title: Regenerative PbS and CdS quantum dot sensitized solar cells with a cobalt complex as hole mediator.
abstract: Metal sulfide (PbS and CdS) quantum dots (QDs) were prepared over mesoporous TiO2 films by improved successive ionic layer adsorption and reaction (SILAR) processes. The as-prepared QD-sensitized electrodes were combined with a cobalt complex redox couple [Co(o-phen)3]2+/3+ to make a regenerative liquid-type photovoltaic cell. The optimized PbS QD-sensitized solar cells exhibited promising incident photon-to-current conversion efficiency (IPCE) of over 50% and an overall conversion efficiency of 2% at 0.1 sun in a regenerative mode. The overall photovoltaic performance of the PbS QD-sensitized cells was observed to be dependent on the final turn of the SILAR process, giving a better result when the final deposition was Pb2+, not S2-. However, in the case of CdS QD-sensitized cells, S2- termination was better than that of Cd2+. The cobalt complex herein used as a regenerative redox couple was found to be more efficient in generating photocurrents from PbS QD cells than the typical hole scavenger Na2S in a three-electrode configuration. The CdS-sensitized cell with this redox mediator also showed better defined current-voltage curves and an IPCE reaching 40%.
authors.affiliation: Laboratory for Photonics and Interfaces, Institute of Chemical Sciences and Engineering, School of Basic Sciences, Swiss Federal Institute of Technology, CH-1015 Lausanne, Switzerland.
authors.forename: Hyo Joong
authors.initials: HJ
authors.lastname: Lee
authors.forename: Peter
authors.initials: P
authors.lastname: Chen
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Moon
authors.forename: Frédéric
authors.initials: F
authors.lastname: Sauvage
authors.forename: Kevin
authors.initials: K
authors.lastname: Sivula
authors.forename: Takeru
authors.initials: T
authors.lastname: Bessho
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Gamelin
authors.forename: Pascal
authors.initials: P
authors.lastname: Comte
authors.forename: Shaik M
authors.initials: SM
authors.lastname: Zakeeruddin
authors.forename: Sang Il
authors.initials: SI
authors.lastname: Seok
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.forename: Md K
authors.initials: MK
authors.lastname: Nazeeruddin