Improved property in organic light-emitting diode utilizing two Al/Alq3 layers

We reported on the fabrication of organic light-emitting devices (OLEDs) utilizing the two Al/Alq"3 layers and two electrodes. This novel green device with structure of Al(110nm)/tris(8-hydroxyquinoline) aluminum (Alq"3)(65nm)/Al(110nm)/Alq"3(50nm)/N,N'-dipheny1-N, N'-bis-(3-methy1phyeny1)-1, 1'-bipheny1-4, 4'-diamine (TPD)(60nm)/ITO(60nm)/Glass. TPD were used as holes transporting layer (HTL), and Alq"3 was used as electron transporting layer (ETL), at the same time, Alq"3 was also used as emitting layer (EL), Al and ITO were used as cathode and anode, respectively. The results showed that the device containing the two Al/Alq"3 layers and two electrodes had a higher brightness and electroluminescent efficiency than the device without this layer. At current density of 14mA/cm^2, the brightness of the device with the two Al/Alq"3 layers reach 3693cd/m^2, which is higher than the 2537cd/m^2 of the Al/Alq"3/TPD:Alq"3/ITO/Glass device and the 1504.0cd/m^2 of the Al/Alq"3/TPD/ITO/Glass. Turn-on voltage of the device with two Al/Alq"3 layers was 7V, which is lower than the others.