Song Yang, Liu Ruixiang, Wang Zhibo, Xu Huaiyu, Ma Yong, Fan Fengjia, Voznyy Oleksandr, Du Jiangfeng
Hefei National Laboratory for Physical Sciences at the Microscale and School of Physical Sciences, University of Science and Technology of China, Hefei 230026, China.
CAS Key Laboratory of Microscale Magnetic Resonance, University of Science and Technology of China, Hefei 230026, China.
Sci Adv. 2022 Feb 25;8(8):eabl8219. doi: 10.1126/sciadv.abl8219. Epub 2022 Feb 23.
Current state-of-the-art quantum dot light-emitting diodes have reached close to unity internal quantum efficiency. Further improvement in external quantum efficiency requires more efficient photon out-coupling. Improving the directivity of the photon emission is considered to be the most feasible approach. Here, we report improved emission directivity from colloidal quantum dot films. By growing an asymmetric compressive shell, we are able to lift their band-edge state degeneracy, which leads to an overwhelming population of exciton with in-plane dipole moment, as desired for high-efficiency photon out-coupling. The in-plane dipole proportion determined by back-focal plane imaging method is 88%, remarkably higher than 70% obtained from conventional hydrostatically strained colloidal quantum dots. Enhanced emission directivity obtained here opens a path to increasing the external quantum efficiencies notably.
当前最先进的量子点发光二极管已接近单位内量子效率。外部量子效率的进一步提高需要更高效的光子出耦合。提高光子发射的方向性被认为是最可行的方法。在此，我们报告了胶体量子点薄膜发射方向性的改善。通过生长不对称压缩壳层，我们能够消除其带边态简并，这导致具有面内偶极矩的激子占主导地位，这是高效光子出耦合所需要的。通过后焦平面成像方法确定的面内偶极比例为88%，显著高于传统静水应变胶体量子点获得的70%。此处获得的增强发射方向性为显著提高外部量子效率开辟了一条途径。
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