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Highly transparent Ho:Y2O3 ceramics for laser diode lighting were prepared using the vacuum sintering method with 0.3 at.% Nb2O5 as a sintering additive. The microstructures, transmittance, and luminescence properties of the Ho:Y2O3 ceramic samples were investigated in detail. The transmittance levels of all samples with various Ho3+ concentrations reached ~81.5% (2 mm thick) at 1100 nm. Under the excitation of 363 nm (ultraviolet) or 448 nm (blue) light, Ho:Y2O3 transparent ceramic samples showed that green emission peaked at 550 nm. The emission intensity was strongly affected by the concentration of Ho3+ ions, reaching its highest level in the sample doped with 1 at.% Ho3+. The CIE coordinates of the luminescence were in the green region (i.e., the CIE coordinates of the sample doped with 1 at.% Ho3+ were [0.27, 0.53] and [0.30, 0.69], under the excitation of 363 nm and 448 nm light, respectively). The possibility of its application as laser diode lighting was reported. Under the excitation of 450 nm blue laser, the sample doped with 0.5 at.% Ho3+ had the best performance: the saturated luminous flux, lumen efficiency, and the luminescence saturation power densities were 800 lm, 57.7 lm/W, and 17.6 W/mm2, respectively. Furthermore, the materials have high thermal conductivity and mechanical strength due to their host of rare-earth sesquioxide. Thus, Ho:Y2O3 transparent ceramics are expected to be a promising candidate for green-light-emitting devices for solid-state lighting, such as laser diode lighting. [ABSTRACT FROM AUTHOR]

Constructing a solar-powered photothermal system that can self-regulate temperature without requiring extra energy input is significant for energy saving, but how to achieve zero-energy building remains challenging. Here, a photothermal system that integrates sunlight harvesting, photothermal conversion (PTC), and heat storage was constructed. Well-developed nanoscale pore silica aerogels with high transparency (visible-light transmittance 69.3%, near-infrared transmittance 86.9%), bending resistance (bending angle >30°), and low thermal conductivity were prepared by the interpenetration of C and Si molecular networks using vinyltrimethoxysilane as the silica source, which was used as a window material for the temperature self-regulating system to block heat loss and allow sunlight transmission. Simultaneously, the prepared CsxWO3 (CWO) film with PTC could convert sunlight into heat. Also, PEG 2000 is introduced into the system with a suitable phase transition temperature to further realize temperature self-regulation within a certain range. The outdoor simulation test results showed that the system could heat water to 69.8 °C using sunlight in cold weather around 0 °C, which was 67.6 °C higher than the ambient temperature and can stay above 18 °C for about 20 h, and even in cloudy weather, it could reach 58.2 °C. The highly transparent silica aerogel is given the ability to resist bending, which opens up more application prospects for silica aerogels, and the constructed self-regulating temperature system without additional energy input contributes to the development of the zero-energy building. [ABSTRACT FROM AUTHOR]

Highly transparent Er:Y2O3 ceramics (1–9 at.% Er) were fabricated by hot pressing sintering with ZrO2 as the sintering additive. The microstructures, transmittance, luminescent properties, thermal conductivity, and mechanical properties of the Er:Y2O3 ceramic samples were investigated in detail. The samples all exhibited dense and fine grain microstructures; the average grain sizes were about 0.8 μm. The transmittance levels of the samples with various Er concentrations (2 mm thick) at the wavelengths of 600 and 2700 nm were ~74 and ~83%, respectively. As the Er doping concentration increased from 1 to 9 at.%, the up-conversion luminescence of the samples gradually changed from green to red, with the intensity ratio of red/green light increasing from 0.28 to 2.01. Meanwhile, the down-conversion luminescence properties of the specimens were also studied. When the samples were under 980 nm excitation, the emission bands were detected at 1552, 1573, 1639, and 1661 nm. The thermal conductivity of the samples was found to decrease from 8.72 to 5.81 W/(m·K) with an increase of the Er concentration from 1 to 9 at.%. Moreover, the microhardness and fracture toughness of the samples with 1 at.% Er concentration were ~8.51 GPa and ~1.03 MPa·m1/2, respectively. [ABSTRACT FROM AUTHOR]

Chitin and gelatin are biodegradable and biocompatible polymers which have gained much attention applied as bio-based materials. In this study, Chitin nanofiber (ChNF)/gelatin nanocomposite was synthesized by immersion method followed with drying at room temperature. The ChNF content in the ChNF/gelatin was controlled in a broad range by changing the concentration of gelatin solutions from 2, 5 to 10% during the immersion processes. The prepared ChNF/gelatin showed uniformly nanofiber network structures which embedded inside the gelatin matrix. The UV measurement indicated that the transmittance of ChNF was increased to as high as 88.7% from 65% at 600 nm, regardless of nanofiber content. Young’s modulus of the 50.2%-ChNF/gelatin (with the ChNF content of 50.2%) was around 5192 MPa, which was almost two times higher than that of the pure gelatin. This mechanical improvement was attributed to the reinforcing effect from ChNF nano-networks as well as the formation of hydrogen bondings between gelatin and chitin moleculars. Therefore, with the highly transparent and improved mechanical properties, the prepared ChNF/gelatin nanocomposite films may offer promising and broad prospects in the field of food packaging and bio-medical industrials. [ABSTRACT FROM AUTHOR]

In order to prepare novel polyimides (PI) with high transparency and solubility in common solvents, three diamine monomers containing pyridine or methyl-substituted pyridine and cyclohexane, 1,1'-bis[4-(5-amino-2-pyridinoxy) phenyl]cyclohexane (IIIa), 1,1'-bis[4-(5-amino-3-methyl-2-pyridinoxy)phenyl]cyclohexane (IIIb), and 1,1'-bis[4-(5-amino2-methyl-6-pyridinoxy)phenyl]cyclohexane (IIIc), were synthesized and characterized. The diamine monomer (IIIa) was subsequently polymerized with 3,3',4,4'-oxydiphthalic anhydride, 4,4'-(hexafluoroisopropylidene)-diphthalic anhydride (6FDA) to obtain PIs, PI-1 and PI-2. Furthermore, PI-3 (IIIb/6FDA) and PI-4 (IIIc/6FDA) were prepared for structure -- property comparison studies. The structures of the resulting PIs were characterized by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction, and elemental analysis. The physical properties of the PI films were investigated by thermogravimetric analysis, differential scanning calorimetric analysis, dynamic mechanical analysis, and ultraviolet -- visible spectroscopy. In general, the PIs showed excellent thermal properties and good mechanical properties. Most had good solubility in polar organic solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone (NMP), m-cresol, and even soluble in low boiling solvents such as tetrahydrofuran (THF) and CHCl3. The PI films also exhibited high optical transmittance of 94-97% at 500 nm and cut-off wavelength at 345-359 nm. In summary, the introduction of methyl, cyclohexane, and pyridine groups into the backbone was shown to improve the solubility and transparency of PI films. [ABSTRACT FROM AUTHOR]

The scalable synthesis of highly transparent and robust sub-monolayers of Co3O4 nano-islands, which efficiently catalyze water oxidation, is reported. Rapid aerosol deposition of Co3O4 nanoparticles and thermally induced self-organization lead to an ultra-fine nano-island morphology with more than 94% light transmission at a wavelength of 500 nm. These transparent sub-monolayers demonstrate a remarkable mass-weighted water oxidation activity of 2070-2350 A gCo3O4−1 and per-metal turnover frequency of 0.38-0.62 s−1 at an overpotential of 400 mV in 1 m NaOH aqueous solution. This mixed valent cobalt oxide structure exhibits excellent long-term electrochemical and mechanical stability preserving the initial catalytic activity over more than 12 h of constant current electrolysis and 1000 consecutive voltammetric cycles. The potential of the Co3O4 nano-islands for photoelectrochemical water splitting has been demonstrated by incorporation of co-catalysts in GaN nanowire photoanodes. The Co3O4-GaN photoanodes reveal significantly reduced onset overpotentials, improved photoresponse and photostability compared to the bare GaN ones. These findings provide a highly performing catalyst structure and a scalable synthesis method for the engineering of efficient photoanodes for integrated solar water-splitting cells. [ABSTRACT FROM AUTHOR]

To further increase the efficiency of multijunction thin-film silicon (TF-Si) solar cells, it is crucial for the front electrode to have a good transparency and conduction, to provide efficient light trapping for each subcell, and to ensure a suitable morphology for the growth of high-quality silicon layers. Here, we present the implementation of highly transparent modulated surface textured (MST) front electrodes as light-trapping structures in multijunction TF-Si solar cells. The MST substrates comprise a micro-textured glass, a thin layer of hydrogenated indium oxide (IOH), and a sub-micron nano-textured ZnO layer grown by low-pressure chemical vapor deposition (LPCVD ZnO). The bilayer IOH/LPCVD ZnO stack guarantees efficient light in-coupling and light trapping for the top amorphous silicon (a-Si:H) solar cell while minimizing the parasitic absorption losses. The crater-shaped micro-textured glass provides both efficient light trapping in the red and infrared wavelength range and a suitable morphology for the growth of high-quality nanocrystalline silicon (nc-Si:H) layers. Thanks to the efficient light trapping for the individual subcells and suitable morphology for the growth of high-quality silicon layers, multijunction solar cells deposited on MST substrates have a higher efficiency than those on single-textured state-of-the-art LPCVD ZnO substrates. Efficiencies of 14.8% (initial) and 12.5% (stable) have been achieved for a-Si:H/nc-Si:H tandem solar cells with the MST front electrode, surpassing efficiencies obtained on state-of-the-art LPCVD ZnO, thereby highlighting the high potential of MST front electrodes for high-efficiency multijunction solar cells. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

High-quality SnO2:Si films and SnO2:10 at.% Ga films were prepared by the solution method. The roughness of films is below 1.08 nm, and possess exceptional transparency (>75%) and decent semiconductor properties. Based on this, the SnO2:Si/SnO2: Ga homojunctions with different Si doping concentrations were prepared. It is found that the conductivity of the SnO2:Si thin film gradually increases, and the rectification characteristics of the homojunction are optimized with increasing Si doping content. The SnO2:15 at.% Si/SnO2:10 at.% Ga homogeneous junction has the best performance, the turn-on voltage is as low as 5.6 V, and it also exhibits good unidirectional conductivity. The photoresponse of the SnO2:15 at.% Si/SnO2:10 at.% Ga homojunction under the lights of red, yellow, and purple was explored respectively. The result shows that the device responds strongly to purple light. Compared with the test results in the dark environment, the device current increases by two orders, which is expected to be applied in the field of near-ultraviolet detection. [ABSTRACT FROM AUTHOR]