Influence of Thickness of Hole Transport Layer on Performance of OLED

Based on a spinning polymer layer of poly (N-vinylcarbazole) (PVK) as Hole Transport Layer (HTL) and an evaporated layer of tris (8-hydroxy) quinoline aluminum (Alq3) as Electron Transport Layer (ETL) and Emissive Layer (EL), Organic Light-Emitting Diodes (OLEDs) with the structure of ITO/PVK (0~60 nm)/Alq3(60 nm)/Mg:Ag/Al were fabricated. By measuring and analyzing the current-voltage-luminance characteristics, influences of the thickness of HTL on devices performance was investigated. Experimental results show that optical and electrical properties of the devices are closely related to the thickness of HTL and the device with a layer of HTL 15 nm has the best performances, i.e. the lowest turn-on voltage, highest luminance and maximal luminous efficiency.