| 초록 |
We present multi-functional dendrimer ligands that act as the charge injection controlling layers as well as the adhesive layers at the interfaces between quantum dots (QDs) and the electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs). Specifically, we use amine-functionalized ligands (poly(amidoamine) dendrimers (PADs)) that bind to the surface of QDs by replacing the oleic acid ligands (OA) and also to the surface of ZnO ETL. PAD ligands adjust the electron injection rate from ZnO into QDs by altering the electronic energy levels of the ZnO surface and thereby improve the charge balance within QDs, leading to the enhancement of the device efficiency. As an ultimate achievement, the device efficiency improves by a factor of 3 by replacing the OA ligands (3.8%) with PAD ligands (11.4%). In addition, dendrimer ligands keep the QD emissive layer intact during subsequent solution processing, enabling us to accomplish solution-processed QLEDs. The results emphasize the importance of controlling the ligands of QDs to enhance QLED performance and offer effective chemical mean toward all-solution-processed QLEDs. |
