Enhanced Electroluminescence of CdSe/ZnS Quantum Dot Light–emitting Diodes with Phosphorescent Donors

Abstract

ABSTRACTWe demonstrated the enhancement of electroluminescence (EL) from green CdSe/ZnS QDs in hybrid QD/organic light-emitting diodes (QD-LEDs) by employing blue phosphorescent dyes Bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium (FIrpic) as efficient exciton harvesters and energy transfer donors. Precise control of the concentration of the FIrpic donors doped in a 4,4’-N, N’-dicarbazole-biphenyl (CBP) host and their distance from the QD layer led to complete triplet exciton energy transfer and EL enhancement by a factor of 2.5. The Förster distance between FIrpic molecules and green CdSe/ZnS QDs was determined to be ∼ 8 nm, which is in a good agreement with the value calculated using the Förster model. Our study shows that integrating colloidal QDs with phosphorescent organic dyes provides an effective means for improving the quantum efficiency of QD-based hybrid LEDs.