Details

Autor(en) / Beteiligte

• Meerheim, Rico
• Scholz, Sebastian
• Olthof, Selina
• Schwartz, Gregor
• Reineke, Sebastian
• Walzer, Karsten
• Leo, Karl

Titel

Influence of charge balance and exciton distribution on efficiency and lifetime of phosphorescent organic light-emitting devices

Ist Teil von

• Journal of applied physics, 2008-07, Vol.104 (1), p.014510-014510-8

Ort / Verlag

American Institute of Physics

Erscheinungsjahr

2008

Quelle

American Institute of Physics

Beschreibungen/Notizen

• We discuss the importance of appropriate charge carrier confinement and exciton management for the realization of highly efficient and stable organic light-emitting diodes (OLEDs). As an example, we choose red p - i - n -type OLEDs based on the iridium-based electrophosphorescent emitter Ir ( MDQ ) 2 ( acac ) doped in α -NPD as host material. We show how an appropriate choice of the hole blocking layer material allows external quantum efficiencies as high as 20% for this emitter. At the same time, the display-relevant brightness of 100   cd / m 2 is reached at an operation voltage of only 2.4 V, which is close to the thermodynamic limit. As a result, a high total power efficiency of 37.5   lm / W at 100   cd / m 2 is reached. In a further step, we study the influence of the blocker materials on device lifetime. We investigate the chemical reactions causing the degradation process by use of matrix assisted laser desorption time-of-flight mass spectrometry. It can be shown that discovered degradation reactions can be suppressed by an appropriate choice of the hole blocking material.