Because of their preferential two-dimensional layer-by-layer growth in thin films, 5,5′bis(4-alkylphenyl)-2,2′-bithiophenes (P2TPs) are model compounds for studying the effects of systematic chemical structure variations on thin-film structure and morphology, which in turn, impact the charge transport in organic field-effect transistors. For the first time, we observed, by grazing incidence X-ray diffraction (GIXD), a strong change in molecular tilt angle in a monolayer of P2TP, depending on whether the alkyl chain on the P2TP molecules was of odd or even length. The monolayers were deposited on densely packed ultrasmooth self-assembled alkane silane modified SiO2 surfaces. Our work shows that a subtle change in molecular structure can have a significant impact on the molecular packing structure in thin film, which in turn, will have a strong impact on charge transport of organic semiconductors. This was verified by quantum-chemical calculations that predict a corresponding odd–even effect in the strength of the intermolecular electronic coupling.

A real case study and characterisation of modern energy efficient windows allowing mobile communication is presented. An earlier study had shown that laser scribing of energy saving coatings allows highly reducing the microwave attenuation (from 30 to 1-3 dB) using a wide band-pass frequency-selective surface (FSS) while preserving the thermal quality of the window. To achieve large-scale production, the laser scribing technique has been further developed. The effect of laser scribing on the mechanical properties of a substrate has been determined through mechanical strength tests. Moreover, the insulating properties of the window have been analysed to ensure the reliability of this technology. As a real case demonstration, an entire train has been equipped with prototype windows. The signal quality has been controlled for a wide band of frequencies and for existing technologies such as long term evolution, universal mobile telecommunication system, multiple input multiple output and for different configurations such as a stationary and a moving train.

In order to reduce the energy consumption of buildings, modern windows include metal-containing coatings. These coatings strongly attenuate the microwaves used for mobile communications. Here, we present a novel approach to improve radio signal transmission by structuring a low emissivity coating. Laser ablation is used to scribe a line pattern on the coating. The microwave attenuation of the initial coating ranges between-25 and-30 dB between 850 MHz and 3 GHz. The optimized patterning reduces it down to-1.2 ± 0.6 dB. The fraction of the ablated area is relatively low. Our experimental results show that it is possible to reach a level of attenuation close to that of a glass substrate by removing less than 4% of the coating area. The ablated lines are thin enough to not be noticed in most common lighting situations. Therefore, we achieve a dual spectral selectivity: the coated glass is transparent in the visible range, reflective in the infrared and nearly as transparent as its glass substrate to microwaves. Additionally, numerical simulations were performed and show that the attenuation at grazing incidences is dominated by the behaviour of the glass substrate. To the best of our knowledge, it is the first time that experimental evidence for the combination of such properties is reported and that detailed experimental data are compared to numerical simulations. We anticipate that our findings will be of major importance for the building and transportation sectors.

The sector of transportation accounts for about one third of the total energy consumption in Switzerland. A monitoring campaign of the energy consumption of a regional train revealed the critical energyconsuming systems. Heating, cooling and ventilation were identified as major consumers. Windows are a source of non-controlled heat transfer. In summer, it may result in overheating leading to larger cooling loads while in winter, it is an important source of thermal losses. Selective double glazing and solar protection coatings can reduce these effects. Angular-dependent optical properties of a selective double glazing have been measured, and the solar heat gain coefficient (g value) was determined. An estimation of the solar gains received by a panoramic waggon was performed using the monitored solar irradiation and the measured properties of the glazing. These data were compared to the heating and cooling energy consumption monitored in this waggon. Solar gains were found to be in the same order of magnitude that the heating energy during some sunny days. They were also compared to the estimated thermal losses through the glazing and the entire envelope. These results show that the solar gains play a nonnegligible role in the energy balance of the waggon. Furthermore, thermal simulations were performed to evaluate the solar gains in different conditions. It showed that 7 to 13% of energy can be saved using the glazing adapted to the climatic conditions. In addition, improving the thermal insulation of the train envelope or equipping the train with an efficient heat recovery system can lead to significant energy savings.

No abstract