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33.3: Invited Paper: OLEDs with Doped Transport Layers for Highly Efficient Displays
Author(s) -
Pfeiffer Martin,
Zhou Xiang,
Huang Jingsong,
Leo Karl,
BlochwitzNimoth Jan
Publication year - 2003
Publication title -
sid symposium digest of technical papers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.351
H-Index - 44
eISSN - 2168-0159
pISSN - 0097-966X
DOI - 10.1889/1.1832474
Subject(s) - oled , optoelectronics , materials science , doping , ohmic contact , anode , dopant , substrate (aquarium) , diode , brightness , nanotechnology , electrode , optics , layer (electronics) , chemistry , oceanography , physics , geology
In this paper, we discuss recent experiments which prove that evaporated organic films can be efficiently doped by coevaporation with dopant molecules. Key advantages for devices are the high conductivity and the formation of ohmic contacts despite large energetic barriers. Organic light emitting diodes (OLEDs) with electrically doped transport layers show significantly improved properties: For instance, we have achieved a brightness of 100Cd/m 2 already at a voltage of 2.55V, well below previous results for undoped small‐molecule devices. The advantages of doping are even more pronounced for top‐emitting, inverted OLED structures: Due to the ohmic contacts nearly independent of the contact properties, it is possible to realize inverted top‐emitting devices with parameters comparable to standard devices. Also, it is possible to deposit ITO anodes on such devices without significant sputter damage since the active regions of the device are protected by thick doped transport layers. Our doping technology is thus a significant advantage for active‐matrix OLED displays and other displays on opaque substrate.