Quantifying Geometric Strain at the PbS QD-TiO₂ Anode Interface and Its Effect on Electronic Structures

Orlando Trejo; Katherine E Roelofs; Shicheng Xu; Manca Logar; Ritimukta Sarangi; Dennis Nordlund; Anup L Dadlani; Rob Kravec; Neil P Dasgupta; Stacey F Bent; Fritz B Prinz

doi:10.1021/acs.nanolett.5b02373

Quantifying Geometric Strain at the PbS QD-TiO₂ Anode Interface and Its Effect on Electronic Structures

Nano Lett. 2015 Dec 9;15(12):7829-36. doi: 10.1021/acs.nanolett.5b02373. Epub 2015 Nov 13.

Authors

Orlando Trejo¹, Katherine E Roelofs^{2

3}, Shicheng Xu¹, Manca Logar^{3

4}, Ritimukta Sarangi⁵, Dennis Nordlund⁵, Anup L Dadlani⁶, Rob Kravec², Neil P Dasgupta⁷, Stacey F Bent², Fritz B Prinz^{1

3}

Affiliations

¹ Department of Mechanical Engineering, Stanford University , Stanford, California 94305, United States.
² Department of Chemical Engineering, Stanford University , Stanford, California 94305, United States.
³ Department of Materials Science and Engineering, Stanford University , Stanford, California 94305, United States.
⁴ Laboratory for Materials Chemistry, National Institute of Chemistry , Ljubljana 1000, Slovenia.
⁵ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory , Menlo Park, California 94025, United States.
⁶ Department of Chemistry, Stanford University , Stanford, California 94305, United States.
⁷ Department of Mechanical Engineering, University of Michigan , Ann Arbor, Michigan 48109, United States.

PMID: 26554814
DOI: 10.1021/acs.nanolett.5b02373

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.

Keywords: X-ray absorption near edge structure; X-ray absorption spectroscopy; atomic layer deposition; density functional theory; quantum dot; sensitized solar cell.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.