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Proceedings Paper

Improvement of operation voltage and efficiency in inverted blue phosphorescent organic light-emitting devices
Author(s): Chih-Hao Chang; Hao Siang Huang; Yu-De Su; Yi-Hu Liang; Yu-Shuo Chang; Chuan-Hao Chiu; Hsin-Hua Chang
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Paper Abstract

Inverted organic light-emitting diodes (IOLEDs) have drawn considerable attention for use in active-matrix OLED (AMOLED) displays because of their easy integration with n-channel metal-oxide-based thin film transistors (TFTs). The most crucial issue for IOLEDs is the poor electron injection caused by the bottom cathode. According to previous reports, the turn-on voltages of FIrpic-based IOLEDs are within a range from 4 to 8 V. In this study, we focus on developing bottom-emission IOLEDs with low operating voltages through the use of adequate-charge injection materials. We successfully demonstrate a turn-on voltage as low as 3.7 V for blue phosphorescent IOLEDs. The effective electron injection layers (EIL) were constructed by combining an ultrathin aluminum layer, an alkali metal oxide layer and an organic layer doped with alkali metal oxide, allowing for the effective adjustment of the carrier balance in IOLEDs. The peak efficiencies of the IOLEDs reached 15.6%, 31.8 cd/A and 23.4 lm/W. An external nanocomposite scattering layer was used to further improve light extraction efficiency. The IOLEDs equipped with the SiO2 nanocomposite scattering layer respectively provided performance improvements of 1.3 and 1.5 times that of pristine blue phosphorescent IOLEDs at practical luminance levels of 100 cd/m2 and 1000 cd/m2. Through sophisticated EIL and external light-extraction structures, we obtained blue phosphorescent IOLEDs with satisfactory efficiency and low operation voltages, thereby demonstrating the great potential of nanocomposite film for application in IOLEDs.

Paper Details

Date Published: 27 September 2013
PDF: 8 pages
Proc. SPIE 8829, Organic Light Emitting Materials and Devices XVII, 88291W (27 September 2013); doi: 10.1117/12.2023130
Show Author Affiliations
Chih-Hao Chang, Yuan Ze Univ. (Taiwan)
Hao Siang Huang, Yuan Ze Univ. (Taiwan)
Yu-De Su, Yuan Ze Univ. (Taiwan)
Yi-Hu Liang, Yuan Ze Univ. (Taiwan)
Yu-Shuo Chang, Yuan Ze Univ. (Taiwan)
Chuan-Hao Chiu, Yuan Ze Univ. (Taiwan)
Hsin-Hua Chang, Vanung Univ. (Taiwan)

Published in SPIE Proceedings Vol. 8829:
Organic Light Emitting Materials and Devices XVII
Franky So; Chihaya Adachi, Editor(s)

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