Effect of Solvent and Substrate on the Surface Binding Mode of Carboxylate-Functionalized Aromatic Molecules

Journal Article · Wed Apr 25 00:00:00 EDT 2018 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.8b01526· OSTI ID:1457402

Domenico, Janna ^[1]; Foster, Michael E. ^[2]; Spoerke, Erik D. ^[3]; Allendorf, Mark D. ^[2]; Sohlberg, Karl ^[1]

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1. Drexel Univ., Philadelphia, PA (United States)
2. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Here, the efficiency of dye-sensitized solar cells (DSSCs) is strongly influenced by dye molecule orientation and interactions with the substrate. Understanding the factors controlling the surface orientation of sensitizing organic molecules will aid in the improvement of both traditional DSSCs and other devices that integrate molecular linkers at interfaces. Here, we describe a general approach to understand relative dye–substrate orientation and provide analytical expressions predicting orientation. We consider the effects of substrate, solvent, and protonation state on dye molecule orientation. In the absence of solvent, our model predicts that most carboxylic acid-functionalized molecules prefer to lie flat (parallel) on the surface, due to van der Waals interactions, as opposed to a tilted orientation with respect to the surface that is favored by covalent bonding of the carboxylic acid group to the substrate. When solvation effects are considered, however, the molecules are predicted to orient perpendicular to the surface. We extend this approach to help understand and guide the orientation of metal–organic framework (MOF) thin-film growth on various metal–oxide substrates. A two-part analytical model is developed on the basis of the results of DFT calculations and ab initio MD simulations that predicts the binding energy of a molecule by chemical and dispersion forces on rutile and anatase TiO₂ surfaces, and quantifies the dye solvation energy for two solvents. The model is in good agreement with the DFT calculations and enables rapid prediction of dye molecule and MOF linker binding preference on the basis of the size of the adsorbing molecule, identity of the surface, and the solvent environment. We establish the threshold molecular size, governing dye molecule orientation, for each condition.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1457402
• Report Number(s): SAND--2018-1500J; 660646
• Journal Information: Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 20 Vol. 122; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY