Efficient Organic Light-Emitting Diodes with ZnS Thin Films as Hole Buffer Layer

An organic light-emitting diodes (OLEDs) using ZnS thin film by RF magnetron sputtering as a hole buffer layer were prepared. With the presence of the buffer layer, the devices using the typical structure of ITO/TPD/Alq/LiF/Al performed a good electroluminescent properties compared with the devices without ZnS buffer layer. The investigation on the effects of the ZnS thickness showed that the device with 5 nm ZnS buffer layer double its luminance under driven voltage 20 V, and the current efficiency of the devices with 5 and 10 nm ZnS is improved by about a factor of forty percent compared with the devices without buffer layer. The results suggested that ZnS may be a good anode buffer layer material and can improve the efficiency and stability of OLEDs.