Capping Ligand Engineering of Cadmium-Free AIZS Quantum Dots Toward Bright Electroluminescent Light-Emitting Diodes by All-Solution Process

Abstract

Cadmium-free AgInZnS (AIZS) quantum dots (QDs) have garnered significant research interest for applications in light-emitting diodes (LEDs); however, their performance remains limited by insulating long-chain ligands. In this study, highly fluorescent orange-emitting AIZS QDs are synthesized by replacing long-chain 1-dodecanethiol (DDT) with short-chain 1-octanethiol (OTT), achieving photoluminescence quantum yields of up to 80% in solution and 60% in film. The incorporation of OTT in combination with oleic acid and oleylamine as co-capping ligands enabled excellent dispersion of the QDs in non-polar solvents. The resulting OTT-capped AIZS QDs exhibited improved film smoothness and reduced nonradiative recombination. Furthermore, all-solution-processed QD light-emitting diodes (QLEDs) are fabricated comprising indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate/hole transporting layer/AIZS QDs/ZnO electron transporting layer/Al. The effects of OTT capping and the thickness of the AIZS emitting layer on device performance are systematically evaluated. As a result, the QLEDs demonstrated enhanced luminance and current efficiency, reaching 515 cd m⁻² and 0.4 cd A⁻¹ respectively, representing improvements of over 50% and 33% compared to devices utilizing DDT-capped AIZS QDs. This study presents a facile and effective approach for developing high-brightness AIZS QLEDs.