Influence of the electron-cation interaction on electron mobility in dye-sensitized ZnO and TiO.sub.2./sub. nanocrystals: a study using ultrafast terahertz spectroscopy

0350369 - FZÚ 2011 RIV US eng J - Journal Article
Němec, Hynek - Rochford, J. - Taratula, O. - Galoppini, E. - Kužel, Petr - Polívka, T. - Yartsev, A. - Sundström, V.
Influence of the electron-cation interaction on electron mobility in dye-sensitized ZnO and TiO₂ nanocrystals: a study using ultrafast terahertz spectroscopy.
Physical Review Letters. Roč. 104, č. 19 (2010), 197401/1-197401/4. ISSN 0031-9007. E-ISSN 1079-7114
R&D Projects: GA ČR(CZ) GP202/09/P099; GA AV ČR(CZ) IAA100100902; GA MŠMT LC512
Institutional research plan: CEZ:AV0Z10100520
Keywords : ultrafast dynamics * terahertz spectroscopy * semiconductor nanocrystals * dye-sensitized semiconductors
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 7.621, year: 2010

Charge transport and recombination in nanostructured semiconductors are poorly understood key processes in dye-sensitized solar cells. We have employed time-resolved spectroscopies in the terahertz and visible spectral regions supplemented with Monte Carlo simulations to obtain unique information on these processes. Our results show that charge transport in the active solar cell material can be very different from that in nonsensitized semiconductors, due to strong electrostatic interaction between injected electrons and dye cations at the surface of the semiconductor nanoparticle. For ZnO, this leads to formation of an electron-cation complex which causes fast charge recombination and dramatically decreases the electron mobility even after the dissociation of the complex. Sensitized TiO2 does not suffer from this problem due to its high permittivity efficiently screening the charges.
Permanent Link: http://hdl.handle.net/11104/0190387