Orbital alignment at the internal interface of arylthiol functionalized CdSe molecular hybrids

Journal Article · Tue Apr 21 00:00:00 EDT 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4918364· OSTI ID:22402893

Li, Zhi; Schlaf, Rudy ^[1]; Mazzio, Katherine A.; Okamoto, Ken; Luscombe, Christine K. ^[2]

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1. Department of Electrical Engineering, University of South Florida, Tampa, Florida 33620 (United States)
2. Department of Materials Science and Engineering and Molecular Engineering and Sciences Institute, University of Washington, Box 352120, Seattle, Washington 98195-2120 (United States)

Organic-inorganic nanoparticle molecular hybrid materials are interesting candidates for improving exciton separation in organic solar cells. The orbital alignment at the internal interface of cadmium selenide (ArS-CdSe) hybrid materials functionalized with covalently attached arylthiolate moieties was investigated through X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A physisorbed interface between arylthiol (ArSH) ligands and CdSe nanoparticles was also investigated for comparison. This interface was created via a multi-step thin film deposition procedure in-vacuo, where the surface was characterized after each experimental step. This enabled the direct comparison of ArSH/CdSe interfaces produced via physisorption and ArS-CdSe covalently attached hybrid materials, which rely on a chemical reaction for their synthesis. All material depositions were performed using an electrospray deposition, which enabled the direct injection of solution-originating molecular species into the vacuum system. This method allows XPS and UPS measurements to be performed immediately after deposition without exposure to the atmosphere. Transmission electron microscopy was used to determine the morphology and particle size of the deposited materials. Ultraviolet-visible spectroscopy was used to estimate the optical band gap of the CdSe nanoparticles and the HOMO-LUMO gap of the ArSH ligands. These experiments showed that hybridization via covalent bonds results in an orbital realignment at the ArSH/CdSe interface in comparison to the physisorbed interface. The orbital alignment within the hybrid caused a favorable electron injection barrier, which likely facilitates exciton-dissociation while preventing charge-recombination.

• OSTI ID: 22402893
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 15; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CADMIUM SELENIDES
CHEMICAL BONDS
COMPARATIVE EVALUATIONS
COVALENCE
ELECTRON BEAM INJECTION
EXCITONS
INTERFACES
MORPHOLOGY
NANOPARTICLES
ORGANIC SOLAR CELLS
PARTICLE SIZE
RECOMBINATION
SURFACES
THIN FILMS
THIOLS
TRANSMISSION ELECTRON MICROSCOPY
ULTRAVIOLET RADIATION
X-RAY PHOTOELECTRON SPECTROSCOPY