Influence of the electron-cation interaction on electron mobility in dye-sensitized ZnO and TiO2 nanocrystals: a study using ultrafast terahertz spectroscopy.
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.
Nemec
H
H
Department of Chemical Physics, Lund University, Getingevägen 60, Box 124, 221 00 Lund, Sweden.
Rochford
J
J
Taratula
O
O
Galoppini
E
E
Kuzel
P
P
Polívka
T
T
Yartsev
A
A
Sundström
V
V
D000042:Absorption; D004396:Coloring Agents / Q000737:chemistry*; D004553:Electric Conductivity; D004579:Electron Transport; D004583:Electrons; D007700:Kinetics; D009010:Monte Carlo Method; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D012666:Semiconductors; D013057:Spectrum Analysis; D014025:Titanium / Q000737:chemistry*; D015034:Zinc Oxide / Q000737:chemistry*
D004396:Coloring Agents; C009495:titanium dioxide; D014025:Titanium; D015034:Zinc Oxide