title: Passivation of PbS Quantum Dot Surface with l-Glutathione in Solid-State Quantum-Dot-Sensitized Solar Cells.
abstract: Surface oxidation of quantum dots (QDs) is one of the biggest challenges in quantum dot-sensitized solar cells (QDSCs), because it introduces surface states that enhance electron-hole recombination and degrade device performance. Protection of QDs from surface oxidation by passivating the surface with organic or inorganic layers can be one way to overcome this issue. In this study, solid-state QDSCs with a PbS QD absorber layer were prepared from thin mesoporous TiO2 layers by the successive ionic layer adsorption/reaction (SILAR) method. Spiro-OMeTAD was used as the organic p-type hole transporting material (HTM). The effects on the solar cell performance of passivating the surface of the PbS QDs with the tripeptide l-glutathione (GSH) were investigated. Current-voltage characteristics and external quantum efficiency measurements of the solar cell devices showed that GSH-treatment of the QD-sensitized TiO2 electrodes more than doubled the short circuit current and conversion efficiency. Impedance spectroscopy, intensity-modulated photovoltage and photocurrent spectroscopy analysis of the devices revealed that the enhancement in solar cell performance of the GSH-treated cells originates from improved charge injection from PbS QDs into the conduction band of TiO2. Time-resolved photoluminescence decay measurements show that passivation of the surface of QDs with GSH ligands increases the exciton lifetime in the QDs.
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Askhat N
authors.initials: AN
authors.lastname: Jumabekov
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Cordes
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.|Department of Chemical & Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Siegler
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Pablo
authors.initials: P
authors.lastname: Docampo
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Alesja
authors.initials: A
authors.lastname: Ivanova
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Ksenia
authors.initials: K
authors.lastname: Fominykh
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Dana D
authors.initials: DD
authors.lastname: Medina
authors.affiliation: Department of Chemistry, University of Bath , Bath BA2 7AY, United Kingdom.
authors.forename: Laurence M
authors.initials: LM
authors.lastname: Peter
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), Ludwig-Maximilians-University Munich (LMU) , 81377 Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bein
keywords: impedance spectroscopy; lead sulfide; quantum dots; solar cells; surface passivation