Berlin 2005 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 36: Single molecules II
CPP 36.4: Vortrag
Mittwoch, 9. März 2005, 12:00–12:15, TU C243
Quantification of photo-induced and spontaneous quantum-dot photoluminescence blinking — •Fernando D. Stefani, Xinhua Zhong, Wolfgang Knoll, and Maximilian Kreiter — Max-Planck-Institut für Polymerforschung
Ackermannweg 10 D55128, Mainz
Photoluminescence blinking of Zn0.42Cd0.58Se QDs on glass and conducting substrates was investigated experimentally as a function of the excitation intensity and modeled via a Monte-Carlo method. One (spontaneous) process is active for switching on and off, and has a power-law probability distribution for the length of both bright and dark periods. In addition, a single rate (photoinduced) process is evoked for the on→off transition. From the modeling of the data it is possible to extract independent information about both processes. The spontaneous blinking is completely independent of excitation intensity and the electronic properties of the environment. Spontaneous on- and off-switching processes show identical statistics which indicate a symmetry of the underlying physical mechanism, and a weak but noticeable memory effect. The photoinduced on→off transition is defined by its characteristic time τPI and can account for all the experimentally observed photoinduced effects. On glass, τPI is found to be inversely proportional to the excitation power. This indicates the presence of a 1-photon process in agreement with earlier studies on isolating matrices. On ITO, τPI shows an unprecedented exponential dependence on excitation intensity.