GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates

In this study, we report synthesis of large area (> 2 cm^2) crack-free GaInP/GaAs double junction solar cells on 50 mm diameter Ge/Si templates fabricated using wafer bonding and ion implantation induced layer transfer techniques. Defect removal from the template film and film surface prior to epitaxial growth was found to be critical to achievement of high open circuit voltage and efficiency. Cells grown on templates prepared with chemical mechanical polishing in addition a wet chemical etch show comparable performance to control devices grown on bulk Ge substrates. Current-voltage (I–V) data under AM 1.5 illumination indicate that the short circuit current is comparable in templated and control cells, but the open circuit voltage is slightly lower (2.08V vs. 2.16V). Spectral response measurements indicate a drop in open circuit voltage due to a slight lowering of the top GaInP cell band gap. The drop in band gap is due to a difference in the indium composition in the two samples caused by the different miscut (9° vs. 6°) of the two kinds of substrates

GaInP/GaAs dual junction solar cells on Ge/Si epitaxial templates

Large area, crack-free GaInP/GaAs double junction solar cells were grown by metal organic chemical vapor deposition on Ge/Si templates fabricated using wafer bonding and ion implantation induced layer transfer. Photovoltaic performance of these devices was comparable to those grown on bulk epi-ready Ge, demonstrating the feasibility of alternative substrates fabricated via wafer bonding and layer transfer for growth of active devices on lattice mismatched substrates

Metamorphic concentrator solar cells with over 40% conversion efficiency

ABSTRACT: Multijunction III-V concentrator cells have attracted much interest for concentrator photovoltaic (PV) systems recently due to their unparalleled conversion efficiencies. As high as these efficiencies are, they can be made even higher if the combination of subcell bandgaps for the multijunction solar cell are chosen from metamorphic semiconductors that are not all lattice-matched to the same growth substrate. Advances in the design of metamorphic subcells to reduce carrier recombination and increase voltage, wide-bandgap tunnel junctions capable of operating at high concentration, metamorphic buffers to transition from the substrate lattice constant to the active subcells, concentrator cell AR coating and grid design, and integration into 3-junction cells current matched under the terrestrial spectrum have resulted in new heights in solar cell performance. A metamorphic Ga 0.44 In 0.56 P/ Ga 0.92 In 0.08 As/ Ge 3-junction solar cell from this research has reached a record 40.7% efficiency at 240 suns, under the standard reporting spectrum for terrestrial concentrator cells (AM1.5 direct, low-AOD, 24.0 W/cm 2 25°C), and experimental lattice-matched 3-junction cells have now also achieved over 40% efficiency, with 40.1% measured at 135 suns. This metamorphic 3-junction device is the first solar cell to reach over 40% in efficiency, and has the highest solar conversion efficiency for any type of photovoltaic cell developed to date

LI-RADS: A Conceptual and Historical Review from Its Beginning to Its Recent Integration into AASLD Clinical Practice Guidance

The Liver Imaging Reporting and Data System (LI-RADS®) is a comprehensive system for standardizing the terminology, technique, interpretation, reporting, and data collection of liver observations in individuals at high risk for hepatocellular carcinoma (HCC). LI-RADS is supported and endorsed by the American College of Radiology (ACR). Upon its initial release in 2011, LI-RADS applied only to liver observations identified at CT or MRI. It has since been refined and expanded over multiple updates to now also address ultrasound-based surveillance, contrast-enhanced ultrasound for HCC diagnosis, and CT/MRI for assessing treatment response after locoregional therapy. The LI-RADS 2018 version was integrated into the HCC diagnosis, staging, and management practice guidance of the American Association for the Study of Liver Diseases (AASLD). This article reviews the major LI-RADS updates since its 2011 inception and provides an overview of the currently published LI-RADS algorithms

Mosque-based emotional support among young Muslim Americans

Despite a growing literature on social support networks in religious settings (i.e., church-based social support), little is known about mosque-based support among Muslims. This study investigates the demographic and religious behavior correlates of mosque-based social support among a multi-racial and ethnic sample of 231 young Muslims from southeast Michigan. Several dimensions of mosque-based support are examined including receiving emotional support, giving emotional support, anticipated emotional support and negative interactions with members of one’s mosque. Results indicated that women both received and antic- ipated receiving greater support than did men. Higher educational attainment was associated with receiving and giving less support compared to those with the lowest level of educational attainment. Moreover, highly educated members reported fewer negative interactions than less educated members. Mosque attendance and level of congregational involvement positively predicted receiving, giving, and anticipated emotional support from congregants, but was unrelated to negative interactions. Overall, the study results converge with previously established correlates of church- based emotional support.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107410/1/art%3A10.1007%2Fs13644-013-0119-0(1).pd

Cross-Sectional Transport Imaging in a Multijunction Solar Cell

IEEE Journal of PhotovoltaicsThe article of record as published may be found at http://dx.doi.org/10.1109/jphotov.2016.2623088We combine a highly localized electron-beam point source excitation to generate excess free carriers with the spatial resolution of optical near-field imaging to map recombination in a cross-sectioned multijunction (Ga0.5In0.5P/GaIn0.01As/Ge) solar cell. By mapping the spatial variations in emission of light for fixed generation (as opposed to traditional cathodoluminescence (CL), which maps integrated emission as a function of position of generation), it is possible to directly monitor the motion of carri- ers and photons. We observe carrier diffusion throughout the full width of the middle (GaInAs) cell, as well as luminescent coupling from point source excitation in the top cell GaInP to the middle cell. Supporting CL and near-field photoluminescence (PL) measure- ments demonstrate the excitation-dependent Fermi level splitting effects that influence cross-sectioned spectroscopy results, as well as transport limitations on the spatial resolution of conventional cross-sectional far-field measurements.Funded by Naval Postgraduate SchoolFulbright Senior Scholar AwardNational Renewable Energy LaboratoryNational Science FoundationLaboratory and Directed Research and Development progra

Advances in High-Efficiency III-V Multijunction Solar Cells

The high efficiency of multijunction concentrator cells has the potential to revolutionize the cost structure of photovoltaic electricity generation. Advances in the design of metamorphic subcells to reduce carrier recombination and increase voltage, wide-band-gap tunnel junctions capable of operating at high concentration, metamorphic buffers to transition from the substrate lattice constant to that of the epitaxial subcells, concentrator cell AR coating and grid design, and integration into 3-junction cells with current-matched subcells under the terrestrial spectrum have resulted in new heights in solar cell performance. A metamorphic Ga0.44In0.56P/Ga0.92In0.08As/ Ge 3-junction solar cell from this research has reached a record 40.7% efficiency at 240 suns, under the standard reporting spectrum for terrestrial concentrator cells (AM1.5 direct, low-AOD, 24.0 W/cm2, 25∘C), and experimental lattice-matched 3-junction cells have now also achieved over 40% efficiency, with 40.1% measured at 135 suns. This metamorphic 3-junction device is the first solar cell to reach over 40% in efficiency, and has the highest solar conversion efficiency for any type of photovoltaic cell developed to date. Solar cells with more junctions offer the potential for still higher efficiencies to be reached. Four-junction cells limited by radiative recombination can reach over 58% in principle, and practical 4-junction cell efficiencies over 46% are possible with the right combination of band gaps, taking into account series resistance and gridline shadowing. Many of the optimum band gaps for maximum energy conversion can be accessed with metamorphic semiconductor materials. The lower current in cells with 4 or more junctions, resulting in lower I2R resistive power loss, is a particularly significant advantage in concentrator PV systems. Prototype 4-junction terrestrial concentrator cells have been grown by metal-organic vapor-phase epitaxy, with preliminary measured efficiency of 35.7% under the AM1.5 direct terrestrial solar spectrum at 256 suns