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Efficient Polymer Electrophosphorescent Devices with Interfacial Layers
Author(s) -
Yang X. H.,
Jaiser F.,
Stiller B.,
Neher D.,
Galbrecht F.,
Scherf U.
Publication year - 2006
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200500834
Subject(s) - pedot:pss , materials science , polymer , luminous efficacy , phosphorescence , quantum efficiency , homo/lumo , styrene , energy conversion efficiency , optoelectronics , annealing (glass) , electroluminescence , layer (electronics) , chemical engineering , composite material , copolymer , molecule , optics , organic chemistry , fluorescence , chemistry , physics , engineering
Abstract It is shown that several polymers can form insoluble interfacial layers on a poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layer after annealing of the double‐layer structure. The thickness of the interlayer is dependent on the characteristics of the underlying PEDOT:PSS and the molecular weight of the polymers. It is further shown that the electronic structures of the interlayer polymers have a significant effect on the properties of red‐light‐emitting polymer‐based electrophosphorescent devices. Upon increasing the highest occupied molecular orbital and lowest unoccupied molecular orbital positions, a significant increase in current density and device efficiency is observed. This is attributed to efficient blocking of electrons in combination with direct injection of holes from the interlayer to the phosphorescent dye. Upon proper choice of the interlayer polymer, efficient red, polymer‐based electrophosphorescent devices with a peak luminance efficiency of 5.5 cd A –1 (external quantum efficiency = 6 %) and a maximum power‐conversion efficiency of 5 lm W –1 can be realized.