Patent Publication Number: US-2021167324-A1

Title: Optoelectronic device and process for manufacturing same

Description:
The present patent application claims the priority benefit of French patent application FR18/00561, which is herein incorporated by reference. 
     BACKGROUND 
     The present disclosure generally concerns optoelectronic devices and methods of manufacturing the same and, more particularly, devices comprising a display screen and/or an image sensor. 
     DISCUSSION OF THE RELATED ART 
     Many computers, touch pads, cell phones, smart watches, are equipped with an image sensor. 
       FIG. 1  partially and schematically shows an image sensor  10 . Image sensor  10  comprises an array  11  of detection elements  12 , called optical array hereafter. Detection elements  12  may be arranged in rows and in columns. Each detection element  12  comprises a photodetector  14 , for example, a photodiode, and a selection element  16 , for example, a transistor having its source or drain coupled to a first electrode of photodiode  14 , for example, the cathode. Image sensor  10  comprises a selection circuit  18  comprising, for each row, a conductive track  20  coupled to the gates of selection transistors  16 . Image sensor  10  further comprises a readout circuit  22  comprising, for example, for each column, a conductive track  24  coupled to the source or to the drain of column selection transistors  16 . Further, the second electrodes of photodiodes  14 , for example, the anodes, may be coupled by conductive tracks  26  to a source  28  of a reference potential. 
     It is known to form detection elements  12  at least partly made of organic materials. Optical array  11  may then be formed separately on a substrate and selection circuit  18 , readout circuit  22 , and the source of potential  28  may correspond to external circuits which are connected to optical array  11 . Optical array  11  generally comprises a stack of layers covered with a coating particularly protecting organic photodiodes  14  against water and the oxygen contained in the air. The coating may correspond to a film which is attached to the optical array via an adhesive layer. A film cutting step is then provided after the bonding of the film to the optical array, particularly to expose contact pads of optical array  11  intended to be connected to selection circuit  18 , to readout circuit  22 , and to potential source  28 . The cutting step may be carried out by means of a laser. 
     A disadvantage of such a manufacturing method is that the setting of the laser is difficult, whereby the laser cutting step may cause an unwanted deterioration of the conductive tracks  22 ,  24 ,  26  located on the path of the laser beam. Further, when the substrate is made of plastic, it may be absorbing for the wavelengths of the laser so that the laser cutting step may cause an unwanted deterioration of the substrate on the path of the laser beam. 
     SUMMARY 
     An object of an embodiment is to overcome all or part of the disadvantages of the previously-described optoelectronic devices and of their manufacturing methods. 
     Another object of an embodiment is for the optoelectronic device manufacturing method to comprise a cutting step, particularly a laser cutting step. 
     Another object of an embodiment is for the optoelectronic device to comprise conductive tracks which are not deteriorated. 
     Another object of an embodiment is for the optoelectronic device to comprise a substrate which is not deteriorated. 
     Another object of an embodiment is to provide an optoelectronic device comprising a display screen and/or an image sensor. 
     Another object of an embodiment is for the image sensor to be at least partly made of organic semiconductor materials. 
     Another object of an embodiment is for all or part of the optoelectronic device to be formed by successive depositions of layers by printing techniques, for example, by inkjet, by heliography, by silk-screening, by flexography, or by coating. 
     Thus, an embodiment provides an optoelectronic device comprising a substrate, an array of optoelectronic components covering the substrate, first conductive tracks coupled to the optoelectronic components, an adhesive layer covering a portion of the array, and a coating in contact with the adhesive layer, the coating comprising a periphery, the device further comprising a second track reflecting and/or absorbing a radiation at a wavelength in the range from 335 nm to 10.6 μm and extending, aligned with the periphery along a given direction, between the first conductive tracks and the coating. 
     According to an embodiment, the second track is selected from the group comprising: 
     a metal or a metal alloy, for example, silver (Ag), gold (Au), lead (Pb), palladium (Pd), copper (Cu), nickel (Ni), tungsten (W), molybdenum (Mo), aluminum (Al), or chromium (Cr), or an alloy of magnesium and silver (MgAg); 
     carbon, silver, and copper nanowires; 
     graphene; 
     colored or black resin, for example, colored or black SU-8 resin; and 
     a mixture of at least two of these materials. 
     According to an embodiment, the device comprises a first electrically-insulating layer and, for each optoelectronic component, an electrode in contact with the optoelectronic component, resting on the first insulating layer and in contact with the first insulating layer, the second track resting on the first insulating layer and in contact with the first insulating layer. 
     According to an embodiment, the second track is made of the same material as the electrodes. 
     According to an embodiment, the device comprises a second electrically-insulating layer, and for each optoelectronic component, a field-effect transistor and third conductive tracks coupling the transistor to the optoelectronic component, resting on the second insulating layer and in contact with the second insulating layer, the second track being made of the same material as the third tracks, resting on the second insulating layer and in contact with the second insulating layer. 
     According to an embodiment, the second track is interposed between the adhesive layer and the coating. 
     According to an embodiment, the optoelectronic components comprise organic photodetectors. 
     According to an embodiment, the optoelectronic components comprise organic light-emitting components. 
     An embodiment provides a method of manufacturing the optoelectronic device such as previously defined. 
     According to an embodiment, the method comprises the steps of: 
     forming the array of optoelectronic components covering the substrate and the first conductive tracks coupled to the optoelectronic components; 
     covering the portion of the array with the adhesive layer; 
     applying a film in contact with the adhesive layer; and 
     cutting the film by using a laser beam extending along a given direction to obtain the coating, 
     the method further comprising forming the second track reflecting and/or absorbing the laser beam and extending aligned with the periphery of the coating along said given direction between the first conductive tracks and the coating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features and advantages, as well as others, will be described in detail in the following description of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which: 
         FIG. 1 , previously described, shows an electric diagram of an example of an image sensor; 
         FIGS. 2 and 3  respectively are a cross-section view and a top view, partial and simplified, of an example of an optical array of an image sensor; 
         FIGS. 4A to 4C  are partial simplified cross-section views of the structures obtained at successive steps of an embodiment of a method of manufacturing the optical array shown in  FIGS. 2 and 3 ; 
         FIGS. 5 and 6  respectively are a cross-section view and a top view, partial and simplified, of an embodiment of an optical array; and 
         FIGS. 7 to 9  are partial simplified cross-section views of embodiments of an optical array. 
     
    
    
     DETAILED DESCRIPTION 
     The same elements have been designated with the same reference numerals in the different drawings. The same elements have been designated with the same reference numerals in the different drawings. In particular, the operation of a display screen and of an image sensor has not been detailed, the described embodiments being compatible with usual display screens and image sensors. Further, the other components of the optoelectronic device integrating a display screen and/or an image sensor have not been detailed either, the described embodiments being compatible with the other usual components of display screen and/or image sensor optoelectronic devices. 
     Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other than conductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements. 
     In the following description, when reference is made to terms ““in the order of” and “substantially”, this means within 10%, preferably within 5%. Further, when reference is made to terms qualifying the absolute position, such as terms “top”, “bottom”, etc., or the relative position, such as terms “above”, “under”, “upper”, “lower”, etc., unless specified otherwise, reference is made to the orientation of the drawings. 
     The expression active region of an optoelectronic component, particularly of a light-emitting component or of a photodetector, designates the region from which most of the electromagnetic radiation supplied by the optoelectronic component is emitted or from which most of the electromagnetic radiation received by the optoelectronic component is captured. In the following description, an optoelectronic component is called organic when the active region of the optoelectronic component is mainly, preferably totally, made of at least one organic material or of a mixture of organic materials. Further, an element said to be reflective for a radiation is an element having its reflection factor for the radiation greater than 80%, preferably greater than 90%, more preferably greater than 95%, the reflection factor being defined as being the ratio of the flow of the reflected radiation to the flow of the incident radiation. 
     An embodiment will now be described for an optical array in the case where the optoelectronic components of the optical array are organic photodiodes. It should however be clear the electronic components may correspond to light-emitting components. 
       FIG. 2  is a partial simplified lateral cross-section view of an example of an optical array  30  having an electric diagram capable of corresponding to the optical array  11  shown in  FIG. 1 . 
     Optical array  30  comprises, from bottom to top in  FIG. 2 : 
     a substrate  32 ; 
     a stack  34  having thin-film transistors formed therein, a single transistor T being shown in  FIG. 2 ; 
     electrodes  36 , each electrode  36  being coupled to one of transistors T, a single electrode  36  being shown in  FIG. 2 ; 
     photodetectors  38 , for example, organic photodiodes, also called OPD, a single photodiode  38  being shown in  FIG. 2 , each photodiode  38  being in contact with one of electrodes  36 ; 
     an electrode  40  in contact with all organic photodiodes  38 ; 
     a layer of an adhesive material  42 ; and 
     a coating  44 . 
     According to an embodiment, each photodiode  38  comprises an active region  46 , electrodes  36  and  40  being in contact with active region  46 . As a variant, each organic photodiode  38  may comprise a first interface layer in contact with one of electrodes  36 , active region  46  in contact with the first interface layer, and a second interface layer in contact with active region  46 , electrode  40  being in contact with the second interface layer. 
     According to the present embodiment, stack  34  comprises: 
     electrically-conductive tracks  50 ,  51  resting on substrate  32 , tracks  50  forming the gate conductors of transistors T and tracks  51  being coupled with the drains or with the sources of transistors T; 
     a layer  52  of a dielectric material covering tracks  50 ,  51  and substrate  32  between tracks  50 ,  51  and forming the gate insulators of transistors T; 
     active regions  54  resting on dielectric layer  52  opposite gate conductors  50 ; 
     electrically-conductive tracks  56  extending on dielectric layer  52 , some of these tracks being in contact with active regions  54  and forming the drain and source contacts of transistors T, some of tracks  56  being electrically coupled to tracks  51  via electrically-conductive vias  57  extending through layer  52 ; and 
     a layer  58  of a dielectric material covering active regions  54  and electrically-conductive tracks  56 , electrodes  36  resting on layer  58  and being connected to some of conductive tracks  56  by conductive vias  60  crossing insulating layer  58  and electrode  40  being connected to some of conductive tracks  51  by conductive vias, not shown in  FIG. 2 , crossing insulating layers  58  and  52 . 
     As a variant, transistors T may be of high gate type. 
     When at least one interface layer is present in contact with active region  46 , this interface layer may correspond to an electron injection layer or to a hole injection layer. The work function of each interface layer is capable of blocking, collecting, or injecting holes and/or electrons according to whether the interface layer plays the role of a cathode or of an anode. More particularly, when the interface layer plays the role of an anode, it corresponds to a hole injection and electron blocking layer. The work function of the interface layer is then greater than or equal to 4.5 eV, preferably greater than or equal to 5 eV. When the interface layer plays the role of a cathode, it corresponds to an electron injection and hole blocking layer. The work function of the interface layer is then smaller than or equal to 4.5 eV, preferably smaller than or equal to 4.2 eV. 
     In the present embodiment, electrode  36  or  40  advantageously directly plays the role of an electron injection layer or of a hole injection layer for photodiode  38 , and it is not necessary to provide, for photodiode  38 , an interface layer in contact with active region  46  and playing the role of an electron injection layer or of a hole injection layer. 
     Substrate  32  may be a rigid substrate or a flexible substrate. Substrate  32  may have a monolayer structure or correspond to a stack of at least two layers. An example of a rigid substrate comprises a silicon, germanium, or glass substrate. Preferably, substrate  32  is a flexible film. An example of flexible substrate comprises a film of PEN (polyethylene naphthalate), PET (polyethylene terephthalate), PI (polyimide), TAC (cellulose triacetate), COP (cycloolefin copolymer), or PEEK (polyetheretherketone). The thickness of substrate  32  may be in the range from 5 μm to 1,000 μm. According to an embodiment, substrate  32  may have a thickness from 10 μm to 300 μm, preferably from 75 μm to 250 μm, particularly in the order of 125 μm, and may have a flexible behavior, that is, substrate  32  may, under the action of an external force, deform, and particularly bend, without breaking or tearing. Substrate  32  may comprise at least one substantially oxygen- and moisture-tight layer, to protect the organic layers of optical array  30 . This may be one or a plurality of layers deposited by an atomic layer deposition (ALD) method, for example, an Al 2 O 3  layer. 
     According to an embodiment, the material forming electrodes  36 ,  40  is selected from the group comprising: 
     a transparent conductive oxide (TCO), particularly indium tin oxide (ITO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), an ITO/Ag/ITO alloy, an ITO/Mo/ITO alloy, a AZO/Ag/AZO alloy, or a ZnO/Ag/ZnO alloy; 
     a metal or a metal alloy, for example, silver (Ag), gold (Au), lead (Pb), palladium (Pd), copper (Cu), nickel (Ni), tungsten (W), molybdenum (Mo), aluminum (Al), or chromium (Cr), or an alloy of magnesium and silver (MgAg); 
     carbon, silver, and/or copper nanowires; 
     graphene; and 
     a mixture of at least two of these materials. 
     The material forming electrode  40  may further be selected from the group comprising the PEDOT:PSS polymer, which is a mixture of poly(3,4)-ethylenedioxythiophene and of sodium polystyrene sulfonate, or a polyaniline, tungsten oxide (WO 3 ), nickel oxide (NiO), vanadium oxide (V 2 O 5 ), or molybdenum oxide (MoO 3 ). 
     When optical array  30  is exposed to a light radiation, the latter reaches photodiodes  38  through coating  44 , electrode  40 , and coating  44  are at least partly transparent to the electromagnetic radiation captured by photodiodes  38 . Electrode  40  is for example made of TCO. Electrodes  36  and substrate  32  may then be opaque to the electromagnetic radiation captured by photodiodes  38 . When the radiation reaches photodiodes  38  through substrate  32 , electrodes  36  and substrate  32  are made of a material at least partly transparent to the electromagnetic radiation captured by photodiodes  38 . Electrodes  36  are for example made of TCO. Electrode  40  may then be opaque to the electromagnetic radiation captured by photodiodes  38 . 
     Each insulating layer  52 ,  58  may have a monolayer or multilayer structure and comprise at least one layer made of silicon nitride (SiN), of silicon oxide (SiO 2 ), or of a polymer, particularly, a resin. 
     Layer  42  of adhesive material is transparent or partially transparent to visible light. Layer  42  of adhesive material is preferably substantially air- and water-tight. The material forming layer  42  of adhesive material is selected from the group comprising a polyepoxide or a polyacrylate. Among polyepoxides, the material forming layer  42  of adhesive material may be selected from the group comprising bisphenol A epoxy resins, particularly the diglycidylether of bisphenol A (DGEBA) and the diglycidylethers of bisphenol A and of tetrabromobisphenol A, bisphenol F epoxy resins, novolac epoxy resins, particularly epoxy-phenol-novolacs (EPN) and epoxy-cresol-novolacs (ECN), aliphatic epoxy resins, particularly epoxy resins with glycidyl groups and cycloaliphatic epoxides, glycidyl amine epoxy resins, particularly the glycidyl ethers of methylene dianiline (TGMDA), and a mixture of at least two of these compounds. Among polyacrylates, the material forming layer  42  of adhesive material may be made from monomers comprising acrylic acids, methylmethacrylate, acrylonitrile, methacrylates, methyl acrylate, ethyl acrylate, 2-chloroethyl vinyl ether, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, butyl acrylate, butyl methacrylate, trimethylolpropane triacrylate (TMPTA), or derivatives of these products. 
     When layer  42  of adhesive material comprises at least one polyepoxide or a polyacrylate, the thickness of layer  42  of adhesive layer  42  is in the range from 1 μm to 50 μm, preferably from 5 μm to 40 μm, particularly in the order of 15 μm. 
     Coating  44  is a flexible film. An example of flexible film comprises a film of PEN (polyethylene naphthalate), PET (polyethylene terephthalate), PI (polyimide), TAC (cellulose triacetate), COP (cycloolefin copolymer), or PEEK (polyetheretherketone). The thickness of coating  44  may be in the range from 5 μm to 1,000 μm. 
     According to an embodiment, substrate  32  may have a thickness from 10 μm to 300 μm, preferably from 25 μm to 100 μm, particularly in the order of 50 μm, and may have a flexible behavior, that is, the coating may, under the action of an external force, deform, and particularly bend, without breaking or tearing. Coating  44  may comprise at least one substantially oxygen- and moisture-tight layer to protect the organic layers of optical array  30 . Coating  44  may comprise at least one SiN layer, for example, deposited by plasma-enhanced chemical vapor deposition (PECVD) and/or one aluminum oxide layer (Al 2 O 3 ), for example, deposited by ALD. 
     Active region  46  comprises at least one organic material and may comprise a stack or a mixture of a plurality of organic materials. Active region  46  may comprise a mixture of an electron donor polymer and of an electron acceptor molecule. The functional area of active region  46  is delimited by the overlapping of lower electrode  36  and of upper electrode  40 . The currents crossing the functional area of active region  46  may vary from a few femtoamperes to a few microamperes. The thickness of the active region  46  covering lower electrode  36  may be in the range from 50 nm to 5 μm, preferably from 300 nm to 2 μm, for example, in the order of 500 nm. 
     Active region  46  may comprise small molecules, oligomers, or polymers. These may be organic or inorganic materials. Active layer  46  may comprise an ambipolar semiconductor material, or a mixture of an N-type semiconductor material and of a P-type semiconductor material, for example in the form of stacked layers or of an intimate mixture at a nanometer scale to form a bulk heterojunction. 
     Example of P-type semiconductor polymers capable of forming active region  42  are poly(3-hexylthiophene) (P3HT), poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4,7-di-2-thienyl-2′,1′,3′-benzothiadiazole] (PCDTBT), Poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thie-no[3,4-b]thiophene))-2,6-diyl]; 4,5-b′]dithi-ophene)-2,6-diyl-alt-(5,5′-bis(2-thienyl)-4,4,-dinonyl-2,2′-bithiazole)-5′,5″-diyl] ( PBDTTT-C), le poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) or Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT). 
     Examples of N-type semiconductor materials capable of forming active region  42  are fullerenes, particularly C60, [6,6]-phenyl-C 61 -methyl butanoate ([60]PCBM), [6,6]-phenyl-C 71 -methyl butanoate ([70]PCBM), perylene diimide, zinc oxide (ZnO), or nanocrystals enabling to form quantum dots. 
     In the case where an interface layer is present and the interface layer plays the role of an electron injection layer, the material forming the interface layer is selected from the group comprising: 
     a metal oxide, particularly a titanium oxide or a zinc oxide; 
     a molecular host/dopant system, particularly the products commercialized by Novaled under trade names NET-5/NDN-1 or NET-8/MDN-26; 
     a conductive or doped semiconductor polymer, for example, the PEDOT:Tosylate polymer, which is a mixture of poly(3,4)-ethylenedioxythiophene and of tosylate; 
     a carbonate, for example CsCO3; 
     a polyelectrolyte, for example, poly[9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene-alt-2,7-(9,9-dioctyfluorene)] (PFN), poly[3-(6-trimethylammoniumhexyl] thiophene (P3TMAHT) or poly[9,9-bis(2-ethylhexyl)fluorene]-b-poly[3-(6-trimethylammoniumhexyl] thiophene (PF2/6-b-P3TMAHT); 
     a polyethyleneimine (PEI) polymer or a polyethyleneimine ethoxylated (PEIE), propoxylated, and/or butoxylated polymer; 
     MgAg; 
     tris(8-hydroxyquinoline)aluminum(III) (Alq 3 ); 
     2-(4-Biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (Bu-PBD); and 
     a mixture of two or more of these materials. 
     In the case where an interface layer is present and the interface layer plays the role of a hole injection layer, the material forming the interface layer may be selected from the group comprising: 
     a conductive or doped semiconductor polymer, particularly the materials commercialized under trade names Plexcore OC RG-1100, Plexcore OC RG-1200 by Sigma-Aldrich, PEDOT:PSS; 
     a molecular host/dopant system, particularly the products commercialized by Novaled under trade names NHT-5/NDP-2 or NHT-18/NDP-9; 
     a polyelectrolyte, for example, Nafion; 
     a metal oxide, for example, a molybdenum oxide, a vanadium oxide, ITO, or a nickel oxide; 
     Bis[(1-naphthyl)-N-phenyl]benzidine (NPB); 
     triarylamines (TPD); and 
     a mixture of two or more of these materials. 
     Preferably, in the case where the interface layer plays the role of a hole injection layer, the material forming the interface layer is a conductive or doped semiconductor polymer. 
     In the case where the optical array comprises light-emitting components, particularly organic light-emitting diodes, the active region of the light-emitting diode is for example made of a light-emitting material. The light-emitting material may be a polymeric light-emitting material, such as described in the publication entitled “Progress with Light-Emitting Polymers” of M. T. Bernius, M. Inbasekaran, J. O&#39;Brien and W. Wu (Advanced Materials, 2000, Volume 12, Issue 23, pages 1737-1750) or a light-emitting material of low molecular weight such as aluminum trisquinoline, as described in patent U.S. Pat. No. 5,294,869. The light-emitting material may comprise a mixture of a light-emitting material or of a fluorescent dye or may comprise a layered structure of a light-emitting material and of a fluorescent dye. Light-emitting polymers comprise polyfluorene, polybenzothlazole, polytriarylamine, poly (phenylenevinylene), and polythiophene. The preferred light-emitting polymers comprise homopolymers and copolymers of 9,9-di-n-octylfluorene (F8), of N, N-bis (phenyl)-4-sec-butylphenylamine (TFB), of benzothiadiazole (BT), and of 4,4′-N,N′-dicarbazole-biphenyl (CBP) doped with iridium tris(2-phenylpyridine) (Ir(ppy)3). The thickness of active region  46  is in the range from 1 nm to 100 nm. 
     Conductive tracks  50 ,  51 ,  56  may be made of the same material as electrodes  36  or  40 . The thickness of conductive tracks  50 ,  51  may be smaller than 50 μm. 
     Active regions  54  may be made of polysilicon, particularly low-temperature polycrystalline silicon (LIPS), of amorphous silicon (aSi), of zinc-gallium-indium (IGZO), of polymer, or comprise small molecules used in known fashion for the forming of organic thin film transistors (OTFT). 
     Each insulating layer  52 ,  58  may be made of SiN, of SiO 2 , or of an organic polymer. Insulating layer  52  may have a thickness in the range from 10 nm to 4 μm and insulating layer  58  may have a thickness in the range from 10 nm to 4 μm. 
     Optical array  30  may further comprise a polarizing filter, for example arranged on coating  44 . Optical array  30  may further comprise color filters opposite photodetectors  38  to obtain a wavelength selection of the radiation reaching photodetectors  38 . 
       FIG. 3  is a partial simplified top view of the optical array  30  shown in  FIG. 2 .  FIG. 3  shows in dotted lines  60  the periphery of the area having photodiodes  38  formed therein and in full lines and dotted lines  62  the peripheries of areas having conductive tracks  50  and  51  formed therein. The periphery  64  of coating  44  has further been shown with a full line. As shown in  FIG. 3 , a portion of areas  62 , shown in full lines, is not covered with coating  44  to allow the connection to conductive tracks  50 ,  51  of selection circuit  18 , of readout circuit  22 , and of potential source  28 , not shown in  FIG. 3 . 
       FIGS. 4A to 4C  are partial simplified cross-section views of the structures obtained at successive steps of another embodiment of a method of manufacturing the optical array  30 . 
       FIG. 4A  shows the structure obtained after the forming of the stack of layers comprising transistors T, electrodes  36 , photodetectors  38 , electrode  40 , and layer  42  of adhesive material. 
     According to the considered materials, the method of forming the layers of the optical array may correspond to a so-called additive process, for example, by direct printing of the material forming the organic layers at the desired locations, particularly in sol-gel form, for example, by inkjet printing, photogravure, silk-screening, flexography, spray coating, or drop casting. According to the considered materials, the method of forming the layers of the optical array may correspond to a so-called subtractive method, where the material forming the organic layers is deposited all over the structure and where the non-used portions are then removed, for example, by photolithography or laser ablation. According to the considered material, the deposition over the entire structure may be performed, for example, by liquid deposition, by cathode sputtering, or by evaporation. Methods such as spin coating, spray coating, heliography, slot-die coating, blade coating, flexography, or silk-screening, may in particular be used. When the layers are metallic, the metal is for example deposited by evaporation or by cathode sputtering over the entire support and the metal layers are delimited by etching. 
     Advantageously, at least some of the layers of the optical array may be formed by printing techniques. The materials of the previously-described layers may be deposited in liquid form, for example, in the form of conductive and semiconductor or insulating inks by means of inkjet printers. “Materials in liquid form” here also designates gel materials capable of being deposited by printing techniques. Anneal steps may be provided between the depositions of the different layers, but it is possible for the anneal temperatures not to exceed 150° C., and the deposition and the possible anneals may be carried out at the atmospheric pressure. 
       FIG. 4B  shows the structure obtained after the deposition of a film  68  made of the same material as the desired coating  44 . This may be performed by a lamination step during which film  68  is applied against adhesive layer  42 , possibly under pressure and with a heating. 
       FIG. 4C  shows the structure obtained after a step of coating of film  68  to form coating  44 . The cutting step may be a laser cutting step. As an example, the laser is a CO 2 -type continuous laser with a wavelength in the range from 9.4 μm to 10.6 μm. As an example, the power of the laser is in the range from 1 W to 100 W, the displacement speed being in the range from 1 cm/s to 10 m/s. An alternative is to use a continuous nitrogen laser with a 337.1-nm wavelength or a pulsed Yag laser with wavelengths of from 1,050 nm to 1,070 nmn, 1,550 nm, or 2,100 nm. The cutting is preferably performed with a CO 2  laser. The path followed by the laser beam is schematically indicated in  FIG. 4C  by arrows  64 . 
     The inventors have shown that the laser cutting step may cause a deterioration of conductive tracks  50 ,  51  by the laser beam, and particularly a local interruption of conductive tracks  50 ,  51 , on the path of the laser. Further, in the case where substrate  32  is made of a plastic material, substrate  32  may absorb the laser beam, which may cause a local deterioration of substrate  32  on the path of the laser. 
     The inventors have shown that deteriorations due to the laser cutting step may be avoided by providing a track of a material reflecting the laser radiation and/or of a material absorbing the laser radiation on the path of the laser during the cutting step, the track being interposed between the laser beam on the one hand and conductive tracks  50 ,  51  and substrate  32  on the other hand. Preferably, the width of this track is greater than 500 μm, preferably greater than 1 mm. 
       FIGS. 5 and 6  respectively are a cross-section view and a top view, partial and simplified, of an embodiment of an optical array  70  comprising a protection for the cutting step. Optical array  70  comprises all the elements of the optical array  30  shown in  FIG. 2  and further comprises at least one reflective track  72  resting on insulating layer  58  on the cutting path of film  68 . According to an embodiment, reflective track  72  is an electrically-conductive track formed simultaneously to electrodes  36  and made of the same material as electrodes  36  when electrodes  36  are made of a reflective material. 
       FIG. 7  is a partial simplified cross-section view of an embodiment of an optical array  75  comprising a protection for the cutting step. Optical array  75  comprises all the elements of the optical array  30  shown in  FIG. 2  and further comprises a reflective track  76  resting on insulating layer  52  on the cutting path of film  68 . According to an embodiment, reflective track  76  is an electrically-conductive track formed simultaneously to tracks  56  and made of the same material as tracks  56 . 
     According to an embodiment, the material forming track  72  or  76  is selected from the group comprising: 
     a metal or a metal alloy, for example, silver (Ag), gold (Au), lead (Pb), palladium (Pd), copper (Cu), nickel (Ni), tungsten (W), molybdenum (Mo), aluminum (Al), or chromium (Cr), or an alloy of magnesium and silver (MgAg); 
     an ITO/Mo/ITO stack; 
     carbon, silver, and/or copper nanowires; 
     graphene; and 
     a mixture of at least two of these materials. 
     The thickness of track  72  or  76  may be in the range from 10 nm to 10 μm. 
     When track  72 ,  76  is electrically conductive, it may be coupled, during the operation of the optical array, to a source of a low reference potential, for example, to ground, to the source of potential  28 , or to a source of the potential controlling the turning on of transistors T. 
       FIG. 8  is a partial simplified cross-section view of an embodiment of an optical array  80  comprising a protection for the cutting step. Optical array  80  comprises all the elements of the optical array  30  shown in  FIG. 2  and further comprises a track  82  of a material absorbing the radiation of the laser and resting on insulating layer  58  on the cutting path of film  68 . Track  82  may be made of colored resin, for example, a colored or black SU-8 resin. In the present embodiment, track  82  is formed on insulating layer  58  before the deposition of adhesive layer  42 , for example, according to one of the previously described additive or subtractive method techniques. The thickness of track  82  may be in the range from 100 nm to 50 μm. 
       FIG. 9  is a partial simplified cross-section view of an embodiment of an optical array  85  comprising a protection for the cutting step. Optical array  85  comprises all the elements of the optical array  30  shown in  FIG. 2  and further comprises a track  86  of a material absorbing the radiation of the laser resting on adhesive layer  42  on the cutting path of coating  44 . Track may be made of the same material as track  82 . In the present embodiment, track  86  is formed on adhesive layer  42  before the application of the film forming coating  44 , for example, according to one of the previously described additive or subtractive method techniques. 
     Various embodiments with different variants have been described hereabove and various variants and modifications will occur to those skilled in the art. It should be noted that those skilled in the art may combine these various embodiments and variants without showing any inventive step. In particular, the optical array may comprise both photodetectors and light-emitting components.