Light-Management Strategies for Thin-Film Silicon Multijunction Solar Cells

Light management is of crucial importance to reach high efficiencies with thin-film silicon multijunction solar cells. In this contribution, we present light-management strategies that we recently developed. This includes high quality absorber materials, low-refractive index intermediate reflectors, and highly transparent multiscale electrodes. Specifically, we show the fabrication of high-efficiency tandem devices with a certified stabilized efficiency of 12.6%, triple-junction solar cells with a stabilized efficiency of 12.8%, recently developed smoothening intermediate reflector layers based on silicon dioxide nanoparticles, and periodic-on-random multiscale textures

Controlling Mesopore Size and Processability of Transparent Enzyme-Loaded Silica Films for Biosensing Applications

Silica-based nanoporous thin films including large mesopores are relevant as enzyme supports for applications in biosensing. The diffusion and immobilization of large biomolecules such as enzymes in such porous films require the presence of large mesopores. Creating such morphologies based on a bottom-up synthesis using colloidal templates is a challenge in view of the combination of desired material properties and the robustness of the casting process for the fabrication of thin films. Here a strategy to reproducibly synthesize transparent porous silica thin films with submicrometer thickness and homogeneously distributed porosity is presented. For this purpose, polystyrene-poly-2-vinylpyridine (PS-P2VP) amphiphilic block copolymers are used as porogenic templates. Low-chain alcohols are employed as both selective solvents for the P2VP blocks and reaction media for silica synthesis. Rheology measurements reveal a strong influence of the block copolymer length on the behavior of PS-P2VP micelles in suspension. The pore distribution and accessibility into the film are controlled by adjusting the silica to block copolymer weight ratio. The solvent choice is shown to control not only the micelle size and the generated pore morphology but also the structural homogeneity of the films. Finally, the suitability of the synthesized films as supports for enzymes is tested using a model enzyme, horseradish peroxidase EC 1.11.1.7. Our approach is innovative, robust, and reproducible and provides a convenient alternative to synthesize large mesopores up to small macropores (20100 nm) in nanostructured thin films with applications in biosensing and functional coatings

Transparent and Robust Silica Coatings with Dual Range Porosity for Enzyme-Based Optical Biosensing

Hierarchically porous transparent silica coatings combine large specific surface area with enhanced pore accessibility for optical biosensing. This paper describes a versatile approach to fabricate optically transparent silica coatings with multiscale porosity. Thin films (around 1 mu m in thickness) of an aqueous suspension of primary silica aggregates form a mesoporous, interconnected matrix, and sacrificial polymer particles template well-defined, discrete macropores with high structural integrity. The total surface area achieved is around 200 m(2) g(-1) with mesopore sizes of 20-40 nm and macropores of 250 nm, with a total porosity of 84%. The macro/meso dual range of porosity allows enhanced biocatalyst loadings of l-lactate dehydrogenase for detection of lactate. The functionalized films showed a linear response within the range of interest of 1-20 x 10(-3) m of lactate. These biosensing coatings therefore strongly enhance sensitivity, speed and reliability of optically based lactate detection as compared to classical thin films with monomodal mesopore structure. Particle-based simulations and experiments reveal that both the location and connectivity of the macropores control the biosensing performance. The coatings and procedure presented here are versatile, scalable, inexpensive, and are therefore compatible with a wide range of deposition techniques suitable for industrial and health care applications

Flow-induced vibrations of in-line cylinder arrangements at low Reynolds numbers

International audienceThe present study numerically explores the limiting two degrees of freedom (streamwise and transverse) free oscillation response of three circular cylinders, placed in an in-line configuration subjected to a uniform cross flow at low Reynolds numbers. Three identical cylinders with a low mass ratio (m⁎=4/πm⁎=4/π) and zero damping are considered. The spacing between the cylinders L/DL/D is equal to 4. The reduced velocity Ur is varied from 2 to 13 for two values of the Reynolds number (Re=100Re=100 and Re=150Re=150). For comparison purposes, the free oscillation responses of an isolated cylinder and a tandem cylinder pair under the same conditions are also evaluated. The results show that the dynamic behaviors of three in-line cylinders are significantly different from those of the tandem cylinder pair. While the maximum transverse oscillation amplitude increases by about 25%, there is now a very large streamwise oscillation amplitude (AX/D≈1.3AX/D≈1.3), comparable to those in the transverse direction. They appear at Ur>9Ur>9. The frequency responses of the triple cylinder case are much richer; in particular, at higher Ur. There is a clear low frequency component which is most evident in the streamwise direction. Many of the displacement trajectories of the triple cylinder case can almost be described as “bounded random movements”. The associated phase portraits and the Poincaré maps show that the dynamical characteristics of the triple cylinder configuration are considerably richer than those of the tandem cylinder pair. Even at such low Re, the free oscillations of three in-line cylinders already seem to approach a chaotic response. In particular, there is evidence that the fluid–structure system approaches to chaos via the quasi-periodic route. Due to such much more complex dynamical characteristics, it is therefore highly risky to predict the free oscillation behaviors of multiple in-line cylinders by extrapolating those of the tandem cylinder pair

Self-Patterned Nanoparticle Layers for Vertical Interconnects: Application in Tandem Solar Cells

We demonstrate self-patterned insulating nanoparticle layers to define local electrical interconnects in thin-film electronic devices. We show this with thin-film silicon tandem solar cells, where we introduce between the two component cells a solution-processed SiO2 nanoparticle layer with local openings to allow for charge transport. Because of its low refractive index, high transparency, and smooth surface, the SiO2 nanoparticle layer acts as an excellent intermediate reflector allowing for efficient light management

Self-Patterned Nanoparticle Layers for Vertical Interconnects: Application in Tandem Solar Cells

We demonstrate self-patterned insulating nanoparticle layers to define local electrical interconnects in thin-film electronic devices. We show this with thin-film silicon tandem solar cells, where we introduce between the two component cells a solution-processed SiO₂ nanoparticle layer with local openings to allow for charge transport. Because of its low refractive index, high transparency, and smooth surface, the SiO₂ nanoparticle layer acts as an excellent intermediate reflector allowing for efficient light management