Highly efficient and bright electroluminescent Ru(bpy)3(ClO4)2∕Alq3 device

Abstract

Electroluminescent devices of indium tin oxide ( ITO ) ∕ Al q 3 ( 212 nm ) ∕ Ru ( bpy ) 3 ( Cl O 4 ) 2 ( 100 nm ) ∕ Ga : In were fabricated and showed high external quantum and power efficiencies, of 6.4% and 5.3%, respectively, at an optical output power of 0.4 mW ∕ cm 2 under a bias of 2.3 V. At a higher bias voltage ( > 2.7 V ) , the output power was well above 10 mW ∕ cm 2 , but with a lower efficiency. Light emission occurred at the interface between Al q 3 and Ru ( bpy ) 3 ( Cl O 4 ) 2 , whose relative energies of both excited and ground states were offset, ideal for confining both charge carriers and minimizing the quenching of the Ru ( bpy ) 3 2 + excited state. By comparison, in a single layer device without Al q 3 , the emission zone was located at the ITO interface where excited states were quenched and electron injection from the reduced molecules to the ITO contact produced a unipolar current and thus lower efficiency.