Spectrum-Dependent Spiro-OMeTAD Oxidization Mechanism in Perovskite Solar Cells

We propose a spectrum-dependent mechanism for the oxidation of 2,2′,7,7′-tetrakis­(<i>N</i>,<i>N</i>-di-<i>p</i>-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) with bis­(trifluoromethane)­sulfonimide lithium salt (LiTFSI), which is commonly used in perovskite solar cells as the hole transport layer. The perovskite layer plays different roles in the Spiro-OMeTAD oxidization for various spectral ranges. The effect of oxidized Spiro-OMeTAD on the solar cell performance was observed and characterized. With the initial long-wavelength illumination (>450 nm), the charge recombination at the TiO₂/Spiro-OMeTAD interface was increased due to the higher amount of the oxidized Spiro-OMeTAD. On the other hand, the increased conductivity of the Spiro-OMeTAD layer and enhanced charge transfer at the Au/Spiro-OMeTAD interface facilitated the solar cell performance

As shown in the load-displacement of the lumbar vertebrae, the compressive strength at the first significant decrease of slope of the load displacement curve was the failure load and the stiffness was the slope of linear region of load-displacement curve.

<p>As shown in the load-displacement of the lumbar vertebrae, the compressive strength at the first significant decrease of slope of the load displacement curve was the failure load and the stiffness was the slope of linear region of load-displacement curve.</p

Scatter plots showing relationship between BMD and failure load in subgroup A, B and C.

<p>Scatter plots showing relationship between BMD and failure load in subgroup A, B and C.</p

The mean stiffness and standard deviation of the normal BMD, osteoporotic and serious osteoporotic group.

<p>“*” stands for the presence of statistical difference between the subgroup B and C; “**” stands for the presence of statistical difference between the subgroup A and C; “***” stands for the statistical intergroup difference of subgroup A among the three BMD groups; “****” stands for the statistical intergroup difference of subgroup B among the three BMD groups; “*****” stands for the statistical intergroup difference of subgroup C among the three BMD groups. </p

H- and J‑Aggregation of Fluorene-Based Chromophores

Understanding of H- and J-aggregation behaviors in fluorene-based polymers is significant both for determining the origin of various red-shifted emissions occurring in blue-emitting polyfluorenes and for developing polyfluorene-based device performance. In this contribution, we demonstrate a new theory of the H- and J-aggregation of polyfluorenes and oligofluorenes, and understand the influence of chromosphere aggregation on their photoluminescent properties. H- and J-aggregates are induced by a continuous increasing concentration of the oligofluorene or polyfluorene solution. A relaxed molecular configuration is simulated to illustrate the spatial arrangement of the bonding of fluorenes. It is indicated that the relaxed state adopts a 2₁ helical backbone conformation with a torsion angle of 18° between two connected repeat units. This configuration makes the formation of H- and J-aggregates through the strong π–π interaction between the backbone rings. A critical aggregation concentration is observed to form H- and J-aggregates for both polyfluorenes and oligofluorenes. These aggregates show large spectral shifts and distinct shape changes in photoluminescent excitation (PLE) and emission (PL) spectroscopy. Compared with “isolated” chromophores, H-aggregates induce absorption spectral blue-shift and fluorescence spectral red-shift but largely reduce fluorescence efficiency. “Isolated” chromophores not only refer to “isolated molecules” but also include those associated molecules if their conjugated backbones are not compact enough to exhibit perturbed absorption and emission. J-aggregates induce absorption spectral red-shift and fluorescence spectral red-shift but largely enhance fluorescence efficiency. The PLE and PL spectra also show that J-aggregates dominate in concentrated solutions. Different from the excimers, the H- and J-aggregate formation changes the ground-state absorption of fluorene-based chromophores. H- and J-aggregates show changeable absorption and emission derived from various interchain interactions, unlike the β phase, which has relatively fixed absorption and emission derived from an intrachain interaction

Lumbar spines (L1-L5) collected from fresh cadavers were used for biomechanical tests in the current study (a); Bony endplate was exposed by removing the soft tissue (b); After removing the posterior elements and endplate preparation, each lumbar vertebra was placed at the fixture of the material testing system and then the axial compression test was conducted under the displacement control mode (c).

<p>Lumbar spines (L1-L5) collected from fresh cadavers were used for biomechanical tests in the current study (a); Bony endplate was exposed by removing the soft tissue (b); After removing the posterior elements and endplate preparation, each lumbar vertebra was placed at the fixture of the material testing system and then the axial compression test was conducted under the displacement control mode (c).</p

Scatter plots showing relationship between BMD and stiffness in subgroup A, B and C.

<p>Scatter plots showing relationship between BMD and stiffness in subgroup A, B and C.</p

The mean failure load and standard deviation of the normal BMD, osteoporotic and serious osteoporotic group.

<p>“*” stands for the presence of statistical difference between the subgroup B and C; “**” stands for the presence of statistical difference between the subgroup A and C; “***” stands for the statistical intergroup difference of subgroup A among the three BMD groups; “****” stands for the statistical intergroup difference of subgroup B among the three BMD groups; “*****” stands for the statistical intergroup difference of subgroup C among the three BMD groups. </p

Synthesis and Characterization of the Hole-Conducting Silica/Polymer Nanocomposites and Application in Solid-State Dye-Sensitized Solar Cell

Hole-conducting silica/polymer nanocomposites exhibit interesting physical and chemical properties with important applications in the field of energy storage and hybrid solar cells. Although the conventional strategy of grafting hole-conducting polymer onto the surface of silica nanoparticles is to use in situ oxidative polymerization, a promising alternative of using surface-initiated controlled living radical polymerization has arisen to anchor the polymer on the silica. The resulting silica/polymer nanocomposites from the latter method are more chemically and thermally stable because of the strong covalent bonding compared to the electrostatic interaction from in situ polymerization. The use of these nanocomposites mixed with spiro-MeOTAD (2,2′,7,7′-tetrakis­(<i>N</i>,<i>N</i>-di-<i>p</i>-methoxyphenylamine)-9,9′-spirobifluorene) as a new hole conductor in the application of solid-state dye-sensitized solar cell (ss-DSSC) is reported here. The power conversion efficiency of this ss-DSSC is higher than the full spiro-MeOTAD ss-DSSC. Notably, the short circuit current improves by 26%. It is explained by large size silica/polymer nanocomposites forming an additional light scattering layer on the top of photoanode. This is the first time a conductive light scattering layer is introduced into ss-DSSC to enhance cell performance

Summary of pre- and postoperative SACS(°) in relation to the levels involved.

<p>No., number; SACS, sagittal alignment of the whole cervical spine; Preop, preoperative; Postop, postoperative.</p