EP2798683A1

EP2798683A1 - Back-emitting oled device and method for homogenizing the luminance of a back-emitting oled device

Info

Publication number: EP2798683A1
Application number: EP12820867.5A
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: WO2013098534A1; KR20140116167A; US9252386B2; US20150008412A1; CN104137290A; FR2985378B1; EA201491302A1; FR2985378A1; JP2015503821A

Abstract

The present invention relates to an OLED device (100), comprising: a transparent anode (1) having a specific sheet resistance R1, and a cathode (3) having a specific sheet resistance R2, the ratio r = R2/R1 being 0.01 to 2.5; at least one electrical anode contact and a first electrical cathode contact (5) having a specific so-called contact surface that is arranged above the active area (20); and a reflector (6) covering the active area (20) above an organic light-emitting system Et for each point B of the anode contact (41), point B being on a given edge of the first anode region (40), while defining a distance D between B and point C of the contact surface closest to said point B, and while defining a distance L between said point B and a point X of an edge of the first anode region opposite the first edge while passing through C, wherein the following criteria are defined: if 0.01 < r < 0.1, then 30% < D/L < 48%; if 0.1 < r < 0.5, then 10% < D/L < 45%; if 0.5 < r < 1, then 10% < D/L < 45%; if 1 < r < 1.5, then 5%< D/L < 35%; and if 1.5 < r < 2.5, then 5% < D/L < 30%.

Description

OLED DEVICE WITH REAR EMISSION,

The present invention relates to an organic electroluminescent diode device and a method for homogenizing the luminance of an OLED device that is emitted by the light emitting device. back.

The known organic electroluminescent systems or OLED (for "Organic Light Emitting Diodes" in English) 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 resistance per square 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 an organic light-emitting diode device, called OLED, comprising a transparent substrate with a first face main device comprising a stack comprising in this order starting from said first face:

- (directly on the first face or on a sub-layer for example) a lower electrode forming anode, which is transparent, preferably comprising at least one electroconductive layer, resistance anode per given square R1, in particular R1 being less than 30 Ohm / square or even lower than or equal to 15 Ohm / square or even 10 Ohm / square, the anode having a given anode surface, the characteristic dimension 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 0.01 to 2.5

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:

at least one anode electrical contact, in particular in a layer, said first adapted anode contact, the first adapted contact delimiting alone or with one or two anode contacts said to be adapted, in particular punctual, the (external) contour of a first region of the anode surface referred to as the first anode region, (a potential V being applied at the edge of the anode),

a first cathode electrical contact, in particular in a layer, which is:

arranged above the active zone, partially covering the region of the cathode above the first anode region,

a given surface, said contact area, smaller than the area of the active zone and the area of the first anode region,

- Shifted from the first suitable anode contact and possible second (s) second (s) adapted anode (s), at any point of the contact surface.

And for (at least a majority or even 80% and preferably) each point B of the first adapted anode contact and each second adapted anode contact, where the point B is in a given (first) edge of the first anodic region, defining a distance D between said point B and the point C of the nearest contact surface of said point B, and defining a distance L between said point B and a point X of an edge of the first anode region opposite to first edge, passing through C, we define the following criteria:

if 0.01 <r <0.1, then 30% <D / L <48%,

if 0.1 <r <0.5, then 10% <D / L <45%,

if 0.5 <r <1, then 10% <D / L <45%,

if 1 <r <1, 5, then 5% <D / L <35%,

if 1, 5 <r <2.5, then 5% <D / L <30%.

More strictly, D is the distance between B and the (orthogonal) projection of

C on the anode or better in the plane passing through B parallel to the anode, but given the low height of the OLED, this does not change the criteria defined above.

And even more rigorously, L the distance between B and X through the orthogonal projection of C in the plane passing through B parallel to the anode but taking into account the low height of the OLED, this does not change the criteria defined above.

It may therefore be preferable to define D and L in the plane passing through B parallel to the anode.

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

According to the invention, the term "adapted anode contact" (that is to say the first anode contact adapted as the second or second adapted 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 anode contact is to distribute the same electrical potential over its entire surface.

According to the invention, the first cathode electrical contact 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 largest possible OLED satisfying a criterion of luminance homogeneity prerequisite with an anode of R1 given and a given organic layer resistance rorg.

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.

The more one increases r (or r '), the more it is necessary to increase the contact area.

In particular for manufacturing difficulties, the ratio r is limited to 2.5.

The denomination opposite edges is taken broadly and incorporates two opposite zones of a rounded anodic region (disk, ovoid contour, etc.).

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

For better homogenization, the first cathode contact is present in the region or regions farthest from the edges of the first anode region (at potential V).

It is indeed in these remote areas that the anode potential drops most drastically. According to the invention, it is therefore necessary to compensate for a potential drop in the cathode, this potential drop being generated by the first cathode contact according to the invention.

For common anodic region shapes (polygons, round, etc.), this is naturally the central region - hence the center and its surroundings - of the first anodic region.

Thus, the first cathode contact may advantageously extend from the central region (ie the center) of the first anode region to the edges of the active area at least toward the adapted anode contact (s).

The upper limit of D / L recalls that the first cathode contact according to the invention deviates from a point type contact (or infinitely thin).

It is important that the first cathode contact has a surface of sufficient contact.

For example, a cathode contact leaving a part of the inhomogeneous central 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 first anode region,

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

Another counter example of cathode contact (not in accordance with the invention) would be a cathode contact external to the active zone.

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

The cathode contact according to the invention does not necessarily reproduce the symmetry of the active zone and / or the first anode region.

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 first anode region 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 (equipotential 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 contact surface may be a solid surface, a grid surface (arranged to maintain an equipotential), the surface being optionally starred.

In fact, a contact surface, even full, can be starred, with more or less thick branches (especially comparable to lines). Preferably, the ends of the branches are spaced from a point B1 nearest anode contact adapted a distance D1 with D1 / L1 obeying the same criteria on D / L The (substantially) solid contact surface (in particular a layer deposited on the anode) may have surface discontinuities, but incapable of disturbing its equipotential function in the region furthest from the adapted anode contact (s).

The solid surface may in particular be convex at least facing the adapted anode contact (s).

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. In the case of an active zone with at least one (strong) narrowing, it may be preferable not to have suitable anode contacts with respect to this narrowing.

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 cathode contact may extend to an area or edge areas of the active area that do not have anode contact matched.

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 first adapted contact, in particular substantially rectilinear, can be peripheral, peripheral taken in the broad sense therefore

on an anode edge protruding from the edge of the electroluminescent system (and from the edge of the cathode above), and therefore (at least partly) at the periphery external to the active zone, and in particular separated from the edges of the cathode and the organic layer by passivation,

and / or on an anode 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) at the inner periphery of the active area.

The first external peripheral adapted contact and / or the second or second optional external peripheral anode contacts are preferably at a distance W less than L / 10 or even L / 20 of the edge closest to the active zone.

Preferably the first adapted contact which is peripheral (such as the second optional peripheral anode contacts) runs along the periphery (internal or external) of the active zone, 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 of less than 10 mm, or even less than or equal to 5 mm from the nearest edge of the active zone and even (in part) at the edge of the the active zone (passing on both sides).

The second or anode peripheral contacts optionally peripheral peripheral (external and / or internal) are preferably at a distance (preferably constant) less than 10 mm or even 5 mm from the edge closest to the active zone and even be (in part) on the edge of the active zone (passing on both sides).

The first adapted contact may be on the anode edge.

Preferably, the shape of the first anode region (especially if only one region of the anode surface) corresponds (substantially) to the shape of the active zone or approaches it, for example formed of a set of rectilinear sections for a round outline .

The first and / or the second or second anode contacts adapted (including peripheral) may be substantially 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. Typically the reflector may have a light reflection RL (to the organic system) of at least 80%.

If the active zone is of the hollow type such as a frame or a ring, the first anode contact is on the outermost edge of the active zone, and it is preferred to place another suitable anode contact on the contour. more internal of the active zone. It is possible to define a distance D 'between a point B' of this other adapted anode contact and a point C closest to the cathode contact and a distance L 'between the point B' and the point B on the contour of a more external anode passing through C and in a manner similar to D and L and the ratios of DVL 'are defined as a function of r.

More rigorously, D 'is the distance between B' and the orthogonal projection of C in the plane passing through B 'parallel to the anode, but given the low height of the OLED, this does not change the criteria defined. above. And even more rigorously, L 'the distance between the point B' and B, passing through the orthogonal projection of C in the plane passing through B 'parallel to the anode but taking into account the low height of the OLED this does not change the criteria defined above.

It may therefore be preferable to define D 'and L' in the plane passing through B 'parallel to the anode.

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.

For even better homogenization, it is preferable:

- if O, 04≤r <0.1, then 40% <D / L <48%

- if 0.1 <r <0.5, then 30% <D / L <45%

- if 0.5 <r <1, then 20% <D / L <40% or even 25% <D / L <35%

if 1 <r <1, 5, then 10% <D / L <35%,

if 1, 5 <r <2.5, then 15% <D / L <25%.

Particularly preferred are the following criteria (in particular for a closed or quasi-closed contour of adapted anode contact (s) or a set of spaced extended anode contacts):

- 0.1 <r <0.5, then 30% <D / L <45%

- 0.5 <r <1, then 20% <D / L <40%, even 25% <D / L <35% - 1 <r <1, 5, then 10% <D / L <35%.

The first cathode contact may be preferably continuous in the first anode region, in particular is a solid layer (mono or multilayer), metal and / or preferably the contact surface is not hollow (at least in the center).

The anode can be contacted by a plurality of adapted anode contact groups defining the contours of a plurality of anode regions. In each anode region, the OLED device may comprise a cathode contact (adjacent to a possible hinge element or a Bragg mirror as detailed later) arranged above said anode region, of given surface area less than the area of the anodic region, partially covering the region of the cathode above said anode region and offset from the associated adapted anode contacts at any point C of the contact surface and meeting the criteria already described of D / L as a function of r.

Thus the adapted anode contacts can form a tiling of the anode (therefore of the active zone) with a mesh for example triangular, rectangular, square, honeycomb ...

The anodic regions are of identical or distinct sizes and of identical or distinct forms.

The OLED device may comprise one or more resistive electrical anode electrical contacts, in particular an electroconductive layer, arranged in the first anode region, connected to the first adapted anode contact and / or to the possible second (s) (s). ) suitable anode contact (s), resistive contacts possibly interconnected.

And the ratio r = R2 / R1 ranging from 0.01 to 2.5 is then replaced by a ratio r '= R2 / R'1 ranging from 0.01 to 2.5 in which R'1 is the equivalent square resistance. of the anode assembly and resistive contact (s) in the first anode region and the criteria for D / L are retained.

Of course we will prefer:

if 0.04 <r '<0.1, then 40% <D / L <48%

if 0.1 <r '<0.5, then 10% <D / L <45%

if 0.5 <r '<1, then 20% <D / L <40% or even 25% <D / L <35%

if 1 <r '<1, 5, then 10% <D / L <35%,

if 1, 5 <r '<2.5, then 15% <D / L <25%.

Resistive contacts are of such resistance that in operation, some points of the resistive contact are at a potential Vr distinct from the potential of the anode contact adapted 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 in 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 contact with screen-printed silver (enamel with silver) 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 μηη 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 ΓΙΤΟ 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 in the anode region, 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. It may be preferable to position the connection of the anode outside the active zone, that is why the connection (connected to the peripheral adapted anode contact) is placed in an anode contact zone protruding from the active zone.

It may be preferable to position the connectivity of the cathode outside the active zone, that is why the connection connected to the cathode contact is placed in a "cathode contact" zone protruding from the active zone.

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 anode contact adapted alone or with the second or anode contacts adapted to a closed or quasi-closed contour delimit all or part of the first anode region, which contour may be completed by one or more edges of the active zone (or edge). anode zone without anode contact more precisely).

And, in a first preferred embodiment, the first suitable anode contact extends and forms alone or with the second or second anode contacts adapted a closed or substantially closed contour including leaving at least one opening for example to achieve a cathode connector.

By almost closed contour is meant a contour covering at least 70%, or even

80% or even at least 90% of the contour of the first anode region.

For example, the length of a zone without suitable anode contact is, for example, of restricted size, in particular less than 5 cm, or even 1 cm (for example for an active zone dimension of at least 10 cm). It can also have several restricted openings.

Particularly preferred is a square, rectangular or round active zone with said quasi-closed contour and the ranges of D / L as a function of r or r 'above.

In particular, when the first adapted anode contact (internal and external) is peripheral to the active zone, one or more anode contactless zones (adapted or resistive) complete the outline of the first anode region. In this free zone of anode contact, the cathode can thus be fed:

by causing the cathode contact to overflow at one of its ends outside the active zone, this zone being no longer defined as a cathode contact zone but as a zone of cathode connection.

- or by overflowing the reflector on one side outside the active zone. Thus there may be for example:

a first and only strip forming the first contact adapted with an opening

a first band forming the first suitable contact and other strips (for example one per edge), strips separated by 1, 2, 3, 4 ... or even X openings for example at 1, 2, 3, 4 ... even X corners of the first anodic region with corners (from the triangle to the honeycomb for example).

With a closed or quasi-closed contour of adapted anode contact (s), the first cathode contact can be (substantially) centered with respect to the edges of the first anode region (or preferably with respect to the edges of the active zone if external anode contact (s)).

The first cathode contact has for example a contact surface whose contour is orthogonal to the current lines in the first anode region, especially in a square or rectangular configuration.

Preferably with a closed or quasi-closed contour of adapted anode contact (s), the first cathode contact, in particular centered, may have a (substantially) homothetic surface on the surface of the first anode region, or even of the active zone if external adapted contact (s).

At least the contour of the points of the contact surface closest to the first extended anode contact can follow the shape of the first extended anode contact or the shape of the contour of the active area.

The ratio r (or r ') can be adapted according to the geometry of the anode and cathode contacts or conversely, there is also an optimal contact surface (size and same geometry), for r or r' given.

Particularly preferred is a square or rectangular active zone or round with said quasi-closed contour, forming a homothetic surface and the ranges of D / L as a function of r or r 'above. Preferably with a closed or quasi-closed contour of adapted anode contact (s), the first anode region may be a square or a rectangle, the first cathode contact is in cross, centered, cross oriented along the diagonals from the first anode region (or the active zone) for example to ± 5 °, and the ratio r (or r ') is equal to 1.1 ± 0.1.

Naturally, one can deviate from a cross in the strict sense (four orthogonal rectangular sections) for example using a rosette with four branches.

With a closed or quasi-closed contour of suitable anode contact (s), there is also an optimal contact surface for a disk-shaped central contact on the cathode, as well as an optimal R2 (at R1 data).

For a too small contact area on the cathode, the current density in the cathode is very large near the contact (because all the current is concentrated towards the contact to exit the device to ground), so the voltage drop is very important in the cathode near the contact, which still leads to homogeneity.

For an intermediate contact surface, the voltage drop in the cathode compensates for the voltage drop in the anode, and the homogeneity is better than in the two extremal cases (small area or complete area, i.e. assimilated to an ideal cathode).

The optimum is independent of the size of the OLED and the strength of the organic layer.

Also, if the first adapted anode contact forms a closed or quasi-closed contour, the first anode region is in disc, the first cathode contact is centered and is preferably a disc, with 1 <r (or r ') < 1, 5 and 20% <D / L <30%.

In an outline configuration (quasi) closed in particular, the more one increases r (or r '), the more it is necessary to increase the contact area.

For polygons approaching a disk (for example from 6 or even 8 sides), this "disk" solution is particularly suitable.

In one embodiment of the invention with multiple adapted and spaced apart anode contacts, the first adapted anode contact may be an extended contact (band ..), and at least two of the second adapted anode contacts are of extended type and it is preferred that Lp <0.25P or <0.15P, with Lp the distance between each extended matched contact and P the perimeter of the first anode region.

Naturally, we can add punctual adapted anode contacts between extended anode contacts.

Preferably, the extended contacts are regularly distributed.

In one embodiment of the invention with multiple adapted and spaced anode contacts, the first adapted anode contact is a point type contact, the second point type adapted anode contacts are distributed to delimit the first one. anodic region, in particular, are present opposite each edge of the active zone, and in that the distance between each adapted point contact is less than half the maximum distance Lmax of the first anode region, or even Lmax / 4, or even Lmax 8.

It is indeed preferred that the point anode contacts are not spaced too far apart.

Preferably, the point contacts are regularly distributed.

Of course, suitable point anode contacts and extended anode contacts can be mixed.

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 semi-transparent cathode), the reflector may comprise a metallic reflecting covering element, in particular in layer (s) (thin), above the cathode away from the first main face, the covering element being separated from the cathode by an electrical insulating element, in particular a layer, said interlayers.

The first cathode contact, adjacent to the spacer (and at least partially surrounded by the spacer), may also be part of the reflector and is preferably in contact or electrically coupled to the reflective covering element.

The reflective covering element can be:

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

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

The reflective covering element, preferably layered, is for example 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

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

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

and / or optionally is diffusing for example by addition of diffusing particles, especially mineral particles, in a binder, in particular a 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 reflective covering element may be formed by a continuous layer on the interlayer (in layer) and the cathode, and preferably the cathode contact, or even the continuous layer, is based on the same material as the cathode, especially 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, resistivity (mass) of 900 nOhm.m, which can be transparent or semi-transparent depending on the selected thickness and the R2 of the barium, resistivity (mass) of 332 nOhm.m, which is transparent or semi-transparent depending on the chosen thickness.

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 with a thickness <3 nm.

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 semi-transparent 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 films of high refractive index n1, such as ΤΊ02, Zr02, 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 stack ΤΊ02 60 nm / Si02 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; R. Jordan, A. Dodabalapur, and R. E.

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, David K. Fork, Patrick De Visschere 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 also proposes a method for homogenizing the luminance of a rear-emission organic electroluminescent device with a transparent substrate with a first main face comprising a stack comprising in this order starting from said first face:

a lower electrode forming anode, which is transparent, preferably comprising at least one electroconductive layer, anode of resistance per given square R1, in particular R1 less than 30 Ohm / square, even less than or equal to 15 Ohm / square or even 10 Ohm /square,

an organic electroluminescent system above the anode,

an upper electrode forming a cathode, above the organic electroluminescent system, preferably comprising an electroconductive layer, cathode of resistance per given square R2 and preferably of constant given thickness,

the anode, the organic electroluminescent system and the cathode thus defining a common area, called active.

The process comprising

at least one anode electrical contact, said first adapted anode contact,

at least one first cathode electrical contact, called first cathode contact,

the method comprising adjusting the ratio r = R2 / R1 from 0.01 to 2.5 and positioning the cathode contact above the active zone, in particular the zone or zones furthest from the edges of the active zone and the choice of the size of the contact surface so as to obtain a luminance homogeneity H of the active zone greater than or equal to 5%, or even 10% to that of a different OLED device by the choice of a cathode of 100 nm aluminum (intrinsically forming the cathode contact over the entire surface of the active zone).

the addition of a reflector above the cathode, in particular by inserting said interlayer adjacent to the cathode contact, as already mentioned above. In addition, a ratio r (or r ') of 0.1 (or 0.5) to 2.5 or even 1.5 is preferred.

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

FIG. 1 is a schematic sectional view of an organic electroluminescent device according to the invention, FIG. 1a illustrates a schematic top view of the OLED device of FIG. 1, showing the anode and cathode contacts

FIG. 1b illustrates a schematic top view of the OLED device of FIG. 1 in a first variant,

FIG. 1c illustrates a schematic top view of the OLED device of FIG. 1 in a second variant,

FIGS. 1a and 1b are diagrammatic sectional views of an OLED device showing the connection of the cathode,

FIG. 1 is a diagrammatic sectional view of an OLED device according to the invention,

FIG. 1 'a illustrates a schematic view from above of the OLED device of FIG. 1', showing the anode and cathode contacts

FIG. 2 illustrates a schematic view from above of an OLED device with several anode regions and cathode contacts

FIG. 2a illustrates a schematic top view of the OLED device of FIG. 2, showing the anode and cathode contacts

- Figures 3 to 9 each illustrate a schematic top view of the OLED device, showing the anode and cathode contacts with active areas of different shapes

FIG. 4a shows graphs of homogeneity of the luminance obtained by the invention

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 1000 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, cathode of resistance per given square R2 of constant given thickness, the ratio r = R2 / R1 being between 0, 01 and 2.5, the stack thus defining a common, so-called active zone 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 of the peripheral anode 41 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 a continuous band, outside the active zone 20 delimiting only a quasi-closed, external contour of a first region of the anode surface referred to as the first anode region 40.

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.

Also, a first cathode electrical contact 5, for example in a layer, is arranged above the active zone 20 and above the central zone of the first anode region 40, with a given surface area known as the lower contact surface area. area of the anode region 40 (and active region 20). The contact surface therefore extends from the center of the first anode region to the edges of the active area.

The cathode contact 5 is offset from the first anode contact 41 and partially covers the region of the cathode 3 above the first anode region 40 at any point Ci of the contact surface.

For each point B of the first adapted anode contact and each second adapted anode contact, where the point B is in a given edge of the first anode region, defining a distance D between said point B and the point C the closer to said point B, and defining a distance L between said point B and a point X of an edge of the first anode region opposite the first edge, through C then:

• if 0.01 <r <0.1, then 30% <D / L <48%,

• if 0.1 <r <0.5, then 10% <D / L <45%,

• if 0.5 <r <1, then 10% <D / L <45%,

• if 1 <r <1, 5, then 5% <D / L <35%, • if 1, 5 <r <2.5, then 5% <D / L <30%.

or even better

• if 0.04 <r <0.1, then 40% <D / L <48%,

• if 0.1 <r <0.5, then 30% <D / L <45%,

· If 0.5 <r <1, then 20% <D / L <40%, or even 25% <D / L <35%,

• if 1 <r <1, 5, then 10% <D / L <35%,

• if 1, 5 <r <2.5, then 15% <D / L <25%.

More strictly, D is the distance between B and the orthogonal projection of C in the plane passing through B parallel to the anode. And L the distance between B and X, passing through the orthogonal projection of C in the plane passing through B parallel to the anode. It is therefore preferred to define D and L in the plane passing through B parallel to the anode.

In FIGS. 1a, 1b, 1c, 1a, 2a, 3, 4, 4, 5a, 6a to 6d, 7 to 9, points B1, B2, B3 and points C1 are illustrated by way of illustration. C2, C3, the points X1, X2, X3 and the associated distances L1, L2 or L3 and D1, D2 or D3. More precisely, the distances are defined in the plane passing through B1 or B2 or B3 parallel to the anode and the orthogonal projections of C1, C2, C3 in this plane passing through B1 or B2 or B3 are considered.

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

The OLED device 100 having above the organic electroluminescent system 2, away from the first face, a reflector 6 covering the active area.

More specifically, the reflector 6 comprises a metal 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 intermediate, 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.

In FIG. 1, the cathode contact 5 is based on the same material as the metallic covering element 61. The cathode contact 5 and the covering reflector 6 are 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, tab 7 has been structured before filing to leave an area free area corresponding to the area to be the area of the cathode contact. The edges of the active zone 20 are, for example, passivated by polyimide resin, for example 71.

The anode contact 41 is here on the anode 1 thus 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. This does not change the definition of the first anodic region 40.

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 contact of cathode is then preferably an aluminum-based layer, as already indicated.

The first anode region 40 (and thus the active zone 20) is for example at least 5 cm by 5 cm.

Figure 1a illustrates a schematic top view of the device 100 showing a portion of the device elements for clarity, namely the electrical function elements.

The first anode adapted contact 41 is a band delimiting the first anode region 40 which is square (or alternatively not shown several strips for example rectilinear delimiting a square).

The active zone 20 (defined here simply by its outlines, in dashed lines) is square, too, is internal to the first anode region 40. Practically the space between the first anode region 40 and the active zone 20 is restricted. The first external peripheral adapted contact is preferably at a distance W less than La / 10 or even La / 20 of the edge closest to the active zone 20 where La is the maximum dimension of the active zone for example.

The first anode contact is unique and delimits an almost closed contour, here covering 95% of the contour of the first anode region 40 (and of the active zone 20). An opening 4 'on the middle of the upper edge is used for the zone of cathode connection 52. The length of this zone without suitable anode contact is for example of restricted size especially less than 1 cm.

Alternatively not shown, the first cathode contact 5 can extend to the edge area of the active area (here at the center of the upper edge) which does not have suitable anode contacts 4, if the ratio D The prerequisites according to the invention are unchanged (in particular for the anode contact points at the ends).

The first cathode contact 5 (defined here simply by its outlines) is centered with respect to the edges of the first anode region 40, for example a square and edges of the active area 20.

We choose La = 15 cm, Rorg = 300 Ohm. cm ² , an anode of 3 Ohm / square, and the homogeneity H of the luminance H is shown in Table 2 below (the homogeneity H 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 the OLED) as a function of the square resistance of the cathode R2 and the edge of the square cathode contact and its distance D with the first contact adapted anode.

Table 2

Example A corresponds to an ideal cathode. We realize that he is it is preferable to finely adjust both the torque r and D / L to increase H. Thus even with an r around 1, we can degrade the homogeneity H especially if the contact surface is too weak (D / L too large) ), as indicated by counter examples 2 and 3. The best homogeneity is for r around 1, 1 and D = 0.25L (Example 2). Counter example 3 illustrates the lack of homogeneity for r greater than 3.5.

We choose a R1 preferably less than 5 ohm per square for better efficiency.

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 a cathode of R2 equal to 3 ohm per square approximately, aluminum is deposited by adjusting the thickness.

The results for H are similar (follow the same trend) with a different Rorg, typically between 50 and 300 Ohm. cm ² , an anode of R1 different typically between 1 and 10 ohm per square, and for any other size of active area.

In a first variant shown in FIG. 1b, illustrating a view from above of the OLED, the first cathode contact 5, always centered, is in cross, along the diagonals of the square of the first anode region 40.

The homogeneity results are the best for r equal to 1, 1.

The opening 4 'for the zone of cathode connection 52 is for example in a corner. There may be other unused openings at other corners for example.

In a second variant shown in FIG. 1c, illustrating a schematic top view of the OLED, electrically conductive anode contacts 42 are added in the first anode region 40 and connected to the first anode contact. adapted 41.

Here these resistive contacts 42 are interconnected and form a grid.

Also to obtain a good homogeneity of illumination, the ratio r ranging from 0.01 to 2.5 is replaced by a ratio r '= R2 / R'1 ranging from 0.01 to 2.5 in which R'1 is the equivalent square resistance of the anode assembly and anode contact (s) resistive (s) in the first anode region, that is to say the paralleling of the anode and resistive anode contacts.

The resistive anode contact may be of the same material as the adapted contact 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 will be 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.

It has already been observed that the contour of the first anode region 40 is almost closed and a zone of cathode connection 52 has been defined.

As shown in FIG. 1a, which is another diagrammatic sectional view of the OLED of FIG. 1, in fact the layer forming the reflector 6 is overflowed in a zone of the first face 10 without anode contact (FIG. area of the opening).

As shown in FIG. 1b, which is another diagrammatic sectional view of the OLED of FIG. 1 in a variant, in fact, the layer forming the reflector 6 is overflowed in an area of the first face 10 above anode contact 41 which is then isolated by passivation 71, passivation extending on the edge of the anode 1.

It is also possible to extend the end of the cathode contact 5 beyond the active zone 40 in the non-contact zone of suitable anode. FIG. 1 'shows an OLED device 200 in a variant of the first embodiment of the invention. invention and different in that the first adapted anode contact 41 is under the electroluminescent system 2. The first anode contact 41 is passivated by the resin 71. As shown in FIG. Va, one of the ends of the adapted anode contact 41 may protrude from the active zone for the anode connector 44.

FIG. 2 shows an OLED device 200 in a second embodiment of the invention and different from the first embodiment in that the first adapted anode contact 41 is not only peripheral. The first adapted contact 41 in fact defines two anode regions 20, for example rectangular and of equal area, comprising together the active zone, for example square (preferably anode region and active zone are of similar shape).

Also, the adapted first anode contact further comprises an adapted (passivated) internal strip 41 from a first (longitudinal) edge to a second opposite longitudinal edge here as shown in FIG. 2a which is a top view of the device 200.

For the homogeneity of the whole of the active zone 20, the second anode region is carried out as in the first anode region: addition of the second cathode contact and positioned according to the invention. The spacer and the covering element is modified accordingly. The choice of r and therefore the D / L is maintained in each anode region.

There is an opening 4 'by anode region 40 for the zone of cathode connector 52 for example in a corner or an edge.

Naturally a variant not shown is that the anode contact is at the inner periphery.

If resistive anode contacts are added, preferably one is placed in each anode region.

It is not necessary that all the anode regions have the same shape for which the position, the geometry and even r can vary from one region to another. This leads to the limit, a cathode of constant thickness per piece (by anode region).

In all cases, it is preferred to supply V with the edges of the whole of the active zone 20 (at the zones of openings 4 ').

In a variant with anode multi-regions shown in FIG. 3, the device 300 comprises an active zone 20 square, there are two anode regions triangular 40 formed by anode contacts 41 and paving the active zone 20 (a contact being along the diagonal of the active zone.

The first and second cathode contacts 5 are triangular (homothetic shape to the associated anode region)

Figure 4 shows an OLED device 400 in a fourth embodiment of the invention and different from the first mode in that the active area 20 is a disk, the first anode region 40 is a disk.

With rorg = 300 Ohm. cm ² , a diameter L1 of 15 cm from the active zone, R1 = 3 Ohm, Table 3 indicates the homogeneity H as a function of the size of the cathode contact Rc or D1 / L1 and as a function of R2.

Table 3

From this table is deduced the optimal range of parameters, that is to say r = 1 or r = 1, 25 with D1 / L1 = 25% ± 5%.

FIG. 4bis shows homogeneity graphs H as a function of D1 / L1 for the device 400 shown in FIG. 4, for different ratios r (between 0.1 and 2).

We see 6 curves F1 to F6 of homogeneity H (in%) respectively for r = 0.1; r = 0.3; r = 0.5; r = 1; r = 1.25; r = 2. These graphs recall the appropriate parameter ranges, in particular r = 1 or r = 1, D1 / L1 = 25% ± 5%.

For example, an anode is chosen for a silver stack of R1 at 3 Ohm / square and a cathode of R2 at 3.75 Ohm / square.

In a variant, for example, anode of ΓΙΤΟ from R1 to

8 Ohm / square and a cathode of R2 at 10 Ohm / square.

Alternatively shown in FIG. 4 ', the solid contact surface is replaced by a star-shaped surface with thick primary central sections and finer secondary beam sections.

FIG. 5 shows an OLED device 500 in a fifth embodiment of the invention and different from the first mode in that the first adapted anode contact 41 is a point-type contact (but could remain extended as an alternative, for example on only one edge), and eleven other adapted anode contacts 4i, of point type, are distributed to delimit the first anode region 40 especially present on each anode region edge.

The distance between each adapted point contact 4i is preferably less than half the maximum distance Lmax between two opposite edges, or even Lmax / 4 or Lmax / 8.

FIGS. 6a to 6d illustrate other examples of OLED 600 of anode regions and cathode contacts 5 of homothetic form or the like.

In the abovementioned examples, the active zone and the first anodic region are of the same shape (geometric for example):

- quadrilateral (figure a),

- hexagon (figure b),

- octagon (figure c),

pentagon (Figure d).

The cathode contact has the shape of the first anode region and approaches for example a circle for the octagon.

FIG. 7 illustrates a variant of FIG. 1a in which the solid contact surface is replaced by a star-shaped contact surface 5, in a beam, of preferably keeping a square outline.

FIG. 8 illustrates a schematic and partial plan view of a hexagonal active zone 20.

The first extended adapted anode contact 41, and two extended second adapted anode contacts 41 are along non-adjacent edges of the active zone 21, 22, 23

Preferably Lp <0.25P or <0.15P, with Lp the distance between each extended adapted contact and P the perimeter of the first anode region 40 defined by connecting these contacts. The cathode contact is here triangular up to the edges 21 ', 22', 23 'of the active zone without anode contacts.

FIG. 9 is a diagrammatic and partial plan view of an octagonal active zone 20.

The first extended adapted anode contact 41, and three extended second adapted anode contacts 41 are along non-adjacent edges of the active zone 21, 22, 23, 24.

The cathode contact is here starry up to the edges of the active zone without anode contacts 21 ', 22', 23 ',

Claims

An organic light-emitting diode device, called OLED (100 to 900), 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 anode (1), which is transparent, resistance anode 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) with a given square resistance R2, the ratio r = R2 / R1 ranging from 0.01 to 2.5,

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

the OLED device comprising:

at least one anode electrical contact, said first adapted anode contact (41), the first adapted anode contact (41) delimiting alone or with one or second adapted anode contacts (4i), the contour of a first region of the anode surface referred to as the first anode region (40),

a first cathode electrical contact (5), which is:

arranged above the active zone (20), partially covering the region of the cathode (3) above the first anode region,

- offset from the first adapted anode contact (41) and any second (s) second contact (s) of anode adapted (s), at any point of the contact surface, for each point B of the first adapted anode contact (41) and each optional second anode contact (4i), the point B being in a given edge of the first anode region (40), defining a distance D between said point B and the point C of the nearest contact surface of said point B, and defining a distance L between said point B and a point X of an edge of the first anode region opposite the first edge, via C the criteria are defined next :

if 0.01 <r <0.1, then 30% <D / L <48%,

if 0.1 <r <0.5, then 10% <D / L <45%, if 0.5 <r <1, then 10% <D / L <45%,

if 1 <r <1, 5, then 5% <D / L <35%,

if 1, 5 <r <2.5, then 5% <D / L <30%.

and the OLED device has above the organic electroluminescent system (2), away from the first face (10), a reflector (6) covering the active area (20).

OLED device (100 to 900) according to the preceding claim characterized in that the contact surface extends from the center of the first anode region (40) to the edges of the active zone (20).

OLED device (100 to 900) according to one of the preceding claims characterized in that the contact surface (5) is a solid surface, a grid surface, the surface being optionally starred.

OLED device (100 to 900) according to one of the preceding claims, characterized in that:

if 0.04 <r <0.1, then 40% <D / L <48%,

if 0.1 <r <0.5, then 30% <D / L <45%,

if 0.5 <r <1, then 20% <D / L <40%, or even 25% <D / L <35%,

if 1 <r <1, 5, then 10% <D / L <35%,

if 1, 5 <r <2.5, then 15% <D / L <25%.

OLED device (100 to 900) according to one of the preceding claims characterized in that it comprises one or more resistive electrical anode electrical contacts (42), in particular electroconductive layer, arranged in the first anode region (40) and connected to the first adapted anode contact (41) and / or to the optional second anode contact (s) (4i), resistive contacts (42) of greater resistance than the resistor adapted contacts, and in that the ratio r ranging from 0.01 to 2.5 is replaced by a ratio r '= R2 / R'1 ranging from 0.01 to 2.5 in which R'1 is the resistance by an equivalent square of the anode assembly (1) and resistive anode contact (s) (42) in the first anode region (40).

OLED device (100 to 900) according to one of the preceding claims, characterized in that the first adapted anode contact (41) extends and forms alone or with the second or second adapted anode contacts (4i) an outline closed or substantially closed and the first cathode contact (5) is preferably substantially centered with respect to the edges of the first anode region (40) or relative to the (x) adapted anode contact (s).

7. OLED device (100 to 400, 600) according to one of the preceding claims characterized in that the first cathode contact (5), in particular centered, has a homothetic surface on the surface of the first anode region (40), in particular if the first anodic region is round and / or homothetic on the surface of the active zone (40).

8. OLED device (100) according to one of claims 1 to 6 characterized in that the first anode region (40) is a square or a rectangle, the first cathode contact (5) is cross, centered, cross next the diagonals of the first anode region (40), and the ratio r or r 'is selected to be 1, 1 ± 0.1 or in that the first anode region (40) is in disk, the first cathode contact ( 5), centered, and is preferably a disk, with 1 <r or r '<1, 5 and 20% <D / L <30%.

9. OLED device (800, 900) according to one of claims 1 to 7 characterized in that the first suitable anode contact is an extended contact (41), and at least two of the second adapted anode contacts are of extended type (4i) and in that Lp <0.25P or <0.15P, with Lp the distance between each extended adapted contact and P the perimeter of the first anode region (40).

10. OLED device (500) according to one of claims 1 to 7 characterized in that the first adapted anode contact is a point type contact (41), the second adapted anode contacts, of point type, ( 4i) are distributed to delimit the first anode region (40), in particular are present opposite each edge of the active zone, and in that the distance between each adapted point contact (41) or (4i) is less than half of the maximum distance Lmax of the first anodic region, or even Lmax / 4 or even Lmax 8.

1 1. OLED device (100 to 900) 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), preferably metallic , in particular in a layer, above the cathode (3) away from the first main face, the covering element (61) being separated from the cathode by an insulating electrical element (7) said intermediate, and in that that the first cathode contact (5), adjacent to the spacer (7), is part of the reflector (6) and is preferably in contact or electrically coupled to the reflective cover element (61).

12. OLED device (100 to 900) according to claim 1 1 characterized in that the first cathode contact (5) is based on the same material as the reflective covering element (61), preferably based on aluminum, especially the first cathode contact (5) and the covering element (61) are formed by a continuous layer on the spacer (7) and the cathode (3), and preferably the continuous layer, is based on the same material as the cathode (3), in particular aluminum. OLED device (100 to 900) according to the preceding claim characterized in that the cathode (3) comprises an aluminum-based layer and the first cathode contact (5) comprises an aluminum-based layer.

OLED device (100 to 900) 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.

A method of homogenizing the luminance of a rear-emission organic electroluminescent device (100 to 900) with a transparent substrate with a first main surface (10) comprising a stack comprising in this order from said first surface:

a lower electrode forming anode (1), which is transparent, anode of 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 comprising an electroconductive layer, cathode of resistance per given square R2,

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

at least one anode electrical contact, said first adapted anode contact (41),

at least a first cathode electrical contact (5) with a given contact area less than the area of the active area,

the process comprising:

the adjustment of the ratio r = R2 / R1 ranging from 0.01 to 2.5 or even 0.1 to 1.5

positioning the cathode contact (5) above the active zone (20), in particular in the zone (s) furthest from the edges of the active zone, and the choice of the size of the contact surface so as to be to obtain luminance homogeneity H of the active zone (20) greater than or equal to 5%, that of a different OLED device by the choice of a 100 nm aluminum cathode,

the addition of a reflector (6) above the cathode (3).