Imaging the Ultrafast Photoelectron Transfer Process in Alizarin-TiO2.
In this work, we adopt a quantum mechanical approach based on time-dependent density functional theory (TDDFT) to study the optical and electronic properties of alizarin supported on TiO2 nano-crystallites, as a prototypical dye-sensitized solar cell. To ensure proper alignment of the donor (alizarin) and acceptor (TiO2 nano-crystallite) levels, static optical excitation spectra are simulated using time-dependent density functional theory in response. The ultrafast photoelectron transfer from the dye to the cluster is simulated using an explicitly time-dependent, one-electron TDDFT ansatz. The model considers the δ-pulse excitation of a single active electron localized in the dye to the complete set of energetically accessible, delocalized molecular orbitals of the dye/nano-crystallite complex. A set of quantum mechanical tools derived from the transition electronic flux density is introduced to visualize and analyze the process in real time. The evolution of the created wave packet subject to absorbing boundary conditions at the borders of the cluster reveal that, while the electrons of the aromatic rings of alizarin are heavily involved in an ultrafast charge redistribution between the carbonyl groups of the dye molecule, they do not contribute positively to the electron injection and, overall, they delay the process.
Dirección de Postgrado e Investigación, Universidad Autónoma de Chile, Llano Subercaceaux 2801, San Miguel, Santiago, Chile. tatiana.gomez@uautonoma.cl.
Tatiana
T
Gomez
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany. gunter.hermann@fu-berlin.de.
Gunter
G
Hermann
Dirección de Postgrado e Investigación, Universidad Autónoma de Chile, Llano Subercaceaux 2801, San Miguel, Santiago, Chile. ximena.zarate@uautonoma.cl.
Ximena
X
Zarate
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany. jperez@zedat.fu-berlin.de.
Jhon Fredy
JF
Pérez-Torres
Institut für Chemie und Biochemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany. jc.tremblay@fu-berlin.de.
Jean Christophe
JC
Tremblay
D000880:Anthraquinones / Q000737:chemistry*; D004583:Electrons; D021621:Imaging, Three-Dimensional; D008958:Models, Molecular; D008968:Molecular Conformation; D055668:Photochemical Processes; D013057:Spectrum Analysis; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
D000880:Anthraquinones; C009495:titanium dioxide; C010078:alizarin; D014025:Titanium
dye-sensitized solar cell; electronic flux density; optical spectra