Charging and Discharging Channels in Photoluminescence Intermittency of Single Colloidal CdSe/CdS Core/Shell Quantum Dot.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS(2016)
Abstract
Understanding photoluminescence (PL) intermittency of single quantum dots (QDs) (intensity blinking by randomly switching between distinguishable brightness states under continuous excitation) has been a longstanding fundamental challenge and potential roadblock for their applications. Here we introduce a new analysis method for single-molecule spectroscopy that treats the blinking as photochemical/chemical processes (switching between neutral/ bright and charged/dim states). It uncovers the channels for charging (bright to dim) and discharging (dim to bright) involved in PL blinking of single CdSe/CdS core/shell QDs. Both charging and discharging of the single CdSe/CdS core/shell QD possess a photochemical channel (-1075 to 10(-6) events/photon) that linearly depends on excitation in both single- and multi-exciton regime. These two linear channels coupled to a spontaneous discharging channel (similar to 2 events/s) to dictate the QDs from nonblinking to gradually blinking under increasing excitation. For high-quality CdSe/CdS core/shell QDs, Auger ionization of multiexciton for both charging and discharging is negligible.
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Key words
single colloidal cdse/cds,photoluminescence intermittency,cdse/cds core/shell,quantum dot
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