Abstract-Time-resolved terahertz spectroscopy reveals the influence of charged sensitizing quantum dots on the electron dynamics in ZnO

Sesha Bamini N.,^ab   Hynek Němec,^c   Karel Žídek,^a  Mohamed Abdellah,^ad   Mohammed J. Al-Marri,^e  Pavel Chábera,^a   Carlito Ponseca,^a   Kaibo Zheng*^ae and  Tönu Pullerits*^a  

http://pubs.rsc.org/en/content/articlelanding/2017/cp/c6cp07509f#!divAbstract

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Corresponding authors

^a

Department of Chemical Physics and NanoLund, Lund University, Box 124, 22100 Lund, Sweden
 E-mail: kaibo.zheng@chemphys.lu.se,tonu.pullerits@chemphys.lu.se

^b

National Center for Ultrafast Processes, University of Madras, Chennai 600113, India

^c

Institute of Physics, Czech Academy of Sciences, Na Slovance 2, 18221 Prague, Czech Republic

^d

Department of Chemistry, Faculty of Science, South Valley University, Qena 83523, Egypt

^e

Gas Processing Center, College of Engineering, Qatar University, P.O. Box 2713, Doha, Qatar

Photoinitiated charge carrier dynamics in ZnO nanoparticles sensitized by CdSe quantum dots is studied using transient absorption spectroscopy and time-resolved terahertz spectroscopy. The evolution of the transient spectra shows that electron injection occurs in a two-step process, where the formation of a charge transfer state (occurring in several picoseconds) is followed by its dissociation within tens of picoseconds. The photoconductivity of electrons injected into the ZnO nanoparticles is lower than that of charges photogenerated directly in ZnO. We conclude that the motion of injected electrons in ZnO nanoparticles is strongly influenced by their interaction with positive charges left in the sensitizing quantum dots.

Abstract-Conductivity Mechanisms in Sb-doped SnO2 Nanoparticle Assemblies: Dc and Terahertz Regime

Volodymyr Skoromets , Hynek Němec , Jaromír Kopeček , Petr Kuzel , Kristina Peters , Dina Fattakhova-Rohlfing , Aliaksei Vetushka , Martin Müller , Kristína Ganzerová , and Antonin Fejfar

J. Phys. Chem. C, Just Accepted Manuscript

DOI: 10.1021/acs.jpcc.5b05091

Publication Date (Web): July 27, 2015

Copyright © 2015 American Chemical Societ

http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.5b05091

Assemblies of undoped and antimony-doped tin-oxide nanoparticles synthesized via non-aqueous sol-gel procedure, pressed into pellets, and annealed under various conditions were investigated using time-domain terahertz spectroscopy, scanning electron microscopy, atomic force microscopy and dc conductivity measurements. Combination of these methods made it possible to resolve the conductivity limitations imposed by intrinsic properties of the material and by the morphology of the samples. Percolation of the nanoparticles was confirmed in all samples. The undoped samples exhibit a weak hopping conductivity, whereas band-like conduction of charges partially confined in the nanoparticles dominates in the doped samples. The conductivity of nanoparticles and their connectivity can be greatly controlled during the sample preparation, namely by the calcination temperature and by the order of technological steps. Substantial increase of the conductivity inside nanoparticles and of the charge transport between them is achieved upon calcination at 500°C.

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Abstract-Electron and Hole Contributions to the Terahertz Photoconductivity of a Conjugated Polymer:Fullerene Blend Identified

 

http://pubs.acs.org/doi/abs/10.1021/jz301013u

 

Carlito S. Ponseca , Hynek Němec,  Nenad Vukmirovic , Sandra Fusco , Ergang Wang , Mats R. Andersson , Pavel Chabera , Arkady Petrovich Yartsev , and Villy Sundstrom

J. Phys. Chem. Lett., Just Accepted Manuscript

DOI: 10.1021/jz301013u

Publication Date (Web): August 17, 2012

Copyright © 2012 American Chemical Society

Time-resolved terahertz spectroscopy was employed for the investigation of charge transport dynamics in benzothiadiazolo-dithiophene polyfluorene ([2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3-benzothiadiazole)]) (APFO-3) polymers with various chain lengths and in its monomer form, all blended with an electron acceptor ([6,6]-phenyl-C61-butyric acid methyl ester, PCBM). Upon photoexcitation, charged polaron pairs are created, negative charges are transferred to fullerenes while positive polarons remain on polymers/monomers. Vastly different hole mobility in polymer and monomer blends allows us to distinguish the hole and electron contributions to the carrier mobility.