Compositional engineering of multinary Cu–In–Zn-based semiconductor nanocrystals for efficient and solution-processed red-emitting quantum-dot light-emitting diodes

For quantum-dot light-emitting diodes (QD-LED), replacing Cd-based II-VI nanocrystals (NCs) with the Cu-In-Zn-VI counterparts combines the consideration of environmental benignity and device performance. To prove this concept, the chemical composition and nanostructures of Cu-In-Zn-VI nanocrystals need to be thoroughly explored aiming to competitive optoelectronic properties. Herein, we reported a detailed study of Cu–In–Zn–Se–S synthesis and demonstrated how the optical bandgap, emission full width at half-maximum (FWHM) and the performance of QD-LED were tuned by simply changing the dose of precursors in a non-injection synthesis. Evident by optical absorption, the optimization of Se and Cu doses enabled good dispersity and desired emission wavelength. Further analysis of photo-electron spectroscopy revealed the chemical composition from core to surface favored soft confinement of exciton by gradually increasing the loading of Zn element. Finally, we successfully demonstrated solution-processed QD-LEDs with the best external quantum efficiencies as high as 4.2% and emission wavelength centering at 663 nm. To our best knowledge, this is the most efficient solution-processed red QD-LED based on Cu-In-Zn-VI nanocrystals.