锂喹啉配合物作为电子注入层对有机电致发光器件性能的影响

利用锂喹啉配合物(8-hydroxy-quinolinato lithium，Liq)作电子注入层，制备了结构为氧化铟锡／锂喹啉配合物铝{ITO(indium tin oxidc) TPD(N，N′-di-phenyl-N，N′-bis(3-mmethylphenyl)-l.l′biphenyl-4，4′diamine)/Alq3tris-8-hydroxy-quinolinato)aluminum] Liq AI的电致发光器件。通过改变电子注入层Liq的厚度，考查了Liq厚度对器件电致发光效率及电流密度-电压关系的影响。实验表明Liq厚度大约为0．5nm左右时器件的性能最佳、电致发光效率约为没有Liq器件效率的5倍，而定电流下的工作电压最低，其原因可归于Liq在金属铝电极与有机层Alqs之间产生偶极层，使铝与有机层间的界面接近欧姆接触，从而使电子注入效率大幅提高；随着Liq厚度的增加，器件的电致发光效率降低，而定电流下的工作电压升高，与同类型以LiF作注入层的器件相比，这种器件性能受厚度影响而变化的趋势是类似的，但以Liq作注入层的器件具有较低的厚度敏感性，这是由于LiF为绝缘体，而Liq为半导体的缘故。Liq作注入层器件的这种对注入层厚度的不敏感性对批量生产中所用的大尺寸基底来说是非常有利的。

Effect of Liq as an Electron Injection Layer on Organic Electroluminescent Devices

Devices with a structure of ITO(indium tin oxide)/TPD(N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine)/Alq3tris-(8-hydroxy-quinolinato) aluminum)/Liq(8-hydroxy-quinolinato lithium)/Al, here Liq was used as an electron injection layer,were investigated. Effect of Liq thickness on the electroluminescent efficiency and characteristics of current density-voltage was investigated. Experimental results show that a device with 0.5 nm thick Liq as an electron injection layer was the highest in the efficiency which was about five times higher than that without Liq. This may be attributed to the enhancement of electron injection from the introduction of Liq, which generate a dipole layer and form an ohmic contact between aluminum electrode and Alq3 organic layer. Increase the thickness of Liq layer leads to the decrease of device efficiency and the increase of operating voltage. Comparing with same structure devices using LiF as an injection layer, the trend of change of device performance with the thickness increase of injection layer was similar, however the devices using Liq as an injection layer are less sensitive to the thickness of injection layer. This is because that LiF is an insulator and Liq is a semiconductor. This is very important for use of a large size substrate in the mass production.