Berlin 2005 – wissenschaftliches Programm

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.5: Poster

Montag, 7. März 2005, 18:00–20:00, Poster TU A

High-efficiency p-i-n electrophosphorescent organic light-emitting diodes without blocking layers — •Gufeng He, Karsten Walzer, Martin Pfeiffer, and Karl Leo — IAPP, TU Dresden, D-01062 Dresden, Germany

By using high conductive p- and n-doped organic materials as charge injection layers in organic light-emitting diodes (OLEDs), low operating voltage and ultra-high power efficiency have been reached. It is also very important to simplify the manufacture process in production of OLEDs. Here we have successfully removed either hole-blocking layer (HBL) or electron-blocking layer or both in our double-emission layer (D-EML) OLEDs without efficiency loss and lifetime drop. The D-EML comprises two emission layers with ambipolar transport characteristics, both doped with the green phosphorescent dye tris(phenylpyridine)iridium [Ir(ppy)3]. An important feature of the D-EML structure is its self-balancing character being not based on abrupt barriers, but on rather smooth transitions between regions with different mobility for the charge carriers. Both electrons and holes are gradually slowed down in the emission layer, and are likely to recombine before reaching the high barrier to the corresponding blocking layers. Hence, the blocking layers are less critical in D-EML structure than in other structures. A power efficiency of 80 lm/W is obtained at 100 cd/m2 without HBL.