KR20150002812A - Functionalization of a substrate - Google Patents

Abstract

Thereby increasing the work function of the electrode. The method includes obtaining a negatively charged species from the precursor using electromagnetic radiation, and reacting the surface of the electrode with the negatively charged species. An electrode comprising a functionalized substrate is also provided.

Description

{FUNCTIONALIZATION OF A SUBSTRATE}

Cross reference of related application

This application is related to U.S. Patent Application No. 13 / 446,927, filed April 13, 2012, U.S. Patent Application No. 61 / 673,147, filed July 18, 2012, U.S. Patent Application No. 60 / 673,147 filed on March 30, No. 61 / 806,855, and Canadian Patent Application No. 2,774,591, filed April 13, 2012, each of which is incorporated herein by reference in its entirety.

Technical field

The following generally relates to functionalization of the substrate.

Organic light emitting diodes (OLEDs) are becoming increasingly popular for displays and other optoelectronic applications. Organic electronic displays typically consist of a matrix of OLEDs, each containing a thin film of organic materials that emit light upon excitation by an electrical current. The organic thin film is typically sandwiched between an anode and a cathode, which provides current to the organic thin film to allow the film to emit light. In the display, light emitted by the organic thin film exits the thin film and is transmitted through at least one of the electrodes to be visible to a user. Thus, at least one of the electrodes of the electrode pair comprises a transparent conductor, for example a transparent conducting film (TCO).

Indium tin oxide (ITO) is the most commonly used TCO due to its transparency and its high conductivity relative to other TCO's. ITO is used in a variety of applications requiring transparency and conductivity, including liquid crystal displays, plasma displays, photoelectric conversion devices, electronic ink displays, and OLED displays. ITO is typically deposited as a thin film on a transparent substrate such as glass.

Regarding OLEDs, an ITO layer is typically formed on a transparent substrate to be used as an anode. A hole is injected from the anode into the hole transport layer (HTL), and the layer transports the holes to the light emitting thin film layer. At the same time, electrons are injected through the cathode, transported through the electron transport layer (ETL), and recombined with the holes in the light emitting thin film layer to emit photons. Photons emitted from the thin film layer may then exit the thin film layer, pass through the HTL, and exit the OLED device through the ITO layer and the transparent substrate.

The energy required to inject holes from the anode varies depending on the height of the hole injection blocking layer. The height of the hole injection blocking layer varies depending on the difference between the work function of the anode and the highest level occupied molecular orbital (HOMO) of the adjacent organic layer. The hole injection blocking layer of conventional OLEDs is high, but this can be alleviated by providing one or more intermediate organic layers. Each organic layer subsequently has a deeper HOMO level, which allows holes to pass through a larger number of smaller injection blocking layers than a single larger injection blocking layer. However, each additional organic layer increases the cost of the apparatus and reduces the yield of the manufacturing process.

It is an object of the present invention to alleviate or eliminate one or more of the above disadvantages.

In one aspect, electromagnetic radiation is used to obtain negatively charged species from a precursor; And reacting the electrode surface with the negatively charged species.

The negatively charged species may be halogen. The electromagnetic radiation may have a wavelength of at least about 100 nm. The electromagnetic radiation may have a wavelength of less than about 400 nm. The method may also include cleaning the surface of the electrode. The electrode may be a transparent conductive film. The transparent conductive film may be ITO. And select the negatively charged species to acquire a predetermined work function electrode. The surface coverage of the species may be selected to obtain an electrode of a predetermined work function. It is possible to function on the substrate up to approximately a single layer of halogen. The halogen may be chlorine. The precursor may be a volatile liquid. The precursor may be a gas. The substrate can be functionalized to increase its airborne stability.

In yet another aspect, an electrode comprising a substrate functionalized according to the method is provided. An organic electronic device comprising the electrode is also provided.

In yet another aspect, there is provided the use of a system for chemically functionalizing a substrate with a species, said system comprising: a reaction chamber; A radiation emitter operable to emit electromagnetic radiation into the reaction chamber; Wherein the reaction chamber is operable to receive a precursor of the species and a substrate; Wherein the electromagnetic radiation generates radicals from the species precursor and chemically bonds with the substrate. The radiation emitter may emit radiation having a wavelength of at least about 100 nm. The radiation emitter may emit radiation having a wavelength of less than about 400 nm. In an exemplary embodiment, the radiation emitter is external to the reaction chamber; The reaction chamber may be operated to at least partially transmit ultraviolet light from the radiation emitter.

In yet another embodiment, plasma is used to obtain chlorine from the precursor; And reacting the surface of the electrode with the chlorine to form about 20% or more of the chlorine monolayer. In an exemplary embodiment, a single layer of approximately chlorine can be reacted with the surface of the electrode. The substrate may include a transparent conductive film. The transparent conductive film may be ITO. The surface coverage of the chlorine can be selected so that a predetermined work function electrode is obtained.

Yet another aspect provides an electrode comprising a substrate functionalized at about 20% or more of a halogen monolayer. And an organic electronic device including the electrode. The organic electronic device may include an organic light emitting diode. The organic light emitting diode may be phosphorescent. The organic light emitting diode may be fluorescent.

Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a diagram illustrating a system according to the present invention comprising a substrate functionalized at about 0.5 of a species single layer;
Figure 2 is a diagram illustrating a system according to the invention in which the substrate is functionalized with approximately 0.7 of the species monolayer;
Figure 3 is a diagram illustrating a system according to the present invention in which the substrate is functionalized with approximately one monolayer of the species;
FIG. 4 is an X-ray photoelectron spectroscopy graph showing that the bonding state of indium-chlorine bond in InCl ₃ is equivalent to the bonding state of indium-chlorine bond in chlorine-functionalized ITO;
FIG. 5 is an X-ray photoelectron spectroscopy graph showing the relationship between the processing time and the chlorination of the ITO surface; FIG.
6 is an energy level diagram illustrating the work function of an exemplary ITO electrode;
Figure 7 is an energy level diagram illustrating the work function of an exemplary chlorine-functionalized ITO electrode;
8 is a typical chart showing the relationship between the approximate surface coverage of chlorine on the ITO substrate and the work function of the ITO substrate;
Figure 9 is an X-ray photoelectron spectroscopy graph comparing the binding energies of various halogen-functionalized substrates;
10 is a typical chart comparing the change in work function over time of the air of the chlorine-functionalized ITO substrate and the top ITO substrate;
11 is a table showing the work function of the various chlorinated and base substrates after exposure to air;
12 is a chart comparing the transmittance of chlorine-functionalized ITO on a glass substrate to the transmittance of a top ITO electrode on the same glass substrate;
13 is a chart showing the spectrum of ultraviolet emitters;
14 is an energy level diagram of an exemplary phosphorescent green OLED structure comprising a top ITO anode;
Figure 15 is an energy level diagram of an exemplary phosphorescent green OLED structure comprising a chlorinated ITO anode;
16 is a typical chart showing the relationship between the work function of the chlorine functionalized surface and the hole injection blocking layer height into the hole transport layer;
Figure 17 is an energy level diagram of an exemplary phosphorescent green OLED comprising a chlorine-functionalized anode;
18 is a current-voltage chart showing the reduction of the required driving voltage with increasing surface chlorination of the ITO anode;
19 is a chart showing the relationship between the luminous efficiency and current efficiency of the OLED of FIG. 17 comprising an anode with a single layer of chlorine;
Figure 20 is a diagram illustrating the efficiency of the OLED of Figure 17 including a single layer of chlorine on the ITO anode;
Figure 21 is a table comparing the efficiency of the OLED of Figure 17 with a prior art phosphorescent green OLED device comprising a monolayer of chlorine on the ITO anode;
22 is a chart showing the change in luminescence over time of an OLED including a chlorine functionalized anode;
23 is an energy level diagram of an exemplary fluorescent green OLED;
Figure 24 is a diagram showing current-voltage characteristics of an exemplary fluorescent green OLED including a chlorine-functionalized ITO anode;
Figure 25 is a diagram illustrating the efficiency of an exemplary fluorescent green OLED comprising a chlorine-functionalized ITO anode;
26 is a chart showing current densities for the electric field of a chlorinated ITO anode for different anode types;
Figure 27 is a diagram illustrating an exemplary plasma functionalization apparatus in accordance with the present invention;
28 is a diagram illustrating another exemplary plasma functionalization apparatus in accordance with the present invention;
29 is an energy level diagram of an exemplary phosphorescent green OLED comprising an ITO anode that is functionalized with chlorine.

For simplicity and clarity of illustration, where appropriate, reference numerals may be repeated to indicate corresponding or similar elements in the figures. In addition, numerous specific details are set forth in order to provide a thorough understanding of the exemplary embodiments disclosed herein. However, it will be understood by one of ordinary skill in the art that the exemplary embodiments disclosed in the present invention can be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail in order not to obscure the exemplary embodiments disclosed in the present invention.

In addition, the above description should not be construed as limiting the scope of the exemplary embodiments disclosed in the present invention. For example, reference is made to the functionalization of a transparent conductive film (TCO) substrate. It will be appreciated that other substrates may be functionalized using the process described herein. Other non-transparent or non-conductive substrates may also be functionalized according to the process disclosed herein.

The present invention provides a method of functionalizing a substrate in one species. In particular, it provides functionalization of the electrode by negatively charged species to increase the work function of the electrode. It also provides a method of functionalizing the TCO electrode that achieves a higher work function without significantly altering the critical properties of the TCO electrode, e.g., conductivity and device stability. In one embodiment, the substrate is functionalized using plasma dissociation of the precursor to release a reactive species, such as a halogen species. The halogen species chemically react with the substrate to increase the work function of the substrate.

Also provided is a substrate functionalized below a single layer of approximately negatively charged species. The negatively charged species may be halogen. The halogen may be chlorine. The substrate may be a TCO. An electrode comprising a functionalized substrate is also provided. The substrate may be functionalized to increase the work function of the electrode. In an exemplary embodiment, the substrate is functionalized at about 20% or more of the monolayer. About 20% functionalization can be a significant accomplishment. An organic electronic device using an electrode comprising a functionalized substrate is also provided.

It has now been found that a transparent conducting film comprising indium tin oxide (ITO) (also referred to as tin-doped indium oxide) can now be used directly as an electrode in an organic electronic device, for example an organic light emitting diode (OLED) lost. The work function of the ITO is approximately 4.7 eV in vacuum. The use of ITO as the anode causes a high hole injection blocking layer and poor operational stability of the device, since 4.7 eV is rarely compatible with the highest level occupied molecular orbital (HOMO) levels of many common hole transport materials. An anode having a work function of energy closer to the HOMO level of the adjacent hole transporting organic material will reduce the hole injection blocking layer thereby reducing the required operating voltage of the organic electronic device and increasing the efficiency and operational stability Are well known.

In the case of OLEDs, the active luminescent material typically has a HOMO level much greater than 4.7 eV. For example, the HOMO level of tris (8-hydroxyquinolinato) aluminum (Alq ₃ ), a fluorescent green light emitting compound, is 5.75 eV. Although some organic luminescent materials may have a HOMO level closer to 4.7 eV, they are typically doped with a host matrix having a HOMO level much higher than 4.7 eV. Typically, holes must be injected into the HOMO of the host in order for the dopant to emit light. For example, the HOMO level of tris (2-phenylpyridine) iridium (III) [Ir (ppy) ₃ ], which is a phosphorescent green luminescent compound, is 5.4 eV, but typically 4,4'-bis (carbazol- Lt; / RTI > biphenyl (CBP) matrix. CBP has a HOMO level of 6.1 eV, which is much larger than 4.7 eV. In particular, the HOMO level of the host material used in the phosphorescent OLED is greater than about 6 eV. Thus, there is a need for a transparent electrode having a work function that is larger, preferably slightly greater, than the HOMO level of the host material used in the OLED. In particular, a transparent electrode having a work function of about 6 eV or more is required.

One way to increase the work function of the TCO substrate is to clean the surface of the substrate to remove contaminants. For example, the surface of the TCO substrate can be cleaned using ultraviolet (UV) ozone or O ₂ plasma treatment. Plasma surface treatment and UV ozone surface treatment are effective for removal of organic contaminants and can leave negatively charged species on the surface of the TCO substrate. As an example, UV ozone cleaning of the ITO substrate surface can increase its work function to about 5.0 eV. Cleaning of the substrate may cause band bending and an increase in the surface dipole of the TCO at the surface of the substrate due to negatively charged oxygen species on the surface of the substrate, thereby increasing the work function of the ITO substrate. While referring to cleaning the TCO substrate using UV ozone or O ₂ plasma, the substrate may be cleaned using a liquid cleaning method, such as a detergent or a solvent.

It has been recognized that another way to increase the work function of ITO, an important TCO substrate, is to chemically treat the ITO substrate with a negative-working halogen, such as fluorine. In the example of an ITO substrate, a halogen can react with indium or tin atoms on the substrate surface to form a layer of approximately similar indium halide. The process of reacting the surface of the TCO substrate with a halogen can be referred to as "functionalization ".

One way of chemically treating the TCO substrate with halogens is to react the surface of the substrate with a halogen-containing acid (e.g., hydrochloric acid). The halogen gas may also be dissolved in the carrier liquid and applied to the surface of the TCO electrode. However, such a process is difficult to control, may corrode the surface of the substrate, and leaves very little halogen that is functionalized on the surface of the substrate. Thus, the substrate surface may become coarser and more contaminated, while the work function of the electrode may not be sufficiently increased. Furthermore, the conductivity and transparency of the substrate may also be reduced by the use of the process. The halogenation of the substrate using an elemental hydrogen containing solution (e.g. HCl) may be carried out in conjunction with UV ozone or O ₂ plasma treatment.

The work function of the TCO substrate may also be increased using a halogen containing plasma (which may cause the halide species to react with the surface of the TCO). For example, a fluorocarbon plasma such as CFH ₃ , an inorganic fluorine containing plasma such as SF ₆ , or a pure halogen plasma such as F ₂ may be used. Multiple plasma gases may be used together. Carrier gases, such as Ar, He or N ₂ , may also be used.

The halogen-containing plasma is typically used as a standard reactive ion etching (RIE) industrial process for dry etching of substrates comprising TCO electrodes. Thus, the halogen-containing plasma typically corrodes the surface of the substrate. This may reduce the conductivity of the surface and contaminate the surface with carbon halide. Halogenated carbon is a molecule comprising at least one carbon atom covalently bonded to one or more halogen atoms (e.g., fluorine, chlorine, iodine, and bromine). The chemical bond between the contaminant and the substrate varies depending on the materials involved, the type of plasma used, and the process conditions. The addition of an oxidizing agent (e.g., O ₂ ) may reduce the amount of halogenated carbon deposited and may also increase the rate at which the substrate is corroded, which may adversely affect other properties of the substrate. As further disclosed below, exemplary devices provide functionalized species on the surface of the substrate while reducing corrosion of the substrate.

From the electronegativity of each of fluorine, chlorine, iodine, and bromine, it can be expected that fluorine functionalization will provide the greatest increase in work function since it has the highest electronegativity and thus can form the largest surface dipole Can be expected. Surprisingly, it has been found to the present invention that the chlorinated TCO has a much higher work function. This has been demonstrated from density functional theory calculations and experimental results, as measured by X-ray photoelectron spectroscopy (XPS) using an ITO substrate functionalized according to the method disclosed in the present invention. Table 1 summarizes the above results.

The experimental and theoretical work function of functionalized ITO The functionalized halogens on the ITO surface The experimental work function (XPS) [eV] Calculation of Density Functionality Theory [eV] Fluorine 5.7 5.7 Goat 6.1 6.1 bromine 5.4 - iodine 5.2 -

Thus, a chlorinated TCO can have a higher work function than TCOs functionalized with other halogens.

The above-mentioned UV ozone and O ₂ plasma cleaning treatments are reversible. For example, the surface of the cleaned TCO substrate can be re-contaminated, negatively charged species on the TCO surface can be desorbed, and the surface of the substrate is susceptible to hydrolysis. While the halogenation treatment described above provides greater stability than UV ozone or O ₂ plasma treatment, a typical application of these treatments is to attack the surface of the TCO substrate. Furthermore, this halogenation treatment can also affect other important properties of the TCO, including surface roughness, conductivity and transparency. In addition, the treatment of halogen-containing gases for plasma processes requires special safety precautions due to the toxic and reactive nature of the related materials.

The above-mentioned techniques may not be able to increase the work function of the TCO substrate to a level that allows efficient injection of holes into the hole transporting organic material having a deep HOMO level (e.g., above 6 eV). As a result, an additional hole injection layer (HIL) and a hole transport layer (HTL) having a HOMO level between the work function of the TCO substrate and the HOMO level of the active organic layer are deposited on a practical organic optoelectronic device Typically required. For example, a number of intermediate organic layers may be used, each of which has a deeper HOMO level subsequently. This allows holes to pass through a larger number of smaller injection barrier layers than a single large injection barrier layer. Each additional layer increases the cost of the apparatus and reduces the yield of the manufacturing process.

Other methods of sufficient integration of TCO electrodes on the device having a high work function are high work-function polymer to the TCO (e.g., PEDOT), a self-assembled monolayer (SAM), or a metal oxide (for example WO ₃₎ ≪ / RTI > However, such methods can increase impedance, device complexity, and fabrication costs, while introducing additional problems associated with device stability.

Exemplary embodiments disclosed herein relate to the functionalization of a TCO thin film by halogen for modification of the work function in one aspect. In particular, exemplary embodiments are disclosed with reference to halogens and / or halogenated carbons released from halogen-containing precursor compounds under ultraviolet light. However, it is recognized that it is within the scope of the present invention to functionalize other substrates using the methods disclosed herein. In one embodiment, the substrate is functionalized using plasma dissociation of a precursor that releases a negatively charged species, such as a halogen. The halogen chemically reacts with the substrate to increase the work function of the substrate. For example, functionalizing a substrate with a halogen using a halogen-containing plasma, and in particular a chlorine-containing plasma, is within the scope of the present invention, as further disclosed below.

In another embodiment, there is provided a method of functionalizing a surface of a substrate into a species, wherein the precursor containing the species is dissociated using electromagnetic (EM) radiation. The species then reacts with the substrate to increase the work function of the substrate. In particular, the TCO substrate can be functionalized with halogens by dissociating the halogen atoms from the precursor using EM radiation. It has been found that ultraviolet radiation (UV) is particularly effective, although electromagnetic radiation of any wavelength that destroys the bond between the species and the precursor can be used. In particular, UV radiation having a wavelength of 100 nm to 400 nm has been found to be effective. A catalyst may assist in breaking the bond between the halogen and the precursor. The catalyst may comprise a chemical surface of the substrate.

The chemical bond between the species and the surface can increase the stability of the functionalized material in air, as further disclosed herein.

In some embodiments, and in the examples disclosed herein, the halogen-containing compound is a volatile halogen-containing organic precursor. It will be appreciated that inorganic precursors may also be used. Organic precursors that emit halogen atoms include carbon halides. The precursor may comprise two different halogens, such as fluorine and chlorine. For example, the halogen-containing precursor may comprise a mixture of fluorine and chlorine.

Exemplary precursors include, for example, halogenated alkanes, halogenated alkenes, and halogenated aromatic compounds. Typical chlorinated precursors include chloromethane, dichloromethane tetrachloromethane, perchlorethylene, tetrachlorethylene, 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, carbon tetrachloride, chloro Methylene chloride, methylene chloride, 1,1,1-trichloroethane, 1,2,3-trichloropropane, ethylene dichloride, dichloropropane, dichlorobenzene, trichlorobenzene, propylene Dichloride, 1,2-dichloroethylene, 1,1-dichloroethane and the like. The precursor may comprise a halogen-containing polymer, such as polytetrafluoroethylene (PTFE). The precursor may include metal halides, such as indium halide, zinc halide, and tin halide. In one example, the metal halide species is preferably a constituent metal element of the substrate. The constituent metal elements will typically not substantially alter the surface chemistry of the substrate if the metal component of the precursor remains on the surface of the substrate. For example, tin halide can be used as a precursor to a tin oxide substrate, while indium halide can be used as a halogen-containing species for ITO.

Upon functionalization of the substrate, the residual contamination can be removed by further treatment with suitable wavelength of EM radiation. The contaminants can be removed using UV ozone treatment and / or using a suitable plasma cleaning treatment, such as an O ₂ plasma. The cleaning process is performed at low energy to reduce the possibility of corrosion of the surface of the substrate. When an organic precursor is used, oxygen reacts with the remainder of the organic precursor molecule to form volatile molecules (e.g., CO ₂ and H ₂ O), which can advantageously be flushed from the surface of the substrate. Volatile molecules may also volatilize from the surface of the substrate. Thus, in some embodiments, the organic precursor may leave less contamination after the washing step than the inorganic precursor.

However, inorganic precursors may also be used in the process disclosed herein. Examples of such precursors include pure halogen gases, hydrogen halides, boron halides, sulfur halides and phosphorus halides.

In some embodiments, the substrate may be functionalized with other volatile precursors, such as, for example, sulfur, boron, or phosphorus. For example, ammonium sulphide can be used to functionalize the substrate with sulfur. Other species may be used that can be functionalized on the surface of the substrate to alter the work function.

The processing of the substrate includes obtaining a transparent conductive (TC) substrate, such as an ITO film, deposited on the glass. Other exemplary TCO substrates include those deposited on a glass such as tin oxide, indium oxide, cadmium oxide, FTO, ZnO, NiO, MoO3, WO3, AuOx (oxidized gold), cadmium oxide tin oxide Tin oxide (ZTO), antimony tin oxide (ATO), zinc oxide (AZO), titanium oxide zinc (TZO), gallium gallium oxide (GZO), aluminum gallium gallium oxide (AGZO), indium gallium gallium oxide (IGZO) Gallium indium (GIO), zinc oxide indium (ZIO), gallium indium tin oxide (GITO), zinc indium tin oxide (ZITO), titanium oxide indium (TIO), tin oxide cadmium (TCO) Zinc cadmium oxide (ZCO), and aluminum cadmium oxide (ACO). It will be appreciated that other substrates including transparent conductive (TC) substrates may be used.

The TC substrate may be deposited on a transparent mechanical support layer, e.g., glass. The mechanical support layer may be rigid, flexible, planar, warped, or have any other geometry that can be functionalized using the methods disclosed herein.

The substrate may comprise a number of different layers. For example, the substrate may comprise a plurality of different TCO layers, a metal film on top of the TCO, a metal film sandwiched between the two TCO layers, or a thin layer of a high work function material, such as a transition metal, . ≪ / RTI > The various layers in the substrate may be conductive, anti-conducting, or insulating.

The substrate may comprise a plurality of different metal, metal oxide, TCO, polymer and layers of carbon based material. The electrode may be a metal coated with a layer of a metal oxide containing a unique metal oxide. The electrode may be solid or porous. One or more layers of the substrate may comprise nano-material components, such as nano-particles, nano-rods, nano-tubes or other nano-scale materials. One or more layers of the substrate may comprise a complex of different materials, for example nano-particles in a polymer matrix. One or more layers of the substrate may comprise micron-scale particles.

The substrate can be patterned with nano-scale or micron-scale features, e.g., features to enhance light extraction of light from the optoelectronic device. One or more layers of the substrate may be patterned. The substrate may comprise a plurality of layers having different refractive indexes to form, for example, a Bragg mirror or a photonic crystal.

The substrate may be transparent, semi-transparent, opaque or reflective. The substrate may comprise a mechanical support layer, for example a piece of glass, flexible plastic or semiconductor wafer. The substrate and the mechanical support layer may be the same material. The substrate may be mechanically self-supporting, for example a metal foil or a silicon wafer.

Although reference is made to functionalizing a substrate with a halogen, it will be appreciated that the substrate may be functionalized with other species. For example, the substrate may be functionalized with carbon halide to affect the surface energy of the functionalized surface. Typically, the halogenated carbon treatment will less etch the surface of the TCO substrate than the halogenated treatment, but the equipment required to perform the halogenated carbon treatment is specialized. In addition, the conductivity of some of the halogenated carbons strongly depends on process conditions and is therefore difficult to control. Even if the process conditions are precisely controlled, the most conductive halogenated carbons, e.g., conductive fluorocarbons, are much less conductive than many TCO's, including ITO. However, EM dissociation of a halogenated carbon precursor for depositing a halogenated carbon film on a substrate may also be achieved as described below with reference to Fig.

Returning to Fig. 1, a system for substrate functionalization is provided. The system may include a reaction chamber 126 in which the substrate 104 may be placed. One species may be deposited on the substrate 104 in the reaction chamber 126. The precursor compound 108 may be placed in or supplied to the reaction chamber 126. The precursor compound 108 may be a volatile liquid or a solid. The dissociation of the precursor 108 may occur in a vapor phase, a liquid phase, or a solid phase. An interaction reaction with the surface of the substrate 104 may occur on the surface of the substrate 104 in contact with the vapor phase. The precursor compound 108 may also be a gas, in which case it is not necessary to evaporate the volatile precursor compound 108 to make the precursor compound 108 a vapor phase. The gas containing the precursor compound 108 may be fed into the reaction chamber 126 through a tube (not shown).

A radiation emitter (112) emits EM radiation into the chamber (126). The radiation emitter 112 may emit, for example, 100 to 400 nm of UV radiation. The radiation emitters 112 may be disposed in the reaction chamber 126. The radiation emitter 126 may, on the other hand, be external to the reaction chamber 126 if the walls of the reaction chamber are at least partially transparent to the radiation.

In an exemplary embodiment, the precursor 108 is applied directly to the surface of the substrate 104 in the form of, for example, liquid or fine particulates (e.g., powder or nanoparticles). The dissociation reaction of the precursor compound 108 and the subsequent functionalization of the substrate 104 may proceed directly on the surface of the substrate 104. The reaction may also be catalyzed. For example, the reaction may be catalyzed by the surface of the substrate 104. In an exemplary embodiment, the catalyst is disposed in the system to facilitate or enable the catalyzed reaction.

Specifically, in the embodiment shown in FIG. 1, the precursor compound 108 is a volatile liquid contained in an open receiving vessel 110. The precursor compound 108 is vaporized onto its vapor.

The substrate 104 itself may be deposited on the mechanical support layer 102. For example, the substrate may comprise a TCO thin film (e.g., ITO) deposited on a glass substrate. The reaction chamber 126 isolates the substrate 104 from external contaminants and maintains the precursor vapor and the reactive species near the substrate 104.

The radiation emitter 112 may be operated to release the EM radiation 114 into the reaction chamber 126 to dissociate the halogen species from the halogen-containing precursor 108. The dissociation can be accomplished in a vapor phase, in a liquid phase (e.g., in the receiving vessel 110 or on the surface of the walls of the reaction chamber 126), in a solid phase, or on a surface of a substrate. An exemplary halogen containing volatile precursor compound is a dihalobenzene.

When the halogen species are chemically bonded to the substrate, a monolayer 106a begins to be formed. As can be seen from Fig. 1, a partial monolayer 106a corresponding to approximately half of the surface of the substrate 104 was formed. As will be described in further detail below, the surface properties of the substrate 104 can be tuned based on the surface coverage of the substrate 104 by the functionalizing species 106a.

As used herein, the term "monolayer" refers to a coating layer having approximately one atomic layer. It is understood that a slightly more or less layer than a monolayer is considered a monolayer. It is also understood that a single layer containing impurities, for example residual carbon, is considered as a single layer.

While the system of Figure 1 discloses the functionalization of a substrate with halogens, in some embodiments, the deposited species is carbon halide. The halogenated carbon molecules may form a polymeric structure when functionalized on the surface of the substrate. For example, a fluorocarbon film can be deposited on the surface of the substrate. A fluorocarbon film containing a C: F ratio that was set to be adjustable from 1: 3 to 3: 1 was achieved, which was confirmed by X-ray photoelectron spectroscopy (XPS). Higher or lower carbon to halogen ratios are possible. The XPS results indicated the presence of CF ₃ , CF ₂ , CF, C-CF and CH bonds. Some species, such as halocarbons, may react to form multiple layers of a halogenated carbon film, which can be several nanometers in thickness. The halogenated carbon film may be conductive or insulating. The work function of the surface varies depending on the amount and type of halogenated carbon.

To increase or decrease the hydrophobicity of the surface, other properties, including surface energy, may be varied. The surface can be functionalized using a mold to control the surface energy at a particular area on the surface. Surfaces with modified surface energies can interact more favorably with some species and interfere with their interaction with other species. For example, a hydrophobic surface can be a water bead, while a hydrophilic surface can be wetted with water. The functionalization of a particular region of the surface allows the functionalized region to react with one species and the unfunctionalized region to resist the reaction and vice versa. It is noted that about half of the monolayer is formed on the substrate 104, but less than a monolayer may be formed. For example, about 20% or more of the monolayer can be formed on the substrate.

Returning now to FIG. 2, although the system of FIG. 1 is shown, the partial monolayer 106a of FIG. 1 has been inhabited more than chemically bonded paper, as shown by 106b. The functionalization reaction may be carried out in the presence of at least one selected from the group consisting of the wavelength of electromagnetic radiation used to dissociate the halogen from the precursor, the intensity of the EM radiation, the temperature at which the reaction takes place, the precursor used, Lt; RTI ID = 0.0 > halogen. ≪ / RTI > The monolayer 106b continues to form on the substrate 104 as long as the halogen continues to react with the substrate 104. [

Returning now to Fig. 3, there is shown a substrate 104 having a monolayer 106c formed on a surface. As described above, the single layer 106c may have defects (not shown). It may be desirable to stop functionalizing the substrate 104 during the functionalization process prior to formation of the monolayer. The dissociation of the precursor 116 may be stopped by removing, blocking, or otherwise interrupting radiation from the radiation emitter 112. Once the emission of halogen atoms from the precursor stops, the surface coverage remains substantially constant. The ability to quiesce the functionalization reaction enables control over the degree to which the substrate 104 is functionalized at approximately the same time.

As is known, the functionalized substrate may contain contaminants. Removing organic contaminants from the surface can increase the work function of the substrate 104. After functionalizing the desired portion of the substrate 104, the substrate 104 may be cleaned. Specifically, the substrate 104 may be washed to remove contaminants deposited during the functionalization reaction. For example, the contaminant may comprise an organic compound originating from the precursor 108. In the case of organic precursors, the contaminants may react with UV generated ozone to form volatile compounds and flush them from the reaction chamber 126.

The functionalization process may not significantly increase the surface roughness of the substrate 104. [ In an exemplary embodiment, the ITO substrate is functionalized with chlorine. The atomic force microscope (AFM) was used to characterize the surface of the ultraviolet ozone treated ITO substrate and the chlorine-functionalized ITO substrate. The surface roughness represented by the arithmetic mean R _a was found to be 2.2 nm for the top surface and 1.9 nm after being functionalized as a monolayer of chlorine atoms. It can be seen that the monolayer is not a perfect monolayer and there may be some variability in coverage and contamination.

Turning now to FIG. 4, an XPS chart is shown showing the 2p core-level energy spectrum of chlorine-functionalized ITO superimposed on the 2p core-level spectrum of the InCl ₃ standard. The similarity between the InCl ₃ curve and the chlorine-functionalized ITO curve suggests that the indium-chlorine bond on the surface of the functionalized ITO substrate is in the same chemical state as the indium-chlorine bond in InCl ₃ .

Returning now to FIG. 5, a chart of approximate surface functionalization (as assessed by the 2p peak intensity of chlorine) for the reaction time is provided. Many ITO substrates were functionalized with chlorine using the EM radiation dissociation method. The duration of the functionalization of each substrate was selected from 0 to 10 minutes. The approximate surface coverage of the chlorine on the functionalized substrate was measured using XPS. As the reaction time of the functionalization process increases from 0 to 10 minutes, there is a proportional increase in the 2p peak intensity, demonstrating that the functionalization of the substrate can be increased by increasing the reaction time. In other words, for shorter reaction times, the substrate is less functional, i.e. less than a single layer is formed on the surface of the substrate. By selecting an appropriate duration of the functionalization reaction, the surface coverage can be tuned, for example, the surface coverage can be tuned for a predetermined reaction of the monolayer.

Figure 6 shows a band diagram of the work function of a standard ITO substrate with a top surface. The work function of the top ITO is approximately 4.7 eV (5 eV after cleaning), which is significantly lower than approximately 6 eV required to efficiently inject holes from the anode into the emissive layer of a typical organic electronic device.

Turning now to FIG. 7, an energy level diagram for an ITO substrate functionalized with a single layer of chlorine is provided. Each chlorine atom in the monolayer is chemically bonded to an indium atom in the ITO substrate, as evidenced by the XPS chart in Figure 4 above. The work function at the surface of the functionalized ITO electrode is significantly higher than that of the ultimate UV ozone treated ITO. For example, the work function of ITO functionalized with a single layer of chlorine may be approximately 6.1 eV compared to approximately 5 eV for man, UV ozonated ITO.

The increase in work function of the chlorinated substrate relative to the bare substrate can be attributed to the surface dipole induced by the chlorine atoms on the substrate of ITO. Thus, the functionalized species increases the work function of the ITO in proportion to the dipole moment due to the surface of the substrate. The desired increase in the work function of the electrode can be obtained by selecting the appropriate functionalizing species. Surprisingly, as described above, chlorine achieves the best dipole even though it is less negative than fluorine. Density functionality theory calculations indicate that the In-Cl bond length is greater than the In-F bond length, which results in a larger net dipole moment for chlorine compared to fluorine.

The work function of the TCO substrate can be tuned within a certain range by controlling the reaction time, for example by interrupting or blocking the radiation 114 from the radiation emitter 112. The concentration of the precursor compound can also be selected to tune the range. For example, by depositing less than a single layer on the surface of a substrate, the work function can be set to be lower than the work function of the substrate functionalized with the entire monolayer of species, but higher than that of the substrate surface.

Returning to FIG. 8, a chart illustrating the relationship between work function and surface coverage of chlorine on an ITO substrate as outlined from the chlorine 2p core-level XPS results is provided. The work function is roughly related to the surface functionalization of the ITO substrate. It should be noted that the chart of FIG. 8 is a rough approximation and only shows this relationship.

By way of example, the functionalization of about 15% of the monolayer corresponds to a work function of about 5.65 eV. The functionalization of approximately 95% of the monolayer corresponds to a work function of approximately 6.15 eV. Thus, the work function can be tuned according to the application by functionalizing the surface below a single layer. If a higher work function, for example about 6.1 eV, is desired, the surface can be functionalized with a near monolayer of chlorine. As noted above, it will be appreciated that the monolayer, or a portion of the monolayer, may be defective.

With regard to OLEDs, ITO is commonly used as an anode. The work function of the functionalized ITO anode may be tuned to coincide with the HOMO level of the organic hole transport material, as further described below.

Referring to FIG. 9, there is provided an XPS core-level spectrum of ITO functionalized with iodine, bromine and fluorine. As described above, the largest dipole is induced in the halogen-indium bond on the chlorine-functionalized ITO surface, thereby providing the maximum work function increase compared to ITO functionalized with other halogens.

As can be seen in Table 1 below, functionalization of various TCO surfaces is possible. UPS refers to ultraviolet photoelectron spectroscopy.

Experimental work function from XPS / UPS of various functionalized substrates Board Functionalized species The work function [eV] The work function [eV] of the functionalized substrate ITO Goat 4.7 6.1 FTO Fluorine 4.9 5.6 ZnO Goat 4.7 5.3 Au Goat 5.2 6.2

In addition to increasing the work function of the electrode, halogen functionalization increases the stability of the work function of the electrode relative to the ultraviolet ozone or O ₂ plasma treated TCO electrode. Returning to Fig. 10, there is provided a chart showing the stability of the work function of the ITO substrate functionalized with a single layer of chlorine relative to the bare ITO substrate in the presence of air. The surface of the substrate was treated with UV ozone for 15 minutes. As can be seen from Figure 10, the work function of the top electrode drops to about 0.1 eV for about 3 hours in the presence of air. In contrast, there is no substantial change in the Al function of the functionalized substrate. This demonstrates increased stability provided to the functionalized substrate. This may be advantageous in a production environment because the functionalized substrate may be left under atmospheric conditions for a period of time without affecting the work function of the substrate. Higher stability allows the substrate to be stored in air rather than under vacuum or inert gas. The stability of the functionalized substrate varies with the ambient environment, including ambient temperature and humidity.

Returning to Figure 11, a table is presented that illustrates the work function of various substrates after exposure to air for a period of time. Under the same conditions, after exposure to air, the work function of the functionalized substrate is substantially higher than the work function of the substrate under the same conditions.

Referring now to FIG. 12, there is provided a chart illustrating that the transmittance characteristics of the chlorine-functionalized ITO substrate are not substantially inferior to the transmittance characteristics of the master ITO substrate. The ITO layer was deposited on a transparent substrate. As can be seen from the chart, the transmittance is very similar over a wide wavelength range. Importantly, the curve is nearly indiscernible across the visible spectrum, which means that the chlorine-functionalized ITO anode can be used in an organic optoelectronic device without increasing the attenuation of light transmitted through the anode compared to the case of a bare ITO anode .

Returning to Fig. 13, there is provided a spectrum of an ultraviolet lamp used in the above example to functionalize an ITO substrate. Specifically, the spectrum corresponds to that of the PL16-110 Photo Surface Processing Chamber (Sen Lights (R)). A wavelength corresponding to the cutoff wavelength of Pyrex (trademark) glass that can be used as a reaction chamber is also provided.

The conductivity of the chlorine-functionalized ITO substrate is also not substantially inferior to the conductivity of the top ITO substrate. When measured with a four-terminal probe, the sheet resistance of an exemplary chlorine-functionalized ITO substrate is 18.2 ohms / square compared to 18.1 ohms / square for the top ITO substrate.

One use of a transparent conductive substrate, for example an ITO substrate, functionalized to have a high work function is the use of the substrate in an organic electronic device. Functioning the surface of the ITO substrate with a halogen species to increase the work function of the ITO substrate can reduce the hole injection blocking layer. The reduction in the hole injection blocking layer improves the hole injection efficiency in the OLED, thereby reducing the amount of voltage required to induce current in the device.

Although functionalized TCO substrates are shown in an exemplary OLED structure, it will be appreciated that other OLED structures may also utilize functionalized TCO substrates. Still further, other types of electronic devices may include functionalized TCO substrates.

Figure 14 shows an exemplary energy diagram of an embodiment of an OLED using a transparent conductive substrate from the prior art. The ITO layer 1280 is typically formed on a transparent substrate used as an anode. Holes are injected from the anode 1280 into the hole injection layer (HIL) 1282 and then into the hole transport layer (HTL) 1284 through the electron blocking layer (EBL) 1286 to the light emitting thin film layer 1292 . At the same time, electrons are injected through the cathode 1298, transported through the electron transport layer (ETL) 1296, through the hole blocking layer (HBL) 1294, and recombined with the holes in the light emitting thin film layer to emit photons . The photons emitted into the thin film layer then pass through the ITO layer 1280 and any transparent substrate supporting the ITO layer 1280. A faint line 1290 is provided to indicate the relative work function of the chlorine-functionalized ITO layer, which is remarkably well aligned with the emissive layer.

FIG. 15 is an energy level diagram for a simplified phosphorescent OLED including a chlorine-functionalized ITO electrode 1380. FIG. At a lower barrier layer height, holes can be injected more efficiently from the anode. As can be seen from the above diagram, the height of the hole injection blocking layer (which varies with the difference between the HOMO of the emitting layer and the work function of the ITO electrode 1380) is relatively low for chlorine functionalized electrodes. This low hole injection blocking layer may allow the electrode to be implanted directly into the host 1284, thereby making the host and the HTL 1283 the same material. Since the chlorine-functionalized anode is closely aligned with the HOMO level of the HTL 1283, the HIL layer 1282 is not required. In contrast, the bare ITO electrode 1280 has a high injection blocking layer, which makes it ineffective to inject holes without an intermediate HIL layer, as shown in Fig. When the HTL and ETL are selected to have appropriate energy levels, the EBL and HBL can also be removed, as will be appreciated by those skilled in the art.

Referring now to FIG. 16, there is provided a UPS chart illustrating the relationship between the work function of the anode and the barrier layer height for holes in an OLED device. It can be seen that increasing the work function of the electrode using halogen functionalization reduces the height of the hole injection blocking layer.

In an exemplary embodiment, chlorine-functionalized ITO anodes were prepared for use in phosphorescent green-emitting OLEDs. Another OLED comprising an OLED containing a chlorine-functionalized ITO anode and an ITO anode with a top UV ozone treatment was applied to a base of 10 ^-8 Torr on commercially patterned ITO coated glass (25 mm x 25 mm) Pressure was produced with the Kurt J. Lesker LUMINOS (trademark) cluster tool. The ITO substrate was washed with deionized water (DI), acetone, and a standard regimen of Alconox (TM) dissolved in methanol. The ITO substrate was then treated with UV ozone treatment for 3 minutes in a PL16-110 photo support processing chamber (Senryts).

Chlorine-functionalized ITO was prepared by functionalizing the surface of the ITO substrate for 10 minutes in a Pyrex (trademark) Petri dish with 0.2 ml 1,2-dichlorobenzene as precursor compound according to the method described in Fig. A Pyrex (trademark) receiver was used as the chamber, and a UV light source was placed outside the chamber. The transmission spectrum of Pyrex (trademark) is provided in FIG. 24a, and the spectrum of the UV lamp is provided in FIG. 24b. Once the functionalization was completed, the ITO substrate was treated with UV ozone for 3 minutes.

The organic layer and LiF cathode were thermally deposited from an alumina crucible in a dedicated organic chamber. The Al layer was deposited in a separate dedicated metal deposition chamber from a boron nitride crucible without vacuum breakdown. All layers were patterned using a stainless steel shadow mask to define the device structure. The active area for all devices was 2 mm2.

The standard device structure is as follows: Anode / CBP (35 nm) / CBP: Ir (ppy) ₂ (acac) (15 nm, 8%) / TPBi (65 nm) / LiF (1 nm) / Al ), Wherein Ir (ppy) ₂ (acac) is bis (2-phenylpyridine) (acetylacetonate) iridium (III) and TPBi is 2,2 ', 2 "- (1,3,5- Tril) -tris (1-phenyl-1-H-benzimidazole).

The energy level diagram 1200 of the exemplary phosphorescent OLED structure is provided in FIG. The chlorine-functionalized ITO anode 1202 has a significantly higher work function than the top UV ozone treated ITO anode 1206. Thus, the chlorine-functionalized anode can be more efficiently injected into the CBP layer 1204 because the HOMO level of the CBP layer 1204 is well aligned with the work-function of the chlorine-functionalized ITO anode . The Ir (ppy) ₂ (acac) layer 1208 may be doped into the CBP layer 1204. The TPBi layer 1210 is in electrical communication with the LiF / Al cathode layer 1212 and the Ir (ppy) 2 (acac) layer 1208.

18 is a diagram showing current-voltage characteristics of the exemplary device of FIG. As can be seen, as the processing time increases to the point at which the monolayer is formed, the voltage required to drive the current decreases. Thus, when a monolayer of chlorine is functionalized on the surface of the ITO anode used in the exemplary OLED device, the voltage required for operation of the OLED can be significantly reduced. As can be seen from FIG. 18, the voltage can be reduced to about 4 V at an equivalent current density.

19 is a chart of the current efficiency of the exemplary OLED device of FIG. 17 that includes a chlorine-functionalized anode, with respect to the luminescence generated from a prior art OLED reference device. Specifically, the to OLED device comprises a UV ozone treatment anode having the following structure: an anode / PEDOT: PSS (5 ㎚) / α-NPD (35 ㎚) / CBP: Ir (ppy) 2 (acac) ( NPN is N, N'-bis (naphthalene-1-yl) -N, N'-bis (naphthalene- Bis (phenyl) -benzidine. The PEDOT: PSS (5 nm) / alpha -NPD (35 nm) layer in the reference device was used to inject holes from the rod UV ozonated ITO anode into the CBP: Ir (ppy) ₂ (acac) need. From FIG. 19 it can be seen that the chlorine-functionalized anode increases the current efficiency for a reference OLED comprising a top UV ozone treated electrode. In particular, at high luminescence, the OLED comprising the functionalized anode is significantly more efficient.

Returning to FIG. 20, the current efficiency and external quantum efficiency (EQE) of a phosphorescent OLED including a chlorinated anode is provided. The phosphorescent OLED has a high maximum current efficiency of 93.5 cd / A at 400 cd / m 2, which corresponds to a maximum EQE of 24.7%. At 10,000 cd / m 2, the current efficiency and EQE are still relatively high at 79.6 cd / A and 21%, respectively. Returning to Fig. 21, the exemplary OLED of Fig. 17 comprising a chlorinated ITO anode is compared to a device fabricated using methods found in the prior art. As can be seen, an OLED comprising the chlorine-functionalized anode can be made significantly simpler with respect to device layers and materials, and the OLED can additionally exhibit significantly higher external quantum efficiency.

Referring now back to FIG. 22, a chart is presented showing the change in measured luminescence in vacuum for an exemplary OLED having the following structure: Electrode / CuPc (25 nm) / alpha -NPD (45 nm) / CBP: Ir _{ppy) 2 (acac) (15} ㎚, 8%) / TPBi (10 ㎚) / Alq 3 (45 ㎚) / LiF (1 ㎚) / Al (100 ㎚), where CuPc is a copper phthalocyanine. As can be seen, the luminescence of OLEDs containing ITO anode functionalized with chlorine is higher than OLEDs containing ITO anode treated with man UV ozone after several hours of operation. This proves that OLEDs containing ITO anode maintain relatively higher luminescence over time.

In another exemplary embodiment, a fluorescent green OLED was fabricated according to the same procedure as for the outlined phosphorescent OLED. Standard device structure of the OLED is as follows: anode / CBP (50 ㎚) / Alq 3: C545T (30 ㎚, 1%) / Alq 3 (15 ㎚) / LiF (1 ㎚) / Al (100 ㎚), Wherein CBP is 4,4'-bis (carbazol-9-yl) biphenyl, Alq ₃ is tris (8-hydroxy-quinolinato) aluminum, C545T is 2,3,6,7- Tetrahydro-1,1,7,7-tetramethyl-1H, 5H, 11H-10- (2-benzothiazolyl) quinolizino [9,9a, 1gh] coumarin.

An energy level diagram 900 of the fluorescent OLED structure is provided in FIG. The numeral 902 refers to a chlorine-functionalized ITO anode, which has a significantly higher work function than the top ITO anode 906. Thus, the chlorine-functionalized anode 902 can be formed in the CBP layer 904 since the HOMO level of the CBP layer 904 is well aligned with the work function of the chlorine-functionalized ITO anode 902 Better holes can be injected. The OLED is Alq _3: include C545T layer 908 and Alq ₃ layer 910 (which is in communication with the LiF / Al cathode 912) also.

The HOMO level of the CBP layer in contact with the anode is approximately 6.1 eV. When measured by ultraviolet photoelectron spectroscopy (UPS), after being treated with ozone, the work function of the functionalized anode is approximately 6.1 eV and the work function of the manned anode is approximately 5.0 eV. The work function of the manned anode is too low to efficiently inject holes into the OLED while the work function of the functionalized anode is more aligned with the HOMO level of the CBP layer.

24 is a chart showing the current-voltage characteristics of a fluorescent green OLED comprising a chlorine-functionalized ITO anode for a fluorescent green OLED of the same structure comprising an ultraviolet-ozone treated ITO anode. As can be seen from FIG. 24, the voltage required to achieve a particular current density is significantly lower for an OLED comprising such a chlorine-functionalized anode.

Specifically, the current density of an OLED device comprising the functionalized electrode is greatly increased with a driving voltage exceeding 6 volts. At 10 volts, the current density of the OLED including the chlorine-functionalized ITO anode is approximately 300 mA / cm2. In contrast, the current density of the OLED including the top ITO electrode is negligible. The higher current density of OLEDs comprising the chlorine-functionalized ITO anode demonstrates that the higher work function enables more efficient injection of holes into organic hole transport materials with deep HOMO levels.

A major advantage of aligning the work function of the ITO anode with the HOMO of the CBP layer is that the power efficiency of the OLED is increased; That is, the light output per electric input unit increases. Referring to Fig. 25, a chart showing the current and power efficiency of the OLED device discussed above is provided. The device with the top ITO anode has lower power efficiency and lower current efficiency due to insufficient hole injection from the top ITO anode to the deep 6.1 eV HOMO of CBP. Devices with chlorine-functionalized ITO anode have much higher efficiency, with a maximum current efficiency of 23 cd / A at a luminance of approximately 1000 cd / m 2, while approximately 18 cd / A for the top ITO anode.

Similarly, the power efficiency of an OLED including a chlorine-functionalized ITO anode is approximately 12 Im / W at 1000 cd / m < 2 >, while the power efficiency of an OLED including the top ITO anode is at a luminance of 1000 cd / It is approximately 5 Im / W. The increased power efficiency suggests that the chlorination of the ITO anode has a significant effect on power efficiency.

Considering the improved alignment of the work function of the chlorinated ITO anode and the HOMO of the CBP layer, this alignment leads to a number of HIL and HTL typically required for such device fabrication without loss of unacceptable efficiency can do. Since it is possible to reduce the number of process steps necessary for manufacturing the OLED device, thereby increasing the manufacturing yield of the OLED device and reducing the cost associated with its production, Do.

In this example, the halogen-functionalized electrode provides little in-line impedance to the device. For example, chlorine-functionalized ITO anodes were prepared for use in single-carrier hole-only organic devices. The structure of the device is as follows: anode /? -NPD (536 nm) / Ag (50 nm). A first apparatus comprising the top UV ozone treated anode was applied to a second apparatus having a UV ozone treated ITO anode coated with 1 nm vacuum deposited MoO ₃ and a third apparatus comprising a chlorine-functionalized ITO anode . The height of the hole injection blocking layer between the anode and the? -NPD organic layer was measured for each device using a UPS. The hole injection blocking layer height was 0.6 eV for the ultraviolet UV ozonated ITO, 0.45 eV for the UV ozone treated ITO coated with 1 nm vacuum deposited MoO ₃ and 0.45 eV for the chlorinated ITO . The performance of the device with UV ozone-treated ITO coated with the 1 nm MoO ₃ could initially be expected to be the same as with the device with the chlorine-functionalized ITO because the barrier height to holes Is the same in both devices.

Fig. 26 is a diagram showing the current-voltage characteristics of the exemplary single-carrier hole-only organic device described above. The current density at a given voltage is highest in the case of devices having the chlorine-functionalized ITO anode. Nevertheless, the device with UV ozone-treated ITO coated with 1 nm of MoO ₃ , due to its lower hole injection blocking layer height, still has a higher voltage at any given voltage than the device with the most UV ozone treated ITO anode High current density. Unexpectedly, even though the current density of the device with the chlorine-functionalized ITO anode is equal to that of a device with a UV ozone treated ITO anode coated with 1 nm MoO ₃ , despite the same barrier layer height for holes, . In the device with the UV ozone treated ITO anode coated with the 1 nm MoO ₃ , the lower current density indicates that the MoO 3 layer introduces a series impedance into the device.

As described above, the substrate can also be functionalized with plasma. 27 is a plasma system for functionalizing a substrate. The system includes a grounded (2612) reaction chamber 2608. The system may include a plurality of rods 2620 that support a substrate support 2626 upon which the substrate 2652 may rest. The substrate 2652 is placed in electrical communication with the substrate support 2626. The substrate 2652 is deposited on a non-conductive mechanical support 2650, e.g., glass. A high energy plasma shield 2624 is also provided. The plasma shield 2624 may also be supported by the rod 2620. The plasma shield 2624 is also grounded.

A radio frequency (RF) power source 2610 provides power to the power supply electrode 2611. The reaction chamber 2608 includes an inlet 2614 through which a gas containing a precursor can be pumped and an outlet 2616 through which the vacuum chamber can be evacuated by a vacuum pump. The precursor may be a liquid or a gas. When the power supply electrode 1611 is powered by the RF power source 2610, a plasma is generated between the power supply electrode 1611 and the grounded portion of the system including the reaction chamber 2608 . In particular, the highest energy plasma occurs at the highest electric field region (which may be between the power supply electrode 2611 and the plasma shield 2624). However, a plasma may also occur anywhere in the chamber 2608. [

It will be appreciated that a variety of plasma generation methods may be used to generate halogen-containing plasmas, including glow discharge substrate plasmas. It will also be appreciated that the plasma can be used with UV light treatment to functionalize the substrate. For example, dichlorobenzene diluted with argon gas can be used with ultraviolet light or radio frequency electromagnetic radiation to functionalize the substrate as a halogen species.

The plasma causes dissociation of any precursor in the reaction chamber. The dissociated precursor may then react with the surface of the substrate 2652 to begin forming a monolayer 2654. As is well known, particles in the plasma may have significant kinetic energy. The plasma shield 2624 prevents plasma with the highest kinetic energy from impinging directly on the surface of the substrate 2652, thereby reducing the corrosive effect on the substrate 2652.

As an example, the chamber can be pumped down to about 250 mTorr and 1,2-dichlorobenzene can leak as a precursor to the ITO substrate. The substrate can be processed for approximately 5 minutes. Corrosion of the substrate was minimized by placing the substrate behind the plasma shield 2624. The functionalized substrate may be washed to remove residual contaminants.

Another exemplary plasma system for functionalizing the substrate is provided in Fig. In the example of FIG. 28, an RF power source 2610 is connected to the substrate support 2626 and thus to the substrate 2652 itself. And the grounded electrode 2711 is placed in an arrangement parallel to the substrate 2652. When the power source 2610 is activated, a plasma is generated between the grounded electrode 2711 and the substrate 2652. As outlined above, the plasma causes dissociation of any precursor in the reaction chamber. The dissociated precursor then reacts with the surface of the substrate 2652 to begin to form a single layer 2654. In order to alleviate any corrosive effect of the plasma, the gas comprising the precursor may be diluted with a carrier gas as outlined below.

It is known that a variety of known precursor-containing gases may be used. For example, other halogen-containing precursors or fluorocarbon-containing precursors can be used. Exemplary precursors include bromine, chlorine, tri-chloroethane, dichlorobenzene, halogenated alkanes, halogenated alkenes, and halogenated aromatic compounds. Typical chlorinated precursors are chloromethane, dichloromethane, tetrachloromethane, perchlorethylene, tetrachlorethylene, 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, carbon tetrachloride, Chloroform, methylene chloride, trichlorethylene, methyl chloroform, 1,1,1-trichloroethane, 1,2,3-trichloropropane, ethylene dichloride, dichloropropane, dichlorobenzene, propylene dichloride, 1,2-dichloroethylene, 1,1-dichloroethane, and the like. The precursor may also comprise a halogen-containing polymer. An inorganic precursor may also be used. Examples of inorganic precursors include pure halogen gases, halogen halides, boron halides, sulfur halides and phosphorus halides.

Advantageously, the difference in ionization energy between the precursor and the carrier gas can be used to affect the amount of halogen radicals or ions produced using electromagnetic radiation. For example, in a plasma-based process using RF electromagnetic radiation, the chlorine gas can ionize more readily than the argon gas. Thus, although the concentration of chlorine in argon may be relatively low, it may be, for example, 1%, but the concentration of active ionized chlorine species in the plasma may be much larger.

The precursor may comprise a mixture of various halogen-containing precursors. An oxidant, such as oxygen, may also be added to the diluted precursor mixture to increase the removal of carbon impurities from the surface of the substrate.

Plasma functionalization of the substrate can be used in processes where UV treatment can damage the substrate or otherwise adversely affect the substrate. For example, in some cases, the thin film transistor (TFT) on the substrate may be damaged by UV radiation. Specifically, the UV radiation may degrade the semiconductor substrate including the silicon substrate and the indium gallium indium gallium (IGZO) substrate.

The functionalization of the substrate using the plasma can be beneficial because the plasma treatment is typically performed under vacuum, as in many other steps of OLED fabrication. The functionalization process itself can be performed in the same operation line as the other steps of OLED fabrication, without increasing the substantial pressure, thereby reducing the time required to perform the functionalization step. Furthermore, the substrate may be functionalized using conventional plasma equipment. Conventional plasma equipment can also be used for large substrates including so-called "8th generation" substrates (2.2 m x 2.5 m).

In another example, the plasma may use a carrier gas to reduce the concentration of the halogen-containing species. A gas having a lower concentration of halogen-containing species may be safer to handle and further reduce the corrosive effect of the plasma. For example, pure chlorine gas is highly toxic and corrosive, and is typically stored in a pressurized cylinder. Carrier gases, such as chlorine gas diluted with 1% chlorine gas in an argon carrier, are less toxic and less corrosive.

By way of example, the carrier gas may comprise an inert gas, such as argon. Other exemplary carrier gases include helium, neon, krypton, and xenon. The carrier gas may comprise a mixture of different ratios of these gases.

The carrier gas may account for less than about 99.9% of the total gas volume. For example, the halogen-containing precursor may be introduced at a concentration of about 0.1%, 1%, 5%, or 10%, with the remainder being occupied by one or more carrier gases. The concentration of the halogen-containing precursor may be selected according to the desired processing time, the zone coverage of the substrate, the reactivity of the halogen with the substrate, or various other process parameters. The lower concentration of the halogen-containing precursor plasma has a significantly lower corrosion rate than the higher concentration of the same species.

For example, the concentration of the gas containing the halogen-containing precursor may be 5% in 95% carrier gas. As a specific example, a mixture of 5% dichlorobenzene and 95% argon can be used.

As an example, an ITO substrate coated on a glass sheet was functionalized with a chlorine gas diluted in argon carrier gas at a concentration of about 1% as shown below.

The ITO substrate was washed with detergent, acetone and methanol and loaded into a commercial Advanced Energy reactive ion corrosion system. The process chamber was pumped down to a base pressure of 10-2 Torr using a scroll-pump. Chlorine gas diluted in argon at a concentration of 1% was leached into the processing chamber at a pressure of 1 to 10 mTorr using a mass flow controller. Approximately 50 W of forward radio frequency power at 13.56 MHz was applied to the processing chamber to form chlorine and argon plasma. The substrate was treated for 10 seconds. It will be appreciated that other processing times, operating pressures, and plasma power may be used. In this example, a relatively low power was chosen to minimize corrosion of the sample.

The work function of the treated sample was measured using x-ray photoelectron spectroscopy and found to be > 6.0 eV. The Cl 2p core-level of chlorine on the surface of the sample suggests the formation of an In-Cl bond. The surface roughness of the sample measured using an atomic force microscope was found to be about 2 nm, which is substantially the same as the substrate before the plasma treatment.

An organic light emitting diode having a structure of CBP (35 nm) / CBP: Ir (ppy) 2 (acac) (15 nm, 8%) / TPBi (65 nm) / LiF (132 nm) / Al Functionalized ITO substrate. The OLED exhibited a relatively high external quantum efficiency of 24%, demonstrating that it is possible to produce electrodes for organic optoelectronic devices such as OLEDs using such processes. Although ITO is used, it will be appreciated that other substrates may be functionalized with a halogen using similar processes, for example, other transparent conducting films (TCO), metal oxides or metals.

Processes similar to those described above can also be used for functionalization with other halogens, or for functionalizing the surface with a chalcogenide, for example sulfur from a sulfur-containing precursor diluted in a carrier gas. It is also possible to functionalize the substrate with chlorine using RIE.

As described above, a metal halide can be used as a precursor. Exemplary processes for functionalization of ITO substrates using metal halide precursors are described below. Specifically, an ITO substrate was functionalized using a vapor phase in Example 1, chlorine from a metal chloride precursor in a liquid phase in Example 2, and an organic precursor in Example 3. [

Example 1

The ITO coated glass substrate was ultrasonically washed with a standard program of Alconox (TM) dissolved in deionized water (DI), acetone and methanol. The ITO substrate was then treated with UV ozone treatment for 3 minutes in a PL16-110 photo-surface processing chamber (Senryts).

The surface of the ITO substrate was exposed to InCl ₃ in a vapor phase in a vacuum chamber by sublimation of InCl ₃ powder from an alumina crucible. The exposure was like depositing a layer of InCl ₃ about 5 Å thick on the surface of the substrate as measured by a quartz oscillator balance.

The ITO substrate was treated in a PL16-110 photo-surface processing chamber for 3 minutes using UV ozone treatment.

Example 2

The ITO coated glass substrate was ultrasonically washed with a standard program of Alconox (TM) dissolved in deionized water (DI), acetone and methanol. The ITO substrate was then treated in a PL16-110 photo-surface processing chamber for 3 minutes using UV ozone treatment.

The surface of the ITO substrate was exposed to a dilute solution of InCl ₃ dissolved in ethanol by spin-coating the solution on the surface of the substrate at 2000 rpm.

The ITO substrate was treated in a PL16-110 photo-surface processing chamber for 3 minutes using UV ozone treatment.

Example 3

The ITO coated glass substrate was ultrasonically washed with a standard program of Alconox (TM) dissolved in deionized water (DI), acetone and methanol. The ITO substrate was then treated in a PL16-110 photo-surface processing chamber for 3 minutes using UV ozone treatment.

The surface of the ITO substrate was treated with 1,2-dichlorobenzene (DCB) vapor in a closed Pyrex (R) Petri dish under UV irradiation for 10 minutes in a PL16-110 photo-surface processing chamber.

The ITO substrate was treated in a PL16-110 photo-surface processing chamber for 3 minutes using UV ozone treatment.

The chemical composition and work function of all of the substrates were characterized using x-ray photoelectron spectroscopy (XPS) in a PHI 5500 Multi-Technique System using monochromatic Al K _alpha (hv = 1486.7 eV) Respectively. An x-ray photoelectron spectroscopy (XPS) spectrum showing the chemical state of chlorine bound to the surface using the three example procedures described above is provided in FIG. Specifically, the XPS spectrum was measured using three different chlorinated functionalized ITO substrates, which were functionalized using InCl ₃ vapor (Example 1), InCl _{3 in} solution (Example 2), and DCB vapor using UV light 2p < / RTI > core-level energy spectrum. The similarity between Cl 2p core-level spectra for the three different chlorine functionalized substrates suggests that the surface chemistry conditions of the three samples are similar.

As such, Figure 28 refers to the reaction of InCl ₃ and dissolving the surface of the ITO in the InCl ₃ solution and in the vapor phase can hwahal reacting the surface with chlorine. The work function of each of the three chlorine-functionalized ITO substrates can be estimated to be 6.05 ± 0.05 eV. Therefore, InCl ₃ and the surface chemical vapor state, and the work function of the ITO substrate functionalized with InCl ₃ was dissolved in the solution is similar to the functionalized using dichlorobenzene and UV light ITO substrate.

It will be appreciated that substrates functionalized using metal halides are expected to act in the same manner when used in devices, e.g., OLEDs, because the ITO substrates described above provide a similar chemical structure.

Potential applications of organic optoelectronic devices including substrates functionalized according to the methods disclosed herein include organic photoelectric conversion engineering, OLEDs, organic thin film transistors, and biomedical devices. Although reference has been made to organic electronic devices including TCO functionalized electrodes, it will be appreciated that inorganic electronic devices may also include functionalized TCO electrodes. For example, an LCD electrode can be functionalized using the process as disclosed in the present invention.

Another potential application of the substrate functionalized according to the method described above comprises functionalizing the substrate to control the surface energy and optionally template the growth of the material on the functionalized substrate.

Although embodiments have been provided that initiate functionalization of a TCO substrate, it will be appreciated that other types of substrates may be functionalized. For example, metals, polymers (including conducting polymers), and ceramics can be functionalized into one species using processes such as those described herein.

It will be appreciated that although an exemplary method of functionalizing the substrate is provided above, the substrates may be functionalized using methods other than those described above. For example, it will be appreciated that an electrode comprising a TCO substrate can be functionalized below approximately a single layer of a halogen species using methods other than those described above.

While the foregoing is directed to some specific illustrative embodiments, various modifications thereof, without departing from the scope of the appended claims, will be apparent to those skilled in the art.

Claims (27)

As a method of increasing the work function of the electrode,
Obtaining a negative species from the precursor using electromagnetic radiation;
Reacting the surface of the electrode with the negatively charged species
≪ / RTI > The method according to claim 1,
Wherein the negative paper is halogen. The method according to claim 1,
Wherein the electromagnetic radiation has a wavelength of at least 100 nm. The method according to claim 1,
Wherein the electromagnetic radiation has a wavelength of less than 400 nm. The method according to claim 1,
And cleaning the surface of the electrode. The method according to claim 1,
Wherein the electrode is a transparent conducting film. The method according to claim 6,
Wherein the transparent conductive film is ITO. The method according to claim 1,
A method of selecting a negatively charged species so that an electrode of a predetermined work function is obtained. The method according to claim 1,
Wherein the surface coverage of the species is selected such that an electrode of a predetermined work function is obtained. 3. The method of claim 2,
A method for functionalizing a substrate substantially below a single layer of halogen. 11. The method of claim 10,
Wherein the halogen is chlorine. The method according to claim 1,
Wherein the precursor is a volatile liquid. The method according to claim 1,
Wherein the precursor is a gas. The method according to claim 1,
A method for activating a substrate to increase its stability in air. An electrode comprising a substrate functionalized according to the method of claim 1. An organic electronic device comprising the electrode of claim 15. For use as a system for chemically functionalizing a substrate with one species,
The system
A reaction chamber;
A radiation emitter operable to emit electromagnetic radiation into the reaction chamber,
Said reaction chamber being operable to receive a precursor of said species and a substrate; Wherein the electromagnetic radiation generates radicals from the species precursor and chemically bonds the substrate. 18. The method of claim 17,
Wherein the radiation emitter emits radiation having a wavelength between 100 nm and 400 nm. 20. The method of claim 19,
The radiation emitter is outside the reaction chamber;
Wherein the reaction chamber is operable to at least partially transmit ultraviolet radiation from the radiation emitter
The purpose of the system. As a method of increasing the work function of the electrode,
Obtaining chlorine from the precursor using plasma;
Reacting the surface of the electrode with the chlorine to form about 20% or more of the chlorine monolayer
≪ / RTI > 21. The method of claim 20,
Wherein the surface of the electrode is reacted to a level not more than a single layer of chlorine. 21. The method of claim 20,
Wherein the substrate comprises a transparent conducting film. 23. The method of claim 22,
Wherein the transparent conductive film is ITO. 22. The method of claim 21,
Wherein the surface coverage of the chlorine is selected such that an electrode of a predetermined work function is obtained. An electrode comprising a substrate functionalized at about 20% or more of a monolayer of halogen. 26. An organic electronic device comprising the electrode of claim 25. 27. The method of claim 26,
An organic electronic device comprising an organic light emitting diode.

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