TY - JOUR
T1 - The role of transition metal oxides in chargegeneration layers for stacked organic light-emitting diodes
AU - Hamwi, Sami
AU - Meyer, Jens
AU - Kröger, Michael
AU - Winkler, Thomas
AU - Witte, Marco
AU - Riedl, Thomas
AU - Kahn, Antoine
AU - Kowalsky, Wolfgang
PY - 2010/6/9
Y1 - 2010/6/9
N2 - The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs2CO 3doped 4,7-diphenyl-1,10-phenanthroline layer and a WO3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance - current density - voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5 nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO3 layer and its neighboring hole-transport material, 4, 4', 4'-tris(N-carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED.
AB - The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs2CO 3doped 4,7-diphenyl-1,10-phenanthroline layer and a WO3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance - current density - voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5 nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO3 layer and its neighboring hole-transport material, 4, 4', 4'-tris(N-carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED.
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U2 - 10.1002/adfm.201000301
DO - 10.1002/adfm.201000301
M3 - Article
AN - SCOPUS:77952975311
SN - 1616-301X
VL - 20
SP - 1762
EP - 1766
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 11
ER -