Broadband Antireflection Mie Scatterers Revisited - a Solar Cell and Module Analysis

Reflectance, reduction, and light trapping enhancement are essential to maximize the absorption of silicon solar cells. The industrial state of the art method to improve the solar cell optics is wet chemical texturization of the front surface in combination with the deposition of antireflection coatings. This work analyzes an alternative route, namely a TiO2 pillar structure on the front side of a planar silicon solar cell encapsulated in ethylene vinyl acetate (EVA) and glass. It focuses on parameter variations of the structured TiO2 layer while taking the module encapsulation into account. It is shown that internal reflections at the front interface of the module play a crucial role for the structure design. This leads to optimized structures working in a different optical regime. While state of the art structures optimized for a half infinite encapsulation act as effective media, structures optimized for the full module show an improved performance by making use of diffractive effects. It could be shown that weighted reflectance of 4.7% can be reached for a solar module with TiO2 pillar structure on top of the silicon surface compared to 5.5% for a two-layer ARC with a TiO2 bottom layer and 2.3% for an isotexture, which is the state of the art structure for multicrystalline silicon cells

Nanoimprinted sol-gel materials for antireflective structures on silicon solar cells

Silicon solar cells are typically textured by means of wet chemical etching in order to enhance absorption. Within this work, we apply an optically functional layer onto a planar silicon surface. This layer is made of a high refractive index sol-gel material and can be patterned by nanoimprint lithography (NIL). In first experiments, we investigated various sol-gel based TiO2 precursors and evaluated their refractive index as well as the possibility to apply them in NIL. The refractive index was determined to be up to 2.25 using ellipsometry. This result was achieved with a solution composed of amorphous TiO2 precursors mixed with ethanol and 1,5-pentanediol. The topography of the patterned TiO2 layers were investigated using an atomic force microscope (AFM) and a scanning electron microscope (SEM) revealing a period of 1 μm and a pattern depth of 60 nm after sintering. Furthermore, optical modeling was used to optimize the structure parameters in order to minimize the weighted reflectance of an encapsulated silicon solar cell

Front Side Structures in TiO2 for Crystalline Silicon Solar Cells. Which Effects can they Achieve?

Light trapping and reflection reduction are essential, in order to enhance the absorption of silicon solar cells. State of the art in industry is texturization using wet chemical etching of the front surface in combination with the deposition of antireflection coatings to improve the solar cell optics. Within this work an alternative route, namely a TiO2 coating with nano structures on the front side of a planar silicon solar cell encapsulated in ethylene vinyl acetate (EVA) and glass, is analyzed. The focus is put on the experimental realization of such a system. Optical measurements are compared to optical simulations using the rigorous coupled wave analysis (RCWA) and the OPTOS method. Good agreement between measurements and simulation was found, so the simulation modell can be used in the future for prediction of the optical perfomance of different structures even in a PV-module

Infections in families with small children: Use of social insurance and healthcare

Objective. To examine infectious symptoms on a daily basis in families with small children and how often these infections cause people to stay at home or seek healthcare. Design. A population-based prospective study. Setting. Child health clinics in seven municipalities in Sweden. Subjects and main outcome measures. All family members of 835 families who came with an 18-month-old child to a child health clinic were asked to register all infectious symptoms in a diary for a month. They were also asked to indicate whether they had stayed at home from day-care or school, whether social insurance had been used, and whether they had contacted healthcare facilities or seen a physician. Results. In total, 7% of the 18-month-old children and 34% of the parents had no symptoms during the winter month. The most common symptom was a runny nose. The 18-month-old children had 1.6 symptom episodes with an average duration of 5.6 days. Of the symptom episodes 13% led to contact with healthcare facilities and 6% to an antibiotic prescription. Of the symptom days 27% required staying at home and in 10% social insurance was claimed. Conclusion. Symptoms of infection among families with small children were common, with a runny nose being the most common. Physician consultations and antibiotic prescriptions were used in a small proportion of the symptom episodes. Social insurance was claimed in about one-third of the days with absence from day-care