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17.4: A Novel Technique to Study OLED Function
Author(s) -
Sims Marc,
Venter Steven W.,
Parker Ian D.
Publication year - 2008
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 - 10.1889/1.3069629
Subject(s) - oled , anode , cathode , materials science , capacitance , voltage , population , analytical chemistry (journal) , optoelectronics , absorption (acoustics) , charge (physics) , electrode , molecular physics , chemistry , physics , nanotechnology , composite material , demography , layer (electronics) , quantum mechanics , chromatography , sociology
We employ electrically induced absorption (EIA) spectroscopy to probe the internal operation of a series of NPB/Alq 3 (1) OLED structures. Our results complement the capacitance‐voltage measurements of Brütting et al [3] and support the proposal of a fixed negative charge population at the NPB/Alq 3 interface. We show a direct signature for hole injection under reverse bias (as predicted in [3,4]) and demonstrate that the voltage onset for hole injection, V h (equivalent to transition voltage, V o in [3,4]) is largely independent of anode material. Conversely, V h appears to depend sensitively on the cathode material (an exchange of LiF/Al for CsF/Al raises V h by +0.5V). Finally, we observe a rise in V h after a prolonged period of current stress and propose that this finding originates in a gradual neutralization of the negative interfacial charge population.