Efficient Single-Layer Organic Light-Emitting Diodes Based on C545T-Alq3 System

We report efficient single-layer organic light-emitting diodes (OLEDs) based on 2,3,6,7-tetrahydro-1,1,7,7,-tetramethyl-1H,5H,11H-10-(2-benzothiazolyl) quinolizino-[9,9a,1gh] coumarin (C545T) and tris(8-hydroxyquinolinolato)aluminum (Alq3) system. The doping concentration, as well as nickel oxide (Ni2O3) and molybdenum oxide (MoO3)-modified indium tin oxide (ITO) anodes were investigated. With increasing doping concentration from 1 to 23%, the emission color varied from green to yellow; the Commission Internationale de l'Eclairage (CIE) coordinate changed from (0.29, 0.66) to (0.45, 0.53). The green- to yellow-emitting devices showed current efficiency from 6.4 to 4.2 cd/A for ITO/Ni2O3 anode and 12.8 to 5.5 cd/A for ITO/MoO3 anode at 100 cd/m2, respectively, which are better than 3.8 cd/A obtained in the traditional undoped three-layered device ITO/copper-phthalocyanine (CuPc)/ N,N′-diphenyl-N,N′-bis-(1-naphthyl)-1-1′-biphenyl-4,4′-diamine (α-NPD)/Alq3/LiF/Al and comparable to 14.4 cd/A in the doped device ITO/CuPc/α-NPD/C545T−Alq3 (∼1%)/Alq3/LiF/Al.