Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/66—Electroplating: Baths therefor from melts
  • C25D3/665—Electroplating: Baths therefor from melts from ionic liquids
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/54—Electroplating: Baths therefor from solutions of metals not provided for in groups C25D3/04 - C25D3/50

Definitions

• the invention relates to a process for the electrochemical deposition of selenium on a substrate in an ionic liquid.
• Selenium has a number of properties that make it suitable for many applications in photovoltaics and electronics.
• Selenium is a photosemiconductor that changes its conductivity by several orders of magnitude when exposed to visible light (magnified).
• selenium is transparent to wavelengths greater than 650 nm.
• selenium is used as a constituent in thin-film solar cells in combination with Cu and indium, as described, for example, in DE 44 47 866 or in DE 199 177 58.
• all layer components are deposited by evaporation or only copper or indium are applied by electroplating.
• the selenium is preferably applied in both cases via the gas phase in an evaporator.
• Electrolysis of selenium describes US 2,414,438.
• the deposition takes place in aqueous alkaline solutions of ammonium, alkali metal or Erdalkalimetallseleniden.
• the deposition is difficult, however, since in the room temperature range usually amorphous or glassy red selenium is deposited, which has a poor electron conductivity. Only at higher temperatures is a gray, metallic phase separated, but the deposits do not exist even at temperatures around 100 0 C singular gray selenium. Higher temperatures, which would promote the deposition of gray selenium, are excluded in open galvanic baths. However, the electrochemical deposition would allow continuous operation in the form of a Badgalvanik without closed evaporator or sputtering facilities.
• the object is achieved by the method according to the invention.
• the invention relates to a process for the electrochemical deposition of gray selenium on a substrate in at least one ionic liquid.
• the deposition of gray selenium takes place on a wide variety of substrates in a wide variety of applications.
• the deposition may serve solely for the deposition of selenium, but it may also be used in connection with the deposition of other materials, e.g. Copper or indium can be used.
• ionic liquids which are suitable for the process according to the invention are highly conductive and as a rule thermally stable up to 400 ° C.
• ionic liquids are used which are electrochemically stable under the deposition conditions described below.
• you have an electrochemical window in the cathodic branch which ranges from 0 mV to -3500 mV against ferrocene / ferrocinium, preferably from -2000 mV to -3000 mV against ferrocene / ferrocinium.
• suitable ionic liquids have an electrochemical window ranging from 0 mV to +3500 mv against ferrocene / ferrocinium, preferably from +2000 to +3000 mV against ferrocene / ferrocinium.
• the information refers to the measuring arrangements and conditions given below.
• Suitable ionic liquids contain in particular at least one tetraalkylammonium, tetraalkylphosphonium cation, wherein the
• Alkyl groups each independently of one another may have 1 to 10 carbon atoms, or a heterocyclic cation selected from
• R 1 'to R 4 ' are each independently hydrogen, -CN, -OR ', -NR' 2> -P (O) R ' 2 , -P (O) (NR ⁇ ) 2 , -C (O) R 1 , straight-chain or branched alkyl having 1-20 C atoms, straight-chain or branched alkenyl having 2-20 C atoms and one or more double bonds, straight-chain or branched alkynyl having 2-20 C atoms and one or more triple bonds, saturated, partially or fully unsaturated cycloalkyl having 3-7 C atoms, which may be substituted by alkyl groups having 1-6 C atoms, saturated, partially or fully unsaturated heteroaryl, heteroaryl-C r C 6 alkyl or aryl-CrC ⁇ -alkyl where the substituents R 1 ', R 2 ', R 3 'and / or R 4 ' together can also form a ring system, wherein one or more
• R 2 'or R 3 ' is, in each case independently of one another, in particular hydrogen, methyl, ethyl, isopropyl, propyl, butyl, sec-butyl, tert-butyl, cyclohexyl, phenyl or benzyl.
• R 2 ' is particularly preferably hydrogen, methyl, ethyl, isopropyl, propyl, butyl or sec-butyl.
• R 2 'and R 3 ' are hydrogen.
• the C 1 -C 12 -alkyl group is, for example, methyl, ethyl, isopropyl, propyl, butyl, sec-butyl or tert-butyl, and also pentyl, 1-, 2- or 3-methylbutyl, 1, 1, 1, 2- or 2,2-dimethylpropyl, 1-ethyl propyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl or dodecyl.
• a straight-chain or branched alkenyl having 2 to 20 C atoms, wherein several double bonds may also be present, is, for example, allyl, 2- or 3-butenyl, isobutenyl, sec-butenyl, furthermore 4-pentenyl, isopentenyl, hexenyl, Heptenyl, octenyl, -CgHi 7 , -Ci 0 Hi 9 to -C 2 oH 39 ; preferably allyl, 2- or 3-butenyl, isobutenyl, sec-butenyl, furthermore preferred is 4-pentenyl, iso-pentenyl or hexenyl.
• a straight-chain or branched alkynyl having 2 to 20 C atoms, wherein a plurality of triple bonds may also be present, is, for example, ethynyl, 1- or 2-propynyl, 2- or 3-butynyl, furthermore 4-pentynyl, 3-pentynyl, hexynyl, Heptynyl, octynyl, -C 9 Hi 5 , -C 10 H 17 to -C 20 H 37 , preferably ethynyl, 1- or 2-propynyl, 2- or 3-butynyl, 4-pentynyl, 3
• Pentynyl or hexynyl Pentynyl or hexynyl.
• Aryl-C 1 -C 6 -alkyl is, for example, benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl or phenylhexyl, where both the phenyl ring and the alkylene chain, as described above, partially or completely with halogens, in particular -F and / or -Cl, or partially with -OR ', -CN, -C (O) OH, -C (O) NR' 2 , -SO 2 NR 1 S , -C (O) X, -SO 2 OH, -SO 2 X, -NO 2 may be substituted.
• Cycloalkyl groups having 3-7 C atoms are therefore cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclopentenyl, cyclopenta-1, 3-dienyl, cyclohexenyl, cyclohexa-1,3-dienyl, cyclohexa-1,4-dienyl, phenyl, Cycloheptenyl, cyclohepta-1, 3-dienyl, cyclohepta-1, 4-dienyl or cyclohepta-1, 5-dienyl, which may be substituted with Cr to C 6 alkyl groups, in turn, the cycloalkyl group or with Cr to Ce- alkyl groups substituted cycloalkyl group with halogen atoms such as F, Cl, Br or I, in particular F or Cl or with -OR ', -CN, -C (O) OH,
• examples are so modified
• R ' C 3 - to C 7 -cycloalkyl, for example cyclopropyl, cyclobutyl,
• substituted phenyl by Cr to C 6 alkyl, is C to C 6 alkenyl, NO 2 , F, Cl, Br, I, C r C 6 alkoxy, SCF 3 , SO 2 CF 3 , COOH , SO 2 X 1 , SO 2 NR " 2 or SO 3 H-substituted phenyl, where X 'is F, Cl or Br and R" is a non, partially or perfluorinated C r to C 6 -alkyl or C 3 - to C 7 - Cycloalkyl as defined for R 1 , for example, o-, m- or p-methylphenyl, o-, m- or p-ethylphenyl, o-, m- or p-propylphenyl, o-, m- or p-isopropylphenyl, o-, m- or p-tert-butylphenyl, o-
• R 1 'to R 4 ' is understood as a heteroaryl saturated or unsaturated mono- or bicyclic heterocyclic radical having 5 to 13 ring members, where 1, 2 or 3 N and / or 1 or 2 S or O atoms may be present and the heterocyclic radical is mono- or polysubstituted by Cr to Ce-alkyl, C 1 to C 6 -alkenyl, NO 2 , F, Cl, Br, I, C 1 -C 6 -alkoxy, 1 SCF 3 ,
• SO 2 CF 3 COOH, SO 2 X ', SO 2 NR " 2 or SO 3 H may be substituted, wherein X' and R" have the meaning given above.
• the heterocyclic radical is preferably substituted or unsubstituted 2- or 3-furyl, 2- or 3-thienyl, 1-, 2- or 3-pyrrolyl, 1-, 2-, 4- or 5-imidazolyl, 3-, 4- or 5-pyrazolyl, 2-, 4- or 5-oxazolyl, 3-, 4- or 5-isoxazolyl, 2-, 4- or 5-thiazolyl, 3-, 4- or 5-isothiazolyl, 2-, 3- or 4-pyridyl, 2-, 4-, 5- or 6-pyrimidinyl, furthermore preferably 1, 2,3-triazole-1, -4- or -5-yl, 1, 2,4-triazole-1 , -4- or -5-yl, 1- or 5-tetrazolyl, 1, 2,3-oxadiazol-4 or -5-yl 1, 2,4-ox
• heteroaryl-C 1 -C 6 -alkyl by analogy with aryl-C 1 -C 6 -alkyl, pyridinyl-methyl, pyridinyl-ethyl, pyridinyl-propyl, pyridinyl-butyl, pyridinyl-pentyl, pyridinyl-hexyl is now understood, in which case the previously described heterocycles can be linked in this way with the alkylene chain.
• R 1 'to R 4 ' are in particular alkyl groups having 1 to 10 C atoms or hydroxyalkyl groups having 1 to 10 C atoms.
• Particularly suitable ionic liquids include
• alkyl group having 1 to 10 carbon atoms is meant, for example, methyl, ethyl, isopropyl, propyl, butyl, sec-butyl or tert-butyl, and also pentyl, 1-, 2- or 3-methylbutyl, 1, 1 -, 1, 2- or 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, heptyl, octyl, nonyl or decyl.
• the alkyl groups may also be partially or completely substituted by fluorine.
• Fluorinated alkyl groups are, for example, difluoromethyl, trifluoromethyl, pentafluoroethyl, pentafluoropropyl, heptafluoropropyl, heptafluorobutyl or nonafluorobutyl.
• a hydroxyalkyl group having 1 to 10 carbon atoms is meant, for example, 1-hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, and also 5-hydroxypentyl, 6-hydroxyhexyl, 7-hydroxyheptyl, 8-hydroxyoctyl, 9-hydroxynonyl or 10-hydroxydecyl.
• the alkylene chain of the hydroxy group can also be partially or completely substituted by fluorine.
• Fluorinated hydroxyalkyl groups can be described, for example, by the subformula - (CHF) n -OH or - (CF 2 ) n -OH, where n can denote 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.
• Suitable anions which, in combination with the cations according to the invention, fulfill the aforementioned condition with regard to stability, may be selected from the group PF 6 , BF 4 , alkylsulfate, perfluoroalkylsulfonate, perfluoroacetate, bis (fluorosulfonyl) imide, bis (perfluoroalkylsulfonyl) imide, tris (perfluoroalkyl) trifluorophosphate, bis (perfluoroalkyl) tetrafluorophosphate, tris (perfluoroalkylsulfonyl) methide or perfluoroalkylborate.
• perfluoroalkyl group means that all H atoms of the corresponding alkyl group are replaced by F atoms.
• the alkyl or perfluoroalkyl groups in the indicated anions in each case independently of one another have 1 to 10 C atoms, more preferably 1, 2, 3 or 4 C atoms.
• Anions which are suitable according to the invention can be selected, for example, from the group trifluoromethylsulfonate, pentafluoroethylsulfonate, heptafluoropropylsulfonate, nonafluorobutylsulfonate, bis (fluorosulfonyl) imide, perfluoroacetate, bis (trifluoromethylsulfonyl) imide, bis (pentafluoroethylsulfonyl) imide, bis (heptafluoropropylsulfonyl) imide, bis ( nonafluorobutylsulfonyl) imide, tris (trifluoromethylsulfonyl) methide, tris (pentafluoroethylsulfonyl) methide ) tris (heptafluoropropylsulfonyl) methide, tris (nonafluorobut
• perfluoroalkyl groups may independently of one another denote different perfluoroalkyl groups.
• the above definition therefore also includes, for example, mixed anions such as trifluoromethylsulfonyl pentafluoroethylsulfonylimide, bis (trifluoromethyl) sulfonylpentafluoroethylsulfonylmethide.
• the anions of the group trifluoromethanesulfonate, bis (trifluoromethylsulfonyl) imide or tris (pentafluoroethyl) trifluorophosphate are particularly preferably selected.
• Suitable cations are, in particular, optionally linear or branched, tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, tetrapentylammonium, tetrahexylammonium, tetraheptylammonium, tetraoctylammonium, tetranonylammonium, tetradecylammonium, trimethylalkylammonium, trimethyl (ethyl) ammonium, triethyl (methyl) ammonium, trihexylammonium, methyl (trioctyl) ammonium, tetramethylphosphonium, tetraethylphosphonium, tetrapropylphosphonium, tetrabutylphosphonium, tetrapentylphosphonium, tetrahexylphosphonium,
• Particularly suitable cations are tetramethylammonium, trimethylalkylammonium, it being possible for the alkyl group to have 1 to 10 C atoms, in particular trihexyltetradecylphosphonium, triisobutyl (methyl) phosphonium, tributyl (ethyl) phosphonium, tributyl (methyl) phosphonium, moreover preferably 1 Butyl-1-methylpyrrolidinium, 1-butyl-1-ethylpyrrolidinium, 1-hexyl-1-methylpyrrolidinium, 1-methyl-1-octylpyrrolidinium or 1- (2-hydroxyethyl) -3-methyl-imidazolium, are particularly suitable cations 1-butyl-1-methylpyrrolidinium, 1-hexyl-1-methylpyrrolidinium, 1-methyl-1-octylpyrrolidinium or 1- (2-hydroxyethyl) -3-methyl-imidazolium.
• Particularly suitable ionic liquids for use in the process according to the invention are 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide, 1-butyl-1-methylpyrrolidinium tris (pentafluoroethyl) trifluorophosphate, 1-hexyl -1-methylpyrrolidinium trifluoromethanesulfonate,
• selenium ions are dissolved in a suitable ionic liquid as described above.
• Suitable selenium salts are, for example, selenetetrahalides, e.g. Selenium tetrachloride or selenetetrabromide, but also selenium dioxide. In principle, any selenium salt is suitable that allows a selenium deposition under the conditions mentioned.
• the ion concentration in the ionic liquid to the metal deposition is preferably from 10 "5 to 10 mol / l. Preferably, with an ionic concentration of 10" worked 3 to 10 "1 mole / l.
• the deposition according to the invention takes place in a protective gas atmosphere, for example under argon, the oxygen and water content and in particular the water content should be below 1 ppm.
• the deposition is carried out in a 3-electrode cell as known to those skilled in the art (for example, AJ Bard, LR Faulkner, Electrochemical Methods, Wiley).
• a 3-electrode cell as known to those skilled in the art (for example, AJ Bard, LR Faulkner, Electrochemical Methods, Wiley).
• platinum or selenium electrodes as counter and reference electrodes.
• all metals or carbon can be used as electrode materials, as long as the products formed at the counter electrode, the processes at the Do not disturb the working electrode, ie as long as the electrode materials are not deposited together with selenium under the experimental conditions.
• the selection of suitable materials is carried out within the scope of the skilled person.
• the inventive method is preferably carried out potentiostatically, at electrode potentials between 0 and -2000 mV and at temperatures between 1O 0 C and 23O 0 C, preferably between 100 0 C to 150 ° C. 0
• the method according to the invention can also be carried out by means of pulsed techniques, as known to the person skilled in the art, for example as described in J.-C. Puippe, F. Leaman, Pulse-Plating: Electrolytic Metal Deposition with Pulsed Current, Eugen G. Leuze Verlag,
• gray selenium can be used in any layer thicknesses, e.g. be deposited between 200 .mu.m and 300 .mu.m in micro- or nanocrystalline opaque layers.
• the desired layer thickness is controlled via the electrode potential and the flowed charge as well as the electrochemical parameters.
• F Faraday constant
• A area
• p density of the metal
• I current
• Figure 1 shows a cyclic voltammogram of an approximately 0.1 molar solution of SeCl 4 in 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide (BMP Tf 2 N) at room temperature on Au (111).
• BMP Tf 2 N 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide
• +0.5 volt shows an oxidation process, wherein the ratio of the flowed anodic to the cathodic currents is significantly less than 1.
• Figure 3 shows the morphology of selenium deposits deposited at 15O 0 C from SeCU in BMP Tf2N.
• XRD X-ray diffraction, cobalt K alpha as X-ray
• Suitable substrates are for example selectable from all categories, for example non-metals, semi-metals, metals, metal alloys, conductive or metallized ceramics or conductive or metallized plastics are possible.
• a preferred nonmetal is, for example, graphite.
• a preferred semi-metal is, for example, silicon.
• Preferred metals are, for example, gold, platinum, copper, iron, cobalt, nickel or molybdenum.
• Preferred metal alloys are, for example, a wide variety of steels or nickel alloys.
• suitable substrates may already already consist of several layers onto which a further layer as an intermediate layer or final layer of selenium is applied by the process according to the invention. The enumeration of the substrates is therefore in no way to be construed as limiting. The person skilled in the respective field of application can make the selection of the suitable substrate without further information.
• the ionic liquid can be washed out with organic solvents.
• organic solvents are, for example, toluene, benzene, methylene chloride,
• Acetonitrile, acetone, methanol, ethanol or isopropanol When using selenium tetrachloride, this can be removed, for example, by heating in vacuo by distillation from the ionic liquid.
• substrates which are coated by the method according to the invention.
• ionic liquids for deposition, preferably for electrochemical deposition, of gray selenium on a substrate is another object of the present invention.
• Example 1 Deposition of Selenium from SeCl4_to Gold
• a solution of SeCU in the ionic liquid 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide is prepared and transferred under protective gas atmosphere at room temperature in the 3-Elektrodenmeßzelle.
• a typical 3-electrode measuring cell was used, as described, for example, in AJ. Bard and L.R. Faulkner, Electrochemical Methods, Wiley.
• the 3-electrode measuring cell has a gold electrode as the working electrode (cathode) and platinum wires serve as quasi-reference and counter-electrode.
• the electrode potential is at -1500 mV vs. Platinum quasi-reference set.
• the deposition of selenium begins at -1000 mV.
• Example 2 Separation of Selenium from Seq / j on Platinum Analogously to Example 1, a 0.25 molar solution of SeBr 4 in the ionic liquid 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide is prepared and under protective gas atmosphere transferred at room temperature in the 3-Elektrodenmeßzelle.
• a typical 3-electrode measuring cell was used, as described, for example, in AJ. Bard and LR Faulkner, Electrochemical Methods, Wiley.
• the 3-electrode measuring cell has as a working electrode (cathode) a platinum electrode and platinum wires serve as quasi-reference and
• the electrode potential is at -1500 mV vs. Platinum quasi-reference set.
• the deposition of selenium begins at -1000 mV.
• Example 3 Separation of Selenium from SeBu on Indium Analogously to Example 1, a 0.25 molar solution of SeBr 4 in the ionic liquid 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide is prepared and incubated in a protective gas atmosphere at room temperature in the Transferred electrode measuring cell.
• a typical 3-electrode measuring cell was used, as described, for example, in AJ. Bard and LR Faulkner, Electrochemical Methods, Wiley.
• the 3-electrode measuring cell has an indium electrode as the working electrode (cathode) and platinum wires serve as a quasi-reference and counterelectrode.
• the electrode potential is at -1500 mV vs. Platinum quasi-reference set.
• the deposition of selenium begins at -1000 mV.

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