ARTICLE
Highly Efficient, Color-Reproducible Full-Color Electroluminescent Devices Based on Red/Green/Blue Quantum Dot-Mixed Multilayer Ki-Heon Lee,† Chang-Yeol Han,† Hee-Don Kang,† Heejoo Ko,‡ Changho Lee,‡ Jonghyuk Lee,‡ NoSoung Myoung,§ Sang-Youp Yim,§ and Heesun Yang*,† †
Department of Materials Science and Engineering, Hongik University, Seoul 121-791, Korea, ‡Display Research Center, Samsung Display Company, Ltd., Yongin, Kyunggi-do 446-811, Korea, and §Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea
ABSTRACT Over the past few years the performance of colloidal quantum dot-light-emitting diode
(QLED) has been progressively improved. However, most of QLED work has been fulfilled in the form of monochromatic device, while full-color-enabling white QLED still remains nearly unexplored. Using red, green, and blue quantum dots (QDs), herein, we fabricate bichromatic and trichromatic QLEDs through sequential solution-processed deposition of poly(9-vinlycarbazole) (PVK) hole transport layer, two or three types of QDs-mixed multilayer, and ZnO nanoparticle electron transport layer. The relative electroluminescent (EL) spectral ratios of constituent QDs in the above multicolored devices are found to inevitably vary with applied bias, leading to the common observation of an increasing contribution of a higher-band gap QD EL over low-band gap one at a higher voltage. The white EL from a trichromatic device is resolved into its primary colors through combining with color filters, producing an exceptional color gamut of 126% relative to National Television Systems Committee (NTSC) color space that a state-of-the-art full-color organic LED counterpart cannot attain. Our trichromatic white QLED also displays the recordhigh EL performance such as the peak values of 23 352 cd/m2 in luminance, 21.8 cd/A in current efficiency, and 10.9% in external quantum efficiency. KEYWORDS: quantum dot-light-emitting diode . full-color electroluminescence . efficiency . color gamut
F
ascinating fluorescent properties of colloidal semiconductor quantum dots (QDs), including outstanding photoluminescent (PL) quantum yield (QY), facile emission tunability, and narrow emission bandwidth, render them suitable as visible emitters for the application to display and lighting devices. In particular, a high degree of color saturation (purity) enabled by QD emission bandwidths as sharp as
