CN100473247C - Electroluminescence element - Google Patents
Electroluminescence element Download PDFInfo
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- CN100473247C CN100473247C CNB2005101079469A CN200510107946A CN100473247C CN 100473247 C CN100473247 C CN 100473247C CN B2005101079469 A CNB2005101079469 A CN B2005101079469A CN 200510107946 A CN200510107946 A CN 200510107946A CN 100473247 C CN100473247 C CN 100473247C
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Abstract
An EL element includes, between an anode and a cathode, an emissive element layer including a plurality of emissive layers. The emissive element layer includes two or more organic layers containing a hole transporting compound, and one or more of the plurality of emissive layers contain the hole transporting compound. The concentration of the hole transporting compound in the organic layer which is formed closest to the electron injecting electrode among the organic layers containing the hole transporting compound is lower than the concentration of the hole transporting compound in the organic layer which is formed closest to the hole injecting electrode. When three or more organic layers contain a hole transporting compound, the concentration of the hole transporting compound contained in each organic layer can be set such that, as the organic layer is further away from the hole injecting electrode, the concentration is lower. With this setting, the supply amount and supply timing of holes and electrons can be optimized easily with regard to each of the plurality of emissive layers, so that uniform light emission can be generated in any one of the emissive layers.
Description
Technical field
The present invention relates to the formation of electroluminescence (Electroluminescence:EL) element.
Background technology
In recent years, for display elements such as flat display apparatus and light sources, the electroluminescence element of emissive type is subjected to greatly attracting attention, especially can send the illuminant colour of multicolour by the organic compound material that adopts and can reach the luminous organic electroluminescent element of high brightness, this correlative study is carried out just energetically.
Organic electroluminescent element is that the light emitting element layer that contains luminescent layer is set between hole injecting electrode (anode) and electron injection electrode (negative electrode), in light emitting element layer, from anode institute injected holes with combine (Recombination) again from negative electrode institute injected electrons, because of the light emitting molecule that energy excited of combination can be luminous when returning ground state (ground state) again, therefore can utilize this luminous demonstration.
As mentioned above, in organic electroluminescent element, the luminescent organic molecule that can pass through to be adopted obtains the light of all colors.Yet, the color that also exists at present white for example etc. to be realized by single luminous organic material.For the light of described color, realized by the light of combination multicolour.About described white, also the someone proposes, and lamination forms Yellow luminous layer and the blue light-emitting layer with complementary colours relation in 1 element, and by realizing white light at the sodium yellow that each layer obtained and the additive color of blue light.Yet it is efficient luminous to be difficult to make each layer of multilayer luminescent layer to carry out, and the gap between illuminant colour and the reference white is also not little.
In addition,, but still there are the problems such as durability of the organic material of light emitting molecule etc., still dislike not enough as the life-span of element though organic electroluminescent element generally can carry out the luminous of high brightness.When lamination multilayer luminescent layer obtains additive light, measurablely worsen sooner than other luminescent layer to the bigger luminescent layer of luminescent layer that for example luminous efficiency is minimum or injection current, and component life depends on the luminescent layer that the life-span is the shortest.Therefore,, not only need various illuminant colours are developed the luminous organic material that can reach long-life more and higher luminous efficiency, and must reach the optimization of component construction etc. for all illuminant colours.
Summary of the invention
The invention relates to,, also can make luminescent layer luminous efficiently and realize the technology of long-life element even possess the electroluminescence element of multilayer luminescent layer.
The present invention is a kind of electroluminescence element, between hole injecting electrode and electron injection electrode, possesses the light emitting element layer that contains the multilayer luminescent layer, wherein, described light emitting element layer possesses the organic layer that contains the cavity conveying compound more than 2 layers, formation more than 1 layer in the described multilayer luminescent layer contains the described organic layer of described cavity conveying compound, in described organic layer, be formed at the layer of approaching described electron injection electrode described cavity conveying compound contain layer also little that concentration ratio is formed at the most approaching described hole injecting electrode.
About alternate manner of the present invention, in described electroluminescence element, the organic layer that contains described cavity conveying compound exists more than 3 layers; The described cavity conveying compound of described organic layer contain concentration, the described hole injecting electrode of distance is far away, the concentration of this layer is lower.
In addition, described cavity conveying compound for example is an amine derivatives compounds.
About alternate manner of the present invention, in described electroluminescence element, this multilayer luminescent layer possesses: be disposed near the 1st luminescent layer of hole injecting electrode and be disposed at the 1st luminescent layer and described electron injection electrode between the 2nd luminescent layer; Between described the 1st luminescent layer and described hole injecting electrode, possesses hole transporting layer at least; The concentration that contains with the described cavity conveying compound of described hole transporting layer is made as Chi, the concentration that contains with the described cavity conveying compound of described the 1st luminescent layer is made as Cem1, during with the containing concentration and be made as Cem2 of the described cavity conveying compound of described the 2nd luminescent layer, satisfy Cem1-Cem2〉relation of Chi-Cem1.
About alternate manner of the present invention, in described electroluminescence element, in described multilayer luminescent layer, be disposed near the 1st luminescent layer of hole injecting electrode at least and be formed near the luminescent layer of the 1st luminescent layer, respectively contain identical cavity conveying compound.
So, when the organic layer of multilayer contains the cavity conveying compound separately, more near the organic layer of the side of hole injecting electrode, the concentration that contains of this cavity conveying compound heals high, it is lower that the organic layer far away of healing then contains concentration, thus, the hole that can easily carry necessity respectively and measure fully to the multilayer luminescent layer that is formed between hole injecting electrode and the electron injection electrode.
About alternate manner of the present invention, in described electroluminescence element, in described multilayer luminescent layer, possessing the 1st luminescent layer near the hole injecting electrode place, between the 1st luminescent layer and described electron injection electrode, possess the 2nd luminescent layer; Between described the 1st luminescent layer and described hole injecting electrode, possesses hole transporting layer at least; Between described the 2nd luminescent layer and described electron injection electrode, possesses electron supplying layer at least; The electron transport compound of described electron supplying layer, described the 2nd luminescent layer and described the 1st luminescent layer contain concentration, the described electron supplying layer of distance is far away, the concentration of this layer is lower.
By satisfying described relation, in the element that is provided with the multilayer luminescent layer, be not only the hole, also can easily inject electronics equably to each luminescent layer.
About alternate manner of the present invention, in described electroluminescence element, in described multilayer luminescent layer,, possess hole transporting layer and hole injection layer at least being disposed between the 1st luminescent layer and this hole injecting electrode near hole injecting electrode; In described multilayer luminescent layer,, possesses electron supplying layer at least being disposed between the 2nd luminescent layer and this electron injection electrode near electron injection electrode; Thickness with described hole injection layer is made as Lhi, hole mobility is made as μ hi, thickness with described hole transporting layer is made as Lht, hole mobility is made as μ ht, thickness with described the 1st luminescent layer is made as Lem1, hole mobility is made as μ hem1, thickness with described the 2nd luminescent layer is made as Lem2, electron mobility is made as μ hem2, thickness with described electron supplying layer is made as Let, when electron mobility is made as μ et, satisfy the relation of (Lhi/ μ hi)+(Lht/ μ ht)+(Lem1/ μ hem1)=α { (Lem2/ μ hem2)+(Let/ μ et) }, α satisfies 0.5＜α＜2.5.
By setting α, can on same opportunity, make electronics arrive the 1st luminescent layer and make the hole arrive the 2nd luminescent layer easily in the scope that satisfies 0.5 to 2.5.Therefore, can prevent that electronics and hole are only compound on luminescent layer centrality ground on one side produces luminous and non-luminous inconsistent phenomenon on the luminescent layer at another side.
According to the present invention, when the organic layer of multilayer contains common charge-transporting compound, make the amount (concentration) of this charge-transporting compound possess gradient, near the electrode that is required most conveying capacity organic layer improves this amount, and along with the distance electrode far reduces amount.At least be in different 2 layers of organic layer to the distance of electrode, improving concentration near the charge-transporting compound of the layer of electrode.Thus, be formed near the luminescent layer the electrode and be formed at than this situation for luminescent layer at a distance even exist, also can be separately positively with electronics and cavity conveying luminescent layer to both sides, and carry out combination more easily.Therefore, can promote the luminous harmony of each luminescent layer, realize the additive light of desired color, also realize the long-life element of high efficiency in addition easily.
About alternate manner of the present invention, be a kind of electroluminescence element, between hole injecting electrode and electron injection electrode, possesses the light emitting element layer that contains organic compound, wherein, described light emitting element layer possesses the multilayer luminescent layer, in this multilayer luminescent layer,, possesses hole transporting layer at least being disposed between the 1st luminescent layer and this hole injecting electrode near hole injecting electrode; In described multilayer luminescent layer,, possesses electron supplying layer at least being disposed between the 2nd luminescent layer and this electron injection electrode near electron injection electrode; With the required time that arrives this hole till described the 2nd luminescent layer from described hole injecting electrode institute injected holes by described hole transporting layer and described the 1st luminescent layer is Th, and be Te from described electron injection electrode institute injected electrons arrives this electronics till described the 1st luminescent layer by described electron supplying layer and described the 2nd luminescent layer required time, both ratio Th/Te satisfy 0.5＜(Th/Te)＜2.5.
About alternate manner of the present invention, described ratio Th/Te satisfies 1 ≦ (Th/Te)＜2.
So, the ratio that hole or electronics are arrived the required time till each luminescent layer is set at for example 0.5 to 2.5 the scope that satisfies as described, thus, can make electronics arrive the 1st luminescent layer easily and makes the hole arrive the 2nd luminescent layer on same opportunity.Therefore, can prevent electronics and hole only on luminescent layer on one side centrality ground combine again and produces luminous and in the non-luminous inconsistent phenomenon of the luminescent layer of another side, and it is balancedly luminous that the multilayer luminescent layer is distinguished.In addition, be more than 1 and if set the ratio of required time less than 2, then can be really and make any one deck of multilayer luminescent layer of stromatolithic structure luminous efficiently.
About alternate manner of the present invention, described the 1st luminescent layer possesses the cavity conveying function, and described the 2nd luminescent layer possesses the electron transport function.
By satisfying the relation as described, can be in the element that is provided with the multilayer luminescent layer easily hole and electronics be flow into each luminescent layer equably and luminous.
The effect of invention
According to the present invention, can promote the luminous harmony of the multilayer luminescent layer of institute's lamination, and can realize the additive light of purpose color also realizing high efficiency and long-life element in addition easily.
Description of drawings
Fig. 1 has shown the summary profile construction of the electroluminescence element of form of implementation of the present invention.
Fig. 2 has shown a part of summary profile construction of the colour display device of the electroluminescence element that adopts the invention process form.
Fig. 3 has shown the luminescent spectrum of the electroluminescence element of the 1st embodiment.
Fig. 4 has shown the luminescent spectrum of the electroluminescence element of 1-2 comparative example.
Fig. 5 has shown the luminescent spectrum of the electroluminescence element of 2-2 comparative example.
The main element symbol description
100 substrates, 160 interlayer insulating films
180 planarization insulating layers, 200 light emitting element layers
220 hole injecting electrodes (anode), 240 electron injection electrodes (negative electrode)
242 electron injecting layers, 244 metal levels
300 light emitting element layers, 310 hole injection layers
320 hole transporting layers 330 the 1st luminescent layer
340 the 2nd luminescent layers, 350 electron supplying layers
360 electron injecting layers, 500 electroluminescence element
The CF colored filter
Embodiment
Followingly form of implementation of the present invention (hereinafter referred to as form of implementation) is described with reference to accompanying drawing.Fig. 1 is presented at the summary profile construction of the electroluminescence element 500 of this form of implementation that possesses the multilayer luminescent layer between the 1st electrode and the 2nd electrode.
The the 1st and the 2nd electrode, Yi Bian be hole injecting electrode (anode) 220, another side is an electron injection electrode (negative electrode) 240, in the example of Fig. 1, form anode 220 in the side of substrate, negative electrode 240 then be formed on anode 220 relatively to, double team has the light emitting element layer 300 of organic compound therebetween.
Light emitting element layer 300 possesses the organic layer of the multilayer that contains the cavity conveying compound.In addition, this light emitting element layer 300 possesses the multilayer luminescent layer, in this multilayer luminescent layer, being disposed between the 1st luminescent layer 330 and this anode 220 near anode 220, possesses hole transporting layer 320 at least.In the multilayer luminescent layer,, possesses electron supplying layer 350 at least being disposed between the 2nd luminescent layer 340 and this negative electrode 240 near negative electrode 240.The formation of light emitting element layer 300 is that all differences are arranged according to the organic material that adopted etc., in the example of Fig. 1, be side from anode 220, lamination hole injection layer 310, hole transporting layer the 320, the 1st luminescent layer the 330, the 2nd luminescent layer 340 and electron supplying layer 350 in regular turn.
In addition, in this form of implementation,, adopt orange luminescent layer and blue light-emitting layer to be used as luminescent layer, and be set at the 1st luminescent layer 330 and the 2nd luminescent layer 340 respectively in order to realize white luminous according to additive color.Though be not limited to that lamination orange luminescent layer and blue light-emitting layer constitute in regular turn from the side of hole transporting layer, but comparatively ideally be, in the multilayer luminescent layer, the side that the luminescent layer that the cavity conveying function is higher is arranged on anode 220 is used as the 1st luminescent layer 330, and the side that the luminescent layer that the electron transport function is higher is arranged on negative electrode 240 is used as the 2nd luminescent layer 340.
Luminescent layer is not limited to 2 layers, also can be more than 3 layers, in the case, in the multilayer luminescent layer, near the 1st luminescent layer 330 of anode 220 (far away) and between the 2nd luminescent layer 340 near negative electrode 240 (far away) apart from anode 220 apart from negative electrode 240, be provided with the 3rd, the 4th ... .., n luminescent layer.Be arranged on the 1st and the 2nd luminescent layer the centre luminescent layer each other or and the 1st or the 2nd luminescent layer between interlayer, can form other functional layer that has beyond luminous.
About anode 220, for example can adopt the conductive metal oxide material, ITO (Indium Tin Oxide, tin indium oxide) and IZO transparent conductivity materials such as (Indium Zinc Oxide, indium zinc oxides) are particularly arranged.Negative electrode 240 is by based on the metal level 244 of the bigger metal material of work function and be used for reducing the stromatolithic structure that the electron injecting layer 242 of the electron transport resistance barrier of electron supplying layer 350 is formed and constituted.About metal level 244, for example can adopt Al, Ag, MgAl alloy, MgAg alloy, LiAl alloy, LiAg alloy etc.And under the less situation of 350 electron transport resistance barrier, also can omit electron injecting layer 242 from negative electrode 240 toward electron supplying layer, electron injecting layer 242 for example can adopt lithium fluoride (LiF), lithium (Li) etc.
In the example of Fig. 1, in the multilayer luminescent layer, be to form continuously on the hole transporting layer 320 in monolayer constructions will near the 1st luminescent layer 330 of anode, this 1st luminescent layer 330 contains the cavity conveying compound of relative higher concentration.Particularly, it is main material that the 1st luminescent layer 330 adopts the cavity conveying compound, adopt the luminescent material of orange to be used as dopant material, and will about 10 quality % or this dopant material of the concentration below it is doped in the cavity conveying main material and is formed.Just, in the 1st luminescent layer 330, contain the cavity conveying compound that the cavity conveying compound concentrations is approximately (for example about 90 quality %) more than 100 quality % to the 80 quality %.The aromatic amine derivative compound that the cavity conveying compound can adopt described hole transporting layer 320 to be adopted.Luminescent material (dopant material) for orange is not particularly limited, (Rubrene (5 for example can to adopt lycid alkene, 6,11,12-tetraphenylnaphthacene)) and DBzR (5,12-bis (4-(6-methylbenzothiazole-2-yl) phenyl)-6,11-diphenyl naphthacene) (DBzR (5, two (4-(the 6-methylbenzene azoles-2-yl) phenyl)-6 of 12-, 11-diphenyl naphthonaphthalene)).Possess at dopant material under the situation of lighting function and higher cavity conveying, the cavity conveying compound concentrations that can be considered the 1st luminescent layer 330 is almost 100 quality %.
In the example of Fig. 1, in the multilayer luminescent layer, be formed on directly over described the 1st luminescent layer 330 near the 2nd luminescent layer 340 of negative electrode 240, and both contact with the 1st luminescent layer 330 and electron supplying layer 350.The 2nd luminescent layer 340 comprises the electron transport compound of high concentration at least, in this form of implementation, is to adopt described cavity conveying compound and electron transport compound both are used as main material, and adopts blue luminescent material to be used as dopant material.This dopant material can by for example 10% or the concentration below it come main material is mixed.
The main material of the cavity conveying of the 2nd luminescent layer 340 can be identical with described the 1st luminescent layer 330, adopt the aromatic amine derivative compound, main material for electron transport, except the metal-organic complex compound that described electron supplying layer 350 is adopted, also can adopt polycyclc aromatic compound.The metal complex compounds for example can adopt aforesaid aluminium oxyquinoline complex compound and this derivative.Polycyclc aromatic compound for example can adopt anthracene (Anthracene) series compound.
About an example of this anthracene series compound, ADN (9,10-di (2-naphthyl) anthracene) (AND (9,10-two (2-naphthyl) anthracene)) etc. is for example arranged.Described polycyclc aromatic compound for example can adopt to be possessed electron transport and cavity conveying and helps dopant etc. as the 1st luminescent layer 330.In the case help dopant, for example can adopt DPN (5,12-diphenyl naphthacene) (DPN (5,12-diphenyl naphthonaphthalene)) etc.Luminescent material (dopant material) for blueness is not particularly limited, and for example can adopt perylene (Perylene) series compound and pyrene (Pyrene) series compound.
The cavity conveying compound concentrations of the 2nd luminescent layer 340 can be set in 0 quality % to 50 quality %.In addition, the electron transport compound concentrations can be set in 100 quality % to 50 quality %.In addition, for example adopting as Alq
3As the compound with electron transport function and lighting function when being used as the 2nd luminescent layer 340, can adopt the electron transport luminophor of 100 quality % separately.
As mentioned above, in this form of implementation, possessing 2 layers luminescent layer 330,340 and in hole transporting layer 320 and the 1st luminescent layer 330, containing under the situation of cavity conveying compound at least, the cavity conveying compound of the 1st luminescent layer 330 contain concentration be set as than the cavity conveying compound of hole transporting layer 320 to contain concentration lower or equal.Possess simultaneously under lighting function and both situations of cavity conveying function at the luminescent material that the 1st luminescent layer 330 is adopted, the concentration that contains of the cavity conveying compound of the 1st luminescent layer 330 is almost 100 quality %.And in the 2nd luminescent layer 340, also can adopt the cavity conveying compound of a part, even but when adopting, this contain concentration also than the 1st luminescent layer 330 to contain concentration lower.Just, comparatively ideally be, in the organic layer of the multilayer that contains the cavity conveying compound, setpoint distance anode 220 layer far away of healing, it is lower that it contains concentration.When possessing the organic layer of the multilayer that contains the electron transport compound, the near organic layer but setpoint distance negative electrode 240 is healed, the concentration that contains of its electron transport compound heals high.
Organic electroluminescent element 500 constitutes by above stromatolithic structure, and each layer begins lamination in regular turn from anode 220 above transparent insulation substrate such as glass or plastic film 100.Anode 220 for example can be formed by sputtering method, and light emitting element layer 300 and negative electrode 240 for example can form continuously by vacuum vapour deposition.Be used as the display element (light-emitting component) of each pixel of display unit and transistor be set in each pixel being applicable to keep and to control the situation of so-called active-matrix type display unit of the displaying contents of each pixel with this organic electroluminescent element 500, at the interlayer of described substrate 100 and anode 220, the layer of each image element circuit of transistor formed etc. is formed.
In so constituting, be injected in hole injection layer 310 from 220 injected holes of anode, the hole transporting layer 320 of high concentration ground by containing the cavity conveying compound, and arrive the 1st luminescent layer 330.In addition, be used as main material owing to contain the cavity conveying compound of high concentration, therefore the 1st luminescent layer 330 also possesses cavity conveying, so the hole arrives the 2nd luminescent layer 340 by the 1st luminescent layer 330.
On the other hand, from negative electrode 240 (from metal level 244 process electron injecting layers 360) the institute's electron supplying layer 350 of injected electrons high concentration ground, and arrive the 2nd luminescent layer 340 by containing the electron transport compound.As described, the electron transport compound that also contains high concentration owing to the 2nd luminescent layer 340 possesses electron transport, so electronics arrives the 1st luminescent layer 330 by the 2nd luminescent layer 340.
Therefore, in the 1st luminescent layer 330, the hole that comes from anode 220 with from negative electrode 240 through the 2nd luminescent layer 340 and the electronics that arrives combines again, and excite the light emitting molecule of dopant, and when returning ground state, can obtain to send the light of orange by the energy of combination again.In the 2nd luminescent layer 340, combine again with electronics from hole that anode 220 arrives through the 1st luminescent layer 330 from negative electrode 240, excite the light emitting molecule of dopant, and when returning ground state, can obtain to send the light of blueness.In the example of Fig. 1, all penetrate toward outside by the formed substrate 100 of transparent insulation materials such as glass from the side process of transparent anode 220 in the 2nd luminescent layer 340 blue light that is obtained and the orange light that is obtained in the 1st luminescent layer 330.Therefore, externally, because the additive color of blue light and orange light, and can observe out white light.
In this form of implementation, as mentioned above, the organic layer that contains the multilayer of cavity conveying compound at lamination is used as under the situation of light emitting element layer 300, be set at apart from the anode 220 near organic layer of healing, its cavity conveying compound to contain concentration higher.Yet, especially be Chi in the concentration that contains with the cavity conveying compound of hole transporting layer 320, the concentration that contains with the cavity conveying compound of the 1st luminescent layer 330 is Cem1, during with the containing concentration and be Cem2 of the cavity conveying compound of the 2nd luminescent layer 340, comparatively ideal is to satisfy Cem1-Cem2〉relation of Chi-Cem1.
By enlarging the concentration difference between the 1st luminescent layer 330 and the 2nd luminescent layer 340, especially reduce the concentration of Cem2, the cavity conveying of the 2nd luminescent layer 340 can be set at also lower than the 1st luminescent layer 330.When arriving negative electrode 240 if the 2nd luminescent layer 340 is passed in the hole, then this hole becomes idle current, and is unprofitable to luminous.In addition, even combine again with electronics, also, therefore be unprofitable to luminous owing to outside luminescent layer, there is not light emitting molecule usually at the interlayer of the 2nd luminescent layer 340 and negative electrode 240.When the material that has electron transport and a lighting function in employing was used as electron supplying layer 350, it was luminous then to cause electron supplying layer 350 in non-purpose to produce, thereby caused the reduction of colorimetric purity.Therefore, comparatively ideal is the concentration gradient that is set in as described.
Under the situation that forms the luminescent layer more than 3 layers, as mentioned above, be between the 1st luminescent layer 330 and the 2nd luminescent layer 340, to form luminescent layer again.In the case, in the 1st luminescent layer 330, be required higher cavity conveying ability, and comparatively ideal be to set the cavity conveying compound concentrations for example for up to about 100 quality % to 90 quality %.Relatively, be required higher electron transport ability in the 2nd luminescent layer 340, it for example is the higher concentration of 100 quality % to 50 quality % that the electron transport compound is set for.For between the 1st luminescent layer 330 and the 2nd luminescent layer 340 and be formed at,, therefore contain the cavity conveying compound owing to the hole must be sent to the side of the 2nd luminescent layer 340 near the luminescent layer of the 1st luminescent layer 330.The cavity conveying compound of the luminescent layer in the middle of this contain concentration can be set at also lower than the 1st luminescent layer 330, and than described the 2nd luminescent layer 340 to contain concentration also high.All can adopt identical cavity conveying compound near luminescent layer of the 1st luminescent layer 330 (under the situation of the luminescent layer of 2 layers of structure, being the 2nd luminescent layer 340) and the 1st luminescent layer 330.By adopting identical materials, can when for example waiting each layer of lamination light emitting element layer 300, form luminescent layer efficiently and easily adopt identical evaporation to originate with vacuum vapour deposition.
The characteristic of the electroluminescence element of formed form of implementation under described concentration relationship below is described.At first, will inject and be expressed as Th from anode 220 by the required time that hole injection layer 310, hole transporting layer 320 and the 1st luminescent layer 330 arrive the per unit distance in the hole till the 2nd luminescent layer 340.In addition, inject and be expressed as Te from negative electrode 240 by the required time that electron supplying layer 350 and the 2nd luminescent layer 340 arrive the per unit distance of the electronics till the 1st luminescent layer 330, under so representing, in the electroluminescence element 500 of this form of implementation that reaches the optimization concentration as described, ratio (Th/Te) satisfies 0.5＜(Th/Te)＜2.5 relation.Comparatively ideal is to satisfy 1 ≦ (Th/Te)＜2, and better is to satisfy 1.3＜(Th/Te)＜1.7 relation.
The ratio of the arrival the 1st by making hole and electronics and the required time of the 2nd luminescent layer satisfies this relation, hole and electronics is arrived become more approaching the opportunity that opportunity of the 1st luminescent layer 330 and hole and electronics arrives the 2nd luminescent layer 340.
If the gap of described Th and Te is excessive, for example Th is more than 2.5 times of Te, then in the 1st nearest luminescent layer 330 of distance anode, even hole and electronics arrived and produce luminous on much at one opportunity, but when arriving in the hole apart from nearest the 2nd luminescent layer 340 of negative electrode 240, because electronics has passed through the 2nd luminescent layer 340 of electron transport, so the reduction of the probability of the combination again of hole and electronics, and be difficult for producing luminous.Certainly, only luminous if on opposite opportunity in the generation of the 2nd luminescent layer, and can be not luminous in the 1st luminescent layer.Therefore, if the ratio of this required time of optimization not is also only luminous at central a part of luminescent layer even the multilayer luminescent layer then is set, and can't obtain the additive light (being white) of harmonious good purpose at this.Yet, by satisfying the ratio relation of described required time, for example being located at 1.3 to 1.7 scope, arrival reaches consistent opportunity, thereby can make the multilayer luminescent layer luminous harmoniously respectively.At this, the ratio Th/Te that sets required time is that one of more suitable reason more than 1 is, be not only the control that the hole arrives arrival opportunity of the 2nd luminescent layer 340, and can by in light emitting element layer 300 as far as possible thickening cause the layer of the side of concavo-convex more anode because of the influence that is subjected to lower floor, and prevent the broken string of light emitting element layer 300 and promote the poor covering property of section.
In this form of implementation, can consider the charge mobility (cm of charge transport material
2/ Vs) and the concentration of each layer of light emitting element layer 300 (better is also to consider thickness), adjusted described required time Th, Te.At this, the charge transport material that light emitting element layer 300 is adopted (hole transporting material, electron transport materials) generally speaking has 10
-3To 10
-6The charge mobility (hole mobility, electron mobility) of scope, usually, this mobility is the value that is obtained when certain high concentration.In addition, if the concentration increase then mobility also increase.Therefore, can make the concentration that contains of the charge transport material that each layer adopt reach optimization, and adjust the thickness of each layer, can realize described characteristic thus.
Charge mobility, thickness and the concentration of each layer below are described.
At first, the hole mobility of the aromatic amine derivative compound that is adopted in the main material of the material of hole transporting layer 320 and the 1st luminescent layer 330 is 10
-3Cm
2/ Vs to 10
-4Cm
2/ Vs when concentration (about 100 quality %).
The electron mobility of the metal-organic complex that is adopted in the main material of the material of electron supplying layer 350 and the 2nd luminescent layer 340 is 10
-4Cm
2/ Vs to 10
-6Cm
2/ Vs when concentration (about 100 quality %).Adopting polycyclc aromatic compound to be used as under the situation of main material of electron transport of this 2nd luminescent layer 340, this compound possesses electronics and both conveyings of hole, and electron mobility is 10
-3Cm
2/ Vs to 10
-5Cm
2/ Vs, hole mobility also is 10
-3Cm
2/ Vs to 10
-5Cm
2/ Vs.
Can record described hole mobility and electron mobility by time-of-flight method (TOF:Time of Flight).Particularly, this TOF method is to make the material membrane of mensuration (in this form of implementation, organic compound material film for each layer) between the electrode of subtend each other, come lamination and double team with the concentration of about 100 quality %, by optical excitation with the interface of the electrode on one side of material membrane on produce electric charge carrier, and measure time of electrode that this electric charge carrier arrives the another side of institute's subtend, try to achieve mobility thus.
As implied above, when coming film forming with the concentration of about 100 quality %, have cavity conveying and the hole mobility of known organic compound 10
-3Cm
2/ Vs to 10
-5Cm
2The scope of/Vs, and when coming film forming with the concentration of about 100 quality %, have electron transport and the electron mobility of known organic compound 10
-3Cm
2/ Vs to 10
-6Cm
2The scope of/Vs.
The thickness of each layer then is described, hole injection layer 310 is 0.5nm to 5.0nm (under the situation of CFx) or 10nm to 20nm (under the situation of CuPc).Hole transporting layer 320 is 30nm to 300nm, and the 1st luminescent layer 330 is 10nm to 150nm, and the 2nd luminescent layer 340 is 20nm to 50nm, and electron supplying layer 350 is the thickness of 10nm to 30nm.
The relation of the charge mobility of light emitting element layer 300 and the thickness of each layer can be represented by following formula (1),
(Lhi/ μ hi)+(Lht/ μ ht)+(Lem1/ μ hem1)=α { (Lem2/ μ hem2)+(Let/ μ et) } ... formula (1)
In addition, α satisfies the relation of 0.5＜α＜2.5.In described formula (1), thickness with hole injection layer 310 is that Lhi, hole mobility are μ hi, thickness with hole transporting layer 320 is that Lht, hole mobility are μ ht, thickness with the 1st luminescent layer 330 is that Lem1, hole mobility are μ hem1, thickness with the 2nd luminescent layer 340 is that Lem2, electron mobility are μ hem2, is that Let, electron mobility are μ et with the thickness of electron supplying layer 350.In addition, though α is comparatively ideal is the relation that satisfies 1 ≦ α＜2, better is the scope that is positioned at 1.3＜α＜1.7, but, can obtain to make the 1st luminescent layer 330 and the 2nd luminescent layer 340 both luminous harmoniously and difficult long-life component constructions that produce broken string easily by making α greater than 0.5 and less than 2.5.
Next explanation makes the thickness of each layer for fixing and change 6 kinds of organic electroluminescent elements 500 of the concentration of charge-transporting compound.For the electroluminescence element 500 of the 1st embodiment (real 1), 1-1 comparative example (than 1-1) and 1-2 comparative example (than 1-2), only the cavity conveying material concentration of the 1st luminescent layer (EML1) and electron transport material concentration are different.For the electroluminescence element 500 of the 2nd embodiment (=real 1), 2-1 comparative example (than 2-1) and 2-2 comparative example (than 2-2), only the cavity conveying material concentration of the 2nd luminescent layer (EML2) and electron transport material concentration are different.
Again, electroluminescence element 500 is that employing CuPc is hole injection layer (HIL) 310 (thickness 10nm), and the thickness of hole transporting layer (HTL) 320 forms 100nm, and adopts a kind of NPB of aromatic amines compound.The thickness of the 1st luminescent layer (EML1) 330 forms and adds up to 30.9nm, main material adopts the NPB of cavity conveying, and dopant adopts DBzR, helps dopant to adopt DPN (5,12-diphenyl naphthacene) (DPN (5,12-diphenyl naphthonaphthalene)) (orange luminescent layer).The thickness of the 2nd luminescent layer (EML2) 340 forms 41.0nm, main material adopts polycyclc aromatic compound, particularly be the ADN (9 of anthracene series compound, 10-di (2-naphthyl) anthracene) (AND (9,10-two (2-naphthyl) anthracene)), dopant adopts perylene (Perylene) series compound, and interpolation NPB is used as cavity conveying compound (blue light-emitting layer).In addition, the thickness of electron supplying layer (ETL) 350 forms 10nm, and adopts Alq3 (tris (8-hydroxyquinolinato) aluminum (III): aluminium oxyquinoline complex compound).For the described DPN that helps dopant possesses the bipolarity of cavity conveying and electron transport, the concentration of therefore assessing this DPN is used as the electron transport compound concentration of the 1st luminescent layer.
Table 1
Described table 1 shows, concentration (weight %), thickness scaled value (nm) and the element luminous efficiency (cd/A) of each layer of each electroluminescence element of the 1st embodiment (real 1), 1-1 comparative example (than 1-1), 1-2 comparative example (than 1-2), the 2nd embodiment (real 2), 2-1 comparative example (than 2-1), 2-2 comparative example (than 2-2).
The concentration of the cavity conveying compound (NPB) of the HTL/EML1/EML2/ETL of the electroluminescence element 500 of the 1st embodiment is 100%/93.9%/7.3%/0%.
In contrast to this, the HTL of 1-1 comparative example and 1-2 comparative example and the NPB concentration of EML2 are all 100% and 7.3%, and the NPB concentration of EML1 then becomes lower by 87.4% and 77.7%.
In addition, the electron transport compound concentrations of the electroluminescence element 500 of the 1st embodiment is 0%/3.2%/90.2%/100% according to the order of HTL/EML1 (DPN concentration)/EML2 (ADN concentration)/ETL (Alq concentration).Than the element of this 1-1 comparative example and 1-2 comparative example, the electron transport compound concentrations of EHL and EML2 is identical, but the concentration of the electron transport compound (DPN) of the EML1 between being arranged at is 9.7% and 19.4% to become higher.The luminous efficiency of the 1st embodiment, 1-1 comparative example, 1-2 comparative example respectively is 14,12,10, and along with the minimizing (along with the increase of electron transport compound concentration) of the cavity conveying compound concentration of the 1st luminescent layer, luminous efficiency reduces.
At this, the material that can will demonstrate intrinsic mobility separately with 100% concentration for the 1st luminescent layer that contains multiple material and the 2nd luminescent layer is lamination in addition, and thickness in this case converts and try to achieve the α value of each electroluminescence element 500 of described each example, in the 1st embodiment, α=1, in the 1-2 comparative example, α=2.5.
Numerical value according to the conversion benchmark of thickness merges mark with concentration in described table 1, in the 1st embodiment, from hole transporting layer, be NPB (100nm)/NPB (2.9nm)+DPN (1.0nm)+DBzR (0.9nm)/AND (37.0nm)+NPB (3.0nm)+BD (1.0nm)/Alq (10nm) in regular turn.
Fig. 3 has shown the luminescent spectrum intensity of the electroluminescence element 500 (α=1) of this 1st embodiment, this figure demonstrates the 1st luminescent layer 330 and the 2nd luminescent layer 340, and both are harmonious good luminous, and obtain the white light of purpose, and luminous efficiency is the 14cd/A (electrical efficiency is 6.1lm/W) as described, therefore possesses excellent characteristic.
Fig. 4 shows, the NPB concentration in these 3 examples in the 1st luminescent layer is the luminescent spectrum intensity of the electroluminescence element 500 (α=2.5) of minimum 1-2 comparative example.Can learn that from Fig. 4 though the 1st luminescent layer 330 is luminous, the luminosity of the 2nd luminescent layer 340 is lower, 2 layers luminous harmonious relatively poor, and become near yellow white light.In addition, luminous efficiency is 10cd/A (electrical efficiency is 4.6lm/W), is the value also lower than the 1st embodiment.
From Fig. 4, can learn, in the element of 1-2 comparative example, in the 2nd luminescent layer, can't obtain luminous fully, phenomenon can estimate thus, when the cavity conveying concentration of material of the 1st luminescent layer is hanged down, cavity conveying quantity not sufficient from anode toward the 2nd luminescent layer 340, and be difficult for making the multilayer luminescent layer balancedly luminous.
Next, the HTL of the electroluminescence element 500 of 2-1 comparative example and 2-2 comparative example and the NPB concentration of EML1 respectively are 100% and 93.9%, though identical with the 2nd embodiment (the 1st embodiment), the NPB concentration of EML2 is 14.6% and 19.5%, go back high than 7.3% of the 1st embodiment.About luminous efficiency, 14cd/A than the 1st embodiment, in the electroluminescence element 500 of 2-1 comparative example and 2-2 comparative example,, and descend along with lower (NPB concentration is higher) of the concentration of the ADN of the electron transport compound in the 2nd luminescent layer (EML2) respectively for 11cd/A and 7cd/A (electrical efficiency is 3.2lm/W).
Fig. 5 has shown the luminescent spectrum of the electroluminescence element (α=0.5) of 2-2 comparative example, opposite with described 1-2 comparative example, though the 2nd luminescent layer 340 is luminous, the luminosity of the 1st luminescent layer 330 is lower, 2 layers luminous harmonious relatively poor, and become near blue white light.From this result, can infer, if possess electron transport compound concentration lower from the 2nd luminescent layer of the function of electron transport to the 1 luminescent layer of electron supplying layer, then electronics can't ample supply to the 1 luminescent layer, and can't be luminous fully in the 1st luminescent layer.
At this, be that the thickness of setting hole injection layer 310 is that 10nm, mobility [mu] hi are 10 in 1 the described organic electroluminescent element setting α value
-3Cm
2/ Vs, the thickness of hole transporting layer 320 are that 100nm, mobility [mu] ht are 10
-3Cm
2/ Vs, the thickness of the 1st luminescent layer 330 are that 30.9nm, mobility [mu] hem1 are 10
-3Cm
2/ Vs, the thickness of the 2nd luminescent layer 340 are that 41.0nm, mobility [mu] hem2 are 10
-3Cm
2/ Vs, the thickness of electron supplying layer 350 are that 10nm, mobility [mu] et are 10
-4Cm
2/ Vs.Certainly, thickness and mobility are not limited to these combinations, can be by producing described α value greater than 1 and make multilayer luminescent layer equilibrium and luminous efficiently less than 2.5 element.
In addition, can learn from described comparison that the concentration of hole transporting material that is positioned at 2nd luminescent layer also far away than the 1st luminescent layer (at this for blue light-emitting layer) from anode is higher, then luminous efficiency is lower, and luminous in addition harmony is variation also.Illustrate that from another viewpoint the concentration of hole transporting material that is arranged in 1st luminescent layer nearer apart from anode is lower,, and cause reduction and luminous balanced deterioration of efficient then toward the cavity conveying ability drop of the 2nd luminescent layer.
In addition, the concentration of electron transport materials that is positioned at 1st luminescent layer also far away than the 2nd luminescent layer (at this for the orange luminescent layer) from negative electrode is higher, and then luminous efficiency is lower, and luminous in addition harmony is variation also.Illustrate that from another viewpoint the concentration of electron transport materials that is arranged in 2nd luminescent layer nearer apart from negative electrode is lower,, and cause reduction and luminous balanced deterioration of efficient then toward the electron transport ability drop of the 1st luminescent layer.
Under tabulate and 2 show, in described the 1st embodiment, 1-1 comparative example, 1-2 comparative example, the relation between the difference of the concentration of the hole transporting material of the difference of the concentration of the hole transporting material of the 1st and the 2nd luminescent layer and hole transporting layer and the 1st luminescent layer.
Table 2
| Cem1-Cem2 | Chi-Cem1 | (Cem1-Cem2)/(Chi-Cem1) | Luminous efficiency (cd/A) | |
| The the 1st (2) embodiment | 86.6 | 6.1 | 14.2 | 14 |
| The 1-1 comparative example | 80.1 | 12.6 | 6.4 | 12 |
| The 1-2 comparative example | 70.4 | 22.3 | 3.2 | 10 |
As mentioned above, the concentration of hole transporting material is comparatively ideal to be to satisfy Cem1-Cem2〉Chi-Cem1, from the result of described the 1st embodiment, 1-1 comparative example, 1-2 comparative example, can learn, comparatively ideal is that (Cem1-Cem2) is also big more than (Chi-Cem1), it is desirable to more than 6 times, better is (to be 14.2 times in the 1st embodiment) about 14 times.
The organic electroluminescent element 500 of this form of implementation not only can be used in by additive color white light is penetrated to outside white escope and planar light source, also applicable to the display that arbitrary hue is penetrated by other additive color etc.
In addition, as shown in Figure 2, between white organic electroluminescent element 500 and substrate 10, for example can be and be used for making element formation face to reach between the smooth planarization insulating layer 180 at the interlayer insulating film 160 that makes transistor insulation, form any of colored filter CF of 3 looks of corresponding R, G, B, and from the emitted white light composition of organic electroluminescent element 500, only allow desired R, G, B light component penetrate, can realize full-color demonstration thus.In addition, can not form colored filter yet, and carry out the colour demonstration by 4 kinds of colors of R, G, B and W (white) in the pixel of a part.Colored filter is not limited to 3 looks of R, G, B, also can be provided with again Y (yellow) and M (fuchsin, Magenta) etc.
Claims (5)
1. an electroluminescence element possesses the light emitting element layer with multilayer luminescent layer between hole injecting electrode and electron injection electrode, wherein,
Described light emitting element layer possesses the organic layer that contains the cavity conveying compound more than 2 layers;
Described multilayer luminescent layer possesses: be disposed at the 1st luminescent layer near hole injecting electrode, and be disposed at the 2nd luminescent layer between described the 1st luminescent layer and the described electron injection electrode;
Between described the 1st luminescent layer and described hole injecting electrode, possesses hole transporting layer at least;
If the concentration that contains of the described cavity conveying compound of described hole transporting layer is Chi, the concentration that contains of the described cavity conveying compound of described the 1st luminescent layer is Cem1, during the containing concentration and be Cem2 of the described cavity conveying compound of described the 2nd luminescent layer, satisfy the relation of following formula:
Cem1-Cem2>Chi-Cem1。
2. electroluminescence element as claimed in claim 1, wherein, described cavity conveying compound is an amine derivatives compounds.
3. electroluminescence element as claimed in claim 1, wherein, in described multilayer luminescent layer, be disposed near the 1st luminescent layer of hole injecting electrode at least and be formed at the luminescent layer of the most approaching described the 1st luminescent layer, contain identical cavity conveying compound respectively.
4. electroluminescence element as claimed in claim 1, wherein,
Between described the 2nd luminescent layer and described electron injection electrode, possesses electron supplying layer at least;
The electron transport compound of described electron supplying layer, described the 2nd luminescent layer and described the 1st luminescent layer contain concentration, the described electron supplying layer of distance is far away, concentration is lower.
5. electroluminescence element as claimed in claim 1 wherein, in described multilayer luminescent layer, between described hole transporting layer and described hole injecting electrode, possesses hole injection layer at least;
In described multilayer luminescent layer,, possesses electron supplying layer at least being disposed between the 2nd luminescent layer and described electron injection electrode near electron injection electrode;
If the thickness of described hole injection layer is Lhi, hole mobility is μ hi, the thickness of described hole transporting layer is that Lht, hole mobility are μ ht, the thickness of described the 1st luminescent layer is that Lem1, hole mobility are μ hem1, the thickness of described the 2nd luminescent layer is that Lem2, electron mobility are μ hem2, the thickness of described electron supplying layer is Let, when electron mobility is μ et, satisfies the relation of following formula:
(Lhi/μhi)+(Lht/μht)+(Lem1/μhem1)＝α{(Lem2/μhem2)+(Let/μet)}；
Wherein, α satisfies the relation of 0.5＜α＜2.5.
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| JP2004289358A JP2006107790A (en) | 2004-09-30 | 2004-09-30 | Electroluminescent element |
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