Special Section on Organic Light-Emitting Materials and Devices

Organic light-emitting diodes with roll-up character

[+] Author Affiliations
Jwo-Huei Jou

National Tsing Hua University, Department of Materials Science and Engineering, Taiwan 30013, Taiwan

Pin-Chu Chen, Ming-Chun Tang, Yi-Shan Wang, Chun-Hao Lin

National Tsing Hua University, Department of Materials Science and Engineering, Taiwan 30013, Taiwan

Szu-Hao Chen, Chien-Chih Chen, Ching-Chiun Wang

Mechanical and Systems Research Laboratories Industrial Technology Research Institute, Taiwan 31040, Taiwan

Chien-Tien Chen

National Tsing Hua University, Department of Chemistry, Taiwan 30013, Taiwan

J. Photon. Energy. 2(1), 021208 (Mar 19, 2012). doi:10.1117/1.JPE.2.021208
History: Received September 30, 2011; Revised January 25, 2012; Accepted February 14, 2012
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Abstract.  Highly efficient organic light-emitting diodes (OLEDs) are strongly demanded for both display and illumination applications. High efficiency would also help prolong the device lifespan. However, many OLEDs encounter significant roll-off problems, leading to undesired low device efficiency at high luminance, which is unfavorable to their commercial realization for lighting. Hence, OLED devices with mild or even little roll-off are highly expected. We have, nevertheless, observed some OLEDs that exhibit roll-up phenomenon, i.e., that their external quantum efficiency (EQE) or current efficiency increases as the applied voltage or brightness is increased. By taking such advantage of device architecture design, OLEDs with an approaching or even above the theoretical limit EQE are obtained at high luminance. In this report, we present how this works for a yellow OLED that exhibits a record-high power efficiency among reported fluorescent yellow OLEDs, a very-low color temperature OLED with a record-breaking efficacy based on the same color-temperature, and a green OLED. Notably, the yellow OLED exhibits an EQE that increases from 5.4 to 6.2% and current efficiency from 16.4 to 18.7cd/A as the luminance increases from 1000 to 10,000cd/m2. Plausible mechanisms regarding why roll-up occurs in these devices are discussed.

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© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Jwo-Huei Jou ; Pin-Chu Chen ; Ming-Chun Tang ; Yi-Shan Wang ; Chun-Hao Lin, et al.
"Organic light-emitting diodes with roll-up character", J. Photon. Energy. 2(1), 021208 (Mar 19, 2012). ; http://dx.doi.org/10.1117/1.JPE.2.021208


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