WO2015140090A1

WO2015140090A1 - Transparent substrate for photonic devices

Info

Publication number: WO2015140090A1
Application number: PCT/EP2015/055394
Authority: WO
Inventors: Philippe Roquiny; Benoit Domercq; Hidefumi Odaka
Original assignee: Agc Glass Europe; Asahi Glass Co Ltd
Priority date: 2014-03-17
Filing date: 2015-03-16
Publication date: 2015-09-24
Also published as: EP3120397A1

Abstract

The invention pertains to a transparent substrate (1) for photonic devices comprising a support (10) and an electrode (11), said electrode (11) comprising a stack of layers comprising, starting from the support (10), successively, a first dielectric layer (110), a metal conduction layer (111), a buffer layer (112) and a final dielectric nitride based layer (113). According to the invention, said buffer layer (112) is in direct contact with the metal conduction layer (111) and said final dielectric nitride based layer (113) is in direct contact with the buffer layer (112).

Description

Transparent Substrate for Photonic Devices

The present invention pertains to the technical field of photonic devices.

More specifically, the present invention relates to a transparent conductive substrate for photonic devices, to a process for the manufacture of said substrate and also to a photonic device incorporating such substrate. Photonic device is understood to mean any type of device that can emit or collect light. Such devices are optoelectronic devices, for example, such as organic light- emitting device (OLED) or light collectors such as organic photovoltaic cells, also referred to as solar cells. In particular, the invention relates to a transparent conductive substrate for an organic light-emitting device (OLED).

Organic light-emitting devices are generally manufactured with a good internal light efficiency. This efficiency is expressed in terms of internal quantum efficiency (IQE). Internal quantum efficiency represents the number of photons obtained by the injection of an electron. It lies in the order of 85%, even close to 100%), in known organic light-emitting devices. However, the quantity of light which effectively exits from these devices is clearly limited by the losses associated with interface reflection phenomena.

In general, an OLED comprises at least one organic light-emitting layer, a transparent conductor electrode generally made from indium-doped tin oxide (ITO) and a transparent support for supporting the electrode. The support is made, for example, of glass, ceramic glass or polymer film. The refractive indexes of the different constituents of the OLED lie in the range of 1.6-1.8 for the organic layers of the light-emitting device, 1.6 to 2 for the ITO layer, 1.4 to 1.6 for the supporting substrate and 1.0 for the outside air. The losses resulting from reflection (R) occurring at the interfaces cause the main reduction in external quantum efficiency (EQE). The external quantum efficiency is equal to the internal quantum efficiency minus the losses through reflection.

Indium-doped tin oxide (ITO) is the material most widely used to form transparent electrodes. However, its use unfortunately causes some problems. Indeed, indium resources are limited, which in the short term will lead to an inevitable increase in production costs for these devices. Moreover, because of the resistivity of ITO it is essential to use a thick layer to obtain a sufficiently conductive electrode. Since ITO is slightly absorbent, this causes problems of decreasing transparency. Moreover, thick ITO is generally more crystalline when conductivity is enhanced, and this increases the roughness of the surface, which must then be polished occasionally for use within organic light-emitting devices. ITO also requires substrate heating during its deposition in order to find a balance between properties such as transparency and electrical conductivity. Furthermore, indium present in organic light-emitting devices has a tendency to diffuse into the organic part of these devices resulting in a reduction in the service life of these devices.

In order to reduce or even suppress the quantity of ITO in an electrode for a photonic device, the use of Transparent Conductive Coatings (TCC) has been proposed. Document WO 2008/029060 A2 discloses a transparent substrate, in particular a transparent glass substrate, having a multilayer electrode with a complex lamination structure comprising a metal conductive layer and also having a base layer combining the properties of a barrier layer and an antireflective layer. This type of electrode enables layers with a low resistivity and a transparency at least equal to the electrode of ITO to be obtained, and these electrodes can be advantageously used in the field of large- surface light sources such as light panels. Moreover, these electrodes allow the quantity of indium used in their formation to be reduced and even dispensed with.

Document WO2010/094775 Al discloses also a transparent substrate having a multilayer electrode with a complex lamination structure comprising a metal conductive layer and also having a base layer combining the properties of a barrier layer and an antireflective layer, said structure being optimised to increase the amount of light emitted by an OLED limiting the losses associated with interface reflection phenomena. Such multi-layered electrodes are hereafter called TCC which is an acronym for Transparent Conductive Coating.

Nevertheless, the injection properties of said electrodes are strongly dependent on the nature and the thickness of the final layer present in the TCC structure. WO 2008/029060 A2 discloses examples of lamination structure having an ITO layer as final layer. The advantage of a final oxide layer, as for example ITO, is linked to the high work function value and the conductivity of said oxide. On the other hand, WO2010/094775 Al discloses the use of a thin nitride layer at the top of the TCC in order to standardise the surface electrical properties of the electrode in contact with the organic part of the photonic device. The main function of the thin layer is to allow a uniform transfer of charge to be obtained over the entire surface of the electrode. This uniform transfer is indicated by a balanced flux of emitted or converted light at every point of the surface. This layer must be thin due to the high light absorption of the suggested nitrides. Furthermore all the examples disclosed in the WO 2008/029060 A2 and WO2010/094775 Al comprise between the metal conduction layer, e. g. in Ag, and the OLED electroluminescent layers at least an oxide layer, said oxide layer being obtained by a cathodic sputtering technique using a magnetic field in an oxidizing atmosphere, in other words in an oxygen containing atmosphere, such atmosphere being critical for silver oxidation during the substrate production. The aims of the present invention are, firstly, to provide transparent conductive substrates for photonic devices having alternative and cheaper TCC structures, said TCC structure having a nitride-based final layer leading to the improvement of the device electrical performances, secondly, to provide an easier and more flexible process for the manufacture of such transparent substrates and thirdly to provide a photonic device that incorporates such transparent substrate.

The invention relates to a transparent substrate for photonic devices comprising a support and an electrode, said electrode comprising a stack of layers comprising, consisting or consisting essentially of, starting from the support, successively, a first dielectric layer, a metal conduction layer, a buffer layer and a final dielectric nitride based layer.

According to the invention, said buffer layer is in direct contact with the metal conduction layer and said final dielectric nitride based layer is in direct contact with the buffer layer. The term "final" in the expression "final dielectric nitride based layer" means that said dielectric nitride based layer is, starting from the support, the last layer of the electrode. The term "layer" means at least one layer . The expression "consisting essentially of means that a stack of layers may authorize the presence of additional layers provided that the essential features of said stack are not affected (e.g. that the required contacts between layers are fulfilled) or that a specific composition may authorize the presence of additional compounds provided that the essential features of said composition are not affected. The expression "buffer layer" is understood to mean a layer that can be fully or partially oxidised or nitrided. This layer helps avoid deterioration of the metal conduction layer, in particular as a result of oxidation or nitridation e.g. due to the next reactive deposition plasma. This buffer layer may also be called "blocking layer" or "barrier layer" in the art of TCC or low-E coating stacks. All the thicknesses given herein are geometrical thicknesses, unless otherwise specified. The inventors have surprisingly found that the use of a nitride- based layer as final layer, said layer being the only one between the buffer layer and the organic part of the photonic device, is an original alternative to current structures, since the properties of nitrides - in terms of conductivity, absorption, work function - were commonly known as not favorable for such applications. All the previous known structures were indeed formed with a final oxide layer, as in WO 2008/029060 A2 for example, or with an oxide covered by a thin nitride layer as in WO2010/094775 Al for example. In particular, the final dielectric nitride based layer according to the invention advantageously offers a good protection to the silver layer, the possibility of adjusting the work function and a good protection against acids usually used thereafter in the OLED manufacturing process.

The transparent substrate of the present invention comprises a transparent support. The support is considered transparent when it exhibits a light absorption of at most 50%, preferably at most 30% or at most 20%, more preferably at most 10%, at wavelengths in the visible light range. In a particular embodiment the transparent substrate according to the invention comprises a transparent support having a refractive index of at least 1.2, preferably at least 1.4, more preferably at least 1.5 or at least 1.6, at a wavelength of 550 nm. The advantage provided by using a support with a high refractive index is that it allows increasing the amount of transmitted or emitted light in the forward direction.

The term "support" is also understood to mean not only the support as such, but also any structure comprising the support as well as at least one layer of a material with a refractive index, n_materiai, close to the refractive index of the support, n_support, in other words |n_SUpp_0rt-n_materiai| < 0.1. |n_SUpp_0rt-n_materiai| represents the absolute value of the difference between the refractive indexes. A silicon oxide layer deposited on a soda-lime-silica glass support can be cited as example. This layer is used to protect the glass surface against ageing before deposition of other layers.

The function of the support is to support and/or protect the electrode. The support can be made of glass, rigid plastic material (e.g. organic glass, polycarbonate) or flexible polymer films (e.g. polyvinyl chloride (PVC), polyethylene terephthalate (PET), polypropylene (PP), polytetrafluoroethylene (PTFE)). The support is preferably rigid.

If the support is made of glass, e.g. a sheet of glass, it preferably has an average thickness of at least 50 μηι. Glasses may be mineral or organic. Mineral glasses are preferred. Of these, soda-lime-silica glasses that are clear or are bulk or surface coloured are preferred. More preferred, these are extra-clear soda-lime-silica glasses. The term extra-clear denotes a glass containing at most 0.020% by weight of total Fe expressed as Fe₂0₃ and preferably at most 0.015% by weight. Because of its low porosity, the glass has the advantage of assuring the best protection against any form of contamination of an OLED comprising the transparent substrate according to the invention.

According to a particular embodiment, the final dielectric nitride based layer has a thickness of at least 0.5 nm, preferably of at least 2.0 nm, more preferably of at least 4.0 nm, still more preferably of at least 6.0 nm; preferably, it has a thickness of at most 10.0 nm. Advantageously, the final dielectric layer has a thickness of at least 7.0 nm and at most 9.0 nm. Furthermore, the ultimate preferred thickness is about 8,0 nm as it usually offers the best balance between absorption increase and charge transfer for the targeted nitride compounds. This thickness also guarantees an entire coverage of the buffer layer to prevent conduction layer oxidation when substrates are exposed to ambient atmosphere.

Alternatively the thickness of the final dielectric nitride based layer may be defined by its ohmic thickness. The ohmic thickness of a layer is the ratio between the resistivity (p) of the material forming said layer and the geometrical thickness of said layer. Preferably, the ohmic thickness of the final dielectric nitride based layer is at most 10¹² Ohm, most preferably at most 10⁷ Ohm.

According to a particular embodiment, the final dielectric nitride based layer comprises, consists, or consists essentially of a nitride, XN_X, of at least one compound, X, selected from the group consisting of Be, Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Si, Ge and Sn, preferably selected from the group consisting of Ti, Zr, Nb, Hf, Ta, V, Nb, Cr, Mo, W, Ni, Fe, Al and Si. "XN_X" is understood to mean a nitride of at least one compound X where the atomic content of nitrogen in said nitride is at least 10%, preferably at least 20%; it does not represent a chemical formula of said nitride. The final dielectric nitride based layer may include oxygen, but then in a ratio O/N preferably less than 1, more preferably less than 0.5, still more preferably less than 0.2.

In a particular embodiment of the preceding one, the final dielectric based layer comprises, consists, or consists essentially of a mixture of a nitride of at least one compound selected from the group consisting of Al and Si and another compound selected from the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe, preferably Ti, Zr, Nb, Cr and Mo, more preferably consisting of Cr and Mo. Preferably, the final dielectric based layer comprises, consists, or consists essentially of a nitrided mixture of SiAlX, denoted "SiAlXN_x", X being selected from the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe, preferably being selected from the group consisting of Ti, Zr, Nb, Cr and Mo, more preferably being selected from the group consisting of Cr and Mo. "SiAlXN_x" is preferably a nitrided mixture of SiAlX wherein the atomic content of nitrogen is at least 10%>, preferably at least 20%>; it does not represent a chemical formula of said nitrided mixture. More preferably, the final dielectric based layer comprises, consists, or consists essentially of a mixture of Si_yAl_wXN_x (y and w being comprised between 0 and 1) X being selected from the group consisting of Mo and Cr. "Si_yAl_wXN_x" is understood to mean a nitride of at least Si and Al wherein the atomic content of nitrogen is preferably at least 10%, more preferably at least 20%, the atomic content of Si is preferably at least 20%, more preferably at least 30% and the atomic content of Al is preferably at least 0.25%, more preferably at least 0.5%. Preferably, the atomic content of Al in the final dielectric based layer is less than 10%, more preferably in the range from 0.5% to 10%. The inventors have surprisingly found that the use of a final dielectric nitride-based layer comprising SiXN_x, A1XN_X or Si_yAl_wXN_x (y and w comprised between 0 and 1) and X being a compound selected from the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe allows to optimize the surface electrical properties. In other words, the work function of the nitride based layer can be tuned from the work function of a SiN_x, A1N_X or Si_yAl_wN_x (y and w comprise between 0 and 1) final dielectric nitride based layer towards the work function of a XN_X wherein X is a compound selected form the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe, by tuning the amount of X from 0 to 100% relative quantity against Si_yAl_w with y and w comprised between 0 and 1, at least one of them being different of 0. Furthermore the inventors have also found that using a nitride based final layer for the electrode may offer the additional advantage of being more resistant to acid attacks coming from the further manufacturing steps of the photonic device, for example coming from metal etchants; this is particularly true for final layers containing SiN_x.

According to a particular embodiment, the final dielectric nitride based layer comprises, consists, or consists essentially of SiXN_x, A1XN_X or Si_yAl_wXN_x (with y and w comprised between 0 and 1), X being a compound selected from the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe, said compound X being present in the layer at a concentration of at least 2.5% in weight of X+Si+Al (without taking into account the nitrogen). Preferably, the final dielectric based layer comprises, consists, or consists essentially of SiyAl_wXN_x (with y and w comprised between 0 and 1), X being a compound selected from the group consisting of Mo and Cr, said compound X being present in the layer at a concentration of at least 2.5% in weight of X+Si+Al (without taking into account the nitrogen).

According to a particular embodiment, the final dielectric nitride based layer comprises at least, consists, or consists essentially of two sub-layers of different composition, a primary dielectric nitride based layer closer to the support and a top dielectric nitride based layer, furthest spaced from the support. Preferably, the top dielectric nitride based layer has a thickness of at least 0.5 nm, preferably at least 1.0 nm; it has a thickness at most 3,0 nm, preferably at most 2,0 nm. The primary dielectric nitride based layer has a thickness of at least 0.5 nm, preferably of at least 2.5 nm, more preferably of at least 4.5 nm; it has a thickness of at most 9.5 nm, preferably at most 8.5 nm, more preferably at most 7.5 nm. Advantageously, the top dielectric nitride based layer has a thickness of at least 1.0 nm and at most 2.0 nm and the primary dielectric nitride layer has a thickness of at least 5.0 nm and at most 8.0 nm. Advantageously, the primary dielectric nitride based layer has a thickness of about 6.5 nm and the top dielectric nitride based layer has a thickness of about 1.5 nm. Such values may offer the best balance between absorption increase and charge transfer for the targeted nitride compounds, the primary dielectric nitride based layer being the thicker layer having a low absorption and the thin top dielectric nitride based layer having a high absorption and a uniform charge transfer. According to a particular embodiment, the top dielectric nitride based layer comprises at least, consists, or consists essentially of a nitride of a compound selected from the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe. Preferably, the top dielectric nitride based layer comprises at least, consists, or consists essentially of a nitride of a compound selected from the group consisting of Cr and Zr. The main function of said top dielectric nitride based layer is to smooth the surface electrical properties located at the top of the electrode and to allow a uniform transfer of charge to be obtained over the entire surface of the electrode.

According to another particular embodiment, the final dielectric nitride based layer comprises, consists, or consists essentially of:

• a primary dielectric nitride based layer comprising at least, consisting, or consisting essentially of SiN_x, A1 _X or Si_yAl_wN_x

• a top dielectric nitride based layer comprising, consisting, or consisting essentially of at least a nitride of a compound selected from the group consisting of Mo, Cr, Ti, Ta, Zr, Hf, Nb, V, W, Ni and Fe, or preferably consisting of Cr and Zr.

According to a preferred embodiment, the buffer layer comprises, consists, or consists essentially of a compound selected from metals, nitrides, oxides, oxynitrides, substoichiometric oxides and substoichiometric nitrides and substoichiometric oxynitrides. Preferably, the buffer layer comprises, consists, or consists essentially of one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn and Al. More preferably, the buffer layer comprises, consists, or consists essentially of one element selected from the group consisting of Ti, Zr, Ni, Zn, Cr and Al. Still more preferably, the buffer layer comprises, consists, or consists essentially of Ti, TiO_x (where x < 2), NiCr, NiCrO_x, TiZrO_x (TiZrO_x indicates a titanium oxide layer with 20-80% by weight of zirconium oxide), ZnO_x, or ZnA10_x (ZnA10_x indicates a zinc oxide layer with 1 to 30% by weight of aluminium oxide). Advantageously the buffer layer comprises, consists, or consists essentially of TiO_x (where x < 2) or NiyCr_zO_x (where x < 1.1 and z/y > 17%), said compounds having a low absorption in the visible light. Alternatively, the buffer layer comprises, consists, or consists essentially of a substoichiometric oxynitride of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn and Al. Preferably, the buffer layer comprises at least, consists, or consists essentially of one element selected from the group consisting of Ti, Zr, Ni, Zn, Cr and Al. Still more preferably, the buffer layer comprises, consists, or consists essentially of either TiO_xN_y or NiCr_zO_xN_y and may present a graded nitrogen concentration, said concentration increasing from the metal conduction layer to the outermost surface of said buffer layer. According to a particular embodiment, the buffer layer has a thickness of at least 0.5 nm, preferably at least 1.0 nm, more preferably at least 2.0 nm; it has a thickness of at most 6.0 nm, preferably at most 5.0 nm, more preferably at most 4.0 nm. Advantageously, the buffer layer has a thickness of at least 2.0 nm and at most 4.0 nm. This thickness range allows to protect the conduction layer from damage due to the next nitride reactive deposition plasma, to limit intrinsic absorption present in the buffer layer and to ensure adhesion of the interface. If a ceramic target is used to form the buffer layer, said layer has a thickness of at least 1 nm, preferably at least 2.0 nm; it has a thickness of at most 15.0 nm, preferably at most 10.0 nm, more preferably at most 7.0 nm. Advantageously, if a ceramic target is used to form the buffer layer, the buffer layer has a thickness of at least 2.0 nm and at most 7.0 nm.

According to another particular embodiment, the buffer layer and the final dielectric nitride based layer form together a layer having a graded concentration of nitride compounds that increases starting from the metal conduction layer. Preferably, the graded concentration of nitride compound is such that the nitrogen concentration in the layer varies from less than 25 at.% near the metal conduction layer to above 75 at.%, furthest away from the metal conduction layer.

According to a preferred embodiment, the total thickness of the buffer layer and the final dielectric nitride based layer is at least 1.0 nm, preferably at least 5.0 nm, more preferably at least 8.0 nm; it is at most 15.0 nm, preferably at most 13.0 nm. Advantageously, the total thickness of the buffer layer and the final dielectric nitride based layer is at least 9.0 nm and at most 13.0 nm. The inventors have surprisingly found that such thicknesses simultaneously fit the properties of electrical conduction and light absorption.

The metal conduction layer mainly ensures the electrical conduction of the electrode. It preferably comprises at least one layer composed of a metal or a mixture of metals. The generic term "mixture of metals" denotes the combinations of at least two metals in the form of an alloy or doping of at least one metal by at least one other metal, wherein the metal and/or the mixture of metals comprises at least one element selected from Pd, Pt, Cu, Ag, Au, and Al. The metal and/or mixture of metals preferably comprises at least, consists, or consists essentially of one element selected from Cu, Ag, Au, and Al. More preferably, the metal conduction layer comprises at least, consists, or consists essentially of Ag in pure form or alloyed to another metal. The other metal is preferably selected from the group consisting of Au, Pd, Al, Cu, Zn, Cd, In, Si, Zr, Mo, Ni, Cr, Mg, Mn, Co, and Sn. More preferably, the other metal comprises at least, consists, or consists essentially of Pd and/or Au, preferably Pd.

Advantageously, the thickness of the metal conduction layer is at least 6.0 nm, preferably at least 8.0 nm, more preferably at least 10.0 nm; it is at most 29.0 nm, preferably at most 27.0 nm, more preferably at most 25.0 nm, still more preferably at most 22.0 nm. The thickness of the metal conduction layer is advantageously comprised within the range from 6.0 nm to 29.0 nm, preferably from 7.0 nm to 27.0 nm, more preferably from 8.0 nm to 25.0 nm. The inventors have found that the thickness of the metal conduction layer must be at least equal to 6.0 nm in order to obtain a good conductivity of the electrode, in other words a low electrical resistance.

The material forming the first dielectric layer comprises at least, consists, or consists essentially of one compound selected from the group consisting of:

• an oxide of at least one element selected from Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ni, Zn, Al, Ga, In, Si, Ge, Sn, Sb and Bi,

• a nitride of at least one element selected from boron, aluminium, silicon, and germanium,

• silicon oxynitride, aluminium oxynitride, mixed oxynitride of silicon- aluminium and silicon oxycarbide,

• substoichio metric oxides and doped oxides of at least one element selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Zn, Al, Ga, In, Si, Ge, Sn, Sb, and Bi, the doping agent preferably comprising at least one element selected from Al, Ga, In, Sn, P, Sb, and F,

• doped nitrides of at least one element selected from boron, aluminium, silicon, and germanium, the doping agent preferably comprising at least one element selected from Al, Ga, In, Sn, P, Sb, and F, • doped Si oxycarbides, the doping agent preferably comprising at least one element selected from Al, Ga, In, Sn, P, Sb, and F,

• doped silicon oxynitride, the doping agent comprising at least one element selected from B, Al, and Ga.

Preferably, the material forming the first dielectric layer comprises at least, consists, or consists essentially of one compound selected from the group consisting of:

• ITO, doped Sn oxide, wherein the doping agent is at least one element chosen from F and Sb, and doped Zn oxide, wherein the doping agent is at least one element chosen from Al, Ga, Sn, Ti.

• an yttrium oxide, a titanium oxide, a zirconium oxide, a hafnium oxide, a niobium oxide, a tantalum oxide, a zinc oxide, a tin oxide, an aluminium oxide, an aluminium nitride, a silicon nitride, a silicon-aluminium nitride and a silicon oxy carbide.

The thickness of the first dielectric layer is advantageously at least 3.0 nm, preferably at least 5.0 nm or at least 7.0 nm, more preferably at least 10.0 nm. For example, when the first dielectric layer is based on zinc oxide or on suboxidised zinc oxide, ZnO_x, wherein these zinc oxides are possibly doped or alloyed with tin or aluminium, a geometric thickness of the first dielectric layer of at least 3.0 nm allows obtaining a metal conduction layer, particularly of silver, that has a good electrical conductivity. The thickness of the first dielectric layer is advantageously at most 200.0 nm, preferably at most 170.0 nm, more preferably at most 130.0 nm, allowing quicker production process. The thickness of the first dielectric layer is advantageously comprised within the range from 5.0 nm to 200.0 nm, preferably from 7.0 nm to 170.0 nm, more preferably from 10.0 nm to 130.0 nm, still more preferably from 20.0 nm to 90.0 nm.

According to a particular embodiment, the first dielectric layer comprises a crystallisation sublayer, said crystallisation sublayer being the layer furthest removed from the support. The crystallisation sublayer may help enhance the crystallisation of the above metal conduction layer. It may also be called "nucleation layer" or "wetting layer" in the art of TCC or low-E coating stacks.

According to a particular embodiment of the preceding one, the thickness of the crystallisation sublayer is at least equal to 7% of the total thickness of the first dielectric layer.

According to a preferred embodiment, the material forming the crystallisation sublayer comprises at least, consists, or consists essentially of one compound selected from the group consisting of ZnO_x (where x < 1), Zn_xAl_yO_z and Zn_xSn_yO_z (where x + y > 3 and z < 6). Preferably, the material forming the crystallisation sublayer comprises, consists, or consists essentially of Zn_xAl_yO_z or Zn_xSn_yO_z having at most 95 wt% of Zn.

According to a particular embodiment, the first dielectric layer comprises a barrier sublayer, said barrier sublayer being the layer closest to the support. This layer in particular allows the electrode to be protected from any contamination by the migration of alkaline substances coming from the support, e.g. made of soda-lime-silica glass, or from the scattering layer (which is described hereinafter) and thus enables the service life of the electrode to be extended. The barrier sublayer preferably comprises at least, consists, or consists essentially of one compound selected from the group consisting of:

• titanium oxide, zirconium oxide, aluminium oxide, yttrium oxide,

• mixed oxides of zinc-tin, zinc-aluminium, zinc-titanium, zinc-indium, tin- indium,

• silicon nitride, silicon oxynitride, silicon oxycarbide, silicon oxycarbonitride, aluminium nitride, aluminium oxynitride, mixed nitride of aluminium- silicon, and mixed oxynitride of aluminium-silicon.

Furthermore, the barrier sublayer may be doped or alloyed with tin. According to a particular embodiment, the transparent substrate according to the invention has the following structure, starting from a clear or extra-clear glass support:

- a first dielectric layer:

· made of Ti0₂,

• comprising a crystallisation sublayer made at least of ZnO, Zn_xAl_yO_z or Zn_xSn_yO_z (where x + y > 3 and z < 6),

• having a thickness of at least 20.0 nm and at most 200.0 nm,

- a metal conduction layer made of Ag, having a thickness of at least 6.0 nm, preferably at least 8.0 nm, more preferably at least 10.0 nm and at most 22.0 nm, preferably at most 20.0 nm, more preferably at most 18.0 nm, and advantageously comprised within the range from 6.0 nm to 22.0 nm, preferably from 8.0 nm to 20.0 nm, more preferably from 10.0 nm to 18.0 nm,

- a buffer layer made of Ti or TiOx (x < 2) and having a thickness within the range 0.6 to 3.0 nm,

- a final dielectric nitride based layer selected from the following layers:

• a CrNx layer having a thickness of at least 1.0 nm and at most 2nm, i.e. a nitrided Cr wherein the atomic content of nitrogen is at least 10%, preferably at least 20%,

· a SiCrNx layer having a thickness of at least 1.0 nm and at most 15nm, ti.e. a nitrided mixture of Si and Cr wherein the atomic content of nitrogen is at least 10%>, preferably at least 20%>,

• a ZrNx layer having a thickness of at least 1.0 nm and at most 15nm, i.e. a nitrided Zr wherein the atomic content of nitrogen is at least 10%, preferably at least 20%,

• a SiMoNx layer having a thickness of at least 1.0 nm and at most 15nm, i.e. a nitrided mixture of Si and Mo wherein the atomic content of nitrogen is at least 10%>, preferably at least 20%>,

• a primary dielectric nitride based layer of Si x having a thickness of at least 1.0 nm and at most 3.0, i.e. a nitrided Si wherein the atomic content of nitrogen is at least 10%, preferably at least 20%, and a top dielectric nitride based layer of TiNx having a thickness of at least 0.5 nm and at most 4.5 nm, i.e. a nitrided Ti wherein the atomic content of nitrogen is at least 10%, preferably at least 20%.

According to a particular embodiment, the transparent substrate according to the invention comprises a scattering layer formed over the transparent support. Said scattering layer may for example comprise a glass which contains a base material having a first refractive index for at least one wavelength of light to be transmitted and a plurality of scattering materials dispersed in the base material and having a second refractive index different from that of the base material, such as the scattering layers described in WO2009017035 (Al), WO2009060916 (Al), WO2009/116531 (Al), WO2010/041611 (Al), WO2010084922 (Al), WO2010084923 (Al), WO2010/084924 (Al), WO2010084925 (Al), WO2011046190 (Al), WO2011126097 (Al), WO2011/046156, WO2012086396 (Al), WO2012014812 (Al). Preferably, said scattering layer has a thickness in the range 2 to 60 μιη, more preferably 5 to 40 μιη.

Advantageously, the scattering layer comprises a smoothing layer, said smoothing layer being, starting from the support, the outermost layer of said scattering layer. Preferably, the smoothing layer has a thickness of at least 200 nm. Preferably, the smoothing layer has a thickness of at most 400 nm. More preferably, the smoothing layer has a thickness of around 300 nm. Advantageously, said smoothing layer is made of a mixed oxide of silicon and titanium. The use of a smoothing layer helps reduce the occurrence of electrical short cuts. Advantageously, the support comprises at least one barrier layer on the face of the glass on which the scattering layer is deposited. This layer in particular allows the electrode to be protected from any contamination by the migration of alkaline substances coming from the support, e.g. made of soda-lime- silica glass, and thus enables the service life of the electrode to be extended. The barrier layer comprises at least, consists, or consists essentially of one compound selected from the following: silicon oxide, aluminium oxide, titanium oxide, mixed oxide of zinc-tin, mixed oxide of zinc-aluminium, silicon nitride, aluminium nitride, titanium nitride, silicon oxynitride, aluminium oxynitride. A second object of the invention is a process for the manufacture of a transparent substrate according to the invention, comprising, in the order:

• deposition on the support of the first dielectric layer,

• deposition of the crystallisation sub-layer of the first dielectric layer,

• deposition of the metal conduction layer,

· deposition of the buffer layer,

• deposition of the final dielectric nitride based layer.

Advantageously, said process steps are directly followed by deposition of the different functional elements adapted to build the photonic device, eventually with a full vacuum process from the deposition of the first dielectric layer of the electrode till the end of the deposition of the different functional elements adapted to build the photonic device.

The first dielectric layer, the metal conduction layer, the buffer layer and the final dielectric nitride based layer forming the electrode may be deposited by a method selected from the group of deposition techniques consisting of cathodic sputtering techniques, possibly using a magnetic field, deposition techniques using plasma, CVD (chemical vapour deposition), PVD (physical vapour deposition) techniques and PECVD (plasma-enhanced chemical vapour deposition). The compound of the final dielectric nitride base layer is preferably deposited by magnetron sputtering in a nitrogen containing atmosphere from a mixed target or by co-sputtering.

The deposition method is preferably conducted under vacuum. The term "under vacuum" denotes a pressure lower than or equal to 2.0 Pa. More preferably, the process under vacuum is a magnetron sputtering technique. One advantage of the final dielectric nitride based layer according to the present invention is that all the layers forming the final dielectric nitride based layer can be deposited in a similar nitrogen containing atmosphere when said layer is deposited by magnetron sputtering. Furthermore, the electric and the transparency properties of said final dielectric nitride based layer may be easily tuned by adapting the N₂ flow or by the addition of supplementary compounds through the use a doped target or an additional target as used in a co-sputtering process.

The process for the manufacture of the transparent substrate comprises continuous processes, in which every layer forming the electrode is deposited immediately after the layer underlying it in the multilayer stacking structure (e.g. deposition of the stacking structure forming the electrode according to the invention onto a support that is a moving ribbon or deposition of the stacking structure onto a support that is a panel). The manufacturing process also comprises discontinuous processes in which a time interval (e.g. in the form of storage) separates the deposition of one layer and the layer above it in the stacking structure forming the electrode.

According to a preferred embodiment, the method for the manufacture of a transparent substrate according to the invention also comprises, in order:

· deposition of the scattering layer on the transparent support,

• optionally, deposition of a smoothing layer on said scattering layer, before deposition of the first dielectric layer.

In a third object of the invention, the transparent conductive substrate according to the present invention is incorporated into an OLED that emits light.

The transparent substrate according to the invention will now be illustrated on the basis of the accompanying figures 1 and 2. Said figures show in a non-restrictive manner a substrate structure according to the invention. These figures are purely for illustration purposes and do not constitute a representation of a structure to scale. Moreover, performances of organic light-emitting devices containing transparent substrates according to the invention will also be shown in figures 3 to 16.

Figure 1 shows a cross-sectional view of a transparent substrate according to the invention, wherein the substrate comprises a transparent support and an electrode.

Figure 2 shows a cross-sectional view of a transparent substrate according to the invention, wherein the substrate comprises a transparent support, a scattering layer and an electrode. Figures 3 to 9 shows the variation of the current intensity versus the voltage applied for different OLEDs, the difference between all the OLEDs lying within their electrode structure (see Table 1 hereunder), wherein (a) is a comparative example and references (b) to (q) are OLEDs devices comprising substrates according to the invention. Fig. 10-16 show the evolution of the light absorption measured on the coating side from 400 nm to 800 nm for comparative example (a) and for various substrates (b) to (m) according to the invention.

Figure 17 shows the resistivity (Rho) for various nitrides monolayers deposited on 2mm soda-lime glass. Figure 18 shows the work function (WF - in eV) against slope (in arbitrary intensity unit/eV) recorded by ACl tool (made by Riken Keiki Co., Ltd Tokyo - Japan) on 150nm mono-layers of nitrides deposited on glass.

Figure 19 shows the work function (WF - in eV) against slope (in arbitrary intensity unit/eV) recorded by ACl tool (made by Riken Keiki Co., Ltd Tokyo - Japan) on 150nm ZrN_x mono-layers deposited on glass. Figure 20 schematically shows a cross-sectional view of a transparent substrate according to the invention, identifying the wording used herein with reference to individual layers and sublayers.

Figure 1 shows an example of a lamination structure forming a transparent substrate (1) according to the invention. The transparent substrate has the following structure, starting from the support (10):

• a first dielectric layer (110),

• the metal conduction layer (111),

• the buffer layer (112),

• the final dielectric nitride based coating (113),

these four layers forming the electrode (11).

Figure 2 shows an example of another lamination structure forming a transparent substrate (1) according to the invention. The transparent substrate has the following structure, starting from the support (10):

• a scattering layer (12) comprising a base material (121) having a first refractive index for at least one wavelength of light to be transmitted and a plurality of scattering materials (122) dispersed in the base material and having a second refractive index different from that of the base material

• a first dielectric layer (110),

• a metal conduction layer (111),

• the buffer layer (112),

• the final dielectric nitride based coating (113)

these last four layers forming the electrode (11).

Table 1 presents various electrode stacks wherein (a) and (a') correspond to known TCC references and are used as comparative examples, and (b), (c), (d), (e), (f), (g), (h), (i), 0^'), (k), (1), (m), (o), (p) and (q) correspond to examples according to the invention. In this table, the geometrical thickness of each layer is expressed in nanometer (nm) between [ ] brackets signs. Table 1 :

References Electrode structure

(a) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / ZS09 [7.0 nm] /

TiN_x [1.5 nm]

(a') Ti0₂ [75.0 nm] / ZS09 [9.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] /

ZS09 [6.3 nm] / TiN_x [1.5 nm]

(b) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / TiN_x [1.5 nm]

(c) Ti0₂ [75.0 nm] / ZS09 [9.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] /

CrN_x [1.5 nm]

(d) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiCrN_x [8.0 nm] with power ratio Si:Cr 0.25 : 1

(e) Ti0₂ [75.0 nm] / ZS09 [9.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] /

ZrN_x [1.5 nm]

(f) Ti0₂ [75.0 nm] / ZS09 [9.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] /

SiZrNx [8.0 nm] with power ratio Si:Zr 0.25:1

(g) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiMoN_x [8.0 nm] with power ratio Si:Mo 0.25:1

CO ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / Si _x [6.3 nm]

(i) Ti0₂ [75.0 nm] / ZS09 [9.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] /

Si _x [6.3 nm] / TiN_x [1.5 nm] ω Ti0₂ [75.0 nm] / ZS09 [9.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] /

Si _x [3.0 nm] / TiN_x [1.5 nm]

(k) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiCrN_x [4.0 nm] (1) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiCrN_x [12.0 nm]

(m) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / ZrN_x [8.0 nm] (gas flow 27/23 (Ar/N₂)

(m-) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / ZrN_x [8.0 nm] (gas flow 41/9 (Ar/N₂)

(m₊) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / ZrN_x [8.0 nm] (gas flow 18/32 (Ar/N₂)

(o) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiCrN_x [8.0 nm] with power ratio Si:Cr 0.1 : 1

(P) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiCrN_x [8.0 nm] with power ratio Si:Cr 0.33/1

(q) ZS09 [30.0 nm] / Ag [13.5 nm] / TiO_x [2.0 nm] / SiCrN_x [8.0 nm] with power ratio Si:Cr 0.50/1

For all the electrode examples and comparative examples, the layers were deposited onto 10x10cm² soda- lime clear glass (2mm thick) by magnetron sputtering running with DC power supplies MDX lkW (from Advance Energy Industries, Inc., Fort Collins, CO, USA). The various compounds have been sputtered under 0.4 Pa and 500W from a 10 cm diameter target except for co-sputtered species where 5cm diameter targets were used and Si power was maintained at 300W (1) or 600 W (2) while the second target was maintained at another specific power as stated. Ti0₂, titanium dioxide, was deposited from substoichio metric titanium oxide target with 5 seem 0₂ and 45 seem Ar. TiO_x, substoichiometric titanium dioxide, was deposited from substoichiometric titanium oxide target in pure Ar. The expression "ZS09" means a Zn_xSn_yO_z deposited under 10 seem 0₂ / 40 seem Ar gas from a ZnSn metallic target with 10 wt.% Sn content. Pure Ag (99.99%) was deposited in pure Ar atmosphere. For nitride compounds, the gas flow was 18 seem N₂ and 32 seem Ar except otherwise stated while. Pure (>99.5%) Si (doped with B), Ti, Cr, Mo, Ta, Al, Zr or Si_yZr_z targets were sputtered. It should be noted that Si_yZr_zN_x was obtained from a Si target containing 10 wt.% Zr. Si_yCr_zN_x and Si_yMo_zN_x were obtained by co-sputtering with a power ratio 0.25 Cr or Mo vs. 1 Si, in other words, 75W for Cr or Mo target and 300W for Si target.

Organic layers and aluminium counter-electrodes as described in "Methods Summary" of the S. Reineke et al. article, published in Nature, Vol. 459, p. 234-238, 2009, have then been deposited on said electrodes. All the curves appearing from fig. 3 to fig. 8 have been measured using the following method: one applies a fixed voltage to said OLED device, and then measures the resulting current. In a typical curve, there is a subthreshold region, a turn-on region and a saturated region. The transition between subthreshold and turn-on occurs at the turn-on voltage corresponding to light emission by the diode. To evaluate the device electrical performances, we observe the variation of the current after the turn-on voltage. It appears that the thickness of the final layer on top of the conduction layer is a key parameter so that low thicknesses are recommended for the nitride-based final coating in order to improve the device electrical performances. Fig. 3 clearly shows the advantage linked to the nature of the final layers in the electrode used in the substrate according to the invention (b) compared to the reference substrate (a), the charge injection threshold presenting a lower value. Another important value is also the current intensity measured at 4V. This value also shows clearly the advantage of the substrate according to the invention compared to the reference, said substrate presenting a current intensity which is, compared to the reference, higher by a factor 15,4.

Fig. 4 also shows a charge injection threshold of a lower value for the invention (c) compared to the reference substrate (a). Substrate (c) shows a current intensity which is, compared to the reference, higher by a factor 15,3. Fig. 5 shows that substrates according to the invention (e and f) may be used as alternatives to the reference substrate (a), the charge injection threshold of substrate (e) and (f) being in the same range as the reference. Furthermore, the current intensities measured at 4V are also in the same range as the reference, substrates (e and f) presenting respectively a current intensity which is, compared to the reference, higher by a factor 1,8 (e) and lower by a factor 0,3

(f).

Fig. 6 shows that the substrate according to the invention (g) may be used as alternative to the reference substrate (a), the charge injection threshold of substrate (g) being in the same range as the reference. Furthermore, the current intensity measured at 4V is also in the same range as the reference, substrate (g) presenting a current intensity which is, compared to the reference, lower only by a factor 0,8.

Fig. 7 shows that substrates according to the invention (h and i) may be used as alternatives to the reference substrate (a), the charge injection threshold of substrates (h) and (i) being in the same range as the reference. Furthermore, the current intensities measured at 4V are also in the same range as the reference, substrates (h and i) presenting respectively a current intensity which is lower by only a factor 0,4 (h) and 0,3 (i) than the reference.

Fig. 8 shows that substrates according to the invention (i and j) may be used as alternatives to the reference substrate (a), the charge injection threshold of substrates (h) and (i) being in the same range as the reference. Furthermore, the current intensities measured at 4V are also in the same range as the reference, substrates (i and j) presenting respectively a current intensity which is lower by only a factor 0,3 (i) and 1,2 (j) than the reference.

Fig. 9 shows clearly that substrates according to the invention (o, p and q) may be used as alternatives to the reference substrate (a), the charge injection threshold of substrate (o), (p) and (q) being in the same range as the reference. Figures 10-16 are showing absorption curves from 400 to 800nm from the various examples and are compared to the reference substrate (a). These measurements have been performed with a "Ultrascan PRO" spectrophotometer from Hunter Associates Laboratory, Inc. VA-USA.

These figures are showing that the absorption is still at a reasonable level for all the examples. Only few spectra (m+, q ) are presenting an absoption stronger than the (a) comparative example. The maximum increase in the spectra is nevertheless limited to 8% maximum. In all the remaining examples, the absorption is significantly decreased. Most of these absorption decreases are preferably occurring in the blue for substrates according to the invention (see table 2)·

Table 2 shows the influence of the electrode structure on the electrical performance of OLED and on the absorption data in the blue region at 450nm. It compares various substrates according to the invention to TCC references. The absorption in the blue region at 450nm was measured on the coating side of samples before OLED deposition, with a "Ultrascan PRO" spectrophotometer from Hunter Associates Laboratory, Inc. VA-USA.

Table 2:

References Current intensity (mA) Absorption (coating-side) at

at 4 V wavelength = 450nm

(a) 0.52 20.9%

(a') 0.50 20.0%

(b) 7.99 15.6%

(c) 7.94 37.5%

(d) 3.62 15.9% (e) 0.95 -

(f) 0.14 -

(g) 0.41 17.4%

CO 0.21 10.9%

(i) 0.14 16.4% ω 0.60 15.5%

(k) - 11.3%

(1) - 15.8%

(m) - 14.8%

All the examples according to the invention show at least a benefit either in term of better electrical performance or in term of lower intrinsic blue absorption. In the current state-of-the-art, the blue colour is generally the most difficult to produce from less efficient fluorescent or phosphorescent emitters. The electrode should reduce any inefficient lost and then avoid as much as possible the absorption in this precious blue range.

In order to screen the potential nitrides to be applied as final dielectric nitride-based layer in any embodiment of the invention, thick monolayers have been deposited on 2mm thick soda-lime glass substrates (size 10x10cm²). 150nm thick layers (calibrated using the well-known stylus method) have been sputtered under 18sccm N₂ / 32 seem Ar, except elsewhere stated, giving about 0.4 Pa pressure. In the case of ternary compounds, a 5cm diameter Si target (power either 1 unit = 300W or 2 units = 600 W) and a second 5 cm diameter target (set at a reduced power compared to the Si target) were co- sputtered together to produce the nitride. For simple nitride coatings, the target diameter was 10cm and the applied power 500W. Deposition time was adjusted to reach 150nm (+/- 5%). As comparative examples, ZnSnO or ZnAlO oxides have been used as references. In that case, pure 02 gas was used at 0.4 Pa pressure from 10cm diameter targets running at 500W. Sn content was 10 wt % in ZnSn target while 2 wt % Al doping was added to Zn target in the other case.

Figure 17 shows the resistivity (Rho) for these various compounds. Rho has been deduced from sheet resistance measurements assuming the targeted 150nm thickness for nitrides mono-layers deposited on 2mm soda- lime glass. Rho is presented in Log scale for various investigated nitride compounds as well as for 2 oxides references (ZnSnO and ZnAlO). For more conductive samples (Rho < 1 ohm.cm), Loresta AP MCP-T4000 sheet resistivity meter has been used, while Hioki SM8220 has measured less conductive compound (Rho>100 ohm.cm).

The ratio (xx/yy) given for each compound in figure 17 indicates the Ar/N2 flow ratio used during deposition for simple nitride. With these ratios, a pressure about 0.4 Pa is obtained in the chamber. Aa(xx):Si(yy) indicates the power ratio (xx vs. yy) used during the co-sputtering of the SixAayNz compound.

Surprisingly, we have observed that all the investigated sputtered nitrides are exhibiting a resistivity value significantly lower than reference oxides making them all candidates for better charge transfer in the multilayer stack described by the inventors.

Some of these nitride samples were also investigated with an AC1 tool (made by Riken Keiki Co., Ltd Tokyo - Japan) to measure the work function of nitrides (WF - in eV) against slope (in arbitrary intensity unit/eV). Figure 18 shows said work function of nitrides against slope recorded by said AC1 tool on 150nm mono-layers deposited on glass. The various nitride natures are indicated by their label on the figure. The power ratio between the Si and Xx for co- sputtered species is indicated by the marker type. By default, the gas ratio has been maintained to 18/32 (Ar/N2) during co-sputtering of nitride ternary compounds SixXxyNz.

These measurements on co-sputtered mono-layers show that the combination of two different nitrides allows tuning the electrical properties of the surface such as WF. This can be advantageously applied to the final dielectric nitride based layer of the invention. As example, Mo or Cr addition inside Si nitride allows to tune WF from about 4.25eV to 5.2eV.

Figure 19 shows the work function (WF - in eV) against slope (in arbitrary intensity unit/eV) recorded by AC1 tool (made by Riken Keiki Co., Ltd Tokyo - Japan) on 150nm thick ZrNx mono-layers deposited on glass. The various Ar/N2 flows used during deposition are indicated by the marker type on the figure. This figure shows that mastering the flows used during deposition is one way to control the electrical properties of the surface such as WF. This can be advantageously applied to the final dielectric nitride based layer of the invention. As example, zircomiun nitride applied as thin final layer allows to tune WF from about 4.2eV to 5.2eV.

Claims

1. Transparent substrate (1) for photonic devices comprising a support (10) and an electrode (11), said electrode (11) comprising a stack of layers comprising, starting from the support (10), successively, a first dielectric layer (110), a metal conduction layer (111), a buffer layer (112) and a final dielectric nitride based layer (113) characterized in that said buffer layer (112) is in direct contact with the metal conduction layer (111) and said final dielectric nitride based layer (113) is in direct contact with the buffer layer (112).

2. Transparent substrate (1) according to claim 1, wherein the final dielectric nitride based layer (113) has a thickness of at least 0.5 nm and at most 10.0 nm.

3. Transparent substrate (1) according to any preceding claim, wherein the final dielectric nitride based layer (113) comprises a nitride of at least one element selected from the group consisting of Be, Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, In, Si, Ge and Sn.

4. Transparent substrate (1) according to any preceding claim, wherein the final dielectric nitride based layer (113) comprises at least two sublayers of different composition, a primary dielectric nitride based layer (1131) and a top dielectric nitride based layer (1132).

5. Transparent substrate (1) according to any preceding claim, wherein the buffer layer (112) comprises a compound selected from metals, nitrides, oxides, substoichiometric oxides, substoichiometric nitrides and oxynitrides.

6. Transparent substrate (1) according to claim 5, wherein the compound of the buffer layer (112) comprises one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn and Al.

7. Transparent substrate (1) according to any preceding claim, wherein the buffer layer (112) has a thickness of at least 0.5 nm and at most 6.0 nm.

8. Transparent substrate (1) according to claim 1, wherein the buffer layer (112) and the final dielectric nitride based layer (113) form together a layer having a graded concentration of nitride compounds that increases starting from the metal conduction layer (111).

9. Transparent substrate (1) according to any preceding claim, wherein the total thickness of the buffer layer (112) and the final dielectric nitride based layer (113) is at least 0.5 nm and at most 15.0 nm.

10. Transparent substrate (1) according to any preceding claim, wherein the first dielectric layer (113) has a thickness of at least 3.0 nm.

11. Transparent substrate according to any preceding claim wherein the metal conduction layer (111) comprises at least one layer consisting of a metal or a mixture of metals, said metal being selected from the group consisting of Pd, Pt, Cu, Ag and Au.

12. Transparent substrate according to any preceding claim, wherein the electrode (11) is such that the first dielectric layer (110) comprises a crystallisation sublayer (1102), said crystallisation sublayer (1102) being the layer furthest removed from the support (10).

13. Transparent substrate according to claim 12, wherein the thickness of the crystallisation sublayer (1102) is at least 7% of the total thickness of the first dielectric layer (110).

14. Organic light-emitting device comprising at least one transparent substrate according to any one of claims 1 to 13.