Synchronous Outcoupling of Tri‐Colored Light for Ultra‐Bright White Quantum Dot Light‐Emitting Diodes by Using External Wrinkle Pattern

Abstract

AbstractThe brightness of white quantum dot light‐emitting diodes (W‐QLEDs) is one of the most important indicators for their commercialization. However, the brightness of W‐QLEDs is severely limited by the light trapped in the substrate mode. In this work, a prototype W‐QLED with the original brightness of 88 181 cd m−2 is fabricated by using a mixture of red‐, green‐, and blue‐emitting quantum dots as a light emitting layer. Then, a tailored wrinkle pattern is attached on the bottom of the glass substrate of W‐QLEDs for the further light extraction. Different from the widely used external periodic patterns, the wrinkle patterns with richer Fourier spectra can outcouple the tricolor light trapped in the substrate mode simultaneously. In this case, the brightness of W‐QLEDs has a 54.4% enhancement to an ultra‐high value 136 207 cd m−2, and realizes the quasi‐Lambertian emission. The external quantum efficiency is improved from 9.68% to 13.41%. Meanwhile, correlated color‐temperature can cover a wider span transforming from pure white light (5115 K) to cold white light (6912 K). This work proposes a unique and efficient approach for the light extraction and color control of W‐QLEDs for their real application.