| Organic Light-Emitting Diode(OLED)provides a new efficient and feasible method for illumination and display technology due to their thinness,wide viewing angle,fast response,high brightness,and flexibility,and are replacing some of the commercial technologies,such as liquid crystal display(LCD).OLED has a wide range of commercial,medical and industrial applications.In addition,OLED also has great potential in future wearable device applications.At present,many researches are devoted to the development and application of OLED.However,in order to realize the development of flexible OLEDs for flexible wearable applications,one of the key issues is the applicability of transparent electrodes.Because it must not only have high conductivity and high transmittance(as an ordinary standard electrode),but also must have good bendability or mechanical flexibility.It is well known that Indium Tin Oxide(ITO)is the most commonly used transparent conductive film.However,due to the scarcity of its materials and its own fragility,its application in flexible OLEDs is limited.Therefore,there is an urgent need to find alternative materials for ITO to prepare transparent electrodes for flexible OLEDs.In recent decades,people have never stopped exploring flexible transparent electrodes,and developed such as metal nanowires,carbon nanotubes,graphene,conductive polymers,metal thin films and other highly potential flexible electrodes.However,these electrodes have their limitations and cannot be directly used as transparent electrodes for flexible OLEDs.For example,the internal junction of the carbon nanotube film is easily opened,which leads to a higher sheet resistance,and its insoluble in organic solution makes it unfavorable for the use of easy-to-operate solution preparation methods.For graphene materials,the peeling technology is also a major difficulty.The low conductivity of PEDOT:PSS greatly limits its application in optoelectronic devices.At the same time,the nature of silver nanowires that is easily oxidized in the air also hinders its preparation into flexible electrodes.Among these electrode materials,ultra-thin metal films are promising candidates for flexible electrodes.However,when ultra-thin metal is deposited directly on a bare substrate,the metal will follow an island-like growth pattern,forming a granular uneven surface morphology,and reducing the conductivity of the metal film.Therefore,it is necessary to prepare a nucleation induction layer that modifies the substrate before depositing the ultra-thin metal.This paper studied a novel type of nucleation induction layer for self-encapsulated ultra-thin electrodes based on atomic layer deposition technology.The nucleation induction layer PMMA/TMA was obtained by using ALD technology to introduce Trimethylaluminum(TMA)into the surface of the polymethyl methacrylate(PMMA)film and react with it.By virtue of the self-limiting reaction characteristic of ALD,the carbonyl group on the surface of PMMA was modified into highly active methyl group accurately.The functional methyl group of PMMA/TMA acted as a ligand and formed a coordination complex with Au atoms through coordination bonds,avoiding the island-like growth caused by the random migration and aggregation of Au.In addition,the pulsed TMA also filled the holes in the PMMA film,greatly reducing the water vapor transmission rate of the bare PMMA substrate,and solving the problem of poor encapsulation performance of organic polymers.In this study,the 7nm ultra-thin gold electrode prepared based on the nucleation induction layer has low sheet resistance(18.19±0.44 ?/?),high transmittance(85.89%)and flat surface morphology(root mean square was about 0.566±0.035 nm).The optical and electrical properties of flexible OLEDs based on PMMA/TMA/Au electrodes were better than conventional flexible ITO devices,and they had excellent flexibility.After being repeatedly bent 1000 times to a bending radius of 1 mm,it could still maintain 95.0% of the initial brightness. |
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