Open AccessUltrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots
Author(s) -
Smith Charles T.,
Leontiadou Marina A.,
Page Robert,
O'Brien Paul,
Binks David J.
Publication year - 2015
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201500088
Subject(s) - ultrafast laser spectroscopy , exciton , trapping , quantum dot , absorption (acoustics) , materials science , charge carrier , surface charge , ion , fluence , electron , ultrashort pulse , molecular physics , atomic physics , spectroscopy , chemical physics , optoelectronics , chemistry , laser , optics , physics , condensed matter physics , ecology , organic chemistry , quantum mechanics , composite material , biology
Ultrafast transient absorption spectroscopy is used to study subnanosecond charge dynamics in CdTe colloidal quantum dots. After treatment with chloride ions, these can become free of surface traps that produce nonradiative recombination. A comparison between these dots and the same dots before treatment enables new insights into the effect of surface trapping on ultrafast charge dynamics. The surface traps typically increase the rate of electron cooling by 70% and introduce a recombination pathway that depopulates the conduction band minimum of single excitons on a subnanosecond timescale, regardless of whether the sample is stirred or flowed. It is also shown that surface trapping significantly reduces the peak bleach obtained for a particular pump fluence, which has important implications for the interpretation of transient absorption data, including the estimation of absorption cross‐sections and multiple exciton generation yields.