Ultrafast Charge Dynamics in Trap‐Free and Surface‐Trapping Colloidal Quantum Dots

Advanced Science

Charles T. Smith²  Marina A. Leontiadou²  Robert Page¹  Paul O'Brien¹ 

[1] School of Chemistry, University of Manchester, Manchester, UK;School of Physics and Astronomy and Photon Science Institute, University of Manchester, Manchester, UK

关键词: nanocrystals;    quantum dots;    surface trapping;    transient absorption;    ultrafast spectroscopy;   

DOI  :  10.1002/advs.201500088

来源: Wiley

【 摘 要 】

Abstract

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.

【 授权许可】

CC BY   
© 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.