Browsing by Author "Yang, Xuyong"

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Electroluminescence Efficiency Enhancement in Quantum Dot Light-Emitting Diodes by Embedding a Silver Nanoisland Layer
(WILEY-V C H VERLAG GMBH, POSTFACH 101161, 69451 WEINHEIM, GERMANY, 2015) Yang, Xuyong; Hernandez-Martinez, Pedro Ludwig; Dang, Cuong; Mutlugun, Evren; Zhang, Kang; Demir, Hilmi Volkan; Sun, Xiao Wei; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
A colloidal quantum dot light-emitting diode (QLED) is reported with substantially enhanced electroluminescence by embedding a thin layer of Ag nanoislands into hole transport layer. The maximum external quantum efficiency (EQE) of 7.1% achieved in the present work is the highest efficiency value reported for green-emitting QLEDs with a similar structure, which corresponds to 46% enhancement compared with the reference device. The relevant mechanisms enabling the EQE enhancement are associated with the near-field enhancement via an effective coupling between excitons of the quantum dot emitters and localized surface plasmons around Ag nanoislands, which are found to lead to good agreement between the simulation results and the experimental data, providing us with a useful insight important for plasmonic QLEDs.
Highly flexible, electrically driven, top-emitting, quantum dot light-emitting stickers
(American Chemical Society, 2014) Yang, Xuyong; Mutlugun, Evren; Dang, Cuong; Dev, Kapil; Gao, Yuan; Tan, Swee Tiam; Sun, Xiao Wei; Demir, Hilmi Volkan; 0000-0003-3715-5594; AGÜ, Mühendislik Fakültesi, Elektrik - Elektronik Mühendisliği Bölümü; Mutlugun, Evren
Flexible information displays are key elements in future optoelectronic devices. Quantum dot light-emitting diodes (QLEDs) with advantages in color quality, stability, and cost-effectiveness are emerging as a candidate for single-material, full color light sources. Despite the recent advances in QLED technology, making high-performance flexible QLEDs still remains a big challenge due to limited choices of proper materials and device architectures as well as poor mechanical stability. Here, we show highly efficient, large-area QLED tapes emitting in red, green, and blue (RGB) colors with top-emitting design and polyimide tapes as flexible substrates. The brightness and quantum efficiency are 20 000 cd/m2 and 4.03%, respectively, the highest values reported for flexible QLEDs. Besides the excellent electroluminescence performance, these QLED films are highly flexible and mechanically robust to use as electrically driven light-emitting stickers by placing on or removing from any curved surface, facilitating versatile LED applications. Our QLED tapes present a step toward practical quantum dot based platforms for high-performance flexible displays and solid-state lighting.