Inkjet printing of mixed layers comprising multinary semiconductor quantum dots and charge transport materials for light-emitting diode displays

Abstract

Quantum dots (QDs) are important luminescent structures with applications in wide-color-gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs are expected to serve as eco-friendly materials to replace conventional QDs owing to the narrow spectral widths and tunable bandgaps of these QDs. However, the application of multinary QDs, which tend to exhibit defect-related emissions, to QD light-emitting diode (QLED) displays will require electroluminescence to be obtained from QLEDs incorporating inkjet-printed emitting layers. The present work examines QLEDs exhibiting vibrant color emissions based on blue-emitting Zn–Se–Te QDs, green-emitting Ag–In–Ga–S QDs, and red-emitting Ag–Cu–In–Ga–S QDs. Each such QLED contains QD emitting layers comprising a mixture of charge transport materials. The spectra obtained from these RGB QLEDs fabricated by spin-coating show very high color purity. Passive matrix QLED displays incorporating these QDs are also fabricated by inkjet printing to demonstrate the high color purity that can be obtained from multinary QDs in displays. In conjunction with passive matrix driving, these displays produce clear moving images with vibrant electroluminescence originating from the multinary QDs. The present results indicate that these QDs have significant potential for utilization in wide-color-gamut displays.