Low-temperature Remote Plasma Enhanced Atomic Layer Deposition Of Thin Film Encapsulation For Flexible Organic Light-emitting Diodes

Organic light-emitting device(OLED)have attracted considerable attention because of their advantages,including wide color gamut,wide viewing angle,high contrast,fast response time,low cost,low power consumption and mechanical flexibility.However,the process of OLED is still facing many urgent difficulties in industrial production.One of the most important issue is that the organic materials and metal cathode in OLED is easily damaged by water vapor(H2O)and oxygen(O2)in the air.The aim of this study is finding a solution of the key issues of flexible OLED encapsulation.Thin film encapsulation(TFE),in which the with directly deposited barrier films onto a flexible electronics and has been performed with various deposition techniques,such as remote plasma enhanced atomic layer deposition(PEALD).In our work,zirconium dioxide(ZrO2)films deposited with PEALD have been widely investigated.The zircone prepared with the technology of molecular layer deposition(MLD)to obtain high gas-barrier nanolaminate encapsulation film.The surface reaction mechanisms of ZrO2 film were studied using an in-situ quadrupole mass spectroscopy(QMS)and in-situ quartz crystal microbalance(QCM).The primary reaction byproducts in PEALD,such as H2 O,CO,NO and CO2 during the O2 plasma process were detected using the QMS,indicating a combustion-like reaction process.The self-limiting property and growth mechanisms of the ZrO2 during the complex surface chemical reaction of the ligand and O2 plasma were monitored via the QCM.Interestingly,it was first demonstrated that the-CN group gave rise to cut-off phenomenon at high temperature.Several reaction pathways were accordingly established.The present work initiates a new way of achieving controlled growth properties of ZrO2 thin films.To optimize the encapsulation properties for OLED,a new group of hybrid inorganic/organic films known as “ZrO2/zircone” was investigated.The ZrO2 ALD and zircone MLD alloy TFEs were fabricated using the remote PEALD method at a low deposition temperature(80°C).It was found that the morphology of the film turn to smooth as the number of the zircone layer become denser.And the water vapor transmission rate(WVTR)and the lifetime of the four different structures have been test in the view of films qualification.The WVTR of the films could reach to 3.08×10-5g.m-2.day-1.The continuous lighting time is 182 hours using PET substrate,this phenomenon indicates that the ultrathin thin films of zircone blocked the pin-hole in the film,furthermore,prolonged the path of H2 O and O2 through the bulk ZrO2.Because of such low permeation rates,low process temperature,and its mechanical compatibility,the organic/inorganic nanolaminate improved protection for flexible organic electronic devices.