Intermittently fluorescing single molecule systems are found in many materials, including semiconductor quantum dots (QD), dyes on crystalline or nanoparticle film surfaces, and biological systems. The QD’s show a ~ -3/2 power law for the distribution of “on” and “off” times. For the “on” states there is also an exponential tail whose importance increases with increasing light intensity. We interpret these and additional QD results in terms of a diffusion/electron transfer (ET) theory (“spectral” diffusion”). Less studied than QD’s is the single molecule dye-photoinjection of electrons or holes into semiconductors or into their films of nanoparticles, of solar cell interest. Here, an injection can be either into a conduction band (valence band in the case of hole injection) or into the band gap, followed by diffusion of the carrier. We describe a diffusion/ET theory, leading to different kinetics for band and band gap injection and recombination and to the observed ~ -1 power law.
Extension of the Diffusion Controlled Electron Transfer Theory for Intermittent Fluorescence of Quantum Dots: Inclusion of Biexcitons and the Difference of “On” and “Off” Time Distributions,” Z. Zhu and R. A. Marcus, Phys. Chem. Chem. Phys., 16, 25691-25700 (2014)
Wei-Chen Chen and R. A. Marcus “Theory of a single dye molecule blinking with a diffusion-based power law distribution” J. Phys. Chem. C, 116, 15782-15789 (2012)