The Study Of Thin-film Encapsulation Based On Organic Light-emitting Diodes

Organic light-emitting diode?OLED?display products gradually become a leader in the display product market because of its advantages of wide color gamut,fast response,energy saving,flexibility and so on.People not only want to use hard OLED panels,but also hope to experience the unique charm of flexible OLED panels.In fact,the OLED device?including the active metal cathode and organic layer?is sensitive to water vapor and oxygen in the external environment,and the presence of water oxygen make the functional layers gradually corroded corroded and degenerated.In order to ensure the normal life of OLED products,OLED panel must be encapsulated,and then assembled into mobile phones,monitors and other products.Flexible OLEDs will face much more complex packaging problems.The encapsulation layer should maintain the same bending property with the OLED.And more importantly,the barrier mush achieve good enough barrier performance,even if having performed bending for many time.At present,the mainstream flexible encapsulation solution is divided into two kinds.One is the thin-film packaging technology?TFE?,namely the barrier layers are directly deposited on the surface of OLED device;the second is the flexible capping solution,which deposited barrier layers on the flexible substrate firstly,and then the flexible capping film adhesives to the OLED with curing glue.The research content of this paper is based on thin-film encapsulation technology.Based on ALD technology,the effects of ALD flow process,optimizing oxidative precursors and nano-laminated structure on the barrier properties of inorganic barrier films were studied.First,the Al₂O₃ film achieved WVTR to the level of 10-5 g/m2/day by optimizing the oxygen source precursor and good feedback was obtained on the encapsulated OLED device.However,Al₂O₃ film can not withstand high temperatures,like 60 oC where the film will be corroded quickly,lossing its barrier properties.In order to improve the high temperature resistance of barrier films,we introduce MgO layer,which was able to absorb water,to prepare Al₂O₃/MgO nanostructure films,referred to as AMO films.With process optimization,the WVTR of the AMO film could achieve to 10-6 g/m2/day,and the encapsulated OLED device exhibits a storage life of more than 600 h under condition of 60 oC and 100% RH,confirming that the AMO film was resistant to a high temperature of 60 oC and having better barrier performance.The content above corresponds to the third chapter of the article,with the experiment around the preparation of the Al₂O₃ film and the AMO film,where I participated in part of the work about the film deposition and device characterization.On this basis,it is believed that the packaging film has poor weather resistance,with the film been damaged by external particles easily.Therefore,I recommend introducing an organic protective layer over the inorganic barrier layer to protect it from external physical damage.Three kinds of polymer material were perpared to protect the AMO layer to form an inorganic-organic composite encapsulation structure by spin-coating which was characterized fully.We have concluded that the introduction of the organic protective layer can effectively improve the barrier effect and the WVTR of encapsulation layer was further reduced.The results of verification on a 5.2-inch green OLED device also show that the composite barrier film does have good weather resistance.In the chemical resistance test,there was no influence on AMO + CYTOP composite film when soaked into developing solution,stripping solution and acetone for 5 min.In summary,it is believed that AMO + CYTOP composite barrier structure has both outstanding barrier properties and excellent weather resistance,which could resist against part of external physical damage and chemical damage,as a reliable encapsulation film for OLEDs.