Highly Stable and Scalable Blue QD‐LED via an Evaporated TiO<sub>2</sub> Thin Film as an Electron Transport Layer
Sang Yun Bang, Xiang‐Bing Fan, Sung‐Min Jung, Jiajie Yang, Dong‐Wook Shin, Yo‐Han Suh, Tae Hoon Lee, Sanghyo Lee, Hyung Woo Choi, Luigi G. Occhipinti, Soo Deok Han, Jong Min Kim
Abstract
Abstract Quantum dot‐based light‐emitting diodes (QD‐LEDs) have excellent optical properties; however, their limitations of stability, reproducibility, and scalability due to the solution process are the major drawback. Herein, blue QD‐LEDs fabricated with the conventional vacuum process using an e‐beam‐evaporated TiO 2 thin film as an electron transport layer (ETL) are demonstrated. CdZnS/ZnS‐based blue LEDs with a TiO 2 thin film are fabricated under ambient conditions. They exhibit maximum external quantum efficiencies of 3.53% and a peak luminance of 2847 cd m −2 . These values are retained, which minimizes performance degradation under high potential bias. In addition, the optimized evaporated TiO 2 thin film has a negligible red shift (0.5 nm) of the peak wavelength between the photoluminescence spectrum and electroluminescence spectrum with stable full‐width at half‐maximum changing by less than 2 nm at high voltage. Finally, a blue QD‐LED is fabricated on a scalable emission area of 2 × 2 in. with a patterned cathode accompanied by an evaporated TiO 2 thin film, which allows to perform conventional photolithography. A highly stable and reproducible vaporized inorganic thin film as the ETL supports the multilayer architecture to minimize the process damage.