DE10132329B4 - Light-emitting device and method for its production - Google Patents

Abstract

light emitting Device with an active area, in which light generation takes place or at whose interfaces light generation takes place, characterized in that the active region consists predominantly of a metal phosphonate structure or from several different metal phosphonate structures which forms part of an inorganic-organic composite layer are, with the metal ions in this coordinated with oxygen are and a distant order and / or proximity of the molecules and / or Atoms have.

Description

The The invention relates to a light emitting device and a method for their preparation according to the preamble and features of the claims 1 to 27.

A light emitting device may light due to different Emit processes. Two examples of light-emitting (or light-emitting) Devices are devices such as light emitting diodes (LEDs) or laser diodes (LDs) by applying an electrical voltage to the component, the necessary energy, which for the emission of Light is required. The LEDs are currently off Semiconductor materials such as gallium arsenide, gallium aluminum arsenide, Gallium phosphide, gallium arsenic phosphide, Aluminum indium gallium phosphide, indium gallium phosphide, gallium aluminum nitride, Gallium nitride or other alloy semiconductors. laser diodes need in addition to a typical LED structure, which is the conversion of electrical energy in light, additionally an arrangement that represents an optical resonator, the Laser effect, which allows lasing.

One third example for light-emitting devices form fluorescent components, which are exposed to high-energy radiation, e.g. UV light, X-ray or γ radiation or under Exposure of elementary particles such as α-particles, electrons, protons, Neutrons etc. emit light, which is a measure of the prevailing at the site of the device irradiance or particle density can serve. The emitted light intensity must be in this Quantum detected quantitatively by a suitable detection device which, together with the light-emitting component, which acting as a sensor, a detector for the corresponding high-energy Represents radiation.

Recent developments in the field of LEDs are no longer based exclusively on inorganic semiconductors but on organic materials. The LEDs thus produced are referred to as organic light-emitting diodes or devices (OLEDs). A typical structure for OLEDs can be described as follows: On an optically transparent substrate, for example a glass slide of suitable size, there is a semiconductor which is substantially transparent in the visible spectral range, such as indium tin oxide (ITO) or zinc oxide (ZnO). In this layer of the transparent semiconductor, here is exemplified ITO, brought by a suitable method to an organic semiconductor. This can be a conjugated polymer such as polyparaphenylene vinylene (PPV), which is spin-coated or doctored onto the ITO layer in a first process step by spin coating in the form of a still soluble precursor polymer , In a second step, the precursor polymer is converted into a conjugated, insoluble polymer (PPV). The first step of this process is carried out under normal pressure conditions and under a protective gas atmosphere to exclude harmful environments such as oxygen or water.

At the Use of low molecular weight organic semiconductors, e.g. triphenylamine or its derivatives, the deposition of the layer takes place in a vacuum by thermal evaporation of the organic substance which is on the ITO layer. This method has the advantage that oxygen and water can be largely excluded from the process.

typical Layer thicknesses which are set by spin coating or vapor deposition, range between 20 nm and 100 nm.

To Deposition of the organic semiconductor becomes this with a metal as aluminum (Al) steams, its work function in a certain relationship to the energetic position of the molecular levels or valence and conduction band of the organic semiconductor must be.

in the The result of this process is a so-called single-layer OLED, which contains only one layer of an active organic semiconductor. When investing an electrical voltage will be exceeded after a certain Voltage at the ITO electrode holes (holes) injected (anode), whereas at the Al electrode, which forms the cathode, electrons be injected into the organic semiconductor. Meet both types of charge carriers in the volume of the organic semiconductor or at its boundary layer to another medium on each other, so can a certain percentage the electrons with holes recombine with the emission of light.

If one builds the OLED as a sandwich of two different organic semiconductors (double-layer OLED), then under certain circumstances the efficiency of the OLED, ie the number of emitted quanta per injected charge carrier can be determined increase significantly. A typical example of a double-layer OLED, in addition to a typical hole conductor such as TPD still contains a so-called electron conductor such as the aluminum quinoline complex (Alq ₃ ) '. This two-layer OLED is prepared by first evaporating a TPD layer on the ITO layer in vacuo. This is followed by vapor deposition of the Alq ₃ on the TPD layer. Finally, the cathode is vapor-deposited on the Alq ₃ layer in the form of an Al layer or a layer of other base metals or alloys. The entire device is finally encapsulated to protect it against the destructive influence of oxygen and water. The first OLEDs based on vaporizable low molecular weight organic compounds are currently on the market, and more recently vaporizable or spin-coating and related techniques processable metal-organic complex compounds are used, which allow a particularly high efficiency of the device. These include various iridium complexes and metal phosphonate compounds , Polymer-based OLEDs are also in the market introduction phase. An organic laser diode based on a tetracene single crystal has also been demonstrated , where the verification of the decryption by other groups is still outstanding. Fluorescent building elements based on inorganic or organic materials which can serve as sensors for electromagnetic or particle radiation are known. As an example, dye-doped polymer fibers may be mentioned which are used as sensors for particle or γ radiation in the monitoring of reactors or accelerators. It is known that metal phosphonates can be applied in layers to support materials such as silicon or gold ,

The our investigation into the production of disorderly and ordered metal phosphonate layers, i.a. serve as catalysts can, led surprisingly to the result that metal phosphonate structures that are part of an inorganic-organic composite layer, wherein the metal ions in this are coordinated with oxygen and a long-range order and / or Close arrangement of the molecules and / or atoms, electroluminescence and fluorescence and / or Phosphorescence under the influence of different excitation forms such as electric current, electromagnetic fields or radiation or Show particle radiation.

Of the The invention is based on the object, light-emitting devices to develop on a new class of compounds, the metal phosphonate structures based on a novel principle. The advantages of these light-emitting devices in comparison consist of known light-emitting devices such as the OLEDs in that she can be much more stable than the latter and the described manufacturing process cost-effective can be designed as a known method. Also arise new Application areas.

Building an organic / inorganic light-emitting diode (OLED) on an ITO-coated glass substrate

The arrangement of the individual functional layers of the OLED is in 1 shown schematically. The structure is in principle in such a way that one on the transparent glass carrier 1 an ITO layer 4 , usually by sputtering, applying, which is then provided with an anchor layer. The anchor layer then allows the construction of multiple layers of cations and bifunctional anions (phosphonate layers) 2 , The multilayers are covered with a metal layer 3 or an electron transport layer (not shown) and metal layer 3 covered, with the metal layer 3 serves as an electrode. The last layer applied is a cover layer or a multilayer system for protection against the penetration of water, oxygen or other harmful substances or against other damaging external influences (not shown). The ITO coated glass slide used was cleaned in an ultrasonic bath for 30 minutes in a solution of three parts of 25% aqueous ammonia and one part of 30% H ₂ O ₂ . Thereafter, the coated glass slides were rinsed with Aqua-Bidest and dried at 393 K in a stream of nitrogen.

On the ITO glass slide prepared in this way, an anchor layer is produced as the 1st layer by immersing the support for 30 minutes at 25.degree. C. in a 0.5 to 1 mM aqueous solution of a bisphosphonic acid, such as 4,4'-diphenylbisphosphonic acid. The provided with the anchor layer ITO glass carrier is un The action of ultrasound washed with water and dried in a stream of nitrogen. In the following reaction steps, the structure of the metal bisphosphonate layers is repeated several times, as demonstrated by the example of zirconium-4,4'-diphenylbisphosphonate or 4,4 "-terphenyl bisphosphonate layers. The metal ions are used as 2 mM solutions of their salts and the bisphosphonate ions as 1 mM solutions in the form of the free acids or their ammonium salts in water.

Of the Layer construction is carried out by alternating immersion of the adhesive layer provided vehicle in a Zirkoniumchlorid- or 4,4'-Diphenylbisphosphonsäurelösung. The Temperature of the solutions can be between 0 ° C and 50 ° C chosen become. The exposure time is every 30 minutes. Between the individual diving steps is the coated carrier intensively washed with water under irradiation of sonoenergie.

By repeating the dipping and washing operations, any number of inorganic-organic composite layers can be deposited. In 2 schematically the chemical structure of an ordered zirconium bisphosphonate layer is shown as an example of such an inorganic-organic composite layer.

The metal ions are coordinated in the composite layers with oxygen and link in this way the corresponding phosphonates. By this linking principle, either amorphous or ordered phosphonate layers can be prepared. In ordered layers, the active organic components (chromophores) can occupy different angles relative to the substrate normal. In 3 there are two examples of chromophore orientation, the standing and the tilted arrangement.

there is the increase of the layer thickness per applied monolayer in Fall of the tilted arrangement less than in the case of standing Arrangement, since the cosine of the tilt angle τ is to be considered.

In 4 is the ellipsometrically measured thickness of an inorganic-organic composite multilayer based on zirconium-4,4'-terphenyl bisphosphonate depending on the number of individual layers reproduced. Thereafter, the layer thickness increases steadily with increasing number of individual layers. Out 4 results in an average thickness of the monolayer of about 1.8 nm.

comparing one the molecular size of the used Organobisphosphonsäuren with the increase in thickness of each layer grown, as in the example 4,4 '' - terphenylbisphosphonic acid, so it becomes clear that the organophosphonic almost perpendicular to the surface of the substrate. There are also other arrangements possible at an angle of typically 45 ° to 60 ° between the longitudinal axis of the molecule and layer normal.

Studies on the order in the layers have shown that the lateral order is often not perfect, since there are often domains with different orientations. This case is schematic in 5 shown. In this case, one does not deal with densely packed materials but with films that have a certain defect density. In the example, the composites are dried after application of 25 individual layers in a stream of nitrogen and coated in vacuum with a 50 to 500 nm thick aluminum layer by vapor deposition. Finally, the component is sealed with a glass plate, an inorganically filled lacquer or a multi-layer barrier system (eg alternately vapor-deposited layers of MgF ₂ and SiO ₂ ).

The fluorescence emission spectrum of a zirconium-4,4'-terphenyl bisphosphonate based multilayer shows 6 , With maximum fluorescence intensity at 386 nm, these layers are blue emitters. Strictly speaking, this example is a UV emitter. In 6 It can be clearly seen how the fluorescence intensity increases with the number of emitting fluorophores. The coordinating metal atoms do not quench the fluorescence.

The LED structure described in the example has the in 7 illustrated current-voltage-luminance characteristics. Clearly, an asymmetry of the current-voltage characteristic can be seen when changing the polarity of the applied voltage. This underlines the diode character of the fabricated structure. Blue electroluminescence occurs at both positive and negative voltages, but at different threshold voltages. Positive voltage means that the diode is forward biased and negative voltage means that the diode is reverse biased. The threshold voltage for the electroluminescence in the case of the "single-layer" diode presented in the example is +7.5 V in the forward direction and -10 V in the reverse direction. From the different increases of the electroluminescence intensity with the voltage, it becomes clear that the conversion efficiency is different in the forward direction than in the reverse direction. The emission spectrum of electroluminescence is similar to the spectrum of photoluminescence.

From the in 7 it is clear that the structure described in the example is a light-emitting device within the meaning of the claims of this patent message.

Explanations to the pictures

1 Structure of a Luminiszensdiode with inorganic-organic composite layer on ITO-coated glass substrate

2 : Schematic representation of the chemical structure of an ordered, zirconium-4,4'-diphenylbisphosphonate layer.

3 : Schematic representation of chromophore orientation in organic bisphosphonate layers; (a) standing arrangement (layer thickness D); (b) tilted arrangement (layer thickness Dcosτ, with τ - angle between molecular longitudinal axis and substrate normal)

4 : Ellipsometrically determined thickness of zirconium thphenylphosphonate composite multilayers as a function of the number of molecular layers

5 : Schematic representation of a bisphosphonate layer with domains of different orientation

6 : Fluorescence emission spectrum of multilayers based on zirconium 4,4'-terphenyl bisphosphonate for 20, 25 and 33 monolayers. The emission maximum is 386 nm.

7 : Current-voltage characteristic (solid line) and luminance (EL) voltage characteristic of a monolayer diode based on zirconium-4,4 "-terphenyl bisphosphonate.

Claims (27)

A light-emitting device having an active region in which light generation takes place or at whose interfaces light generation takes place, characterized in that the active region consists predominantly of a metal phosphonate structure or of several, different metal phosphonate structures which are part of an inorganic-organic composite layer, wherein the metal ions in this are coordinated with oxygen and have a long-range order and / or proximity of the molecules and / or atoms. Light-emitting device according to claim 1, characterized characterized in that electromagnetic radiation in one or several of the following spectral ranges with supply of Energy emitted: THz region, far infrared, infrared, near Infrared, visible area, ultraviolet. A light-emitting device according to any one of claims 1 or 2, characterized in that energy by applying an electrical DC and / or AC voltage and / or pulsed electrical Voltage of the device is supplied. A light-emitting device according to any one of claims 1 to 3, characterized in that the device by applying with a mold or simultaneous or sequential loading with several of the following electromagnetic forms Radiation energy supplied radio waves, microwaves, light of all spectral ranges, X-rays, Gamma radiation or with one or more forms of particle radiation - protons, Neutrons, electrons, alpha particles, all other elementary particles. A light-emitting device according to any one of claims 1 to 4, characterized in that energy by magnetic DC or alternating fields or by magnetic fields in combination with the excitation forms mentioned in claim 3 and / or claim 4 supplied becomes, A light-emitting device according to any one of claims 1 to 5, characterized in that the metal phosphonate structures consist of multilayers that are disordered. A light-emitting device according to any one of claims 1 to 6, characterized in that the metal phosphonate structures Metal ions such as titanium, zirconium, hafnium, germanium, tin, lead and / or lanthanides contain. Light-emitting device according to one of claims 1 to 7, characterized in that the metal phosphonate structures following organic compounds or molecular building blocks and / or derivatives thereof include: alkanes, alkenes, alkynes, paraphenylenes, Paraphenylenevinylenes, thiophenes, pyrroles, oxadiazoles, triazoles, thiazines, Quinolines, quinoxalines, triazines, aromatic amines, ferrocenes, Metal chelate complexes, acenes, phenazines, phenothiazines, phenoxazines, Perylene, rylenes, phthalocyanines, porphyrins, fullerenes, fullerene derivatives or silanes. Process for producing a light-emitting Device according to one of the claims 1 to 8, characterized in that the metal phosphonate structures, which are part of an inorganic-organic composite layer, wherein the metal ions in this are coordinated with oxygen, on a carrier material be fixed. Process for producing a light-emitting Device according to claim 9, characterized in that the support material a metal is. Method according to claim 9, characterized in that that this support material is a semiconductor. Method according to claim 9, characterized in that that this support material an electrical insulator is. Process according to claims 10 or 11, characterized that the metal phosphonate structure or the semiconductor and / or the metal or metals completely or partially covered. Method according to claim 13, characterized in that that the carrier material wholly or partly with a monolayer and / or with multilayers one or more other materials that do not contain metal phosphonates are covered, to which bound the metal phosphonate structure is. Method according to claim 13, characterized in that that the Metal phosphonate structure with one or more cover layers consisting of at least one Monolayer of another material, is provided. Method according to claim 15, characterized in that that the cover layer is a metal. Method according to claim 15, characterized in that that the Cover layer is a semiconductor. Method according to claim 15, characterized in that that the Cover layer is an electrical insulator. A light-emitting device according to any one of claims 1 to 8, characterized in that the metal phosphonate structure with at least one cover layer is provided, which has the function of a Encapsulation against the invasion of ambients in the active Area of the device exercises. Light emitting device according to claim 19, characterized in that at least one of the cover layers has the function of an optical reflector / mirror for light (ultraviolet, visible, infrared). A light-emitting device according to claim 19 or 20, characterized in that a plurality of cover layers a dielectric Mirror / reflector for Light (ultraviolet, visible, infrared) form. A light-emitting device according to claim 20 or 21, characterized in that at least two mirrors / reflectors are in an arrangement with each other, which is an optical resonator forms. A light-emitting device according to claim 22, characterized in that at least two mirrors / reflectors are in an arrangement with each other, an electrically or optically pumped laser forms. Light emitting device according to claim 19, characterized in that external mirrors / reflectors on or are mounted near the device such that an optical resonator arises, which increased shows spontaneous emission in a narrow spectral range or one Laser forms. Light emitting device according to claim 19, characterized in that the active cover layer through the mold or in combination with other materials a waveguide and / or forms an optical resonator, which increases spontaneous emission in one narrow spectral range or forms a laser. Method according to claim 9, characterized in that that the metal phosphonate structure or metal phosphonate structures on an optically transparent Fixed carrier material become. Method according to claim 9, characterized in that that the Metal phosphonate structure or metal phosphonate structures fixed on a support material such be that one optical waveguide is formed.