Abstract:
An apparatus and method for liquid-phase coating of layers onto a substrate of an electronic device. Electo-form nozzles containing a body and disc are arranged in an array to perform multiple depositions on the substrate. A low solids mixture produces a very thin dried film of electronic materials.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority under 35 U.S.C. §119(e) from Provisional Application No. 61/140,945 filed Dec. 27, 2008 which is incorporated by reference in its entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    This disclosure relates in general to a process for making an electronic device. In particular, it relates to a method and nozzle apparatus for continuous coating liquid-phase layers using a specific nozzle assembly for liquid mixtures having low solids content. 
       BACKGROUND INFORMATION 
       [0003]    Increasingly, active organic molecules are used in electronic devices. These active organic molecules have electronic or electro-radiative properties including electroluminescence. Electronic devices that incorporate organic active materials may be used to convert electrical energy into radiation and may include a light-emitting diode, light-emitting diode display, or diode laser. 
         [0004]    Two methods are commonly used to prepare organic light-emitting diode (“OLED”) displays: vacuum deposition, and liquid-phase processing. (The latter includes all forms of applying the layers from a fluid, as a true solution or a suspension.) Vacuum deposition equipment typically has very high investment costs, and inferior material utilization (high operating costs), so liquid-phase processing is preferred, especially for large area displays. 
         [0005]    Liquid-phase processing for the deposition of organic active layers includes any number of technologies for control of layer thickness on a substrate. Some of these technologies include self regulated methods to control thickness, including spin coating, rod coating, dip coating, roll coating, gravure coating or printing, lithographic or flexographic printing, screen coating or printing, etc. Other of these technologies seek to control deposition thickness using controlled deposition techniques including ink jet printing, spray coating, nozzle coating, slot die coating, curtain coating, bar or slide coating, etc. 
         [0006]    Self regulated techniques suffer a number of drawbacks. Fluids used in coating OLED displays are often applied over surfaces with topography—electrodes, contact pads, thin film transistors, pixel wells formed from photoresists, cathode separator structures, etc. The uniformity of the wet layer deposited by a self regulated technique depends on the coating gap and resulting pressure distribution, so variations in the substrate topography result in undesirable variations in the wet coating thickness. Self regulated techniques generally suffer higher operating costs in that not all the fluid presented to the substrate is deposited. Some fluid is either recycled in the fluid bath (e.g., dip coating), or on the applicator (e.g., roll or gravure coating), or, it is wasted (e.g., spin coating). Solvent evaporates from the recycled fluid, requiring adjustment to maintain process stability. Wasting material, and recycling and adjusting material, adds cost. 
         [0007]    Controlled techniques can provide lower operating costs. However, in some cases, the wear on precision equipment, such as nozzles, leads to poor control over layers which are only nanometers thick when dry. A precision machined nozzle is expensive to produce, and providing an array of nozzles to cover a larger substrate area will magnify the control problems. Inconsistent formation of organic layers typically leads to poor device performance and poor yield in device fabricating processes. 
         [0008]    There continues to be a need for improved processes for the liquid-phase deposition of organic materials for OLED applications. 
       SUMMARY OF THE DISCLOSURE 
       [0009]    In a controlled coating method all the fluid supplied to the coating nozzle is applied to the substrate or workpiece. The average wet coating thickness can be calculated a priori from the volumetric flow rate of the coating fluid, the coated width, and the speed at which the substrate moves past the nozzle. Fluid properties (e.g., viscosity, surface tension) and external forces (e.g., gravity) may affect the quality of the coating, but they do not affect the average wet thickness. Of particular interest of the controlled coating methods is the continuous nozzle coating method, in particular, an electro-form process having a disc bonded to a recess in the distal end of a nozzle body. 
         [0010]    Continuous nozzle operation has many variations, including design of the nozzle itself, “patch coating” versus “continuous coating”, “stripe coating”, and the methods of generating the pressure which forces liquid out of the nozzle. Continuous nozzle coating is generally recognized to be coating with a nozzle separated by gap from a substrate or workpiece. 
         [0011]    Typical thickness levels associated with nozzle are on the order of tenths of microns when wet, and can dry to final films on the order of a few microns. In contrast, continuous nozzle coating of organic layers for fabricating OLED displays produces layers generally from about 0.1 to 500 nanometers thick. Process improvements are required to produce acceptable layer performance at such thin dimensions. 
         [0012]    Degradation of the stream, also called pillar, emanating from the nozzle leads to unacceptable deposition and performance of the organic materials in the dried layer. When used in an arrangement of nozzles, the degradation of just one nozzle stream in an arrangement of 16 nozzles can lead to unacceptable product losses, as a multitude of devices are coated during operation of the arrangement. In one embodiment of the present disclosure, an electro-formed disc can be attached to a nozzle body to facilitate easy change out of discs when the stream has degraded beyond acceptable parameters. Instead of replacing the entire nozzle assembly, only the disc at the terminus of the nozzle need be replaced. 
         [0013]    At least one embodiment includes a nozzle assembly comprises a body containing a recessed area at the distal end of the body and a disc having a centrally located aperture. This aperture has an aperture diameter d A , the disc having a diameter d D . In addition, the disc is characterized as having a first side and a second side, wherein the first side is attached to the recessed area of the body, and the second side having the aperture located within a recessed area. This recessed area on the second side of the disc has a diameter d 2 , wherein d D  is greater than d 2 . 
         [0014]    In one embodiment the diameter of the aperture, d A , is less than or equal to 0.05 mm. In another embodiment d A  is less than or equal to 0.01 mm. In still another embodiment, d A  varies between the first side of the disc and the second side of the disc. In another embodiment d A  is larger at the first side than the second side. In another embodiment a radius r A  defines a surface of the aperture between the first and second sides. In one embodiment the radius is less than 0.05 mm. In another embodiment the radius r A  is less than 0.04 mm. In another embodiment the radius r A  is less than 0.03 mm. 
         [0015]    At least one embodiment includes a liquid-phase coating process comprising several steps, such as providing a body containing a recessed area at the distal end of the body. Providing a disc having a centrally located aperture, the aperture having an aperture diameter d A , and the disc having a diameter d D , a first side and a second side. The second side of the disc has the aperture located within a recessed area having a diameter d 2 , wherein the disc diameter d D  is greater than d 2 . The first side of the disc is attached to the recessed area of the body to form a nozzle assembly, and a mixture containing a liquid and a solid is provided. This mixture is directed through the nozzle assembly to produce a layer. In one embodiment the liquid is an organic solvent. In another embodiment the liquid is water. In one embodiment the mixture is a solution having less than 10% solids content, and in another embodiment the mixture is a suspension having less than 10% solids content. 
         [0016]    In one embodiment, the workpiece comprises a substrate (such as glass) useful for an organic electronic device. The term “organic electronic device” or sometimes just “electronic device,” is intended to mean a device including one or more organic semiconductor layers or materials. An organic electronic device includes, but is not limited to: (1) a device that converts electrical energy into radiation (e.g., a light-emitting diode, light emitting diode display, diode laser, or lighting panel), (2) a device that detects a signal using an electronic process (e.g., a photodetector, a photoconductive cell, a photoresistor, a photoswitch, a phototransistor, a phototube, an infrared (“IR”) detector, or a biosensors), (3) a device that converts radiation into electrical energy (e.g., a photovoltaic device or solar cell), and (4) a device that includes one or more electronic components that include one or more organic semiconductor layers (e.g., a transistor or diode), or any combination of devices in items (1) through (4). 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0017]      FIG. 1  is an illustration of an electronic device. 
           [0018]      FIG. 2  is an illustration of one embodiment of a disc with a centrally located aperture of the present disclosure. 
           [0019]      FIG. 3  is an illustration of an edge view taken along line  3 - 3  of the disc of  FIG. 2  of the present disclosure. 
           [0020]      FIG. 4  is an illustration of one embodiment of a recessed area at the distal end of a nozzle body of the present disclosure. 
           [0021]      FIG. 5  is an illustration of one embodiment of a nozzle arrangement of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    One example of an electronic device comprising an organic light-emitting diode (“OLED”) is shown in  FIG. 1  and designated  100 . The device has an anode layer  110 , a buffer layer  120 , a photoactive layer  130 , and a cathode layer  150 . Adjacent to the cathode layer  150  is an optional electron-injection/transport layer  140 . Between the buffer layer  120  and the photoactive layer  130 , is an optional hole-injection/transport layer (not shown). 
         [0023]    As used herein, the term “buffer layer” or “buffer material” is intended to mean electrically conductive or semiconductive materials and may have one or more functions in an organic electronic device, including but not limited to, planarization of the underlying layer, charge transport and/or charge injection properties, scavenging of impurities such as oxygen or metal ions, and other aspects to facilitate or to improve the performance of the organic electronic device. Buffer materials may be polymers, oligomers, or small molecules, and may be in the form of solutions, dispersions, suspensions, emulsions, colloidal mixtures, or other compositions. The term “hole transport” when referring to a layer, material, member, or structure, is intended to mean such layer, material, member, or structure facilitates migration of positive charges through the thickness of such layer, material, member, or structure with relative efficiency and small loss of charge. The term “electron transport” when referring to a layer, material, member or structure, is intended to mean such a layer, material, member or structure that promotes or facilitates migration of negative charges through such a layer, material, member or structure into another layer, material, member or structure. The term “hole injection” when referring to a layer, material, member, or structure, is intended to mean such layer, material, member, or structure facilitates injection and migration of positive charges through the thickness of such layer, material, member, or structure with relative efficiency and small loss of charge. The term “electron injection” when referring to a layer, material, member, or structure, is intended to mean such layer, material, member, or structure facilitates injection and migration of negative charges through the thickness of such layer, material, member, or structure with relative efficiency and small loss of charge. 
         [0024]    The device may include a support or substrate (not shown) that can be adjacent to the anode layer  110  or the cathode layer  150 . Most frequently, the support is adjacent the anode layer  110 . The support can be flexible or rigid, organic or inorganic. Generally, glass or flexible organic films are used as a support. The anode layer  110  is an electrode that is more efficient for injecting holes compared to the cathode layer  150 . The anode can include materials containing a metal, mixed metal, alloy, metal oxide or mixed oxide. Suitable materials include the mixed oxides of the Group 2 elements (i.e., Be, Mg, Ca, Sr, Ba, Ra), the Group 11 elements, the elements in Groups 4, 5, and 6, and the Group 8-10 transition elements. If the anode layer  110  is to be light transmitting, mixed oxides of Groups 12, 13 and 14 elements, such as indium-tin-oxide, may be used. As used herein, the phrase “mixed oxide” refers to oxides having two or more different cations selected from the Group 2 elements or the Groups 12, 13, or 14 elements. Some non-limiting, specific examples of materials for anode layer  110  include, but are not limited to, indium-tin-oxide (“ITO”), aluminum-tin-oxide, gold, silver, copper, and nickel. The anode may also comprise an organic material such as polyaniline, polythiophene, or polypyrrole. The IUPAC number system is used throughout, where the groups from the Periodic Table are numbered from left to right as 1-18 (CRC Handbook of Chemistry and Physics, 81 st  Edition, 2000). 
         [0025]    In one embodiment, the buffer layer  120  comprises hole transport materials. Examples of hole transport materials for layer  120  have been summarized for example, in Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition, Vol. 18, p. 837-860, 1996, by Y. Wang. Both hole transporting molecules and polymers can be used. Commonly used hole transporting molecules include, but are not limited to: 4,4′,4″-tris(N,N-diphenyl-amino)-triphenylamine (TDATA); 4,4′,4″-tris(N- 3 -methylphenyl-N-phenyl-amino)-triphenylamine (MTDATA); N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine (TPD); 1,1-bis[(di-4-tolylamino) phenyl]cyclohexane (TAPC); N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)[1,1′-(3,3′-dimethyl)biphenyl]-4,4′-diamine (ETPD); tetrakis-(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA); α-phenyl-4-N,N-diphenylaminostyrene (TPS); p-(diethylamino)benzaldehyde diphenylhydrazone (DEH); triphenylamine (TPA); bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP); 1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl] pyrazoline (PPR or DEASP); 1,2-trans-bis(9H-carbazol-9-yl)cyclobutane (DCZB); N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB); N,N′-bis(naphthalen-1-yl)-N,N′-bis-(phenyl)benzidine (α-NPB); and porphyrinic compounds, such as copper phthalocyanine. Commonly used hole transporting polymers include, but are not limited to, poly(9,9,-dioctyl-fluorene-co-N-(4-butylphenyl)diphenylamine), and the like, polyvinylcarbazole, (phenylmethyl)polysilane, poly(dioxythiophenes), polyanilines, and polypyrroles. It is also possible to obtain hole transporting polymers by doping hole transporting molecules such as those mentioned above into polymers such as polystyrene and polycarbonate. 
         [0026]    The photoactive layer  130  may typically be any organic electroluminescent (“EL”) material, including, but not limited to, small molecule organic fluorescent compounds, fluorescent and phosphorescent metal complexes, conjugated polymers, and mixtures thereof. Examples of fluorescent compounds include, but are not limited to, pyrene, perylene, rubrene, coumarin, derivatives thereof, and mixtures thereof. Examples of metal complexes include, but are not limited to, metal chelated oxinoid compounds, such as tris(8-hydroxyquinolato)aluminum (Alq3); cyclometalated iridium and platinum electroluminescent compounds, such as complexes of iridium with phenylpyridine, phenylquinoline, or phenylpyrimidine ligands as disclosed in Petrov et al., U.S. Pat. No. 6,670,645 and Published PCT Applications WO 03/063555 and WO 2004/016710, and organometallic complexes described in, for example, Published PCT Applications WO 03/008424, WO 03/091688, and WO 03/040257, and mixtures thereof. Electroluminescent emissive layers comprising a charge carrying host material and a metal complex have been described by Thompson et al., in U.S. Pat. No. 6,303,238, and by Burrows and Thompson in published PCT applications WO 00/70655 and WO 01/41512. Examples of conjugated polymers include, but are not limited to poly(phenylenevinylenes), polyfluorenes, poly(spirobifluorenes), polythiophenes, poly(p-phenylenes), copolymers thereof, and mixtures thereof. 
         [0027]    The particular material chosen may depend on the specific application, potentials used during operation, or other factors. The EL layer  130  containing the electroluminescent organic material can be applied using any number of techniques including liquid-phase processing. In another embodiment, an EL polymer precursor can be applied and then converted to the polymer, typically by heat or other source of external energy (e.g., visible light or UV radiation). 
         [0028]    Optional layer  140  can function both to facilitate electron injection/transport, and can also serve as a confinement layer to prevent quenching reactions at layer interfaces. More specifically, layer  140  may promote electron mobility and reduce the likelihood of a quenching reaction if layers  130  and  150  would otherwise be in direct contact. Examples of materials for optional layer  140  include, but are not limited to, include metal chelated oxinoid compounds, such as tris(8-hydroxyquinolato)aluminum (Alq3), bis(2-methyl-8-quinolinolato)(para-phenyl-phenolato)aluminum(III) (BAIQ), and tetrakis-(8-hydroxyquinolinato)zirconium (IV) (ZrQ) ; and azole compounds such as 2-(4-biphenylyl) -5-(4-t-butylphenyl)-1,3,4-oxadiazole (PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (TAZ), and 1,3,5-tri(phenyl-2-benzimidazole)benzene (TPBI); quinoxaline derivatives such as 2,3-bis(4-fluorophenyl)quinoxaline; phenanthrolines such as 4,7-diphenyl-1,10-phenanthroline (DPA) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (DDPA); and mixtures thereof. Alternatively, optional layer  140  may be inorganic and comprise BaO, LiF, Li 2 O, or the like. 
         [0029]    The cathode layer  150  is an electrode that is particularly efficient for injecting electrons or negative charge carriers. The cathode layer  150  can be any metal or nonmetal having a lower work function than the first electrical contact layer (in this case, the anode layer  110 ). As used herein, the term “lower work function” is intended to mean a material having a work function no greater than about 4.4 eV. As used herein, “higher work function” is intended to mean a material having a work function of at least approximately 4.4 eV. 
         [0030]    Materials for the cathode layer can be selected from alkali metals of Group 1 (e.g., Li, Na, K, Rb, Cs,), the Group 2 metals (e.g., Mg, Ca, Ba, or the like), the Group 12 metals, the lanthanides (e.g., Ce, Sm, Eu, or the like), and the actinides (e.g., Th, U, or the like). Materials such as aluminum, indium, yttrium, and combinations thereof, may also be used. Specific non-limiting examples of materials for the cathode layer  150  include, but are not limited to, barium, lithium, cerium, cesium, europium, rubidium, yttrium, magnesium, samarium, and alloys and combinations thereof. 
         [0031]    In other embodiments, additional layer(s) may be present within organic electronic devices. For example, a layer (not shown) between the buffer layer  120  and the EL layer  130  may facilitate positive charge transport, band-gap matching of the layers, function as a protective layer, or the like. Similarly, additional layers (not shown) between the EL layer  130  and the cathode layer  150  may facilitate negative charge transport, band-gap matching between the layers, function as a protective layer, or the like. Layers that are known in the art can be used. In addition, any of the above-described layers can be made of two or more layers. Alternatively, some or all of inorganic anode layer  110 , the buffer layer  120 , the EL layer  130 , and cathode layer  150 , may be surface treated to increase charge carrier transport efficiency. The choice of materials for each of the component layers may be determined by balancing the goals of providing a device with high device efficiency with the cost of manufacturing, manufacturing complexities, or potentially other factors. 
         [0032]    The different layers may have any suitable thickness. In one embodiment, inorganic anode layer  110  is usually no greater than approximately 500 nm, for example, approximately 10-200 nm; buffer layer  120 , is usually no greater than approximately 250 nm, for example, approximately 50-200 nm; EL layer  130 , is usually no greater than approximately 100 nm, for example, approximately 50-80 nm; optional layer  140  is usually no greater than approximately 100 nm, for example, approximately 20-80 nm; and cathode layer  150  is usually no greater than approximately 100 nm, for example, approximately 1-50 nm. If the anode layer  110  or the cathode layer  150  needs to transmit at least some light, the thickness of such layer may not exceed approximately 100 nm. In organic light emitting diodes (OLEDs), electrons and holes, injected from the cathode  150  and anode  110  layers, respectively, into the EL layer  130 , form negative and positively charged polar ions in the polymer. These polar ions migrate under the influence of the applied electric field, forming a polar ion exciton with an oppositely charged species and subsequently undergoing radiative recombination. A sufficient potential difference between the anode and cathode, usually less than approximately 12 volts, and in many instances no greater than approximately 5 volts, may be applied to the device. The actual potential difference may depend on the use of the device in a larger electronic component. In many embodiments, the anode layer  110  is biased to a positive voltage and the cathode layer  150  is at substantially ground potential or zero volts during the operation of the electronic device. A battery or other power source(s) may be electrically connected to the electronic device as part of a circuit but is not illustrated in  FIG. 1 . 
         [0033]      FIG. 2  illustrates one embodiment of a disc  200 . The disc  200  has first side  202  (shown in  FIG. 3 ) and a second side  204 . An aperture  206  passes through the disc  200  and exhibits a aperture diameter d A  at the second side  204 . The second side  204  additionally contains a recessed area  208 . This recessed area  208  acts as to shield the stream (not shown) from wind generated during relative motion between the substrate (not shown) and a nozzle assembly  502  (see  FIG. 5 ). A quiescent zone is formed in the recessed area  208  to produce more controlled deposition conditions. In one embodiment of the invention diameter of the disc, d D , can be 10 cm or less. In another embodiment d D  can be 5 cm or less. In another embodiment the aperture diameter d A , can be 0.05 mm or less. In another embodiment, d A  can be 0.01 mm or less. In another embodiment the diameter of the recessed area, d 2 , can be 1.0 mm or less. In another embodiment d 2  can be 0.05 mm or less. The ratio of t D / d 2  is sufficient to create the quiescent zone in the recessed area  208 . In one embodiment t D  can be 0.05 mm and d 2  can be 0.5 mm. 
         [0034]      FIG. 3  illustrates one embodiment of an edge view of the disc  200 , shown as line  3 - 3  in  FIG. 2 . The first surface  202  and the second surface  204  are separated by the thickness of the disc, as indicated by disc thickness t D , wherein t D  can be 0.1 mm or less. In one embodiment of the invention the disc thickness, t D , can be 0.05 mm or less. In another embodiment t D  can be 0.03 mm or less. In one embodiment the thickness of the aperture, t A , can be 50 μm or less. In another embodiment t A  can be 10 μm or less. Providing thin thickness of the aperture results in pressure losses that are reduced, jet exit velocity is maintained and the stream is less likely to break into droplets. Such an embodiment can be useful for depositing a buffer layer, a charge-blocking layer, a charge-injection layer, a charge-transport layer, an electroluminescent layer or a combination thereof. 
         [0035]      FIG. 4  illustrates one embodiment of a body  400  having a recessed area containing a shoulder  402  and opening  404 . Disc  200  is bonded to body  400 , wherein first surface  202  is bonded to the shoulder  402  to form a nozzle assembly  502  (shown in  FIG. 5 ). Bonding can include mechanical bonding such as fasteners, clips, or other mechanical means, gluing, soldering, welding, fusing, etc. In one embodiment, the body  400  is aluminum and coated with nickel, the disc  200  is soldered into the recessed area of body  400 . Other materials and processes can be used without altering the scope of this invention. For example, the distal end of body  400  may not contain a recess, and disc  200  can be bonded directly to the distal surface of body  400  (not shown). 
         [0036]      FIG. 5  illustrates one embodiment of a linear arrangement  500  of nozzle assemblies  502 . Arrangement  500  is a linear structure containing 16 total nozzle assemblies  502 , but any number may be used and stay within the teachings of this invention. A mixture is sent through the nozzle assembly to provide controlled deposition on the substrate. The mixture comprises a liquid and a solid material to produce a solution, suspension, dispersion, emulsion, colloidal mixtures, or other compositions. The liquid can be an organic solvent or water, as discussed later in this description. The solid is any one or more of the materials used in the buffer layer  120 , EL layer  130  or optional layer  140 . 
         [0037]    Several variables are used in the nozzle coating process to improve yields and final performance of the electronic device. A coating gap of 200-800 μm, a coating velocity of 2-10 m/s. A solids content of 2-15%, viscosity of 0.5-10 cp, and a surface tension of 20-100 dynes/cm for the mixture. 
         [0038]    In a further embodiment, the liquid mixture has a viscosity no greater than 5 centipoise. In still a further embodiment, the liquid mixture includes a liquid solvent, wherein the liquid solvent may include at two or more solvents. In yet a further embodiment, at least one of the solvents is water. 
         [0039]    Additional equipment may reside within or be used with the nozzle assembly  502 , including containers and feed lines fluidly coupled to the nozzle assembly  502  to accommodate any number of constituents to form the liquid-phase mixture. Other equipment can include any one or more stepper motors, pumps, filters, control electronics, other electrical, mechanical, or electro-mechanical assemblies or subassemblies, facilities connections, or any combination thereof. 
         [0040]    During the coating operation, the pressure within the nozzle assembly  502  can be in a range of approximately 100 to 500 KPa. In one embodiment the pressure can be kept constant and flow is controlled by a mass flow controller. The flow rate of liquid mixture from the nozzle assembly  502  can be in a range of 50 to 600 microliters per minute. In other embodiments, a higher or lower pressure, a higher or lower flow rate, or any combination thereof can also be used. After reading the specification, skilled artisans will be able to adjust or modify the coating operations to achieve pressures and flow rates for their particular applications. 
         [0041]    3. Liquid Compositions 
         [0042]    The nozzle assembly  502  can be used to deposit a variety of different materials, including liquid solutions. The following paragraphs include only some but not all of the materials that may be used. In one embodiment, one or more materials for an organic layer within an electronic device are formed using the nozzle assembly  502 . 
         [0043]    The nozzle assembly  502  is well suited for printing liquid compositions. The nozzle assembly  502  allows a wider range of operating parameters and liquid compositions to be used compared to a conventional ink-jet printer. In one embodiment, one or more parameters can affect the flow characteristics of the liquid composition. Viscosity is a parameter that can affect the flow characteristics. The viscosity can be affected by selection of the liquid medium, the solids content within the liquid medium, temperature of the liquid composition, or potentially one or more other factors, or any combination thereof. Viscosity can be affected directly by temperature (viscosity of the liquid medium increases with decreasing temperature or decreases with increasing temperature) or indirectly by changing the evaporation rate of the liquid medium within the liquid composition (i.e., using liquid medium having lower or higher boiling points, changing the temperature of the liquid composition, or a combination thereof). After reading this specification, skilled artisans will appreciate that they have many different ways to allow a significantly larger selection of liquid medium, a larger range of solids concentration of the liquid composition to be used, or a combination thereof. 
         [0044]    The liquid mixture can be in the form of a solution, dispersion, emulsion, or suspension. In the paragraphs that follow, non-limiting examples of solid materials and liquid medium are given. The solid material(s) can be selected upon the electronic or electro-radiative properties for a subsequently-formed layer. The liquid medium can be selected based on criteria described later in this specification. 
         [0045]    When using the nozzle assembly  502 , the liquid composition may have solid(s) greater than approximately 2.0 weight percent without having to worry about clogging. In one embodiment, the solid(s) content is in a range of approximately 2.0 to 3.0 weight percent. Therefore, the nozzle assembly  502  can use a liquid composition having a higher viscosity or lower boiling point compared to a conventional ink-jet printer. Further, the nozzle assembly  502  can use a liquid composition having a lower viscosity or higher boiling point compared to a conventional ink-jet printer. Additionally, the liquid medium within a liquid composition does not need to be degassed before printing. For example, a conventional ink-jet printer used for dispensing a conductive organic material within an aqueous solution requires the aqueous solvent to be degassed. However, because nozzle assembly  502  allows for more processing margin, degassing of a liquid medium is not required for the proper operation of the nozzle assembly  502 . 
         [0046]    An organic layer printed using the nozzle assembly  502  can include an organic active layer, (e.g., a radiation-emitting organic active layer or a radiation-responsive organic active layer), filter layer, buffer layer, charge-injecting layer, charge-transport layer, charge-blocking layer, or any combination thereof. The organic layer may be used as part of a resistor, transistor, capacitor, diode, etc. 
         [0047]    For a radiation-emitting organic active layer, suitable radiation-emitting materials include one or more small molecule materials, one or more polymeric materials, or a combination thereof. A small molecule material may include any one or more of those described in, for example, U.S. Pat. No. 4,356,429 (“Tang”); U.S. Pat. No. 4,539,507 (“Van Slyke”); U.S. Patent Application Publication No. US 2002/0121638 (“Grushin”); or U.S. Pat. No. 6,459,199 (“Kido”). Alternatively, a polymeric material may include any one or more of those described in U.S. Pat. No. 5,247,190 (“Friend”); U.S. Pat. No. 5,408,109 (“Heeger”); or U.S. Pat. No. 5,317,169 (“Nakano”). An exemplary material is a semiconducting conjugated polymer. An example of such a polymer includes poly(paraphenylenevinylene) (PPV), a PPV copolymer, a polyfluorene, a polyphenylene, a polyacetylene, a polyalkylthiophene, poly(n-vinylcarbazole) (PVK), or the like. In one specific embodiment, a radiation-emitting active layer without any guest material may emit blue light. 
         [0048]    For a radiation-responsive organic active layer, a suitable radiation-responsive material may include a conjugated polymer or an electroluminescent material. Such a material includes, for example, a conjugated polymer or an electro- and photo-luminescent material. A specific example includes poly(2-methoxy,5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene) (“MEH-PPV”) or a MEH-PPV composite with CN-PPV. 
         [0049]    For a hole-injecting layer, hole-transport layer, electron-blocking layer, or any combination thereof, a suitable material includes polyaniline (“PANI”), poly(3,4-ethylenedioxythiophene) (“PEDOT”), polypyrrole, an organic charge transfer compound, such as tetrathiafulvalene tetracyanoquinodimethane (“TTF-TCQN”), a hole-transport material as described in Kido, or any combination thereof. 
         [0050]    For an electron-injecting layer, electron transport layer, hole-blocking layer, or any combination thereof, a suitable material includes a metal-chelated oxinoid compound (e.g., Alq 3  or aluminum(III)bis(2-methyl-8-quinolinato)4-phenylphenolate (“BAIq”)); a phenanthroline-based compound (e.g., 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (“DDPA”) or 9,10-diphenylanthracence (“DPA”)); an azole compound (e.g., 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole (“PBD”) or 3-(4-biphenyl)-4-phenyl-5-(4-t-butylphenyl)-1,2,4-triazole (“TAZ”); an electron transport material as described in Kido; a diphenylanthracene derivative; a dinaphthylanthracene derivative; 4,4-bis(2,2-diphenyl-ethen-1-yl)-biphenyl (“DPVBI”); 9,10-di-beta-naphthylanthracene; 9,10-di-(naphenthyl)anthracene; 9,10-di-(2-naphthyl)anthracene (“ADN”); 4,4′-bis(carbazol-9-yl)biphenyl (“CBP”); 9,10-bis-[4-(2,2-diphenylvinyl)-phenyl]-anthracene (“BDPVPA”); anthracene, N-arylbenzimidazoles (such as “TPBI”); 1,4-bis[2-(9-ethyl-3-carbazoyl)vinylenyl]benzene; 4,4′-bis[2-(9-ethyl-3-carbazoyl)vinylenyl]-1,1′-biphenyl; 9,10-bis[2,2-(9,9-fluorenylene)vinylenyl]anthracene; 1,4-bis[2,2-(9,9-fluorenylene)vinylenyl]benzene; 4,4′-bis[2,2-(9,9-fluorenylene)vinylenyl]-1,1′-biphenyl; perylene, substituted perylenes; tetra-tert-butylperylene (“TBPe”); bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl) iridium III (“F(Ir)Pic”); a pyrene, a substituted pyrene; a styrylamine; a fluorinated phenylene; oxidazole; 1,8-naphthalimide; a polyquinoline; one or more carbon nanotubes within PPV; or any combination thereof. 
         [0051]    For an electronic component, such as a resistor, transistor, capacitor, etc., the organic layer may include one or more of thiophenes (e.g., polythiophene, poly(alkylthiophene), alkylthiophene, bis(dithienthiophene), alkylanthradithiophene, etc.), polyacetylene, pentacene, phthalocyanine, or any combination thereof. 
         [0052]    Examples of an organic dye include 4-dicyanmethylene-2-methyl-6- (p-dimethyaminostyryl)-4H-pyran (DCM), coumarin, pyrene, perylene, rubrene, a derivative thereof, or any combination thereof. 
         [0053]    Examples of an organometallic material include a functionalized polymer comprising one or more functional groups coordinated to at least one metal. An exemplary functional group contemplated for use includes a carboxylic acid, a carboxylic acid salt, a sulfonic acid group, a sulfonic acid salt, a group having an OH moiety, an amine, an imine, a diimine, an N-oxide, a phosphine, a phosphine oxide, a β-dicarbonyl group, or any combination thereof. An exemplary metal contemplated for use includes a lanthanide metal (e.g., Eu, Tb), a Group 7 metal (e.g., Re), a Group 8 metal (e.g., Ru, Os), a Group 9 metal (e.g., Rh, Ir), a Group 10 metal (e.g., Pd, Pt), a Group 11 metal (e.g., Au), a Group 12 metal (e.g., Zn), a Group 13 metal (e.g., Al), or any combination thereof. Such an organometallic material includes a metal chelated oxinoid compound, such as tris(8-hydroxyquinolato)aluminum (Alq 3 ); a cyclometalated iridium or platinum electroluminescent compound, such as a complex of iridium with phenylpyridine, phenylquinoline, or phenylpyrimidine ligands as disclosed in published PCT Application WO 02/02714, an organometallic complex described in, for example, published applications US 2001/0019782, EP 1191612, WO 02/15645, WO 02/31896, and EP 1191614; or any mixture thereof. 
         [0054]    An examples of a conjugated polymer includes a poly(phenylenevinylene), a polyfluorene, a poly(spirobifluorene), a copolymer thereof, or any combination thereof. 
         [0055]    Selecting a liquid medium can also be an important factor for achieving one or more proper characteristics of the liquid mixture. A factor to be considered when choosing a liquid medium includes, for example, viscosity of the resulting solution, emulsion, suspension, or dispersion, molecular weight of a polymeric material, solids loading, type of liquid medium, boiling point of the liquid medium, temperature of an underlying substrate, thickness of an organic layer that receives a guest material, or any combination thereof 
         [0056]    In some embodiments, the liquid medium includes at least one solvent. An exemplary organic solvent includes a halogenated solvent, a colloidal-forming polymeric acid, a hydrocarbon solvent, an aromatic hydrocarbon solvent, an ether solvent, a cyclic ether solvent, an alcohol solvent, a glycol solvent, a ketone solvent, a nitrile solvent, a sulfoxide solvent, an amide solvent, or any combination thereof. 
         [0057]    An exemplary halogenated solvent includes carbon tetrachloride, methylene chloride, chloroform, tetrachloroethylene, chlorobenzene, bis(2-chloroethyl)ether, chloromethyl ethyl ether, chloromethyl methyl ether, 2-chloroethyl ethyl ether, 2-chloroethyl propyl ether, 2-chloroethyl methyl ether, or any combination thereof. 
         [0058]    An exemplary colloidal-forming polymeric acid includes a fluorinated sulfonic acid (e.g., fluorinated alkylsulfonic acid, such as perfluorinated ethylenesulfonic acid) or any combinations thereof. 
         [0059]    An exemplary hydrocarbon solvent includes pentane, hexane, cyclohexane, heptane, octane, decahydronaphthalene, a petroleum ether, ligroine, or any combination thereof. 
         [0060]    An exemplary aromatic hydrocarbon solvent includes benzene, naphthalene, toluene, xylene, ethyl benzene, cumene (iso-propyl benzene) mesitylene (trimethyl benzene), ethyl toluene, butyl benzene, cymene (iso-propyl toluene), diethylbenzene, iso-butyl benzene, tetramethyl benzene, sec-butyl benzene, tert-butyl benzene, anisole, 4-methylanisole, 3,4-dimethylanisole, or any combination thereof. 
         [0061]    An exemplary ether solvent includes diethyl ether, ethyl propyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, methyl t-butyl ether, glyme, diglyme, benzyl methyl ether, isochroman, 2-phenylethyl methyl ether, n-butyl ethyl ether, 1,2-diethoxyethane, sec-butyl ether, diisobutyl ether, ethyl n-propyl ether, ethyl isopropyl ether, n-hexyl methyl ether, n-butyl methyl ether, methyl n-propyl ether, or any combination thereof. 
         [0062]    An exemplary cyclic ether solvent includes tetrahydrofuran, dioxane, tetrahydropyran, 4 methyl-1,3-dioxane, 4-phenyl-1,3-dioxane, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 1,4-dioxane, 1,3-dioxane, 2,5-dimethoxytetrahydrofuran, 2,5-dimethoxy-2,5-dihydrofuran, or any combination thereof. 
         [0063]    An exemplary alcohol solvent includes methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol (i.e., iso-butanol), 2-methyl-2-propanol (i.e., tert-butanol), 1-pentanol, 2-pentanol, 3-pentanol, 2,2-dimethyl-1-propanol, 1-hexanol, cyclopentanol, 3-methyl-1-butanol, 3-methyl-2-butanol, 2-methyl -1-butanol, 2,2-dimethyl-1-propanol, 3-hexanol, 2-hexanol, 4-methyl-2-pentanol, 2-methyl-1-pentanol, 2-ethylbutanol, 2,4-dimethyl-3-pentanol, 3-heptanol, 4-heptanol, 2-heptanol, 1-heptanol, 2-ethyl-1-hexanol, 2,6-dimethyl-4-heptanol, 2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol, or any combination thereof. 
         [0064]    An alcohol ether solvent may also be employed. An exemplary alcohol ether solvent includes 1-methoxy-2-propanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-butanol, ethylene glycol monoisopropyl ether, 1-ethoxy-2-propanol, 3-methoxy-1-butanol, ethylene glycol monoisobutyl ether, ethylene glycol mono-n-butyl ether, 3-methoxy-3-methylbutanol, ethylene glycol mono-tert-butyl ether, or any combination thereof. 
         [0065]    An exemplary glycol solvent includes ethylene glycol, propylene glycol, propylene glycol monomethyl ether (PGME), dipropylene glycol monomethyl ether (DPGME), or any combination thereof. 
         [0066]    An exemplary ketone solvent includes acetone, methylethyl ketone, methyl iso-butyl ketone, cyclohexanone, isopropyl methyl ketone, 2-pentanone, 3-pentanone, 3-hexanone, diisopropyl ketone, 2-hexanone, cyclopentanone, 4-heptanone, iso-amyl methyl ketone, 3-heptanone, 2-heptanone, 4-methoxy-4-methyl-2-pentanone, 5-methyl-3-heptanone, 2-methylcyclohexanone, diisobutyl ketone, 5-methyl-2-octanone, 3-methylcyclohexanone, 2-cyclohexen-1-one, 4-methylcyclohexanone, cycloheptanone, 4-tert-butylcyclohexanone, isophorone, benzyl acetone, or any combination thereof. 
         [0067]    An exemplary nitrile solvent includes acetonitrile, acrylonitrile, trichloroacetonitrile, propionitrile, pivalonitrile, isobutyronitrile, n-butyronitrile, methoxyacetonitrile, 2-methylbutyronitrile, isovaleronitrile, N-valeronitrile, n-capronitrile, 3-methoxypropion itrile, 3-ethoxypropionitrile, 3,3′-oxydipropionitrile, n-heptanenitrile, glycolonitrile, benzonitrile, ethylene cyanohydrin, succinonitrile, acetone cyanohydrin, 3-n-butoxypropionitrile, or any combination thereof. 
         [0068]    An exemplary sulfoxide solvent includes dimethyl sulfoxide, di-n-butyl sulfoxide, tetramethylene sulfoxide, methyl phenyl sulfoxide, or any combinations thereof. 
         [0069]    An exemplary amide solvent includes dimethyl formamide, dimethyl acetamide, acylamide, 2-acetamidoethanol, N,N-dimethyl-m-toluamide, trifluoroacetamide, N,N-dimethylacetamide, N,N-diethyldodecanamide, epsilon-caprolactam, N,N-diethylacetamide, N-tert-butylformamide, formamide, pivalamide, N-butyramide, N,N-dimethylacetoacetamide, N-methyl formamide, N,N-diethylformamide, N-formylethylamine, acetamide, N,N-diisopropylformamide, 1-formylpiperidine, N-methylformanilide, or any combinations thereof. 
         [0070]    A crown ether contemplated includes any one or more crown ethers that can function to assist in the reduction of the chloride content of an epoxy compound starting material as part of the combination being treated according to the invention. An exemplary crown ether includes benzo-15-crown-5; benzo-18-crown-6; 12-crown-4; 15-crown-5; 18-crown-6; cyclohexano-15-crown-5; 4′,4″(5″)-ditert-butyldibenzo-18-crown-6; 4′,4″(5″)-ditert-butyldicyclohexano-18-crown-6; dicyclohexano-18-crown-6; dicyclohexano-24-crown-8; 4′-aminobenzo-15-crown-5; 4′-aminobenzo-18-crown-6; 2-(aminomethyl)-15-crown-5; 2-(aminomethyl)-18-crown-6; 4′-amino-5′-nitrobenzo-15-crown-5; 1-aza-12-crown-4; 1-aza-15-crown-5; 1-aza-18-crown-6; benzo-12-crown-4; benzo-15-crown-5; benzo-18-crown-6; bis((benzo-15-crown-5)-15-ylmethyl)pimelate; 4-bromobenzo-18-crown-6; (+)-(18-crown-6)-2,3,11,12-tetra-carboxylic acid; dibenzo-18-crown-6; dibenzo-24-crown-8; dibenzo-30-crown-10; ar-ar′-di-tert-butyldibenzo-18-crown-6; 4′-formylbenzo-15-crown-5; 2-(hydroxymethyl)-12-crown-4; 2-(hydroxymethyl)-15-crown-5; 2-(hydroxymethyl)-18-crown-6; 4′-nitrobenzo-15-crown-5; poly-[(dibenzo-18-crown-6)-co-formaldehyde]; 1,1-dimethylsila-11-crown-4; 1,1-dimethylsila-14-crown-5; 1,1-dimethylsila-17-crown-5; cyclam; 1,4,10,13-tetrathia-7,16-diazacyclooctadecane; porphines; or any combination thereof. 
         [0071]    In another embodiment, the liquid medium includes water. A conductive polymer complexed with a water-insoluble colloid-forming polymeric acid can be deposited over a substrate and used as a charge-transport layer. 
         [0072]    Many different classes of liquid medium (e.g., halogenated solvents, hydrocarbon solvents, aromatic hydrocarbon solvents, water, etc.) are described above. Mixtures of more than one of the liquid medium from different classes may also be used. 
         [0073]    The liquid mixture may also include an inert material, such as a binder material, a filler material, or a combination thereof. With respect to the liquid mixture, an inert material does not significantly affect the electronic, radiation emitting, or radiation responding properties of a layer that is formed by or receives at least a portion of the liquid mixture. 
         [0074]    It is to be appreciated that certain features of the invention which are for clarity, described above in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity described in the context of a single embodiment, may also be provided separately or in any subcombination. Further, reference to values stated in ranges include each and every value within that range.