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J Nanopart Res (2013) 15:1462 DOI 10.1007/s11051-013-1462-3
RESEARCH PAPER
Unique oxide overcoating of CuInS2/ZnS core/shell quantum dots with ZnGa2O4 for fabrication of white light-emitting diode with improved operational stability
Woo-Seuk Song Eun-Pyo Jang
Jong-Hoon Kim Ho Seong Jang Heesun Yang
Received: 20 November 2012 / Accepted: 22 January 2013 / Published online: 2 February 2013 Springer Science+Business Media Dordrecht 2013
Abstract CuInS2 quantum dots (QDs) have been recently highlighted as blue-to-yellow color converters for the demonstration of QD-based white light-emitting diodes (LEDs) owing to their advantageous uorescent attributes including a broadband yellow emission and exceptional quantum yield. Similar to other types of elaborate core/shell structured QDs, however, core/shell QDs of CuInS2/ZnS are also susceptible to the photo-induced degradation, rendering them inappropriate for the practical application to high operational stability white LED. In this study, CuInS2/ZnS QDs are overcoated with the unprecedented oxide phase of ZnGa2O4 to enhance their photostability, and the resulting CuInS2/ZnS/ZnGa2O4
QDs are characterized with X-ray diffraction and transmission electron microscope. The operational stability test of CuInS2/ZnS/ZnGa2O4 QD-based white
LED is performed and compared with that of uncoated CuInS2/ZnS QD-based one, and the efcacy of
ZnGa2O4 overlayer is proved in mitigating the photodegradation of QDs and thus improving the device stability.
Keywords CuInS2/ZnS quantum dots
Blue-to-yellow color converters White light-emitting
diodes ZnGa2O4 shell Operational stability
Introduction
IIIIVI group-based semiconductor nanocrystals quantum dots (QDs) comprising ternary compositions such as CuInS (Li et al. 2009, 2011; Xie et al. 2009; Kim et al. 2012c; Park and Kim 2011; Nam et al. 2011; Song and Yang 2012; Hsu et al. 2011; Tan et al. 2011; Chen et al. 2012; Uehara et al. 2008), AgInS (Xie et al. 2009; Hamanaka et al. 2011; Hong et al. 2012), and CuGaS (Song et al. 2012), and quaternary ones including AgInGaS (Uematsu et al. 2010), ZnCuInS (De Trizio et al. 2012; Zhang et al. 2011; Tang et al. 2011; Zhang and Zhong 2011), ZnAgInS (Torimoto et al. 2001), and MnCuIn S (Liu et al. 2012) have been emerging as highly efcient luminophores. Thanks to the defective crystalline nature of IIIIVI QDs listed above, the radiative recombination of photo-excited carriers is governed by the intragap levels that develop inside a host QD as acceptor and/or donor states, typically characteristic of Stokes...