Exploratory Study On The Fabrication Of Organic Electroluminescent Devices Under Non-vacuum

Organic Light-Emitting Devices(OLEDs)have self-illumination,strong contrast,wide color gamut,wide viewing angle,fast response,and low power consumption.So far,the vacuum evaporation technology of OLEDs has been quite mature and industrialized,and full-color displays of various sizes of OLEDs have been launched.However,the ultra-high vacuum evaporation equipment used in this technology is expensive,and it is necessary to continuously provide a circulating cooling system,and the material waste is serious,resulting in high cost of current OLEDs products.Therefore,the development of technologies for preparing OLEDs under all nonvacuum can completely avoid the vacuum evaporation,thereby greatly reducing the production cost of OLEDs products and achieving large-area production,which has great application potential in the future and solid-state lighting.In order to prepare OLEDs devices under non-vacuum conditions,researchers have conducted a lot of research,and solution method preparation is the main research direction.Solving the problem of mutual solubility of solution OLEDs is the basis for non-vacuum preparation of OLEDs.Therefore,this thesis firstly studied the method of using polyethyleneimine(PEI),a polymer material,as an interface layer in OLEDs prepared by inverted solution method to solve the problem of mutual solubility between different functional layers.We systematically studied the morphology,electrical properties and photoluminescence of PEI films.The results show that in the inverted OLEDs,the insertion of the double PEI interface layer between the luminescent layer,the electron transport layer and the electron injection layer prepared by the solution method can prevent the mutual solubility between the functional layers while ensuring the electron transporting ability.Finally,we achieved a double PEI interfacial layer of high performance green OLEDs prepared by solution method,which achieved a current efficiency of up to 45.2 cd/A,and its current efficiency is close to that of the device prepared by vacuum evaporation.Secondly,in the related research on non-vacuum preparation of OLEDs,the preparation of OLEDs bottom electrode under non-vacuum is also a difficult problem.In this thesis,a novel silver nanowire(AgNWs)-MEH-PPV composite flexible electrode is proposed,which can be fabricated into a composite electrode by embedding photoelectric polymer material MEH-PPV into AgNWs by physical external force,which can realize non-vacuum preparation of flexible OLEDs bottom electrode.It also has the function of color conversion of OLEDs,which can be used for flexible white OLEDs devices with full non-vacuum preparation.We systematically studied the effects of parameters such as pressure,temperature and pressing time on the electrode properties during the preparation process,obtained the optimal preparation parameters,and studied the surface morphology and photophysical properties of the composite electrode.The sheet resistance of the AgNWs-MEH-PPV flexible composite electrode prepared under the optimal conditions is only 22.1 ?/sq,which is close to the commonly used ITO electrode,but its bending performance is far superior to that of ITO.If it is used instead of flexible ITO electrode for flexible OLEDs will greatly improve the bending performance of the device.Finally,this thesis studies a flexible white OELDs device based on AgNWs-MEHPPV multifunctional flexible composite electrode.The flexible white OLEDs fabricated by vacuum evaporation on the composite electrode exhibit high efficiency of cold white light emission,current efficiency of 20.5 cd/A,color temperature of about 8662 K,CIE coordinates of(0.279,0.324),and excellent The color stability and color temperature can be modulated by simply changing the thickness of the color conversion layer,and the sunlight and warm white light can be modulated.Subsequently,based on the first two tasks,this paper combines the AgNWs-MEH-PPV multifunctional flexible composite electrode and the organic functional layer processed by the solution method to realize the flexible white OLEDs device with excellent color stability prepared in non-vacuum.It provides a reliable idea for the study of high efficiency,high stability non-vacuum processing OLEDs.Because the series of devices are processed by lowcost solution method,it is easy to combine the inkjet printing technology on the production line and the solution processing technology such as roll-to-roll processing,which will help to realize low-cost,large-area production of flexible white light in the industry in the future OLEDs devices.