Photoinduced charge carrier dynamics of Zn-porphyrin-TiO2 electrodes: the key role of charge recombination for solar cell performance.
Time resolved absorption spectroscopy has been used to study photoinduced electron injection and charge recombination in Zn-porphyrin sensitized nanostructured TiO(2) electrodes. The electron transfer dynamics is correlated to the performance of dye sensitized solar cells based on the same electrodes. We find that the dye/semiconductor binding can be described with a heterogeneous geometry where the Zn-porphyrin molecules are attached to the TiO(2) surface with a distribution of tilt angles. The binding angle determines the porphyrin-semiconductor electron transfer distance and charge transfer occurs through space, rather than through the bridge connecting the porphyrin to the surface. For short sensitization times (1 h), there is a direct correlation between solar cell efficiency and amplitude of the kinetic component due to long-lived conduction band electrons, once variations in light harvesting (surface coverage) have been taken into account. Long sensitization time (12 h) results in decreased solar cell efficiency because of decreased efficiency of electron injection.
Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan. imahori@scl.kyoto-u.ac.jp
Hiroshi
H
Imahori
Soonchul
S
Kang
Hironobu
H
Hayashi
Mitsutaka
M
Haruta
Hiroki
H
Kurata
Seiji
S
Isoda
Sophie E
SE
Canton
Yingyot
Y
Infahsaeng
Arunkumar
A
Kathiravan
Torbjörn
T
Pascher
Pavel
P
Chábera
Arkady P
AP
Yartsev
Villy
V
Sundström
D004566:Electrodes; D004583:Electrons; D005456:Fluorescent Dyes / Q000737:chemistry*; D008665:Metalloporphyrins / Q000737:chemistry*; D015394:Molecular Structure; D049329:Nanostructures / Q000737:chemistry; D010316:Particle Size; D055668:Photochemical Processes; D012666:Semiconductors; D012993:Solar Energy; D013237:Stereoisomerism; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
D005456:Fluorescent Dyes; D008665:Metalloporphyrins; C009495:titanium dioxide; D014025:Titanium; D015032:Zinc