Aluminum-doped Zinc Oxide Transparent Electrode For Organic Light Emitting Devices

Transparent conductive oxide?TCO?film is an extremely important functional material in the field of photovoltaic device industry and photoelectric material research,it promotes the rapid development of flat display,solid-state lighting and other industries.Indium tin oxide?ITO?film is one of the most widely used TCO materials,but many factors such as expensive raw materials,toxic and environmental pollution are important issues that restrict the development of ITO film.Al-doped ZnO?AZO?film has similar photoelectric properties to ITO film,it has the advantages of low price,good photoelectric performance,environmental protection and non-toxicity.It is considered to be the most promising potential for replacing ITO.Firstly,the research background,basic structure,photoelectric properties and application status of AZO thin films are introduced as the basis of this study.Then AZO transparent conductive film was prepared by atomic layer deposition?ALD?method at 150°C.The doping ratio and deposition parameters of the film were optimized during the research,which improved the film formation quality and shortened the preparation.At the same time,the surface morphology and photoelectric properties of the prepared films were characterized.In the work of preparing AZO thin films by ALD method reported in the past,most of the research focuses on the effects of exposure time of precursors and reactants on the properties of thin films.Less attention has been paid to how the purge conditions change the morphology,optical properties,and electrical properties of AZO films,because it is generally believed that all ALD purge times result in films with the same properties.In this work,we first studied the relationship between different H₂O purge times and the properties of films grown by ALD,in the process of preparing AZO thin films by ALD,the crystal orientation and conductivity are changed by changing the purge time of H₂O.An optimized AZO electrode,which had an Al:Zn mole ratio of 1:49,was prepared with a 20 s H₂O purge time.The film had a low resistivity?1.25 m?cm±0.2 m?cm?,a high transmittance?83.2%at 550 nm?and a high work function of 4.7 eV.This study provides new insights into the relationship between AZO transparent conductive films prepared by ALD and H₂O purge times.An classic organic light-emitting device?OLED?with MoO₃/m-MTDATA/NPB/Alq/LiF/Al structure was fabricated on a glass substrate using the optimized AZO anode,it compares performance with OLED devices with ITO as anode,and a maximum current efficiency of 3.9cd/A was achieved.These results indicate that such a method of preparing a transparent conductive film by ALD can be used to prepare anodes for OLEDs.