Micrometer-Thin Crystalline-Silicon Solar Cells Integrating Numerically Optimized 2-D Photonic Crystals

A 2-D photonic crystal was integrated experimentally into a thin-film crystalline-silicon solar cell of 1-{\mu}m thickness, after numerical optimization maximizing light absorption in the active material. The photonic crystal boosted the short-circuit current of the cell, but it also damaged its open-circuit voltage and fill factor, which led to an overall decrease in performances. Comparisons between modeled and actual optical behaviors of the cell, and between ideal and actual morphologies, show the global robustness of the nanostructure to experimental deviations, but its particular sensitivity to the conformality of the top coatings and the spread in pattern dimensions, which should not be neglected in the optical model. As for the electrical behavior, the measured internal quantum efficiency shows the strong parasitic absorptions from the transparent conductive oxide and from the back-reflector, as well as the negative impact of the nanopattern on surface passivation. Our exemplifying case, thus, illustrates and experimentally confirms two recommendations for future integration of surface nanostructures for light trapping purposes: 1) the necessity to optimize absorption not for the total stack but for the single active material, and 2) the necessity to avoid damage to the active material by pattern etching.Comment: Authors' postprint version - Editor's pdf published online on Nov.

Absorbing photonic crystals for thin film photovoltaics

The absorption of thin hydrogenated amorphous silicon layers can be efficiently enhanced through a controlled periodic patterning. Light is trapped through coupling with photonic Bloch modes of the periodic structures, which act as an absorbing planar photonic crystal. We theoretically demonstrate this absorption enhancement through one or two dimensional patterning, and show the experimental feasibility through large area holographic patterning. Numerical simulations show over 50% absorption enhancement over the part of the solar spectrum comprised between 380 and 750nm. It is experimentally confirmed by optical measurements performed on planar photonic crystals fabricated by laser holography and reactive ion etching.Comment: 6 pages. SPIE Photonics Europe pape

Future of Management of Multiple Sclerosis in the Middle East: A Consensus View from Specialists in Ten Countries

The prevalence of multiple sclerosis (MS) is now considered to be medium-to-high in the Middle East and is rising, particularly among women. While the characteristics of the disease and the response of patients to disease-modifying therapies are generally comparable between the Middle East and other areas, significant barriers to achieving optimal care for MS exist in these developing nations. A group of physicians involved in the management of MS in ten Middle Eastern countries met to consider the future of MS care in the region, using a structured process to reach a consensus. Six key priorities were identified: early diagnosis and management of MS, the provision of multidisciplinary MS centres, patient engagement and better communication with stakeholders, regulatory body education and reimbursement, a commitment to research, and more therapy options with better benefit-to-risk ratios. The experts distilled these priorities into a single vision statement: “Optimization of patient-centred multidisciplinary strategies to improve the quality of life of people with MS.” These core principles will contribute to the development of a broader consensus on the future of care for MS in the Middle East

Characteristics of multiple sclerosis in the Middle East with special reference to the applicability of international guidelines to the region

We have reviewed the clinical literature with reference to the local applicability of guidelines for the diagnosis and management of multiple sclerosis (MS) in the Middle East. There is a substantial burden of MS in the region: the prevalence of the disease appears to have increased markedly in recent decades, with a faster rate of increase in female vs. male patients. The aetiology and presentation of MS appears to be broadly similar in the Middle East to that in other regions. Interferon-β is the most commonly used treatment for MS in the Middle East, as elsewhere, although it is unclear to what extent economic constraints act as a barrier to accessing this treatment. Similarly, limited available data suggest that the availability of MRI scanners appears to be lower in the Middle East than in more developed nations. Little is known concerning other potential barriers to treatment. There is a need for further research on aspects of management of MS beyond the pharmacological aspects of treatment to assess fully the potential barriers to the adoption of international guidelines for the diagnosis and management of the disease in the Middle East. © 2014 Informa Healthcare USA, Inc