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WO1998007202A1 - Cathodes en nitrure de gallium pour dispositifs electroluminescents et ecrans de visualisation - Google Patents

Cathodes en nitrure de gallium pour dispositifs electroluminescents et ecrans de visualisation Download PDF

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Publication number
WO1998007202A1
WO1998007202A1 PCT/IB1996/000780 IB9600780W WO9807202A1 WO 1998007202 A1 WO1998007202 A1 WO 1998007202A1 IB 9600780 W IB9600780 W IB 9600780W WO 9807202 A1 WO9807202 A1 WO 9807202A1
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organic
light emitting
cathode
substrate
gan
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PCT/IB1996/000780
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English (en)
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Supratik Guha
Richard Alan Haight
Samuel Clagett Strite
Ronald Roy Troutman
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International Business Machines Corporation
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Priority to PCT/IB1996/000780 priority Critical patent/WO1998007202A1/fr
Publication of WO1998007202A1 publication Critical patent/WO1998007202A1/fr

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/80—Constructional details
    • H10K59/805—Electrodes
    • H10K59/8052—Cathodes

Definitions

  • the present invention pertains to organic electroluminescent devices, arrays, displays and methods for making the same.
  • Organic electroluminescence (EL) has been studied extensively because of its possible applications in discrete light emitting devices, arrays and displays. Organic materials investigated so far can potentially replace conventional inorganic materials in many applications and enable wholly new applications. The ease of fabrication and extremely high degrees of freedom in organic EL device synthesis promises even more efficient and durable materials in the near future which can capitalize on further improvements in device architecture.
  • OLEDs Organic EL light emitting devices
  • FIG. 1A The simplest possible structure, schematically illustrated in Figure 1A, consists of an organic emission layer 10 sandwiched between two electrodes 1 1 and 12 which inject electrons (e ) and holes (h 1 ), respectively.
  • e electrons
  • h 1 holes
  • Such a structure has been described in the above mentioned paper of Burroughs et al., for example.
  • the electrons and holes meet in the organic layer 10 and recombine producing light. It has been shown in many laboratories, see for example: "Conjugated polymer electroluminescence", D. D. C. Bradley. Synthetic Metals, Vol. 54, 1993, pp.
  • Figure 2A illustrates a device with a large electron barrier 16, such that few electrons are injected, leaving the holes no option but to recombine in the cathode 15.
  • a second problem, illustrated in Figure 2B, is that the mobilities of electrons and holes in most known organic materials, especially conductive ones, differ strongly.
  • Figure 2B illustrates an example where holes injected from the anode 18 quickly traverse the organic layer 19, while the injected electrons move much slower, resulting in recombination near the cathode 17. If the electron mobility in the organic layer 19 were larger than the holes', recombination would occur near the anode 18. Recombination near a metal contact is strongly quenched by the contact which limits the efficiency of such flawed devices.
  • This feature eliminates non-radiative recombination at the metal contacts as described in Figure 1A and also promotes a high density of electrons and holes in the same volume leading to enhanced radiative recombination.
  • the main figure of merit for electrode materials is the position of the bands relative to those of the organic materials (see Bradley and Parker above for detailed discussion).
  • the electrode material it is also desirable for the electrode material to be either transparent or highly reflective.
  • the electrode should also be chemically inert and capable of forming a dense uniform film to effectively encapsulate the OLED. It is also desirable that the electrode not strongly quench organic EL.
  • High voltage is necessary because electron injection from Al into, e.g., Alq3 is field assisted.
  • the high operating voltage reduces device efficiency due to increased ohmic losses.
  • the higher electrical fields present at increased voltages also are likely to degrade the device materials more rapidly by driving interdiffusion or exciting parasitic chemical reactions or recombination processes.
  • Al contacts, of lesser reactivity compared to Mg or Ca, have still been observed to degrade during OLED operation, see e.g. L. M. Do et al., "Observation of degradation processes of Al electrodes in organic EL devices by electroluminescence microscopy, atomic force microscopy, and Auger electron microscopy", Journal of Applied Physics, Vol. 76, No. 9, 1994, pp. 5118-5121 .
  • ITO On the anode side, ITO, which has been preferred primarily for its high work function and its properties as a transparent conductor, is also not ideal. Parker, in the reference cited above, has shown that the replacement of ITO with higher work function Au yields a two-fold improvement in device efficiency. This work reveals that an undesirable barrier to hole injection exists between ITO and preferred HTL materials. There are also questions about the chemical reactivity of ITO contacts. Oxidation of, and In diffusion into the organic layers, arising from the proximity of the ITO contact has been speculated to contribute to OLED degradation. ITO is also polycrystalline, and its numerous grain boundaries provide ample pathways for impurity diffusion.
  • Organic LEDs have great potential to outperform conventional inorganic LEDs in many applications.
  • One important advantage of OLEDs and devices based thereon is price since they can be deposited on large, inexpensive glass substrates, or a wide range of other inexpensive transparent, semitransparent or even opaque crystalline or non-crystalline substrates at low temperature, rather than on expensive crystalline substrates of limited area at comparatively higher growth temperatures (as is the case for inorganic LEDs).
  • the substrates may even be flexible enabling pliant OLEDs and new types of displays. To dale, the performance of OLEDs and devices based thereon is inferior to inorganic ones for several reasons:
  • High operating voltage Organic devices require more voltage to inject and transport the charge to the active region (emission layer) which in turn lowers the power efficiency of such devices. High voltage results from the need for high electric fields to inject carriers over energy barriers at the electrode/organic interfaces, and from the low mobility of the carriers in the organic transport layers (ETL and HTL) which leads to a large ohmic voltage drop and power dissipation.
  • A) Efficient low field electron injection requires low work function cathode metals like Mg, Ca, Li etc. which are all highly reactive in oxygen and water. Ambient gases, and gases coming out of the organic materials during ohmic heating degrade the contacts.
  • OLEDs are mainly limited by their contacts and transport layers, and feedback from the transport layer heating. It is thus highly desirable to replace the low work function metal based cathodes with stable, possibly transparent cathode characterized by barrierless charge injection into OLEDs.
  • a transparent cathode provides the additional advantage of allowing conventional ITO anodes to be replaced with improved anodes.
  • the contact materials need to be improved to realize OLEDs and displays based thereon with superior characteristics. It is an object of the present invention to provide new and improved organic EL devices, arrays and displays based thereon.
  • the above objects have been accomplished by providing an OLED having a cathode comprising gallium nitride (GaN) wide bandgap semiconductor.
  • GaN gallium nitride
  • the inventive approach capitalizes primarily on the favorable conduction band energy of GaN, as well as its good conductivity, transparency in the visible spectrum, chemical inertness, hardness, and ability to be deposited in the amorphous state at extremely low temperatures on glass, organic thin films, or other amorphous or crystalline substrates.
  • Our experiments have shown that GaN is conductive, even when deposited at room temperature in the amorphous state, highly transparent in the visible spectrum, and has a favorable conduction band alignment for electron injection into the LUMOs of preferred OLED materials.
  • GaN is an excellent encapsulant for OLEDs due to the extremely low diffusivity of impurities in GaN and the nearly amorphous state of material deposited at low temperature.
  • GaN - having all of the above favorable properties - can be deposited onto glass, or even directly onto an OLED multilayer structure, and produces a device with improved performance and stability.
  • a single or multi-layer OLED structure having a GaN cathode directly in contact with the corresponding organic layer, and a conventional opposite contact electrode is envisioned .
  • an OLED structure having an (AI,ln)GaN cathode directly in contact with the corresponding organic layer, and a conventional opposite contact electrode is envisioned.
  • the purpose of alloying the GaN cathode with small amounts ( ⁇ 20%) of AIN is to finely tune the position of the cathode conduction band to the corresponding organic material molecular orbital
  • the purpose of alloying the GaN with InN is to improve the ohmic contacts between the cathode and the outer cathode layer(s).
  • an OLED in which a GaN cathode, preferably an AIGalnN cathode, is separated from the nearest organic layer by a thin metal interlayer is envisioned.
  • the metal can be selected for its transparency, work function, or properties as a diffusion barrier between the organic materials and GaN, and serves the purpose of further improving the stability or electron injection of the GaN/organic interface.
  • an OLED in which a GaN cathode, preferably an AIGalnN cathode, is in direct contact to the nearest organic layer, but has a thin embedded metal interlayer very near to the GaN/organic interface.
  • the metal can be selected for its work function, properties as a diffusion barrier between the organic materials and GaN, or transparency, and serves the purpose of further improving the stability or electron injection of the GaN/organic interface.
  • GaN is highly transparent to visible light. This adds flexibility in the choice of anode designs, e.g. the anode can be opaque.
  • GaN is chemically inert and thermally stable and therefore has no undesirable solid state interactions with the organic layers with which it is in contact or close proximity. 4. GaN is an outstanding encapsulant and mechanical protectant material for OLEDs, due to its nearly amorphous state, hardness and low impurity diffusion constants.
  • GaN can be deposited at conditions required for OLED formation (e.g. low temperature, amorphous substrates, minimum damage to the growth surface) in a conductive state.
  • GaN as a semiconductor, quenches optical recombination in nearby organic layers less strongly than metals enabling reduced transport layer thicknesses.
  • GaN/Organic Cathode The GaN is in direct contact with the electron transporting OLED layer.
  • the GaN may be deposited onto the organic material or the organic material may be deposited onto the GaN.
  • InGaN/GaN/AIGaN/organic Cathode The AIGaN or GaN is in direct contact with the electron transporting OLED layer. Small amounts ( ⁇ 20%) of AIN tune the (AI,ln)GaN conduction band to precisely match the organic material . InGaN or GaN is furthest from the organic material and facilitates lateral conduction or ohmic contact formation to the GaN based cathode.
  • the cathode may be deposited onto the organic material or the organic material may be deposited onto the cathode.
  • (AI,ln)GaN/Metal/Organic Cathode The GaN or (Al .ln)GaN is separated from the electron transporting OLED layer by a thin metal layer. The thickness of the metal layer can range between a partial monolayer to 20 nm. Either the cathode or the organic layer can be deposited first.
  • (AI,ln)GaN/Metal/(AI,ln)GaN Organic Cathode The GaN or (AI,ln)GaN is in direct contact with the electron transporting OLED layer, and encapsulates a thin metal layer a short distance ( ⁇ 50 nm) from the cathode/organic interface. The thickness of the metal layer can range between a partial monolayer and 50 nm. Either the cathode or the organic layer can be deposited first.
  • FIG. 1A shows a known OLED having an emission layer and two electrodes.
  • FIG. 1 B shows another known OLED having an emission layer and two metal electrodes, with work functions chosen such that the energy barriers for carrier injection are reduced .
  • FIG. 2A shows another known OLED having an emission layer and two metal electrodes, the work function of the anode being chosen such that the energy barrier for hole injection is low, whereas the work function of the cathode poorly matches the emission layer yielding little electron injection and little radiative recombination in said emission layer.
  • FIG. 2B shows another known OLED having an emission layer with lower electron mobility than hole mobility such that the recombination occurs close to the cathode where it is quenched.
  • FIG. 3 shows another known OLED having an electron transport layer and hole transport layer.
  • FIG. 4 shows an optical absorption spectrum of a GaN/glass thin film.
  • FIG. 5 shows the band structure measured by ultraviolet photoemission spectroscopy for a GaN/Alq3 heterojunction.
  • Experimental error is included in the Alq3 bands as drawn.
  • the lowest unoccupied molecular orbital (LUMO) of Alq3 lies at equal or lower energy compared to the GaN conduction band minimum meaning that electron injection from GaN to Alq3 is barrierless.
  • FIG. 6 shows a cross section of the first embodiment of the present invention in which a GaN cathode is deposited on the substrate before the organic layer stack. Light is emitted through the transparent cathode and glass substrate into the plane below the substrate.
  • FIG. 7 shows a cross section of the second embodiment of the present invention in which a GaN cathode is deposited on top of the organic layer stack. Light is emitted through the transparent cathode into the plane above the substrate.
  • FIG. 8 shows a cross section of the third embodiment of the present invention in which an AIGalnN cathode is deposited on top of the organic layer stack. Light is emitted through the ITO anode and glass substrate into the plane below the substrate. If a transparent outer cathode metal other than Al would be chosen, the cathode would also be transparent, and light would be emitted into both planes above and below the substrate.
  • FIG. 9 shows a cross section of the fourth embodiment of the present invention in which a GaN cathode deposited on top of the organic layer stack is separated by a thin metal interlayer.
  • the metal serves to either improve injection, protect the organic during GaN deposition, or act as a diffusion barrier. Light is emitted through the transparent cathode plane above the substrate.
  • FIG. 10 shows a cross section of the fifth embodiment of the present invention in which a GaN cathode encapsulates a thin metal layer which is situated very near to the organic layer stack.
  • the thin GaN layer permits electrons to pass freely from the metal to the organic layer, either by tunneling or thermionic emission, while chemically and physically isolating the metal from the organic. Light is emitted into both the planes above and below the substrate.
  • FIG. 11 shows a cross section of a display or array according to the present invention.
  • the transparent GaN based top cathode permits an opaque Si substrate to be chosen.
  • the Si substrate can be an integrated circuit providing the display function to the OLED array deposited on top of it.
  • FIG. 12 shows a cross section of a display or array according to the present invention in which a GaN based cathode is deposited onto an opaque Si substrate.
  • the GaN cathode provides a stable cathode which can withstand typical handling and processing of the Si wafer.
  • FIG. 13 shows a cross section of a display or array according to the present invention in which a transparent GaN based cathode down geometry is used on a glass substrate. Light is emitted in the plane below the glass substrate.
  • GaN is an ideal material for electron injection into OLEDs, based both on what is known of the material in the literature, and what we have discovered in our laboratory.
  • the physical properties of GaN are catalogued in: S. Strife and H. Morkoc, "GaN, AIN and InN: a review", Journal of Vacuum Science and Technology B, Vol. 10, 1992, pp. 1237-1266 and "Properties of Group III Nitrides", edited by James H. Edgar, (The Institution of Electrical Engineers, London 1994).
  • the properties of GaN as a transparent conductor have been described by H.
  • Mechanical hardness GaN can be deposited at low temperatures via magnetron sputtering, laser ablation, plasma enhanced molecular beam deposition (PEMBD) or other related techniques in which the energy required to create a reactive nitrogen radical is supplied from some external stimulus, and not thermal energy at the substrate.
  • PEMBD plasma enhanced molecular beam deposition
  • thermally evaporated Ga atoms react with low kinetic energy nitrogen radicals at the substrate surface is our preferred method due to the small amount of chemical and/or kinetic damage endured by the substrate and the large supply of reactive nitrogen species created by the plasma.
  • Ga can be supplied from thermally evaporated elemental metal, or from a Ga containing compound or gas.
  • Active N is supplied by the plasma excitation which excites and cracks a N bearing gas, typically N 2 , NH 3 , hydrazine.
  • a N bearing gas typically N 2 , NH 3 , hydrazine.
  • undoped GaN has a resistivity of roughly 10 Ohm-cm when grown at room temperature.
  • OLEDs incorporating a GaN cathode grown onto the organic layer stack show comparable properties to inverted structures in which the GaN cathode is grown first, demonstrating that GaN can be grown by the PEMBD technique without damaging the organic layer below.
  • the temperature at which the GaN is grown should be below 150 degree centigrade.
  • Figure 4 is a transmission spectrum of one such thin film. These data indicate that low temperature amorphous GaN, much like crystalline GaN, has a wide bandgap energy of 3.3 - 3.4 eV, making it highly transparent to visible light.
  • a clean GaN surface was prepared onto which a thin layer of Alq3 was vacuum deposited.
  • Ultraviolet Photoemission Spectroscopy can resolve the relative positions in energy of the GaN valence band and the Alq3 highest occupied molecular orbital (HOMO).
  • GaN conduction band Further confirmation of the favorable energy positioning of the GaN conduction band comes from measurements of actual OLED device structures, e.g. a GaN cathode structure having the following layer sequence from the glass substrate up: Glass/ITO/CuPc/NPB/Alq3/GaN/lnGaN/AI.
  • NPB means:
  • OLED devices both in terms of operating voltage and external efficiency.
  • InGaN was added to facilitate ohmic contact from the Al to the GaN .
  • Polymer based OLEDs also show improved device performance when GaN cathodes are formed, which is expected since injection occurs via the same mechanisms in polymers as molecular organic compounds.
  • GaN fulfills the first four points of the above list describing an ideal contact electrode. That GaN fulfills the next three points ( 5-7) is apparent from the technical literature on GaN which is readily available, e.g. in the above referenced review paper by Strite and Morkoc or the book entitled "Properties of Group III Nitrides.”
  • FIG. 6 The simplest embodiment of a GaN cathode OLED, already improved with respect to the state of the art is depicted in Figure 6. From the substrate up, listed in the order of deposition, is a glass/GaN/ETL/HTL/Metal OLED structure. In addition to the lower barrier to electron injection afforded by the cathode 61 comprising GaN formed on the glass substrate 60, the ETL 62 thickness may be reduced as a result of reduced optical quenching and the conventional ITO anode can be replaced by a higher work function metal since the anode 64 must no longer serve as the transparent contact. We note here that the structure depicted in Figure 6 might also benefit from the addition of an additional layer 61.1 (e.g.
  • the preferred embodiment would have a transparent top contact 64, e.g. ITO in the case of a cathode 61 comprising GaN.
  • the organic region 65 of the first embodiment comprises an ETL 62 and HTL 63. It is to be noted that the present Figure and all other Figures are not drawn to scale.
  • substrate 60 glass 0.1 mm-5mm 1 mm
  • FIG. 7 A second embodiment of a GaN cathode device is depicted in Figure 7. From the substrate 70 up, listed in the order of deposition, is a giass/Metal/HTL/EL/ETL/GaN OLED structure. The major difference between Figure 7 and Figure 6 is that the cathode 75 comprising GaN is deposited last on top of the organic layer stack 72-74, which in this case includes a separate emission layer 73 (EL) as is sometimes practiced in the art.
  • EL emission layer 73
  • the cathode 75 might comprise additional layer or layers, e.g. an InGaN layer 75.2, an ITO layer 75.3, might be grown on top of the GaN layer 75.1 in order to reduce the lateral sheet resistance of the contact and improve electron injection from the ITO 75.3 into the GAN 75 1 .
  • Any substrate other than glass can be chosen, even an opaque one.
  • the cathode 75 is preferably designed to be fully transparent for ease of light extraction.
  • the organic region 75 of the second embodiment comprises an ETL 74, a layer 73 suited for electroluminescence (EL) and HTL 72.
  • substrate 60 glass 0.1 mm-5mm 1 mm
  • a third embodiment of the present invention is depicted in Figure 8. From the substrate 80 up, listed in the order of deposition, this embodiment comprises glass/ITO/HTL/ETL/(AI,ln)GaN OLED structure.
  • the GaN has been alloyed with AIN to match the cathode conduction band to the LUMO of the ETL.
  • the improved alignment may be necessary if an ETL is selected which has a higher LUMO energy than the GaN CB.
  • these concepts are equally valid for cathode down structures in which the GaN cathode is grown prior to the organic layers and top anode.
  • GaN has been combined with ITO to improve ohmic contact between the cathode 84.1 and outer cathode 84.3.
  • the organic region 85 of the third embodiment comprises a combined ETL/EL layer 83 and a HTL 82. Table 3: Exemplary details of the third embodiment
  • substrate 80 glass 0.1 mm-5mm 1 mm
  • a fourth embodiment of the present invention is depicted in Figure 9. From the substrate 90 up, listed in the order of deposition, is a glass/ITO/HTL/ETL/TM/GaN OLED structure.
  • the thin metal (TM) 94.1 is chosen either for its transparency, low work function or properties as a chemical, diffusion or protective barrier between the organic ETL and GaN 94.2.
  • the TM may be helpful in improving the alignment of the GaN 94.2 CB to the LUMO of the ETL 93, in which case GaN 94.2 doubles as both an electron injector and an encapsulant for the OLED and TM.
  • the TM 94.1 may improve reliability by inhibiting chemical reactions or diffusion between the organic and the GaN layer 94.2 during or after growth, or as a protective barrier to shield the ETL 93 from degradation caused by the GaN 94.2 deposition
  • these concepts are equally valid for cathode down structures in which the GaN then the TM are grown prior to the organic layers and top contact, and also for (Al.ln)GaN alloys according lo the third embodiment.
  • the organic region 95 of the fourth embodiment comprises a combined ETL/EL layer 93 and a HTL 92.
  • substrate 90 glass 0.1 mm-5mm 1 mm
  • Figure 10 depicts an OLED structure in which a GaN or (AI,ln)GaN cathode encapsulates an embedded TM interlayer near the cathode/organic interface.
  • the thin GaN layer between the TM and the organic stack serves as a chemical and diffusion barrier lo prevent mixing and reactions between the metal and organic materials.
  • the GaN layer between the TM and the organic is thin enough to permit electrons to easily pass from the TM to the organic region by either tunneling or thermionic emission.
  • the organic region 105 of the fourth embodiment comprises a combined ETL/EL layer 103 and a HTL 102.
  • sub-anode 101 ITO 10-300nm 50nm
  • outer cathode 104.5 ITO 10-2000nm 50nm
  • the substrate could be fabricated to contain active Si devices, such as for example an active matrix, drivers, memory and so forth.
  • active Si devices such as for example an active matrix, drivers, memory and so forth.
  • Such a structure can be a very inexpensive small area organic display with high resolution and performance realized in the Si
  • An OLED, OLED arrays or an OLED display may either by grown directly on such a Si substrate carrying Si devices, or it may be fabricated separately and flipped onto the Si substrate later.
  • a problem is the Si metallization.
  • Traditional OLED cathode metals are not stable in Si processes or air.
  • Another problem is that a transparent top contact is needed because Si is not a transparent substrate.
  • the present invention offers a solution to these problems.
  • the disclosed GaN based cathode permits a stable, low voltage contact to be formed on top of the standard Si process metallizations, and are therefore compatible with OLED technology.
  • FIG. 11 An organic array or display structure formed on a Si substrate is illustrated in Figure 11 and described in Ihe following.
  • This display comprises a Si substrate 1 10 which has integrated circuits comprising active and/or passive devices such as memory cells, drivers, capacitors, transistor etc. (these devices are not shown).
  • a stable OLED anode e.g. ITO, Au, Pt, Ni, Cr
  • An OLED, in the cathode-up geometry is deposited on the patterned anodes 111 and Si substrate 1 10.
  • a GaN-based cathode 113 is provided.
  • OLED organic light-emitting diode
  • the OLED may be any color including blue or white.
  • full color might be realized by patterning a color conversion dye array or color filter array on top of the cathode.
  • an Al-metallized Si chip 110 on which ITO anodes 11 1 are patterned may serve as substrate for an OLED array or display 1 12.
  • One such OLED comprises (from the bottom to the top)- a stable anode layer, e.g. ITO 1 11 , a HTL, an organic doped or undoped active region, an ETL, and a cathode 1 13 which comprises GaN.
  • This cathode 113 may for example be composed of the following stack of layers': TM/GaN/lnGaN/ITO.
  • the organic region of the present devices may - in addition to charge transport layers if needed at all - either comprise:
  • FIG. 12 Another array or display embodiment, where the OLEDs 122 have the anode up, is illustrated in Figure 12.
  • OLEDs 122 on top of a Si substrate 120 are schematically shown.
  • the Si substrate 120 is partially covered by Al metal electrodes 121 .1 which inject charge into the GaN-based cathodes 121 .
  • Other areas 120.1 do not conduct current.
  • the Si IC substrate 120 could be planarized during the back end of the Si processing. This approach lowers processing cost because a blanket GaN-based cathode 121 can be deposited immediately before OLED deposition, and does not require additional patterning. As discussed above, this is possible because the intended vertical current must traverse a distance much smaller than the spacings between Al contact pads 121.1.
  • the anode up embodiment on Si of Figure 12 may have advantages compared to the cathode up version of Figure 1 1 which arise from the generally higher hole mobilities in preferred HTL layers compared to electron mobilities in preferred ETL layers. If any damage to the upper organic layer occurs during electrode deposition, or contamination diffuses through the electrode and degrades the HTL, it could still have a higher mobility than the buried and ungraded ETL, and therefore not be the limiting factor in overall current conduction. Simply put, since the HTL initially outperforms the ETL in known OLED devices, the device is less sensitive to the initial stages of degradation of the HTL than the ETL.
  • This display comprises a transparent substrate 130 on top of which amorphous-Si or poly-Si structures are formed using the same technology developed for active matrix liquid crystal displays.
  • the Si is structured to provide thin-film-transistors 131 (TFTs) and other devices, to produce an active matrix.
  • TFTs thin-film-transistors
  • the Si devices 131 formed may then be covered or planarized by special layers 134.
  • Color filters or color converters 132 can be provided, in addition, if the OLEDs 135 emit white or blue light, respectively.
  • the Si devices 131 include structured GaN-based cathodes 133, for example, onto which the OLEDs 135 can be deposited.
  • An advantage of this approach is that entrenched active matrix liquid crystal display (AMLCD) technology can be leveraged in combination with OLEDs to realize inexpensive, high performance AM displays over large areas. Furthermore, clever design permits light to be emitted through the glass substrate 130 so no transparent top contact (anode 136) is needed.
  • the anode 136 may be covered by a cap layer 137.
  • Electron transport/Emitting materials are given.
  • Alq3, Gaq3, Inq3, Scq3, BAIq3 (q means 8-hydroxyquinoline) and other 8-hydroxyquinoline metal complexes such as Znq2, Beq2, Mgq2, ZnMq2, BeMq2, and AIPrq3, for example.
  • These materials can be used as ETL or emission layer.
  • Other classes of electron transporting materials are deficient nitrogen containing systems, for example oxadiazoles like PBD (any many derivatives), triazoles, for example TAZ (1 ,2,4-triazole). These functional groups can also be incorporated in polymers, starburst and spiro compounds. Further classes are materials containing pyridine, pyriimidine, pyrazine and pyridazine functionalities.
  • quinoline, quinoxaline, cinnoline, phthalazine and quinaziline functionalities are well known for their electron transport capabilities.
  • Other materials are cyano-substituted polymers, didecyl sexithiophene (DPS6T), bis-triisopropylsilyl sexithiophene (2D6T), Azomethin-zinc complexes, pyrazine (e.g. BNVP), strylanthracent derivatives (e.g. BSA-1 , BSA-2), non-planar distyrylarylene derivatives, for example DPVBi (see C. Hosokawa and T. Kusumoto, International Symposium on Inorganic and Organic Electroluminescence 1994, Hamamatsu, 42), cyano PPV (PPV means poly(p-phenylenevinylene)) and cyano PPV derivatives.
  • DPS6T didecyl sexithiophene
  • NSD oxadiazole derivatives
  • OXD OXD-1 , OXD-7
  • PDA N,N,N',N ' -tetrakis(m-methylphenul)-1 ,3-diaminobenzene
  • PDA Perylene and Perylene derivatives, phenyl-substituted cyclopentadiene derivatives, 12-phthaloperinone derivatives (PP), squarilium dye (Sq), 1 ,1 ,4,4-tetraphenyl-1 ,3-butadiene (TPBD), sexithiophene (6T), poly(2,4-bis(cholestanoxyl)-1 ,4--phenylene-vinylene (BCHA-PPV),
  • DSA distyryl arylene derivatives
  • naphthalene e.g., 1,3-diphenyl-N,N'-bis-(4-phenylphenyl)-1 , 1 ' biphenyl-4,4 -diamine
  • DSA distyryl arylene derivatives
  • naphthalene e.g., 1,3-diphenyl-N,N'-bis-(4-phenylphenyl)-1 , 1 ' biphenyl-4,4 -diamine
  • DSA distyryl arylene derivatives
  • naphthalene e.g.
  • NSD Quinacridone
  • QA also suited as dopant
  • P3MT poly(3-methylthiophene) family
  • PTCDA 10-perylenetetracarboxylic dianhydride
  • TPD-1 tetra phenyldiaminodiphenyl
  • TPD-2 tetra phenyldiaminodiphenyl
  • PPV and some PPV derivatives poly(2-methoxyl,5-(2'ethyl-hexoxy)-1 ,4-phenylene-vinylene (MEH-PPV), poly(9-vinylcarbazole) (PVK), discotic liquid crystal materials (HPT).
  • blend (i.e. guest host) systems containing active groups in a polymeric binder are also possible.
  • the concepts employed in the design of organic materials for OLED applications are to a large exlent derived from the extensive existing experience in organic photoreceptors.
  • a brief overview of some organic materials used in the fabrication of organic photoreceptors is found in the above mentioned publication of P. Brosenberger and D.S. Weiss, and in Teltech, Technology Dossier Service, Organic Electroluminescence (1995), as well as in the primary literalur.
  • OLEDs have been demonstrated using polymeric, oligomeric and small organic molecules.
  • the devices formed from each type of molecules are similar in function, although the deposition of the layers varies widely.
  • the present invention is equally valid in all forms described above for polymeric and oligomeric organic light emitting devices.
  • Small Molecule devices are routinely made by vacuum evaporation. This is extremely compatible with PEMBD of GaN. Evaporation can be performed in a Bell jar type chamber with independently controlled resistive and electron-beam heating of sources. It can also be performed in a Molecular Beam Deposition System incorporating multiple effusion cells and electron-beam evaporators. In each case, GaN deposition can occur in the same chamber, a vacuum connected chamber, or even a separate chamber if some atmospheric contamination is tolerable. Oligomeric and Polymeric organics can also be deposited by evaporation of their monomeric components with later polymerization via heating or plasma excitation at the substrate. It is therefore possible to alloy these by co-evaporation also, and they are fully compatible with monomeric compounds.
  • polymer containing devices are made by dissolving the polymer in a solvent and spreading it over the substrate either by spin coating or the doctor blade technique. After coating the substrate, the solvent is removed by heating or otherwise.
  • This method allows the fabrication of well defined multilayer structures, provided that the respective solvents for each subsequent layer do not dissolve previously deposited layers.
  • hybrid devices containing both polymeric and evaporated small organic molecules are possible.
  • the polymer film is generally deposited first, since evaporated small molecule layers cannot withstand much processing. More interesting is the possibility of making a polymer/inorganic transport layer on top of which monomeric layers are evaporated, possibly also incorporating alloys. If the polymer is handled in an inert atmosphere prior to introduction to vacuum, sufficient cleanliness for device fabrication is maintained. In any case, the chemical inertness of GaN and other n-d WBS makes it highly tolerant of polymer OLED processing.

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  • Electroluminescent Light Sources (AREA)

Abstract

La présente invention concerne un dispositif électroluminescent comprenant un substrat (60), une anode (64), une cathode (61) et une région organique (62, 63) dans laquelle se produit l'électroluminescence si l'on applique une tension électrique entre ladite anode (64) et ladite cathode (61). La cathode (61) se compose de nitrure de gallium (GaN).
PCT/IB1996/000780 1996-08-08 1996-08-08 Cathodes en nitrure de gallium pour dispositifs electroluminescents et ecrans de visualisation WO1998007202A1 (fr)

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PCT/IB1996/000780 WO1998007202A1 (fr) 1996-08-08 1996-08-08 Cathodes en nitrure de gallium pour dispositifs electroluminescents et ecrans de visualisation

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PCT/IB1996/000780 WO1998007202A1 (fr) 1996-08-08 1996-08-08 Cathodes en nitrure de gallium pour dispositifs electroluminescents et ecrans de visualisation

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EP0996176A1 (fr) * 1998-10-13 2000-04-26 Sony International (Europe) GmbH Méthode de fabrication et structure d'un dispositif d'affichage émetteur de lumière à matrice active
US6316786B1 (en) 1998-08-29 2001-11-13 International Business Machines Corporation Organic opto-electronic devices
US7011955B1 (en) 1999-01-29 2006-03-14 Universitaet Tuebingen Quantitative determination of analytes in a heterogeneous system
DE102006051101A1 (de) * 2006-10-25 2008-04-30 Osram Opto Semiconductors Gmbh Organische Licht emittierende Diode (OLED) mit strukturierter Backelektrode und Verfahren zur Herstellung einer OLED mit strukturierter Backelektrode
WO2008082472A1 (fr) * 2006-12-27 2008-07-10 Eastman Kodak Company Oled doté d'électrode à double couche protectrice
US7843125B2 (en) 2004-01-26 2010-11-30 Cambridge Display Technology Limited Organic light emitting diode
US8822040B2 (en) 2004-02-26 2014-09-02 Dai Nippon Printing Co., Ltd. Organic electroluminescent element
DE10225778B4 (de) * 2001-06-11 2020-06-18 Lumileds Holding B.V. Leuchtstoff umgewandelte, Licht emittierende Anordnung
CN113451515A (zh) * 2021-05-13 2021-09-28 山东大学 一种GaN半导体材料作为双功能层的钙钛矿太阳能电池的制备方法

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EP0448268A2 (fr) * 1990-03-13 1991-09-25 Kabushiki Kaisha Toshiba Dispositif luminescent à semi-conducteur comportant une jonction organique-inorganique

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EP0448268A2 (fr) * 1990-03-13 1991-09-25 Kabushiki Kaisha Toshiba Dispositif luminescent à semi-conducteur comportant une jonction organique-inorganique

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SATO H ET AL: "TRANSPARENT AND CONDUCTIVE GAN THIN FILMS PREPARED BY AN ELECTRON CYCLOTRON RESONANCE PLASMA METALORGANIC CHEMICAL VAPOR DEPOSITION METHOD", JOURNAL OF VACUUM SCIENCE AND TECHNOLOGY: PART A, vol. 11, no. 4, PART 01, 1 July 1993 (1993-07-01), pages 1422 - 1425, XP000403745 *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6316786B1 (en) 1998-08-29 2001-11-13 International Business Machines Corporation Organic opto-electronic devices
US6461885B1 (en) 1998-10-13 2002-10-08 Sony International (Europe) Gmbh Method of fabricating and structure of an active matrix light-emitting display device
EP0996176A1 (fr) * 1998-10-13 2000-04-26 Sony International (Europe) GmbH Méthode de fabrication et structure d'un dispositif d'affichage émetteur de lumière à matrice active
US7011955B1 (en) 1999-01-29 2006-03-14 Universitaet Tuebingen Quantitative determination of analytes in a heterogeneous system
DE10225778B4 (de) * 2001-06-11 2020-06-18 Lumileds Holding B.V. Leuchtstoff umgewandelte, Licht emittierende Anordnung
US7843125B2 (en) 2004-01-26 2010-11-30 Cambridge Display Technology Limited Organic light emitting diode
US8822040B2 (en) 2004-02-26 2014-09-02 Dai Nippon Printing Co., Ltd. Organic electroluminescent element
US8773014B2 (en) 2006-10-25 2014-07-08 Osram Opto Semiconductors Gmbh Organic light emitting diode and method for producing an organic light emitting diode
US8193698B2 (en) 2006-10-25 2012-06-05 Osram Opto Semiconductors Gmbh Organic light emitting diode and method for producing an organic light emitting diode
DE102006051101A1 (de) * 2006-10-25 2008-04-30 Osram Opto Semiconductors Gmbh Organische Licht emittierende Diode (OLED) mit strukturierter Backelektrode und Verfahren zur Herstellung einer OLED mit strukturierter Backelektrode
US7646144B2 (en) 2006-12-27 2010-01-12 Eastman Kodak Company OLED with protective bi-layer electrode
WO2008082472A1 (fr) * 2006-12-27 2008-07-10 Eastman Kodak Company Oled doté d'électrode à double couche protectrice
CN113451515A (zh) * 2021-05-13 2021-09-28 山东大学 一种GaN半导体材料作为双功能层的钙钛矿太阳能电池的制备方法

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