利用8-羟基喹啉锂作电子注入层以提高有机发光器件的发光效率

Improve Luminance Efficiency of Organic Light Emitting Diodes with 8-Hydroxyquinolinolato-lithium as an Electron Injection Layer

8-羟基喹啉锂用作有机电致发光器件的电子注入层能够提高阴极功函数,进而提高器件的发光效率。10的Liq薄膜足以降低有机电致发光器件中的开启电压并能有效提高器件效率,该现象可与LiF/Al作阴极的器件性能相比拟。利用不同阴极材料制作器件,讨论了8-羟基喹啉锂的电子注入机制,发现把Liq薄膜引入到Alq3和不同阴极之间后,器件的电流密度与所用阴极材料的种类无关。为了讨论电子在分界面上注入势垒的变化情况,对器件进行饱和光伏测试。测试发现Alq3/Liq/Al的分界面上真空能级的移动降低了电子注入势垒。推测此现象是由于在界面上形成了强偶极子,这也可能是有机电致发光器件中电子注入效率提高的机理之一。

It has been proved that the insertion of insulating layer into between tris(8-hydroxyquinoline)aluminum(Alq3)and cathode can improve electron injection of organic light emitting diodes and then advance the efficiency of device.For improving the electron injection,we can also add some electron injection layer to device properly.In this study,we report8-hydroxyquinolinolato-lithium as an efficient electron injection layers for Alq3organic light emitting device(OLEDs)in cooperated with Al cathode.About10of thin Liq layer is enough to lower the trun-on voltage and improve the device efficiency,which is also comparable to the well established LiF/Al cathode.We investigate the electron injection mechanism for hydroxyquinolinolato-lithium using different cathode materials,and found that the improvement of electron injection in the device is irrespective of the cathode material used once a thin Liq layer is inserted between Alq3and the cathode.The improvement brought by these thin layers in cooperation with different cathodes is very similar in nature,showing that same process is responsible for the improvement of electron injection.The study has shown that there is a vacuum level shift at Alq3/Liq/Al interface lowering the HOMO-LUMO of Alq3,which may be due to a strong dipole formation at these interfaces and it is a potential mechanism for improved electron injection.