title: Highly bright yellow-green-emitting CuInS₂ colloidal quantum dots with core/shell/shell architecture for white light-emitting diodes.
abstract: In this study, we report bright yellow-green-emitting CuInS2 (CIS)-based quantum dots (QDs) and two-band white light-emitting diodes (LEDs) using them. To achieve high quantum efficiency (QE) of yellow-green-emitting CIS QDs, core/shell/shell strategy was introduced to high quality CIS cores (QE = 31.7%) synthesized by using metal-oleate precursors and 1-dodecanethiol. The CIS/ZnS/ZnS QDs showed a high QE of 80.0% and a peak wavelength of 559 nm under the excitation of 450 nm, which is well matched with dominant wavelength of blue LEDs. The formation of core/shell/shell structure was confirmed by X-ray diffraction, transmission electron microscopy, and inductively coupled plasma-optical emission spectroscopy analyses. Intense and broad yellow-green emission band of the CIS/ZnS/ZnS is beneficial for bright two-band white light. When the CIS/ZnS/ZnS was coated on the blue LEDs, the fabricated white LED showed bright natural white light (luminous efficacy (η(L)) = 80.3 lm·W(-1), color rendering index (R(a)) = 73, correlated color temperature (T(c)) = 6140 K). The QD-white LED package showed a high light conversion efficiency of 72.6%. In addition, the CIS/ZnS/ZnS-converted white LED showed relatively stable white light against the variation of forward bias currents of 20-150 mA [color coordinates (x, y) = (0.3320-0.3207, 0.2997-0.2867), R(a) = 70-72, T(c) = 5497-6375 K].
authors.affiliation: †Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Park
authors.affiliation: †Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.|‡Department of Chemistry, Korea University, Seoul 136-701, Republic of Korea.
authors.forename: Ara
authors.initials: A
authors.lastname: Hong
authors.affiliation: §Department of Materials Science and Engineering, Hongik University, Seoul 121-791, Republic of Korea.
authors.forename: Jong-Hoon
authors.initials: JH
authors.lastname: Kim
authors.affiliation: §Department of Materials Science and Engineering, Hongik University, Seoul 121-791, Republic of Korea.
authors.forename: Heesun
authors.initials: H
authors.lastname: Yang
authors.affiliation: ‡Department of Chemistry, Korea University, Seoul 136-701, Republic of Korea.
authors.forename: Kwangyeol
authors.initials: K
authors.lastname: Lee
authors.affiliation: †Materials Architecturing Research Center, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.|⊥Korea University of Science and Technology, Daejeon 305-350, Republic of Korea.
authors.forename: Ho Seong
authors.initials: HS
authors.lastname: Jang
keywords: core/shell/shell; luminescence; quantum dots; white LEDs