EP2798685A1

EP2798685A1 - Backside-emitting oled device

Info

Publication number: EP2798685A1
Application number: EP12821292.5A
Authority: EP
Inventors: Vincent CHERY; Fabien Lienhart; Vincent Sauvinet
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2011-12-30
Filing date: 2012-12-28
Publication date: 2014-11-05
Also published as: US9112178B2; WO2013098536A1; US20150041782A1; FR2985380B1; KR20140116891A; FR2985380A1; JP2015503823A; CN104137291A

Abstract

The invention relates to an OLED device (100) comprising a transparent anode having a given sheet resistance R1, a cathode (3) having a given sheet resistance R2, the ratio r = R2/R1 varying between 0.1 and 5, a first suitable anode electrical contact, and a first cathode electrical contact (5a, 5d) which is offset in relation to the suitable anode electrical contact (41) at each point B1 of each suitable anode contact (41), defining a distance D1 between point B1 and the point C1 on the contact surface closest to point B1 and defining a distance L1 between point B1 and a point X1 on a second edge (22) of the active zone opposite the first edge (21) passing through C1, with the following criteria being defined: if 0.1 ≤ r < 1.75, then 20% < D1/L1; if 1.75 ≤ r < 2.5, then 20% < D1/L1< 90%; if 2.5 ≤ r < 3, then 20% < D1/L1< 80%; or if 3 ≤ r ≤ 5, then 20% < D1/L1< 70%, a reflector (6) covering the active zone (20).

Description

OLED DEVICE WITH REAR EMISSION

The present invention is directed to a rear-emitting organic light-emitting diode device.

The known organic electroluminescent systems or OLEDs (for

"Organic Light Emitting Diodes") comprise a stack of organic electroluminescent layers electrically powered by electrodes flanking it in the form of electroconductive thin layers. When a voltage is applied between the two electrodes, the electric current flows through the organic layer, thereby generating light by electroluminescence.

In an OLED device (bottom OLED), the upper electrode, or cathode, is a reflective metal layer typically with a square resistance of less than or equal to 0.1 Ω / square and the lower electrode or anode, is a transparent layer, deposited on a glass or plastic substrate allowing the emitted light to pass, of resistance by square of several orders of greater sizes.

WO99 / 02017 finds that a very large difference in square resistance between the anode and the cathode leads to both inhomogeneity of luminance, decreased duration and reliability, especially for large devices. sizes. Also, it proposes an organic electroluminescent diode device with a given transparent resistance anode by given square R1 and a cathode with a resistance given by square R2 given close, the ratio r = R2 / R1 being between 0.3 and 3.

For example, the anode is a layer of resistance ITO per square 10 ohms and the cathode is a thin layer of ytterbium resistance square 9.9 ohms is r around 1.

The gain in homogeneity, however, is not yet optimal and even is not certain for all OLED configurations.

Also, the subject of the present invention is firstly an organic light-emitting diode device, called OLED, comprising a transparent substrate with a first main face comprising a stack comprising in this order starting from said first face:

- (directly on the first face or on an under layer for example) a lower electrode forming anode, which is transparent, comprising preferably at least one electroconductive layer, anode of resistance per given square R1, in particular R1 less than 30 Ohm / square or even less than or equal to 15 Ohm / square or even 10 Ohm / square, the anode having a given anode surface, the dimension characteristic of the anodic surface being preferably at least 2 cm, or even 5 cm,

an organic electroluminescent system above the anode,

an upper electrode forming a cathode, above the organic electroluminescent system (or directly on the system), preferably comprising an electroconductive layer, cathode of resistance per given square R2, cathode preferably of constant thickness, with a ratio r = R2 / R1 ranging from 0, 1 to 5

the anode, the organic electroluminescent system and the cathode thus defining a so-called active common area (corresponding to the illuminating surface minus any internal anode contacts, if too opaque).

The OLED device further comprises:

along a first edge of the active zone, all along the first edge, for example, or along a group of adjacent edges (including the first edge), a suitable first anode electrical contact, or even a plurality of suitable anode electrical contacts, in particular at the inner and / or outer periphery of the active zone,

a first (preferably single) cathode electrical contact, which is offset from the appropriate anode electrical contact (s), given surface cathode contact, said contact surface.

For (the majority or even 80% or at best for) any point B1 of each adapted anode contact (including the first adapted anode electrical contact), defining a distance D1 between said point B1 and the point C1 of the surface contact point closest to said point B1, and defining a distance L1 between said point B1 and a point X1 of a second edge of the active zone opposite the first edge, via C1, then the following criteria are defined:

if 0.1≤r <1, 75 then 20% <D1 / L1,

if 1, 75 <r <2.5, then 20% <D1 / L1 <90%, or

if 2.5 <r <3, then 20% <D1 / L1 <80%,

- or if 3 <r <5, then 20% <D1 / L1 <70%. Finally, the OLED device comprises, above the organic electroluminescent system, away from the first face, a reflector covering the active area.

Such a device is adapted to be connected in series by the arrangement of the cathode and anode contacts in particular.

The invention also relates to an organic light-emitting diode device, called OLED, comprising a transparent substrate with a first main face having a number n greater than 1 of stacks, each stack comprising in this order starting from said first face:

- (directly on the first face or on a sub-layer for example) a lower anode electrode, which is transparent, preferably comprising at least one electroconductive layer, resistance anode per given square R1,

an organic electroluminescent system above the anode,

an upper electrode forming a cathode, above the organic electroluminescent system and preferably comprising an electroconductive layer, cathode of resistance per given square R2 preferably of constant given thickness, the ratio r = R2 / R1 ranging from 0.1 to 5; the anode, the organic electroluminescent system and the cathode thus defining a so-called active common zone,

the stacks being connected in series, or able to be connected in series (by the arrangement of the cathode or anode contacts in particular ...) and for at least one of the stacks, preferably for the majority or each of the n stacks, the OLED device comprising:

along a first edge of the active zone, a first electrical anode contact adapted or several adapted electrical anode contacts,

a first (preferably single) cathode electrical contact, which is offset from the appropriate anode electrical contact (s), given surface cathode contact, said contact surface,

For (the majority or even 80% or at best for) any point B1 of each adapted anode contact (including the first adapted anode electrical contact), defining a distance D1 between said point B1 and the point C1 of the surface contact point closest to said point B1, and by defining a distance L1 between said point B1 and a point X1 of a second edge of the active zone opposite the first edge, via C1, then the following criteria are defined: if 0.1 <r <1, 75 then 20% <D1 / L1,

if 1, 75 <r <2.5, then 20% <D1 / L1 <90%, or

- if 2.5 <r <3, then 20% <D1 / L1 <80%, or

if 3 <r <5, then 20% <D1 / L1 <70%.

Finally, the OLED device comprises, above the organic electroluminescent system, away from the first face, a reflector covering the active area.

Also for 0.1 <r <1, 75, if D1 is less than L1 (D1 / L1 <100%), the first cathode electrical contact is arranged above the active area and then partially covers the region of the cathode above the active area (extending to the second edge opposite the first edge). If D1 is greater than or equal to L1, the first cathode electrical contact is arranged along the second edge at the outer periphery of the active zone (for example in a cathode zone extending beyond the active zone).

For the other ranges of r, the first cathode electrical contact is then arranged above the active area and then partially covers the region of the cathode above the active area, (extending to the opposite second edge at the first edge).

More strictly, D1 is the distance between B1 and the projection (orthogonal) of C1 on the anode or better in the plane passing through B1 parallel to the anode, but given the low height of the OLED, this does not does not change the criteria defined above.

And even more strictly, L1 the distance between B1 and X1 (X1 in the plane passing through B1 parallel to the anode) through the orthogonal projection of C in the plane passing through B1 parallel to the anode but considering of the low height of the OLED, this does not change the criteria defined above.

It may therefore be preferable to define D1 and L1 in the plane passing through B1 parallel to the anode.

The transparent substrate may be monolithic (common for all or part of the stacks) or in several pieces (for example a support by stacking, n supports being abutted to form the substrate).

According to the invention, the term "adapted anode contact" (that is to say the first anode contact adapted as the other or the appropriate anode contacts), an electrical contact having sufficient conduction so that, when the OLED is in operation, the voltage is the same at any point of the adapted contact. As a result of this conduction property, between two points of the adapted contact, the luminance variation in the vicinity of these two points is less than 5%. The role of the adapted contact anode is therefore to distribute the same electrical potential over its entire surface.

According to the invention, the first cathode electrical contact further has sufficient conduction that, when the OLED is in operation, the voltage is the same at any point of the first cathode contact. As a result of this conduction property, between two points of this cathode contact, the luminance variation in the vicinity of these two points is less than 5%. The role of this cathode contact is to distribute the same electrical potential over its entire surface.

The object of this invention is to manufacture the highest possible OLED satisfying a prerequisite luminance homogeneity criterion with a given R1 anode and a given organic layer resistance rorg, in particular with a given configuration of contact contacts. anode on one edge or OLEDs in series.

The Applicant has found that the positions of the anode and cathode connectors, including their positioning relative to each other, and their shapes were critical. For a real gain in homogeneity, it is thus crucial:

to judiciously choose the anode contact (s), in particular their position and their resistance (so that they are adapted),

to correctly position the first cathode contact,

and to sufficiently move the first cathode contact away from the adapted anode contact (s).

This gives a potential difference as constant as possible between the cathode and the anode over the entire illuminating surface.

D1 can be constant regardless of the point B1 or vary while remaining with the ratio D1 / L1 according to the invention which depends drastically on the choice of ratio r.

The first cathode contact may extend into the active area toward the edges of the active area at least toward the adapted anode contact (s).

The possible upper limit of D1 / L1 recalls that the first cathode contact according to the invention then deviates from a point type contact.

A cathode contact leaving then a part of the central zone of the inhomogeneous active zone is not in accordance with the invention. Some examples include:

a cathode contact in several pieces that are spaced too far apart in the central zone of the active zone,

- A hollow cathode contact forming a frame or ring too thin.

Another counter example of cathode contact (not in accordance with the invention) would furthermore be a network of resistive or even adapted contacts, such as a grid or parallel strips, occupying only the inner periphery of the active zone (of width D1) or the whole of the active zone.

The first cathode contact according to the invention, especially above the active zone, preferably is not a point type contact.

The cathode contact according to the invention does not necessarily reproduce the symmetry of the active zone.

The contact surface may be a solid surface, a grid surface (arranged to maintain an equipotential). The contact surface may preferably be a single surface (in one piece) and / or the cathode contact may be unique.

The (substantially) solid contact surface (in particular a layer deposited on the anode) may have surface discontinuities, but incapable of disturbing its equipotential function.

And, as already indicated, preferably the full contact surface is not of the hollow type.

It is further preferred that the active zone is of the solid type.

The cathode contact may be self-supporting and attached to the cathode for example a set of son, sheet, etc.

Preferably the thickness of the first cathode contact is constant.

The first suitable contact can be a solid layer or mesh type (narrow grid forming a band ..), or a set of anode contacts point close enough to distribute the current, for example, less than a few mm .

The expression "along a first edge" is to be interpreted in a broad sense, the adapted anode contact (s) able to follow the contour of the first edge (internally or in the name "second edge opposite the first edge is taken in the broad sense and incorporates two opposite areas of a rounded active area (disk, ovoid contour, etc.).

The first contact adapted, in particular (substantially) rectilinear, may be peripheral, peripheral in the broad sense therefore:

- at the outer periphery at the first edge,

- Covered by the electroluminescent system (and by the cathode above) and is passivated by a passivation layer, such as polyimide, so (at least partly) the inner periphery of the first edge.

The first external peripheral adapted contact and / or the second or second suitable external anode contacts are preferably at a distance W less than L / 10 or L / 20 of the first edge where L is the distance between first and second edge, preferably constant.

Preferably, the first adapted contact which is peripheral (such as the second or second possible peripheral anode contacts) runs along (substantially) the periphery (internal or external) of the first edge, and is at a constant distance (or approximately) from the periphery of the active zone.

The first peripheral, external and / or internal adapted contact is preferably at a distance less than 10 mm, or even less than or equal to 5 mm from the first edge and even (in part) on the first edge of the active zone (in exceeding each other).

The first or the other peripheral anode contacts that may be peripheral peripheral (external and / or internal) are preferably at a distance (preferably constant) less than 10 mm or even 5 mm from the first edge, and even ( partly) on the first edge of the active zone (passing on both sides).

The first adapted contact may be on or under the anode.

The first and / or second or second anode contacts adapted (including peripheral) may (substantially) be rectilinear, be curved ....

Typically the width of a suitable anode contact (extended or even point) is of the order of cm. There is probably no outgoing light in the active area with the first suitable anode contact, because the latter is too opaque.

Moreover, contrary to the aforementioned prior art, an acceptable luminance level is preserved via the reflector according to the invention. Typically the reflector may have a light reflection R _L (towards the organic system) of at least 80%.

The organic electroluminescent system is above the anode:

- especially directly on the anode, by integrating in the anode function also a possible electroconductive planarization,

or directly on anode contact passivation adapted internal to the active zone (as discussed later),

or else directly on a resistive anode contact passivation internal to the active zone (as discussed later).

Typically, the substrate coated with the anode (anode directly on the substrate or separated by a layer for example for the extraction of light) can have a light transmission of at least 70%.

According to the invention, thin film is understood to mean a layer (mono or multilayer in the absence of precision) of thickness less than one micron, or even 500 nm or even 100 nm.

According to the invention, the term layer is a monolayer or multilayer, this in the absence of precision.

The cathode is preferably of constant thickness, especially with a tolerance depending on the manufacturing method, for example ± 10% for a thin-film type deposition.

OLED according to the invention particularly intended for lighting also the characteristic dimension, i. e. the largest dimension, such as the length or diameter, of the active zone may be at least 10 cm or even 15 cm.

The cathode being electrically powered to a potential Vc, such that the potential difference (s) between anode and cathode is suitable for lighting, in particular Vc is grounded.

It is considered that a conventional thick cathode is ideal, that is to say that it forms in itself a cathode contact (equi potential at any point of the cathode). The invention is distinguished from such a cathode by increasing the resistance per square of the cathode R2 and criteria on the contact surface.

The cathode contact is above the active area, especially if 1.75 <r or the cathode contact can be outside the active area if r <1.75.

Preferably, the first cathode contact which is above the active zone may have a (substantially) homothetic surface on the surface of the active zone and / or be at a distance (substantially) constant in contact with the adapted anode in particular. (substantially) parallel to the adapted anode contact.

If the active area is a square or a rectangle, the cathode contact is a square or a rectangle or if the active area is round, the first cathode contact has a rounded edge facing the first edge.

For even better homogenization, it is preferred:

if 0.1 <r <1, 75, then 40% <D1 / L1, or even 60% <D1 / L1,

if 1, 75 <r <2.5, then 40% <D1 / L1 <80%, even 50% <D1 / L1 <70%,

if 2.5 <r <3, then 40% <D1 / L1 <70%, or even 40% <D1 / L1 <60%,

- if 3 <r <5, then 30% <D1 / L1 <50%. The OLED device may comprise one or more resistive anode electrical contacts, in particular electroconductive layer, connected to the first adapted anode contact and / or to (x) any suitable anode contact (s) (s). )), potentially interconnected resistive contacts, resistance contacts larger than the resistance of the adapted anode contact (s).

And the ratio r = R2 / R1 ranging from 0.1 to 5 is then replaced by a ratio r '= R2 / R1' ranging from 0.1 to 5, in which R1 'is the equivalent square resistance of the anode assembly and resistive contact (s) in the active zone and the ratios D1 / L1 are kept.

Of course we will prefer:

if 0.1 <r '<1, 75, then 40% <D1 / L1, or even 60% <D1 / L1,

if 1, 75 <r '<2.5, then 40% <D1 / L1 <80%, even 50% <D1 / L1 <70%,

if 2.5 <r '<3, then 40% <D1 / L1 <70%, or even 40% <D1 / L1 <60%,

- if 3 <r '<5 then 30% <D1 / L1 <50%.

The resistive contacts are of such resistance that in operation, certain points of the resistive contact are at a potential Vr distinct from the potential of the adapted anode contact by more than 5% in absolute relation, or even at least 10% or even 20%.

The overall resistance of the anode can thus be defined as the paralleling of the resistance of the resistive contacts with the resistance of the transparent anode layer.

The resistive contact may be of the same material as the adapted contact, but much thinner for example less than 1 mm.

For aesthetic purposes, an OLED device without one or more anode contacts adapted in the active zone, or even without one or more resistive anode contacts (although generally fine in general), may be preferred. ) in the active area.

Anode contact (adapted or resistive) may be in the form of a layer of thicknesses between 0.2 and 10 μηη and preferably in the form of a monolayer in one of the following metals: Mo, Al, Cr, Nb or alloy such as MoCr, AINb or as a multilayer such as Mo / Al / Mo or Cr / Al / Cr.

It can also be a bus bar silver silkscreened (silver enamel) or deposited by inkjet.

It is already known to lower R1 of the anode by a fairly fine mesh of resistive electrical contacts, typically a square metal network or honeycomb. on the anode.

The strands are of the order of 50 to 100 μηι wide and the pitch of the network is generally 1/5 mm, which gives an occultation rate between 1 and 5%.

R1 'can vary from 0.5 to 5 ohms for example. In practice, a Mo or Cr (100 nm) / Al (500 nm to 1000 nm) / Mo or Cr (100 nm) multilayer is deposited for example over a ΙΊΤΟ of 140 nm. This multilayer is then etched chemically, with a photolithography process in general, to form the resistive contacts and possibly the anode contacts adapted to the same material but wider.

Thus, at the level of the anode, everything happens as if one had a resistance anode equivalent to the paralleling of the anode and the resistive anode contact (s).

We then have a voltage in the anode resistive contacts which will gradually decrease as we move away from the edges of the OLED.

In the same way, there may be one or more cathode resistive contacts, for example in an electroconductive layer, connected to the first cathode contact, possibly interconnected resistive contacts and in particular distributed over the entire area between the first cathode contact and the edges of the OLED.

In this case, R2 corresponds to the equivalent square resistance of the cathode assembly and resistive contact (s).

The resistive contacts are for example of resistance such that in operation, certain points of the resistive contact are at a potential Vr distinct from the potential of the first cathode contact V of more than 2% in absolute relation, or even at least 4% or even 8 %.

The first suitable anode contact may be an extended contact, in particular a single contact where the first adapted anode contact is a point type contact, and other suitable point type anode contacts are distributed on the first edge.

The first edge and the second edge are preferably the longitudinal (longer) edges of the active area. It is preferred that there be no suitable anode contacts on the edges adjacent to the first and second edges. It is preferred that the adapted anode contact (s) extend over (at least) a first edge a distance less than half of the active area.

For a square type active area or a rectangle, it is preferred that the one or more suitable anode contacts extend over a single, preferably the longest, edge. If the cathode contact is external, its shape matters less. Preferably it is close (or even in contact with the second edge) and runs along the second edge.

For a round active zone, the anode contact and the cathode contact are of the parenthesis type if the cathode contact is external. Or the anode contact is C and the internal cathode contact is C, particularly at a constant distance from the C of the anode contact.

One form of triangle-type active zone is avoided, the first and second edges being "too" adjacent. An active zone of symmetrical type is preferred.

The active area (s) may form strips, square or rectangular, (substantially) rectilinear, parallel or curved strips.

In the case of n stacks, the active areas are for example aligned in at least one given direction A said connection, or extend in another form such as a sun ...

The active zones of the n stacks, in particular solid, are preferably of similar sizes, in particular equal to a surface S ± 10% and preferably the active zones are of similar shapes. The distance between the first edge and the second edge is preferably (substantially) constant, for example, is worth G ± 10%.

The spacing between the active zones is preferably minimized to less than 500 μηη, in particular between 100 and 500 μηη.

Between the active areas, the reflector can be extended.

In the off state, we can arrange for the reflector to form a mirror on all n stacks (so without discontinuities).

The active areas are preferably geometric shapes, tessellations (rectangle, square, honeycomb ..).

Moreover, because of the adaptation of R2, the cathode may be transparent or semi-reflective, in particular RL reflection less than 80%, or even less than or equal to 60%, or even 50%.

The cathode allows the emitted light to pass, preferably without too much absorption. In a first configuration (with the transparent or semitransparent cathode), the reflector may comprise a preferably metallic reflective covering element, especially in layer (s) (thin), above the cathode while moving away. of the first main face, the covering element being separated from the cathode by an electrical insulating element, in particular a layer, said interlayer. The first cathode contact, adjacent to the spacer, may also be part of the reflector and is preferably in contact or electrically coupled to the reflective cover member.

The reflective covering element can be:

a layer, deposited by physical vapor deposition on the spacer, or on an inner face of a counter-element (glass, plastic film) attached to the spacer (preferably in optical contact),

a metal sheet: Cu, Inox, Alu, Ag ...

The reflective covering element, preferably layered, is based on at least one metal selected from Al, Ag, Cu, Mo, Cr.

The interlayer can be chosen to let the light emitted, preferably without too much absorb. For example, the interlayer is transparent, preferably of TL> 90%, and not particularly absorbent, in particular A <3%.

The interlayer can be:

a layer deposited on the thin-layer cathode deposited by physical vapor deposition, or even an adhesive if the reflector is a plate (stainless steel etc.) ...

air, the reflector being spaced apart by spacers, peripheral to the active zone,

an attached film, for example a lamination interlayer (PVB type) and the reflector is for example a glass substrate with a reflective layer. The interlayer preferably comprises or consists of a (mono) layer

(in particular of thickness less than 100 nm, thickness adjusted according to its absorption) which is

o mineral, preferably chosen from a nitride, an oxide, an oxynitride, for example a silicon nitride,

o or a resin for example identical to the passivation resin of the OLED edges, in particular polyimide,

o and / or optionally is diffusing, for example by addition of diffusing particles including mineral in a particular mineral binder. Preferably, in this first configuration, the first cathode contact comprises a layer based on the same material as the metal covering element, preferably which is an aluminum-based layer. The cathode contact can be:

a layer deposited on the cathode: conductive adhesive, layer deposited by inkjet or screen printing according to the desired shape, thin layer deposited by PVD and if necessary patterned, a solder or a solder ...

and / or a film attached with the predetermined shape: foil ...

The cathode contact, preferably layered, is based on at least one metal preferably selected from Al, Ag, Cu, Mo, Cr.

In particular, the cathode contact and the covering element may be formed by a continuous layer, in particular on the interlayer (in layer) and the cathode. Preferably the cathode contact, or even the continuous layer, is based on the same material as the cathode, in particular aluminum.

In this way in the off state, the continuous layer can form a mirror and there is no differentiation by the cathode contact of the covering element.

It may be desired to use a single deposition technique (for example physical vapor phase PVD, especially cathode sputtering or evaporation) for the covering element and the cathode contact (and even the cathode or the interlayer), or even only one layer deposition step for the covering element and the cathode contact.

More widely, among the possible materials for the cathode, mention may be made of

metals: aluminum, beryllium, magnesium, calcium, strontium, barium, lanthanum hafnium, indium, bismuth,

and lanthanides: cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

Particularly preferred are aluminum, silver, barium, calcium, samarium which are often used for their poor work output.

Table 1 below gives

the R2 of the aluminum (which can be transparent or semi-transparent depending on the chosen thickness),

the samarium R2, with a resistivity (mass) of 900 nOhm.m, which can be transparent or semi-transparent depending on the chosen thickness and the R2 of the barium, with a resistivity (mass) of 332 nOhm.m, which is transparent or semi-transparent depending on the chosen thickness. Thickness (nm) R2 (Ω / D) Thickness R2 (Ω / □) Thickness R2 (Ω / □) for Al (nm) for Ba (nm) for Sm

10 5 5 66 10 90

20 2.5 10 33 50 18

50 1 30 1 1 100 9

100 0.5 50 6 200 4.5

200 0.25 75 4

500 0.1 100 3

Table 1

It is preferred that R2 be greater than or equal to 1 or even 3 ohm / square and less than 20 ohm / square.

The cathode is preferably based on at least one metal, preferably selected from Al and Ag, optionally with a layer of LiF underlying the metal layer and for example less than 3 nm thick.

In particular, the cathode may comprise or even consist of an aluminum-based layer and the cathode contact is an aluminum-based layer, forming for example an excess thickness on the aluminum cathode layer.

In a second configuration (with the transparent or semitransparent cathode), the reflector is a Bragg mirror, a Bragg mirror arranged on the cathode and adjacent to the cathode contact, and the cathode contact is part of the reflector.

The Bragg mirror is known as a stack formed of an alternation of thin layers of high refractive index n1, such as TiO2, ZrO2, Al2O3, Si3N4, and thin layers of lower index n2, such as SiO2, CaF2.

For example, the delta of index n2-n1 is at least 0.3, and preferably at least 0.6, and the stack comprises at least two high index layers and two low index layers.

Thus, for an OLED with a wavelength centered around 570 nm, it is possible to envisage a multilayer multilayer TiO 2 60 nm / SiO 2 95 nm, or even possibly the superposition of this multilayer stack.

The use of Bragg mirrors for OLEDs is well known to those skilled in the art, which may possibly refer to the following publications: • Appl. Phys. Lett. 69, 1997 (1996); Efficiency enhancement of microcavity organic light emitting diodes; RH Jordan, A. Dodabalapur, and RE Slusher

• JOSA B, Vol. 17, Issue 1, pp. 1 14-1 19 (2000), Semitransparent or distributed gold Bragg reflector for wide-viewing-angle organic light-emitting-diode microcavities; Kristiaan Neyts, Patrick De Visschere, David K. Fork, and Greg B. Anderson.

The cathode contact may touch the Bragg mirror.

The cathode contact is connected for example by one of its ends protruding from the active area forming a zone of cathode connection.

The invention will now be described in more detail using non-limiting examples and figures

FIG. 1 is a diagrammatic sectional view of a first organic electroluminescent device according to the invention,

FIG. 1a illustrates a schematic top view of the OLED device of FIG. 1,

FIG. 1b shows graphs of homogeneity of the luminance obtained according to the invention

FIG. 1 is a diagrammatic sectional view of a second organic electroluminescent device according to the invention,

FIG. 1 'a illustrates a schematic view from above of the OLED device of FIG. 1',

FIG. 2 is a diagrammatic sectional view of a third organic electroluminescent device according to the invention,

FIG. 2a illustrates a partial schematic view from above of the device

OLED of Figure 2,

Figure 3 is a schematic sectional view of a fourth OLED device according to the invention with 4 stacks connected in series. It is specified that for the sake of clarity the various elements of objects (including angles) shown are not reproduced to scale.

FIG. 1, voluntarily very schematic, shows in section an organic electroluminescent device emitting through the substrate or "bottom emission" in English. The OLED device 100 (connectable in series easily) comprises a transparent substrate with a first main face 10 comprising a stack comprising in this order starting from said first face:

a lower electrode forming anode 1, which is transparent, comprising at least one electroconductive layer, resistance anode per given square R1, for example a TCO or a silver stack,

an organic electroluminescent system 2 above the anode (including HTL and ETL layer),

an upper cathode electrode 3, transparent or semi-reflective, above the organic electroluminescent system, comprising an electroconductive layer, given resistance cathode R2 of given constant thickness, the ratio r = R2 / R1 ranging from 0 , 1 to 5, the stack thus defining a common area, called active 20.

A potential V, for example 4 V or 10 V, is applied at the edge of the anode 1 via a first electrical contact 41 of the peripheral anode, in (multi) metal layers for example. It is said first adapted anode contact 41, that is to say electrical resistance adapted to be, in operation, the first potential V at any point.

The first adapted contact 41 is here outside the active zone 20 on a first longitudinal edge 21 of the active zone.

The invention thus consists of an OLED module whose ratio r and the geometry of the electrical connections on the two electrodes are adjusted so that the voltage drops which take place in the two electrodes compensate for maintaining a difference. as uniform as possible between the two electrodes.

For any point B1 of the first adapted anode contact 41, defining a distance D1 between said point B1 and the point C1 of the nearest contact surface of said point B, and defining a distance L1 between said point B1 and a point X1 of a second longitudinal edge 22 of the active zone opposite the first edge 21, via C1, then the following criteria are defined:

if 0.1 <r <1, 75, then 20% <D1 / L1,

if 1, 75 <r <2.5, then 20% <D1 / L1 <90%,

if 2.5 <r <3, then 20% <D1 / L1 <80%,

if 3 <r <5, then 20% <D1 / L1 <70%.

And better yet - if 0.1 <r <1, 75 then 40% <D1 / L1, even 60% <D1 / L1, or even 70% <D1 / L1

if 1, 75 <r <2.5, then 40% <D1 / L1 <80%, even 50% <D1 / L1 <70%,

if 2.5 <r <3, then 40% <D1 / L1 <70%, or even 40% <D1 / L1 <60%,

- if 3 <r <5 then 30% <D1 / L1 <50%

The contact surface 5 is here a solid surface, alternatively it is grid.

A reflector 6 comprises a metallic reflecting covering element 61, above the cathode 3 away from the first main face, the covering element 61 being separated from the cathode 3 by an electrically insulating electrical element 7 said interlayer, transparent and little absorbent, here a layer of preferably mineral and thin, such as 50 nm of silicon nitride.

The first cathode contact 5, adjacent to the spacer 7, is reflective, therefore part of the reflector 6 and is preferably in contact even electrically coupled to the reflective covering element 61.

The cathode contact 5 is preferably based on the same material as the metal covering element 61. The cathode contact 5 and the covering reflector 6 are then formed by a continuous layer on the insert 7 and the cathode 3 for example by physical vapor deposition. Preferably, this continuous layer is based on aluminum, for example 100 nm or even 500 nm thick. Naturally, the interlayer 7 has been structured before the deposition to leave a free zone corresponding to the zone intended to be the zone of the cathode contact.

The second edge 22 of the active zone 20 is, for example, passivated by polyimide resin, for example 71.

The anode contact 41 is here on the anode 1 previously deposited on the substrate (or on an underlying layer). However, the anode 2 can just as easily be deposited after the anode contact 41 and cover it partially for its electrical connection.

In a variant not shown, the reflector comprises a Bragg mirror adjacent to said first cathode contact. The reflective cathode contact is then always part of the reflector. The Bragg mirror (made of dielectric materials) can be directly on the cathode.

The cathode 3 is, for example, an aluminum layer, in particular of R2 greater than or equal to 1 ohm / square, or even greater than or equal to 3 ohm / square and less than 20 ohm / square or even 10 ohm / square, the cathode contact is then preferably an aluminum-based layer, as already indicated.

The active zone 20 is for example at least 5 cm by 5 cm.

The cathode contact extends outside the active zone beyond the second edge 22 and for example is deposited on a pre-existing contact pad 81.

The OLED device 100 comprises, above the organic electroluminescent system 2, away from the first face 10, a reflector 6 covering the active zone 20. FIG. 1 a illustrates a schematic view from above of the device 100 showing a part of the elements of the device for clarity, namely the electric function elements.

The first adapted anode contact 41 is a straight strip. The active zone 20 (here defined simply by its outlines, in dashed lines) is square too.

The edges 23, 24 of the active zone adjacent to the first and second edges

21, 22 are not provided with suitable anode contacts.

By way of illustration, a point B1 of the anode contact 41 has been drawn, the nearest point C1 belonging to the cathode contact 5 (here internal) and the point X1 of the second edge 22 (in the plane of B1 parallel to the 'anode). The straight line passing through B1, by the orthogonal projection of C1 in the plane of B1 parallel to the anode and passing through X1 makes it possible to define at best L1 and D1.

Virtually the space between the first adapted contact 21 and the first edge 21 is restricted. The first external peripheral adapted contact is preferably at a distance W less than L / 10 or even L / 20 of the first edge where L is the distance between first and second edges 21 and 22 here constant (equal to L1).

We choose L = 15 cm, Rorg = 1000 Ohm. cm ² , an anode of 3 Ohm / square, and the homogeneity H of the luminance is defined as the ratio between the minimum luminance on the maximum luminance for an OLED supplied at a given voltage above the ignition voltage of OLED.

FIG. 1b shows the homogeneity graphs H as a function of D1 / L1 of the cathode contact 5 of the device 100 shown in FIG. 1, for different ratios r (between 0.1 and 4). We see six curves F1 to F6 of homogeneity H (in%) respectively for r = 0.1; r = 0.5; r = 1; r = 2; r = 3; r = 4.

These graphs F1 to F6 recall the appropriate parameter ranges, especially towards the low r, the optimal range is narrower but H is better.

The results for H are similar (follow the same trend) with a

Rorg different, typically between 50 and 1000 Ohm. cm ² , an anode of R1 different typically between 1 and 10 ohm per square, and for any other size of active area.

For example, r = 3 and D / L = 50% are chosen with an ITO anode of R1 = 8 Ohm per square and a cathode of R2 = 24 Ohm per square; or a silver anode of R1 = 3 Ohm per square and a cathode of R2 = 9 Ohm per square.

We can also choose a lower r, for ease of manufacture, for example with r = 1 and D / L = 70% => with an ITO anode of R1 = 8 Ohm per square and a cathode of R2 = 8 Ohm by square; or a silver anode of R1 = 3 Ohm - cathode of R2 = 3 Ohm per square.

To make an anode of R1 equal to 3 ohm per square, a silver stack is preferred over a transparent conductive oxide "TCO", such as ITO. For example, silver monolayer or silver bilayer stacks described in applications WO 2008/029060 and WO 2009/083693.

To make the cathode, aluminum is deposited by adjusting the thickness.

Figure 1 is a schematic sectional view of a second organic electroluminescent device 100 'according to the invention.

We chose a rather weak r, for example with r = 1 and 100% <D / L. In other words, the spacer 7 and the covering element 61 cover the entire active zone 20 and the cathode contact 5 'is offset at the periphery of the second edge 22 in a region of the cathode 3 projecting beyond the active zone 20.

The cathode contact 5 'may be in contact with the covering element 61, for example forming a continuous layer in the active zone and beyond. Fig. 1a illustrates a schematic top view of the device 100 'showing part of the device elements for clarity, namely the electrical function elements.

The first adapted anode contact 41 is a straight strip. The active zone 20 (here defined simply by its contours, in dashed lines) is rectangular. The edges 23 and 24 of the active zone adjacent the first and second edges 21, 22 are not provided with suitable anode contacts.

Virtually the space between the first adapted contact and the first edge 21 is restricted. The first external peripheral adapted contact is preferably at a distance W less than L / 10 or even L / 20 of the first edge where L is the distance between the first and second edges 21, 22.

As an illustration, a point B1 of the anode contact 41 has been drawn, the point C1 closest to the cathode contact 5 (here external) and the point X1 of the second edge 22 (in the plane of B1 parallel to the anode ). The straight line passing through B1, by the orthogonal projection of C1 in the plane of B1 parallel to the anode and passing through X1 makes it possible to define at best L1 and D1.

FIG. 2 is a diagrammatic sectional view of a second organic electroluminescent device 100 'according to the invention in a variant of the first device 100. FIG. 2a shows a partial schematic view from above of the OLED device of FIG. 2,

Resistive anode electrical contacts 42 are added in an electroconductive layer connected to the first adapted anode contact 41. Here these resistive contacts 42 are interconnected and form a grid on the anode (or alternatively below) and passivated by a resin 71.

Also to obtain a good homogeneity of illumination, the ratio r is replaced by a ratio r '= R2 / R'1 in which R'1 is the equivalent square resistance of the anode assembly and contact (s) of anode resistive (s), that is to say the paralleling of the anode and resistive anode contacts.

The resistive anode contact 42 may be of the same material as the adapted contact 41 but much thinner for example less than 1 mm. For example, a square mesh of metal strands with a period of 5 mm, made using aluminum wires of 500 nm height and 100 μηη of width forms a system having an equivalent square resistance of 2, 7 ohm per square. If such a mesh is placed on a resistance ITO anode per square of 20 ohm per square, the equivalent resistance of the anode (defined as the resistance resulting from the paralleling of the anode and the resistive contacts) is then 2.4 ohm per square. By producing on this anode a square active area OLED of 8x8 cm ² , having a vertical resistance of organic materials of 100 ohm.cm ² , the illumination will be close to a resistive contact located at 4 cm from the edge of the 'OLED 20% lower. This reduction in illumination greater than 5% is attributed to the resistive nature of the resistive contacts which cause a decrease in the voltage of the anode in the center of the OLED, causing the drop in illumination.

Another difference with respect to the first device is that the first anode contact 41 runs along the first edge 21 in the active zone 20 and not outside. Also, it is passivated by a resin 71. It protrudes from the edge 24 (adjacent to the first edge 21) for its electrical connection.

Figure 3 is a schematic sectional view of a third organic electroluminescent device 1000 according to the invention.

In fact, the OLED device comprises four OLED devices 100a to 100b of the type of the first device 100, thus four stacks defining four active zones 20a to 20d and connected in series along a direction A.

Naturally, the cathode contact pad 81 is moved on the last edge of the last stack 20d. In addition, the first cathode contact 5a protrudes from the first active zone 20a and serves as the anode contact 41b of the second anode 2b and so on.

Here there is only one substrate 10, but it is also possible to use four supports with the OLED abutting together.

The preferably identical active areas are rectilinear strips or even curved strips of constant width.

It is preferred to minimize the non-reflective areas between each device 100a to 100d.

It is also possible to produce OLEDS in series with the device of the 100 'or 200 type. It is also possible to produce OLEDS in series with round active zones or the like.

Claims

Organic light-emitting diode device, called OLED (100 to 200, 1000), comprising a transparent substrate with a first main face (10) comprising a stack comprising in this order starting from said first face:

- a lower electrode forming an anode (1), which is transparent, anode resistance per given square R1,

- an organic electroluminescent system (2) above the anode,

- an upper electrode forming a cathode (3), above the organic electroluminescent system, cathode (3) of resistance per square given R2, the ratio r = R2/R1 ranging from 0.1 to 5,

the anode, the organic electroluminescent system and the cathode thus defining a common so-called active zone (20),

the OLED device comprising:

- along a first edge (21) of the active zone (20), a first adapted anode electrical contact (41), or even several adapted anode electrical contacts,

- a first cathode electrical contact (5', 5, 5a, 5d) which is offset from the adapted anode electrical contact (41), cathode contact (5) of a given surface, called contact surface,

for any point B1 of each suitable anode contact (41), by defining a distance D1 between said point B1 and the point C1 of the contact surface closest to said point B1, and by defining a distance L1 between said point B1 and a point X1 of a second edge (22) of the active zone opposite the first edge (21), passing through C1, then the following criteria are defined:

- if 0.1 < r < 1.75, then 20% < D1/L1,

- if 1.75 < r < 2.5, then 20% < D1/L1 < 90%,

- or if 2.5 < r < 3, then 20% < D1/L1 < 80%,

- or if 3 < r < 5 then 20%< D1/L1 < 70%,

and the OLED device (100) comprises above the organic electroluminescent system (2), moving away from the first face (10), a reflector (6) covering the active zone (20). Organic light-emitting diode device, called OLED (1000), comprising a transparent substrate with a first main face (10) comprising a number n greater than 1 of stacks (100a to 100d), each stack comprising in this order starting from said first side:

- a lower electrode forming anode (1), which is transparent, anode resistance per given square R1,

- an organic electroluminescent system (2) above the anode,

the anode (1), the organic electroluminescent system

(2) and the cathode

(3) thus defining a common so-called active zone (20a, 20d),

the stacks being connected in series, or able to be connected in series and for at least one of the stacks, preferably for the majority or even each of the n stacks, the OLED device comprises:

- along a first edge (21) of the active zone (20), a first adapted anode electrical contact or even several adapted anode electrical contacts (41, 41 a to 41 d),

- a first cathode electrical contact (5', 5a to 5d), which is offset from the adapted anode electrical contact(s) (41), cathode contact (5) of a given surface, called contact surface,

- for any point B1 of each suitable anode contact (41), by defining a distance D1 between said point B1 and the point C1 of the contact surface closest to said point B, and by defining a distance L1 between said point B1 and a point X1 of a second edge (22) of the active zone opposite the first edge (21), passing through C1, then the following criteria are defined:

- if 0.1 < r < 1.75, then 20% < D1/L1,

- if 1.75 < r < 2.5, then 20% < D1/L1 < 90%,

- if 2.5 < r < 3, then 20% < D1/L1 < 80%,

- if 3 < r < 5, then 20%< D1/L1 < 70%,

OLED device (100 to 1000) according to one of the preceding claims characterized in that the contact surface (5, 5', 5a to 5d) is a solid surface, a grid surface.

4. OLED device (100 to 1000) according to one of the preceding claims characterized in that the cathode contact (5) is above the active zone (20), in particular if 1.75 < r or the contact of cathode (5') is outside the active zone (20) in particular if r < 1.75.

5. OLED device (100 to 1000) according to one of the preceding claims characterized in that the cathode contact (5) is above the active zone (20) and has a surface substantially homothetic to the surface of the zone active (20) and in particular has a substantially constant distance from the suitable anode contact (41).

6. OLED device (100 to 1000) according to one of the preceding claims characterized in that the cathode contact (5) is above the active zone (20) and is of substantially constant distance to the adapted anode contact (41).

7. OLED device (100 to 1000) according to one of the preceding claims characterized in that:

- if 0.1 < r < 1.75, then 40% < D1/L1 or even 60% < D1/L1,

- if 1.75 < r < 2.5, then 40% < D1/L1 < 80%, or even 50% < D1/L1 < 70%,

- if 2.5 < r < 3, then 40% < D1/L1 < 70%, or even 40% < D1/L1 < 60%,

- if 3 < r < 5, then 30% < D1/L1 < 50%.

8. OLED device (100 to 1000) according to one of the preceding claims characterized in that so-called resistive anode electrical contacts (42), in particular in an electroconductive layer, contacts (42) of greater resistance than the resistance of the or suitable anode contacts (41), are connected to the suitable anode contact(s) (41), and in that the ratio r between 0.1 and 5 is replaced by a ratio r'= R2/R1' ranging from between 0.1 to 5 in which R1' is the equivalent square resistance of the anode assembly (1) and resistive anode contact(s) (42).

9. OLED device (100 to 1000) according to one of the preceding claims characterized in that the first edge (21) and the second edge (22) are longitudinal edges of the active zone (20).

10. OLED device (100 to 1000) according to one of claims 2 to 9 characterized in that the active zones of several of the n stacks, or even n stacks, are of similar sizes.

1 1. OLED device (100 to 1000) according to one of the preceding claims characterized in that the cathode (3) being transparent or semi-reflective, the reflector (6) comprises a reflective covering element (61), in particular metallic, above the cathode (3) moving away from the first main face, the reflective covering element (61) being separated from the cathode by a electrical insulating element (7) called interlayer, and in that the first cathode contact (5), adjacent to the interlayer (7), preferably forms part of the reflector (6) and is preferably in contact or even electrically coupled to the reflective covering element (61).

12. OLED device (100 to 1000) according to the preceding claim characterized in that the first cathode contact (5) is based on the same material as the reflective covering element (61), preferably based on aluminum, in particular the first cathode contact (5) and the reflective covering element (61) are formed by a continuous layer, and preferably the cathode contact (5) is based on the same material as the cathode (3).

13. OLED device (100 to 1000) according to the preceding claim characterized in that the continuous layer is based on the same material as the cathode (3), in particular aluminum.

14. OLED device (100 to 1000) according to one of the preceding claims characterized in that the cathode comprises an aluminum-based layer and the first cathode contact comprises an aluminum-based layer.

15. OLED device according to one of claims 1 to 10 characterized in that the reflector comprises a Bragg mirror, adjacent to the cathode contact, and the cathode contact is part of the reflector.