Transparent InP Quantum Dot Light-Emitting Diodes with ZrO2 Electron Transport Layer and Indium Zinc Oxide Top Electrode

• Published in: Advanced functional materials 2016-05, Vol.26 (20), p.3454-3461
• Main Authors: Kim, Hee Yeon, Park, Yu Jin, Kim, Jiwan, Han, Chul Jong, Lee, Jeongno, Kim, Yohan, Greco, Tonino, Ippen, Christian, Wedel, Armin, Ju, Byeong-Kwon, Oh, Min Suk
• Format: Article
• Language: English
• Subjects: InP; light emitting diode; quantum dot; transparent; ZrO2
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201505549

Because of outstanding optical properties and non‐vacuum solution processability of colloidal quantum dot (QD) semiconductors, many researchers have developed various light emitting diodes (LEDs) using QD materials. Until now, the Cd‐based QD‐LEDs have shown excellent properties, but the eco‐friendly QD semiconductors have attracted many attentions due to the environmental regulation. And, since there are many issues about the reliability of conventional QD‐LEDs with organic charge transport layers, a stable charge transport layer in various conditions must be developed for this reason. This study proposes the organic/inorganic hybrid QD‐LEDs with Cd‐free InP QDs as light emitting layer and inorganic ZrO2 nanoparticles as electron transport layer. The QD‐LED with bottom emission structure shows the luminescence of 530 cd m−2 and the current efficiency of 1 cd/A. To realize the transparent QD‐LED display, the two‐step sputtering process of indium zinc oxide (IZO) top electrode is applied to the devices and this study could fabricate the transparent QD‐LED device with the transmittance of more than 74% for whole device array. And when the IZO top electrode with high work‐function is applied to top transparent anode, the device could maintain the current efficiency within the driving voltage range without well‐known roll‐off phenomenon in QD‐LED devices. Transparent eco‐friendly quantum dot Quantum Dot OLEDs light emitting diodes (QD‐LEDs) are realized by using InP QDs, inorganic ZrO2 electron transport layer (ETL), and indium zinc oxide (IZO) top electrode, showing 530 cd m−2 and 1 cd A−1. When the two‐step sputtering process for the IZO top electrode is used, a fully transparent QD‐LED (Tpanel > 74% @ 550 nm) with 200 cd m−2 and 0.47 cd A−1 can be fabricated.