Atomistic Insight Into the Role of Alkali Metals in Modulating Optical Properties of CdS Quantum Dot Embedded Glass

Quantum‐dot (QD)‐embedded glasses are pivotal for advanced photonic applications, yet achieving high photoluminescence performance remains a challenge due to complex interfacial defect states. While recent advances have identified the QD/glass interface as a critical determinant of luminescence, the specific mechanistic role of different alkali metal modifiers in shaping this interface—and consequently the optical properties—remains a significant knowledge gap. Here, we employ atomistic simulations to systematically investigate CdS QDs embedded in 55SiO 2 ‒25R 2 O‒5BaO‒5BaF 2 ‒5B 2 O 3 ‒5ZnO (R = Li, Na, K, or their binary mixtures) glasses. We reveal that the choice of alkali metal directly dictates the interfacial reconstruction: Li cations exhibit a strong preference for bonding with F ions rather than S atoms, whereas Na and K ions display the opposite tendency, driving a higher proportion of S‒alkali interfacial bonds. Furthermore, larger alkali cations induce greater glass network depolymerization, and mixed‐alkali systems manifest pronounced non‐linear deviations in electronic properties. Ultimately, our findings establish a direct composition‒structure‒property relationship, providing experimentalists with a theoretical blueprint to rationally select and mix alkali modifiers to engineer the QD/glass interface and optimize the fluorescence performance of QD‐embedded glasses.