Achieving high efficiency by improving hole injection into quantum dots in colloidal quantum dot light-emitting devices with organic electron transport layer

We developed highly efficient quantum dot light-emitting devices (QD-LEDs) by improving the charge balance with triple hole injection and transport layers consisted of MoO3/poly[N,N '-bis(4-butylphenyl)-N,N '-bis(phenyl)benzidine] (poly-TPD)/poly(9-vinylcarbazole) (PVK). The hole injection layer was prepared by evaporating MoO3. Poly-TPD and PVK were spin-coated as hole transport layers. The stepwise energy level of MoO3/poly-TPD/PVK enhanced the hole injection from anode to QD emitters. Tris[2,4,6-trimethyl-3-(pyridine-3-yl)phenyl]borane (3TPYMB) was used as an electron transport layer (ETL) because of its relatively high electron mobility and deep lowest unoccupied molecular orbital (LUMO) level. We achieved high external quantum efficiency of 8.2% by enhancing hole injection into the QD layer in the organic ETL-based green QD-LEDs.