Abstract
The effect of molecular reductants on the charge transfer-induced brightening of near-infrared photoluminescence (PL) from silicon (Si) quantum dots (QDs) was studied. Without a molecular reductant, a temporal decrease of the PL quantum yield (QY) during light irradiation in water was observed. The temporal photodarkening was reversed when a molecular reductant [sodium sulfites (Na2SO3)] was added in water. In Na2SO3-dissolved water, the PL QY increased gradually during light irradiation. The photobrightening behavior depended strongly on the amount of reductant molecules, excitation power, and the size of Si QDs. The observed phenomena suggest that an excess hole generated by trapping a photoexcited electron to a trap level is effectively removed by a reductant molecule. The observed charge transfer-induced photobrightening paves way to realize high efficiency and stable Si QDs-based phosphors usable in aqueous media.
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