Efficient green InP quantum dot light-emitting diodes using suitable organic electron-transporting materials

摘要

Quantum dot light-emitting diodes (QD-LEDs) are expected to be used in wide-color-gamut displays because the emission colors from QDs are highly saturated. InP-based QDs are one of the most promising candidates for low-toxicity QDs. Here, we report an efficient green QD-LED whose emitting layer was composed of InP-based QDs and an organic electron-transporting material (ETM). To investigate ETMs suitable for combining with the QDs, the device characteristics of QD-LEDs with various ETMs were compared. The external quantum efficiency (EQE) and the driving voltage were found to be markedly improved by the incorporation of suitable ETMs. We demonstrated green QD-LEDs with a high maximum EQE of 10.0% and a low turn-on voltage of 2.4 V by using 2,4,6-tris(3'-(pyridin-3-yl)biphenyl-3-yl)-l,3,5-triazine (TmPPPyTz) as an ETM. Furthermore, to clarify the origin of the difference in device characteristics, we investigated their hole- and electron-transporting properties. The results suggested that the hole-current leakage from the QD layer was substantially suppressed in the QD-LEDs with TmPPPyTz. Using an ETM with such hole-suppressing ability is demonstrated to be an effective approach to improving the EQEs of QD-LEDs.