Background of the invention.

In many applications there is a requirement for inexpensive transparent conducting layers, but a busbar will be also required for some of the (large area) applications. Highly conductive (non- transparent) patterns can be made by screen-printing conducting pastes such as silver or carbon black pastes. Vacuum evaporation of metals through shadow masks is another method. Yet another method makes use of homogeneous conductive metallized surfaces which can be patterned by use of photoresist technology in combination with a metal etching agent. Photographic films can, under certain conditions, be used for making electrically conductive silver "images".

US 3,664, 837 describes the use of light sensitive evaporated silver halide film which upon exposure and after development results in conductive images. DE 1,938, 373 describes a photographic method for producing conducting paths, resistances and capacitors for microcircuits starting from coated silver halide emulsions. US 3,600, 185 describes the production of electrically conductive patterns by means of diffusion transfer techniques.

Combinations of a transparent polymer-based conductor and a high conductive (non-transparent) pattern are described in some publications. DE-A 196 27 071 discloses an electroluminescent configuration, which contains hole and/or electron injecting layers, wherein the polymeric organic conductor is selected from the group of polyfurans, polypyrroles, polyanilines, polythiophenes and polypyridines. DE-A 196 27 071 also discloses the use of poly (3, 4-ethylenedioxythiophene) as a charge-injection layer on transparent metallic electrodes such as ITO (indium-tin oxide) and that the following materials are suitable as transparent and conductive materials: a) metal oxides e. g. ITO, tin oxide etc.; b) semi-transparent metal films e. g. Au, Pt, Ag, Cu etc. The latter being applied by vacuum techniques.

EP-A 510 541 discloses an organic electroluminescent device having an anode, an organic hole injection transport layer, an

organic luminescent layer and a cathode formed sequentially in this order, wherein the organic hole injection transport layer contains a metal complex and/or a metal salt of an aromatic carboxylic acid.

EP-A 510 541 further discloses that the conductive layers used in such devices may have a multi-layer structure by depositing different types of conductive materials selected from a metal, e. g.

Al, Au, Ag, Ni, Pd or Te, a metal oxide, carbon black or a conductive resin such as poly (3-methylthiophene), but no specific combinations are exemplified.

US 5,447, 824 discloses a method of manufacturing a pattern of an electrically conductive polymer on a substrate surface, said method comprising: a) forming a liquid layer on a surface of said substrate from a solution containing a material capable of forming said electrically conductive polymer upon being heated, e. g. 3,4- ethylenedioxythiophene, an oxidizing agent and a base, b) exposing said liquid layer to patterned radiation, and c) heating said layer thereby forming a pattern of an electrically conductive polymer, said conductive polymer being formed in unexposed areas and a non- conductive polymer being formed in the exposed areas of the layer.

The galvanic provision of the conductive polymer pattern with a metal layer, e. g. silver, copper, nickel or chromium, is also disclosed in US 5,447, 824.

Wo 98/54767 discloses a conductive layer system, particularly for a transparent or semi-transparent electrode or electroluminescent configuration, comprising at least two layers, characterized in that the first layer contains an organic or organometallic electrically conductive polymer, which is transparent or semi-transparent in the visible range of the electromagnetic spectrum, e. g. a polymer selected from the group consisting of polythiophene, polypyrrole, polyaniline, polyacetylene or their optionally substituted derivatives and the second layer contains at least one electrically conductive inorganic compound or a metal or an appropriately doped semi-metal e. g. a material selected from the group consisting of Cu, Ag, Au, Pt, Pd, Fe, Cr, Sn, Al or their alloys or conductive carbon. In a preferred embodiment the second layer is a conductive pattern formed by an open grid structure, preferably with a 5-500 im grid so that it cannot be perceived by the human eye. Invention example 2 discloses a poly (3,4-ethylenedioxythiophene) [PEDOT] /poly (styrene sulphonate) [PSS] layer with a surface resistivity of 1500 square to which conducting tracks of"Leitsilber" (a silver particle dispersion) ca. 2 mm wide had been applied by a printing technique.

The layer configuration disclosed in Example 2 of WO 98/54767 has the disadvantages of the grid of"Leitsilber"requiring a thickness of 5 to 10 im to realize layers with a surface resistance of 0.5 to 1 92/square, which means that the surface of the configuration will have a certain roughness which will limit its applications, making it difficult to apply a thin, e. g. 100 nm, functional layer. Furthermore, an aqueous PEDOT/PSS dispersion would not wet such a"Leitsilber"grid and hence a usable multilayer conductive configuration would not result.

Moreover, with an intrinsically conductive polymer layer or a metal grid outermost wetting problems arise as regards coating of thin functional layers. Furthermore, for devices requiring very thin functional layers such as transistors, the thickness of a multilayer electrode and even slight deviations from flatness are disadvantageous in their production.

Aspects of the invention.

It is therefore an aspect of the present invention to provide a conductive electrode with similar properties, but thinner than multilayer electrodes comprising a conductive polymer layer and a conductive metal layer with an outermost layer with improved flatness.

It is a further aspect of the present invention to provide a process for preparing a conductive electrode with similar properties, but thinner than multilayer electrodes comprising a conductive polymer layer and a conductive metal layer with an outermost layer with improved flatness.

It is also an aspect of the present invention to prevent ion migration from the conductive electrode.

Further aspects and advantages of the invention will become apparent from the description hereinafter.

Summary of the invention.

It has been surprisingly found that a thin substantially transparent conductive layer with high conductivity and with an outermost surface with improved flatness can be realized in a layer containing an intrinsically conductive polymer, e. g. PEDOT/PSS, and a conductive metal, e. g. silver, non-uniformly distributed therein to which functional layers can be readily applied.

Upon applying a potential between the conductive layer, according to the present invention, as cathode and a counter- electrode as cathode under conditions of high relative humidity metal ions present at the anode, there always being an equilibrium between metal ions and metal atoms, diffuse under the applied potential to the cathode, where they are deposited at metal atoms which stack forming dendritic metal which grow towards the anode.

This results long term in short circuiting of the electrodes.

In the case of conductive layers containing silver ions migrate and silver dendrites are formed. The use of benzotriazole as a silver electrode-stabilizer is disclosed in US 4,821, 148 and US 6,174, 606 and Evenpoel et al. in 1970 disclosed the use of thiourea in Metallurgie X, volume 4, page 132, and Ambland et al. in 1978 disclosed the use of tartaric acid in Surface Technology, volume 6, pages 409-423. However, these remedies were unsuccessful with the conductive layer of the present invention. Surprisingly, it has been found that particular phenyl-mercaptotetrazole compounds are capable of substantially preventing the formation of silver dendrites.

Aspects of the present invention are realized by a substantially transparent conductive layer on a support, the layer comprising an intrinsically conductive polymer and a conductive metal non-uniformly distributed therein and forming of itself a conductive entity.

Aspects of the present invention are also realized by a process for preparing a substantially transparent conductive layer on a support, the layer comprising an intrinsically conductive polymer and a conductive metal non-uniformly distributed therein and forming of itself a conductive entity, comprising the step of: preparing the non-uniformly distributed conductive metal by a photographic process.

Aspects of the present invention are also realized by a light emitting diode comprising the above-described conductive layer or produced according to the above-described process.

Aspects of the present invention are also realized by a photovoltaic device comprising the above-described conductive layer or produced according to the above-described process.

Aspects of the present invention are also realized by a transistor comprising the above-described conductive layer or produced according to the above-described process.

Aspects of the present invention are also realized by an electroluminescent device comprising the above-described conductive layer or produced according to the above-described process.

Preferred embodiments are disclosed in the dependent claims.

Detailed description of the invention.

Figure 1 shows four silver patterns, pattern (a) representing a continuous silver layer 3 x 3 cm2 in area, pattern (b) representing a regular strip pattern, the parallel strips being 10 mm apart and having a width of 1 mm; pattern (c) representing a regular strip pattern, the parallel strips being 5 mm apart and having a width of 150 pm ; and pattern (d) representing no silver development.

Definitions The term alkyl means all variants possible for each number of carbon atoms in the alkyl group i. e. for three carbon atoms: n- propyl and isopropyl ; for four carbon atoms: n-butyl, isobutyl and tertiary-butyl; for five carbon atoms: n-pentyl, 1, 1-dimethyl- propyl, 2,2-dimethylpropyl and 2-methyl-butyl etc.

The term aqueous for the purposes of the present invention means containing at least 60% by volume of water, preferably at least 80% by volume of water, and optionally containing water- miscible organic solvents such as alcohols e. g. methanol, ethanol, 2-propanol, butanol, iso-amyl alcohol, octanol, cetyl alcohol etc.; glycols e. g. ethylene glycol; glycerine; N-methyl pyrrolidone; methoxypropanol; and ketones e. g. 2-propanone and 2-butanone etc.

The term"support"means a"self-supporting material"so as to distinguish it from a"layer"which may be coated on a support, but which is itself not self-supporting. It also includes any treatment necessary for, or layer applied to aid, adhesion to the support.

The term continuous layer refers to a layer in a single plane covering the whole area of the support and not necessarily in direct contact with the support.

The term non-continuous layer refers to a layer in a single plane not covering the whole area of the support and not necessarily in direct contact with the support.

The term coating in used as a generic term including all means of applying a layer including all techniques for producing continuous layers, such as curtain coating and doctor-blade coating

and all techniques for producing non-continuous layers such as screen printing, ink jet printing, flexographic printing, and techniques for producing continuous layers The term intrinsically conductive polymer means organic polymers which have (poly)-conjugated s-electron systems (e. g. double bonds, aromatic or heteroaromatic rings or triple bonds) and whose conductive properties are not influenced by environmental factors such as relative humidity.

The term"conductive"is related to the electric resistance of the material. The electric resistance of a layer is generally expressed in terms of surface resistance Rs (often specified as /square). Alternatively, the conductivity may be expressed in terms of volume resistivity Rv = Rs d, wherein d is the thickness of the layer, volume conductivity kv = 1/Rv [unit: S (iemens) /cm] or surface conductance ks = 1/Rs [unit: S (iemens). square].

The term photographic refers to any photochemical process particularly those based on silver halide processes.

The term silver salt diffusion transfer process refers to a process developed independently by A. Rott [GB 614,155 and Sci.

Photogr. , (2) 13,151 (1942)] and E. Weyde [DE 973,769] and described by G. I. P. Levenson in Chapter 16 of"The Theory of the Photographic Process Fourth Edition", edited by T. H. James, pages 466 to 480, Eastman Kodak Company, Rochester (1977).

The term substantially transparent means that the integral transmission of visible light is above 50% of the incident light normal to the conductive layer of the present invention i. e. the layer had an overall optical density of less than 0.30, although local transmission of visible light though the lines of the silver pattern may be well below 10% of the incident light normal to the conductive layer of the present invention i. e. well above an optical density of 1.0.

The abbreviation PEDOT represents poly (3,4-ethylenedioxy- thiophene).

The abbreviation PSS represents poly (styrene sulphonic acid) or poly (styrenesulphonate).

Conducting layer Aspects of the present invention are realized by a substantially transparent conductive layer on a support, the layer comprising an intrinsically conductive polymer and a conductive

metal non-uniformly distributed therein and forming of itself a conductive entity.

According to a first embodiment of the conducting layer, according to the present invention, the conductive metal is silver. intrinsically conductive polymer The intrinsically conductive polymers used in the present invention can be any intrinsically conductive polymer known in the art e. g. polyacetylene, polypyrrole, polyaniline, polythiophene, etc. Details about suitable intrinsically conductive polymers can be found in textbooks, such as"Advances in Synthetic Metals", ed.

P. Bernier, S. Lefrant, and G. Bidan, Elsevier, 1999; "Intrinsically Conducting Polymers: An Emerging Technology", Kluwer (1993);"Conducting Polymer Fundamentals and Applications, A Practical Approach", P. Chandrasekhar, Kluwer, 1999; and"Handbook of Organic Conducting Molecules and Polymers", Ed. Walwa, Vol. 1-4, Marcel Dekker Inc. (1997).

According to a second embodiment of the conductive layer process, according to the present invention, the intrinsically conductive polymer contains structural units represented by formula (I) : in which, each of Rl and R2 independently represents hydrogen or a Cl-4 alkyl group or together represent an optionally substituted C_4 alkylene group or a cycloalkylene group.

According to a third embodiment of the conductive layer, according to the present invention, the intrinsically conductive polymer is a polymer or copolymer of a 3,4-dialkoxythiophene in which the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge.

According to a fourth embodiment of the conductive layer, according to the present invention, the intrinsically conductive polymer is a polymer or copolymer of a 3,4-dialkoxy-thiophenes in which the two alkoxy groups together represent an optionally

substituted oxy-alkylene-oxy bridge and is selected from the group consisting of: poly (3,4-methylenedioxythiophene), poly (3,4- methylenedioxythiophene) derivatives, poly (3,4-ethylenedioxy- thiophene), poly (3,4-ethylenedioxythiophene) derivatives, poly (3,4- propylenedioxythiophene), poly (3,4-propylenedioxythiophene) derivatives, poly (3,4-butylenedioxythiophene) and poly (3,4- butylenedioxythiophene) derivatives and copolymers thereof.

According to a fifth embodiment of the conductive layer, according to the present invention, the intrinsically conductive polymer is a polymer or copolymer of a 3,4-dialkoxy-thiophenes in which the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge and the substituents for the oxy-alkylene-oxy bridge are alkyl, alkoxy, alkyloxyalkyl, carboxy, alkylsulfonato and carboxy ester groups.

According to a sixth embodiment of the conductive layer, according to the present invention, the intrinsically conductive polymer is a polymer or copolymer of a 3,4-dialkoxy-thiophenes in which the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge and the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge which is a 1,2-ethylene group, an optionally alkyl- substituted methylene group, an optionally C1_l2-alkyl-or phenyl- substituted 1,2-ethylene group, a 1,3-propylene group or a 1,2- cyclohexylene group.

Such polymers are disclosed in Handbook of Oligo-and Polythiophenes Edited by D. Fichou, Wiley-VCH, Weinheim (1999); by L. Groenendaal et al. in Advanced Materials, volume 12, pages 481- 494 (2000); L. J. Kloeppner et al. in Polymer Preprints, volume 40 (2), page 792 (1999); P. Schottland et al. in Synthetic Metals, volume 101, pages 7-8 (1999); and D. M. Welsh et al. in Polymer Preprints, volume 38 (2), page 320 (1997).

Organic polymer containing structural units according to formula (I) can be polymerized chemically or electrochemically.

Chemical polymerization can be carried out oxidatively or reductively. The oxidation agents used for the oxidative polymerisation of pyrrole, such as described for example in J.

Amer. Chem. Soc. , vol. 85, pages 454-458 (1963) and J. Polym. Sci.

Part A Polymer Chemistry, volume 26, pages 1287-1294 (1988), can be utilized for the oxidative polymerization of thiophenes. According to a seventh embodiment of the present invention, the inexpensive and easily accessible oxidation agents such as iron (III) salts such as FeCl3, the iron (III) salts of organic acids, e. g. Fe (OTs) 3, H202,

K2Cr207, alkali and ammonium persulphates, alkali perborates and potassium permanganate are used in the oxidative polymerization.

Theoretically the oxidative polymerization of thiophenes requires 2.25 equivalents of oxidation agent per mole thiophene of formula (I) [see e. g. J. Polymer Science Part A Polymer Chemistry, volume 26, pages 1287-1294 (1988) ]. In practice an excess of 0.1 to 2 equivalents of oxidation agent is used per polymerizable unit.

The use of persulphates and iron (III) salts has the great technical advantage that they do not act corrosively. Furthermore, in the presence of particular additives oxidative polymerization of the thiophene compounds according to formula (I) proceeds so slowly that the thiophenes and oxidation agent can be brought together as a solution or paste and applied to the substrate to be treated.

After application of such solutions or pastes the oxidative polymerization can be accelerated by heating the coated substrate as disclosed in US 6,001, 281 and WO 00/14139 herein incorporated by reference.

Reductive polymerization can be performed using the Stille (organotin) or Suzuki (organoboron) routes described in 2002 by Appperloo et al. in Chem. Eur. Journal, volume 8, pages 2384-2396, and as disclosed in 2001 in Tetrahedron Letters, volume 42, pages 155-157 and in 1998 in Macromolecules, volume 31, pages 2047-2056 respectively or with nickel complexes as disclosed in 1999 in Bull.

Chem. Soc. Japan, volume 72, page 621 and in 1998 in Advanced Materials, volume 10, pages 93-116.

1-phenyl-5-mercato-tetrazole compound in which the phenyl group is substituted with one or more electron accepting groups According to a seventh embodiment of the conducting layer, according to the present invention, the conductive layer further contains a silver-ion stabilizer.

According to an eighth embodiment of the conducting layer, according to the present invention, the conductive layer further contains a silver-ion stabilizer which is a 1-phenyl-5-mercato- tetrazole compound in which the phenyl group is substituted with one or more electron accepting groups.

According to a ninth embodiment of the conducting layer, according to the present invention, the conductive layer further contains a silver-ion stabilizer which is a 1-phenyl-5-mercato- tetrazole compound in which the phenyl group is substituted with one or more electron accepting groups groups selected from the

group consisting of chloride, fluoride, cyano, sulfonyl, nitro, acid amido and acylamino groups.

According to a tenth embodiment of the conducting layer, according to the present invention, the conductive layer further contains a silver-ion stabilizer which is selected from the group consisting of: 1-(3', 4'-dichlorophenyl)-5-mercapto-tetrazole,

Suitable 1-phenyl-5-mercapto-tetrazole compounds with substituted phenyl groups [PMT], according to the present invention, include: Structural formula PMT01 ci 1- (31, 41- Cl + dichlorophenyl)-5- mercapto-tetrazole s N,, N N-N I I H H PMT02 N 1-(3-acetylamino- phenyl)-5-mercapto- 0 tetrazole HS zu NIT N PMT03 H H N) fSyN o O HS Nt HO NEZ PMT 0 4 H N-N N-N PMT04 H N \ T PMT05 . PMT05 0 0= =0 /0 0= i =O OH Na 12 "dz Y, 11 f1 N PMT06 1-(3'-benzoylamino- H phenyl)-5-mercapto- tetrazole /o PO HSstí N K 0 7 ; f PMT07 H H Nu oh cl HS Nez HsCz/CzHs N-N c2H5 PMT08 H N I-i s II o\C2H5 0 0 L' 0 0 HS f ft HSofNs N- PMT09 H \ ,. 5 "j L' 0 0 Na HS Na" Na Y, PMT10 PMT /0 0 OH HS'N I HS N N---N n n r H N-N HsC2/C2H5 N-N H 5 c 2--, C2HS C2Hs PMT11 H " ?) N-N H S N,, N N N-N PMT12 N (CHZ) a \ f 1 So s'CzHS /O N-N H N N PUT13 PMT13 H O N N cp SH . N N . N-N 0 PMT14 H N H /N. N/. 0 i H HS'N N N---N

Process for preparing a conductive layer Aspects of the present invention are also realized by a process for preparing a substantially transparent conductive layer on a support, the layer comprising an intrinsically conductive polymer and a conductive metal non-uniformly distributed therein and forming of itself a conductive entity, comprising the step of: preparing the non-uniformly distributed conductive metal by a photographic process.

According to a first embodiment of the process, according to the present invention, the photographic process comprises the steps of: coating the support with a layer containing the intrinsically conductive polymer and a nucleation agent; producing a non- continuous silver layer in the nucleation layer using silver salt diffusion transfer.

According to a second embodiment of the process, according to the present invention, the photographic process comprises the steps of: coating the support with a layer containing the intrinsically conductive polymer and palladium sulphide e. g. palladium sulphide nanoparticles, as a nucleation agent; producing a non-continuous silver layer in the nucleation layer using silver salt diffusion transfer.

According to a third embodiment of the process, according to the present invention, the photographic process comprises the steps of: coating the support with a layer containing an intrinsically conductive polymer, silver halide and gelatin with a weight ratio of gelatin to silver halide in the range of 0.05 to 0.3, image-wise exposing the layer, and developing the exposed layer to produce the non-uniformly distributed silver.

Surfactants According to an eleventh embodiment of the conductive layer, according to the present invention, the conductive layer further contains a surfactant.

According to a twelfth embodiment of the conductive layer, according to the present invention, the conductive layer further contains a non-ionic surfactant e. g. ethoxylated/fluoroalkyl surfactants, polyethoxylated silicone surfactants, polysiloxane/polyether surfactants, ammonium salts of perfluoro- alkylcarboxylic acids, polyethoxylated surfactants and fluorine- containing surfactants.

Suitable non-ionic surfactants include: Surfactant no. 01 = ZONYLTM FSN, a 40% by weight solution of F (CF2CF2) 1-gCH2CH20 (CH2CH20) xH in a 50% by weight solution of isopropanol in water where x = 0 to about 25, from DuPont; Surfactant no. 02 = ZONYL FSN-100 : F (CF2CF2) 1-gCH2CH2O (CH2CH20) xH where x = 0 to about 25, from DuPont; Surfactant no. 03 = ZONYLTM FS300, a 40% by weight aqueous solution

of a fluorinated surfactant, from DuPont; Surfactant no. 04 = NONYL FSO, a 50% by weight solution of a mixture of ethoxylated non-ionic fluoro- surfactant with the formula: F (CF2CF2) 1-7CH2CH2O (CH2CH20) yH where y = 0 to ca.

15 in a 50% by weight solution of ethylene glycol in water, from DuPont; Surfactant no. 05 = ZONYLTM FSO-100, a mixture of ethoxylated non- ionic fluoro-surfactant from DuPont with the formula : F (CF2CF2) 1_7CH2CH20 (CH2CH20) yH where y = 0 to ca. 15 from DuPont; Surfactant no. 06 = TegoglideTM 410, a polysiloxane-polymer copolymer surfactant, from Goldschmidt; Surfactant no. 07 = TegowetTM, a polysiloxane-polyester copolymer surfactant, from Goldschmidt; Surfactant no. 08 = FLUORADFC431 : CF3 (CF2)7SO2(C2H5)N-CH2CO-(OCH2CH2) nOH from 3M; Surfactant no. 09 = FLUORADFC126, a mixture of the ammonium salts of perfluorocarboxylic acids, from 3M; Surfactant no. 10 = Polyoxyethylene-10-lauryl ether Surfactant no. 11 = FLUORAD'mFC430, a 98.5% active fluoroaliphatic ester from 3M; According to a thirteenth embodiment of the conductive layer, according to the present invention, the conductive layer further contains an anionie surfactant.

Suitable anionic surfactants include: Surfactant no. 12 = NONYL 7950, a fluorinated surfactant, from DuPont; Surfactant no. 13 = ZONYLTM FSA, 25% by weight solution of F (CF2CF2) 1-gCH2CH2SCH2CH2COOLi in a 50% by weight solution of isopropanol in water, from DuPont; Surfactant no. 14 = ZONYLTM FSE, a 14% by weight solution of [F (CF2CF2) 1-7CH2CH2O] xP (O) (ONH4) y where x = 1 or 2; y = 2 or 1; and x + y = 3 in a 70% by weight aqueous ethylene glycol solution, from DuPont; Surfactant no. 15 = ZONYLTM FSJ, a 40% by weight solution of a blend of F (CF2CF2) 1-7CH2CH2O] xP (O) (ONH4) y where x = 1 or 2; y = 2 or 1; and x + y = 3 with a hydrocarbon surfactant in 25% by weight solution of isopropanol in water, from DuPont;

Surfactant no. 16 = ZONYLT FSP, a 35% by weight solution of [F (CF2CF2) 1_7CH2CH2o] xP (0) (ONH4) y where x = 1 or 2; y = 2 or 1 and x + y = 3 in 69.2% by weight solution of isopropanol in water, from DuPont; Surfactant no. 17 = ZONYLTM UR: [F (CF2CF2) 1_7CH2CH2O] xP (0) (OH) y where x - 1 or 2 ; y = 2 or 1 and x + y = 3, from DuPont; Surfactant no. 18 = ZONYLT TBS : a 33% by weight solution of F (CF2CF2) 3_8CH2CH2SO3H in a 4.5% by weight solution of acetic acid in water, from DuPont; Surfactant no. 19 = ammonium salt of perfluoro-octanoic acid from 3M Binder According to a fourteenth embodiment of the conductive layer, according to the present invention, the conductive layer further contains a binder.

Crosslinking agent According to a fifteenth embodiment of the conductive layer, according to the present invention, the conductive layer further contains a cross-linking agent.

Support According to a sixteenth embodiment of the conductive layer, according to the present invention, the support is transparent or translucent.

According to a seventeenth embodiment of the conductive layer, according to the present invention, the support is a polymeric film, silicon, a ceramic, an oxide, glass, polymeric film reinforced glass, a glass/plastic laminate, a metal/plastic laminate, optionally treated paper and laminated paper.

According to an eighteenth embodiment of the conductive layer, according to the present invention, the support is provided with a subbing layer or other adhesion promoting means to aid adhesion to the substantially transparent conductive layer.

According to a nineteenth embodiment of the conductive layer, according to the present invention, the support is a transparent or translucent polymer film.

A transparent or translucent support suitable for use with the electroconductive or antistatic layers, according to the present

invention, may be rigid or flexible and consist of a glass, a glass-polymer laminate, a polymer laminate, a thermoplastic polymer or a duroplastic polymer. Examples of thin flexible supports are those made of a cellulose ester, cellulose triacetate, polypropylene, polycarbonate or polyester, with poly (ethylene terephthalate), poly (ethylene naphthalene-1, 4-dicarboxylate), polystyrene, polyethersulphone, polycarbonate, polyacrylate, polyamide, polyimides, eellulosetriacetate, polyolefins and poly (vinylchloride), optionally treated by corona discharge or glow discharge or provided with a subbing layer.

Electroluminescent devices Aspects of the present invention are also realized by an electroluminescent device comprising the conductive layer, according to the present invention, or produced according to the process, according to the present invention.

Thin film electroluminescent devices (ELDs) are all characterized by one (or more) electroluminescent active layer (s) sandwiched between two electrodes. Optionally a dielectric layer may also be part of the sandwich.

Thin film ELDs can be subdivided into organic and inorganic based ELDs. Organic-based thin film ELDs can be subdivided into low molecular weight organic devices including ologomers (Organic Light Emitting Diodes (OLEDs) ) and high molecular weight organic devices (Polymer Light Emitting Diodes (PLEDs). The inorganic ELDs on the other hand can be further subdivided into the High Voltage Alternating Current (HV-AC) ELDs and the Low Voltage Direct Current (LV-DC) ELDs. The LV-DC ELDs include Powder ELDs (DC-PEL Devices or DC-PELDs) and thin film DC-ELDs, hereinafter called Inorganic Light Emitting Diodes (ILEDs).

The basic construction of organic ELDs (PLED and OLED) comprises following layer arrangement : a transparent substrate (glass or flexible plastic), a transparent conductor, e. g. Indium Tin oxide (ITO), a hole transporting layer, a luminescent layer, and a second electrode, e. g. a Ca, Mg/Ag or Al/Li electrode. For OLEDs the hole transporting layer and the luminescent layer are 10- 50 nm thick and applied by vacuum deposition, whereas for PLEDs the hole transporting layer is usually about 40 nm thick and the luminescent layer is usually about 100 nm thick and applied by spin coating or other non-vacuum coating techniques. A direct voltage of 5-10 V is applied between both electrodes and light emission

results from holes and electrons being injected from the positive and negative electrodes respectively combining in the luminescent layer thereby producing the energy to excite the luminescent species to emit light.

In OLEDs the hole transporting layer and electroluminescent layer consist of low molecular organic compounds, N, N'-diphenyl- 1, 1'-biphenyl-4, 4'-diamine (TPD) can, for example be used as the hole transporter and aluminium (III) 8-hydroxyquinoline complex (Alq3), polyaromatics (anthracene derivatives, perylene derivatives and stilbene derivatives) and polyhetero-aromatics (oxazoles, oxadiazoles, thiazoles etc. ) can be used as electroluminescent compounds.

In PLEDs electroluminescent compounds that can be used are polymers like the non-conjugated polyvinylcarbazole derivatives (PVK) or conjugated polymers like poly (p-phenylene vinylenes) (PPV), polyfluorenes, poly (3-alkylthiophene), poly (p-phenylene ethynylenes) etc.

Low voltage DC PEL Devices generally comprise a transparent substrate, a transparent conductor (ITO), a doped ZnS phosphor layer (20um), and a top electrode of evaporated aluminium. The phosphor layer is applied by means of the doctor blade technique or screen printing on an ITO conducting layer. Subsequently an aluminium electrode is applied by evaporation. Upon applying a direct current voltage of several volts (ITO positive), holes start moving towards the aluminium electrode, thereby creating an insulating region (about 1 um in thickness) next to the ITO layer within one minute or so. This results in a current drop which is associated with the onset of light emission. This process has been called the forming process. In the thin high resistive phosphor layer thereby formed, high electric fields occur and electroluminescence is already possible at low voltages (typically between 10 and 30 V).

In hybrid LEDs, inorganic emitting so-called quantum dots are used in combination with organic polymers with charge transporting properties and in some cases also emitting properties. Hybrid LEDs with CdSe nano particles have been reported by Colvin et al. [see Nature, volume 370, pages 354-357, (1994) ], Dabbousi et al. [see Appl. Phys. Lett. , volume 66, pages 1316-1318 (1995), and Gao et al. [see J. Phys. Chem. B, volume 102, pages 4096-4103 (1998)], herein incorporated by reference.

Light-emitting devices with ZnS: Cu nano-crystals and a non- semiconducting polymer have been reported by Huang et al. [see

Appl. Phys. Lett. , volume 70, pages 2335-2337 (1997) ] and Que et al. [see Appl. Phys. Lett. , volume 73, pages 2727-2729 (1998)], herein incorporated by reference, with turn on voltages below 5 V.

According to a first embodiment of the electroluminescent device, according to the present invention, the electroluminescent device is a light emitting diode.

According to a second embodiment of the electroluminescent device, according to the present invention, the electroluminescent device further comprises a layer of an electroluminescent phosphor.

According to a third embodiment of the electroluminescent device, according to the present invention, the electroluminescent device comprises a layer of an electroluminescent phosphor, wherein the electroluminescent phosphor belongs to the class of II-VI semiconductors e. g. ZnS, or is a combination of group II elements with oxidic anions, the most common being silicates, phosphates, carbonates, germanates, stannates, borates, vanadates, tungstates and oxysulphates. Typical dopants are metals and all the rare earths e. g. Cu, Ag, Mn, Eu, Sm, Tb and Ce.

According to a fourth embodiment of the electroluminescent device, according to the present invention, the electroluminescent device comprises a layer of an electroluminescent phosphor, wherein the electroluminescent phosphor is encapsulated with a transparent barrier layer against moisture e. g. A1203 and A1N. Such phosphors are available from Sylvania, Shinetsu polymer KK, Durel, Acheson and Toshiba. An example of coatings with such phosphors is 72X, available from Sylvania/GTE, and coatings disclosed in US 4,855, 189.

According to a fifth embodiment of the electroluminescent device, according to the present invention, the electroluminescent device further comprises a layer of an electroluminescent phosphor, wherein the electroluminescent phosphor is ZnS doped with manganese, copper or terbium, or CaGa2S4 doped with cerium e. g. the electroluminescent phosphor pastes supplied by DuPont: LUXPRINTTM type 7138J, a white phosphor; LUXPRIN7M type 7151J, a green-blue phosphor; and LUXPRINT0M type 7174J, a yellow-green phosphor; and ELECTRODAGTM EL-035A supplied by Acheson.

According to a sixth embodiment of the electroluminescent device, according to the present invention, the electroluminescent device further comprises a layer of an electroluminescent phosphor, wherein the electroluminescent phosphor is a zinc sulphide phosphor doped with manganese and encapsulated with A1N.

According to a seventh embodiment of the electroluminescent device, according to the present invention, the electroluminescent device further comprises a dielectric layer.

Any dielectric material may be used in the dielectric layer, with yttria and barium titanate being preferred e. g. the barium titanate paste LUXPRINTTM type 7153E high K dielectric insulator supplied by DuPont and the barium titanate paste ELECTRODAGTM EL-040 supplied by Acheson. A positive ion exchanger may be incorporated into the dielectric layer to capture any ions dissolving escaping from the phosphor of the light-emitting layer. The amount of ion exchanger in the dielectric layer has to be optimized so that it has a maximum effectiveness in reducing black spots while not reducing the initial brightness level. It is therefore preferred to add 0.5 to 50 parts by weight of ion exchanger to 100 parts by weight of the total amount of resin and dielectric material in the dielectric layer. The ion exchanger may be organic or inorganic.

Suitable inorganic ion exchangers are hydrated antimony pentoxide powder, titanium phosphate, salts of phosphoric acid and silicic acid and zeolite.

Aspects of the present invention are also realized by a light emitting diode comprising the above-described conductive layer or produced according to the above-described process.

According to a first embodiment of the light-emitting diode, according to the present invention, the light-emitting diode further comprises a electroluminescent layer comprising a low molecular weight electroluminescent compound.

According to a second embodiment of the light-emitting diode, according to the present invention, the light-emitting diode further comprises a electroluminescent layer comprising a polymeric electroluminescent compound.

According to a third embodiment of the light-emitting diode, according to the present invention, the light-emitting diode further comprises electroluminescent quantum dots.

Photovoltaic devices Aspects of the present invention are also realized by a photovoltaic device comprising the conductive layer, according to the present invention, or produced according to the process, according to the present invention.

Aspects of the present invention are also realized by a solar cell comprising the conductive layer, according to the present

invention, or produced according to the process, according to the present invention.

According to a first embodiment of the photovoltaic device, according to the present invention, the photovoltaic device further comprises at least one photovoltaic layer. The photovoltaic layer may be organic layer, a hybrid inorganic and organic layer or an inorganic layer.

Photovoltaic devices incorporating the conductive layer, according to the present invention, can be of two types: the regenerative type which converts light into electrical power leaving no net chemical change behind in which current-carrying electrons are transported to the anode and the external circuit and the holes are transported to the cathode where they are oxidized by the electrons from the external circuit and the photosynthetic type in which there are two redox systems one reacting with the holes at the surface of the semiconductor electrode and one reacting with the electrons entering the counter-electrode, for example, water is oxidized to oxygen at the semiconductor photoanode and reduced to hydrogen at the cathode. In the case of the regenerative type of photovoltaic cell, as exemplified by the Graetzel cell, the electron transporting medium may be a nano-porous metal oxide semiconductor with a band-gap of greater than 2.9 eV, such as titanium dioxide, niobium (V) oxide, tantalum (V) oxide and zinc oxide, the hole transporting medium may be a liquid electrolyte supporting a redox reaction, a gel electrolyte supporting a redox reaction, an organic hole transporting material, which may be a low molecular weight material such as 2, 2', 7, 7'-tetrakis (N, N-di-p- methoxyphenyl-amine) 9, 9'-spirobifluorene (OMeTAD) or triphenylamine compounds or a polymer such as PPV-derivatives, poly (N- vinylcarbazole) etc. , or inorganic semiconductors such as CuI, CuSCN etc. The charge transporting process can be ionic as in the case of a liquid electrolyte or gel electrolyte or electronic as in the case of organic or inorganic hole transporting materials.

Such regenerative photovoltaic devices can have a variety of internal structures in conformity with the end use. Conceivable forms are roughly divided into two types: structures which receive light from both sides and those which receive light from one side.

An example of the former is a structure made up of a transparently conductive layer e. g. an ITO-layer or a PEDOT/PSS-containing layer and a transparent counter electrode electrically conductive layer e. g. an ITO-layer or a PEDOT/PSS-containing layer having interposed therebetween a photosensitive layer and a charge transporting

layer. Such devices preferably have their sides sealed with a polymer, an adhesive or other means to prevent deterioration or volatilization of the inside substances. The external circuit connected to the electrically-conductive substrate and the counter electrode via the respective leads is well-known.

Alternatively the spectrally sensitized nano-porous metal oxide, according to the present invention, can be incorporated in hybrid photovoltaic compositions such as described in 1991 by Graetzel et al. in Nature, volume 353, pages 737-740, in 1998 by U.

Bach et al. [see Nature, volume 395, pages 583-585 (1998) ] and in 2002 by W. U. Huynh et al. [see Science, volume 295, pages 2425- 2427 (2002) ]. In all these cases, at least one of the components (light absorber, electron transporter or hole transporter) is inorganic (e. g. nano-Ti02 as electron transporter, CdSe as light absorber and electron transporter) and at least one of the components is organic (e. g. triphenylamine as hole transporter or poly (3-hexylthiophene) as hole transporter).

Transistors Aspects of the present invention are also realized by a transistor comprising the conductive layer, according to the present invention, or produced according to the process, according to the present invention.

According to a first embodiment of the transistor, according to the present invention, the transistor further comprises a layer with one or more of the electron transporting or hole transporting components described above, but within such a configuration that it can be used as a transistor. The semiconductor can be n-type, p- type or both (ambipolar transistor) and can be either organic or inorganic.

Industrial application A conductive layer, according to the present invention, can be used in a wide range of electronic devices such as photovoltaic devices, solar cells, batteries, capacitors, light emitting diodes, organic and inorganic electroluminescent devices, smart windows, electrochromic devices, sensors for organic and bio-organic materials and field effect transistors [see also chapter 10 of the Handbook of Oligo-and Polythiophenes, Edited by D. Fichou, Wiley- VCH, Weinheim (1999)].

The invention is illustrated hereinafter by way of INVENTION and COMPARATIVE EXAMPLES. The percentages and ratios given in these examples are by weight unless otherwise indicated.

Ingredients used in the comparative experiments of EXAMPLE 2: Structural formula STAB01 < 1-phenyl-5-mercapto-tetrazole N N S"N,, N H N-N H STAB02 sodium tartrate STAB03 thiourea STAB04 Na2S sodium sulphide STAB05 H 5-methyl-s-triazolo [1, 5-a] pyrimidin-7-ol N zon N STAB06 HlsC i0\/SH 11 11 M-N STAB07 (c4H9) SH _ o 4t 0 1 1 O NN STAB08 Na r SH N STAB09 N (CH 2) 2 1 N N N'I N N N

EXAMPLE 1 (COMPARATIVE) Conductive Ag-pattern made by Diffusion Transfer Reaction with conductive PEDOT/PSS on top Preparation of Material A: The preparation of the physical development nuclei (PdS) is described in the example of EP-A 0769 723. From this example solutions Al, B1 and Cl were used to prepare the nuclei. To 1000 ml of this PdS dispersion 10 g of a 10 g/L water solution of Aerosol OT from American Cyanamid and 5 g of a 50 g/L solution of perfluorcaprylamide-polyglycol were added. This dispersion was then coated to a wet layer thickness of 13.5 um on a poly (ethylene terephthalate) support with a 4 im thick gelatine subbing layer and then dried for 60 minutes at 25°C. This is material A.

Preparation of the PEDOT/PSS dispersion: EP-A 686662 and US 5,766, 515 disclose in the example the preparation of a 1.2% PEDOT/PSS dispersion in water. 15 ml of a 2% solution of ZONYLTM FS0100 in water, 1.25 g of Z6040, a silane from DOW CORNING and 25 g of diethylene glycol were added to 106 g of this dispersion to give the PEDOT/PSS dispersion used in the following EXAMPLES.

Preparation of Material B: The above-described PEDOT/PSS dispersion was used to coat Material A to a wet thickness of 40 Fm and was then dried for 15 minutes at 100°C, thereby producing material C.

Preparation of the transfer emulsion layer: The preparation of the silver chlorobromide emulsion and the preparation of the transfer emulsion layer was as disclosed in EP-A 769 723 except that the coverage of silver halide applied was equivalent to 1.25 g/m2 of AgNO3 instead of 2 g/m2 thereof.

Exposure and development of Materials A and B : The transfer emulsion layer was exposed image-wise as shown in Figure 1 and processed in contact with the receiver (Material A and material B) at 25°C for 10s with a AGFA-GEVAERTTM CP297 developer solution.

Preparation of the double layer electrode configuration: Processed material A was coated with the above-described PEDOT/PSS-dispersion to a wet-layer thickness of 50 um and then dried for 20 minutes at 120°C. The surface resistivity of the PEDOT/PSS layer was about 500 square in the non-exposed areas of material A. Material C was thereby prepared.

Evaluation of materials B and C: The surface resistance measurements were carried out as follows: the layer electrode configurations were cut into strips 3.5 cm in width to ensure perfect positioning of the electrode material; parallel copper electrodes each 35 mm long, 3 mm wide and 35 mm apart, capable of forming line contacts and mounted on a TEFLON insulator were brought into contact with the outermost conductive layer of the strip giving a contacting area of 3.5 x 3.5 cm, a constant contact force being ensured by placing a 4 kg weight on the TEFLON mounting ; and the surface resistance was then directly measured using a Fluke-77 III Multimeter.

The optical density of the conductive layers was determined in transmission using a MacBeth TD924 densitometer with a visible filter for conductive layers without photographic treatment, in pattern type (d) in which no silver was developed and in pattern (a) in which silver was developed over the whole 3 cm x 3 cm area without deducting the density of the support. The surface resistances and optical densities (complete material) after exposure and development according to the patterns shown in Figure 1 are given in Table 1.

Table 1: Control Description Pattern used from Fig 1 trans-Surface materials type description mission resistance O. D. [Q/square] B Without any--0. 09 500 photographic treatment B After transfer reaction a Solid area 2. 30 5.2 B After transfer reaction b 1 mm lines, 0.33* 37 10 mm spacing B After transfer reaction c 150 urn lines, 0.19* 165 5 mm spacing B After transfer reaction d No Ag developed 0.07 800 C Without any-0. 10 650 photographic treatment C After transfer reaction a Solid area 2. 50 2.3 C After transfer reaction b 1 mm lines, 0. 35* 18 10 mm spacing C After transfer reaction c 150 urn lines, 0.20* 120 5 mm spacing C After transfer reaction d No Ag developed 0.09 750

* calculated values EXAMPLE 2 (INVENTION) Preparation of the palladium sulphide dispersion: The preparation of the physical development nuclei (PdS) is described in the example of EP-A 0769 723. From this example solutions Al, B1 and Cl were used to prepare the nuclei.

Preparation of Material D: 100 g of the above-described PEDOT/PSS dispersion was mixed with 3.35 g of the PdS-dispersion. To this mixture, 1.25 g of a 10 g/L water solution of AEROSOL OT (American Cyanamid), 0.625 g of a 50 g/1 solution of perfluorcaprylamidpolyglycol and 61.9 ml of water were added to give the coating dispersion. This dispersion was coated on a support consisting of a poly (ethylene terephthalate) film and a 4 m thick gelatin subbing layer to a wet-layer thickness of 50 um with a doctor blade and then dried for 15 minutes at 100°C to produce Material D.

Preparation of the transfer emulsion layer: The preparation of the silver chlorobromide emulsion and the preparation of the transfer emulsion layer was as disclosed in EP-A 769 723 except that the coverage of silver halide applied was equivalent to 1.25 g/m2 of AgNO3 instead of 2 g/m2 thereof. exposure and development The transfer emulsion layer was exposed image-wise as shown in Figure 1 and processed in contact with the receiver at 25°C for 10s with an AGFA-GEVAERT CP297 developer solution. evaluation Surface resistance and optical density measurements were carried out as described above for COMPARATIVE EXAMPLE 1 and the results are given in Table 2.

Comparing Tables 1 and 2, it is surprising that the surface resistances and optical densities determined with the single layer composite material of the present invention of Material D are fully comparable with the two layer configuration of Material B with the same components produced using the same techniques and exhibited higher visible light transmission than the two layer configuration of Material C in which the PEDOT/PSS-layer was coated on a non- continuous developed silver layer.

The embedding of the developed silver in the PEDOT/PSS-layer results is a greater flatness of the outermost surface of the single layer compared with the two layer configuration.

From Table 2 it can be concluded that (1) it is possible to expose the PEDOT/PSS layer to the AGFA-GEVAERT CP297 developer with minor loss in surface conductivity without affecting the optical transparency and (2) the silver-lines increase the "apparent"surface conductivity significantly as is the case with two layer configurations with the same components indicating that the embedded developed silver forms of itself a conductive entity.

Table 2: Invention Description Pattern used from Fig 1 trans-Surface material type description mission resistance O. D. [Q/square] D Without any--0. 11 340 photographic treatment D After transfer a Solid area 2.04 7.2 reaction D After transfer b 1 mm lines, 0. 28* 40 reaction 10 mm spacing D After transfer c 150 pm lines, 0.16* 140 reaction 5 mm spacing D After transfer d No Ag deposit 0.10 530 reaction

* calculated value EXAMPLE 3 (INVENTION) Conceptual experiments were carried out with a recorder film with a gelatine to silver ratio of 0.014. Exposed areas of 1 x 3 cm2as electrodes with a separation of 40 Jim gave conducting silver patterns upon processing by conventional graphic processing. The resulting electrode pattern had a surface resistance of 50 to 100 ohm/square.

These electrodes were conditioned for 3 days at 35°C and a relative humidity of 80%. The aqueous solutions used for treating the electrodes prior to applying a potential of 100 V between neighbouring electrodes are listed in Table 3.

Table 3: Solution Solution nr. active ingredient conc. (%] solvent 1 3777150 STAB01 (1-phenyl-5-mercapto-tetrazole) 1.0 water* 2 3777151 STAB01 0. 1 water* 3 3777152 STAB01 + AntarotM CO 630# 1. 0 + 0.5 water 4 3777153 STAB01 + Antaro'M CO 630# 0. 1 + 0.5 water 5 3777154 STAB02 (sodium tartrate) 10 water 6 3777155 STAB02 (sodium tartrate) 1 water 7 3777156 STAB03 (thiourea) 10 water 8 3777157 STAB03 (thiourea) 1 water 9 3777158 STAB04 (sodium sulphide) 10 water 10 3777159 STAB04 (sodium sulphide) 1 water 11 3777166 STAB05 (5-methyl-s-triazolo [1, 5- 4. 25 water a] pyrimidin-7-ol) 12 3777167 STAB05 0. 425 water 13 3777168 STAB05 1. 7 x 10-2 water 14 3777169 STAB05 1. 7 x 10-4 water 15 3777170 STAB05 1. 7 x 10-5 water 16 3777171 STAB05 1. 7 x 10-6 water 17 3780150 STAB06 0. 5 water 18 3780151 STAB06 0. 05 water 19 3780152 STAB06 0. 005 water 20 3780153 STAB07 0. 5 water 21 3780154 STAB07 0. 05 water 22 3780155 STAB07 0. 005 water 23 3780156 STAB08 0. 5 water 24 3780157 STAB08 0. 05 water 25 3780158 STAB08 0. 005 water 26 3780159 STAB09 0. 5 water 27 3780160 STAB09 0. 05 water 28 3780161 STAB09 0. 005 water 29 3777161 PMT01 0. 1 ethanol 30 3777172 PMT01 0. 004 ethanol 31 3777173 PMT01 4 x 105 ethanol 32 3777174 PMT10 4 x 10-6 ethanol 33 3780162 PMT02 0. 5 water 34 3780163 PMT02 0.05 water 35 3780164 PMT02 0. 005 water 36 3780165 PMT03 0. 5 water 37 3780166 PMT03 0. 05 water 38 3780167 PMT03 0. 005 water 39 3780168 PMT04 0. 5 ethanol 40 3780169 PMT04 0. 05 ethanol 41 3780170 PMT04 0. 005 ethanol 42 3780171 PMT05 0. 5 water 43 3780172 PMT05 0. 05 water 44 3780173 PMT05 0. 005 water 45 3780175 PMT06 0. 05 water 46 3780176 PMT06 0. 005 water 47 3780178 PMT07 0. 05 water 48 3780179 PMT07 0. 005 water 49 3780180 PMT08 0. 5 water 50 3780181 PMT08 0. 05 water 51 3780182 PMT08 0. 005 water 52 3780183 PMT09 0. 5 water 53 3780184 PMT09 0. 05 water 54 3780185 PMT09 0. 005 water 55 3780187 PMT10 0. 5 water 56 3780188 PMT10 0. 05 water 57 3780190 PMT11 0. 05 water 58 3780191 PMT11 0. 005 water 59 3780193 PMT12 0. 05 water 60 3780194 PMT12 0. 005 water 61 3780196 PMT13 0. 05 water 62 3780197 PMT13 0. 005 water 63 3780199 PMT14 0. 05 water 64 3780200 PMT14 0. 005 water

# a nonyl-phenyl-oxy-polyethyleneglycol (EO 9.5), from GAF After treatment of the electrodes by dipping in the solution for 1 minute at 25°C, a potential of 100 V was applied between neighbouring electrodes for 20 minutes. The result was viewed under a microscope and recorded photographically. The gap between the electrodes without pretreatment and before applying a potential was determined to be 43.0 0.7 jim. Tables 4 and 5 record the final gap width and general observations concerning silver dendrite formation after particular pretreatments and the subsequent application of a potential of 100 V for 20 minutes for the comparative experiments with STAB01 to STAB09 and for the invention experiments with PMT01 to PMT14 respectively.

Table 4: Compar-sol-result of applying 100 V for 20 min. between electrodes ative ution final observations exper-nr. width of iment nr. gap [Um] 1# 3777165 none 25.8 1.0 front formation 2* 3777164 none 28.3 1. 0 front formation 3* 3780201 none 43.1 1. 2 dendrites, but no front formation 4 3777150 1 23.6 1. 8 front formation 5 3777151 2 21.5 2. 5 front formation 6 3777152 3 25.5 2. 9 front formation 7 3777153 4 41.8 0. 7 dendrite formation 8 3777154 5 35.5 1. 3 front formation but loss of electrode contact 9 3777155 6 33.6 1. 7 front formation 10 3777156 7 27.8 1. 9 front formation 11 3777157 8 26.2 ~ 2. 9 front formation 12 3777158 9 22.1 ~ 4. 1 front formation but loss of electrode contact 13 3777159 10 27.8 2. 7front formation 14 3777166 11 30.4 1.7 front formation 15 3777167 12 26.0 1. 2 front formation 16 3777168 13 21.8 2.0 zones with front formation/ zones with dendrites but no front formation 17 3777169 14 23.5 3.1 zones with front formation/ 43.8 0.7 zones with dendrites but no front formation 18 3777170 15 25.7 2.1 zones with front formation/ 42.4 1.0 zones with dendrites but no front formation 19 3777171 16 22.6 ~ 2. 3 zones with front formation/ zones with dendrites but no front formation 20 3780150 17 28.6 0. 6 front formation 21 3780151 18 26.7 0. 6 front formation 22 3780152 19 43.2 ~ 0. 6 dendrites, but no front formation 23 3780153 20 23.4 0.9 front formation 24 3780154 21 24.9 1.1 front formation 25 3780155 22 24.6 0.6 front formation 26 3780156 23 32.2 2. 3front formation 27 3780157 24 43.3 0.6 dendrites, but no front formation 28 3780158 25 42.4 1.8 dendrites, but no front formation 29 3780159 26 42.7 1. 7 dendrites, but no front formation 30 3780160 27 43.1 1.0 occasional dendrites 31 3780161 28 43.0 0.4 occasional dendrites

# neither conditioning nor solution pretreatment prior to application of 100 V DC * no solution pretreatment between conditioning and application of 100 V DC Table 5: Invention sol-result of applying 100 V for 20 min. between electrodes exper-ution final width observations iment nr. nr. of gap [µm] 1 3777161 29 41.9 0.7 almost no dendrite formation 2 3777172 30 42.4 ~ 0. 7 almost no dendrite formation 3 3777173 31 41.5 0. 4 almost no dendrite formation 4 3777174 32 41.4 1. 1 occasional dendrites 5 3780162 33 29.8 0. 4 front formation 6 3780163 34 29'. 4 1.4 front formation 7 3780164 35 43. 1 0.3 dendrites, but no front formation 8 3780165 36 42.9 0. 4 occasional dendrites 9 3780166 37 42.6 0. 7 occasional dendrites 10 3780167 38 43.3 0. 75 dendrites, but no front formation 11 3780168 39 42.4 0. 8 almost no dendrite formation 12 3780169 40 43.4 0. 7 occasional dendrites 13 3780170 41 42. 4 ~ 1. 0 dendrites, but no front formation 14 3780171 42 43.9 0. 8 dendrites, but no front formation 15 3780172 43 43.8 0. 6 almost no dendrite formation 16 3780173 44 44.2 ~ 0. 4 almost no dendrite formation 17 3780175 45 42.9 ~ 0. 7 dendrites, but no front formation 18 3780176 46 43.4 0. 7 almost no dendrite formation 19 3780178 47 43.5 1.0 occasional dendrites 20 3780179 48 43.2 0.9 occasional dendrites 21 3780180 49 25.4 2.3 front formation 22 3780181 50 43.4 0.8 occasional dendrites 23 3780182 51 43.7 0.4 almost no dendrite formation 24 3780183 52 43.3 ~ 0. 7 dendrites, but no front formation 25 3780184 53 42.0 ~ 0. 8 occasional dendrites 26 3780185 54 43.9 ~ 0. 5 almost no dendrite formation 27 3780187 55 24.1 ~ 4. 0 front formation 28 3780188 56 42.9 ~ 0. 9 dendrites, but no front formation 29 3780190 57 25.6 ~ 3. 3 front formation 30 3780191 58 43.0 ~ 0. 5 occasional dendrites 31 3780193 59 23.4 3.0 front formation 32 3780194 60 42.8 0.4 almost no dendrite formation 33 3780196 61 42.2 0.6 occasional dendrites 34 3780197 62 41.9 1.2 occasional dendrites 35 3780199 63 26.1 2.1 front formation 36 3780200 64 41.6 1. 1 occasional dendrites

These results show migration of silver ions upon conditioning for 3 days at 35°C and 80% relative humidity and subsequent

application of a potential of 100 V DC for 20 minutes in the absence of pretreatment (comparative experiments 2 and 3). A comparison of the results with comparative experiments 1 and 2 show that conditioning clearly promoted silver dendrite growth as observed in actual devices.

Pretreatment with an aqueous solution of sodium tartrate (STAB02) provided limited restraint as shown by the reduced growth of the silver dendrite front. Pretreatment with high concentrations of sodium sulphide (STAB04) appeared to detach the silver dendrite front from the electrode. Low concentrations of 5- methyl-s-triazolo [1, 5-a] pyrimidin-7-ol (STAB05) also restrained silver dendrite growth as evidenced by the break up of the silver dendrite front into clusters of silver dendrites although this was limited to particular zones.

All the 5-mercapto-tetrazoles investigated, with the notable exception of unsubstituted 1-phenyl-5-mercapto-tetrazole [STAB01], also exerted at least a limited restraint on the silver dendrite- formation process as could be seen by at least the appearance of a broken front formed by clusters of silver-dendrites. 1-phenyl-5- mercapto-tetrazole itself exhibited this behaviour in the presence of the surfactant Antaro) Jm CO 630, a non-ionic surfactant.

However, substantial restraint was only observed with 1-phenyl- mercapto-tetrazole compounds with the phenyl group substituted with at least one electron accepting group such as halide, acylamino or amido groups as shown by the compounds PMT01 to PMT14. Almost complete restraint was observed upon pretreatment with solutions 29,30, 31,39, 43,44, 46,51, 54 and 60 i. e. with PMT1, PMT05, PMT06, PMT08, PMT09 and PMT12 almost complete restraint was observed at concentrations of 1-phenyl-5-mercapto-tetrazole with phenyl groups substituted with electron accepting groups of 0. 005% : or lower.

The present invention may include any feature or combination of features disclosed herein either implicitly or explicitly or any generalisation thereof irrespective of whether it relates to the presently claimed invention. In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention.