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Reliability Study of Organic Light-emitting Diodes by Continuous-wave and Pulsed Current Stressing

Published online by Cambridge University Press:  16 June 2015

X. M. Li
Affiliation:
Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA
R. Acharya
Affiliation:
Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA
Y. Q. Zhang
Affiliation:
Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA
X. A. Cao
Affiliation:
Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA
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Abstract

The stability of green phosphorescent OLEDs with different structures was evaluated through constant-current stressing. Through the modifications of the ITO anode by different plasma treatments and the hole transport layer (HTL) by incorporating inorganic dopants, we proved that energy level misalignment at the ITO/HTL interface leads to localized joule heating, accelerating defect generation and luminescence decay. Pulsed current stressing was then employed to suppress the joule-heating effect so as to differentiate the thermal and nonthermal factors governing the device degradation. For OLEDs with a large energy barrier at the ITO/HTL interface, the effective lifetime was markedly increased under pulsed operation, whereas in OLEDs with an appropriate interfacial energy level alignment, pulsed stressing with 10% duty cycle only improved the effective half life by ∼15% as compared to continuous-wave stressing, indicating a minor role played by joule heating.

Type
Articles
Copyright
Copyright © Materials Research Society 2015 

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References

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