The current work aimed to demonstrate the application of a technique where white light interferometry (WLI) and Laue X-ray crystallography scanner characterisation were combined to study the chemical etching response of diamond cut multi-crystalline Si (mc-Si) wafers. Using this technique, the effect of different texturing additives (isopropyl alcohol, natrium hypochlorite) was evaluated by examining the topography of the mc-Si surfaces before and after etching. The etching responses of monocrystalline Si wafers of (1 0 0), (1 1 0) and (1 1 1) orientations were used as reference for comparison with the multi-crystalline wafers investigated. The texturing results illustrated the influence of different crystal-orientations on the etching rate. It was revealed that for the mc-Si wafers, the etching speed of the different crystal grain-planes is increasing with their crystallographic similarity with the main (hkl) planes (100, 110,111). The comparison of isopropyl alcohol (IPA) and sodium hypochlorite (NaOCl) additives to KOH solutions showed that NaOCl additive is favourable for the polishing of mc-Si wafers, while IPA can be used as polishing only for crystal grains close to the (1 1 1) orientation.

The presented work is focusing on optical interference coatings on the back side of the front glass for crystalline silicon-based photovoltaic modules. We present results on how such coatings can be designed to obtain desired visual properties combined with a limited loss in power conversion efficiency. This colouring technology may therefore be very attractive for building integrated photovoltaics. Coating design parameters such as number of layers, design wavelength, layer thicknesses, and layer refractive indices affect both the visual appearance parameters and the efficiency. Important colour parameters are lightness, chroma, and hue, and we demonstrate how these colour parameters are influenced by the design parameters of the optical interference coating. Using optical interference coatings to create colours results in colours that are dependent on the observation angle. We have introduced a new parameter for quantification of angular colour dependence. Our results show that the angular colour dependence can be reduced by increasing the refractive indices of the interference coating.For many building projects it may be highly desired to combine high power conversion efficiency with certain visual properties. The results from our work also indicate some of the possibilities and challenges in this regard.

This work is dedicated to developing a method of combined surface morphology- and crystallographic analysis for crystalline silicon. To demonstrate the applicability of the method, a series of chemical operations, such as polishing and texturing, were applied to multi-crystalline silicon samples. The samples were pre- and post-analysed with WLI and Laue techniques, and the experimental data allowed construction of maps for crystal orientation to etching rate dependency. The study illustrates the strengths of the combinatory technique as an alternative to existing techniques such as atom force microscopy (AFM) and electron backscatter diffraction (EBSD). • Combination of LAUE tool and white light interferometry techniques. • Alternative time-effective method to EBSD. • Analysis of surface morphology and crystallographic properties for chemical processing.

Facade integrated photovoltaics (FIPV) is an emerging and essential way to utilize solar energy in built environment. However, there is limited architectural study of FIPV, especially addressing the topic of colour performance. This study developed a theoretical method with pixelated colour design for integrating opaque coloured photovoltaics on building facades. The city of Trondheim in Norway was taken as a case study. Two main facade prototypes for FIPV were derived from Trondheim's urban context. Typical hues for the two facade prototypes were selected from Trondheim's urban colour palette, and colour harmony strategies were applied as design guidelines to generate NCS colour combinations for FIPV. Then a series of pixelated FIPV designs was proposed. The aesthetic performance of the proposed pixelated FIPV designs was tested through an online survey among architects, urban designers and laypersons from different countries. A 5-level semantic differential scaling was employed for aesthetic evaluation. The results demonstrated that the FIPV concept was widely supported by participants, while the proposed pixelated FIPV designs were aesthetically preferred and considered as coherent with urban context by the majority of participants. Besides, the energy production efficiencies of proposed designs were calculated. Pixelated coloured FIPV facades showed promising energy production efficiency (theoretically about 85-93% of black PV facades). The overall facade lightness demonstrated a much stronger influence on efficiency than hue. This study presented a promising pixelization method for FIPV design, through which a balanced FIPV performance including pleasing facade aesthetic quality, satisfied urban integration, and high energy production efficiency could be achieved.

Building integrated photovoltaics (BIPV) has attracted increased commercial interest in recent years due to a growing focus on efficient utilization of land area and local renewable energy generation. Aesthetic aspects must be considered when photovoltaic panels are applied as building elements. Colours can be added by reflecting some of the sunlight that otherwise could have been utilized for electricity generation. Reflectance spectra of commercial solar cell modules have been measured and analysed. Relative efficiency loss caused by the reflected solar radiation energy has been calculated. The calculated losses in efficiency based on measured spectra have been compared to model spectra with colour coordinates corresponding to RAL colours as well as more idealized monochromatic spectra. The analysis shows that the most important colour parameter affecting loss is the lightness. The second most important parameter is the hue of the colour, with green-yellow colours having the lowest loss, and pink colours resulting in the highest loss, when colours with the same lightness are compared. A Colour Performance Index (CPI) given by luminous reflectance divided by relative loss has been proposed as a figure of merit, thus allowing for a useful comparison of colours with different lightness. (C) 2019 The Authors. Published by Elsevier B.V.

Scaling in distribution pipes for secondary alumina is a major issue in aluminium smelters. The scale is formed inside the distribution pipes, and gradually reduces the cross section that is available for alumina transport. The scale cannot be removed without dismantling the transport pipes and using chemical and/or mechanical treatments. This leads to interruptions in normal operation, requires additional labour, and a stock of additional pipe sections. To get a better understanding of the scale formation mechanisms, the rate of scale growth was monitored by acoustic measurements in a transport pipe section at an aluminium producing plant over a period of several months. Correlation between growth rate, and recorded parameters from the associated pots, fume treatment system and meteorological data were studied. In addition, samples from the actual scale were examined by SEM, TEM and AFM to investigate the microstructure and chemical composition.

The temperature of a surface that is exposed to sunlight is influenced by the solar reflectance and the infrared emittance of the surface. A coating that reduces the surface temperature is often referred to as a cool coating. Cool coatings on building surfaces have several potential benefits, such as reduction of energy needed for cooling, improved thermal comfort, and mitigation of the urban heat island effect. In addition to low weight, aluminium is a metal that is known for its excellent reflectance properties. Recycled aluminium is now increasingly requested by the building market, both due to reduced cost as well as for environmental considerations. For building applications, surface treatments and coatings that completely hide the aluminium substrate are needed in order to obtain an attractive appearance, good corrosion properties and overall protection against outdoor environments. We see a need for a low-cost approach that can be used to obtain a cool coating on aluminium sheet. For this we have developed several different one-layer coating systems that can be applied in a coil-coating process. A total of 8 different coloured pigments with low absorption in the near infrared have been investigated with the goal to make cool coatings with various desirable colours. The coated surfaces achieved high solar reflectance by utilizing the excellent reflectance properties of the aluminium substrate. Good hiding of the substrate in the visible range and high infrared emittance has also been obtained. The colours include black and different shades of red, orange and yellow. Solar reflectance spectra and infrared reflectance spectra have been measured. From these spectra, optical properties of the coated surface such as total solar reflectance (TSR), infrared emittance and solar reflectance index (SRI) have been calculated. In addition, we also present results from weathering testing of the coated materials. The results show that the one-layer approach can be used to obtain cool coatings with high near infrared transmittance that are feasible to apply in a coil coating process.

Homogenous aSi1−xAlxHy alloyed thin films, made by magnetron sputtering, has been found to exhibit tunable band gap and dielectric constant depending on their composition. The optical properties of alloys are largely defined by their electronic structure, which is is strongly influenced by interatomic charge transfer. In this work we have quantified interatomic charge transfer between Si, Al and H in aSi1−xAlxHy thin-films, with and . Charge transfer was found experimentally using x-ray photoelectron spectroscopy, by incorporating Auger parameter data into the Thomas and Weightman model. Both the perfect and imperfect screening models were tested, and the results were compared to models calculated using density functional theory based molecular dynamics. Using imperfect screening properties of Si and Al resulted in an excellent agreement between the experimental and computational results. Alloying aSi with Al is associated with donation of electrons from Al to Si for y  =  0. For y  >  0 electrons are transferred away from both Al and Si. The change in Si valence charge increases linearly with increasing band gap and decreasing dielectric constant. These relationships can be used as a quick guide for the evaluation of the Si valence charge and subsequently optoelectronic properties, at specific Al/Si ratios.

Thin films of homogeneous mixture of amorphous silicon and aluminum were produced with magnetron sputtering using 2-phase Al–Si targets. The films exhibited variable compositions, with and without the presence of hydrogen, aSi1−xAlx and aSi1−xAlxHy. The structure and optical properties of the films were investigated using transmission electron microscopy, X-ray photoelectron spectroscopy, UV-VisNIR spectrometry, ellipsometry, and atomistic modeling. We studied the effect of alloying aSi with Al (within the range 0–25 at. %) on the optical band gap, refractive index, transmission, and absorption. Alloying aSi with Al resulted in a non-transparent film with a low band gap (<1 eV). Hydrogenation of the films increased the band gap to values >1 eV. Variations of the Al and hydrogen content allowed for tuning of the optoelectronic properties. The films are stable up to a temperature of 300 °C. At this temperature, we observed Al induced crystallization of the amorphous silicon and the presence of large Al particles in a crystalline Si matrix.

An experimental study has been performed on the interrelationship between visual appearance, surface topography and light scattering on AA6063-T6 aluminium extrusions etched to a depth of up to 700μm. The topography was characterized by use of White Light Interferometry (WLI), and light scattering was measured by use of a glossmeter and photogoniometer. The main parameters for the visual appearance evaluation were gloss, directionality, streakiness and homogeneity. This combined approach of visual assessment and measurements provides valuable insight into how measurable quantities relate to the perceived visual appearance for industrially relevant aluminium surfaces.

Optical properties of single diatom frustule valves from two different Coscinodiscus species (C. wailesii and C. centralis) are studied by transmission confocal hyperspectral imaging and numerical calculations. Light convergence, concentration, and trapping effects are observed and depend on both the wavelength and the valve orientation. These effects seem to occur independently of the incident light angle. From our results, a wavelength-dependent multifocal lens behavior can be explained by light diffraction related to the radial symmetry of the multiscaled 3D nanostructure.

Employing two recently developed X-ray imaging techniques, we investigated methods for observing moisture at different length scales in organic fibers and textiles. Using the coherent diffractive imaging technique of ptychographic tomography, structural features in a single coated wool fiber in both dry and humid conditions were observed at about 200 nm resolution. The reconstructed three-dimensional images yield quantitative information about the spatial density distribution in the fiber, showing that the fiber swells laterally by 8–9% in humid conditions. We further explore the applicability of grating interferometry, also known as Talbot imaging, for studying humidity transport in woven cotton, with a resolution on the order of 100 µm and a field of view of a few square centimeters. Grating interferometry inherently gives access to three complementary imaging modalities, namely absorption-, phase- and dark-field contrast, and we demonstrate that all of them are valuable and provide complementary information for the purpose of monitoring moisture in textiles.

Biological structures harvesting sunlight have evolved for several millions of years in different ways to optimize conversion efficiency. One of the most noteworthy examples of optical bio-nanostructures is the complex silica nanoporous frustule surrounding diatoms (unicellular algae). Diatoms have recently attracted significant attention for their potential in photonic applications [1]. Coscinodiscus wailesii diatom frustules have been shown to combine photonic band gap and waveguide properties resulting in a wavelength dependent light focusing effect. Our experimental and computational results show the dependence between the spatial distribution of light transmitted through a single Coscinodiscus wailesii frustule and the wavelength. We used hyperspectral transmission mapping measurements to study the optical properties of single frustules of Coscinodiscus centralis (CC) and Coscinodiscus wailesii (CW) diatoms. Our aim is to provide a new insight on these properties using direct visualization of the light distribution after transmission through diatom frustules with different structures.

A novel method for the conversion of diatom bio-silica structures into nano-porous 3D silicon/magnesium silicon nitride replicas utilising simultaneous metallothermic reduction and nitriding is described. Optical, chemical and structural characterization of the replicas is also presented.

We address the metal organic frameworks UiO-6x (x = 6, 7, 8), their band gaps, and the changes in the band gaps upon perturbations in the metal-organic framework structures. Computational studies were performed with complementary experimental band gap measurements. Band gap modulations upon hydrogen substitutions by NH2 and NO2 on the organic linker, hydroxylation and dehydroxylation of the metal center, different linker lengths (x = 6, 7, 8), and Ti and Hf substitutions for Zr were analyzed in detail. The origin of the band gap changes was thoroughly investigated, and this work confirmed a reduction in the band gap upon NH2 and NO2 substitutions. Furthermore, this work explicitly illustrated that changes in the band gap were also observed by changing the coordination around the Zr atom, whereas isovalent substitutions on the metal center did not yield significant perturbations of the band gap.

Interaction forces and adhesion between a silica sphere and a flat silica surface in aqueous electrolyte solutions were investigated by atomic force microscopy. The forces were measured as a function of surface separation, pH and NaCl concentration as the surfaces were approaching each other. The adhesion force was determined upon retraction with respect to pH, NaCl concentration and contact time. The magnitude of the long range repulsive force was decreasing with decreasing pH. A short range repulsive force was observed at pH = 2, but no long range repulsive forces were observed at this pH. Force measurements showed that adhesion of silica surfaces in water was obstructed by short and long range repulsive forces. Adhesion was enhanced when both the long and the short range repulsive force was mitigated. A maximum adhesion force of 7.8 mN/m was measured at pH = 12.5 when the short range force vanished and the long range repulsive force was reduced by increasing the NaCl concentration. At pH = 12.5, the work of adhesion was calculated to be 1.2 mJ/m2 according to the Derjaguin–Muller–Toporov (DMT) model. Adhesion energy was much less at pH = 2 (0.3 mJ/m2) due to persistive short range repulsion.

A novel method is used to predict the reflection losses in cover glass for PV-modules. For vertical south oriented modules the method predicts that asymmetric V-grooves improve annual transmission by 1.3% compared to symmetric V-grooves.

This work reports on an experimental investigation of the potential of using selected commercially available organic conductive polymers as active ingredients in thermocouples printed on textiles. Poly(3, 4-ethylenedioxythiophene): poly(4styrenesulfonate) (PEDOT:PSS) and polyaniline (PANI) were screen printed onto woven cotton textile. The influence of multiple thermocycles between 235 K (-38°C) and 350 K (+77°C) on resistivity and thermoelectric properties was examined. The Seebeck coefficients of PEDOT:PSS and PANI were found to be about +18 μV/K and +15 uV/K, respectively, when "metal-polymer" thermocouples were realized by combining the polymer with copper. When "polymer-polymer" thermocouples were formed by combining PEDOT:PSS and PANI, a thermoelectric voltage of about +10 μV/K was observed. A challenge recognized in the experiments is that the generated voltage exhibited drift and fluctuations.

The paper presents the electro-optical design of an interferometric inspection system for massive parallel inspection of Micro(Opto) ElectroMechanicalSystems (M(O)EMS). The basic idea is to adapt a micro-optical probing wafer to the M(O)EMS wafer under test. The probing wafer is exchangeable and contains a micro-optical interferometer array: a low coherent interferometer (LCI) array based on a Mirau configuration and a laser interferometer (LI) array based on a Twyman-Green configuration. The interference signals are generated in the micro-optical interferometers and are applied for M(O)EMS shape and deformation measurements by means of LCI and for M(O)EMS vibration analysis (the resonance frequency and spatial mode distribution) by means of LI. Distributed array of 5x5 smart pixel imagers detects the interferometric signals. The signal processing is based on the "on pixel" processing capacity of the smart pixel camera array, which can be utilised for phase shifting, signal demodulation or envelope maximum determination. Each micro-interferometer image is detected by the 140 x 146 pixels sub-array distributed in the imaging plane. In the paper the architecture of cameras with smart-pixel approach are described and their application for massive parallel electro-optical detection and data reduction is discussed. The full data processing paths for laser interferometer and low coherent interferometer are presented.

The paper introduces different approaches to overcome the large ratio between wafer size and feature size in micro production. The EU-project SMARTIEHS develops a new concept for high volume M(O)EMS testing. The design of the test station is presented and the advancements compared to the state of the art are introduced within the following fields: micro-optical laser interferometer (LI) design, DOE-based microinterferometer production, smart-pixel camera and signal processing for resonance frequency and vibration amplitude distribution determination. The first experiments performed at LI demonstrator are also reported.