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Investigation on internal electric field distribution of organic light‐emitting diodes (OLEDs) with Eu 2 O 3 buffer layer
Author(s) -
Shi Shengwei,
Ma Dongge
Publication year - 2009
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.200925114
Subject(s) - oled , electroluminescence , materials science , thermionic emission , optoelectronics , electric field , layer (electronics) , indium tin oxide , europium , buffer (optical fiber) , diode , quantum tunnelling , schottky diode , field electron emission , luminescence , electron , nanotechnology , electrical engineering , physics , engineering , quantum mechanics
We have found that organic light‐emitting diode (OLED) performance was highly improved by using europium oxide (Eu 2 O 3 ) as a buffer layer on indium tin oxide (ITO) in OLEDs based on tris‐(8‐hydroxyquinoline) aluminium (Alq 3 ), which showed low turn‐on voltage, high luminance, and high electroluminescent (EL) efficiency. The thickness of Eu 2 O 3 generally was 0.5–1.5 nm. We investigated the effects of Eu 2 O 3 on internal electric field distributions in the device through the analysis of current–voltage characteristics, and found that the introduction of the buffer layer balanced the internal electric field distributions in hole transport layer (HTL) and electron transport layer (ETL), which should fully explain the role of the buffer layer in improving device performance. Our investigation demonstrates that the hole injection is Fowler–Nordheim (FN) tunnelling and the electron injection is Richardson–Schottky (RS) thermionic emission, which are very significant in understanding the operational mechanism and improving the performance of OLEDs.