Enhancing extraction efficiency of quantum dot light-emitting diodes introducing a highly wrinkled ZnO electron transport layer

Light extraction efficiency is crucial for achieving highly efficient and bright quantum dot light-emitting diodes (QLEDs), and current efforts toward introducing light outcoupling nanostructures always require complicated procedures. An extremely simple and efficient method to introduce light outcoupling nanostructures in the ZnO electron transport layer (ETL) is demonstrated by adopting a certain heating rate during the annealing process. The ultimate device exhibits a current efficiency of 9.1 cd/A, giving a 50% efficiency improvement compared to the control device with a flat ZnO ETL. This arises from the increased light extraction efficiency induced by random nanostructures formed on a wrinkled ZnO ETL, which could also be modulated by adjusting the heating rate during the annealing process. This study not only provides a simple and efficient method to introduce light outcoupling nanostructures, but also shows ample room for further performance enhancement of QLEDs with the guideline of light extraction.