Diffusion of tin from TEC-8 conductive glass into mesoporous titanium dioxide in dye sensitized solar cells

The photoanode of a dye sensitized solar cell is typically a mesoporous titanium dioxide thin film adhered to a conductive glass plate. In the case of TEC-8 glass, an approximately 500 nm film of tin oxide provides the conductivity of this substrate. During the calcining step of photoanode fabrication, tin diffuses into the titanium dioxide layer. Scanning Electron Microscopy and Electron Dispersion Microscopy are used to analyze quantitatively the diffusion of tin through the photoanode. At temperatures (400 to 600 °C) and times (30 to 90 min) typically employed in the calcinations of titanium dioxide layers for dye sensitized solar cells, tin is observed to diffuse through several micrometers of the photoanode. The transport of tin is reasonably described using Fick\u27s Law of Diffusion through a semi-infinite medium with a fixed tin concentration at the interface. Numerical modeling allows for extraction of mass transport parameters that will be important in assessing the degree to which tin diffusion influences the performance of dye sensitized solar cells

Modeling Diffusion of Tin into the Mesoporous Titanium Dioxide Layer of a Dye-Sensitized Solar Cell Photoanode

Dye-sensitized solar cells (DSSC) utilize a photoanode consisting of a mesoporous semiconducting thin film coated onto a conductive substrate. Typically, the semiconductor is composed of titanium dioxide nanoparticles and the conductive substrate is a thin layer of fluorine-doped tin oxide on glass. Scanning electron microscopy coupled with energy dispersion spectroscopy (SEM/EDS) has been used to investigate mass transport of tin from the conductive layer into the mesoporous semiconductor. EDS maps of tin distribution through the photoanode cross section have been modeled using Fick’s second law of diffusion. Photoanodes fabricated using a doctor-blading method and sintering at temperatures ranging from 450 to 600 °C exhibit tin distributions in the TiO2 layer corresponding to tin diffusion coefficients between 3.2 × 10–5 and 59 × 10–5 μm2 s–1. Diffusion of tin into the glass substrate is also observed, but at lower rates. The magnitude of the tin in TiO2 diffusion coefficient is consistent with diffusion through grain boundaries

Modeling Diffusion of Tin into the Mesoporous Titanium Dioxide Layer of a Dye-Sensitized Solar Cell Photoanode

Dye-sensitized solar cells (DSSC) utilize a photoanode consisting of a mesoporous semiconducting thin film coated onto a conductive substrate. Typically, the semiconductor is composed of titanium dioxide nanoparticles and the conductive substrate is a thin layer of fluorine-doped tin oxide on glass. Scanning electron microscopy coupled with energy dispersion spectroscopy (SEM/EDS) has been used to investigate mass transport of tin from the conductive layer into the mesoporous semiconductor. EDS maps of tin distribution through the photoanode cross section have been modeled using Fick’s second law of diffusion. Photoanodes fabricated using a doctor-blading method and sintering at temperatures ranging from 450 to 600 °C exhibit tin distributions in the TiO₂ layer corresponding to tin diffusion coefficients between 3.2 × 10^–5 and 59 × 10^–5 μm² s^–1. Diffusion of tin into the glass substrate is also observed, but at lower rates. The magnitude of the tin in TiO₂ diffusion coefficient is consistent with diffusion through grain boundaries

The roles of oxygen vacancies, electrolyte composition, lattice structure, and doping density on the electrochemical reactivity of Magneli phase TiO2 anodes

Substoichiometric TiO2 (TinO2n-1, 4 n 10) is a promising and cost-effective material, that is being investigated for many applications, such as information storage, energy storage and conversion, and water treatment. Upon extended anodic polarization, TinO2n-1 reportedly suffers from gradual loss in conductivity and electrochemical reactivity. In this study, the surface deactivation and reactivation mechanisms were examined on a TinO2n-1 monolithic electrode in three different electrolyte solutions (i.e., H2SO4, HClO4, HCl). The intrinsic electronic properties, charge transfer kinetics, crystalline structure, and surface composition were examined experimentally after anodic and cathodic polarizations. Statistically equivalent results were obtained from local scanning electrochemical microscopy (SECM) and bulk electrochemical impedance spectroscopy measurement, which indicate that spatially resolved SECM data accurately characterized charge transfer kinetics of the TinO2n-1 electrode at the micron-scale. Results indicate that decreases in conductivity and charge transfer kinetics after anodic polarizations in all three electrolytes were primarily attributed to the loss of charge carriers, such as H+ discharge at Ti3+ point donor sites, and the process was reversible during cathodic polarization via H+ intercalation. In the H2SO4 electrolyte reversible surface passivation also occurred, which was attributed to the formation of TiOSO4 surface species whose presence were supported by experimental measurements and density functional theory calculations. It was also determined that the TinO2n-1 crystal structure directly affected the hydroxyl radical formation rate, with the highest rate observed for Ti4O7, which also possessed the highest charge carrier density

Fracture Toughness and Impact Properties of Laminated Metal Composites

Laminated metal composites consist of alternating metal (or metal matrix composite) layers bonded together. These materials can provide fracture toughness and impact properties superior to those of the component materials. These properties are a function of component material properties, laminate architecture (volume fraction, thickness) and interface properties. Properties are compared for seven lightweight materials

Elucidating the Solution-Phase Structure and Behavior of 8-Hydroxyquinoline Zinc in DMSO

The solution-phase structure and electronic relaxation dynamics of zinc bis-8-hydroxyquinoline [Zn(8HQ)2] in dimethyl sulfoxide (DMSO) were examined using a broad array of spectroscopic techniques, complimented by ab initio calculations of molecular structure. The ground-state structure was determined using extended X-ray absorption fine structure (EXAFS) data collected on the Zn K-edge and diffusion ordered spectroscopy (DOSY) NMR. The complex was found to be monomeric and octahedral, with two bidentate 8-hydroxyquinolate ligands and two DMSO molecules coordinated to the zinc through oxygen atoms. Electronic relaxation dynamics were examined with ultrafast transient absorption spectroscopy and complementary density functional calculations. Electronic relaxation was observed to proceed through both singlet and triplet pathways. This solution-phase data provides a deeper physical understanding of the behavior of this molecule, which has a variety of uses such as sensing, OLEDs, and biological applications

Elucidating the Solution-Phase Structure and Behavior of 8-Hydroxyquinoline Zinc in DMSO

The solution-phase structure and electronic relaxation dynamics of zinc bis-8-hydroxyquinoline [Zn(8HQ)2] in dimethyl sulfoxide (DMSO) were examined using a broad array of spectroscopic techniques, complimented by ab initio calculations of molecular structure. The ground-state structure was determined using extended X-ray absorption fine structure (EXAFS) data collected on the Zn K-edge and diffusion ordered spectroscopy (DOSY) NMR. The complex was found to be monomeric and octahedral, with two bidentate 8-hydroxyquinolate ligands and two DMSO molecules coordinated to the zinc through oxygen atoms. Electronic relaxation dynamics were examined with ultrafast transient absorption spectroscopy and complementary density functional calculations. Electronic relaxation was observed to proceed through both singlet and triplet pathways. This solution-phase data provides a deeper physical understanding of the behavior of this molecule, which has a variety of uses such as sensing, OLEDs, and biological applications

Elucidating the Solution-Phase Structure and Behavior of 8‑Hydroxyquinoline Zinc in DMSO

The solution-phase structure and electronic relaxation dynamics of zinc bis-8-hydroxyquinoline [Zn­(8HQ)₂] in dimethyl sulfoxide (DMSO) were examined using a broad array of spectroscopic techniques, complimented by ab initio calculations of molecular structure. The ground-state structure was determined using extended X-ray absorption fine structure (EXAFS) data collected on the Zn K-edge and diffusion ordered spectroscopy (DOSY) NMR. The complex was found to be monomeric and octahedral, with two bidentate 8-hydroxyquinolate ligands and two DMSO molecules coordinated to the zinc through oxygen atoms. Electronic relaxation dynamics were examined with ultrafast transient absorption spectroscopy and complementary density functional calculations. Electronic relaxation was observed to proceed through both singlet and triplet pathways. This solution-phase data provides a deeper physical understanding of the behavior of this molecule, which has a variety of uses such as sensing, OLEDs, and biological applications