Recovery of electroluminescence in electron-only organic light-emitting diode by inserting a thin MoO3 layer at Bphen/NPB interface

An electron-only device was realized by using 20 nm Bphen layer to modify ITO anode in NPB/AlQ3 heterojunction organic light-emitting diode (OLED). Different from the usual application as an anode buffer layer, up to 10 nm thick MoO3 layer was inserted at Bphen/NPB interface to recover the electroluminescence (EL). Interfacial charge generation and transport are suggested as the mechanism of such luminescence recovery. Experimental results showed that mobile holes generated in NPB transported to NPB/AlQ3 interface, resulting in light-emitting, while electrons in MoO3 transported to ITO anode through Bphen layer under continuous current condition. The suggested mechanism explains how inserted MoO3 layer modifies Bphen/NPB interface.