Tunable and Orange to Near-Infrared Doped Photoluminescence of Ag-Doped II-VI QDs

The electronic doping of colloidal semiconductor nanocrystals presents significant potential for future device concepts in optoelectronic and spin-based technologies. Ag⁺ is gaining recognition as a novel electronic dopant in II-VI nanocrystals as it creates intragap electronic states that participate in the recombination process of photogenerated carriers within the host materials. Herein, we report the synthesis of a series of Ag-doped II-VI quantum dots (QDs) of varying sizes via a low-temperature cation exchange strategy. A surprisingly tunable dopant emission covering the orange to near-infrared window (606-725 nm for CdS/Ag and 745-877 nm for CdSe/Ag) is achieved through the manipulation of particle sizes in the host QDs, which is derived from the quantum confinement effect. The as-prepared Ag⁺-doped II-VI QDs exhibit effective size-dependent tunable emission with a quantum yield (QY) up to 40.7% and strongly suppressed reabsorption due to the large Stoke shift up to 0.86 eV, demonstrating their potential use as candidates for various optoelectronic devices. Furthermore, using CdSe/Ag as a case to study, both experimental results and density functional theory (DFT) calculations indicate that the successful Ag⁺ doping in the matrix not only results in the formation of additional extra luminescence centers but also causes a reduction in the bandgap.