EP0270392B1 - Elektrolumineszenzanzeige mit amorphem hydriertem und karboniertem Silizium - Google Patents

Elektrolumineszenzanzeige mit amorphem hydriertem und karboniertem Silizium Download PDF

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Publication number
EP0270392B1
EP0270392B1 EP87402320A EP87402320A EP0270392B1 EP 0270392 B1 EP0270392 B1 EP 0270392B1 EP 87402320 A EP87402320 A EP 87402320A EP 87402320 A EP87402320 A EP 87402320A EP 0270392 B1 EP0270392 B1 EP 0270392B1
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EP
European Patent Office
Prior art keywords
layer
display device
electroluminescent
photoconductive layer
photoconductive
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP87402320A
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English (en)
French (fr)
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EP0270392A1 (de
Inventor
Pascal Thioulouse
Ionel Solomon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ministere des PTT
France Telecom R&D SA
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Ministere des PTT
Centre National dEtudes des Telecommunications CNET
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B33/00—Electroluminescent light sources
    • H05B33/12—Light sources with substantially two-dimensional radiating surfaces

Definitions

  • the present invention relates to an electroluminescent display device using hydrogenated and carbonated amorphous silicon.
  • the device of the invention is not necessarily a memory effect, as will be better understood later, it is all the same this property which is most often sought in practice. We can therefore briefly recall what it consists of. It is said that a display device has a memory effect if its electro-optical characteristic (luminance-voltage curve) has hysteresis. For the same voltage located inside the hysteresis loop, the device could thus have two stable beings: is on or on. Plasma and alternately excited screens have such a characteristic of bistability, which is currently widely used.
  • a memory effect display to display a still image, it is sufficient to apply simultaneously and continuously to the entire screen a so-called maintenance voltage.
  • the latter can be a sinusoidal signal or in the form of slots for example.
  • the form and frequency of this maintenance signal can be chosen independently of the complexity of the screen, in particular the number of lines of display points. There is therefore in principle no limit to the complexity of a memory effect display screen.
  • ACTFEL capacitive coupling
  • the PC-EL memory effect the principle of which is as follows.
  • the photoconductor When the device is in the steady state, the photoconductor is not very conductive and retains a large part of the voltage V applied to the assembly. If one increases V to a value Von such that the voltage present at the terminals of the electroluminescent layer exceeds the electroluminescence threshold, the PC-EL device switches to the on state. The photoconductor is then lit by the electroluminescent structure and goes into the conductive state. The voltage across its terminals drops and this results in an increase in the voltage available for the electroluminescent structure. To switch off a PC-EL device, it suffices to reduce the total voltage V to a value Voff lower than Von: this gives a luminance-voltage characteristic comprising a hysteresis.
  • FIG. 1 It comprises a glass substrate 10 on which is deposited an electrode 12, for example made of ITO (tin and indium oxide), a first dielectric layer 14, an electroluminescent layer 16, for example in ZnS: Mn, a second dielectric layer 18, a photoconductive layer 20 consisting of a stack of layers n + - nn + , made of amorphous silicon hydrogenated a-Si: H and finally an electrode 22, for example of aluminum.
  • the electrodes 12 and 24 are connected to a voltage source 24.
  • the layers PC and EL are thin layers, the thickness of which is of the order of a micron.
  • the n + layers, heavily doped n and of very small thickness have the role of allowing a quasi-ohmic electronic injection into the so-called intrinsic n layer.
  • this quasi-ohmic injection is obtained, it is the electrical and photoconductive characteristics of the intrinsic layer which first determine the behavior of the stack n + - nn + , called here "photoconductive layer", and the memory characteristics. of the PCEL device.
  • Such a structure is simple to produce because it does not require an optical screen or additional etching steps. Furthermore, the current-voltage behavior of the thin layer photoconductor in the dark is highly non-linear and reproducible. The beneficial consequences are that the electrical ignition of the device is always easy, that the hysteresis depends only slightly on the excitation frequency and that the reproducibility of the hysteresis margin from one manufacturing to another is guaranteed. .
  • the inventors have also studied the question of the sensitivity spectrum of a photoconductive material. This spectrum is directly linked to the width of the forbidden band of the material used, its intensity depends on the characteristics of the centers of recombination of the electron-hole pairs generated by photo-excitation (energy depth, effective capture section, trapping time, etc. .). For an optimal PC-EL memory effect, it would be desirable to adapt the spectrum of the photoconductor to that of the electroluminescent structure, so as to improve the optical coupling between the EL and PC layers. But in a system using a-Si: H, there is no possibility of carrying out this adaptation.
  • This material is hydrogenated and carbonated amorphous silicon whose formula is a-Si x C 1-x : H.
  • the invention relates to an electroluminescent display device comprising, on an insulating support an electroluminescent layer and a photoconductive layer, these layers being stacked one on the other, all of these two layers being interposed between two systems of electrodes connected to an electric voltage source allowing the excitation of certain zones of the light-emitting layer, this device being characterized by the fact that the photoconductive layer is made of hydrogenated and carbonated amorphous silicon ⁇ -SixC, _x : H with 1-x between 0.05 and 0.50.
  • the photoconductive layer will consist of an intrinsic layer n of hydrogenated and carbonated amorphous silicon a-Si x C 1-x : H, optionally inserted between two necks. ches n + of quasi-ohmic injection, also in hydrogenated and carbonized amorphous silicon a-Si y C 1-y : H.
  • Photoconductivity drops at short wavelengths (high energies) due to the absorption of radiation in the material.
  • a characteristic of the photoconductivity spectrum of a-SixC 1-x : H is the energy E 04 (in Ev) at which the absorption coefficient a is 10 4 cm -1 . It is this energy which is represented on figure 3,
  • 1-x is preferably between 0.05 and 0.50.
  • the carbon concentration [C] / [C] + [Si] is between 5% and 50%.
  • the emission wavelengths used for the polychrome display range from approximately 450 nm for blue to approximately 640 nm for red.
  • An adaptation to such spectra can be obtained by taking 1-x equal to 0.50 for blue and 0.05 for red, respectively.
  • the photoconductive layer can give an electroluminescent structure an excellent display contrast due to the accompanying "black layer” effect.
  • the photoconductive layer in fact masks the rear aluminum electrodes, absorbs ambient light and prevents its reflection on the electrodes.
  • the principle of using an absorbent layer is naturally known. It is described for example in the publication of the inventors cited above, as well as in the American patent US-A-3,560,784. But in these previous documents, the "black layer” is sometimes a-Si: H, sometimes a dielectric, in other words bodies of composition, therefore of property, given. We cannot therefore play freely on the optical properties of these bodies.
  • the refractive index in a wide range (2.0 to 3.6) by acting on 1-x and optically adapt the black layer to the other layers, for example to the dielectric layer which adjoining and which may be Ta 2 O 5 with index 2.1 or with the electroluminescent layer, which may be ZnS with index 2.35. This minimizes the reflection of ambient light by the photoconductive layer-underlying layer (insulator or electroluminescent layer).
  • a layer of a-Si: H with phosphorus (P) makes it possible to very significantly increase the density of free carriers: up to 10 18 ⁇ 10 19 cm- 3 . It is this high density of free carriers which ensures quasi-ohmic electronic injection into the intrinsic layer.
  • the ohmic conductivity of such layers n + is so high (10 -2, 10 -3 ⁇ -1 cm -1) it causes lateral parasitic conduction phenomena in PCEL materials screens.
  • the incorporation of C into the n + layer makes it possible to significantly reduce the conductivity without significantly modifying the density of free carriers.
  • the incorporation of carbon into the a-Si: H has significant positive effects both for the intrinsic layer n and for the layers n + possibly introduced into the photoconductive structure.
  • the layers of hydrogenated and carbonated amorphous silicon are deposited by glow discharge ("glow discharge") from a mixture of silane (SiH 4 ) and methane (CH 4 ).
  • glow discharge a mixture of silane (SiH 4 ) and methane (CH 4 ).
  • CH 4 mixture content varies in a range from 0 to 60%
  • the carbon 1-x content in the deposited layer varies from 0 to 0.2.
  • FIGS. 2 and 3 make it possible to better specify the experimental conditions to be implemented to obtain certain performances.
  • the abscissa axis corresponds to the concentration C of methane to be used in the methane-silane gas mixture.
  • the ordinate axis corresponds to the refractive index n in FIG. 2 and to the energy E04 of the absorption band of the photoconductor expressed in electron volts in FIG. 3.
  • adjusting 1-x to optimize the DOS, resistivity, photoconductivity, spectrum, index, etc. does not in any way exclude the adjustment of the operating conditions of deposition (temperature of the substrate, power of the plasma, etc.). This adjustment makes it possible to perfect the effects of the presence of carbon, or on the contrary, to compensate for this action. This is the case, for example, when 1-x has been chosen to adjust the photoconductivity spectrum and / or the index and we also want to corrode the DOS, the resistivity and the photoconductivity which result from this choice.
  • n + layers of a-Si 1-y C y : H will be obtained for example by adding to the mixture of [SiH 4 ] - [CH 4 ] an adequate concentration of [PH 3] (typically 0.5%).
  • the invention is applicable to any type of electroluminescent structure in thin layers or based on powder, and with continuous or alternative excitation, this although the example described relates to electroluminescence in thin layers with alternative excitation.

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  • Electroluminescent Light Sources (AREA)
  • Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Claims (6)

1. Elektrolumineszenzanzeige mit einer Elektrolumineszenzschicht (16) und einer Photoleiterschicht (20) auf einem isolierenden Träger (10), wobei diese Schichten übereinander angeordnet sind, wobei die Anordnung dieser beiden Schichten zwischen zwei Elektrodensystemen (12, 22) angeordnet ist, die mit einer elektrischen Spannungsquelle (24) verbund sind, die die Anregung von bestimmten Bereichen der Elektrolumineszenzschicht erlaubt, wobei die Anzeige gekennzeichnet ist durch die Tatsache, daß die Photoleiterschicht aus hydrogeniertem und karboniertem, amorphem Silizium a-SixC1-x:H besteht, wobei 1-x zwischen 0,05 und 0,50 liegt.
2. Anzeige nach Anspruch 1, gekennzeichnet durch die Tatsache, daß 1-x zwischen 0,10 und 0,35 liegt.
3. Anzeige nach Asnpruch 2, gekennzeichnet durch die Tatsache, daß die Photoleiterschicht einer Dicke kleiner als 2 Mikrometer hat und daß die Anzeige mit dem Speichereffekt des PC-EL-Typs ausgestattet ist.
4. Anzeige nach Anspruch 1, gekennzeichnet, durch die Tatsache, daß 1-x aus einem der folgenden Bereich ausgewält wird: 0,05-0,15/ 0,10-0,35 und 0,25-0,50, wobei das Empfindlichkeitsspektrum der Photoleiterschicht dann an das Spektrum des von der Elektrolumineszenzschicht ausgestrahlten Lichts angepaßt ist, wobei dieses Spektrum jeweils einer der drei Grundfarben rot, grün, blau entspricht und der PC-EL-Speichereffekt dann in jeder Farbe erzeugte werden kann.
5. Anzeige nach Anspruch 1, gekennzeichnet durch die Tatsache, daß 1-x zwischen 0,20 und 0,50 liegt.
6. Anzeige nach Anspruch 6, gekennzeichnet durch die Tatsache, daß 1-x außerdem so ausgewählt wird, daß der spezifische Wiederstand der Photoleiterschicht über 1011 Qcm liegt, daß die Photoleitfähigkeit dieser Schicht praktisch Null ist und daß ihr Brechungsindex unter 3 liegt, wobei dann die Photoleiterschicht die Rolle einer Absorberschicht spielt, die ein Anzeige mit erhöhtem Kontrast ermöglicht.
EP87402320A 1986-10-23 1987-10-16 Elektrolumineszenzanzeige mit amorphem hydriertem und karboniertem Silizium Expired - Lifetime EP0270392B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8614715 1986-10-23
FR8614715A FR2605777B1 (fr) 1986-10-23 1986-10-23 Dispositif d'affichage electroluminescent utilisant du silicium amorphe hydrogene et carbone

Publications (2)

Publication Number Publication Date
EP0270392A1 EP0270392A1 (de) 1988-06-08
EP0270392B1 true EP0270392B1 (de) 1991-01-16

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EP87402320A Expired - Lifetime EP0270392B1 (de) 1986-10-23 1987-10-16 Elektrolumineszenzanzeige mit amorphem hydriertem und karboniertem Silizium

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Country Link
US (1) US4877995A (de)
EP (1) EP0270392B1 (de)
JP (1) JPS63170895A (de)
DE (1) DE3767456D1 (de)
FR (1) FR2605777B1 (de)

Families Citing this family (24)

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Publication number Priority date Publication date Assignee Title
US5156924A (en) * 1988-12-29 1992-10-20 Sharp Kabushiki Kaisha Multi-color electroluminescent panel
FR2643180B1 (fr) * 1989-02-10 1991-05-10 France Etat Dispositif d'affichage monochrome a memoire du type photoconducteur-electroluminescent
FR2644920B1 (fr) * 1989-03-21 1993-09-24 France Etat Dispositif d'affichage polychrome a memoire du type photoconducteur-electroluminescent
FR2645998B1 (fr) * 1989-04-12 1991-06-07 France Etat Ecran d'affichage electroluminescent a memoire et a configuration particuliere d'electrodes
US5264714A (en) * 1989-06-23 1993-11-23 Sharp Kabushiki Kaisha Thin-film electroluminescence device
US5043632A (en) * 1990-04-13 1991-08-27 Westinghouse Electric Corp. TFEL edge emitter structure with uniform light emission filter
JPH04368795A (ja) * 1991-06-14 1992-12-21 Fuji Xerox Co Ltd 薄膜トランジスタ内蔵薄膜ｅｌ素子
US5243332A (en) * 1991-10-31 1993-09-07 Massachusetts Institute Of Technology Information entry and display
JPH06160850A (ja) * 1992-11-26 1994-06-07 Sharp Corp 液晶表示装置
US5552679A (en) * 1993-07-15 1996-09-03 International En-R-Tech Incorporated Electroluminescent and light reflective panel
WO1996033594A1 (en) * 1995-04-18 1996-10-24 Cambridge Display Technology Limited Electroluminescent device
JP2739844B2 (ja) * 1995-05-19 1998-04-15 日本電気株式会社 薄膜トランジスタアレイ
EP0812526B1 (de) * 1995-12-30 2001-08-08 Casio Computer Co., Ltd. Anzeigervorrichtung für anzeigeoperation gemäss lichtsignal und steuerverfahren dafür
US6965196B2 (en) * 1997-08-04 2005-11-15 Lumimove, Inc. Electroluminescent sign
GB2350926A (en) * 1999-05-27 2000-12-13 Seiko Epson Corp Monolithic,semiconductor light emitting and receiving device
US20010042329A1 (en) * 2000-04-13 2001-11-22 Matthew Murasko Electroluminescent sign
US20020159246A1 (en) * 2001-03-21 2002-10-31 Matthew Murasko Illuminated display system
US7048400B2 (en) * 2001-03-22 2006-05-23 Lumimove, Inc. Integrated illumination system
ATE377257T1 (de) 2001-03-22 2007-11-15 Lumimove Inc Beleuchtetes anzeigesystem und prozess
AU2002345988A1 (en) * 2001-06-27 2003-03-03 Lumimove, Inc. Electroluminescent panel having controllable transparency
US7358658B2 (en) * 2002-03-08 2008-04-15 Chien-Min Sung Amorphous diamond materials and associated methods for the use and manufacture thereof
JP2005317439A (ja) * 2004-04-30 2005-11-10 Seiko Epson Corp 表示パネル及び表示装置
FR2983438B1 (fr) * 2011-12-05 2014-03-14 Renault Sas Dispositif d'eclairage pour vehicule automobile
CN103247731A (zh) * 2013-04-16 2013-08-14 苏州瑞晟太阳能科技有限公司 一种基于纳米材料的新型光控发光二极管

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US3560784A (en) * 1968-07-26 1971-02-02 Sigmatron Inc Dark field, high contrast light emitting display
US4695717A (en) * 1984-04-24 1987-09-22 Canon Kabushiki Kaisha Semi-conductor device and electronic apparatus using the same
FR2574972B1 (fr) * 1984-12-18 1987-03-27 Thioulouse Pascal Dispositif d'affichage a effet memoire comprenant des couches electroluminescente et photoconductrice superposees
US4675265A (en) * 1985-03-26 1987-06-23 Fuji Electric Co., Ltd. Electrophotographic light-sensitive element with amorphous C overlayer
FR2595741A1 (fr) * 1986-03-17 1987-09-18 Lefloch Maurice Support de garde-corps filant en bordure de plancher

Also Published As

Publication number Publication date
FR2605777B1 (fr) 1989-02-17
EP0270392A1 (de) 1988-06-08
FR2605777A1 (fr) 1988-04-29
JPS63170895A (ja) 1988-07-14
US4877995A (en) 1989-10-31
DE3767456D1 (de) 1991-02-21

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