Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-06T05:04:54.735Z Has data issue: false hasContentIssue false

Low Frequency Noise Correlation between Electrical and Optical Signals for Predicting Degradation in Organic Light Emitting Diodes

Published online by Cambridge University Press:  31 January 2011

Soo Jin Chua
Affiliation:
[email protected], Institute Of Materials Research and Engineering, Materials Growth, Singapore, Singapore
Sha Huang
Affiliation:
[email protected], NUS, Singapore, Singapore
Lin Ke
Affiliation:
[email protected], IMRE, Singapore, Singapore
Get access

Abstract

The Low Frequency Noise (LFN) characteristics of Organic Light Emitting Diodes (OLEDs) were investigated in relation to device degradation. The standard layer structure of indium tin oxide (anode), hole transport layer, Alq3, Lithium Fluoride and Aluminium (cathode) was used. With duration of operation, the device degradation is characterized by an eventual drop in the luminance level and the electroluminescence efficiency. Additionally, the driving voltage at a fixed current and the LFN increase gradually during device degradation, accompanied with the formation of non-emissive areas (dark spots). It is found that the coefficient of correlation between voltage fluctuations across the device and low frequency fluctuations of the optical signals remains constant for an initial period and then decreases exponentially with duration of operation and is a sensitive parameter to predict OLED device lifetime. For a number of OLEDs driven at constant current, the device with higher initial correlation coefficient possesses a longer lifetime. The direct relation between LFN correlation and device lifetime can be explained by carrier recombination mechanisms at the microscopic level. An increase in trap density can reduce the internal radiative recombination rate which at the macroscopic level is reflected by a decrease in the correlation coefficient.

Type
Research Article
Copyright
Copyright © Materials Research Society 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

[1] Lim, Shuang Fang, Wang, Wei, Chua, Soo Jin, “Degradation of organic light-emitting devices due to formation and growth of dark spotMaterials Science and Engineering B85 (2001) 154159 10.1016/S0921-5107(01)00599-2Google Scholar
[2] Ke, Lin, Zhao, Xin Yue, Kumar, Ramadas Senthil, and Chua, Soo Jin, “Low Frequency Noise Measurement and Analysis in Organic Light-Emitting Diodes”, IEEE Device Letters, Vol. 27, No.7 (2006)Google Scholar
[3] Kaulakys, B., “On the intrinsic origin of 1/f Noise”, Microelectronics Reliability 40 (2000)10.1016/S0026-2714(00)00055-XGoogle Scholar
[4] Hooge, F.N., “1/f Noise Sources”, IEEE Transaction on Electron Devices, Vol.41, No.11 Google Scholar