Challenge to the Charging Model of Semiconductor-Nanocrystal Fluorescence Intermittency from Off-State Quantum Yields and Multiexciton Blinking

• DOI: 10.1103/physrevlett.104.157403
• Publication Date: 2010-04-19T14:06:53Z
• Authors: Jing Zhao; Gautham Nair; Brent R. Fisher; Moungi G. Bawendi
• Keywords: Intermittency

Semiconductor nanocrystals emit light intermittently; i.e., they ``blink,'' under steady illumination. The dark periods have been widely assumed to be due photoluminescence (PL) quenching by an Auger-like process involving a single additional charge present in the nanocrystal. Our results challenge this long-standing assumption. Close examination of exciton PL intensity time traces CdSe(CdZnS) core(shell) reveals that state quantum yield can 10 times less than biexciton yield. In addition, we observe spectrally resolved multiexciton emission and find it also blinks with on/off ratio greater $10\ensuremath{\mathbin:}1$. These directly contradict predictions charging model.