Advanced Functional Materials

A solution-processed organic photovoltaic tandem cell (see figure and cover) is demonstrated that is constructed from two polymers (PTBEHT/PCBM, PFDTBT/PCBM) with complementary absorption spectra that absorb from the UV to the near-IR. The tandem solar cell is electrically connected in series and the open-circuit voltage of the tandem is the sum of the open-circuit voltages of the two subcells.

Electrotunable non-reciprocal light transmittance and unidirectional circularly polarized lasing are shown for an anisotropic optical heterojunction structure—a phase-retarding nematic liquid crystal (NLC) layer sandwiched between two polymer cholesteric liquid crystal (PCLC) films. Reorienting of the NLC molecules under applied voltage (see figure) and selective reflection by the PCLC films lead to electroswitchable lasing and electrotunable lasing.

Fluorescent self-assembled liquid gels are prepared for the first time through the use of a gelator showing aggregation-induced enhanced emission. The photoluminescence, arising from the fibrous aggregates of the gelator (see figure), can be repeatedly switched by an electric field. Modulating the excitation light through electric-field- induced liquid crystal orientation offers new ways to achieve and explore electrically controllable photoluminescence. Figure width: 200 μm.

Uniform magnetite, hematite, and goethite nanocrystals are obtained through an attractive method based on an oleic acid/alcohol/water system. All the products can be well dispersed in a cyclohexane solvent to form transparent colloids with vivid colors (see figure). The influence of the preparation conditions as well as the magnetic properties of doped magnetite particles are revealed.

Morphological control of polymer microstructure is pursued as a strategy to improve proton conductivity and minimize swelling due to hydration in proton exchange membrane fuel cells (see figure). A highly fluorinated comb-shaped polymer, which forms distinct microphase separated domains (figure inset) resulting in membranes with relatively high proton conductivities and correspondingly low degrees of swelling, is prepared.

A functionalized polyoxophosphotungstate–titania/titanium hybrid electrode (POW–TiO₂/Ti; see figure) is fabricated by encapsulating POW nanoaggregates into a TiO₂ nanotube array. Its chemical stability and photocatalytic and photoelectrocatalytic activities are shown to be markedly superior to those of POW roughly aggregated onto the surface of a multiporous TiO₂ film.

The control of interfacial charge transfer is of key importance in the design of solid-state dye-sensitized solar cells. Using a series of novel triarylamine-type hole conductors (see figure) that vary in molecular weight and mobility, the factors determining charge transfer at the dye/hole conductor interface have been determined.

Aqueous dispersions of functionalized carbon nanotube (f-CNT) complexes with plasmid DNA are studied using UV-vis luminescence spectrophotometry (see figure). The measured fluorescence intensity is correlated with the aggregation state of the f-CNTs: a high intensity indicates improved f-CNT individualization and dispersion, while a decrease in fluorescence intensity indicates a higher degree of nanotube aggregation and bundling.

Synthesis of Te-based bulk optical glasses containing 70 to 80 % Te in a Ga–Ge–Te system is reported. The optical transmission window of these glasses is exceptional, ranging from 1.99 to 28 μm, making them suitable for the production of far-infrared-transmitting optical fibers (see figure), desirable for fabrication of nulling interferometers for space applications such as on the Darwin mission.

A variety of alkyl hydroperoxides have been functionalized onto ordered mesoporous SBA-15 from their corresponding covalently anchored synthons (see figure). tert-Hydroperoxides are prepared by autoxidation using molecular O₂, whereas primary hydroperoxides are obtained by reaction with H₂O₂. The silica-supported alkyl hydroperoxides exhibit high activity in the epoxidation of styrene to styrene epoxide.

Interconnectivity in the channels of pentacene TFTs can be enhanced by two-step deposition (1st layer 10 nm: 0.1 Å s^–1, 2nd layer 40 nm: 4.0 Å s^–1) (see figure). A smaller number of voids is observed at the interface between the pentacene film and insulator, which results in field-effect mobilities as high as 1.2 cm² V^–1 s^–1. This approach to improving the quality of small-molecule active layers will be beneficial to TFT production.

pH-responsive polymer pumps composed of a porous membrane with linear-grafted poly(methacrylic acid) (PMAA) gates acting as functional valves and a crosslinked poly(N,N-dimethylaminoethyl methacrylate) (PDM) hydrogel inside the reservoir are a novel route to “smart” controlled-release systems. The cooperative, simultaneous pH responses of the acidic- and basic-responsive polymers accelerate the responsive release rate by a pumping effect (see figure).

The near-infrared emission intensities of Er³⁺ions in encapsulated Er³⁺—dendrimer complexes are dramatically enhanced on increasing the generation number of the dendrons, owing to light-harvesting and site-isolation effects (see figure). The energy-transfer (ET) efficiency between the dendritic anthracene ligands and Ln³⁺ via the excited singlet-state was evaluated as being in the range of 90 to 97 %.

The graphic shows a possible structure of a Ru^II complex covalently grafted within cetyltrimethylammoniumbromide template-directed mesostructured silica. It is possible to covalently graft the Ru^II complex onto mesosphered silica for oxygen sensing. The mesostructured oxygen sensors show superior properties to those of amorphous samples. Uniformity, improved sensitivity, and a simplified calibration sensor can also be obtained.

Fabrication of photonic crystals infiltrated with PbS quantum dots (QDs) offers a promising route to all-optical limiters. An approach to preparing polymer colloidal crystals heavily loaded with PbS QDs in the interstitial space is reported. The approach uses capillary forces to infiltrate PbS QDs into interstitial spaces and produces high-quality photonic crystals with uniform loading of PbS QDs (see figure).

A solution-processed organic photovoltaic tandem cell (see figure and cover) is demonstrated that is constructed from two polymers (PTBEHT/PCBM, PFDTBT/PCBM) with complementary absorption spectra that absorb from the UV to the near-IR. The tandem solar cell is electrically connected in series and the open-circuit voltage of the tandem is the sum of the open-circuit voltages of the two subcells.

Nanometric LiNi_0.5Mn_1.5O₄ prepared using a polymer-assisted method can be used as a cathode in lithium cells with expanded rate capabilities, excellent coulombic efficiency, and the ability to withstand fast-charge–slow-discharge processes (see figure). This results from the combination of nanometer-sized particles with high crystallinity, which is enhanced by the presence of the polymer during the synthetic procedure.