Quantum Dot-Based Thin-Film III–V Solar Cells

In this work, we report our recent results in the development of thin-film III–V solar cells fabricated by epitaxial lift-off (ELO) combining quantum dots (QD) and light management structures. Possible paths to overcome two of the most relevant issues posed by quantum dot solar cells (QDSC), namely, the degradation of open circuit voltage and the weak photon harvesting by QDs, are evaluated both theoretically and experimentally. High open circuit voltage QDSCs grown by molecular beam epitaxy are demonstrated, both in wafer-based and ELO thin-film configuration. This paves the way to the implementation in the genuine thin-film structure of advanced photon management approaches to enhance the QD photocurrent and to further optimize the photovoltage. We show that the use of light trapping is essential to attain high-efficiency QDSCs. Based on transport and rigorous electromagnetic simulations, we derive design guidelines towards light-trapping enhanced thin-film QDSCs with efficiency higher than 28% under unconcentrated light, ambient temperature. If photon recycling can be fully exploited, 30% efficiency is deemed to be feasible. Towards this goal, results on the development and integration of optimized planar and micro-patterned mirrors, diffractive gratings and broadband antireflection coatings are presented.acceptedVersionPeer reviewe

miR-16 and miR-21 Expression in the Placenta Is Associated with Fetal Growth

BACKGROUND: Novel research has suggested that altered miRNA expression in the placenta is associated with adverse pregnancy outcomes and with potentially harmful xenobiotic exposures. We hypothesized that aberrant expression of miRNA in the placenta is associated with fetal growth, a measurable phenotype resulting from a number of intrauterine factors, and one which is significantly predictive of later life outcomes. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed 107 primary, term, human placentas for expression of 6 miRNA reported to be expressed in the placenta and to regulate cell growth and development pathways: miR-16, miR-21, miR-93, miR-135b, miR-146a, and miR-182. The expression of miR-16 and miR-21 was markedly reduced in infants with the lowest birthweights (p<0.05). Logistic regression models suggested that low expression of miR-16 in the placenta predicts an over 4-fold increased odds of small for gestational age (SGA) status (p = 0.009, 95% CI = 1.42, 12.05). Moreover, having both low miR-16 and low miR-21 expression in the placenta predicts a greater increase in odds for SGA than having just low miR-16 or miR-21 expression (p<0.02), suggesting an additive effect of both of these miRNA. CONCLUSIONS/SIGNIFICANCE: Our study is one of the first to investigate placental miRNA expression profiles associated with birthweight and SGA status. Future research on miRNA whose expression is associated with in utero exposures and markers of fetal growth is essential for better understanding the epigenetic mechanisms underlying the developmental origins of health and disease

Light-trapping enhanced thin-film III-V quantum dot solar cells fabricated by epitaxial lift-off

Contains fulltext : 191873.pdf (preprint version ) (Open Access

Novel Concepts for High-Efficiency Lightweight Space Solar Cells

One of the key issues in the design and development of a satellite Photovoltaic Assembly (PVA) is the trade-off to be made between the available volume located to the PVA, its mass and the total amount of power that the solar panels have to guarantee to the spacecraft. The development of high-efficiency, flexible, lightweight solar cells is therefore instrumental to the design of future satellites providing enhanced missions and services. Based on the consolidated development of GaAs-based single junction and lattice matched triple-junction solar cells, several research efforts are being pursued worldwide to further increase the efficiency and reduce mass. Promising approaches include thin-film technologies such as Inverted Metamorphic and Epitaxial Lift-Off (ELO), and the use of nanostructures or highly mismatched alloys grown by MBE. We propose here an alternative path towards the development of lightweight GaAs-based solar cells with the potential to exceed the Shockley-Queisser (SQ) limit of single junction cells. Our approach is based on the synergistic combination of thin-film design, quantum dots (QDs) absorption, and photonic nanostructures. Challenges and opportunities offered by the use of QDs are discussed. A cost-effective and scalable fabrication process including ELO technology and nanoimprint lithography is outlined. Finally, a proof-of-concept design, based on rigorous electromagnetic and physics-based simulations, is presented. Efficiency higher than 30% and weight reduction close to 90% - owing to the substrate removal - makes the proposed device to rank record power-to-weight ratio, with the potential to become a cost-effective, attractive option for next generation space solar cells

Enhanced Probe-Based RT-qPCR Quantification of MicroRNAs Using Poly(A) Tailing and 5′ Adaptor Ligation

International audienceProbe-based quantitative PCR (qPCR) is a commonly used tool in the realm of real-time qPCR experiments since it is one of the most sensitive detection methods allowing an accurate and reproducible analysis. It uses real-time fluorescence from a fluorescently labeled probe that specifically targets the desired PCR product to measure DNA amplification at each cycle of the PCR. Coupled to a proper reverse transcription step, probe-based qPCR can be efficiently used for the analysis of the expression of difficult targets such as miRNAs. In this chapter, we describe the TaqMan® advanced miRNA assay in which, owing to a poly(A)-tailing step, the reverse transcription is advantageously performed at once for all the miRNAs in a given sample, and, coupled to the ligation of a 5' universal adapter, allows for a supplementary pre-qPCR amplification step increasing the sensitivity of the assay. Along this protocol, we also provide our general guidelines and advices to perform a reliable and successful quantitative analysis