Electrolyte/Dye/TiO₂ Interfacial Structures of Dye-Sensitized Solar Cells Revealed by In Situ Neutron Reflectometry with Contrast Matching

Abstract

The nature of an interfacial structure buried within a device assembly is often critical to its function. For example, the dye/TiO2 interfacial structure that comprises the working electrode of a dye-sensitized solar cell (DSC) governs its photovoltaic output. These structures have been determined outside of the DSC device, using ex situ characterization methods; yet, they really should be probed while held within a DSC since they are modulated by the device environment. Dye/TiO2 structures will be particularly influenced by a layer of electrolyte ions that lies above the dye self-assembly. We show that electrolyte/dye/TiO2 interfacial structures can be resolved using in situ neutron reflectometry with contrast matching. We find that electrolyte constituents ingress into the self-assembled monolayer of dye molecules that anchor onto TiO2. Some dye/TiO2 anchoring configurations are modulated by the formation of electrolyte/dye intermolecular interactions. These electrolyte-influencing structural changes will affect dye-regeneration and electron-injection DSC operational processes. This underpins the importance of this in situ structural determination of electrolyte/dye/TiO2 interfaces within representative DSC device environments.

Characterizing Interfacial Structures of Dye-Sensitized Solar Cell Working Electrodes

“…It should be noted here that the position of the Li + cations (top layer) was attributed tentatively to charge neutrality, given the lack of evidence that they ingress into the dye layer. Reproduced with permission from ref . Copyright 2021 American Chemical Society.…”

“…To improve the spatial resolution and experimental accuracy of in-situ NR measurements that characterize dye···TiO 2 interfacial structures within fully assembled DSC devices, our group has recently developed an in-situ NR method based on contrast matching. , Contrast matching more fully exploits the isotope-specific neutron-scattering cross sections of an element to discriminate scattering from atomic structures within a particular part of a device. For example, neutron scattering from an individual layer of a multilayer structure can be blended into that of a neighboring layer by partially deuterating it in such a fashion that the overall SLD of that layer matches that of this neighboring layer.…”

“…This is the essence of the methodology used in this in-situ NR experiment, whereby partial deuteration of the acetonitrile solvent is used to tailor a contrast match between layers within a DSC device. Dye···TiO 2 interfacial structures that contain N3 , N749 , or MK-2 dyes were chosen as subject materials …”

Ruthenium‐based complex dyes for dye‐sensitized solar cells

“…Among them, ruthenium‐based complex dyes having diverse structures, high efficiency, and good stability have caught much attention in DSC community. [ 2–5 ] This paper reviews only the ruthenium‐based complex dyes developed in our laboratory and a few highly related ruthenium sensitizers reported in the literature. For readers' convenience, the ruthenium complex dyes were introduced according to the number and coordination sites of the ligands.…”

Adsorption Thermodynamic and Kinetic Mechanism of Substrate-Induced Molecular Geometry Orientation

“…A functional molecular modification interface is a research focus and has applications in many fields. The photovoltaic conversion can be enhanced by utilizing nanosemiconductor surfaces modified with Ru­(II) complexes that have a visible light response . A new structure of solar cells, namely, dye-sensitized solar cells, can be constructed based on this photosensitization effect. − The Ru­(II) complex commonly used is the N719 dye ( cis -[Ru­(4-carboxy-4′-carboxylate-2,2′-bipyridine) 2 (NCS) 2 ]), which contains two carboxylic acid groups, two carboxylate groups, and two isothiocyanato (NCS) ligands .…”