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. 2015 Oct 6:5:14822.
doi: 10.1038/srep14822.

Microfluidic White Organic Light-Emitting Diode Based on Integrated Patterns of Greenish-Blue and Yellow Solvent-Free Liquid Emitters

Naofumi Kobayashi  1 , Takashi Kasahara  1 , Tomohiko Edura  2 , Juro Oshima  3 , Ryoichi Ishimatsu  4 , Miho Tsuwaki  1 , Toshihiko Imato  4 , Shuichi Shoji  1 , Jun Mizuno  5
Affiliations

Microfluidic White Organic Light-Emitting Diode Based on Integrated Patterns of Greenish-Blue and Yellow Solvent-Free Liquid Emitters

Naofumi Kobayashi et al. Sci Rep. .

Abstract

We demonstrated a novel microfluidic white organic light-emitting diode (microfluidic WOLED) based on integrated sub-100-μm-wide microchannels. Single-μm-thick SU-8-based microchannels, which were sandwiched between indium tin oxide (ITO) anode and cathode pairs, were fabricated by photolithography and heterogeneous bonding technologies. 1-Pyrenebutyric acid 2-ethylhexyl ester (PLQ) was used as a solvent-free greenish-blue liquid emitter, while 2,8-di-tert-butyl-5,11-bis(4-tert-butylphenyl)-6,12-diphenyltetracene (TBRb)-doped PLQ was applied as a yellow liquid emitter. In order to form the liquid white light-emitting layer, the greenish-blue and yellow liquid emitters were alternately injected into the integrated microchannels. The fabricated electro-microfluidic device successfully exhibited white electroluminescence (EL) emission via simultaneous greenish-blue and yellow emissions under an applied voltage of 100 V. A white emission with Commission Internationale de l'Declairage (CIE) color coordinates of (0.40, 0.42) was also obtained; the emission corresponds to warm-white light. The proposed device has potential applications in subpixels of liquid-based microdisplays and for lighting.

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Figures

Figure 1
Figure 1. Concept of the microfluidic WOLED.
Greenish-blue and yellow liquid emitters are alternately injected into the integrated microchannels, and white-light emission can be generated by the simultaneous emissions of the two different color emitters.
Figure 2
Figure 2
(a) Molecular structure of the employed materials. PLQ was used as the greenish-blue emitter and the host material. TBRb was used as the yellow fluorescent guest emitters. (b) Design of the microfluidic WOLED. Twelve SU-8 microchannels were sandwiched between the anode substrate and the cathode substrate. (c) Fabrication process of the microfluidic WOLED. Anode and cathode electrodes were patterned; subsequently, microchannels were fabricated by photolithography. Finally, two substrates were bonded with APTES- and GOPTS-SAMs.
Figure 3
Figure 3
(a) PL spectrum of PLQ and 2wt% TBRb-doped PLQ, and absorption spectrum of 33.3 μM TBRb. (b) EL spectra of PLQ and 2wt% TBRb-doped PLQ with the microfluidic OLED. Inset: EL emissions of PLQ and TBRb-doped PLQ, and the sum of EL spectra of PLQ and 2wt% TBRb-doped PLQ under an applied voltage of 100 V.
Figure 4
Figure 4
(a) J-V and (b) L-V characteristics of 6-μm-thick microfluidic OLED with PLQ and TBRb-doped PLQ, respectively. Inset: Energy diagram of TBRb-doped PLQ.
Figure 5
Figure 5
(a) Photographic image of the microfluidic WOLED under a 365-nm UV irradiation. (b) EL spectrum of the microfluidic WOLED under an applied voltage of 100 V. (c) CIE coordinates of the microfluidic OLEDs with PLQ and TBRb-doped PLQ, and the microfluidic WOLED.
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