title: Effect of an adsorbent on recombination and band-edge movement in dye-sensitized TiO2 solar cells: evidence for surface passivation.
abstract: The mechanism by which the adsorbent guanidinium affects the open-circuit photovoltage of dye-sensitized TiO2 nanocrystalline solar cells was investigated. The influence of the guanidinium cation on the rate of recombination and band-edge movement was measured by transient photovoltage. When guanidinium is present in the electrolyte recombination becomes slower by a factor of about 20. At the same time, the adsorbent causes the band edges to move downward, toward positive electrochemical potentials, by 100 mV. The collective effect of both a downward shift of the band edges and slower recombination, owing to the presence of guanidinium, results in an overall improvement in the open-circuit photovoltage.
authors.affiliation: National Renewable Energy Laboratory, Golden, Colorado 80401-3393, USA. Nikos_Kopidakis@nrel.gov
authors.forename: Nikos
authors.initials: N
authors.lastname: Kopidakis
authors.forename: Nathan R
authors.initials: NR
authors.lastname: Neale
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Frank