titanium isopropoxide diluted in isopropanol (40 mM, 4 mL, 160 μmol) was then added dropwise with vigorous stirring, resulting in a cloudy white suspension. The solution was stirred for 30 min, after which K8[Nb6O 19 An aqueous solution of Sn (20 mM, 4 mL, 80 μmol) was added. The reaction mixture was stirred for an additional 2 h at 25 °C, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated in an oven (120 °C, 20 h), and then cooled to room temperature on the bench. 0.54 Ti 0.46 [NbO 19 ] 8- A solution containing:

[0202] Isolation and purification was carried out as described above for Example 1, except that a saturated solution of KCl was used instead of NaCl.

[0203] The dialyzed solution was centrifuged (18,000 rcf, 1 hour) to separate Sn 0.54 Ti 0.46 [NbO 19 ] 8- moves to the bottom, and Sn 0.54 Ti 0.46 O2 complexed with [Nb6O 19 ] 8- The upper layer was discarded, and the lower layer was redissolved in a small amount of water to obtain a 15.1 wt. % Sn solution.0.54 Ti 0.46 [NbO 19 ] 8- to obtain a final concentration of .

[0204] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0205] Example 4. Sn 0.25 Ti 0.75 [NbO 19 ] 8- Preparation of A prepared amount of SnCl4·5H2O (9.3 mg, 26 μmol), deionized water (11.76 mL), aqueous KOH solution (400 mM, 0.26 mL, 104 μmol), and a certain amount of K8[Nb6O 19 ] (4 mL, 80 μmol) using the method described in Example 3. 0.25 Ti 0.75 [NbO 19 ] 8- was synthesized, isolated, purified and concentrated.

[0206] The product was concentrated to 9.2 wt % at pH 10.

[0207] A film was prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2. (Example 4a)

[0208] Another film was prepared under the heading "2) Ellipsometry," but was hard-baked at 200° C. instead of 300° C. The results of the ellipsometry measurements are shown in Table 2. (Example 4b)

[0209] Example 5. Sn 0.13 Ti 0.87 [NbO 19 ] 8- The adjusted amount of SnCl4·5H2O (7.2 mg, 20 μmol), deionized water (11.42 mL), KOH aqueous solution (400 mM, 0.58 mL, 230 μmol), and the same amount of K8[Nb6O 19 ] (4 mL, 80 μmol) using the method described in Example 3. 0.13 Ti 0.87 [NbO 19 ] 8- was synthesized, isolated, purified and concentrated.

[0210] Sn 0.13 Ti 0.87 O2 complexed with [Nb6O 19 ] 8- The solution containing was concentrated to a concentration of 17.7 wt %. The solution was then diluted 4 times to obtain a final concentration of 4.4 wt %.

[0211] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0212] Example 6. [NbO] complexed to TiO nanoparticles 19 ] 8- Preparation of Aqueous KOH (400 mM, 4.5 mL, 1.8 mmol) was added to deionized water (178.3 mL), followed by the dropwise addition of a freshly prepared solution of titanium isopropoxide (40 mM, 59.4 mL, 2.38 mmol) diluted in isopropanol under vigorous stirring, resulting in a slightly cloudy white suspension. 19 ] aqueous solution (20 mM, 59.4 mL, 1.19 mmol) was added. The reaction mixture was then refluxed (80 °C, 24 h) to obtain a solution containing complex 6. Isolation and purification were carried out in a manner similar to that described for Example 1, except that a saturated solution of KCl was used instead of NaCl. A concentrated solution of the product was obtained using the concentration method described in Example 3.

[0213] [NbO 19 ] 8-The final concentration of the solution containing was 18.6% by weight.

[0214] A film was prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2. (Example 6a).

[0215] [NbO 19 ] 8- (18.6% w / v) was diluted twice to a concentration of 9.8% w / v.

[0216] A film was prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2. (Example 6b).

[0217] Example 7. [NbO] complexed to TiO nanoparticles 19 ] 8- Preparation of The synthesis, isolation, purification, and concentration were carried out using the protocol described in Example 6, except that instead of refluxing, the reaction was heated hydrothermally. 19 After the addition of the ] solution, the reaction mixture was stirred at 25°C for 1 h, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated in an oven (180°C, 20 h), and then cooled to room temperature on the bench.

[0218] [NbO 19 ] 8- A solution containing (5.2% by weight) was obtained.

[0219] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0220] Example 8. Sn 0.13 Ti 0.87 [α-PW] complexed to O2 nanoparticles 11 O 39 ] 7- Preparation of Solid SnCl4·5H2O (103 mg, 0.294 mmol) was added to deionized water (293 mL). A freshly prepared solution of titanium isopropoxide in isopropanol (10% v / v, 9 mL, 3.1 mmol) was then added dropwise with vigorous stirring to give a cloudy white suspension. The pH was adjusted to 4.5 by adding aqueous KOH (0.4 M, approximately 3 mL, 1.2 mmol), followed by K7[α-PW 11 O 39 ] * SnH2O (3.71 g, 1.17 mmol) was added as a crystalline solid. The reaction mixture was stirred at 25 °C for 3 h, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated (120 °C, 17 h), and then cooled to room temperature on the bench. 0.13 Ti 0.87 [α-PW] complexed to O2 nanoparticles 11 O 39 ] 7- A solution containing:

[0221] Sample isolation and purification was performed as described in Example 1.

[0222] Concentration: The solution was concentrated to a final concentration of 9.4% by weight according to the method described in Example 3.

[0223] Sn 0.13 Ti 0.87 [PW] complexed to O2 nanoparticles 11 O 39 ] 7- The optical properties of were measured after soft baking at 100°C (8a) for 1 minute, and after subsequent heating periods (hard baking) at 300°C (8b), 400°C (8c), and 500°C (8d) for 10 minutes. The results of the ellipsometry measurements are shown in Table 2.

[0224] The optimum appears to be reached at 300° C., which has the highest RI.

[0225] The shrinkage between 100°C for 1 minute and 300°C is about 5%.

[0226] Example 9a-b. [α-PW] complexed to TiO2 nanoparticles 11 O 39 ] 7- Preparation of Example 9a A freshly prepared solution of 10% titanium isopropoxide in isopropanol (8.9 mL, 3.0 mmol) was added dropwise to 369 mL deionized water under vigorous stirring to give a cloudy white suspension. 11 O 39 ] * nHO (4.79 g, 1.51 mmol) was added as a crystalline solid. The reaction mixture was then stirred at 25 °C for 10 min, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated in an oven (170 °C, 20 h), and then cooled to room temperature on the bench. [α-PW] complexed to TiO NPs was obtained. 11 O 39 ] 7- An optically clear solution containing

[0227] [α-PW] complexed to TiO2 nanoparticles 11 O 39 ] 7- Isolation and purification was carried out as described in Example 1.

[0228] Concentration: A concentrated solution was obtained according to the method described in Example 3, with a yield of 10.7% by weight.

[0229] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0230] Example 9b A freshly prepared solution of titanium isopropoxide diluted in isopropanol (40 mM, 59.4 mL, 2.38 mmol) was added dropwise to deionized water (178 mL) under vigorous stirring to give a cloudy white suspension. 11 O 39An aqueous solution of [α-PW] (20 mM, 59.4 mL, 1.19 mmol) was added. The reaction mixture was then stirred at 25 °C for 1 h, transferred to a Teflon-lined 316 stainless steel reaction vessel, heated in an oven (180 °C, 20 h), and then cooled to room temperature on the bench. 11 O 39 ] 7- An optically clear solution containing

[0231] Isolation and purification of the solution was carried out as described in Example 1. Using the concentration method described in Example 3, a concentrated solution of 10.1 wt % was obtained.

[0232] The films were prepared as described in the section "2) Ellipsometry," and the results of the ellipsometry measurements are shown in Table 2.

[0233] [Table 2]

[0234] As can be seen from Table 2, among the complexes with varying Sn:Ti ratios, the complex obtained in Example 4 exhibited the highest refractive index, suggesting that the optimal Sn:Ti element ratio is 0.25-0.75. In addition, Example 8 shows that the optimum value appears to be achieved at 300°C. The shrinkage between 100°C for 1 minute and 300°C is approximately 5%.

[0235] The presence of both counterions "K" and "Na" in Examples 1, 8, and 9 can be easily explained by looking at the synthetic pathways. "K" refers to the precursor K7 [α-PW] used in the synthesis of the corresponding POM-NPs. 11 O 39 ] * It will be understood that this is the remaining residue from H2O.

[0236] [Table 3] The above examples show that the technical object of the present invention is achieved.

[0237] Alternative Solvent-Based Purification Methods Sn x Ti 1-x [NbO 19 ] 8- Synthetic protocol for the preparation of SnCl4 * HO (140 mg, 399 μmol) was added as a solid to deionized water (173 mL). KOH solution (1 M, 1.4 mL, 1.4 mmol) was added to the mixture to adjust the pH to 10.3. Freshly prepared titanium isopropoxide solution (40 mM, 730 μL, 2.49 mmol titanium isopropoxide, diluted with 61.52 mL isopropanol) and K[NbO] were added. 19 The addition of both aqueous solutions of Sn (1.686 g, 1.25 μmol, dissolved in 62.25 mL of water) was performed simultaneously (approximately 30 seconds) to the tin solution with vigorous stirring in a slow, steady stream. The reaction mixture was then stirred for approximately 3 hours, after which the mixture was transferred to a Teflon-lined 316 stainless steel reaction vessel and heated in an oven at 120 °C for 20 hours. The reaction vessel was then cooled to room temperature, and the Sn x Ti 1-x [NbO 19 ] 8- A solution containing:

[0238] Purification method by precipitation (Purification method 1) Purification method 2 involves precipitating the product from the reaction mixture by adding saturated KCl solution until a concentration of 1 M KCl is reached. Under these conditions, the nanocrystals reversibly aggregate and precipitate, while most of the molecular clusters remain in solution. The precipitate is separated from the supernatant by centrifugation and decantation, and can then be redissolved in water using the same volume of solvent as the reaction itself, or in a volume approximately one-sixth the reaction volume. The precipitation, centrifugation, and redissolution steps (one purification cycle) are repeated three times.

[0239] The resulting nanocrystal solution contains excess KCl, which limits the solubility of the product to approximately 1 wt %. To increase solubility, 18 hours of dialysis was performed to remove excess KCl and the K of the hexaniobate ligand. + Remove some of the counterions to leave 6-8 K per ligand + The remaining countercation is a proton (0-2H + ). This removal of KCl allows further concentration of the product to greater than 5 wt % by air evaporation of the aqueous solution.

[0240] Solvent-based purification method (purification method 2) in which a solvent is added to remove molecular by-products In a typical procedure, methanol is added to reach 10% by volume to obtain a mixed solvent system of methanol, isopropanol, and water, followed by centrifugation and redissolution in water or filtration (depending on the scale) of the pellet thus obtained.

[0241] result: The dissolved pellet and supernatant solutions obtained after two purification methods (Purification Method 1 and Purification Method 2) were compared after a single precipitation, isolation, and redissolution cycle using data from UV-Vis, FTIR, and ICP spectroscopy (Figures 7A-7B and 8, and Table 4). 1 .

[0242] Figures 7A and 7B show a comparison of the UV-Vis spectrum of a diluted sample of the supernatant solution (A) and the UV-Vis spectrum of a diluted sample of the lysis product obtained using purification methods 1 and 2 (B).

[0243] FIG. 8 shows the FT-IR spectra of dried samples of the products obtained using purification methods 1 and 2.

[0244] The resulting molar ratios between the elements of the isolated products obtained by ICP-OES measurements are shown in Table 4.

[0245] [Table 4]

[0246] "Combined method" (combined purification methods 1 and 2) After purification by Purification Method 1, the solution was precipitated once more using KCl, followed by centrifugation. The pellet thus obtained was dispersed in a 1:1 water-methanol mixture (1 / 5 of the original sample volume), centrifuged, and the pellet was redissolved in pure water.

[0247] Table 5 shows the molar ratios between the elements of the isolated products as determined by ICP-OES.

[0248] [Table 5]

[0249] The sample for the combined method was [NbO 19 ] 8- 0.6K per cluster + ions, while the standard method sample had an excess of [NbO 19 ] 8- 75K per cluster + It had an excess of ions.

[0250] The results in Tables 4 and 5 can be further optimized by repeating the purification cycle, adjusting the nature of the added solvent or the relative ratio of the solvent mixture, or lowering the pH to control the protonation state of the ligand in the product, which affects solubility and separation upon addition of organic solvent.

[0251] Additional solvent systems: Addition of additional solvents to the isopropanol-water mixture can also be considered. For example, Figure 9 shows the reaction mixture after adding 10% (v / v) of additional solvent (e.g., DMSO, DMF, acetone, methanol, acetonitrile, etc.) to create a mixed organic-aqueous solvent system.

[0252] Figure 10 shows the KNbO in a mixed solvent system of additive solvent, isopropanol, and water. 19A pure solution of

[0253] Preparation of formulations containing complexes of different sizes or with additional polyoxometalate ligands The purpose of the following experiments was to test whether adding smaller POM-NP complexes to larger POM-NP complexes would result in a coating with an increased refractive index.

[0254] General method: Vortex mix the material for 15 seconds at room temperature. If necessary, dilute the material with water by heating at 50°C for 10 minutes and using vortex mixing.

[0255] Example M1 An aqueous solution of "PW-SnO2" (8.5 wt%, Example 1) was mixed with an aqueous solution of "PW-TiO2" (10.7 wt%, Example 9a) in the amount shown in Table 4.

[0256] The results of the ellipsometry measurements are shown in Table 6.

[0257] [Table 6]

[0258] Table 6 shows that by mixing PW-TiO2 with PW-SnO2 in various ratios, higher refractive indices can be obtained compared to the pure PW-TiO2 or PW-SnO2 materials, respectively. Adding small amounts of PW-SnO2 to PW-TiO2 appears to be particularly beneficial in achieving higher refractive indices, with the highest refractive indices achieved by PW-TiO2 at 0.90-0.94 weight fractions.

[0259] FIG. 11 shows the refractive index dependence on the PW-TiO2 weight fraction for PW-TiO2 / PW-SnO2 mixtures.

[0260] Example M2 An aqueous solution of "PW-TiO2" (10.7 wt%, Example 9a) was mixed with an aqueous solution of "PW-A" (10 wt%) in the amount shown in Table 7.

[0261] The results of the ellipsometry measurements are shown in Table 7.

[0262] [Table 7]

[0263] Increasing the amount of PW leads to an increase in the refractive index up to 2.074 at a PW-A weight fraction of 0.31. Additional amounts of PW-A decrease the refractive index at a smaller gradient compared to increases at weight fractions <0.31.

[0264] A refractive index of 2.093 was achieved with a different batch of PW-TiO2 at a weight fraction of 0.35. The film thus prepared also had an extinction coefficient of 0.003.

[0265] The refractive index of the blends containing PW-TiO2 and PW-A is shown in Figure 12 as a function of PW-TiO2 wt% content measured on thin films deposited on Si substrates and hard-baked at 300 °C.

[0266] Example M3: An aqueous solution of "PW-SnO2" (8.5 wt%, Example 1) was mixed with an aqueous solution of "PW-TiO2" (10.7 wt%, Example 9a) to obtain a weight fraction of PW-TiO2 of 0.94 (see Table 3). In addition, an aqueous solution of PW-A (9.5 wt%) was added in the amount shown in Table 8.

[0267] [Table 8]

[0268] As can be seen from Table 8, the addition of PW-A to the PW-TiO2 / PW-SnO2 mixture increases the refractive index.

[0269] Figure 13 shows the refractive index of PW-TiO2 / PW-SnO2 mixtures and various amounts of PW-A added.

[0270] Example M4 "NbO-Sn 0.25 Ti 0.75 An aqueous solution of "O2" (9.2 wt %, Example 4) was mixed with the "NbO-A" solution (10 wt %) in the amount shown in the table. Films were prepared from the resulting formulations. The results of the ellipsometry measurements are shown in Table 9.

[0271] [Table 9] a Hard bake at 300°C. b Hard bake at 400°C.

[0272] For both the 300°C and 400°C firing temperatures, the NbO-Sn ratio was 1.8 / 1. 0.25 Ti 0.75 The weight percent ratio of O2 / NbO-A resulted in films with higher refractive indices: 1.997 at 300°C and 2.033 at 400°C.

[0273] The extinction parameter k is significantly higher at higher NbO-A POM contents.

[0274] Pure NbO-Sn 0.25 Ti 0.75 The film prepared from O2 had a thickness of 92 nm, an RI of 1.968, and k of 0.0031. The addition of NbO-A POM increased the RI.

[0275] Example M5 (mixing material 7 and material 15) An aqueous solution of "NbO-TiO2" (5.2 wt%, Example 7) was mixed with the "NbO-A" solution (10 wt%) in the amount shown in the table.

[0276] [Table 10]

[0277] The addition of POM increases the RI compared to the results obtained in Example 7 (RI = 1.880, k = 0.0009). As can be seen from Table 10, the highest RI was achieved at the weight percent ratio (NbO-TiO2 / NbO-A) with RI = 1.992.

[0278] Example M6 "PW-Sn 0.13 Ti 0.87 An aqueous solution of "O2" (9.4 wt%, Example 8) was mixed with the amount of "PW-A" solution (10 wt% PW-A in water) shown in Table 11.

[0279] [Table 11]

[0280] The extinction parameter k is not significantly higher at high NbO-A ligand contents as it is for particles with high SnO2 contents.

[0281] [Table 12] 1 TiO2 at a weight fraction of 0.94

[0282] The refractive index n and absorption parameter k shown in Table 12 were all measured after a soft bake at 100° C., followed by a hard bake at 300° C. This temperature was chosen because it is advantageous for device fabrication utilizing these formulations. However, higher refractive index values ​​n can be achieved when firing at higher temperatures, as seen in Examples M4.4, M4.5, and M4.6.

[0283] conclusion Selected results from Examples M1-M6 are summarized in Table 12. As can be seen, adding a small amount (6 wt%) of smaller POM-NPs to larger POM-NPs results in an unexpected increase in refractive index (Table 10, M1). The addition of POM ligands to POM-NPs is also beneficial in all tested Examples (Table 10, M2-6). Adding PW-A to a solution of PW-SnO2 / PW-TiO2 (6% PW-SnO2) further increases the refractive index to 2.04 and lowers k (Table 12: M3).

[0284] Trench filling experiment Example T1: PW-SnO2 The solution obtained in Example 1 was diluted in water to a concentration of 5 wt % PW-SnO2. The 5 wt % solution was used to deposit trench samples according to the procedure described above in "Substrates with Trench Structures."

[0285] Briefly, a solution containing PW-SnO2 (5 wt%, 0.1 mL) was deposited onto a piranha-treated Si substrate, followed by spinning at 2000 rpm for 25 seconds. The substrate was soft-baked at 100 °C for 1 minute and then hard-baked at 300 °C for 10 minutes. A cross-sectional SEM image is shown in Figure 14. As shown in Figure 14, large voids are formed within the trench. This may be the result of incomplete filling of the gap due to poor penetration and adhesion of POM-NPs to the trench surface during the heating step.

[0286] Example T2-A: BYK348 additive with PW-SnO An aqueous solution of PW-SnO2 (8.5 wt%, Example 1) was mixed with an aqueous solution of BYK348 in water (0.5 wt%).

[0287] After mixing, a droplet was cast onto a SiN surface with a trench structure. The trench substrate was prepared as described above (see the "Substrate with Trench Substrate" section). The resulting SEM image is shown in Figure 15A. It can be seen that complete trench filling was achieved.

[0288] Example T2-B: BYK348 additive with PW-SnO To study the optical properties of films containing the BYK348 additive, a formulation of 8.5 wt% PW-SnO2 with 0.5 wt% BYK348 in water was prepared.

[0289] An additional film was deposited onto the trench substrate using a spin-coating technique. For this formulation, the trench was partially filled and voids appeared after hard baking at 200°C, as shown in Figure 15B.

[0290] The SEM image in FIG. 15B shows that there is only partial filling (about 50%) and some small side voids appear, but the filling is good compared to that shown in FIG.

[0291] Example T2-C: BYK348 Additive with Ellipsometry of Example #2 [NbO 19 ] -8 (12 wt. %, as described in Example 2) was mixed with an aqueous solution containing BYK348 to obtain 0.5 wt. % BYK348.

[0292] Si wafers were used as substrates at the ends of the films, and the films were soft-baked at 100°C for 1 minute and hard-baked at 300°C for 10 minutes, after which the refractive index and extinction coefficient were measured.

[0293] The material so obtained had a lower refractive index compared to the material obtained in Example 2.

[0294] The results of the ellipsometry measurements are shown in Table 13.

[0295] Example T3 A blend of PW-SnO2 (Example 1) and POM additive PW-A in a weight ratio of 0.85 / 1 was prepared using the same technique as described in Example M2. Take 100 μL of the PW-SnO2 8.5 wt% material and 100 μL of the PW-A material.

[0296] The formulation was deposited as a thin film on a Si substrate and soft-baked at 100°C for 1 minute and hard-baked at 300°C for 10 minutes.

[0297] The results of the ellipsometry measurements are shown in Table 13.

[0298] The formulation was deposited by spin coating onto a trench sample and a cross-sectional SEM image is shown in FIG.

[0299] This formulation provided trench filling after spin coating with BYK348 as well as better trench filling than the pure material (PW-SnO2) described in Example 1. However, BYK348 reduces the RI.

[0300] Example T4: NbO—Sn 0.25 Ti 0.75 O2+NbO-A The formulation is described in Example M4 above.

[0301] After soft baking at 100° C. for 1 minute, spin coating was applied to the trench samples, and SEM images under 114 nm trench (FIG. 17A) and 87.5 nm (FIG. 17B) widths show partial filling.

[0302] After hard baking at 300° C. for 10 minutes (followed by soft baking at 100° C. for 1 minute), the 84 nm trench width was only partially filled (FIG. 17C).

[0303] Example T5 NbO-Sn 0.25 Ti 0.75 O2+NbO-A To obtain complete trench filling, a two-layer deposition technique was performed using the same formulation as in Example T4.

[0304] The first sample was prepared with a single soft bake step (100 °C for 1 min) after depositing both layers. Figures 18A and 18B show the surface feature fill after spin-coating the mixture NbO-SnO2\TiO2 25 / 75%+NbO-A and soft-baking at 100 °C for 1 min. The trench widths are 114 nm (Figure 18A) and 131 nm (Figure 18B).

[0305] In Figure 18A, the two trenches on the right are filled almost to the top of the trench, however the wider gap of >130 nm shown in Figure 12B was not completely filled.

[0306] A sample made with two layers (no soft bake between layers), soft baked after the second layer, and hard baked at 300° C. is shown in Figure 18C. As can be seen, the gap remains filled and no voids are present.

[0307] [Table 13]

Claims

1. 1. A formulation for preparing an optical metal oxide layer, said formulation comprising: (i) a polyoxometallate moiety represented by formula (Ia), and (Q ｌ ) ｎ＋ [X ｚ Y ｐ O ｙ ] ｎ－ (Ia) Nanoparticles represented by formula (Ib): M ｉ M’ ｊ M’’ ｆ O ｋ (Ib) [In the formula, each Q independently represents a cation; l is any number ranging from 1 to 20; n is the total positive charge n+ of l cations Q and polyanion [X ｚ Y ｐ O ｙ ] is a number representing the corresponding negative charge n-; X is a heteroatom; Y is a metal; z is 0 to 20; p is 1 to 100; y is 2 to 400; M, M', and M'' are each independently a metal; i, j, and f are each independently an integer or fractional number from 0 to 10, provided that at least one of l, j, and f is not 0; and k is any number ranging from 1 to 20; (ii) one or more formulation vehicles.

2. The complex is TiO ２ Na complexed to ７ [P.W. １１ O ３９ ], TiO ２ Na complexed to ３ [PMo １２ O ４０ ], TiO ２ K complexed to ６ [P ２ W １８ O ６２ ], TiO ２ K complexed to ６ [P ２ Mo １８ O ６２ ], or TiO ２ Q complexed to ｌ [SiW １１ O ３９ ]. The complex of claim 1 .

3. However, the formula Ib is TiO ２ When formula Ia is Na ７ [P.W. １１ O ３９ ], Na ３ [PMo １２ O ４０ ], K ６ [P ２ Mo １８ O ６２ ], K ６ [P ２ W １８ O ６２ ], or Q ｌ [SiW １１ O ３９ ]. The formulation of claim 1 .

4. The complex has the formula (I): ([Q ｌ ] ｎ＋ [POM] ｎ－ ) ｍ (NP) ｒ (I) [In the formula, POM is a polyoxometalate represented by formula (Ia) above; NPs are metal oxide or mixed metal oxide nanoparticles represented by formula (Ib); m represents the number of polyoxometalate ligands per nanoparticle and is any number ranging from 1 to 5000; and r is any number ranging from 1 to 20,000 and represents an empirical metal oxide unit in said nanoparticles.

5. 5. The formulation of any one of claims 1 to 4, wherein M, M', and M'' are each independently Ba, Sr, Ti, Zr, Nb, Hf, Ta, Zn, Al, In, Sn, or Ce, preferably Ba(II), Sr(II), Ti(III), Ti(IV), Zr(IV), Nb(V), Nb(III), Hf(IV), Ta(V), Zn(II), Al(III), In(III), Sn(II), Sn(IV), or Ce(IV).

6. A formulation according to any one of claims 1 to 5, wherein M' is Ti and / or M is Sn.

7. A formulation according to any one of claims 1 to 6, wherein i is <1, j is 1-i and f is 0.

8. The nanoparticles are SnO ２ , CeO ２ , ZrO ２ , TiO ２ , NbO ２ , HfO ２ , or Ta ２ O ５ The formulation according to any one of claims 1 to 6, wherein

9. 9. The formulation of any one of claims 1 to 8, wherein X is P, Ar, Sb, S, Si, Ge, B, Be, Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, or is absent.

10. 10. The formulation of any one of claims 1 to 9, wherein Y is W, Nb, V, Ta, Ti, Zr, Hf, Mo, Zn, In, or Sn.

11. The formulation of any one of claims 1 to 10, wherein the polyoxometallate moiety is a heteropolyoxotungstate or a polyoxoniobate.

12. The formulation comprises (iii) one or more additives, each of which individually comprises a further complex according to any one of claims 1 to 11, Na ３ P.W. １２ O ４０ ＊ nH ２ O.K. ８ NbO １９ ＊ nH ２ The formulation of any one of claims 1 to 11, wherein the additive is selected from the group consisting of a wetting agent, a dispersing agent, an adhesion promoter, a polymer matrix, and a surfactant.

13. The blend comprises Na ３ P.W. １２ O ４０ ＊ nH ２ O or K ８ Nb ６ O １９ ＊ nH ２ 13. The formulation of any one of claims 1 to 12, further comprising O, and optionally a surfactant such as a polyether modified siloxane.

14. 1. A method for preparing an optical metal oxide layer, comprising the steps of: (a) providing a formulation according to any one of claims 1 to 13; (b) applying the formulation to the surface of a substrate; (c) converting the formulation into an optical metal oxide layer on the surface of the substrate.

15. 15. An optical device, preferably an augmented reality and / or virtual reality device, comprising an optical metal oxide layer, said layer being obtainable by the method according to claim 14.

16. Use of a formulation according to any one of claims 1 to 13 for preparing an optical metal oxide layer or an optical device.

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