Improved Hole-Blocking and Electron Injection Using a TPBI Interlayer at the Cathode Interface of OLEDs

Abstract

The effect of a benzimidazole derivative (TPBI) electron injection layer (EIL) on the performance of Alq3 based organic light-emitting devices (OLEDs) with a Cs2CO3/Al cathode is investigated. An increasing current density from 71.9 mA/cm2too 188.3 mA/cm2, and an enhanced electroluminescence (EL) efficiency from 3.2 cd/A to 3.64 cd/A at 9 V are found when a thin TPBI layer (5 nm) is inserted at the Alq3/Cs2CO3 interface. After further increasing the TPBI thickness to 10 nm, OLEDs display a further increase in EL efficiency to 4.-53 cd/A. Our experiment suggests that the TPBI thin layer at the Alq3/Cs2CO3 interface facilitates the electron injection and is also involved with hole-blocking and exciton confinement.