Electroluminescence performance of organic light-emitting diode with molybdenum trioxide inside hole transport layer

A new structure of organic light-emitting diode (OLED) was fabricated by inserting a thin molybdenum trioxide (MoO3) layer into hole transport layer (HTL) N,N'-diphenyl-N,N'-bis(1-napthyl-phenyl)-1,1'-biphenyl-4,4'-diamine (NPB). The device structure is ITO/NPB(10 nm)/MoO3(3 nm)/NPB (30 nm)/tris-(8-hydroxyquinoline) aluminum (Alq(3)) (60 nm)/LiF(0.5 nm)/Al. The control device is set without MoO3 interlayer. The driving voltage at 100 cd/m(2) is only 4.87 V corresponding to the device with MoO3 interlayer, which is much lower than the control device of 6.40 V. The novel device also shows higher power efficiency compared to the control device. The improvement of device performance is attributed to the Charge Transfer complex (CT complex), generated at the NPB/MoO3/NPB interfaces, contributing here as hole transfer enhancer. Our finding additionally demonstrates the practical applicability of MoO3 as a buffer layer in OLEDs.