Multilayer film for encapsulating oxygen and/or moisture sensitive electronic devices

Abstract

The present invention relates to a multilayer barrier film capable of encapsulating a moisture and/or oxygen sensitive electronic or optoelectronic device, the barrier film including at least one nanostructured layer including reactive nanoparticles capable of interacting with moisture and/or oxygen, the reactive nanoparticles being distributed within a polymeric binder, and at least one ultraviolet light neutralizing layer comprising a material capable of absorbing ultraviolet light, thereby limiting the transmission of ultraviolet light through the barrier film.

Claims

1. A method of fabricating an encapsulated electronic device, comprising: providing a vacuum enclosure, arranging within the vacuum enclosure a base substrate having arranged thereon an electronic device to be encapsulated, and forming a multilayer barrier film on the electronic device, the multilayer barrier film capable of encapsulating a moisture and/or oxygen sensitive electronic or optoelectronic device, and comprising: at least one nanostructured layer comprising reactive nanoparticles capable of interacting with moisture and/or oxygen, and inert nanoparticles which do not interact with moisture and/or oxygen and which are adapted to obstruct the permeation of moisture and/or oxygen, said reactive nanoparticles and inert nanoparticles being distributed within a polymeric binder, and at least one ultraviolet light neutralizing layer comprising a material capable of absorbing ultraviolet light, thereby limiting the transmission of ultraviolet light through the multilayer barrier film on the electronic device, thereby encapsulating the electronic device, wherein forming the multilayer barrier film on the electronic device comprises: forming a first layer comprising a material capable of absorbing ultraviolet light on the electronic device, the first layer constituting the ultraviolet light neutralizing layer, mixing reactive nanoparticles capable of interacting with moisture and/or oxygen and inert nanoparticles which do not interact with moisture and/or oxygen and which are adapted to obstruct the permeation of moisture and/or oxygen with a polymerizable compound having at least one polymerizable group to form a nanoparticulate mixture, applying the nanoparticulate mixture on the first layer formed on the electronic device, and exposing the nanoparticulate mixture to ultraviolet light to cure the nanoparticulate mixture during which the first layer functions to limit the transmission of the ultraviolet light onto the electronic device, thereby forming a second layer constituting the nanostructured layer on the first layer.

2. The method of claim 1, further comprising the step of forming a secondary encapsulation over the electronic device encapsulated by the multilayer barrier film, wherein the multilayer film encapsulating the electronic device is contacted with a curable adhesive in an amount sufficient to surround the electronic device encapsulated by the multilayer barrier film, attaching a cover substrate on the adhesive prior to compressing the adhesive against the electronic device encapsulated by the multilayer barrier film, mechanically compressing the cover substrate against the adhesive at an elevated temperature, and curing the adhesive.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Illustrative embodiments will now be described by way of non-limiting examples only, with reference to the accompanying drawings, in which:

(2) FIG. 1 depicts an encapsulated OLED according to one embodiment of the invention.

(3) FIG. 2A depicts one embodiment of the layer structure of the multilayer barrier film. FIG. 2B depicts another embodiment of the layer structure of the multilayer barrier film with adhesive layer and glass covered incorporated.

(4) FIG. 3A depicts an OLED encapsulated within a rim-sealed panel, underneath a multilayer barrier film according to one embodiment of the invention.

(5) FIG. 3B depicts an OLED located in a chamber which is defined by a multilayer barrier film according to one embodiment of the invention.

(6) FIG. 4 depicts an OLED encapsulated within a proximally sealed panel, the OLED being covered beneath a multilayer barrier film according to one embodiment of the invention.

(7) FIG. 5 depicts a simplified schematic diagram of an OLED panel containing an OLED encapsulated by a multilayer barrier film according to one embodiment of the invention.

(8) FIG. 6 depicts a simplified schematic diagram of a RGB color display OLED panel containing OLED layers sandwiched between multilayer barrier films according to one embodiment of the invention.

(9) FIG. 7 depicts a process scheme for encapsulating an OLED with a multilayer barrier film.

(10) FIG. 8 depicts the encapsulation of an OLED in accordance with the process scheme, based on a cross-sectional view of the layer-structure.

(11) FIG. 9A depicts a simplified set of process equipment required for encapsulating an electronic device and FIG. 9B depicts an apparatus for batch fabrication and encapsulation of an electronic device.

(12) FIG. 10A is a photograph (50× magnification) that depicts zinc oxide nanodots that can be used as starting material for generating, through ripening, zinc oxide nanorods that can be used in an ultraviolet light neutralizing layer of a multilayer barrier film of the invention. FIG. 10B shows zinc nanorods (10× magnification), and FIG. 10C shows zinc rods dense nanostructure (10× magnification).

(13) FIG. 11 depicts the transmittance of a barrier film of the invention that includes a UV neutralizing layer with only the seed layer of zinc oxide nanoparticles before the growth of the zinc oxide nanorods (black curve) and after the growth of the zinc oxide nanorods (grey curve) and an nanostructured layer that includes aluminum oxide nanoparticles as reactive nanoparticles capable of interacting with moisture and/or oxygen.

(14) FIGS. 12A-12F show manufacturing of an OLED encapsulated with a multilayer barrier film according to one embodiment of the invention. FIG. 12A shows an EL device encapsulated with a solvent protection layer on a glass or rigid substrate. FIG. 12B shows zinc oxide nanorods/nanoparticles grown as the active component in the UV light neutralizing layer on a plastic or rigid cover substrate. FIG. 12C shows zinc oxide nanoparticle dispersed acrylic polymer deposited on zinc oxide nanorods. FIG. 12D shows the cover substrate coated with UV filter and uncured reactive nanoparticle dispersed acrylic polymer. FIG. 12E shows the encapsulated OLED before and FIG. 12F shows the encapsulated OLED after curing of the barrier films.

(15) FIG. 13A depicts a schematic drawing of the bending test carried out with encapsulated OLED according to the invention. FIG. 13B is a photograph of the experimental set up for the bending test. FIG. 13C shows the results of the performance test of the encapsulated OLED.

(16) FIG. 14 shows an embodiment of a photovoltaic device comprising a multilayer barrier film of the invention.

(17) FIG. 15 shows a further embodiment of a photovoltaic device comprising a multilayer barrier film of the invention.

DETAILED DESCRIPTION

(18) FIG. 1 shows a simplified schematic diagram of an encapsulated device 100 according to one embodiment of the invention. The encapsulated device 100 comprises an OLED 110 covered by a multilayer barrier film 120 comprising a nanostructured layer 121 which contains nanoparticles capable of absorbing moisture and/or oxygen, and a neutralizing layer 122. The nanostructured layer may be formed from a nanoparticle dispersion that is cast onto the neutralizing layer. Exposure to a curing factor subsequently brings about the polymerization of the monomer. In order to prevent the curing factor from reaching the OLED, the neutralizing layer is deposited closer to the OLED than the nanostructured layer, so that the nanostructured layer is cured without damaging the OLED. Arrows 114 depict the curing factor penetrating the nanostructured layer containing the nanoparticles, thereby polymerizing the monomers to form the nanostructured layer. However, the curing factor is absorbed by the neutralizing layer and is prevented from reaching the OLED.

(19) FIG. 2A shows a magnified view of one embodiment of the multilayer barrier film according to the invention. Multilayer barrier film 120 comprises a distinct nanostructured layer 121 which contains nanoparticles dispersed therein. Adjacent to the nanostructured layer 121 is a neutralizing layer 122 that absorbs the curing factor. Although presently depicted as adjacent layers, the nanostructured layer 121 and the neutralizing layer 122 maybe spaced apart from each other by intervening layers without comprising the function of either layer. FIG. 2B shows an alternative layer arrangement in which the multilayer barrier film 120 comprises a nanostructured layer 121 that is spaced apart from the neutralizing layer 122 by an optical layer 123. The multilayer barrier film is arranged onto an OLED 110, with the neutralizing layer arranged nearest to the OLED 110. An adhesive layer 130 is disposed onto the multilayer barrier film 120 in order to tack a glass substrate 140 that serves to protect the OLED 110.

(20) FIG. 3A shows an encapsulated device 300 depicting a rigid standard glass-to-glass OLED panel in which OLED 110 is covered by a multilayer barrier film 120 and encased within a rim-sealed structure comprising base substrate 150, rim-sealing adhesive 130, and cover substrate 140. The multilayer barrier film 120 comprises nanostructured layer 121 sandwiched between neutralizing layer 122 and optical layer 123. The OLED 110 emits light through the multilayer barrier film 120 towards the transparent cover substrate 140. By covering the OLED 110 with the multilayer barrier film 120, any moisture and/or oxygen that permeates through any of the structural components of the encapsulated device 300 are prevented from reaching OLED by reactive nanoparticles present in the nanostructured layer 121. This embodiment is suitable for large OLED panels as the location of the adhesive 130 only at the edges of the device 300 minimizes the use of adhesive.

(21) FIG. 3B shows an embodiment which is similar to the encapsulated device 300 shown in FIG. 3A. In contrast to the embodiment shown in FIG. 3A, the OLED is located in a chamber 188, i.e. the OLED is not in direct contact with the multilayer barrier film. Also the multilayer barrier film does not comprise an optical layer between the UV neutralizing layer 122 and the nanostructured layer 121. However, it should be noted that an optical layer can still be included in the embodiment shown in FIG. 3B.

(22) FIG. 4 depicts an encapsulated device 400 depicting a flexible, thin film OLED display in which OLEDs 110 are covered by a multilayer barrier film 120 and encased within a proximally sealed structure comprising base substrate 150, adhesive 130 disposed proximally onto the OLEDs 110, and cover substrate 140 tacked to the adhesive 130. The multilayer barrier film comprises nanostructured layer 121 and an underlying neutralizing layer 122. Optical layer 160 is added to enhance the transmission of light from the OLEDs 110. In this embodiment, the multilayer barrier film 120 is fully in contact with the adhesive 130, thereby enabling the cover substrate to be more strongly tacked so as to minimize delamination.

(23) FIG. 5 is a schematic diagram depicting an implementation of the multilayer barrier film according to the invention in the context of an actual OLED panel, such as that shown in European Patent Application 0 776 147 A1. The OLED panel 500 with the encapsulated OLED 100 comprises OLED 110 formed on an ITO substrate 119, which is in turn adhered to a glass cover panel 140. The OLED 110 is protected from moisture through the application of multilayer barrier film 120 comprising an inner neutralizing layer, and an outer nanostructured layer comprising nanoparticles that are reactive towards moisture and/or oxygen. The OLED 110 is sealed off from the external environment by attaching a cover over the OLED 110, with adhesive applied to the edges of the cover to establish a rim-sealed structure. On the opposing side the encapsulated OLED is furthermore encased in a glass sealing case 128 attached to the ITO substrate via a rim-sealing adhesive 130. Light (illustrated by arrows 129) from the OLED 110 is emitted in the direction of the arrows 129.

(24) FIG. 6 is a schematic diagram depicting another implementation of the present invention in the context of a Red Green Blue (RGB) color OLED pixel. The encapsulated OLED pixel structure 600 comprises organic layers sandwiched between a transparent anode 119 and a metallic cathode 111. The organic layers comprise a hole-transport layer and hole-injection layer 117, an emissive layer 115 capable of emitting primary colors, and an electron-transport layer 113. When an appropriate voltage 170 is applied to the organic layers, the voltage give rise to charges which then combine in the emissive layer 115 to cause light 141 to be emitted. The multilayer barrier film 120A, 120B is situated on the metallic cathode 111 as well as on the transparent anode 119, respectively. On top of the multilayer barrier film 120A a base substrate 150 is provided while the multilayer barrier film 120B is terminated by a cover substrate 140, such as a transparent glass cover substrate.

(25) The general scheme of fabrication of the encapsulation barrier film according to the invention is shown in FIG. 7. A conventional polycarbonate or PET substrate is provided for forming the OLED. The substrate is first plasma treated to remove contaminants present on the surface of the substrate. After plasma treatment, the electronic device is formed on the substrate. In the case of OLED devices, the fabrication of the organic EL layers of the OLED can be carried out under vacuum conditions.

(26) Subsequently, the multilayer barrier film is formed over the OLED device. Formation of the multilayer barrier film comprises forming a neutralizing layer (such as by spin coating or by atomic deposition, and then forming over the neutralizing layer (either directly or indirectly) a nanostructured layer comprising moisture and oxygen reactive nanoparticles distributed within a polymer. Curing is subsequently carried out, after which a multilayer barrier film comprising the neutralizing layer and the nanostructured layer is formed. Secondary encapsulation structures, such as an adhesive layer along with a cover substrate, are then formed to further encapsulate the device.

(27) In another embodiment the multilayer barrier film is used to encapsulate a photovoltaic device, such as DSSC solar cell. Exemplary embodiments demonstrating the usage of the multilayer barrier film of the present invention for encapsulation of photovoltaic devices are illustrated in FIGS. 14 and 15. As can be seen in FIG. 14 the multilayer film is laminated over the photovoltaic device 221, such as a DSSC solar cell on the bottom as well as on the top of the solar cell. In contrast to the previous embodiments described, the first layer laminated on the solar cell element 221 shown in FIGS. 14 and 15 is the nanostructured layer 203 and not the UV neutralizing layer. In the embodiment shown in FIGS. 14 and 15 the nanostructured layer 203 is followed by the UV light neutralizing layer 202. Thus, it is noted here that both arrangements of these two layers are suitable in an encapsulation barrier film of the invention, meaning the UV neutralizing layer can be the “first layer” or the layer that contact the device to be encapsulated followed by the nanostructured layer arranged as “second layer” thereon, or alternatively, the nanostructured layer can be the contacting first layer with the UV neutralizing layer arranged thereon as the second layer.

(28) The multilayer film 203, 202 in the embodiment illustrated in FIG. 14 can be laminated by a barrier substrate 201 and another multilayer film or only an UV light neutralizing layer 200 as shown in FIG. 14. As shown in FIG. 15 it is however also possible to laminate the multilayer film 203, 202 only with a barrier substrate 201 without adding a further UV light neutralizing layer. However, such additional layers on top of the multilayer film 203 and 202 are optional such as the combination of layers 380 shown in FIG. 14. In another embodiment, such additional layers may be located only on one side of the encapsulated photovoltaic device.

(29) FIG. 14 also illustrates another potential function of the nanostructured layer 203, which is used in the embodiment illustrated in FIG. 14 as backing structure comprised of layers 214, 216 and 220 or only of layer 216. In the embodiment illustrated in FIG. 14, the backing structure is attached/connected to the nanostructured layer 203 via an adhesive 214 and 220. In another embodiment, the backing structured comprised only of the nanostructured layer is attached/connected to the nanostructured layer 203 via the nanostructured layer 216.

(30) The adhesive can, for example, be ethylene vinyl acetate resins, epoxy resins, polysulfide, silicone and polyurethane. Due to the adsorption capacity of the nanoscale particles in the nanostructured layer of the backing structure, the nanostructured layer 216 does not only protect the solar ceil against oxygen and moisture but also provides a cushion in case of electrolyte leaking from the solar cell. Even in case one solar cell is leaking the backing structure will soak up the electrolyte and protect the neighboring solar cell. On the other hand the backing structure forms a connection to the nanostructured layer 203. To connect the backing structure with the nanostructured layer 203 and adhesive 214, 220 can be used. In another embodiment, it is also possible to use 5 an adhesive layer which is located as thin film between the nanostructured layer 203 and the nanostructured layer 216. Thus, the adhesive layer would be located at both ends of the nanostructured layer 216 connecting it with the nanostructured layer 203.

(31) FIG. 15 illustrates a further embodiment in which the photovoltaic device is a dye-sensitized solar cell (DSSC). The basic setup of such a structure is the same as in FIG. 14. The only difference is that the backing structure shown in FIG. 15 comprises only of a nanostructured layer. The DSSC 221 in FIG. 15 comprises a titanium foil 440, the titanium oxide layer including the dye, the electrolyte 420 and the indium tin oxide (ITO) layer. The working principle and manufacture of a DSSC has already been explained further above and is also referred to in the article of So'mmeling, P. M., Spath, M. et al. (EPSEC-16 (European Photovoltaic Solar Energy Conference), Glasgow, 1-5 May 2000, Title: “Flexible Dye-Sensitized Nanocrystalline TiO.sub.2 Solar Cells”) and the master thesis of Janne Halme (Master thesis of Feb. 12, 2002, Title: Dye-sensitized nanostructured and organic photovoltaic cells: technical review and preliminary tests); Helsinki University of Technology, Department of Engineering Physics and Mathematics).

(32) The backing structure on the right and left side of the DSSC solar cell prevents or blocks the electrolyte 420 in case of leaking and thus protects the other solar cell. Use of a backing structure can provide improved barrier properties of rim sealing as compare to an adhesive wire. Also, in addition to an adhesive wire sometimes an additional layer is applied which is made of, e.g., ethylene-vinyl acetate (EVA) copolymers and adhesive heat seal laminations.

(33) In one embodiment, the backing structure may be comprised of a nanostructured layer and or chemical resistant monomer or polymer or ethylene vinyl acetate copolymers that can block electrolyte leakage. A nanostructured layer can block moisture and oxygen permeation into the device package. A nanostructure layer can also act as a chemical resistant material and may be used to block electrolyte leakage. In one embodiment, a backing structure can be manufactured of a nanostructured layer sandwiched between two adhesive layers (see FIG. 14) while in another embodiment the backing structure is manufactured only of a nanostructured layer (see FIG. 15).

(34) Specific examples will now be described to illustrate the fabrication process as described above as well as the barrier performance of fabricated encapsulation barrier films.

Example 1: Fabrication of an Encapsulated OLED

(35) 1. Surface Preparation of Substrates

(36) Silicon oxide coated soda-lime glass substrates (display-quality glass) were cut into 50 mm×50 mm pieces and also any required sizes for use as a base or cover for the OLEDs. The pneumatically operated hollow die punch-cutting equipment or any conventional slitting machine could be used to slice the samples into the specified or required dimensions.

(37) The water vapor permeation in the present encapsulation package may be mainly through the interface of the adhesive and substrate and also diffusion through adhesive sealing. The suitable surface pre-treatment process such as plasma treatment can eliminate the adhesion issues. Accordingly, they are rinsed with isopropyl alcohol (IPA) and blow-dried with nitrogen. These processes help to remove macro scale adsorbed particles on the surface. Acetone and methanol cleaning or rinsing is not recommended. After nitrogen blow-dry, the substrates are placed in the vacuum oven, with the pressure of 10.sup.−1 mbar, for degassing absorbed moisture or oxygen. The vacuum oven is equipped with fore line traps to prevent hydrocarbon oil back migrating from vacuum pump to the vacuum oven. Immediately after the degassing process, the barrier films are transferred to the plasma treatment chamber (e.g. ULVAC SOLCIET Cluster Tool). RF argon plasma is used to bombard the surface of the barrier film with low energy ions in order to remove surface contaminants. The base pressure in the chamber was maintained below 4×10.sup.−6 mbar. The argon flow rate is 70 sccm. The RF power is set at 200 W and an optimal treatment time usually 5 to 8 eight minutes is used depending on the surface condition.

(38) 2. OLED Fabrication

(39) The OLED architecture described in International Patent Application WO 03/047317 A1 has been adopted in the present example. ITO-coated glass with a sheet resistance of 20 Ω/square was used as a substrate for the OLED device fabrication. Wet chemical cleaning was undertaken with acetone and methanol and followed by dry oxygen plasma treatment. Poly (styrene sulfonate)-doped poly (3,4-ethylene dioxythiophene) (PEDOT) was used as a hole transport layer (HTL). The commercially available phenyl-substituted poly(p-phenylenevinylene) (PPV) yellow light emitting polymer was used. Small molecule based OLED structure was adopted in which 65 nm thick electroluminescence layer tris-(δ-hydroxyquinoline) aluminum (AlQ3) is deposited at 270° C. under high vacuum of 2×10.sup.−5 Pascal. A 5 Å (0.5 nm) thick LiF is deposited at 650° C. as an interlayer between organic electroluminescence (EL) panel and cathode. The aluminum cathode was deposited using thermal evaporation at a thickness of 200 nm.

(40) 3. Hafnium Oxide Neutralizing Layer Deposition

(41) The substrate along with the OLED are transferred under vacuum to an evaporation chamber, where a layer of hafnium oxide thin film is synthesized from tetrakis(dimethylamino) hafnium and (TDMAH) and ozone (O.sub.3) by atomic layer deposition (ALD) in accordance with the procedure described in D3.8.1, Mat. Res. Soc. Symp. Proc. Vol. 765, 2003 Materials Research Society. Other methods known in the art include electron-beam evaporation or sputtering.

(42) 4. Multilayer Barrier Film Proximal Encapsulation

(43) A nanostructured layer derived from a mixture of polymerizable acrylic acid containing a dispersion of aluminum oxide nanoparticles is spin coated onto the hafnium oxide covered OLED, and the acrylic acid monomer is cured through exposure to UV.

(44) HfO.sub.2 UV filter layer and optical layers can also be deposited by PVD methods including sputtering, thermal evaporation or electron beam evaporation, plasma polymerization, CVD, printing, spinning or any conventional coating processes including tip or dip coating.

(45) 5. Fabrication Equipment

(46) The fabrication process described above may be carried out either in an in-line system or a roll-to-roll system. An in-line fabrication system 570 is depicted in FIG. 9A. The system comprises serially connected sub-chambers used for carrying out the steps of cleaning the base substrate, forming the electronic component, forming the gas permeation sensor, and then carrying out the encapsulation of the device, each step being carried out within separate sub-chambers. For instance, in the case of an OLED, the formation of OLED anode, organic EL layer, and cathode may be carried out in sub-chambers 571, 572 and 573, respectively, and gas permeation sensor is carried out in sub-chamber 574. Plasma cleaning and encapsulation may be carried out in a sub-chamber 575. The base substrate, carrying both sensor and electronic component, may finally be transported by a loadlock 578 into the sub-chamber 575, which may be a glove box, for example.

(47) In one exemplary embodiment, sub-chamber 575 may be a lab-scale glove box 500 for carrying out gas permeation sensor batch fabrication and encapsulation as shown in FIG. 9B. In this example, the vacuum chamber 502 has dimensions of 400 5 mm×500 mm×650 mm, is connected to the high vacuum pumping station 504 (preferably mechanical booster with combination of rotary vacuum pump) and is maintained at a base pressure 10.sup.−4 mbar. The high vacuum Pirani gauge 506 is used to monitor the vacuum pressure. The isolation valve 508 is used for isolating the vacuum pumping station 504 and the vacuum chamber 502. The linear motion drive 510 is used for sealing the adhesive pad 512 onto the OLED device 514 under vacuum. The linear motion drive 510 is mounted through a KF25 flange connection 516 to the vacuum chamber and it is pneumatically operated to drive the linear motion system.

(48) Pneumatic linear motion feedthrough provides action for linear motion by applying a suitable compressed air pressure in the range of 40 to 80 psi (275.79 kPa to 551.58 kPa). The compressed air is admitted through the inlet 518 and outlet 520 of the pneumatic actuator. Linear travel can be shortened or lengthened by turning the adjustment knob located at the top end of the pneumatic actuator 522. Once adjusted, the jam nut 524 locks the adjustment knob 526 in place. Linear travel adjustment can be made up to the required travel distance. A suitable adhesive holding jig 528 is connected to the linear motion drive 510 for holding the adhesive pad 512 used for sealing the device. The linear drive's axial load is typically 20 lb (about 9.07 kg). The holding jig 528 is also used to apply pressure while the adhesive sealing process is undertaken. The pressure typically applied is in the range of 40 to 80 psi (275.79 kPa to 551.58 kPa) and the required pressure is tailored to the type of substrate/device used. The pressure can be applied either on the rim or the entire face of the substrate. The different types of holding jigs can be used as per the requirement of packaging. They are constructed of high grade vacuum compatible materials. The use of welded stainless steel bellows and linear bearing shaft support provide reliability and smooth operation. Pneumatic feedthroughs can be chosen from industry standard components, such as, either conflat compatible Del-Seal CF metal seal flanges or ISO KF Kwik-Flange elastomer seal port mounts.

(49) The smooth operation of the linear motion drive, holding jig movements, and alignments with the substrates are carefully controlled by the supporting frame 530 and linear ball guides 532. The holding jig is designed such that the adhesive can be loaded onto the jig through a load-lock 534 of the vacuum chamber. Similarly, the device or substrate can be transferred to the substrate holder through of load-lock for the secondary sealing process.

(50) The vacuum chamber 502 is further equipped with a plasma source 536 for surface pre-treatment or cleaning before the adhesive bonding process. The radiofrequency (RF) power controller 538 is used for controlling the RF power of the plasma source. Surface preparation consists of cleaning or surface modification done to the as-received sample or devices in order to obtain desired and reproducible properties. In the case of a polymer substrate, there are many avenues for surface contamination on the barrier film surface and also the polymer base substrate tends to absorb water vapor due to long storage time and from handling and exposure to ambient conditions. Any surface contamination would certainly affect adhesion of the adhesive pad. Radiofrequency (RF) argon plasma is used to bombard the surface of the substrate or primary sealed device with low energy ions in order to remove surface contamination. The base pressure in the chamber is maintained below 4×10.sup.−6 mbar and is monitored by a pressure monitor 550. The argon flow rate is 70 sccm. The radiofrequency (RF) power is set at 200 W and an optimal treatment time is normally 5 to 8 eight minutes depending on the surface condition. The argon gas line 551 is connected to the vacuum chamber to introduce argon used for plasma treatment. The nitrogen gas line 552 is connected to the vacuum chamber for venting the chamber after the plasma treatment process.

(51) The substrate heating table 540 can provide up to 100° C. and the temperature controller is used to maintain required temperature. The heating process to melt the adhesive during vacuum bonding the device. After the vacuum sealing process, the adhesive can be cured by exposure to UV light for 30 seconds. A 400 W metal halide light UV source 542 (model 2000-EC) is used to cure the adhesive. Wavelengths of 365 nm & 300 nm with the respective intensities of 85 mW/cm.sup.2 and 22 mW/cm.sup.2 may be used to cure the adhesive.

(52) The sequence of fabrication can be chosen flexibly according to the encapsulation design, the type of OLED architecture, substrates and can be used not only for batch and in-line fabrication systems shown herein, but can also be adapted to roll-to-roll processes as well.

Example 2: Encapsulation Vacuum Transfer Technique

(53) The fabrication of the barrier film and the subsequent device encapsulation will be illustrated in the following for highly moisture or oxygen sensitive (up to a water permeation rate of 10.sup.−6 g/m.sup.2/day level), organic devices fabricated on to rigid or plastic substrates, using either an on batch or roll to roll process: 1. Device 110—Organic Light Emitting Diode 2. Solvent protection layer—High refractive index solvent protection optical film (optional) 3. Neutralizing layer—Titanium oxide/Zinc Oxide rod structured acrylic polymer 4. Nanostructured layer—Reactive nanoparticles (other than titanium oxide or zinc oxide, respectively) dispersed in acrylic polymer 5. Cover substrate—Barrier Plastic substrate/glass substrate

(54) The device with the multi-layer barrier film of the invention that includes layers 3 and 4 will be adopted if cover substrates are fabricated on to plain plastic substrates. The solvent protection layer (film) 2 is only used optionally for protecting the device as a first layer; it is not involved in the multi-layer barrier structure.

(55) Deposition of solvent protection layer on to EL device (organic electroluminescent (EL) panel) FIG. 12A shows an EL device encapsulated with solvent protection layer 2 on to glass or rigid substrate 5 before encapsulation of the device 110 with a multilayer barrier film of the invention (that includes the UV neutralizing layer and the nanostructured layer containing reactive nanoparticles capable of interacting with moisture and/or oxygen).

(56) After OLED fabrication, the solvent protection layer 2, magnesium oxide is in a first step deposited by thermal evaporation method on to the organic EL device (organic electroluminescent (EL) panel). This layer helps to prevent the residual solvent permeation or reaction with organic electronic devices such as organic light emitting diodes. Some of the electronic devices such as inorganic electroluminescence devices or inorganic photovoltaic (PV) devices may not require this solvent protection layer. This magnesium oxide or magnesium fluoride layer 2 does not contribute at all or—not significantly to the improvement of the overall barrier properties. The solvent protection layer 2 can, for example, be HfOx, MgO, MgF, BaO, BaF, and LiF or any suitable optical inorganic films with either high refractive or low refractive index optical properties. A high refractive index optical film can be preferred in the event that top emitting OLEDs and photovoltaics devices are encapsulated.

(57) The fabrication of the layers of the barrier film of the invention can be carried out as follows, using, for illustration purposes, the fabrication of multi-layer encapsulation layers on to plastic substrate 5.

(58) As shown in FIG. 12B zinc oxide nanorods/nanoparticles 3 are grown as the 5 active component in the UV light neutralizing layer 122 on to a plastic or rigid cover substrate 5 as follows.

(59) B1—Zinc Oxide Nanorods 3 (or Titanium Oxide Particles) Deposited on to the Cover Rigid or Plastic Substrate 5.

(60) In a first step of generating the UV light neutralizing layer, commercially available nanoparticle dispersions of zinc oxide, or titanium oxide dispersed in hexane diol diacrylate or isobornyl acrylate or tripropylene glycol diacrylate can be used to deposit nanodots (20 to 50 nm) first on to rigid substrate or a flexible plastic substrate by any conventional coatings method such as spin coating, screen printing, ink jet printing or any imprinting methods or roll to roll coating methods such as tip coating, WebFlight, Slot die coatings etc. After the deposition, the solvent can be removed at thermal annealing at 80° C. for few minutes can take place. A solvent thermal route is used to grow zinc oxide nanorods by exposing the substrate 5 to zinc acetate and ammonium hydroxide solution. Zinc oxide nanodots (FIG. 10A) will ripen to nanorod morphologies (FIG. 10B and FIG. 10C) at temperatures of 60° C. to 120° C. within a time of 10 min to 60 min. Use of nanodots as nuclei is one of the approaches that will allow for controlled growth of higher aspect ratio nanorods. Several solvent thermal routes and hydrolysis processes exist that can be employed to grow the zinc nanorods 3 on to the plastic substrates 5. The atomic force microscope (AFM) photographs of nanodots and nanostructures are shown in FIG. 10A to FIG. 10C). These nanorods can be deposited either on barrier coated plastic or any rigid substrate like glass. These nanorods can be used alone in the UV neutralising layer 122 due to their property to scatter the light. It is however also possible to add zinc oxide particles to this film in order to improve the UV filter properties. The structure of a UV neutralizing layer containing Zinc oxide nanoparticles (depicted as small black squares 4 in the layer 122) dispersed in acrylic polymer and deposited onto Zinc oxide nanorods (depicted as “star-like” grey structures 3) is shown in the following.

(61) B2—Zinc Oxide Nanoparticle Dispersed Acrylic Polymer Deposited on to Zinc Oxide Nanorods (FIG. 12C).

(62) For incorporating the zinc oxide nanoparticles into the UV light neutralizing layer, 40 ml of UV curable acrylate monomer with a coating weight of about 100% of the sealing solution was added to 5 ml of a dispersion of zinc oxide in tripropylene glycol diacrylate (35% weight), obtainable from Nanodur of Nanophase Technologies. 15 ml of an organic solvent of PGME and EG (1:1) ratio was added to the mixture. Sonification of the mixture was then carried out for about 1 hour prior to deposition onto a barrier oxide layer. The formation of the film that includes both the nanorods and the nanoparticles via spin coating was undertaken in a nitrogen atmosphere in a glove box. The oxygen and water vapor contents were reduced to less than 1 ppm level in the glove box. This layer was then cured via UV before applying the film that contains the reactive nanoparticles. Alternatively, it is also possible to cure of this layer after deposition the nanostructured layer that contains the reactive nanoparticles as explained in the following.

(63) For the generation of the nanostructured layer containing the reactive nanoparticles capable of interacting with moisture and/oxygen, commercially available nanoparticles (NanoDur 99.5% aluminium oxide particles from Nanophase Technologies) were pre-treated with plasma and added to an organic solvent such as 2-methoxyethanol (2MOE) and ethylene glycol (EG) for dispersion in the ratio of 1:1 2MOE to EG. Propylene glycol monomethyl ether or Ethyl Acetate or Methyl Isobutyl Ketone, Methyl Ethyl, 2 MOE or any mixture of solvents or wetting additive agents can also be used instead. Alternatively, commercially available nanoparticle dispersions such as zinc oxide, or titanium oxide dispersed in hexane diol diacrylate, isobornyl acrylate, tripropylene glycol diacrylate can, for example, also be used.

(64) A compound with polymerizable groups such as commercially available UV curable acrylate monomers (such as HC-5607 obtainable from Addison Clear Wave, Wooddale, Ill., USA, for example) was added to the nanoparticle mixture to form a sealing solution. The polymer coating weight may be between an amount of 5% to 70% by weight of the entire sealing solution. For example, the total concentration of nanoparticles in the polymer may be at 66% by weight of the sealing solution, while polymer coating weight is at about 34% by weight of the sealing solution.

(65) The synthesis was undertaken under inert gas environment. The set of experiments were carried out with different mixtures of nanoparticles in acrylic polymer solutions and spin coated onto the plain polymer substrate.

(66) Deposition of reactive aluminum oxide nanoparticles dispersed acrylic polymer (Hard coat).

(67) B3—the Cover Substrate Coated with UV Filter and Uncured Reactive Nanoparticle Dispersed Acrylic Polymer 6 (FIG. 12D).

(68) For the deposition of the reactive nanoparticles (and thus formation of the respective film) of the UV neutralizing layer) 40 ml of UV curable acrylate monomer with a coating weight of about 1000% of the sealing solution was added to 15 ml of a dispersion of aluminum oxide in tripropylene glycol diacrylate (35% weight), obtainable from BYK Chemicals. 15 ml of an organic solvent of PGME and EG (1:1) ratio was added to the mixture. Sonification of the mixture was then carried out for about 1 hour prior to deposition onto a barrier oxide layer. The formation of the sealing layer via spin coating was undertaken in a nitrogen atmosphere in a glove box. The oxygen and water vapor contents were reduced to less than 1 ppm level in the glove box.

(69) When testing the UV filter properties of a barrier film that contained the zinc nanorods in the UV light neutralizing layer and aluminum nanoparticles in the nanostructured film with a barrier film that only contained the initial seed layer of the zinc oxide particles in the UV light neutralizing layer, it was seen the UV filter properties of the zinc nanorods containing film was significantly higher (FIGS. 12E & F). In this context it is noted that the zinc nanorods can efficiently scatter the light, which enables the UV neutralizing layer to efficiently extract the light from device of interest, for example, an organic top emitting device.

(70) Coating Transfer Process by Vacuum Sealing or Lamination Process

(71) The cover substrate (B3) coated with the UV light neutralizing layer and the uncured nanostructured barrier layer is then sealed onto an organic device by vacuum sealing method ad then cured with UV radiation. Thereby an encapsulated electronic device such as an OLED, as illustrated in FIG. 13 is fabricated.

(72) Flexible OLED Encapsulation—Fabrication of Prototype and Performance Testing of OLED Encapsulated with Barrier Film of the Invention

(73) Either glass or polycarbonate substrates are transparent and can be cut into preferred dimensions. Pneumatically operated hollow die punch-cutting equipment or any conventional slitting machine can be used to slit the polycarbonate substrates into the specified or required dimensions.

(74) In the experimental setup, the substrates were rinsed with isopropyl alcohol (IPA) and blow-dried with nitrogen to remove macro-scale adsorbed particles on the surface. After nitrogen blow-dry, the substrates were placed in the vacuum oven at a pressure of 10.sup.−1 mbar (0.04 Pa) for degassing absorbed moisture or oxygen. Immediately after the degassing process, the substrates were transferred to the plasma treatment chamber (e.g. ULVAC SOLCIET Cluster Tool). RF argon plasma was used to bombard the surface of the barrier film with low energy ions in order to remove surface contaminants. The base pressure in the chamber was maintained below 4×10.sup.−6 mbar. The argon flow rate was 70 seem (seem=cubic centimeters per minute at standard temperature and pressure) (0.1 Pa*m.sup.3/s). The RF power was set at 200 W and an optimal treatment time usually 5 to 8 eight minutes is used depending on the surface condition. Poly (styrene sulfonate)-doped poly (3,4-ethylene dioxythiophene) (PEDOT) was used as a hole transport layer (HTL). The commercial phenyl-substituted poly (p-phenylenevinylene) (PPV) yellow light emitting polymer was used. A 20 nm thick calcium film covered with a 200 nm thick silver cathode was deposited by thermal evaporation in an ULVAC cluster system at a base pressure of 2.0×10.sup.−6 Torr (0.0002666 Pa). The silver film was used to protect the underlying calcium. Also a small molecule based OLED structure was fabricated for the some of the encapsulation studies. In this fabrication process, ITO-coated glass with a sheet resistance of 20 Ω/square was used as a substrate for the OLED device fabrication. 75 nm NPB was deposited in high vacuum 2×10-5 Pa at 270° C. Then, 65 nm thick electroluminescence layer Alq3 was deposited at 270° C. under high vacuum of 2×10.sup.−5 Pa pressure. LiF was deposited at 650° C. as an interlayer between EL and cathode. The cathode (200 nm aluminum) was deposited using thermal evaporation technique.

(75) The standard small molecule based standard OLED device fabrication process was followed using 5 cm by 5 cm of the plastic substrate coated with barrier silicon oxide and ITO films and encapsulated with magnesium oxide thin film with 250 μm as solvent protection layer.

(76) A zinc oxide nanoparticles containing polymer layer as described above was deposited onto the cover plastic substrate and used as UV light neutralizing layer (UV filter). In addition, also a nanostructured polymer layer containing aluminum oxide nanoparticles was deposited onto the UV filter. Before curing, the cover substrate was vacuum sealed on to the OLED device.

(77) The flexibility of an organic light emitting device is limited to a great extent by the de-lamination nanostructure layer, indium tin oxide and interfacial effects of active polymer and hole and electron injection layers.

(78) The flexible encapsulated OLED device according to the invention was subjected to different cycles of flexing as per American Society of Testing Materials Standard (radius of curvature: 30 mm, frequency: 50 Hz and the thickness of display <400 mm). The flexing test chosen were 5000, 10000, 20000 & 30000 cycles. The substrate was 5 cm by 5 cm as shown in FIG. 13a (cf. also FIG. 13B), the flexing radius of curvature R was 37.6 mm and deflection h was 18 mm as shown in FIG. 13A. Before and after each bending test the device luminescence was measured against voltage. FIG. 13C shows the luminescence against bending cycle's characteristics of flexed device performances with different bending cycles. The turn on voltage is 5V for flexed devices with 5 k bending cycles and the luminescence has reached up to 100 Cd/m.sup.2. There was no interfacial failure between encapsulation and OLED, base and cover substrates. However, when the bending cycles increased beyond 10,000 cycles, the luminescence dropped to 80 Cd/m.sup.2. The cover substrate bonding with nanostructured layer and UV filter was however still maintained. It was observed that the bonding between the solvent protection layer and OLED was still good and there no delamination occurred. In contrast thereto, the delamination in between the solvent protection layer and OLED occurred after the 30,000 bending cycles. This results show that vacuum sealing method resulted in a strong attachment of the barrier film of the invention to the OLED and vacuum sealing was able resolve the problems related to the bubbles formation and other defects due to the manual sealing methodologies.

(79) Encapsulation of a Photovoltaic Device

(80) In the following section an example of encapsulation of a photovoltaic device is described in more detail.

(81) Encapsulation of a photovoltaic device as shown in FIG. 14 starts from the bottom of the device shown in FIG. 14. When the optional combination of layers 380 is not included, at first a base substrate (not shown) such as poly(ethylene-2,6-naphthalene dicarboxylate) (PEN), polyethylene terephthalate) (PET), poly(4-methyl-2-pentyne), polyimide, polycarbonate (PC) is provided which is then coated with the UV neutralizing layer 202 followed by the nanostructured layer 203. The barrier properties of this multilayer can be between about 10.sup.−1 g/m.sup.2/day to about 10.sup.−6 g/m.sup.2/day at 39° C. & 90% relative humidity (RH).

(82) The UV neutralizing layer 202 and the nanostructured layer 203 can be coated on the substrate layer by deposition methods known in the art, such as spin coating, slot die coating, vacuum evaporation or screen printing, to name only a few. These layers can be cured by either heat curing or UV curing methods known in the art. It is also possible to coat the substrate layer on both sides with a UV neutralizing layer 202 to obtain a protection of the substrate layer, too.

(83) The thickness of the UV neutralizing layer 202 and the nanostructured layer 203 can be between about 20 nm to about 1 μm or between about 500 nm and 1 μm. In general the thickness of the UV neutralizing layer 202 and the nanostructured layer 203 depends on the thickness of the encapsulated photovoltaic device 221. The ratio between the thickness of the photovoltaic device 221 and the neutralizing layer 202 and the nanostructured layer 203, respectively, is about 1:2. For example, a photovoltaic device 221 with a thickness of 1 μm results in a thickness of each of the UV neutralizing layer 202 and the nanostructured layer 203 of 2 μm.

(84) The substrate layer coated with the UV neutralizing layer 202 and the nanostructured layer 203 is then laminated to the bottom of the photovoltaic device 221. Preparation of the layered structure on the other side of the photovoltaic device is carried out in the same way as at the bottom of the photovoltaic device 221.

(85) However, before encapsulating the photovoltaic device 221 between layers 203 and 202 coated onto the substrate, the backing structure (also called sealing layer) is applied at the side of a photovoltaic device 221. In one embodiment, the backing structure consists of a nanostructured layer and/or adhesive layer and can be applied via standard printing methods (for more details regarding the formation of the backing structure see the following paragraphs). The width of the backing structure can be between about 1 μm to about 5 mm.

(86) The adhesive layer(s) can be applied using a slot die coating process.

(87) FIG. 15 shows a specific embodiment of the structure in FIG. 14 in which the encapsulated photovoltaic device is a Dye-sensitized solar cell (DSSC). The DSSC consists of a indium tin oxide layer 410, an electrolyte layer 420, a titanium oxide+dye layer 430 and a titanium foil layer 440.

(88) For encapsulation of the DSSC with the multilayer barrier film as shown in FIG. 15, the DSSC is formed directly on the multilayer barrier film. At first, the titanium foil 440 is laminated onto the nanostructured layer 203. On top of the titanium foil, the titanium oxide paste is sputtered. To obtain the final titanium oxide/dye layer 430, titanium oxide paste is emerged in a solution of organic dye for a certain period of time.

(89) Sputtering of the titanium oxide paste onto the titanium foil leaves a protrusion in the layer 430 in shape of a crescent. After emerging and drying of the electrode the electrolyte is filled into this protrusion. The electrolyte layer 420 and the nanostructured layer forming the backing structure are created at the same time, for example by any standard printing method known in the art. The backing structure is cured by applying UV light only at the point where the backing structure is located.

(90) Following formation of the electrolyte layer 420 and the backing structure, the ITO layer 410 is laminated on top of the electrolyte layer 420.