Incessant Photoluminescence from Semiconductor Nanocrystals: Challenges and Prospects

Semiconductor nanocrystals, also called quantum dots, with uninterrupted and bright photoluminescence are expected to bring groundbreaking advancements to luminescent displays, solar cells and biological imaging. Although highly-luminescent quantum dots based on cadmium and lead chalcogenides have been developed, stochastic fluctuation of photoluminescence intensity, also called blinking, continues to be a major challenge in the applications of these tiny crystals to single molecule imaging and single photon devices. Blinking photoluminescence has been extensively investigated since its first observation in 1996.1 In a highly-excited quantum dot, blinking originates from photo-charging, ultrafast non-radiative Auger recombination, and delayed charge neutralization.2,3 So far, blinking suppression is accomplished by defect passivation,4 electron transfer,5,6 and shell preparation.7 Among these methods, electron transfer is attractive for post-synthesis, real-time blinking suppression. Investigations of electron transfer from molecular donors to quantum dots and from quantum dots to molecular and nanoparticle acceptors reveal uncorrelated thermodynamic and kinetic properties associated with blinking.8 By referring to hot charge carriers, the rate of non-radiative Auger recombination, and free energy change of electron transfer, this presentation highlights single-molecule detection and real-time suppression of photoluminescence blinking in CdSe-based quantum dots.   

 

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