GB2531809A

GB2531809A - Light emitting structures and devices

Info

Publication number: GB2531809A
Application number: GB1419538.2A
Authority: GB
Inventors: Ping Lai Chung
Original assignee: GRAPHENE LIGHTING PLC
Current assignee: GRAPHENE LIGHTING PLC
Priority date: 2014-11-03
Filing date: 2014-11-03
Publication date: 2016-05-04
Also published as: GB201419538D0

Abstract

A light emitting structure comprising a substrate 1, a system of wires and at least one LED 6. The wires comprise a laminate of copper sheet and a graphene layer 5 and each wire is in electrical contact with the LED to form an electrical circuit. The substrate may be transparent. The copper layer may also contain another metal, such as nickel and the graphene layer may be a mono-layer of graphene. The device may be constructed such that it does not have a heat sink. The device may comprise more than one LED and these extra LEDs may be arranged in series. The copper graphene laminate wires have improved thermal conduction in comparison with copper wires. The graphene layer may be patterned onto the copper sheet.

Description

Light Emitting Structures and Devices [0001] This invention relates to light emitting structures and to light emitting devices comprising said structures. The light emitting structures comprise copper, graphene and LEDs. They are more energy efficient, cheaper to manufacture and generate less heat than existing LED lighting systems. The invention also relates to a process of making the light emitting structures.

BACKGROUND

[0002] LED light bulbs are bulbs which include a number of light-emitting diodes (LEDs).

LED bulbs have a lifespan and electrical efficiency that is several times better than more traditional incandescent lamps, and significantly better than most fluorescent lamps, with some LED chips able to emit more than 100 lumens per watt. LEDs themselves are highly efficient emitting far more light than even fluorescent tubes or incandescent lamps. This is in part because LED bulbs do not generate as much heat as incandescent bulbs.

However, LED bulbs do still generate heat. This heat generation means that most LED bulbs include a heat sink, typically made of aluminium, to disperse the heat away from the LEDs. Even so, LED bulbs typically operate at energy efficiencies lower than the maximum capability of the LEDs themselves. This deficiency is due In part to the inefficient dispersal of heat away from the LEDs. The longevity of LED bulbs is likewise less than it could be based on the longevity of the LEDs themselves and this again, in part arises due to the lack of an efficient means by which to disperse the heat away from the LEDs.

[0003] It is an aim of certain embodiments of this invention to provide an LED based device which is more energy efficient than known devices, i.e. which can generate the same amount of light using lower amounts of energy.

[0004] It is an aim of certain embodiments of this invention to provide an LED based light emitting device which produces relatively less heat than known devices.

[0005] It is an aim of certain embodiments of this invention to provide an LED based light emitting device which is cheaper to produce than known devices.

[0006] It is an aim of certain embodiments of this invention to provide an LED based light emitting device which has improved longevity relative to known devices.

[0007] Certain embodiments of the invention achieve some or all of the above aims.

BRIEF SUMMARY OF THE DISCLOSURE

[0008] In a first aspect of the present invention there is provided a light emitting structure cornprising.

a substrate; a system of wires; and at least one LED; wherein each wire comprises a laminate structure comprising a copper layer and a graphene layer; and wherein each wire is in electrical contact with at least one LED and the system of wires and at least one LED together form an electrical circuit.

[0009] The light emitting structures of the invention may, for example, replace the filament of a traditional light bulb. To resemble the filament, copper or nickel or metal composite conduction paths were plated, evaporated, sputtered or glued on the substrates. Substrates can be made of any transparent materials namely sapphire, glasses, quartz, PET, and other possible materials. The metal conductive paths can be laid in any lenght and any shape but preferably in rectangular shape. The conductive layer can be from singular metal such as copper and nickel or metal composite. The metal composite can consist of copper, nickel,and aluminium. More preferably the layer structure of metal composite is made of copper/nickel or aluminium nickel. The conductive layer is patterned so as to make the discrete islands. The LED which will be bonded on the top of the isolated island to for series connection.

[0010] A graphene layer is grown on the top of patterned copper or nickel depending on applications. Owning to the nucleation selectivity, Graphene can only grown on copper and nickel surfaces. Therefore, the patterned copper/nickel surface will grow grpahene. However, etched surface area which does not consist of copper or nickel will not be coated with Graphene. This proprietary distinctive selectivity helps to ensure the Graphene can be grown in the necessary heat/electric conductive area without being placed in the insulation surface. After Graphene is placed on the top of the conducting wire, LED can be placed using traditional die bonding or wire bonding techniques on these conductive surfaces to form filaments. The LED is preferably been connected in series.

However, we can use two parallel series to increase the illumination intensity for certain applications.

[0011] The graphene layer and the process of forming the graphene layer increase the heat conduction of the copper layer by up to 20%. See 'Thermal Properties of GrapheneCopper-Graphene Heterogenous Films'; Goli et al.; Nana Lett., 2014, 14 (3), pp 1497- 1503; which shows that a layer of copper encapsulated by a layer of graphene on either side shows an increase of heat conduction of up to 24%. The inventors have surprisingly found that the copper layer does not need to be encapsulated with graphene for this effect to be observed. Indeed, the inventors have found that good heat conduction can be obtained when only one side of the copper is coated with graphene. This is so, even if the other side of the laminate is bound or in contact with a substrate.

[0012] Equally surprisingly, the copper layer can be patterned or etched to form a system of wires (similar to the formation of a printed circuit board) without it losing this improved thermal conductivity. In the light emitting structures of the present invention, the copper/graphene wires therefore act both as electrical conductors to form the electrical circuit which provides electricity to the LEDs, and as thermal conductors which efficiently transport heat away from the LEDs when they are in use. The efficiency of the system in terms of the dispersal of heat is remarkable and allows the LEDs to generate more lumens per Watt than current LED lighting systems. It also provides increased longevity relative to existing LED lighting systems.

[0013] Preferably, the or each LED is in electrical contact with the graphene side of the copper/graphene laminate [0014] The substrate will typically be electrically inert in the sense of being nonconductive in use. The graphene layer may be formed by chemical vapour deposition (CVD) onto the copper layer when the substrate is still in place. It may therefore be that the substrate is capable of withstanding high temperatures. A preferred substrate is glass, e.g. quartz.

[0015] It may be that the substrate is situated on the opposing face of the copper layers to the graphene layer. In other words, it may be that the substrate, the copper layer and the graphene layer and the at least one LED (and optionally phosphor) are stacked sequentially to form a laminate. This is typically the case where the substrate is not flexible.

[0016] The substrate may be flexible, e.g. a flexible polymer. -We make the flexible substrate by using a technology called detachable PCB. PCB is usually made of copper or other metal plated on bakelite resin. Detachable PCB is made of same process but with very weak adhesion between the plated metal with substrates. We intentively make the weak bonding of metal on glass by increasing metal thickness and planting delamination layer so we can deplete the metal wires by tape transfer.

[0017] It may be that the substrate is situated on the opposite side of the at least one LED to the graphene layer. Thus, it may be that the at least one LED (and optionally phosphor) are coated in silicone and that the substrate is situated on the opposite side of the silicone to the at least one LED. Thus, the copper layer and the graphene layer, the at least one LED (and optionally phosphor), the silicone and the substrate are stacked sequentially to form a laminate.

[0018] The inventors have surprisingly found that when a flexible substrate is used in a light emitting structure of the invention, the resulting structure does not significantly lose its beneficial properties. Thus, the light emitting structures of the invention may be flexible.

[0019] There may be an adhesive layer between the copper layers of the wires and the substrate. For solid substrate like copper on glass, we do not use adhesive but very clean surface so metal film with very form short distance Van der Waal force with glass. For flexible substrate, we use heat conductive glue which typically sold in the market.

[0020] The copper layers of the wires may comprise at least one other metal, e.g. one or more transition metals. The copper layers of the wires may comprise another metal that can catalyse the CVD formation of graphene (e.g. nickel). The at least one other metal may be in the form of a coating on the surface of the copper layer which is in contact with the graphene layer, i.e. it may be that there is a layer of at least one of metal between the copper layer and the graphene layer of the wires. Preferably, the at least one other metal is nickel.

[0021] . Preferably, the copper layers of the wires have a nickel coating on the surfaces of the copper layers which are in electrical contact with the graphene layers, i.e. the surfaces of the copper layers which are opposed to the substrate.

[0022] The inclusion of the metal (e.g. nickel) coating provides technical benefits which arise from the method of manufacture. The light emitting structures of the invention are typically prepared by CVD formation of a graphene layer onto the surface of a copper layer. The copper layer acts as a catalyst for the formation of graphene. However, under the harsh conditions of CVD copper can degrade, leading to small amounts of oxide impurities on the copper surface which in turn can lead to small defects in the graphene crystal. The nickel coating simultaneously protects the copper surface and catalyses the graphene formation. This results in both the surfaces of the metal wire and the graphene having fewer defects, i.e. an improved "smoothness" [0023] The copper layer may be from 5 pm to 100 pm thick. Preferably, the copper layer is from 10 pm to 50 pm thick, e.g. from 20 pm to 30 pm thick. Thus, the copper layer may be about 25 pm thick.

[0024] The graphene layer may be mono-layer graphene, it may be bi-layer graphene or it may be few layer graphene. Typically, the graphene will be monolayer graphene.

[0025] The graphene layer will preferably be a single crystal of graphene, e.g. a crystal formed by CVD onto the surface of the copper layer (or onto a coating, e.g. a nickel coating, on that surface).

[0026] The structure comprises one or more LEDs. The LEDs can be selected depending on what wavelength or colour of light is desired. Where it is desired that the light emitted by the structure is white, the LEDs will typically be UV or blue light emitting LEDs and they will typically be coated with a phosphor.

[0027] Phosphors are often transition metal compounds or rare earth compounds of various types. For LED lighting, manufacturers typically selected YAG phosphor. Where the structure comprises more than one LED, the LEDs will typically be arranged in series.

This enables a device to be powered by mains voltage without the need for an intervening transformer.

[0028] The light emitting structure may be suitable for use in a light bulb, e.g. a domestic light bulb.

[0029] In a second aspect of the invention is provided a light emitting device comprising at least one light emitting structure of the first aspect.

[0030] The device may also comprise a rectifier and optionally a capacitor. [0031] The device may be a light bulb, e.g. a domestic light bulb.

[0032] The atmosphere in the light bulb may be air. One of the benefits of the present invention is that the light emitting structures are not sensitive to air degradation and there is no need, therefore, for the atmosphere inside the light bulb to be an inert gas such as xenon. This reduces the cost and complexity of producing the light bulbs of the invention.

[0033] The light emitting structures may be mounted in a moulded plastic unit. The structures of the invention generate so little heat build up that there is no need to produce the mounting from heat resistant materials. This also reduces the cost of producing the light bulbs of the invention.

[0034] It may be that the light bulb does not comprise a heat sink. The light emitting structures of the invention generate so little heat build up that there is no need to include a heat sink to improve the efficiency of the device. This also reduces the cost of producing the light bulbs of the invention.

[0035] The device may be flexible.

[0036] In a third aspect of the invention is provided a process for producing a light emitting structure or a plurality of light emitting structures, the process comprising: a) providing a graphene layer on a patterned copper sheet to form a copper/graphene laminate; b) affixing at least one LED to the copper/graphene laminate to form a light emitting structure or an array of light emitting structures; c) optionally separating the array of light emitting structures from one another to provide a plurality of light emitting structures; wherein the copper sheet is patterned such that the copper/graphene laminate and the at least one LED of the light emitting structure or of each of the plurality of light emitting structures together form an electrical circuit.

[0037] Graphene can be established on Copper and Nickel which catalyze the growth of Graphene. Other substrate can NOT have such as growing mechanism so we use this selectivity to make graphene deposition on the "patterned" substrate to prevent conductive Graphene being coated everywhere.

[0038] The step of providing a graphene layer may comprise the steps of: providing a patterned copper sheet; and forming a graphene layer on the patterned copper sheet.

[0039] The step of providing a patterned copper sheet may comprise the step of: patterning a copper sheet.

[0040] The patterned copper sheet may be mounted on a substrate (e.g. a first substrate). The method may therefore comprise the step of: providing a copper sheet on a substrate (e.g. a first substrate) The copper is plated on the substrate which is pre-cleaned with plasma in the vacuum system and maybe sputtered or evaporated with adhesion promotion metal before plating to enhance the adhesion. Or, on the other extreme, one can plant the pre determined delaminating layerso flexible filament can be formed by delaminating the pre stress layer for delaminating purpose.

[0041] Where the copper sheet is the starting material for the process, the copper sheet may comprise one or more other metals, e.g. it may be coated with one or more other metals. The metal may be capable of catalysing the CVD formation of graphene.

Preferably, the copper sheet is coated with nickel.

[0042] The method may thus also comprise (either before the graphene formation step or before the pattering step) the step of coating the copper sheet with a metal. A adhesion promotion layer was deposited in the vacuum system which can be using either sputtering or evaporation with adhesion promotion metal before plating to enhance the adhesion. Or, on the other extreme, one can plant the predetermined delaminating layer so flexible filament can be formed by delaminating the pre stress layer for delaminating purpose.

[0043] The substrate may be sputtered to form an intermediate layer made of thin chromium metal) before the copper sheet is formed on the substrate. There may be an adhesive layer and the intermediate layer between the copper layer and the substrate.

[0044] The step of patterning the copper sheet may comprise etching (e.g. wet-etching) the copper sheet.

[0045] The step of etching the copper sheet can be achieved by a photo masking method, similar to those methods used for the production of printed circuit boards. In this method, a dry film is the thick photoresist in solid form instead of liquid form. The Dry film is thermal pressed on the substrate instead of traditional spinned coated) and is applied to the surface to be etched, and a mask (a negative of the intended pattern of wires) is applied to the film. The masked film is then subjected to radiation (e.g. uv or visible light) and those areas of the dry film not covered by the mask are cured by the radiation. The image is developed traditional I line exposure and the copper sheet is chemical etchant namely ferro chloride removing those portions of the copper sheet which are not covered by the dry film to provide the desired pattern. Removal of the remaining portions of the dry film can then be achieved by NaOH.

[0046] The method may comprise the step of cleaning the surface of the etched copper sheet.

[0047] The formation of the graphene layer is preferably achieved by CVD. The CVD formation of graphene on copper or coated copper substrates is well known in the art (see, for example, US 8,470,400. The procedures disclosed therein are applicable to the present invention). The graphene is typically grown from a gas phase hydrocarbon (e.g. methane) in the presence of hydrogen at high temperature. The temperature may be from about 200 °C to about 1200 °C. The temperature may be from about 250 °C to about 850 °C. The temperature may be from about 700 °C to about 800 °C. Alternatively, the temperature may be from about 300 °C to about 400 °C.

[0048] Other methods of forming a graphene layer are also possible. These include direct transfer of a layer formed by mechanical exfoliation of graphite. It may also include the deposition (e.g. Langmuir-Blodgett deposition) of a graphene layer comprising numerous flakes of graphene.

[0049] The at least one LED may be in the form of a flip chip. This comprises a LED or array of LEDs with preformed balls of solder in the positions necessary to form electrical connections between the LED(s) and the appropriate portions graphene layers of the wires. The flip chip is preferably affixed to the graphene using a die bonder. Any means by which the solder balls of the flip chip can be melted would also be suitable for use in the process of the invention. Likewise, the LEDs may not necessarily be in the form of a flip chip and may instead be individually soldered into place.

[0050] The process may further comprise the step of coating the LED(s) with a phosphor.

[0051] The process may further comprise the step of coating the LED(s) (and optionally phosphor) with silicone. Phosphor is a powder. To apply phosphor on LED, silicone has to be used to premixed with phosphor and being applied to surface of the LED. This silicone simply play the role of matrix for phosphor and hermetic coating of LED to prevent degradation of LED by environment impact;. The LED will emit blue light and some blue light will be convert by the phosphor which scattered in the silicone matrix. Light will be emitted as a whole a white light out of the silicone LED assembly.

[0052] The process may further comprise the step of affixing a substrate (e.g. a second substrate) to the light emitting structure or array of light emitting structures. In such a case the first substrate may be rigid and the second substrate may be flexible. The second substrate will detach the LED and metal conductive features by adhesion as well as weak adhesion of the first substrate. Typically, the second substrate will be affixed to the outer surface of the LED(s), e.g. to the opposite surface of the silicone to the LED(s). In this case, the silicone may be used both as an adhesive to affix the second substrate to the LED(s) and as a filler to provide a smooth surface to which the second substrate can be attached. Preferably the second substrate is transparent or translucent.

[0053] Where a second substrate has been added, the process will typically comprise the step of removing the first substrate. This is done by using a thermal conductive tape on the second substrate. This adhesive will be glued on the first substrate using some at temperature higher than room temperature. After gluing the second substrate will be used to hold the entire features including LED/Graphene/conduction wire delamination against first substrate. Please note that the preset weak adhesion of features on the first substrate and stronger adhesive force on the second substrate will be the key of success of delamination. This will be the case where the second substrate is desired in the final product but is likely to be degraded in the conditions for forming the copper/graphene laminate.

[0054] This copper wire will have nickel pre-coating on both sides so there will be no bare copper exposed to air in the process [0055] The second substrate may be a polymer substrate, e.g. a flexible polymer substrate. The first substrate may be a rigid substrate, e.g. a glass or quartz substrate.

[0056] Where the product of step b) is a single light emitting structure (which may include one or more than one LED), it will typically be the case that the starting substrate has the desired dimensions of a light emitting structure. In this case there is no need to carry out optional step c).

[0057] Alternatively, it may be that the product of step b) is an array of a plurality of light emitting structures. This will be the case when the starting substrate has dimensions considerably in excess of those desired for an individual light emitting structure and the etching step provides a plurality of individual systems of wires on the substrate. The array may be formed to facilitate mass production of light emitting structures of the invention. In this case, the process further comprises the step of separating the array of light emitting structures from one another to provide a plurality of individual light emitting structures. This step can be performed at any stage after the LED(s) have been introduced, including after a second substrate has been introduced.

[0058] The step of separating the array of light emitting structures may be performed using laser cutter (e.g. where a glass substrate is present) or using a dicing saw (e.g. where the second substrate has been introduced and no rigid substrate is present and that second substrate is a flexible polymer).

[0059] It may be that a functioning electrical circuit (i.e. one which would allow the LEDs to provide light) is only formed after the array of light emitting structures have been cut into individual structures.

[0060] The process may be a process for producing a light emitting device, in which case the process may comprise a further step of incorporating at least one light emitting structure into a device.

[0061] In a fourth aspect of the invention is provided a light emitting structure formed according to the method of the third aspect.

[0062] In a fifth aspect of the invention is provided a light emitting device formed according to the third aspect of the invention.

[0063] Any feature or embodiment described in relation to any one of the first to fifth aspects of the invention applies equally to any other aspect, where not mutually exclusive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The term wire is used throughout this specification to mean a conduit for the conduction of electricity. In the case the term "wire" is being used in its traditional electrical sense. The wires of the present invention comprise a laminate structure comprising a copper layer and a graphene layer. Alternative terms for 'wire' in the context of the present disclosure would be 'track' or 'interconnect' or 'via' similar to those used on a semiconductor chip.

[0065] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figure 1 is an illustrative flow schematic of a process of the invention. DETAILED DESCRIPTION [0066] A layer of graphene consists of a sheet of sp2-hybridized carbon atoms. Each carbon atom is covalently bonded to three neighboring carbon atoms to form a honeycomb' network of tessellated hexagons. Graphite is a bulk material which comprises many graphene layers in a stack. The properties of isolated graphene layers differ significantly to those of graphite. Carbon structures which have more than 10 graphene layers (i.e. 10 atomic layers; 3.5 nm) generally exhibit properties more similar to graphite than to mono-layer graphene. Thus, throughout this specification, the term graphene is intended to mean a carbon material with up to 10 graphene layers. For clarity, a material which has just single layer of graphene (i.e. which is a single carbon atom thick) is referred to throughout this specification as mono-layer graphene. A material with two layers of graphene (i.e. which is two carbon atoms thick) is referred to as bi-layer graphene.

[0067] The term 'few-layered' graphene means a carbon nanomaterial formed from a number of graphene layers but which is sufficiently thin that it exhibits one or more properties which are closer to mono-layer graphene than to graphite. Not all of the properties of the compound will differ between a few-layered and a bulk compound but one or more properties are likely to be different. A more convenient definition would be that the term few layered' refers to a material that is from 2 to 9 carbon atom layers thick (e.g. 3 to 7 atoms thick).

[0068] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0069] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0070] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

EXAMPLES

[0071] An exemplary process for producing light-emitting structures according to the invention is shown in figure 1.

[0072] A quartz substrate 1 was sputtered to provide an intermediate layer 2. The intermediate layer for rigid filament will be very thin chromium as adhesion promotion layer. On the other hand, the intermediate layer for flexible filament will be nickel which has bad adhesion on the first substrate. The substrate was then covered with a layer of copper 3 and the copper was etched to remove portions 4 of the copper layer. CVD was used to deposit a monolayer of graphene onto the surface of the remaining portions of copper to form a graphene/copper laminate 5. LEDs 7 in the form of a flip chip. The LED chips used is a conventional flip chip LED typically by Cree Direct Attach "DA" series LEDs were bonded to the laminate using a die bonder and a coating of phosphor 8 was applied. The resultant product was cut using a laser cutter to generate a series of light emitting structures of the invention.

[0073] Alternatively, a layer of silicone 9 was applied to the surface of the phosphor and a flexible polymer sheet can be applied to the silicone, fixing it in place. The intermediate layer 2 was then delaminated and the quartz substrate 1 was removed to provide an array of light emitting structures attached to a flexible substrate. A dice saw was used to cut the individual light emitting structures 12 from the array 11.

Claims

claims 1. A light emitting structure comprising: a substrate; a system of wires; and at least one LED; wherein each wire comprises a laminate structure comprising a copper layer and a graphene layer; and wherein each wire is in electrical contact with at least one LED and the system of wires and at least one LED together form an electrical circuit; and wherein copper, nickel, and metal composite conduction paths are plated, evaporated, sputtered or glued on the substrate; the substrate is made of transparent material, and the transparent material is any one of sapphire, glasses, quartz, and PET; the metal conductive paths is laid in any length and any shape but preferably in rectangular shape; the conductive layer is made of singular metal, and the singular metal is any one of copper, nickel, and metal composite; the metal composite consists of copper, nickel,and aluminium; the conductive layer is patterned so as to make discrete islands; the at least one LED is bonded on a top of an isolated island for series connection; a graphene layer is grown on a top of patterned copper or nickel; an etched surface area which does not consist of copper or nickel is not coated with Graphene; after Graphene is placed on a top of the wire, the at least one LED is placed using a die bonding manner or a wire bonding manner on the conductive surfaces to form filaments; the at least one LED is connected in series.
2. A light emitting structure of claim 1, wherein the or each LED is in electrical contact with the graphene side of the copper/graphene laminate.
3. A light emitting structure of claim 1 or claim 2, wherein the substrate is situated on the opposing face of the copper layers to the graphene layer.
4. A light emitting structure of claim 3, wherein the substrate is quartz.
5. A light emitting substrate of claim 1 or claim 2, wherein the substrate is situated on the opposite side of the at least one LED to the graphene layer.
6. A light emitting structure of claim 5, wherein the substrate is a flexible polymer.
7. A light emitting structure of any one of claims 1 to 6, wherein the copper layer of the wires comprises at least one other metal.
8. A light emitting structure of claim 7, wherein the at least one other metal is in the form of a coating on the surface of the copper layer which is in contact with the graphene layer.
9. A light emitting structure of claim 7 or claim 8, wherein the at least one other metal is nickel.
10. A light emitting structure of any one of claims 1 to 9, wherein the copper layer of the wires is from 5 pm to 100 pm thick.
11. A light emitting structure of any one of claims 1 to 10, wherein the graphene layer is mono-layer graphene.
12. A light emitting structure of any one of claims 1 to 10, wherein the structure comprises more than one LED and the LEDs are arranged in series.
13. A light emitting device comprising at least one light emitting structure of claims 1 to 12.
14. A device of claim 13, wherein the device is a light bulb.
15. A device of claim 13 or claim 14, wherein the light emitting structures are mounted in a moulded plastic unit. .
16. A device of any one of claims 13 to 15, wherein the device does not comprise a heat sink.
17. A process for producing a light emitting structure or a plurality of light emitting structures, the process comprising: a) providing a graphene layer on a patterned copper sheet to form a copper/graphene laminate; b) affixing at least one LED to the copper/graphene laminate to form a light emitting structure or an array of light emitting structures; c) optionally separating the array of light emitting structures from one another to provide a plurality of light emitting structures; wherein the copper sheet is patterned such that the copper/graphene laminate and the at least one LED of the light emitting structure or of each of the plurality of light emitting structures together form an electrical circuit, wherein Graphene is established on Copper and Nickel which catalyze the growth of Graphene.
18. The process of claim 17, wherein the step of providing a graphene layer comprises the steps of: providing a patterned copper sheet; and forming a graphene layer on the patterned copper sheet.
19. The process of claim 18, wherein the step of providing a patterned copper sheet comprises the step of: patterning a copper sheet.
20. The process of any one of claims 16 to 19, wherein the method also comprises the step of coating the copper sheet with a metal, and an adhesion promotion layer was deposited in a vacuum system which is using either sputtering or evaporation with adhesion promotion metal before plating to enhance the adhesion.
21. The process of ay one of claims 16 to 20, wherein the step of patterning the copper sheet comprises etching (e.g. wet-etching) the copper sheet.
22. The process of any one of claims 16 to 21 wherein the graphene layer is formed by CVD.
23. A process for producing a light emitting device, the process comprising incorporating at least one light emitting structure of any one of claims 16 to 22 into a device.