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Abstract Optical solutions are promising for Perovskite solar cell (PSC) technology, not only to increase efficiency, but also to allow thinner absorber layers (higher flexibility) and improve stability. This work optimized the combined anti-reflection and scattering properties of two types of light trapping (LT) structures, based on TiO 2 semi-spheroidal geometries with honeycomb periodicity, for application in PSCs with substrate configuration and different perovskite layer thicknesses. Their optically lossless material (TiO 2) allows the structures to be patterned in the final processing steps, integrated in the cells' top n contact, therefore not increasing the surface area of the PV layers and not degrading the electric performance via recombination. Therefore, this strategy circumvents the typical compromise of state-of-the-art LT approaches between optical improvements and electrical deterioration, which is particularly relevant for PSCs since their main recombination is caused by surface defects. When patterned on the cells' front, the wave-optical micro-features composing the LT structures yield up to 21% and 27% photocurrent enhancement in PSCs with conventional (500 nm thick) and ultra-thin (250 nm) perovskite layers, respectively; which are improvements close to those predicted by theoretical Lambertian limits. In addition, such features are shown to provide an important encapsulation role, preventing the cells' degradation from UV penetration. Graphical abstract fx1 Highlights • Novel light trapping designs optimized for high-efficient Perovskite solar cells. • Wave-optical front structures provide strong VIS anti-reflection & NIR scattering. • Incorporation in n contact prevents electric degradation while boosting absorption. • Record photocurrent enhancement (35%) demonstrated in thin (250 nm) Perovskite cell. • Photonic structures act as UV blocking layer, enhancing Perovskite cell stability. [ABSTRACT FROM AUTHOR]

The interaction of light with wavelength-sized photonic nanostructures is highly promising for light management applied to thin-film photovoltaics. Several light trapping effects come into play in the wave optics regime of such structures that crucially depend on the parameters of the photonic and absorbing elements. Thus, multi-parameter optimizations employing exact numerical models, as performed in this work, are essential to determine the maximum photocurrent enhancement that can be produced in solar cells. Generalized spheroidal geometries and high-index dielectric materials are considered here to model the design of the optical elements providing broadband absorption enhancement in planar silicon solar cells. The physical mechanisms responsible for such enhancement are schematized in a spectral diagram, providing a deeper understanding of the advantageous characteristics of the optimized geometries. The best structures, composed of TiO 2 half-spheroids patterned on the cells' top surface, yield two times higher photocurrent (up to 32.5 mA/cm 2 in 1.5 µm thick silicon layer) than the same devices without photonic schemes. These results set the state-of-the-art closer to the theoretical Lambertian limit. In addition, the considered light trapping designs are not affected by the traditional compromise between absorption enhancement versus current degradation by recombination, which is a key technological advantage. [ABSTRACT FROM AUTHOR]

A new method for depositing PDMS directly onto conductive carbon yarns is proposed to produce Triboelectric Nanogenerator Yarns (TENG yarns) that can serve as the basic building blocks for energy scavenging wearables. The in-situ PDMS curing method described in this study allows the fast formation of a uniform thick coating over conductive surfaces regardless of their roughness. Single-electrode configuration TENG yarns are developed and their electrical output is optimized by precisely adjusting the PDMS layer thickness and by changing the chemical and physical nature of the carbon fiber (CF) yarns' surface. Functionalizing the CF yarns' surface with ZnO rods combined with porous PDMS coating can enhance their electrical output. The best results are achieved using this type of TENG yarns with an average diameter of 1.74 mm, which can be obtained after only 3 min of PMDS deposition by " in-situ " curing method. A maximum of 72 V peak-to-peak and 10 µA (74.1 µW cm−2 of power density with a load resistance of 20 MΩ) is reached when applying an impact force of 600 N to a set of five TENG yarns connected in parallel. The output is stable even after 10,000 cycles and this set of TENG yarns is also able to light at least 28 LEDs when tapping by hand, proving a contribute towards the development of basic building blocks to power the future generation of wearables. R. Barras and co-workers explore a new technique for the production of TENG yarns. This new deposition method features the fast formation of uniform thick and porous coatings of PDMS over conductive carbon fiber surfaces by in-situ curing using joule effect. A maximum power density of 74.1 µW cm−2 was obtained when ZnO nanorods are coating the carbon fiber core [Display omitted] • Radically new method to cure porous PDMS around fiber structures using localized Joule heating. • Precise control over thickness and porosity of the conformable PDMS coating over carbon fiber coated with ZnO rods. • High power triboelectric nanogenerators were achieved by controlling the thickness uniformity and porosity of the PDMS. • Mechanism for contact electrification proposed for the developed nanogenerators. • Weavable fiber based nanogenerators and its integration in proof-of-concept textiles. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the optoelectronic properties and the photodegradation of amorphous silicon films produced by the hot wire plasma assisted technique (HWPA-CVD). We observed that hydrogen dilution in the gas phase plays an important role in the time dependence of the photoconductivity, which is correlated with an enhancement of defect density. We also compare the degradation of these films with those produced by plasma enhanced and by hot wire chemical vapour deposition techniques (PECVD and HW-CVD) and we found lower time dependence for the photodegradation of the films produced by HWPA-CVD technique [Copyright &y& Elsevier]

• Cement as a material used in the historical reconstructions of the Palace of Knossos. • Identification of the types of salts and crusts by WDXRF, XRD, FTIR and μ-Raman. • Formation of gypsum crusts and thenardite efflorescence resulting from the deterioration process of the cements. • Importance of material characterisation for the conservation of monuments. The Palace of Knossos, located on the island of Crete, Greece, is one of Europe's most important archaeological sites, serving as a testament to the Minoan civilization. Situated near the Mediterranean Sea, it is in close proximity to the seaport, airport, and industrial areas. Decay products commonly found in historical monuments within or near urban areas, such as black crusts and salt efflorescence, are also prevalent at the Palace of Knossos. To better understand the characteristics of the type of deterioration compounds found on cement in historical reconstruction zones, as well as their possible relationship with factors influencing the deterioration process, a multi-analytical approach was designed for the study of these materials. The results indicate that the black crusts primarily consist of gypsum and carbonaceous matter. However, the efflorescence salts are predominantly composed of thenardite instead of halite, despite the palace's proximity to the coastal area. These results may contribute to ongoing and future maintenance and preservation efforts for the monument. [ABSTRACT FROM AUTHOR]

Abstract: Soda-lime glasses doped with Eu3+ were synthesized using a variety of compositions, namely changing the fraction of CaO or Eu2O3. Those glasses were characterized with several techniques, including ellipsometry, UV–vis–NIR absorption spectroscopy, steady-state photoluminescence spectroscopy and time-resolved luminescence. The compositions' effects on optical properties such as refraction indexes, Eu3+ oscillator strengths and luminescence lifetimes were accessed from the analysis of the experimental results. Judd–Ofelt theory was used to analyze all these aspects, which allow the detection of a mismatch of optical properties from absorption and emission spectroscopy. This mismatch was confirmed from the time-resolved data, showing the existence of two different spectroscopic Eu3+ species. From those results it is concluded that there is evidence for lanthanide aggregation, giving rise to self-quenching effects that may be described through resonance energy transfer mechanisms. The difference between luminescence lifetimes for isolated and aggregated Eu(III) is interpreted as due to different interactions with oxygen in the matrix, namely degree of covalency of the Eu–O bond and point group symmetry of the lanthanide. [Copyright &y& Elsevier]

One of the most promising approaches to produce industrial-compatible Transparent Conducting Materials (TCMs) with excellent characteristics is the fabrication of TCO/metal/TCO multilayers. In this article, we report on the electro-optical properties of a novel high-performing TCO/metal/TCO structure in which the intra-layer is a micro-structured metallic grid instead of a continuous thin film. The grid is obtained by evaporation of Ag through a mask of polystyrene colloidal micro-spheres deposited by the Langmuir-Blodgett method and partially dry-etched in plasma. IZO/Ag grid/IZO structures with different thicknesses and mesh dimensions have been fabricated, exhibiting excellent electrical characteristics (sheet resistance below 10 Ω/□) and particularly high optical transmittance in the near-infrared spectral region as compared to planar (unstructured) TCM multilayers. Numerical simulations were also used to highlight the role of the Ag mesh parameters on the electrical properties. • High-performing micro-structured Transparent Conductive Materials (TCMs) composed of IZO/Ag Mesh/IZO ultra-thin multi-layers. • Low cost, highly-scalable, easy and no thermal budget method of deposition. • High conductivity and NIR transparency of the TCMs make them attractive for bifacial and multi-terminal tandem solar cells. [ABSTRACT FROM AUTHOR]

Highlights • New method to form highly reproducible plasmonic surfaces in an fast way by RTA process. • Influence of the annealing temperature ramp-up rate on the morphology of the nanoparticles. • Formation of arrays of Ag NP via dewetting processes in just ten minutes. • Influence of the AZO spacer layers thickness on the resulting LT effects produced by the PBRs. • Best performing PBR: 120 nm Ag/100 nm AZO/6 nm Ag NPs/60 nm AZO. • μ c-Si:H solar cells show an overall 11% improvement on device efficiency. Abstract A fast method is presented to fabricate plasmonic light trapping structures in just ten minutes (>5 × faster than the present state of art), with excellent light scattering properties. The structures are composed of silver nanoparticles (Ag NPs) deposited by thermal evaporation and self-assembled using a rapid thermal annealing (RTA) system. The effect of the RTA heating rate on the NPs production reveals to be crucial to the decrease of the annealing process. The Ag NPs are integrated in thin film silicon solar cells to form a plasmonic back reflector (PBR) that causes a diffused light reflectivity in the near-infrared (600–1100 nm wavelength region). In this configuration the thicknesses of the AZO spacer/passivating layers between NPs and rear mirror, and between NPs and silicon layer, play critical roles in the near-field coupling of the reflected light towards the solar cell absorber, which is investigated in this work. The best spacer thicknesses were found to be 100 and 60 nm, respectively, for Ag NPs with preferential sizes of about 200 nm. The microcrystalline silicon (μc-Si:H) solar cells deposited on such improved PBR demonstrate an overall 11% improvement on device efficiency, corresponding to a photocurrent of 24.4 mA/cm2 and an efficiency of 6.78%, against 21.79 mA/cm2 and 6.12%, respectively, obtained on flat structures without NPs. [ABSTRACT FROM AUTHOR]

The growing interest in exploring thin film technologies to produce low cost devices such as n - i - p silicon solar cells, with outstanding performances and capability to address the highly relevant energy market, turns the optimization of their fabrication process a key area of development. The usual one-dimensional analysis of the involved parameters makes it difficult and time consuming to find the optimal set of conditions. To overcome these difficulties, the combination of experimental design and statistical analysis provides the tools to explore in a multidimensional fashion the interactions between fabrication parameters and expected experimental outputs. Design of Experiment and Multivariate Analysis are demonstrated here for the optimization of: (1) the low temperature deposition (150 °C) of high quality intrinsic amorphous silicon ( i -a-Si:H); and (2) the matching of the n -, i -, and p -silicon layers thickness to maximize the efficiency of thin film solar cells. The multiple regression method applied, validated through analysis of variance and evaluated against exact numerical simulations, is shown to predict the overall intrinsic layer properties and the devices performance. The results confirm that experimental design and statistical data analysis are effective approaches to improve, within a minimum time frame and high certainty, the properties of silicon thin films, and subsequently the layer structure of solar cells. [ABSTRACT FROM AUTHOR]

In this paper, we present the preliminary results concerning the deposition of highly transparent and conductive gallium-doped zinc oxide (GZO) deposited on transparent flexible substrate based on cellulose derivatives. Prior to the deposition of the GZO film, the surface of the polymer have been coated with a thin silicon dioxide (SiO2) layer deposited by thermal evaporation assisted by an electron gun. By doing this surface treatment, we succeeded in depositing highly conductive and transparent GZO with an electrical resistivity of 2.0×10−3 Ω cm and an average optical transmittance in the visible part of the spectrum (400–700 nm) of 70% by r.f. magnetron sputtering at room temperature. Besides the optoelectronic properties, the films are mechanically stable with a polycrystalline structure with a strong preferred (002) orientation, parallel to the substrate. [Copyright &y& Elsevier]

In this paper, we present results concerning the thickness dependence (from 70 to 890 nm) of electrical, structural, morphological and optical properties presented by gallium-doped zinc oxide (GZO) deposited on polyethylene naphthalate (PEN) substrates by r.f. magnetron sputtering at room temperature. For thicknesses higher than 300 nm an independent correlation between the electrical, morphological, structural and optical properties are observed. The lowest resistivity obtained was 5×10−4 Ω cm with a sheet resistance of 15 Ω/□ and an average optical transmittance in the visible part of the spectra of 80%. It is also shown that by passivating the surface of the polymer by depositing a thin silicon dioxide layer the electrical and structural properties of the films are improved nearly by a factor of two. [Copyright &y& Elsevier]

Gallium-doped zinc oxide films were prepared by r.f. magnetron sputtering at room temperature as a function of the substrate–target distance. The best results were obtained for a distance of 10 cm, where a resistivity as low as 2.7×10−4 Ω cm, a Hall mobility of 18 cm2/Vs and a carrier concentration of 1.3×1021 cm−3 were achieved. The films are polycrystalline presenting a strong crystallographic c-axis orientation (002) perpendicular to the substrate. The films present an overall transmittance in the visible part of the spectra of approximately 85%, on average. [Copyright &y& Elsevier]