title: Quantifying Geometric Strain at the PbS QD-TiO₂ Anode Interface and Its Effect on Electronic Structures.
abstract: Quantum dots (QDs) show promise as the absorber in nanostructured thin film solar cells, but achieving high device efficiencies requires surface treatments to minimize interfacial recombination. In this work, lead sulfide (PbS) QDs are grown on a mesoporous TiO2 film with a crystalline TiO2 surface, versus one coated with an amorphous TiO2 layer by atomic layer deposition (ALD). These mesoporous TiO2 films sensitized with PbS QDs are characterized by X-ray and electron diffraction, as well as X-ray absorption spectroscopy (XAS) in order to link XAS features with structural distortions in the PbS QDs. The XAS features are further analyzed with quantum simulations to probe the geometric and electronic structure of the PbS QD-TiO2 interface. We show that the anatase TiO2 surface structure induces PbS bond angle distortions, which increases the energy gap of the PbS QDs at the interface.
authors.affiliation: Department of Mechanical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Orlando
authors.initials: O
authors.lastname: Trejo
authors.affiliation: Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.|Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Roelofs
authors.affiliation: Department of Mechanical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Shicheng
authors.initials: S
authors.lastname: Xu
authors.affiliation: Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.|Laboratory for Materials Chemistry, National Institute of Chemistry , Ljubljana 1000, Slovenia.
authors.forename: Manca
authors.initials: M
authors.lastname: Logar
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Ritimukta
authors.initials: R
authors.lastname: Sarangi
authors.affiliation: Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
authors.forename: Dennis
authors.initials: D
authors.lastname: Nordlund
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Anup L
authors.initials: AL
authors.lastname: Dadlani
authors.affiliation: Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Rob
authors.initials: R
authors.lastname: Kravec
authors.affiliation: Department of Mechanical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Dasgupta
authors.affiliation: Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Stacey F
authors.initials: SF
authors.lastname: Bent
authors.affiliation: Department of Mechanical Engineering, Stanford University , Stanford, California 94305, United States.|Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
authors.forename: Fritz B
authors.initials: FB
authors.lastname: Prinz
keywords: X-ray absorption near edge structure; X-ray absorption spectroscopy; atomic layer deposition; density functional theory; quantum dot; sensitized solar cell