Journal article

Ultrafast relaxation dynamics of charge carriers in ZnO nanocrystalline thin films

Ultrafast spectroscopy was used to study the relaxation processes of charge carriers in ZnO nanocryst. thin films. A broad red-IR absorption band linked to shallowly trapped electrons was obsd. by spectroelectrochem. measurements. Femtosecond transient absorption data revealed multiexponential decays of the charge carriers with time consts. ranging from 1 to 400 ps. The decay profile of the signal shows a probe wavelength dependence. This effect is assigned to the trapping (localization) of nonequil. charge carriers which occurs on a time scale of ∼1 ps. The recombination of shallowly trapped electrons with deeply trapped holes, detd. by single-photon counting, mainly occurs in 400 ps.


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