Pure Green Ag–In–Ga–S/Ga–S Quantum Dot Light-Emitting Diodes with Electron Transport Materials Exhibiting Enhanced Luminescence Properties

Abstract

Quantum dots (QDs) are essential luminescent materials with applications in wide-color-gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs composed of groups I, III and VI elements are expected to serve as eco-friendly materials to replace conventional QDs owing to the potential narrow spectral widths and tunable bandgaps of the former. Although optimized Ag–In–Ga–S/Ga–S core/shell QDs (AIGS QDs) have exhibited vibrant green emissions, electroluminescence from QD-based light-emitting diodes (QLEDs) incorporating these AIGS QDs is reduced as a consequence of the effects of defect sites. The present work therefore examines the incorporation of electron transport materials (ETMs) into AIGS QD emitting layers. A device incorporating emitting layers composed of AIGS QDs and 2,4,6-tris(3-(3-pyridyl)phenyl)-1,3,5-triazine (TmPPyTz), with the latter acting as a highly conductive ETM, exhibits a low driving voltage and high efficiency. Furthermore, the addition of two ETMs — TmPPyTz and tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane — is found to provide enhanced luminescence properties because these materials are deposited in the emitting layer in different forms and hence has varying effects in terms of improving conductivity and charge balance. The resulting QLEDs have a sharp spectral width of 30 nm, suggesting a level of color purity suitable for wide-color-gamut displays.