INVESTIGATION ON SUB-BAND GAP OPERATION MECHANISM OF INP QUANTUM DOT-BASED LIGHT-EMITTING DIODES

Abstract

Colloidal quantum dot-based light-emitting diodes (QLEDs) are being to the fore as next-generation technique for future information displays. Though the research for QLEDs have made much progress from perspective of efficiency and stability, the origin of sub-band gap (sub-Eg) turn-on voltage is still controversal. In this study, we investigate the modification of sub-Eg turn-on phenomena of QLEDs. The turn-on voltage of QLEDs are increased as decreaing the hole injection barrier. The turn-on voltage of diode current and consequent light generation demonstrate a clear dependence on the energy difference between conduction band minimum of ZnO and HOMO of HTMs. Emergence of weak emission tail near 1Se-1Shh at sub-Eg implies an involvement of surface states of QDs in the charge injection event. We investigate decay dynamics of QDs, ultraviolet photoelectron spectroscopy, and electrical impedenace spectroscopy to clarify the role of surface states on the sub-Eg operation of QLEDs.