Ag nanocluster-based color converters for white organic light-emitting devices

Yoshinori Nishikitani, Daisuke Takizawa, Soichi Uchida, Yue Lu, Suzushi Nishimura, Kenichi Oyaizu, Hiroyuki Nishide

Research output: Contribution to journalArticle

Abstract

The authors present Ag nanocluster-based color converters (Ag NC color converters), which convert part of the blue light from a light source to yellow light so as to create white organic light-emitting devices that could be suitable for lighting systems. Ag NCs synthesized by poly(methacrylic acid) template methods have a statistical size distribution with a mean diameter of around 4.5 nm, which is larger than the Fermi wavelength of around 2 nm. Hence, like free electrons in metals, the Ag NC electrons are thought to form a continuous energy band, leading to the formation of surface plasmons by photoexcitation. As for the fluorescence emission mechanism, the fact that the photoluminescence is excitation wavelength dependent suggests that the fluorescence originates from surface plasmons in Ag NCs of different sizes. By using Ag NC color converters and suitable blue light sources, white organic light-emitting devices can be fabricated based on the concept of light-mixing. For our blue light sources, we used polymer light-emitting electrochemical cells (PLECs), which, like organic light-emitting diodes, are area light sources. The PLECs were fabricated with a blue fluorescent π-conjugated polymer, poly[(9,9-dihexylfluoren-2,7-diyl)-co-(anthracen-9,10-diyl)] (PDHFA), and a polymeric solid electrolyte composed of poly(ethylene oxide) and KCF3SO3. In this device structure, the Ag NC color converter absorbs blue light from the PDHFA-based PLEC (PDHFA-PLEC) and then emits yellow light. When the PDHFA-PLEC is turned on by applying an external voltage, pure white light emission can be produced with Commission Internationale de l'Eclairage coordinates of (x = 0.32, y = 0.33) and a color rendering index of 93.6. This study shows that utilization of Ag NC color converters and blue PLECs is a very promising and highly effective method for realizing white organic light-emitting devices.

Original languageEnglish
Article number184302
JournalJournal of Applied Physics
Volume122
Issue number18
DOIs
Publication statusPublished - 2017 Nov 14

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nanoclusters
converters
color
electrochemical cells
light sources
polymers
plasmons
fluorescence
solid electrolytes
ethylene oxide
photoexcitation
wavelengths
illuminating
free electrons
energy bands
light emission
light emitting diodes
templates
photoluminescence
acids

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Ag nanocluster-based color converters for white organic light-emitting devices. / Nishikitani, Yoshinori; Takizawa, Daisuke; Uchida, Soichi; Lu, Yue; Nishimura, Suzushi; Oyaizu, Kenichi; Nishide, Hiroyuki.

In: Journal of Applied Physics, Vol. 122, No. 18, 184302, 14.11.2017.

Research output: Contribution to journalArticle

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