Water Molecules Tuning Photoluminescence Of Surface Functionalized Silicon Quantum Dots

One of the difficulties in using silicon quantum dots(Si QDs)as quantum dotbased light-emitting diodes is the irreversible degradation brought on by humid circumstances,which reveals their excited state electrical characteristics substantially impacted by the surface water.However,the mechanism of photoluminescence(PL)linked to the modification of excited state electrical characteristics is still unknown.In order to comprehend how surface functional silicon devices behave in conditions of water environment.Here,we investigate the effects of dipole–dipole interactions between water molecules and various surface functional groups on the PL of Si QDs(Si29H36)related to the electrical performance of Si QDs using time-dependent density functional theory(TDDFT).The substituent effect with a hydrogen atom replaced by a fluorine atom almost has no impact on the PL of Si QDs with the adsorption of water clusters in comparison to the hydrophobic group of pure hydrogen passivation.It’s interesting to note that although a hydrophilic hydroxyl group substitution shows only slightly blueshift the PL spectrum,the intense dipole-dipole interaction between a hydroxyl group and water molecules can significantly cause the delocalized electrons to become localized,resulting in a dual-band peak observed in the PL spectra of Si29H35 OH surrounded by four or five water molecules.The adsorption of water molecules leads to surface trap states due to dipole-dipole interactions,which is the source of this particular PL mechanism.The electron distribution centered on the silicon-oxygen double bond will be triggered by the presence of highly polarizable double-bonded oxygen,thus keeping the PL spectrum of Si29H35 O unaltered by the water molecules.This study establishes a theoretical basis for the practical use of Si QDs as optoelectronic devices by demonstrating that the PL of Si QDs with the substituent hydroxyl group is particularly sensitive to humidity.