Charge Modulation Layer and Wide‐Color Tunability in a QD‐LED with Multiemission Layers

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 17; pp. e2007397 - n/a
• Main Authors: Park, Sung‐Jae, Song, Suk‐Ho, Kim, Sang Soo, Song, Jang‐Kun
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.04.2021
• Subjects: Charge distribution; charge modulation layers; color modulations; Emission analysis; Excitons; Light emitting diodes; Modulation; multiple emission layer structures; Nanotechnology; Pixels; quantum dot light‐emitting diodes; Quantum efficiency; Solvent effect; quantum dot light-emitting diodes; color modulations; multiple emission layer structures; charge modulation layers
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202007397

Widely tunable color emission from a single pixel is a promising but challenging technology for quantum‐dot light‐emitting diodes (QD‐LEDs). Even a QD‐LED pixel with stacked multi‐QD layers having different colors is likely to emit a monotonic color because the exciton recombination mostly occurs in 1 or 1.5 QD layers with better charge balance. In this study, an all‐solution‐processed QD‐LED with electrically tunable color emission over a wide color range by introducing a charge modulation layer (CML) is developed. Specifically, the CML acted as a high and narrow energy barrier for electrons between two QD layers, and the electron drift is sensitively controlled via the field‐dependent tunneling effect. Therefore, the charge distribution and balance in the two QD layers re‐electrically tunable, which enhanced the color tunability. The color tuning range and quantum efficiency are effectively controlled depending on the CML material and thickness. In addition, the color change caused by the solvent effect in a QD‐LED with dual QD layers is thoroughly investigated. The proposed method may advance the understanding of QD emission behavior with the use of CML and provide a practical approach for the actual application of color‐tunable pixel technology. A quantum‐dot light‐emitting diode with electrically tunable color emission over a wide range is achieved by introducing a charge modulation layer (CML). CML controls the electron density in two emission layers via the tunneling effect, and the emission color is controlled by the applied voltage. In addition, the external quantum efficiency can be also improved by the insertion of CML.