Light emitting device with improved light outcoupling

Abstract

Optoelectronic devices are provided that include a composite film in a multi-layer package stack. Methods of forming light reflection modifying structures, as well as other polymeric device layers, using inkjet printing are also provided. The composite film includes a first lower refractive index domain and a second higher refractive index domain.

Description

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 62 / 607,824, filed on December 19, 2017, the entire content of which is incorporated herein by reference. Background Art

[0002] Multilayer encapsulation stacks composed of alternating inorganic and organic polymer films have been used to protect light-emitting devices from the damaging effects of exposure to water vapor and oxygen. Unfortunately, the difference in refractive index (RI) between the inorganic layer in the stack and the adjacent organic polymer layer with a lower refractive index can cause total internal reflection of light at the interface between the two layers, which reduces the proportion of light that can exit the device. In addition, even when there is no high RI mismatch between the inorganic and organic polymer layers, the light-emitting device may suffer from limited light output due to total internal reflection of light at the interface between the terminal layer in the encapsulation stack and the overlying device layer or at the interface between the terminal layer in the encapsulation stack and air in the absence of an overlying device layer. Technical Field The invention described herein relates to encapsulation stacks and light-emitting devices, such as organic light-emitting diode (OLED) devices including multilayer encapsulation stacks. The multilayer encapsulation stack provides reduced total internal reflection and thus improved light output efficiency relative to conventional encapsulation stacks. Brief Description of the Drawings

[0004] Figure 1A is a schematic cross-sectional view showing an embodiment of an OLED device, the OLED device including a multilayer encapsulation stack having a composite film, wherein a single high refractive index dome-shaped structure is disposed on each sub-pixel of the device. Figure 1B is a top view of the OLED device.

[0005] Figure 2 is a schematic cross-sectional view showing a second embodiment of an OLED device, the OLED device including a multilayer encapsulation stack having a composite film, wherein a single high refractive index cylindrical structure is disposed on each sub-pixel of the device.

[0006] Figure 3 is a schematic cross-sectional view showing an embodiment of an OLED device, the OLED device including a multilayer encapsulation stack having a composite film, wherein a plurality of high refractive index dome-shaped structures are disposed on each sub-pixel of the device.

[0007] Figure 4It is a schematic top view showing another embodiment of an OLED device, the OLED device including a multi-layer encapsulation stack having a composite film, wherein a plurality of high refractive index dome-shaped structures are provided on each sub-pixel of the device.

[0008] Figure 5A It is a schematic cross-sectional view showing an OLED device having a composite film on top of its multi-layer encapsulation stack.

[0009] Figure 5B It shows in more detail Figure 5A the schematic diagram of the multi-layer encapsulation stack.

[0010] Figure 6 It is for manufacturing Figure 1A and Figure 1B the schematic diagram of the method for an OLED device.

[0011] Figure 7 It is for manufacturing Figure 2 the schematic diagram of the method for an OLED device. Specific embodiments

[0012] The devices described herein include various electronic and optoelectronic devices, wherein the active area of the device is encapsulated using a protective multi-layer encapsulation stack. In an OLED or other electronic or optoelectronic device, the "active area" does not need to meet any requirements for electrical energy amplification or transistor activity, and generally can refer to an area where electrical or optoelectrical activity (e.g., light emission, light absorption, or light conversion) can occur. The active area itself will typically be a multi-layer structure composed of multiple device layers, the device layers including, for example, electrodes, charge injection layers, charge transport layers, and / or light-emitting layers. Although the following uses a top-emitting OLED device as an illustrative example to describe the various benefits of the encapsulation stack, the encapsulation stack can be applied to other light-emitting devices, including other top-emitting lighting devices, top-emitting quantum dot (QD)-LED devices, micro-LED displays, and QD-photoluminescence (PL) emission color converters. Additionally, this technology can be applied to light sensors and photovoltaic cells, where a large amount of light coupled into the device is beneficial.

[0013] In Figure 1A the schematic diagram shown in the cross-sectional view of an embodiment of an OLED device 100, the OLED device 100 includes a multi-layer encapsulation stack. The top view of the OLED device is shown in Figure 1Bis shown. This embodiment of the OLED device includes a plurality of active regions 104 and an OLED device substrate 102. A multilayer encapsulation stack 106 is disposed over the active regions 104. The multilayer encapsulation stack 106 (which protects the underlying active regions 104 from degradation due to exposure to air and / or moisture) includes a first inorganic barrier layer 108 that inhibits exposure of the active regions 104 to water vapor, oxygen, and / or other reactive gases present in the surrounding atmosphere. A composite film 109 including a first domain is adjacent to the first inorganic barrier layer 108, and the first domain includes a first polymer layer 110. The first polymer layer 110 is composed of one or more organic polymers and provides a planarization layer to planarize the encapsulation stack. In Figure 1A In the illustrated embodiment of the OLED device, the multilayer encapsulation stack 106 includes a second inorganic barrier layer 108A disposed over the composite film 109. In other embodiments of the encapsulation stack, the order of the layers may be reversed such that the composite film 109 is fabricated first, followed by the first inorganic barrier layer 108. In such an embodiment, a second planarizing polymer layer and a second inorganic barrier layer may then be deposited in sequence to provide sufficient encapsulation for the underlying device. Thus, a modified process includes depositing the composite film 109 directly on top of the active regions of the device, followed by depositing the first inorganic barrier layer, followed by depositing the second polymer layer, followed by depositing the second inorganic barrier layer. Additionally, a greater or lesser number of inorganic barrier layers and polymer layers may be provided. For example, Figure 1A the encapsulation stack may have a second polymer layer disposed on the second inorganic barrier layer 108A. Figure 1A The active regions 104 of the OLED device may be light-emitting sub-pixels (e.g., red, green, and / or blue sub-pixels) embedded in or supported by the OLED device 102 substrate. Each of these sub-pixels may include an organic light-emitting layer disposed between a first electrode (e.g., a cathode) and a second electrode (e.g., an anode). Optionally, an electron transport layer and / or an electron injection layer may be disposed between the cathode and the light-emitting layer, and a hole transport layer and / or a hole injection layer may be disposed between the anode and the light-emitting layer.

[0014] At least one layer in the encapsulation stack is a composite film that includes a first domain formed of a first polymer and a second domain formed of a second polymer, wherein the second domain has a higher RI than the first domain, and further wherein the second domain desirably has the same or nearly the same RI as the inorganic material of the first inorganic barrier layer 108. The second domain may be a discontinuous domain that includes a plurality of sub-domains, typically surrounded or embedded in the first domain. For example, in Figure 1A and Figure 1BIn an embodiment of the composite film 109 shown, the sub-domains are a plurality of dome-shaped structures 112. Due to the reduced RI mismatch between the sub-domains 112 and the inorganic barrier layer 108, total internal reflection of light emitted from the sub-pixels 104 is reduced at the interface between the inorganic barrier layer 108 and the structures 112. A suitable RI for the sub-domains 112 will depend on the RI of the inorganic barrier layer. In some embodiments of the multi-layer encapsulation stack, the RI of the sub-domains and the inorganic barrier layer differ by no more than ±15%, including no more than 10%, and also including no more than 5%. By way of illustration only, for an inorganic barrier layer comprising SiNx having an RI in the range of about 1.85 to about 2.2, the sub-domains can have an RI of about 1.7 or higher.

[0015] The material for preparing the higher RI domains can be a polymeric material comprising one or more organic polymers or polymer composites, including polymeric materials comprising inorganic particles dispersed in a polymer matrix. Suitable polymers include acrylics, urethanes, and epoxies. Suitable inorganic particles include metal oxide particles such as zirconia, titania, hafnia, zinc oxide, and mixtures of two or more thereof. Optionally, the inorganic oxide particles can be surface-functionalized with a capping agent that improves their dispersion in the polymer matrix. Such capping agents can include 2-[2-(2-9-methoxyethoxy)ethoxy]acetic acid and / or methoxy(triethyleneglyoxy)propyltrimethoxysilane and / or 3-methacryloxypropyltrimethoxysilane and / or n-n-octyltrimethoxysilane and / or dodecyltrimethoxysilane and / or m,p-phenethylphenethyltrimethoxysilane. In some embodiments, the same metal oxide is present in the higher RI domains of the composite film and the inorganic barrier layer. By way of illustration only, the high RI polymer-nanocrystal composites described in U.S. Patent Publication No. 2014 / 0322549 can be used to form the higher RI domains in the composite film of the multi-layer encapsulation stack described herein, the entire disclosure of which is incorporated herein by reference.

[0016] In Figure 1A an embodiment of the composite film, the sub-domains 112 provide a non-planar interface between the higher RI material of the sub-domains and the lower RI material of the first domain, whereby they change the angle of the light reflected at that interface such that total internal reflection is suppressed and light output coupling and extraction are enhanced. In some embodiments of the higher RI domain material comprising particles, the particles can act as scattering centers to further reduce internal reflection and light trapping. However, for applications where light scattering is not desired, the particles can have a diameter small enough to avoid or minimize light scattering. The sub-domains of the composite film can have various shapes and sizes. For example, as Figure 1AAs shown, the sub-domains can be structures such as hemispheres (domes) arranged in a regular array or random pattern. Once formed, the structure can be covered with a layer of polymer material with a lower RI of the first domain to form a smooth planar or substantially planar surface on which the next inorganic barrier layer can be formed. Optionally, the sub-domains can be cylinders 114 arranged in a regular array or random pattern, as Figure 2 shown. In this embodiment of the device, the first domain 110 surrounds the cylinder 114, and the surface formed by the first domain 110 and the cylinder 114 provides a smooth planar or substantially planar surface on which the next inorganic barrier layer 108A can be formed. The use of a cylindrical structure may be beneficial because light reflected at the vertical interface 116 formed between the cylindrical sub-domain 114 and the first domain 110 can be directed towards the light-emitting surface of the device, thereby further reducing the trapping of light in the first inorganic barrier layer 108 and / or the active region 104.

[0017] The size and position of the sub-domains are not strictly limited as long as they can reduce total internal reflection within the device. For example, various embodiments of sub-domains including hemispherical structures have a radius in the range of 1 μm to 50 μm, an inter-structure spacing (pitch) in the range of 1 μm to 100 μm, and / or a height in the range of 1 μm to 50 μm; however, sizes outside these ranges can be used. Once formed, the sub-domains can be covered with a layer of polymer material with a lower RI of the first domain or laterally surrounded within the layer to form a smooth planar or substantially planar composite film surface on which the next inorganic barrier layer can be formed. Optionally, the first domain and the second domain can be formed simultaneously as a composite film having a smooth planar or substantially planar surface on which the next inorganic barrier layer can be formed.

[0018] To avoid or reduce color bleeding and other undesirable visual effects, the sub-domains can be patterned (e.g., inkjet printed) at a resolution commensurate with the resolution of the display device. For example, in some embodiments of a multi-layer encapsulation stack, there is one sub-domain associated with each pixel or with each sub-pixel within a pixel, as Figure 1A 、 Figure 1B and Figure 2 shown. In other embodiments, the sub-domains are much smaller than the pixels or sub-pixels such that multiple sub-domains are disposed on each pixel or sub-pixel. For example, the sub-domains can be located in clusters on each pixel or sub-pixel in the display device. This is schematically shown in Figure 3 and Figure 3A cross-sectional view showing a part of a display device is presented. The display device includes an OLED sub-pixel 304, on which a packaging stack 306 is provided. The packaging stack 306 includes a first inorganic barrier layer 308, a composite film 309, and a second inorganic barrier layer 308A above the composite film 309. The composite film 309 includes a first domain 310 and a second domain including a plurality of dome-shaped sub-domains 312 aggregated above the OLED 304.

[0019] In Figure 4 the concept of having more than one sub-domain of the composite film located on a single sub-pixel is further illustrated. Figure 4 A top view showing three sub-pixels (red (R), green (G), and blue (B)) is presented, with each sub-pixel associated with three overlying sub-domains 412 of the composite film.

[0020] The advantage of implementing the composite film on top of the first (i.e., lowest) inorganic barrier layer in the multi-layer packaging stack rather than on top of the packaging stack is that such placement reduces the distance between the light-emitting layer of the sub-pixel and the high-RI sub-domain of the composite film. This is beneficial because it helps reduce color bleeding, which can degrade the perceived resolution, black contrast, and / or color gamut of the OLED display.

[0021] Although in Figure 1A 、 Figure 1B and Figure 2 the composite film is directly positioned on the first inorganic barrier layer of the packaging stack in the shown device embodiments, in other embodiments, the composite film can be formed on the second (or higher) inorganic barrier layer within the packaging stack. For example, the composite film can be placed on the top inorganic barrier layer of the packaging stack, as shown in the OLED devices shown in Figure 5A and Figure 5B In addition, the composite film can be provided on more than one inorganic barrier layer in the multi-layer packaging stack. In other embodiments, the composite film can be directly placed on the top surface of the underlying active region (e.g., on the top electrode of the OLED stack) to provide the first layer of the packaging stack.

[0022] In embodiments where the composite film is placed on the second or higher inorganic barrier layer in the encapsulation stack, all layers in the encapsulation stack below the composite film, including the polymer planarization layer, should be made of high RI materials. In such embodiments, the underlying planarization layer may have the same material composition as the second domain in the composite film. However, the planarization layer and the second domain of the composite film do not have to have the same composition, as long as the planarization layer has an RI that is the same as or almost the same as (e.g., within 15% difference) the RI of the inorganic material of the inorganic barrier layer in the encapsulation stack. By way of illustration only, for an inorganic barrier layer comprising SiNx having an RI in the range of about 1.85 to about 2.2, the high RI planarization layer may have an RI of about 1.7 or higher.

[0023] Figure 5A An embodiment of an OLED display device including a composite film as the last layer of the encapsulation stack is schematically shown. The figure is a cross-sectional view and includes components of the active area 530 of the OLED device. These include a reflective anode 522, an organic layer stack 524, and a semi-transparent cathode 526. An encapsulation stack 506 and a top protective glass layer 528 are provided above the active area 530. The organic layer stack 524 may include, from top to bottom: an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, and a hole injection layer. The OLED device may also include a support substrate 520. In the embodiment shown here, the last layer of the encapsulation stack 506 includes a composite film 509 of the type described herein disposed on another underlying encapsulation stack layer 511 (shown here as a single block for simplicity). Figure 5B A more detailed cross-sectional view of the encapsulation layer 506 with the upper composite film 509 is shown. The composite film has a structure similar to the Figure 3 structure shown, except that the composite film 509 is at the top of the encapsulation stack and the underlying layers of the encapsulation stack include one or more inorganic barrier layers 507 made of high RI materials (which may be the same material as that forming the sub-domain 512). For simplicity, Figure 5A and 5B all layers in the display device shown in are shown as having the same thickness. However, as will be understood by those of ordinary skill in the art, depending on their specific functions, the layers in an actual display device will have different thicknesses. For example, the organic layer stack will typically be significantly thinner than the encapsulation stack layers 511 and 509.

[0024] The use of a composite film that includes a high RI region within a layer of a encapsulation stack can significantly improve the light extraction efficiency and integrated current efficiency of an OLED device that includes the film, relative to an otherwise identical OLED device that does not include such a film. By way of illustration, various embodiments of the encapsulation stack according to the present teachings increase the extraction efficiency of the OLED device by at least 30% (e.g., 30% to 40%), and increase the integrated current efficiency of the OLED device by at least 70% (e.g., 70% to 100%). Additionally, an encapsulation stack that includes a composite film can reduce the viewing angle dependence of the emitted light, resulting in a higher quality display.

[0025] Examples of inorganic materials for inorganic barrier layers that can be used to fabricate multi-layer encapsulation stacks can include, for example, various nitrides, oxides, and oxynitrides such as silicon nitride (SiNx), silicon oxide, Al2O3, TiO2, HfO2, and silicon oxynitride (SiO X N Y ). The inorganic barrier layer can be deposited or otherwise formed over the active region, and can be blanket coated (e.g., via chemical and / or physical vapor deposition) over the entire or substantially the entire exposed surface of the substrate and the active region.

[0026] Polymers that can be used to fabricate the first and second regions of the composite film and other polymer planarization layers of the multi-layer encapsulation stack include various polymeric materials that can be cured using one or more of thermal (e.g., baking), radiation (e.g., ultraviolet exposure), or other energy-based (e.g., electron beam) curing techniques, and once cured, can form polymer thin films and / or polymer structures. Various polymer deposition techniques can be used to form the various polymer layers of the encapsulation stack. In some embodiments of the OLED device, the polymer layers of the encapsulation stack, including the composite film, are formed by inkjet printing an ink composition that includes curable monomers, oligomers, and / or polymers onto a substrate (e.g., onto the inorganic barrier layer) and curing the composition to form a polymer film. Additionally, the ink composition can include one or more crosslinkers, polymerization initiators, and / or solvents. The polymer planarization layer can also be prepared by applying the ink composition to the device substrate using a coating technique other than inkjet printing, followed by curing the composition to form a polymer film.

[0027] Examples of acrylate and methacrylate monomers (collectively referred to herein as "(meth)acrylate" monomers) that can be included in the ink composition include mono(meth)acrylate monomers, di(meth)acrylate monomers, and higher functionality (meth)acrylate monomers. In various embodiments of the ink composition, the (meth)acrylate monomer is a polyether. In various embodiments of the ink composition, the (meth)acrylate monomer is an alkoxylated aliphatic di(meth)acrylate monomer. These include neopentyl glycol-based di(meth)acrylates, including alkoxylated neopentyl glycol diacrylates such as neopentyl glycol propoxylate di(meth)acrylate and neopentyl glycol ethoxylate di(meth)acrylate. Other suitable (meth)acrylate monomers include, but are not limited to: alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, and benzyl methacrylate; cyclic trimethylolpropane formal (meth)acrylate; alkoxylated tetrahydrofurfuryl (meth)acrylate; phenoxyalkyl (meth)acrylates such as 2-phenoxyethyl (meth)acrylate and phenoxymethyl (meth)acrylate; 2-(2-ethoxyethoxy)ethyl (meth)acrylate. Other suitable di(meth)acrylate monomers include: 1,6-hexanediol diacrylate, 1,12-dodecanediol di(meth)acrylate; 1,3-butanediol di(meth)acrylate; bis(ethylene glycol dimethyl)acrylate methyl ester, and polyethylene glycol di(meth)acrylate monomers. Other mono- and di(meth)acrylate monomers that can be included alone or in combination in various embodiments of the ink composition include: dicyclopentenyl oxyethyl acrylate (DCPOEA), isobornyl acrylate (ISOBA), dicyclopentenyl oxyethyl methacrylate (DCPOEMA), isobornyl methacrylate (ISOBMA), and N-octadecyl methacrylate (OctaM). Homologues of ISOBA and ISOBMA (collectively referred to as "ISOB(M)A" homologues) can also be used, where one or more methyl groups on the ring are replaced by hydrogen.

[0028] The polyfunctional (meth)acrylate crosslinker desirably has at least three reactive (meth)acrylate groups. Thus, the polyfunctional (meth)acrylate crosslinker can be, for example, a tri(meth)acrylate, a tetra(meth)acrylate, and / or a higher functionality (meth)acrylate. Pentaerythritol tetraacrylate or pentaerythritol tetramethacrylate, bis(trimethylolpropane) tetraacrylate, trimethylolpropane triacrylate, and bis(trimethylolpropane) tetramethacrylate are examples of polyfunctional (meth)acrylates that can be used as the primary crosslinker. The term "primary" as used herein means that other components of the ink composition can also participate in crosslinking, although this is not their primary functional purpose.

[0029] The components for forming the nanocomposite coating in U.S. Patent Application Publication No. 2014 / 0322549 are examples of ink components that can be used for the second domain of forming a composite film and / or any high RI planarization layer in the encapsulation stack. The ink components described in U.S. Patent Application Nos. US20160024322, US2017 / 0062762, and US2017 / 0358775 are examples of ink components that can be used for the first domain of forming a composite film and / or other polymer planarization layers in a multi-layer encapsulation stack.

[0030] Regarding the properties of the ink components applied via inkjet printing, the surface tension, viscosity, and wetting properties of the initial ink components should be adjusted to allow the components to be dispensed through the inkjet printing nozzle without drying or clogging on the nozzle at the temperature for printing (e.g., room temperature; about 25 °C). By way of illustration, some embodiments of the ink components for forming a polymer layer have a viscosity between about 10 cP and about 28 cP (including, for example, between about 15 cP and about 26 cP) at 25 °C and a surface tension between about 28 dynes / cm and about 45 dynes / cm at 25 °C. To adjust or optimize the ink components for inkjet printing, solvents, surfactants, viscosity modifiers, etc. can be included in the ink components. Suitable organic solvents include esters and ethers. In addition to addressing the viscosity and surface tension of the ink, the surface energy of the surface on which the ink component is deposited can also be modified to achieve the desired ink spreading. This can be done by plasma treatment, exposure to a gas containing a surface modifier, and coating with a thin primer layer containing a surface modifier. These surface modifiers can also be deposited in a patterned manner, thereby forcing the ink to be pinned at a defined position on the substrate.

[0031] A method of manufacturing Figure 1A and Figure 1B an OLED device of the type shown in Figure 6is schematically shown. Initially, one or more active regions (e.g., sub-pixels) 104 are formed on the device substrate 102, and the first inorganic barrier layer 108 is deposited as a film on the active regions. Next, droplets of the ink composition 600 comprising materials that make up the sub-domains of the composite film are deposited (e.g., inkjet printed) on the active regions 104 on top of the first inorganic barrier layer 108 (panel (a)). The droplets spread and solidify on the surface to form a dome-shaped structure 112 (panel (b)). In the embodiment shown here, each active region has a dome-shaped structure. If the active region includes sub-pixels that emit different colors, the composition of the sub-domains can be adjusted independently to meet the required optical properties of the different sub-pixels. Although not shown here, after printing, pixel banks can be used to confine the spread ink composition 600. Optionally, the ink composition 600 can be confined by patterning the substrate surface with hydrophobic and / or hydrophilic regions that control the wetting characteristics of the ink composition. Next, droplets of the ink composition 602 comprising materials that make up the first lower RI domain of the composite film are deposited (e.g., inkjet printed) as a coating on the first inorganic barrier layer 108 above the higher RI structure 112 (panel (c)). The coating then solidifies to form the first domain 110. Finally, the second inorganic barrier layer 108A is deposited as a film on the first polymer layer that makes up the first domain of the composite film 109 (panel (d)). In an alternative method, the higher RI ink composition 600 is not cured before depositing the lower RI ink composition 602. In this case, the two ink compositions are optimized such that they do not mix with each other, or such that they only partially mix with each other, thus preserving the out-coupling advantages of the structures in the final device. In a variant of this process, the ink composition that forms the sub-domain structure 112 is cured after deposition but before depositing the lower RI ink composition 602 that forms the first domain. In this case, the interface between the two cured domains is well-defined and abrupt. This method places fewer restrictions on the ink composition system because mixing between the two ink compositions is inhibited by the curing step.

[0032] A method of manufacturing Figure 2 an OLED device of the type shown in Figure 7is schematically shown. In this method, the ink composition 400 for fabricating the higher RI structure of the sub-domain and the ink composition 602 for fabricating the first domain are designed such that they similarly wet the surface of the first inorganic barrier layer 108 to form a planar coating on the surface, but they will not substantially mix with each other within the coating. Droplets of the ink compositions 600 and 602 can be printed (simultaneously or sequentially) onto the first inorganic barrier layer 108 without curing between the printing steps (panels (a) and (b)), and then the coating can be cured, thereby forming a cylindrical sub-domain structure (or cone-like feature) 114 laterally surrounded by a polymer layer of the first domain 110, and subsequently depositing a second inorganic barrier layer 108A (panel (c)). In this method, some mutual mixing between the ink compositions is allowed as long as the mutual mixing region is relatively small and the RI contrast between the two domains is retained.

[0033] An industrial inkjet printing system that can be housed in an enclosure configured to provide a controlled process environment can be used to deposit the ink compositions onto a device substrate. Inkjet printing for depositing the ink compositions described herein can have several advantages. First, since inkjet-based manufacturing can be performed at atmospheric pressure, a series of vacuum processing operations can be eliminated. Additionally, during the inkjet printing process, the ink compositions can be localized to cover portions of the OLED substrate above and near the active region to effectively encapsulate the active region, including the lateral edges of the active region. The targeted patterning using inkjet printing results in the elimination of material waste and the elimination of additional processing typically required to pattern organic thin films (e.g., required by various mask techniques). The ink compositions can be printed using a printing system such as that described in, for example, U.S. Patent No. 9,343,678.

[0034] This teaching is intended to be illustrative and not restrictive. In the specification, various features may be grouped together to streamline the disclosure. This should not be construed as intending that the unclaimed disclosed features are necessary for any claim. Rather, the inventive subject matter may lie in less than all of the features of a particular disclosed embodiment. Thus, the appended claims are hereby incorporated into the detailed description by way of example or embodiment, each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments may be combined with each other in various combinations or arrangements. The scope of the present invention should be determined with reference to the appended claims together with the full scope of equivalents to which such claims are entitled.

Claims

1. An optoelectronic device, comprising: At least one active region; And A multi-layer encapsulation stack disposed above the at least one active region, the multi-layer encapsulation stack comprising: An inorganic barrier layer; A composite film, the composite film being adjacent to the inorganic barrier layer and comprising a first domain and a second domain, the second domain comprising a plurality of sub-domains, wherein the second domain has a higher refractive index than the first domain.

2. The optoelectronic device according to claim 1, wherein, The optoelectronic device is an organic light emitting diode device, and the at least one active region comprises light emitting pixels.

3. The optoelectronic device according to claim 1, wherein, The second domain comprises inorganic particles dispersed in a polymer matrix.

4. The optoelectronic device according to claim 1, wherein, The inorganic barrier layer comprises silicon nitride, silicon oxide, or silicon oxynitride.

5. The optoelectronic device according to claim 4, wherein, The second domain comprises zirconium oxide, titanium oxide, hafnium oxide, zinc oxide, or a mixture of two or more thereof dispersed in a polymer matrix.

6. The optoelectronic device according to claim 1, wherein, The second domain comprises zirconium oxide, titanium oxide, hafnium oxide, zinc oxide, or a mixture of two or more thereof dispersed in a polymer matrix.

7. The optoelectronic device according to claim 6, wherein, The polymer matrix is an acrylic matrix.

8. The optoelectronic device according to claim 1, wherein, The sub-domains are dome-shaped.

9. The optoelectronic device according to claim 1, wherein, The sub-domains are cylindrical or conical in shape.

10. A method of forming an encapsulated optoelectronic device, the method comprising: Forming an inorganic barrier layer on at least one active region of the optoelectronic device; Inkjet printing a first curable ink composition as a plurality of droplets on the inorganic barrier layer; Curing the plurality of droplets to form a plurality of sub-domains on the inorganic barrier layer; Inkjet printing a second ink composition around the plurality of droplets or above the sub-domains; And Curing the second ink composition to form a first domain comprising a polymer film around the sub-domains, wherein the sub-domains have a higher refractive index than the first domain.

11. The method according to claim 10, wherein, The optoelectronic device is an organic light emitting diode device, and the at least one active region comprises light emitting pixels.

12. The method according to claim 10, wherein, The plurality of droplets are cured to form the plurality of sub-domains before the second ink composition is inkjet printed.

13. The method according to claim 12, wherein, The sub-domains are dome-shaped.

14. The method according to claim 10, wherein, The second ink composition is substantially immiscible with the first ink composition, and further wherein, Before the first ink composition and the second ink composition are cured, the second ink composition is printed around the droplets of the first ink composition.

15. The method according to claim 14, wherein, The sub-domains are cylindrical or conical in shape.

16. The method according to claim 10, wherein, The first ink composition comprises inorganic particles and one or more curable monomers, oligomers or polymers.

17. The method according to claim 16, wherein, The inorganic particles comprise zirconium oxide, titanium oxide, hafnium oxide, zinc oxide, or a mixture of two or more thereof.

18. The method according to claim 17, wherein, The one or more curable monomers, oligomers or polymers comprise one or more acrylic monomers, acrylic oligomers or acrylic polymers.

19. The method according to claim 10, wherein, The inorganic particles comprise zirconium oxide, titanium oxide, hafnium oxide, zinc oxide, or a mixture of two or more thereof.

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