Enhanced performances of quantum dot light-emitting diodes with doped emitting layers by manipulating the charge carrier balance

Abstract

High performance quantum dot light-emitting diodes (QD-LEDs) have been realized by doping quantum dots into a polymer matrix as an emitting layer (EML). Efficient energy transfer from the matrix to QDs occurs, resulting in high efficiency QD emission. The issue of hole injection from the hole transport layer to the QD layer, which occurs in normal QD-LEDs due to the ultra-low highest occupied molecular orbital (HOMO) level of QDs, can be neglected. By introducing an additional hole blocking layer with a suitable lowest unoccupied molecular orbital (LUMO) level and electron mobility between the doped QD EML and electron transporting layer (ETL), the emission from the ETL can be eliminated, and an external quantum efficiency (EQE) of 4.7% has been obtained.