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Dye-anchoring modes at the dye...TiO2 interface of n3- and n749-sensitized solar cells revealed by glancing-angle pair distribution function analysis

DOI: 10.1021/acs.jpcc.0c02314 DOI Help

Authors: Karim T. Mukaddem (University of Cambridge; Research Complex at Harwell) , Philip A. Chater (Diamond Light Source) , Leon R. Devereux (University of Cambridge) , Othman K. K. Al Bahri (University of Cambridge; Research Complex at Harwell) , Apoorv Jain (University of Cambridge) , Jacqueline M. Cole (University of Cambridge; Research Complex at Harwell; ISIS Neutron and Muon Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: May 2020
Diamond Proposal Number(s): 16036 , 19288

Abstract: The efficient transport of electrons from the sunlight-harvesting dye molecules into the electrical circuit of a dye-sensitized solar cell (DSSC) is imperative to its effective operation. A dye···semiconductor interface comprises the working electrode of a DSSC. Dye molecules adsorb onto the semiconductor surface, whereupon they transfer electronic charge into the conduction band of the semiconductor; this process initiates the electrical circuit. It is therefore important to characterize this interfacial structure in order to understand how efficiently the dye binds, or anchors, onto the semiconductor surface and imparts charge transfer to it. Armed with such knowledge, the performance of DSSCs may then be improved systematically. The structural determination of a thin-film interface is nonetheless a challenging task. We herein report the results of a glancing-angle pair distribution function (gaPDF) experiment that generated synchrotron x-ray diffraction patterns of N3- and N749-sensitized DSSC working electrodes. This gaPDF experimental approach represents the first diffraction-based strategy for the characterization of intact DSSC working electrodes. The gaPDF structural signatures were compared with PDFs simulated from two possible interfacial structures that were computed using density functional theory (DFT); these simulated structures showed the dyes anchoring in two distinct modes: a bridging bidentate and a monodentate ester configuration. The differences between the experimental observation and these simulated structures revealed a preference for each dye, N3 and N749, to adopt a bidentate bridging dye anchoring mode when sensitized onto TiO2. This work not only demonstrates the successful application of a gaPDF method to DSSC research, it also advocates the applicability of gaPDF to many types of thin-film samples.

Subject Areas: Physics, Chemistry, Energy

Instruments: I15-1-X-ray Pair Distribution Function (XPDF)