HK1072496B - Transparent, thermally stable light-emitting component comprising organic layers - Google Patents

Description

Light-transmitting, thermally stable light-emitting element comprising an organic layer

Technical Field

The invention relates to a light-transmitting and thermally stable light-emitting component comprising an organic layer, in particular a light-transmitting organic light-emitting diode according to the above-mentioned claim 1 or 2.

Background

Organic Light Emitting Diodes (OLEDs), which have been promising candidates for realizing large area displays since their demonstration by Tang et al at low operating voltages [ c.w. Tang et al, appl.phys.lett 51(21), 913(1987) ], consist of a set of thin film layers of organic material (typically 1nm to 1 μm) preferably deposited by vacuum evaporation or spin centrifugation of the solution, whereby the typical (characteristic) properties of such layers are transparent over 80% in the visible region of the spectrum, otherwise the OLEDs produce a slight external illumination effect by re-absorption, the contact characteristics of the organic layers with an anode and a cathode being realized by means of at least one transparent electrode (in most cases by a transparent oxide, such as indium-tin-oxide ITO) and a metal contact. Such light-transmissive contacts (e.g., ITO) are typically directly on the substrate. In the case of at least one metal contact, the OLED as a whole is opaque, but is instead reflective or scattering (via the corresponding modified layer, but not already of true OLED construction), the emission of the OLED taking place via the substrate situated on the bottom side in the case of a typical construction with a light-transmissive electrode on the substrate.

In the case of organic light-emitting diodes, upon application of an externally applied voltage, carriers (electrons on one side and holes on the other side) are injected from the contact points into the organic layer located between them, whereupon excitons (electron-hole pair) are formed in the active region, light is generated in the radiative recombination of the excitons and radiated out of the light-emitting diode.

The advantages of such organic-based components over conventional inorganic-based components (e.g. silicon, gallium arsenide semiconductors) are that it is possible to produce very large-area display devices (fluorescent screens), that the organic raw materials are relatively inexpensive (consume less material and energy) compared to inorganic materials, and that the process temperatures for attaching such materials to flexible substrates are lower compared to inorganic materials, which may lead to a new range of applications in display and lighting technology.

A conventional array of such elements comprising at least one non-light-transmissive electrode is formed in the order of one or more of the following layers:

1. the charge carrier body, the substrate,

2. the base electrode, which is typically light-transmissive for hole injection (positive electrode),

3. the injection of the hole layer is carried out,

4. transport hole layer (HTL)

5. Light radiation layer (EL)

6. Electronic Transmission Layer (ETL)

7. Electron injection layer

8. The cover electrode is mostly a metal with a lower work function, which can inject electrons (cathode),

9. and packaging to isolate the influence of the surrounding environment.

Usually several layers (except 2.5 and 8) are mostly omitted or one film layer can serve several properties.

In the film sequence described, the light is emitted via a transparent base electrode and a substrate, while the cover electrode is formed from a non-transparent metal layer, and the usual materials for the transparent base electrode are indium-tin-oxide (ITO) and oxide semiconductors of the same family as the hole-injecting contact (a transparent degenerated semiconductor), while non-noble metals such as aluminum (Al), magnesium (Mg), calcium (Ca) or magnesium-silver (Ag) mixed layers or combinations of these metals with a thin layer such as lithium fluoride (LiF) salts can be used as electron-injecting substances.

Generally, such OLEDs are opaque, but there are also applications where transparency is of importance, such as the manufacture of a display device that is transparent in the off-state, allowing the environment placed behind it to be observed, and which, in the case of access, allows the viewer to obtain information, it being possible to envisage applications that are possible in the display of car dials and personal displays that can be made without restricting their freedom of movement by displaying (for example head-on displays for monitoring management personnel), such transparent OLEDs forming the basis of transparent displays, for example from:

1.G.Gu，V.Bulovic，P.E.Burrows，S.R.Forrest，Appl.Phys.Lett.，68，2606(1996)，

2.G.Gu，V.Khalfin，S.R.Forrest，Appl.Phys.Lett.，73，2399(1998)，

3.G.Parthasarathy et al.，Appl.Phys.Lett.，72，2138(1997)，

4.G.Parthasarathy et al.，Adv.Mater.11，907(1997)，

g.gu, g.parthasarathy, s.r.forrest, appl.phys. Lett, 74, 305(1999), is known.

The transparency achieved in the introduction (1) is achieved by using conventional light-transmissive anode ITO as the base electrode (i.e. directly on the substrate), it being established here that when the ITO-anode is treated in a specific manner (e.g. ozone-sputtering, plasma integration) to increase the work function of the anode, it is suitable for the operating voltage of the OLED (e.g. c.c.wu et al, Appl phys.lett.70, 1348 (1997); g.gu.et al, Appl phys.lett.73, 2399(1998)). the work function of the ITO can be varied by, for example, ozonisation and/or oxygen-plasma ashing by about 4.2eV to 4.9eV, so that holes can be injected relatively efficiently from the ITO-anode to the hole transport layer, this pre-treatment of the ITO-anode being possible only when the anode is located directly on the substrate, this structure of the OLED being referred to as irreversible; while the OLED structure of the cathode on the substrate is referred to as a reversible structure. The combination of a thin semi-transparent layer of a non-noble metal (magnesium stabilised by incorporation of silver) and a conductive transparent layer of known ITO used as a cover electrode in citation (1) is necessarily applied because the work function of ITO is sufficiently high for efficient electron injection directly into the electron transport layer, thus enabling OLEDS to be produced using lower operating voltages. For this purpose, very thin magnesium interlayers are used, since the element formed by the thin metal interlayer is semi-transparent (covering the electrode transmittance of about 50-80%) and the transmittance, suitable as a fully transparent ITO anode, exceeds 90%, in the citation (1) an ITO contact is added to the metal interlayer by means of a sputter deposition process to ensure lateral conduction to the connection contacts around the OLED, with the consequence that the thickness of the metal interlayer cannot be lower than 7.5nm (citation (1)), otherwise sputtering damage to the underlying organic layers is excessive, this type of structure being also described in the following patents: US patent 5703436(s.r. forrestet al) filed on 1996.3.6; US patent 5757026(s.r. forrest et al) filed 1996.4.15; US patent 5969474(m.arai) in the 1997.10.24 application, in the citation (2), describes the superposition of two OLEDs described in the citation (1) and of a cathode, here a superposition of a green and a red OLED (stack OLED) is made, since both OLEDs are semi-transparent and the colors emitted can be selected in a targeted manner by means of a suitable voltage applied to the 3 rd electrode.

Another known way of achieving light-transmitting OLEDs is to improve the injection of electrons with an organic interlayer (quote 3-5), where an organic layer is located between the light-emitting layer (e.g. aluminum-triquinonolate, Alq3) and the light-transmitting electrode used as cathode (e.g. ITO), in most cases copper phthalocyanine dye (CuPc), which is a hole-transporting material itself, (hole mobility higher than electron mobility), and has the advantage of high thermal stability, that the sputtered capping electrode does not cause much damage to the organic layer underneath, and that such CuPc interlayers have the advantage of a small band gap (HOMO-highest occupied molecular orbital-distance to LuMO-lowest unoccupied molecular orbital) and at the same time the disadvantage of a relatively easy injection of electrons from ITO due to the low position of LuMO, but produce high absorption due to a small band gap in the visible region, the layer thickness of CuPc is limited to below 10 nm. Furthermore, it is difficult to inject electrons from CuPc into Alq3 or another emissive material because their LuMOs are generally higher, and it has been proposed by the founders that the light-transmissive cathode in the above-mentioned OLED is made of a basic earth-metal-oxide(s) (US patent 5457565(t. namiki) filed on 1993.11.18)For example LiO₂) The formation of the thin film layer instead of the CuPc layer improves the disadvantage that electrons are disadvantageously injected from the light-transmitting cathode to the light-emitting layer.

Another way of realizing a light-transmissive OLED (g.parthasarathy et Al, appl.phys.lett., 76, 2128(2000) world patent WO 01/67825Al (g.parthasarathy), application 2001.3.7, priority date 2000.3.9) is to add an electron transport layer (e.g. BCP-high electron mobility elctron) in contact with a light-transmissive cathode (e.g. ITO), or to have a 1nm thick film of pure alkali metal lithium (Li) between the light-emitting layer and the (< 10nm) thin electron transport layer or between the electron transport layer and the ITO cathode, which Li intermediate layer strongly increases the electron injection from the light-transmissive electrode, which phenomenon is explained by the diffusion of Li-atoms into the organic layer, which leads to the formation of a "doped" (semiconductor) highly conductive intermediate layer, in such a way that a light-transmissive contact layer (mostly ITO) is obtained.

The following points are certainly confirmed from the above work:

1. the choice of light-transmissive electrode is limited (mainly ITO or similar degenerate inorganic semiconductors).

2. The work function of the light-transmissive electrode is in principle advantageous for the injection of holes, but the anode must be specially treated to further reduce its work function.

3. Development work to date has been directed to finding a suitable intermediate layer to improve electron injection into the organic layer.

It is known that, in the case of light-emitting diodes of inorganic semiconductors, a thin space charge region can be achieved by a highly doped boundary layer, which, in the presence of an energy thermal barrier, effects effective carrier injection via tunneling, doping (as is customary for inorganic semiconductors) here being intended to influence the conductivity properties of the semiconductor layer by incorporation of additional atoms/molecules; the distinction between organic semiconductors is generally understood to mean the incorporation of special radiation molecules as dopants into the organic layers. Doping of organic materials is described in US patent 5693698 filed on 1991.2.12, but in practice problems arise in the energy balance of the different layers and lead to a reduction in the efficiency of light emitting diodes with doped layers.

Disclosure of Invention

The object of the invention is to provide a completely light-transmissive (> 70% transmission) organic light-emitting diode which can be operated at reduced operating voltages but has a high luminous efficiency, and at the same time all organic layers, in particular the light-emitting layers, are protected against damage during the production of the light-transmissive cover contacts, and the resulting component is stable (long-term stability at operating temperatures of 80 ℃).

According to the invention, which is combined with the features of claim 1, this object is achieved in that the hole transport layer containing an organic material of acceptor type is P-doped, the electron transport layer containing an organic material of acceptor type is n-doped, and the molecular mass of the dopant is greater than 200 g/mol.

In addition, this object is achieved according to the invention by the features of claim 2 in combination in that the electron transport layer containing a donor-type organic material is n-doped and the hole transport layer containing an acceptor-type organic material is p-doped, the molecular mass of the dopant being greater than 200 g/mol.

As described in patent application DE10135513.0(Leo et al, 2001.7.20 application), the order of the layers of the OLED can be reversed, i.e. the contact point (anode) capable of hole injection (light transmission) is changed to cover the electrode. In general, the operating voltage is much higher in the case of inverted organic light-emitting diodes than in the case of the comparative non-inverted structure. The reason for this is the difficulty of injection from the contact into the organic layer, since the work function of the contact is not specifically optimized.

The solution according to the invention is that the injection of charge carriers from the electrode into the organic layer (whether it is a hole-or electron-transport layer) is not so strongly dependent on the work function of the electrode itself, so that it is possible to apply the same electrode-type, for example two identical light-transmissive electrodes, for example ITO, on both sides of the OLED structural element.

The reason for the increased conductivity is the increased equilibrium carrier density in the film layer, which in this case has a larger layer thickness than is possible in the undoped film layer (typically 20-40nm), but does not increase the operating voltage as rapidly as possible, and similarly to the electron injection layer, which in the vicinity of the cathode is a donor-type molecule (preferably an organic molecule or a cleavage thereof, see german patent application DE10307125.3), can be increased in electron conductivity by virtue of the higher intrinsic carrier density after n-doping, which film thickness can also be made larger in the component than is possible in the undoped layer, since the latter leads to an increased operating voltage. The thickness of the two film layers is sufficient to prevent the underlying film layers from being damaged during the sputtering process for making the light-transmissive electrode (e.g., ITO).

In the doped carrier transport layer (holes or electrons) adjacent to the electrodes (anode or cathode), a thin space charge region is formed, through which the carriers can be efficiently injected, through which region the injection cannot be prevented even in the case of high energy barriers due to tunnel injection, it being advantageous if the carrier transport layer can be doped by incorporation of an organic or inorganic substance (dopant), which is firmly embedded in the matrix molecular framework of the carrier transport layer, on the basis of which a high stability can be achieved during operation (without diffusion) of the OLED and also in the thermally loaded state.

An organic light-emitting diode comprising a doped transport layer, which exhibits only high-efficiency luminescence when combined in a suitable manner with a shielding layer, is described in patent application DE 10058578.7 (see x.zhou et al appl. phys. lett.78.410(2001)) which is proposed 2000.11.25, so that in a preferred embodiment the light-transmitting light-emitting diode is also provided with a shielding layer which is located between the light-emitting layer and the carrier transport layer of the component and electrically converts the current-injected carriers of the component into luminescence. The material of the screening layer is selected according to the invention in such a way that, when a voltage is applied in the direction of the operating voltage, the majority carriers (on the HTL side: holes, on the ETL side: electrons) are not blocked to a large extent (low barrier) at the boundary layer of the doped carrier transport layer/screening layer due to the energy levels, but the minority carriers are effectively blocked at the boundary layer of the light-emitting layer/screening layer (high barrier). Further, the barrier for injecting carriers of the shielding layer into the light emitting layer is small, and carriers in the boundary layer are preferably converted strongly into excitons of the light emitting layer, which can prevent the generation of excited compound molecules at the interface of the light emitting layer to lower the light emission efficiency. Since the carrier transport layer preferably has a high band gap, the shielding layer can be chosen to be very thin, although no carrier tunneling from the light-emitting layer to the carrier transport layer is possible, which makes it possible to operate at low voltages despite the presence of the shielding layer.

A preferred version of the structure of a light-transmitting OLED according to the invention as claimed in claim 1 comprises the following layers (non-inverted structure):

1. the number of carriers, the base,

2. a light-transmissive electrode, such as ITO, capable of injecting holes (anode or cathode),

a p-doped, hole-injecting and transporting film layer,

4. a thin hole side shielding layer made of a material having a band energy level suitable for the band energy level of its surrounding film layer,

5. luminescent layer (possibly doped with luminescent dyes)

6. Thin electron side shielding layer made of a material having a band energy level suitable for the band energy level of its surrounding film layer

N-doped electron injection and transport film layer

8. Transparent electrode capable of injecting electrons (cathode being negative electrode)

9. Encapsulation for isolating ambient influences

A second preferred version of a light-transmitting OLED structure according to the invention, as claimed in claim 2, comprises the following layers (inverted structure)

1. The number of carriers, the base,

a light-transmissive electrode, such as ITO, capable of injecting electrons (frustrated electrode-negative electrode),

3 a.n-doped, electron injecting and transporting film layer,

4a thin electron side shield layer made of a material whose band energy level is suitable for that of its surrounding film layer,

a light-emitting layer (possibly also doped with a light-emitting dye),

a thin hole-side shielding layer made of a material having a band energy level suitable for that of its surrounding film layer,

7 a.p-doped, hole-injecting and transporting film layer,

a light-transmissive electrode, hole-injecting (anode or cathode), such as ITO,

9. and packaging to isolate the influence of the surrounding environment.

It is also one of the tasks considered by the present invention to use only one shielding layer, since the band energy levels of the injection and transport layers and the light emitting layer are already adapted to each other on one side, and furthermore the carrier injection function and carrier transport function in the layers 3 and 7 can be distributed in multiple layers, of which at least one layer (next to an electrode) is doped, when the doped layer is not directly adjacent to an electrode, all layers between the doped layer and the corresponding electrode must be thin enough to allow efficient carrier tunneling (< 10nm), and these layers can be thicker if it has a very high conductivity (the bulk resistance of this layer must be less than the resistance of the adjacent doped layer). The intermediate layer according to the invention can additionally be considered as part of an electrode, with typical molar doping concentrations in the range from 1: 10 to 1: 10000, the dopant being an organic molecule with a molecular mass of more than 200 g/mol.

Drawings

The invention is further illustrated below with the aid of examples. The drawings are described as follows:

FIG. 1: energy diagram of a light-transmissive OLED in the embodiments customary hitherto (without doping, the numbers listed relate to the non-inverting film structure of the OLED according to claim 1). The energy level states without limiting voltage (HOMO and LuMO) are described above, (it can be observed that both electrodes have equal work functions); the following is the state in which a limit voltage is applied, and for the sake of simplicity, the shield layers 4 and 6 are also given here.

FIG. 2: the energy diagram of a light-transmitting OLED comprising a doped carrier transport layer and a suitable shielding layer (note the bending of the band immediately adjacent to the contact layer, here ITO in both cases) is shown numerically in relation to the two above-described embodiments, the structure of the upper surface element, which due to its light-transmitting properties radiates light in both directions, and the band structure below.

FIG. 3: the optical density-voltage-characteristic curves of the following examples, typically 100cd/m²The monitor-optical density of (1) has been reached at 4V with an efficiency of 2cd/a, however for process reasons the anode material here is not applied with a light-transmissive contact (e.g. ITO) but simulated with a semi-transparent (50%) full contact, which relates to a semi-light-transmissive OLED.

Detailed Description

In the embodiment shown in fig. 1, no space charge region is present at the contact point, which type of embodiment requires a lower energy barrier for the injection of carriers, which cannot or cannot be achieved with the existing materials (cf. the state of the art mentioned above), so that the injection of carriers from the contacts is not very efficient and the OLED has a high operating voltage.

The structural defects hitherto avoided according to the invention by the use of doped injection and transport layers, often in combination with shielding layers, fig. 2 shows a corresponding set-up, where the carrier injection and transport layers 3 and 7 are doped in such a way that the boundary layers at the contact points 2 and 8 form space-charge regions, provided that the doping is sufficiently high to enable easy tunneling through of the space-charge regions, which doping is possible, at least as demonstrated in the literature in connection with the p-doping of the hole-transport layer into non-light-transmitting light-emitting diodes (x.q.zhou et al, appl.phys.lett.78, 410 (2001); j.blochwitz et al, organic elecronics 2, 97 (2001)).

This bank design shows the following advantages:

efficient injection of charge carriers from the electrodes into the doped charge carrier transport layer

Independent of details of the preparation of the carrier injection materials 2 and 8

The counter electrodes 2 and 8 also have the possibility of choosing a material with a relatively high barrier, for example with the same material, for example ITO, in both cases.

In the following a preferred embodiment is set out, but in which the electron transport layer is not n-doped with a stable macro-organic dopant, as an example of the effect of the light-transmissive OLED solution containing a doped organic transport layer is represented by the unstable n-doped form of a typical electron transport material (Bphen-bathophenanthroline) containing Li (US patent 6013384(j.kido et al), in the 1998.1.22 application; j.kido et al, appl.phys.lett 73, 2866(1998)), which, as described in the state of the art, can demonstrate the effect of doping with a mixture of Li and bren of about 1: 1, but the film is thermally and practically unstable, because of the high dopant concentration present during the doping process, it must also be considered that the mechanism of doping is another case, when organic molecules and the doping ratio are between 1: 10 and 1: 10000, the precondition is that the dopant does not have a great influence on the structure of the carrier transport layer, which cannot be assumed when doping metals, for example Li, in a 1: 1 mixture.

The OLED has a film structure (reverse type structure)

-1 a: the substrate, for example glass,

-2 a: cathode: ITO is commercially available, untreated,

-3 a: an n-doped electron-transporting film layer, 20nm Bphen to Li 1 to 1 molecular mixing comparison,

-4 a: shielding layer on the electron side: the particle size of the particle is 10nm of Bphen,

-5 a: electroluminescent film layer: 20nmAlq3, can be mixed with an emitter dopant to increase the internal quantum efficiency of the emitted light,

-6 a: shielding layer on cavity side: 5nm Triphenyldiamine (TPD)

-7 a: p-doped hole transporting film layer: 100nm starturst m-MTDATAetF4-TCNQ dopant at 50: 1 (thermally stable to 80 ℃ C.)

-8 a: transparent electrode (anode) indium-tin-oxide (ITO).

The mixed layers 3 and 7 are produced by vacuum hybrid evaporation in an evaporation process, in principle such layers can also be produced by other methods, for example by means of evaporation with a heavy barrier of the substances, by means of diffusion at controlled temperatures, by interpenetration of the substances or by means of other deposition methods (for example centrifugation) in which the substances are mixed in a vacuum or non-vacuum, and the barrier layers 3 and 6 are likewise evaporated in a vacuum or by means of other methods, for example centrifugation in a vacuum or non-vacuum.

FIG. 3 shows the optical density-voltage-characteristic curve of a semi-transparent OLED, for which a semi-transparent full-contact is used as anode (50% transmission) for 100cd/m²The required operating voltage for optical density is 4V. This is one of the minimum operating voltages for light-transmissive OLEDs, particularly with inversion-type film constructions, and the envisaged solution of OLED demonstration is achievable due to the fact thatThe semi-transparent covered electrode has an external current efficiency of only about 2cd/A, rather than the maximum expected 5cd/A in OLEDs using pure Alq3 as the light emitting layer.

The doping layer applied according to the invention enables to achieve in a light-transmitting structure a low operating voltage and a high efficiency which are approximately equal when emitting from one side through the substrate in a conventional structure, based on a high carrier injection as described above, since after doping it is relatively unaffected by the exact work function of the light-transmitting contact material, so that the same electrode material (or a light-transmitting electrode material with only a slight difference in work function) can be used as a contact for electron injection and hole injection.

The skilled person will be aware of numerous modifications and variants of the envisaged invention which are obvious from the examples of embodiments but fall within the scope of the invention, for example light-transmissive contacts other than ITO may be used as anode materials (e.g. in h.kim et al, appl.phys lett.76, 259 (2000); h.kim et al, appl.phys.lett.78, 1050 (2001)), and furthermore the light-transmissive electrode according to the invention uses a thick film layer of a non-light-transmissive metal (e.g. silver or gold) and a light-transmissive electrically-conductive material in combination as an intermediate layer, the thickness of which must be or can be (because the thick doped carrier-transporting layer can cause no damage to the light-emitting layer during sputtering) thin enough that the entire element is light-transmissive in the above sense (transmittance > 75% in the entire visible region.) another embodiment consistent with the invention is that the doped electron-transporting layer uses a material, its LuMO-level (layer 7 or 3a in fig. 1 and 2) is lower than the level (i.e. the larger potential barrier represented in fig. 2) that would result in injection of electrons into the shielding layer and the light-emitting layer (6 or 4a and 5 or 5 a). This makes it possible to use a very thin metal layer (< 2.5nm) of a metal having a lower work function than the LuMO's level of the doped electron transport layer between the n-doped electron transport layer (7 or 5a) and the shielding layer (6 or 4a) or the light-emitting layer (5 or 5 a). The metal layer must be thin enough that the overall transmittance of the element is not significantly reduced (see l.s.hung.m.g.mason; appl.phys.lett.78(2001) 3732).

Symbol tables of interest

1 base of a substrate

2, 2a anodes or cathodes

3, 3a hole-or electron-transport layer (doped)

Thin shielding layer on the 4, 4a hole-or electron side

5, 5a light emitting layer

6, 6a electron-or hole-side shielding

7, 7a hole-or electron-transport layer (doped)

8, 8a anodes or cathodes

9 Package

Claims (19)

1. A light-transmitting, thermally stable light-emitting component comprising an organic film, comprising an organic light-emitting diode, which is formed by a film design according to the sequence of a light-transmitting base (1), a light-transmitting anode (2), a hole transport layer (3) next to the anode, at least one light-emitting layer (5), an electron carrier transport layer (7) and a light-transmitting cathode, characterized in that the hole transport layer (3) is p-doped with an organic material of the acceptor type, and the electron transport layer (7) is n-doped with an organic material of the donor type and has a molecular mass of the dopant of more than 200 g/mol.

2. A light-transmitting, thermally stable light-emitting component comprising an organic layer, comprising an organic light-emitting diode, which is formed by a layer design in the order of a light-transmitting substrate (1), a light-transmitting cathode (2a), an electron transport layer (3a) next to the cathode, at least one light-emitting layer (5a), a hole carrier transport layer (7a) and a light-transmitting anode (8a), characterized in that the electron transport layer (3a) is n-doped with an organic material of the donor type, the hole transport layer (7a) is p-doped with an organic material of the acceptor type, and the molecular mass of the dopant is greater than 200 g/mol.

3. A light-emitting component as claimed in claim 1 or 2, characterized in that a hole-side shielding layer (4, 6a) is provided between the doped hole-transport layer (3, 7a) and the light-emitting layer (5, 5 a).

4. A luminescent component as claimed in claim 1 or 2, characterized in that an electron-side screening layer (6, 4a) is provided between the doped electron transport layer (7, 3a) and the luminescent layer (5, 5 a).

5. A light-emitting component as claimed in claim 1 or 2, characterized in that the light-transmitting contacts are both formed from indium-tin-oxide (ITO).

6. A light-emitting component as claimed in claim 1 or 2, characterized in that the light-transmitting contacts are both made of a material having properties similar to ITO or are both made of another degenerated oxide semiconductor which differs from ITO.

7. A light-emitting element as claimed in claim 1 or 2, characterized in that the two light-transmitting contacts are formed from different contact materials.

8. A light-emitting component according to claim 1 or 2, characterized in that a thin modified contact film is present between the electron-transporting layer (7, 3a) and the cathode (8, 2a) and/or between the anode (2, 8a) and the hole-transporting layer (3, 7a), said films having a thickness of less than 10nm and both being able to tunnel easily.

9. A light-emitting element according to claim 1 or 2, characterized in that the light-emitting layer (5) is a mixed layer consisting of a plurality of materials.

10. A light-emitting component as claimed in claim 1 or 2, characterized in that the p-doped hole transport layer (7, 3a) is composed of an organic host substance and a host-type dopant substance and the molecular mass of the dopant is more than 200 g/mol.

11. A light-emitting component according to claim 1 or 2, characterized in that the electron transport layer is formed by mixing an organic host substance and a donor-type dopant substance, by n-type doping and by the molecular mass of the dopant being more than 200 g/mol.

12. A light-emitting component according to claim 1 or 2, characterized in that a light-transmitting protective layer (9) is attached to the upper light-transmitting cathode or anode (8, 8 a).

13. A light-emitting element as claimed in claim 1 or 2, characterized in that the upper light-transmitting cathode or anode (8, 8a) is provided with a thin metal intermediate layer in addition to the underlying doped carrier transport layer (7, 7a) in such a way that the transmission in the entire visible region is always more than 75%.

14. A luminescent component as claimed in claim 1 or 2, characterized in that the lower anode or cathode (2, 2a) is provided with a thin metallic intermediate layer on the doped carrier transport layer (3, 3a) which is applied thereto, so that the transmission in the entire visible region is always more than 75%.

15. A light-emitting component according to claim 1 or 2, characterized in that the sequence formed by the p-doped hole-transport layer (3, 7a) and the light-transmissive anode (2, 8) is present in a component a plurality of times.

16. A light-emitting component according to claim 1 or 2, characterized in that the sequence formed by the n-doped electron-transporting layer (7 or 3a) and the light-transmitting cathode (8, 2a) is present in a component a plurality of times.

17. A light-emitting component according to claim 1 or 2, characterized in that a thin electron-injection-promoting layer of a metal is present between the doped electron-transport layer (7 or 3a) and the screening layer (6 or 4a) or the light-emitting layer (5 or 5a), said electron-injection-promoting layer having a thickness of less than 2.5 nm.

18. A light-emitting component according to claim 1 or 2, characterized in that the molar concentration of dopant molecules to host molecules in the mixture in the hole-transporting layer (3, 7a) and/or in the electron-transporting layer (7, 3a) is in the range from 1: 10000 to 1: 10.

19. A light-emitting component according to claim 1 or 2, characterized in that the layer thickness of the hole-transporting layer (7), the electron-transporting layer (3), the electroluminescent layer (5) and the screening layer (4, 6) is in the range from 0.1nm to 50 μm.