Organic optoelectronic device and method for the encapsulation thereof

Abstract

The invention relates to an organic optoelectronic device which is protected from ambient air by a sealed encapsulation structure of the type including at least one thin layer. The device includes a substrate; at least one light-emitting unit deposited on the substrate, incorporating internal electrodes and external electrodes defining an active zone and, between the electrodes, a stack of organic films; and a sealed encapsulation structure having one or more thin layers including at least one inorganic layer placed on top of the light-emitting unit and encasing same laterally. The device also includes a pre-encapsulation structure located between the external electrode and the encapsulation structure and which includes a buffer layer covering the external electrode and contains a heterocyclic organometallic complex having a glass transition temperature above 80° C., and a barrier layer covering the buffer layer and contains a silicon oxide SiOx, wherein x is 0<x<2.

1 . A method for the encapsulation of a device comprising the following successive steps:
 a) depositing a buffer layer on an external electrode of an electroluminescent unit or on each of a plurality of electroluminescent units, the buffer layer being based on an organometallic complex derived from quinoline or benzoquinoline with a glass transition temperature above 100° C., wherein the at least one electroluminescent unit or plurality of electroluminescent units are deposited on a substrate and incorporate an internal electrode adjacent to said substrate, an external electrode which is transparent or semi-transparent to the light emitted by said at least one electroluminescent unit or said plurality of electroluminescent units, and which defines an active light emission zone, and a stack of organic films between said internal electrode and said external electrode, said stack comprising innermost said organic films,   b) depositing a barrier layer by non-reactive thermal evaporation on said buffer layer, the barrier layer being based on an oxide with the formula SiOx, where x is substantially equal to 1, and laterally coating the buffer layer,   c) optionally, transferring the electroluminescent unit, or each electroluminescent unit of the plurality of electroluminescent units, covered with said buffer and barrier layers for encapsulation, directly to an ambient atmosphere without being confined in a transfer enclosure,   d) subjecting the electroluminescent unit, or each electroluminescent unit of the plurality of electroluminescent units, covered with said buffer and barrier layers to dry etching, and then   e) depositing an inorganic layer or inner inorganic layer on the barrier layer by atomic layer deposition (ALD) or by plasma-assisted chemical vapor phase deposition (PECVD), said inner inorganic layer being based on at least one inorganic compound selected from the group consisting of AlxOy, SiOx, SixNy, SiOxNy, ZnSe, Sb2O3 and transparent conductive oxides (TCOs) optionally combined with a metal, wherein said inner inorganic layer extends from said substrate, thereby laterally coating the barrier layer and the innermost film or films of said stack.   
     
     
         2 . The method as claimed in  claim 1 , wherein step d) is carried out in order to structure at least one of the innermost active films of said stack of this unit, in the case where it has been deposited by a liquid route over the whole substrate, so that it terminates laterally at right angles to or within a peripheral edge of said barrier layer, by removal of the portion of said at least one film which extends laterally beyond the barrier layer, said at least one structured film forming, these buffer and barrier layers then acting as a hard mask during the etching. 
     
     
         3 . The method as claimed in  claim 2 , wherein the method comprises, before step a), deposition by localized spraying of metal atoms through said innermost active film or films which have been deposited previously by a liquid route, so that these atoms are distributed through said active film or films, thus forming therein an electrically conductive annular channel which directly connects an inner peripheral edge of the external electrode to an electrical contact of the latter provided in said substrate. 
     
     
         4 . The method as claimed in  claim 3 , wherein said deposition is carried out by localized spraying by means of a perforated mask, in order to give said channel an annular shape like that of said electrical contact of the external electrode, this spraying being carried out, according to choice, either
 before the deposition of the external electrode, directly onto and through said innermost active film or films deposited by a liquid route, or   after the deposition of the external electrode, directly onto and through this external electrode and the innermost active film or films.   
     
     
         5 . The method as claimed in  claim 1 , further comprises a step f), following step e), in which:
 f1) a photosensitive layer, based for example on a positive photolithographic resin, is deposited in liquid phase onto said inner inorganic layer,   f2) this photosensitive layer, deposited in this way, is etched by irradiation at predetermined points by selectively masking the incident radiation so that the layer is polymerized as a result of this irradiation above said inner inorganic layer and in an enveloping portion which originates from the substrate and laterally coats this inner inorganic layer, and is depolymerized elsewhere, after which   f3) this polymerized photosensitive layer is developed by immersion in a bath, optionally followed by supplementary irradiation of this photosensitive layer.   
     
     
         6 . The method as claimed in  claim 5 , wherein the method further comprises a step g), following step f), in which another said inorganic layer, or outer inorganic layer, which is for example based on the same compound as said inner inorganic layer, is deposited onto said photosensitive polymer layer and also covers this photosensitive polymer layer in a laterally encasing manner, so as to form a plurality of surfaces, parallel to each other and substantially perpendicular to the plane of the substrate, which surfaces form respective obstacles to the lateral penetration of water vapor toward the active area or each active area of the device. 
     
     
         7 . The method of  claim 1 , wherein said organometallic complex derived from quinoline or benzoquinoline is tris(8-hydroxyquinolinato)aluminum (III) (Alq3). 
     
     
         8 . The method of  claim 1 , wherein said dry etching is carried out an oxygen plasma or by reactive ion etching. 
     
     
         9 . The method of  claim 1 , wherein said inner inorganic layer is based on Al 2 O 3  deposited by ALD, in such a way that this inner inorganic layer extends from the substrate, thereby laterally coating the barrier layer and innermost film or films of said stack. 
     
     
         10 . The method as claimed in  claim 4 , wherein said case has a thickness of less than 20 nm. 
     
     
         11 . The method as claimed in  claim 1 , wherein said at least one structured film comprises an electron transport film (ETL), a hole injection film (HIL) and/or a hole transport film (HTL). 
     
     
         12 . A method for the encapsulation of an organic optoelectronic device comprising the following successive steps:
 1) providing a substrate,   2) depositing at least one electroluminescent unit on said substrate by a deposition of an internal electrode adjacent to said substrate, of an external electrode which is transparent or semi-transparent to the light emitted by said at least one electroluminescent unit and which defines an active light emission zone, and of a stack of organic films between said internal electrode and said external electrode, said stack comprising innermost said organic films, and   3) depositing a pre-encapsulation structure on said external electrode which comprises a buffer layer covering said external electrode and based on at least one heterocyclic organometallic complex with a glass transition temperature above 80° C., and a barrier layer covering said buffer layer and based on a silicon oxide with the formula SiO x , where x is a real number such that 0<x<2,   4) depositing a thin-layer encapsulation structure on said pre-encapsulation structure which comprises at least one inorganic layer which is placed on top of said at least one electroluminescent unit and encases it laterally,   wherein step 3) comprises:
 a) depositing said buffer layer on said external electrode of said at least one electroluminescent unit, 
 b) depositing said barrier layer by non-reactive thermal evaporation on said buffer layer, said barrier layer laterally coating said buffer layer, 
 c) optionally transferring said at least one electroluminescent unit, covered for encapsulation with said buffer layer and said barrier layer, directly to the ambient atmosphere without being confined in a transfer enclosure such as a glove box, and 
 d) subjecting to dry etching said at least one electroluminescent unit, covered with said buffer layer and said barrier layer, by means of an oxygen plasma or by reactive ion etching, to structure at least one of said innermost organic films to make it terminate laterally substantially at right angles to a peripheral edge of said barrier layer, 
   and wherein step 4) comprises:
 e) depositing an inner said inorganic layer of said thin-layer encapsulation structure on said barrier layer by atomic layer deposition (ALD) or by plasma-assisted chemical vapor phase deposition (PECVD), said inner inorganic layer being based on at least one inorganic compound selected from the group consisting of compounds with the formulae Al x O y , SiO x , Si x N y , SiO x N y , ZnSe, Sb 2 O 3  and transparent conductive oxides (TCOs) optionally combined with a metal, in such a way that said inner inorganic layer extends from said substrate, thereby laterally coating said barrier layer and said innermost organic films of said stack of organic films. 
   
     
     
         13 . The method as claimed in  claim 12 , wherein said at least one of said innermost organic films is deposited in step 2) by a liquid route over all said substrate and is structured by dry etching in step 3) d) by removal of the portion of said at least one of said innermost organic films which extends laterally beyond the barrier layer and which forms an electron transport film (ETL), a hole injection film (HIL) or a hole transport film (HTL), said buffer layer and said barrier layer then acting as a hard mask during said dry etching. 
     
     
         14 . The method as claimed in  claim 13 , wherein the method comprises, before step 3) a), a deposition by localized spraying of metal atoms through said at least one of said innermost organic films which has been deposited previously by a liquid route, so that these atoms are distributed through said at least one of said innermost organic films, thus forming therein an electrically conductive annular channel which directly connects an inner peripheral edge of said external electrode which surmounts without contact said substrate to an electrical contact of said external electrode which is provided in said substrate. 
     
     
         15 . The method as claimed in  claim 14 , wherein said deposition by localized spraying of metal atoms is carried out by means of a perforated mask, in order to give said electrically conductive annular channel an annular shape like that of said electrical contact of said external electrode, said spraying being carried out: before said deposition of said external electrode, directly onto and through said at least one of said innermost organic films deposited by a liquid route, or after said deposition of said external electrode, which in this case has a thickness of less than 20 nm, directly onto and through said external electrode and said at least one of said innermost organic films. 
     
     
         16 . The method as claimed in  claim 12 , wherein the method further comprises a step 4) f), following step 4) e), in which:
 f1) a photosensitive layer, based on a positive photolithographic resin, is deposited in liquid phase onto said inner inorganic layer,   f2) said photosensitive layer, deposited in this way, is etched by irradiation at predetermined points by selectively masking the incident radiation so that said photosensitive layer is polymerized as a result of said irradiation above said inner inorganic layer and in an enveloping portion which originates from said substrate and laterally coats said inner inorganic layer, and is depolymerized elsewhere, after which   f3) said photosensitive layer which is polymerized is developed by immersion in a bath, optionally followed by supplementary irradiation of said photosensitive layer.   
     
     
         17 . The method as claimed in  claim 16 , wherein the method further comprises a step g), following step f), in which an outer said inorganic layer which is external relative to said inner organic layer and is based on the same compound as said inner inorganic layer, is deposited onto said photosensitive layer and also covers said photosensitive layer in a laterally encasing manner, so as to form a plurality of surfaces, parallel to each other and substantially perpendicular to the plane of said substrate, which plurality of surfaces form respective obstacles to a lateral penetration of water vapor toward said active light emission zone of the device.