Additive-free, Cost-Effective Hole-Transporting Materials for Perovskite Solar Cells Based on Vinyl Triarylamines.

A series of cost-effective hole-transporting materials (TOP-HTMs) for perovskite solar cells (PSCs) was designed and synthesized. The molecules, composed of multiple 4,4'-dimethoxytriphenylamines linked to a benzene core via trans-vinylene units, can be manufactured from inexpensive materials through a simple synthetic route. The photophysical, electrochemical, and thermal properties, as well as hole mobilities, were strongly influenced by the position and number of vinyl triarylamine substituents on the core benzene ring. CH3NH3PbI3-based solar cells using the X-shaped TOP-HTM 3 with additives gave a high power conversion efficiency of 17.5% (forward scan)/18.6% (reverse scan). Crucially, TOP-HTMs gave high working device efficiency without the need for conduction-enhancing additives. The power conversion efficiency for the device with additive-free TOP-HTM 3 was 16.0% (forward scan)/16.6% (reverse scan). Device stability is also enhanced and is superior to the reference HTM, 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD).

Calixazulenes: azulene-based calixarene analogues - an overview and recent supramolecular complexation studies.

Some of the least studied calixarenes are those that consist of azulene rings bridged by -CH2- groups. Since Lash and Colby's discovery of a simple and convenient method for producing the parent all-hydrocarbon calix[4]azulene, there have been two other all-hydrocarbon calix[4]azulenes which have been synthesized in good yields by their method. This allowed studying their supramolecular properties. This report is of our latest work on the solution-state supramolecular complexation of one of these calix[4]azulenes, namely tetrakis(5,7-diphenyl)calix[4]azulene or "OPC4A", with several electron-deficient tetraalkyammonium salts. As a result of more recent methods developed by us and others employing Suzuki-Miyaura cross-coupling reactions to produce additional functionalized azulenes, the promise of further greater functionalized calixazulenes lies in store to be investigated.

Oxygen-Bridged Diphenylnaphthylamine as a Scaffold for Full-Color Circularly Polarized Luminescent Materials.

An oxygen-bridged diphenylnaphthylamine with a helical shape was designed and synthesized as a key scaffold for circularly polarized luminescent (CPL) materials. The introduction of electron-withdrawing groups, such as formyl and 2,2-dicyanovinyl substituents at the naphthyl moiety in this skeleton effectively decreases the LUMO level and thus allows a tuning of the band gap. The prepared model compounds exhibit intense CPL signals with a dissymmetry factor (g value) of 10-3 both in CH2Cl2 solutions and in the solid states. The emission colors of these derivatives are influenced both by the substituents as well as by solvent effects, covering the whole visible region from blue to deep red.

Photo-excitation intensity dependent electron and hole injections from lead iodide perovskite to nanocrystalline TiO2 and spiro-OMeTAD.

Photo-excitation intensity dependent electron and hole injections from CH3NH3PbI3 perovskite to nanocrystalline TiO2 and spiro-OMeTAD are presented with the electron injection yield decrease from 95% to 10% and the hole injection yield decrease from 99% to 50% by increasing the excitation intensity from 10 nJ cm(-2) to 50 µJ cm(-2).

Hole-Transporting Materials with a Two-Dimensionally Expanded π-System around an Azulene Core for Efficient Perovskite Solar Cells.

Two-dimensionally expanded π-systems, consisting of partially oxygen-bridged triarylamine skeletons that are connected to an azulene (1-3) or biphenyl core (4), were synthesized and characterized. When tetra-substituted azulene 1 was used as a hole-transporting material (HTM) in perovskite solar cells, the observed performance (power conversion efficiency = 16.5%) was found to be superior to that of the current HTM standard Spiro-OMeTAD. A comparison of the hole mobility, the ability to control the HOMO and LUMO levels, and the hole-collection efficiency at the perovskite/HTM interface in 1 with reference compounds (2-4 and Spiro-OMeTAD) led to the elucidation of key factors required for HTMs to act efficiently in perovskite solar cells.

Dynamic Optical Properties of CH3NH3PbI3 Single Crystals As Revealed by One- and Two-Photon Excited Photoluminescence Measurements.

The dynamic optical properties of perovskite CH3NH3PbI3 single crystals were studied by means of time-resolved photoluminescence (PL) spectroscopy at room temperature. The PL peak under one-photon excitation exhibits a red-shift with elapsing time, while two-photon PL is time-independent and appears at lower energy levels. The low-energy two-photon PL can be attributed to emissions from the localized states because of strong band-to-band absorption and photon re-absorption of the emitted light in the interior region. We revealed that the PL behaviors can be explained by the diffusion of photocarriers generated in the near-surface region to the interior region. The excitation fluence dependence of the one-photon PL dynamics is also discussed in terms of the electron-hole radiative recombination and carrier diffusion effects.

Excimer formation in organic emitter films associated with a molecular orientation promoted by steric hindrance.

White emission with two sharp strong peaks - a molecular emission peak at 455 nm and an excimer emission peak at 591 nm - was obtained by introducing a terphenyl group into a highly twisted core chromophore, which promoted a molecular orientation in the film state suitable for excimer formation.

On-top π-stacking of quasiplanar molecules in hole-transporting materials: inducing anisotropic carrier mobility in amorphous films.

Dimers of partially oxygen-bridged triarylamines were designed and synthesized as hole-transporting materials. X-ray structural analyses revealed that these compounds form on-top π-stacking aggregates in the crystalline state. TRMC measurements showed that high levels of anisotropic charge transport were induced in the direction of the π-stacking. Surprisingly, even in vacuum-deposited amorphous films, these compounds retained some of the face-on π-stacking, thus facilitating an out-of-plane carrier mobility.

Local levels of interleukin-1beta, -4, -6 and tumor necrosis factor alpha in an experimental model of murine osteomyelitis due to staphylococcus aureus.

The purpose of this study is to evaluate local levels of interleukin-1 beta (IL-1 beta), -4 (IL-4), -6 (IL-6), and tumour necrosis factor-alpha (TNF-alpha), in a model of murine osteomyelitis due to Staphylococcus aureus. Cytokine levels in supernatants derived from bone homogenates were determined by enzyme-linked immunosorbent assay, for 28 days following the direct implantation of murine tibiae with S.aureus. Levels of IL-1 beta and IL-6 in infected bone were elevated in the early post-infection period and then decreased. In contrast, TNF-alpha levels remained elevated 3 to 28 days post-infection, while IL-4 levels were elevated late in the course of infection. The histopathology of infected bone showed predominant infiltration of inflammatory cells and bone resorption 3 to 7 days after infection, and bone resorption and adjacent areas of formation 14 to 28 days after infection. These results suggest that the elevated IL-1 beta and IL-6 levels induced by infection may be related to bone damage mainly in the early phase of infection, and that TNF-alpha and IL-4 may at least in part be associated with histopathological changes, including both bone resorption and formation in the later phase of this osteomyelitis model.

Inhibitory effect of roxithromycin on the local levels of bone-resorbing cytokines in an experimental model of murine osteomyelitis.

OBJECTIVES: The purpose of this study was to evaluate the inhibitory effect of roxithromycin on the production of interleukin (IL)-1beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) in a murine tibial osteomyelitis model using Staphylococcus aureus. METHODS: Cytokine levels in supernatants derived from bone homogenates were measured by enzyme-linked immunosorbent assay for 28 days, after oral administration of roxithromycin at 5 mg/kg/day. RESULTS: There was no significant difference in IL-6 levels between a group receiving roxithromycin administration and a group not receiving roxithromycin. IL-1beta and TNF-alpha levels were significantly lower for the administration group after 7-14 days and after 21-28 days, respectively. However, a significant difference in bacterial counts in bone between the groups was not observed. CONCLUSION: These results indicate that roxithromycin suppresses the local expression of IL-1beta and TNF-alpha, and may exhibit an anti-inflammatory effect in this osteomyelitis model.