The effect of a benzimidazole derivative(TPBI)electron injection layer(EIL)on the performance of Alga based organic light-emitting devices(OLEDs)with a Cs2C03/Al cathode is investigated.An increasing current density from 71.9mA/cm2 to 188.3mA/cm2, and an enhanced electroluminescence(EL)efficiency from 3.2cd/A to 3.64 cd/A at 9 V are found when a thin TPBI layer(5 nm)is inserted at the Alga/Cs2 C03 interface.After further increasing the TPBI thickness to 10 run, OLEDs display a further increase in EL efficiency to 4.53cd/A.Our experiment suggests that the TPBI thin layer at the Alga/Ca2C03 interface facilitates the electron injection and is also involved with hole-blocking and exciton confinement.