Studies of Electroluminescent Characteristics of Quantum Well Green Organic Light Emitting Diodes

Abstract

The electroluminescence (EL) characteristics are studied in organic light emitting diodes consisting of the emitting layer of tris(8-hydroxyquinolinato)-aluminum (Alq₃) and the hole transporting layer of the type-II quantum well (QW) structure with 4,4′,4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA)/4,4′-bis[N-(naphthyl)-N-phenyl-amino]biphenyl (α-NPD) as the quantum well/quantum wall. The EL spectra show a blue shift, around 10 nm compared with the reference device without the QW structure, as the number and thickness of quantum well and the current density increase. The luminescence can be controlled by 25% with the number of quantum wells and 20% with the thickness of the quantum well. The improvement of luminescence and the blue shift in the EL spectrum can be explained by the confinement of holes in the QW and the shifting of emitting zone.

Keywords:

• Emitting zone
• exciton
• OLED
• quantum well structure

Acknowledgments

This work was supported by the Ministry of Knowledge Economy (MKE), Korea and the BK21 project of the Ministry of Education, Science, and Technology (MEST), Korea.