Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/858—Arrangements for extracting light from the devices comprising refractive means, e.g. lenses
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/30—Organic light-emitting transistors
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/805—Electrodes
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
  • H10K2102/301—Details of OLEDs
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/80—Constructional details
  • H10K50/85—Arrangements for extracting light from the devices
  • H10K50/854—Arrangements for extracting light from the devices comprising scattering means

Definitions

• An organic light-emitting diode is specified.
• An object to be solved is to specify an organic light-emitting diode, OLED for short, in which light can be decoupled efficiently from plasmon modes of a metal electrode.
• this comprises a first electrode, which is formed with a metal.
• the first electrode is made of silver, aluminum, cadmium, barium, indium, magnesium, calcium, lithium and / or gold.
• the first electrode is thus designed in particular with an electrically conductive material, which is opaque even in the case of thin layers.
• the first electrode is preferably formed with a material which, when present in a thickness of at least a quarter of a vacuum wavelength of radiation in the visible spectral range, is opaque to this radiation.
• the latter comprises at least one organic layer sequence with at least one active layer.
• the active layer is hereby set up to generate electromagnetic radiation.
• the active layer is based, for example, on an organic polymer, on an organic oligomer, on organic monomers, on organic small, non-polymeric molecules or on a combination thereof.
• the organic layer sequence may comprise further organic layers, which may be used, for example, as Charge carrier injection layers are configured as charge carrier transport layers and / or as charge carrier stop layers.
• the LED has these a second electrode.
• the second electrode, as well as the first electrode designed flat and / or planar.
• Flat may mean that the electrodes at least 80% or completely cover major surfaces of the organic layer sequence on opposite sides, or that a ratio of lateral extent and thickness of the electrodes is at least 1000.
• LED is the organic layer sequence between the first and the second electrode.
• the organic layer sequence can here be completely or partially between the electrodes.
• this comprises a radiation-transmissive index layer.
• the index layer is thus translucent or, preferably, transparent or clear-sighted, at least in partial regions of the visible spectral range.
• the index layer is formed with a dielectric material.
• the index layer can in this case be formed with a homogeneous, for example crystalline material or else be formed by at least one metamaterial.
• suitable materials are, for example, LiNbC> 3, ZnS, ZnSe or TeO 2.
• organic materials such as Cg Q having a refractive index of about 2.2 can be used for or in the index layer.
• a suitable metamaterial is, for example, TiO 2, which is embedded in a matrix material.
• Suitable matrix materials are, for example, polymers, in particular epoxides, silicones and epoxy-silicone hybrid materials.
• the index layer is applied to an outside of the first electrode facing away from the organic layer sequence.
• the metallic first electrode is located between the index layer and the organic layer sequence.
• an average optical refractive index of the index layer is greater than or equal to an average
• Refractive index of the organic layer sequence means that the refractive index is averaged over the entire layer thickness of the organic layer sequence or the index layer, wherein layers of the index layer, which are closer to the first
• the average refractive index may also be an effective refractive index of the respective layers. If, for example, the mean and / or effective refractive index of the organic layer sequence is 1.8, the average and / or effective refractive index of the index layer is likewise at least 1.8.
• this has a front side and a rear side.
• the reverse side faces the index layer or is formed by the index layer, and the front side is facing the organic layer sequence. That is, between the back and the organic layer sequence is at least partially the index layer and between the front and the index layer is at least partially the organic layer sequence.
• a radiation generated in the LED leaves the organic light emitting diode on the front and / or on the back.
• the radiation preferably leaves the light-emitting diode at least on the front side and optionally additionally on the rear side. At side surfaces transversely to the front side of the light emitting diode, no or no significant radiation component is preferably emitted.
• the organic light-emitting diode In accordance with at least one embodiment of the organic light-emitting diode, at least part of an electromagnetic plasmon radiation generated by the organic light-emitting diode passes through the index layer.
• the plasmon radiation is a radiation that is generated from surface plasmons of at least the first electrode.
• the organic light-emitting diode comprises a first electrode, which is formed with a metal, and a second electrode. Furthermore, the organic light-emitting diode includes an organic layer sequence with at least one active layer, wherein the organic layer sequence is located between the first and the second electrode. In addition, the organic light-emitting diode has a radiation-permeable index layer, which is located on an outside of the first electrode facing away from the organic layer sequence.
• Refractive index of the index layer is greater than or equal to a mean refractive index of the organic layer sequence. Furthermore, the organic light emitting diode on a front and a back, wherein the back the index layer and the front side facing the organic layer sequence and a radiation generated in the light emitting diode is emitted at the front and / or at the back. At least a portion of an electromagnetic plasmon radiation generated by the organic light emitting diode passes through the index layer.
• the first electrode is in direct physical contact with both the organic layer sequence and the index layer.
• the first electrode is completely or partially confined and enclosed in a direction transverse to a main extension direction of the first electrode by the index layer and the organic layer sequence.
• surface plasmons are excited by an electromagnetic radiation generated in the active layer at least at the interface between the first electrode and the organic layer sequence.
• the plasmon radiation is completely or partially generated.
• the active layer of the organic layer sequence provided for the generation of radiation has molecules which, in an electronically excited state, approximately indicate an electric dipole moment, wherein in an electronic ground state the molecules do not need to detect a dipole moment.
• electromagnetic interface modes At the interface between the organic layer sequence and the metallic first electrode, there are electromagnetic interface modes. Near-field effects and / or surface roughness can be used to label the interfacial modes, also referred to as surface plasmon modes, to the molecules of the organic layer sequence pair or vice versa.
• the magnitude of the amount of coupling to the surface plasma modes may be about 30%. In other words, a significant proportion of the power of the organic light emitting diode is transferred to the surface plasmons.
• the power component coupled to the surface plasmons is lost, in particular by attenuation of the surface plasma modes in the metal of the first electrode, and can not be converted into light.
• the index layer on the side facing away from the organic layer sequence side of the first electrode is a conservation of energy and a momentum conservation for the
• the index layer has an average geometric thickness of at least 50 nm, in particular of at least 100 nm or at least 200 nm.
• the average geometric thickness of the index layer preferably exceeds at least 300 nm, in particular at least 500 nm.
• the index layer thus has a thickness that corresponds at least to the order of magnitude of the wavelength of the electromagnetic radiation within the index layer.
• the first metallic electrode has a thickness between 15 nm and 65 nm inclusive, preferably between 25 nm and 50 nm inclusive.
• the first electrode is largely impermeable to radiation. That is, no significant portion of the radiation generated in the active layer passes directly through the first electrode without being reflected, absorbed, or converted into surface plasmons.
• the thickness of the first electrode in the specified range is sufficiently low to efficiently ensure transport of the surface plasmons from an inner layer of the first electrode facing the organic layer sequence to the outer side of the first electrode. In the specified thickness range of the first electrode, the generation of the plasmon radiation is therefore particularly efficient.
• an average distance between the first electrode and the active layer is between 15 nm and 100 nm, preferably between 25 nm and 50 nm inclusive.
• organic light emitting diodes are without an index layer designed as specified, the distance between the first electrode and the active layer usually selected as large as possible. As large as possible means that the distance exceeds 100 nm, for example. Since a conversion of the surface plasmons into the plasmon radiation is made possible via the index layer, the distance between the active layer and the first electrode is reducible.
• an average distance between the first electrode and the active layer is at most 25 nm, in particular at most 15 nm.
• Such a small distance between the active layer and the first electrode is a particularly efficient coupling in the active Layer generated radiation to the shovenplasmonenmoden the first electrode guaranteed.
• a particularly high proportion of the power consumption of the organic light-emitting diode in surface plasmons is converted in at least the first electrode.
• an average total geometric thickness of the organic layer sequence is less than or equal to 150 nm, preferably less than or equal to 90 nm.
• Such a small overall thickness of the organic layer sequence is made possible by the recovery of the surface plasmons in the plasmon radiation, so that the overall efficiency of the LED due to the excitation of the surface plasmons the
• the electrical properties of the organic light-emitting diode continue to improve. Thus, due to their small thickness, only a lower electrical voltage drops at the organic layer sequence. Furthermore, the material used to produce the organic Layer sequence is necessary, reducible. In addition, the organic layer sequence no longer acts or at least far less than with conventional light-emitting diodes as a waveguide layer. If the organic layer sequence does not act or reduces as a waveguide layer, then a coupling-out efficiency of the radiation produced can increase.
• an average radiation intensity of the radiation generated by the light-emitting diode at the rear side of the light-emitting diode is at least 5%, in particular at least 15%, of an average radiation intensity at the front side of the light-emitting diode.
• a significant portion of the radiation power emitted by the light-emitting diode is emitted at the rear side, that is to say at the side of the light-emitting diode which faces away from the organic layer sequence.
• the organic light-emitting diode corresponds, with a tolerance of 25 percentage points, the average radiation intensity at the back of the average radiation intensity at the front.
• the tolerance is preferably at most 10 percentage points, in particular the mean radiation intensity at the rear side and at the front side is the same within the production tolerances.
• the ratio of the radiation intensities on the front side and on the rear side can be adjusted, for example, by the distance between the active layer and the first electrode, ie between the degree of coupling to the surface plasma modes, and by the thickness and / or
• the mean refractive index of the index layer is at least 1.1 times the mean refractive index of the organic layer sequence.
• the average refractive index of the index layer is preferably at least 1.2 times, in particular at least 1.3 times, the mean refractive index of the organic layer sequence. Due to the comparatively large refractive index difference, an efficient generation of the plasmon radiation from the surface plasmons can be ensured.
• the index layer is formed from alternately arranged layers, wherein the alternately arranged layers each have different material compositions.
• the alternately arranged layers can alternately exhibit a comparatively high and a comparatively low refractive index.
• Light emitting diode is at least one of the alternately arranged layers designed with a metal oxide, which is transparent.
• the index layer is formed of an alternating sequence of ZnO layers and TiO 2 layers and / or SrTiC ⁇ layers.
• the layers are produced, for example, via atomic layer deposition, English atomic layer deposition or ALD for short.
• Such a designed index layer has a high refractive index and a high transparency and is still for sealing the organic light emitting diode against external influences such as oxygen and moisture suitable.
• the organic light-emitting diode whose rear side is formed by the index layer. That is, a light extraction from the organic light emitting diode at the back takes place directly from the index layer.
• the index layer has a structuring to increase a radiation outcoupling of the plasmon radiation.
• the structuring can be regular or even irregular.
• the patterning is produced by etching with an etching mask or by a random roughening process, such as grinding or sandblasting.
• the index layer is admixed with a diffusion agent.
• the diffusion agent is formed, for example, by scattering particles.
• the plasmon radiation or at least part of the plasmon radiation does not pass through the index layer in a straight line, but experiences at least one of the diffusion means
• the index layer includes a conversion agent.
• the conversion means is hereby arranged to absorb at least a portion of the plasmon radiation and convert it into a radiation having a larger wavelength.
• a spatial radiation characteristic of the light-emitting diode on the rear side can also be changed, in particular made more uniform.
• the conversion agent can also be used in combination with the diffusing agent and with the structuring of the index layer.
• both the first electrode and the second electrode are formed with a metal. So then both electrodes are metallic electrodes.
• the organic light emitting diode is designed as a so-called microresonator OLED.
• a type of resonator is formed by the first electrode and the second electrode.
• both electrodes have a thickness of at most 30 nm, in particular of at most 15 nm. In other words, due to the small thickness, both electrodes are partly transparent to the visible radiation generated in the active layer.
• the second electrode is formed with a transparent conductive oxide.
• the thickness of the second electrode then preferably exceeds 100 nm, in particular 200 nm.
• the thickness of the second electrode is preferably between 100 nm and 140 nm.
• the second electrode is with or consists of indium oxide, indium tin oxide, indium zinc oxide, zinc oxide or tin oxide formed.
• Al-doped zinc oxide short AZO, can be used as material for the second electrode.
• At least the first electrode has a thickness variation along at least one main extension direction, preferably along two main extension directions.
• the thickness of the first electrode changes, for example, periodically or statistically distributed along the two main orthogonal directions.
• a carrier of the light-emitting diode has a structuring on a main side.
• the first and the second electrode as well as the organic layer sequence and the index layer, in each case preferably with a constant thickness over the entire main side within the production tolerances, are then applied to this main side of the carrier.
• a length scale of the thickness variation and / or the structuring lies between 300 nm and 1.5 ⁇ m inclusive, preferably between 400 nm and 1.0 ⁇ m inclusive.
• the thickness variation here can be a uniform or periodic variation, which takes place, for example, in a sinusoidal or stepped manner and exhibits a periodicity corresponding to the length scale. It is also possible that the thickness variation in the form of holes in the first electrode, which are arranged at a regular distance from each other, is executed.
• the length scale may be an average length scale and the thickness variation along the main directions of extension may be irregular or random.
• a mirror which is set up to reflect the plasmon radiation toward the organic layer sequence is located on one side of the index layer facing away from the first electrode.
• the index layer preferably has a diffusion agent and / or a structuring.
• the mirror is part of the index layer.
• the mirror is then shaped as a Bragg mirror and the mirror layers are at the same time partial layers of the index layer.
• Figures 1 to 12 are schematic sectional views of
• Figure 13 is a schematic sectional view of a schematic diagram
• Figure 14 is a schematic representation of dispersion relations of heat and heat.
• the light-emitting diode 10 has an organic layer sequence 3 with an active layer 33. During operation of the light-emitting diode 10, an electromagnetic radiation R is generated in the active layer 33.
• a total thickness H of the organic layer sequence 33 is, for example, at most 300 nm, in particular at most 90 nm.
• a second electrode 2 is located on a side of the layer sequence 3 facing a carrier 7. The second electrode 2 is designed, for example, with a transparent conductive oxide. Through the second electrode 2 and the carrier 7, at least part of the radiation R generated in the active layer 33 is emitted at a front side 6 of the light-emitting diode 10.
• a first electrode 1 On a side of the organic layer sequence 3 facing away from the carrier 7 there is a first electrode 1, which is formed with a metal, for example silver.
• a metal for example silver.
• surface plasmons +, - are excited at the interface between the first electrode 1 and the active layer sequence 3.
• These surface plasmons +, - can reach an outer side 11 of the first electrode 1 facing away from the organic layer sequence 3.
• a thickness D of the first electrode 11 is preferably between 25 nm and 50 nm inclusive.
• an index layer 4 is applied in direct contact with the first electrode 1.
• An average refractive index of the index layer 4 is at least as great or, preferably, greater than an average refractive index of the organic layer sequence 3.
• the index layer 4 also forms a rear side 5 of the light-emitting diode 10.
• the plasmon radiation Pl, P2, P3 at least partially passes through the index layer 4 and is emitted by the light-emitting diode 10 on the rear side 5.
• a thickness D of the index layer 4 in this case is preferably at least 200 nm.
• a wavelength of the plasmon radiation Pl is thus smaller than a wavelength of the plasmon radiation P2, which in turn is smaller than a wavelength of the plasmon radiation P3.
• the index layer 4 is located between the substrate 7 and the first electrode 1.
• the back side 5 is located through the substrate 7 formed and the front side 6 by an organic layer sequence 3 opposite outer side 12 of the second electrode 2.
• the plasmon radiation Pl, P2, P3 is emitted through the substrate 7 from the light emitting diode 10th
• the substrate 7 may have a roughening to improve the coupling-out efficiency.
• the substrate 7 itself forms the index layer 4.
• the substrate 7 is therefore designed with a material which has a refractive index which is at least as great as the mean refractive index of the organic layer sequence 3.
• a refractive index difference between the organic layer 3 is preferred
• Layer sequence 3 and the substrate 7 at least 0.2 or at least 0.3.
• the refractive index of the substrate 7 is then approximately 2.1 and the average refractive index of the organic layer sequence 3 is approximately 1.8, in particular with a tolerance of 0.1 or 0.05 in each case.
• the organic light-emitting diode 10 according to FIG. 4 is designed as a microresonator light-emitting diode.
• Both the first electrode 1 and the second electrode 2 are each formed from a metal, for example, each made of silver. However, the electrodes 1, 2 preferably have metals which are different from one another or consist of different metals.
• Both on the outer side 11 of the first electrode 1 and on the outer side 12 of the second electrode 2 are the index layers 4a, 4b.
• the index layer 4a at the first electrode 1 simultaneously represents the carrier 7.
• the thicknesses D1, D2 of the first electrode 1 and the second electrode 2 are adjustable so that both the surface plasmons and thus a plasmon radiation Pl, P2, P3 are generated, and that the radiation R generated directly in the active layer 3 is at least one of the At least partially pass through electrodes 1, 2. This makes it achievable, as well as in the
• the first electrode 1 has a thickness variation with a length scale L along a main extension direction.
• the length scale L is in this case preferably in the order of magnitude of the vacuum wavelength of the emitted plasmon radiation Pl, P2, P3.
• the thickness variation shows a periodic, sinusoidal course.
• the index layer 4 unlike shown in Figure 5, show a thickness variation. It is also possible, notwithstanding the representation in FIG. 5, that the second electrode 2 has a thickness variation and the layers 3-5 facing away from the substrate 7 from the second electrode 2 are present with a constant thickness. Also, one of the organic layer sequence 3 facing side of the substrate 7 may be structured, in which case preferably the further layers 2-5 have a constant thickness.
• the thickness variation on the length scale L of the wavelength of the plasmon radiation Pl, P2, P3 is a kind of optical grating on the first electrode 1 can be generated. This makes it possible to adjust an angular dependence of the emitted plasmon radiation Pl, P2, P3. For example, the intensity of the plasmon radiation P2 exceeds the intensities of the plasmon radiation Pl, P3.
• the radiation R generated directly in the active layer 33 is not shown in FIG. 5 and in the following figures.
• the first electrode 1 has holes 9.
• a diameter of the holes 9 is, for example, between 100 nm and 200 nm inclusive.
• Through the holes 9 in the first electrode 1 is also a kind of optical grating for adjusting the radiation characteristic on the back 5 can be generated.
• FIG. 7 illustrates that the index layer 4 preferably has a structuring 13 for increasing the coupling-out efficiency of the plasmon radiation P.
• the index layer 4 comprises a diffusion agent 14 in the form of scattering particles. Due to the scattering particles 14, the plasmon radiation P passes through the index layer 4, at least in part, not in a straight line, but is deflected or reflected at the scattering particles. As a result, a decoupling efficiency of the plasmon radiation P from the index layer 4 can also be increased.
• the index layer 4 is given a conversion means 15.
• particles of the conversion agent 15 is at least a part of the Plasmon radiation P absorbed and converted into a secondary radiation S with a longer wavelength.
• a radiation characteristic of the emitted radiation P, S can be homogenized, that is, made more uniform.
• the conversion means 15 can be selected such that, for example, only a blue and green spectral component of the plasmon radiation is converted into the secondary radiation S and approximately a red component of the plasmon radiation P is emitted unconverted on the back side 5.
• the first electrode 1 exhibits a step-like thickness variation. Due to the thickness variation, it can be achieved that at different locations of the first electrode 1 for different wavelengths of
• Plasmon radiation Pl, P2, P3 different efficiencies for the conversions of surface plasmons in the plasmon radiation Pl, P2, P3 are present.
• influencing and shaping of the emission characteristic on the rear side 5 are possible hereinafter, even without structuring of the first electrode 1 in the manner of an optical grating.
• the thickness variation of the first electrode 1 is not stepped, as in FIG. 10, but in the manner of a ramp.
• a periodicity of the ramp-like thickness variation is preferably greater than the wavelength of the plasmon radiation Pl, P2, P3.
• FIG. 12 shows an exemplary embodiment of the light-emitting diode 10, in which a mirror 8 is applied to one side of the index layer 4 remote from the organic layer sequence 3.
• the index layer 4 preferably has an in
• Figure 12 not shown on scattering means. Furthermore, it is possible that the mirror 8 is formed as a part of the index layer 4.
• FIG. 13 shows a so-called Kretschmann configuration.
• a glass prism 16 is deposited on the first electrode 1.
• an organic layer 3 is further applied.
• a radiation Q of a certain wavelength is irradiated.
• a wavelength of the radiation Q and the refractive indices of the glass prism 16 and the organic layer 3 a certain proportion of the radiation Q is converted into the surface plasmons +, -. It is possible here that the total radiation Q in
• FIG. 14 schematically shows a dispersion relation of the surface plasmons +, -.
• Plotted here is a wave vector k in m "1 against a wavelength ⁇ in nm or a frequency f in Hz.
• a conversion of the radiation Q in the surface plasons +, - is with respect to the dispersion relation only from a curve on the right to a further left Curve possible.
• the curve a schematically shows the dispersion relation in air
• the curve b the dispersion relation in a medium with refractive index 1.5
• the curve c the dispersion relation for surface plasmons at an air-silver-interface
• the curve d the dispersion relation for surface plasmons on a silver Organic interface, wherein the organic has a thickness of about 30 nm.

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• 2009
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