Classifications

• • 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
  • H10K59/875—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
  • 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
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/19—Tandem 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
  • H10K50/858—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
  • 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
  • H10K59/8051—Anodes
  • H10K59/80515—Anodes characterised by their shape
• • 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
  • H10K59/80521—Cathodes characterised by their shape
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
  • H10K71/20—Changing the shape of the active layer in the devices, e.g. patterning
  • H10K71/231—Changing the shape of the active layer in the devices, e.g. patterning by etching of existing layers
• • 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
  • H10K2102/302—Details of OLEDs of OLED structures
  • H10K2102/3023—Direction of light emission
  • H10K2102/3026—Top emission

Definitions

• the invention relates to an organic light-emitting diode (OLED), more particularly to the emission type from above.
• OLED organic light-emitting diode
• Such a diode can be applied, in particular, to the display (OLED screens) but also lends itself to other applications such as lighting
• the invention also relates to a display device, such as an OLED screen, comprising a plurality of such diodes.
• An OLED consists of a stack of semiconductor organic layers comprising at least one emitting layer, located between two electrodes, very often metallic.
• the organic stack consists of at least one hole transport layer, an emission layer (electroluminescent) and an electron transport layer.
• the thickness of the organic zone is generally set around 100 nm, so as to form a half-wave Fabry-Perot cavity for the visible (the optical index of the organic layers is typically of the order of 1, 7).
• the application of a potential difference between the electrodes injects into the organic stack electrons and holes that recombine radiatively in the emissive layer.
• the emitters are at a relatively small distance from the electrodes vis-à-vis the wavelength, which generates the excitation of plasmons on the surface of the electrodes, in addition to the useful radiative vertical Fabry-Perot mode.
• These plasmons are planar guided modes, totally absorbed by the metal after a certain distance of lateral propagation.
• WO 2014/191733 discloses a top-emitting organic electroluminescent diode (i.e., the surface opposite to that of the substrate), wherein the upper electrode, through which light is emitted, is periodically structured so as to form a diffraction grating.
• Document US 2013/0153861 describes an organic electroluminescent diode emitting from below (that is to say through the substrate) in which it is the lower electrode which is structured.
• the document WO 2014/069573 A1 describes a low-emission organic electroluminescent diode in which the lower electrode comprises at least one region in electrical contact with the stack of organic layers and the region or regions in contact with the Organic layers have a suitable geometry allowing the excitation of a plasmon mode at the emission wavelength.
• the coupling with the network makes it possible, in a manner known per se, to extract the plasmons and the Fabry-Perot modes, thus improving the radiative efficiency.
• the invention aims to overcome the disadvantages of the prior art. More particularly, it aims to provide an organic light emitting diode, especially at the top, having a higher radiative efficiency of what is made possible by the prior art.
• this object is achieved by using a thinned organic stack, unable to withstand FabryPriot modes at its emission wavelengths, and a lower electrode structured as conductive pads of suitable dimensions.
• the conductive pads form, with the continuous upper electrode, resonators for the plasmons.
• localized plasmon modes (standing waves) are generated which are diffracted by the edges of the pads and couple with radiated electromagnetic modes that propagate outside the OLED.
• the operating principle is fundamentally different from that of a conventional Fabry-Perot cavity OLED and that the plasmons, instead of being a source of losses, are the origin of the light emission. This is made possible by the fact that these are localized, non-propagative plasmons as in the prior art.
• An OLED according to the invention has a narrower emission spectrum than that of a conventional diode comprising the same electroluminescent layer, the emission peak depending on the geometry of the conductive pads.
• An object of the invention is therefore an organic electroluminescent diode comprising a first electrode, a stack of semiconductor organic layers, comprising at least one electroluminescent organic layer, deposited above said first electrode and a second electrode deposited on a surface.
• said stack opposite said first electrode, the first and the second electrode and the stack of semiconductor organic layers forming a Fabry-Perot type optical cavity, characterized in that said stack of semiconductor organic layers has an insufficient thickness to allow the existence of a Fabry-Perot mode in said cavity at at least one emission wavelength of said organic electroluminescent layer, and in that said first electrode comprises at least one region in electrical contact with the stack of semiconductor organic layers, surrounded by one or more electrically isolated regions of said stack, said or each said region in electrical contact with the stack having a geometry adapted to allow excitation of a localized plasmon mode at said emission wavelength of said organic electroluminescent layer.
• said or each said region of the first electrode in electrical contact with the stack of semiconductor organic layers may have at least one lateral dimension equal to
• said lateral dimension may be equal to ⁇
• organic light emitting diode comprising:
• Yet another object of the invention is a display device comprising a matrix of first electrodes, a stack of semiconductor organic layers, comprising at least one organic electroluminescent layer, deposited above said first electrode and a second electrode. deposited on a surface of said stack opposite to said matrix of first electrodes, each first electrode forming, with the second electrode and the stack of semiconductor organic layers, a Fabry-Pérot type optical cavity, characterized in that:
• said stack of semiconducting organic layers is insufficient in thickness to allow existence a Fabry-Perot mode in said cavities in at least a portion of the emission spectrum of said organic electroluminescent layer;
• said matrix comprises a plurality of families of first electrodes, the first electrodes of the same family having geometries adapted to allow excitation of a localized plasmon mode at the same wavelength of said emission spectrum of said organic layer electroluminescent, different from that of other families.
• said or each said first electrode may have at least
• a lateral dimension equal to i) - ; or m is an integer
• ⁇ said wavelength and n eff an effective refractive index for plasmons located between the electrodes in the stack of semiconductor organic layers.
• said lateral dimension may be equal to _
• Yet another object of the invention is a method of manufacturing such a display device comprising:
• FIG. 2 a graph of the radiative efficiency of the OLED of FIG. 1 as a function of the emission wavelength
• FIG. 3 an OLED according to one embodiment of the invention.
• FIG. 4 a graph of the radiative efficiency of the OLED of FIG. 3 at the wavelength of 550 nm as a function of the thickness of its stack of semiconductor organic layers;
• FIG. 5 a graph of the radiative efficiency of the OLED of FIG. 3 as a function of the emission wavelength
• FIG. 6 a display device according to another embodiment of the invention.
• the organic light-emitting diode of FIG. 1 (which is not to scale) comprises, starting from the bottom:
• SUB substrate which can be for example glass or silicon.
• a lower electrode EL1 made of AlCu alloy, deposited
• This electrode is opaque and can be relatively thick (several hundreds of nanometers, even a few micrometers).
• a TiN CT buffer layer deposited for example by
• PVD PVD
• PECVD Pasma-Enhanced Chemical Vapor Deposition
• ALD Atomic Layer Deposition
• An organic stack EO deposited for example by liquid or PVD, typically between 80 and 300nm, for example 100 nm.
• an electroluminescent layer having an emission centered at the wavelength of 550 nm. The figure does not show this layer, but only a point emitter (a point of the layer) EP.
• the reference RE represents the light radiation emitted by the point emitter and propagating in a direction substantially normal to the surface of the substrate.
• the thickness of the stack EO is chosen to be equal to ⁇ / 2 ⁇ 0 ⁇ _ ⁇ , where ⁇ is a wavelength belonging to the emission spectrum of the electroluminescent layer (preferably the length d central wave, or corresponding to the peak emissivity) and n 0 i_ED the average refractive index of the stack at this wavelength.
• ⁇ is a wavelength belonging to the emission spectrum of the electroluminescent layer (preferably the length d central wave, or corresponding to the peak emissivity) and n 0 i_ED the average refractive index of the stack at this wavelength.
• the stack forms a Fabry-Perot cavity for the emitted radiation.
• the PL reference designates the plasmons guided by the interfaces between the organic stack and the lower and upper electrodes, sources of losses.
• An upper electrode EL2 deposited above the organic stack, in Ag and having a thickness of 10 nm - sufficiently low to be substantially transparent.
• FIG. 2 is a graph of the radiative efficiency ⁇ ⁇ of the OLED of FIG. 1 as a function of the emission wavelength ⁇ .
• the radiative efficiency is defined as the ratio between the radiated power Prad and the sum of this same radiated power and the power P a bs absorbed by the metal electrodes:
• Figure 3 shows a sectional view of an OLED according to one embodiment of the invention. It differs from that of Figure 1 by two main characteristics:
• the thickness of the organic stack EO is reduced from 100 to 50 nm. This has two consequences: on the one hand, this thickness is insufficient to allow the existence of Fabry-Perot modes in the visible spectrum, where the emission of the electroluminescent layer is located; on the other hand, the upper and lower electrodes are close enough that their plasmon modes are strongly coupled.
• the lower electrode EL1 is structured in a set of conductive pads PC, separated by insulating regions - in practice cavities or grooves obtained by etching the electrode - and the buffer layer covering it - and filled with a dielectric material such as SiO 2 or a resin.
• the geometry of the PC conductive pads is chosen so that a localized plasmon mode PLL can be confined between a pad and the upper electrode portion EL2 directly opposite.
• the studs often have a circular or square shape, or even polygonal; in this case, they must have a lateral dimension L (side in the case of a square, diameter for a circle, distance between two opposite sides for a polygon ”) equal to half of an odd multiple of one wavelength ⁇ of the emission spectrum of the electroluminescent layer, divided by an effective refractive index:
• n eff is higher but close to the average index of the organic stack.
• the width of a pad optimized for emission at 550 nm is about 200 nm.
• the plasmonic resonators formed by the pads are independent of each other.
• the separation between pads is not critical, as long as it is sufficient to avoid coupling between the plasmons located at different pads; typically it will be greater than or equal to 20% of the width of the pads.
• the structuring is periodic, and at the limit the OLED can comprise a single pad (of course, this implies a very concentrated light emission on a very small surface, and therefore a low total brightness) .
• the manufacturing method of the device of FIG. 3 is close to that of a conventional OLED, except that it also comprises a step of structuring the lower electrode and depositing a thinner organic layer.
• the structuring takes place in several stages. The first is an etching of the metal layer and the buffer layer CT covering it. At the end of this etching is performed the deposition of a thick layer of dielectric, typically Si0 2 , sufficiently thick to fill the holes between the metal parts. Finally to come clear the contacts EL1 electrodes, is carried out a planarization, for example of the chemical-mechanical planarization (CMP) type. Subsequently, the organic stack EO (but making sure that its thickness takes the desired value, much lower than in the prior art) is deposited in a conventional manner, the second electrode and the electrode structure. encapsulation.
• CMP chemical-mechanical planarization
• the device comprises an array of lower electrodes belonging to two families: the electrodes EL1a have a first lateral dimension La, and are adapted to allow the emission of a first radiation REa; ELb electrodes have a second lateral dimension Lb, greater than La, and are adapted to allow the emission of a second radiation REb of central wavelength greater than that of REa.
• Electrodes are deposited on the same substrate SUB and separated by isolated regions RI; they are covered with a common organic stack EO (references EPa, EPb represent point emitters inside this stack), a common upper electrode EL2 and an encapsulation layer, such as the OLED of
• EO organic stack
• EPa, EPb represent point emitters inside this stack
• EL2 common upper electrode
• encapsulation layer such as the OLED of
• display devices comprising regular arrangements of lower electrodes of three or more different families will be used.
• optimized electrodes may be used to emit predominantly red, green and blue radiation, respectively, so as to provide an RGB screen in which each individual electrode corresponds to a sub-pixel.
• the colors obtained according to the invention are insufficiently saturated to avoid the need for color filtering subpixels; however, the invention makes it possible to reduce the constraints on this filtering and / or to improve the rendering of the colors.
• the organic stack, the second electrode and the encapsulation structure are conventional elements and can be modified in known manner.
• the lower electrode generally serves as the cathode and upper anode electrode, but the reverse is also possible.
• the thicknesses of the different layers are not critical, provided that the organic stack is sufficiently thin.
• the conductive pads may have more complex shapes than those hitherto considered, for example shapes that can not simply be characterized by a lateral dimension. What is important is that they can support a plasmon mode located at least one emission wavelength of the light emitting layer of the OLED.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Electroluminescent Light Sources (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

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• 2017
  • 2017-03-15 FR FR1752095A patent/FR3064114A1/fr not_active Withdrawn
• 2018
  • 2018-03-14 KR KR1020197026172A patent/KR20190124234A/ko unknown
  • 2018-03-14 CN CN201880017609.6A patent/CN110431683A/zh active Pending
  • 2018-03-14 US US16/491,139 patent/US20200013983A1/en not_active Abandoned
  • 2018-03-14 WO PCT/EP2018/056452 patent/WO2018167177A1/fr unknown
  • 2018-03-14 JP JP2019550754A patent/JP2020515009A/ja active Pending
  • 2018-03-14 EP EP18711102.6A patent/EP3596760A1/fr not_active Withdrawn

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