The Channel girder is a cost-effective solution for short to medium span structures. The top deck can be manufactured with a variety of traction profiles, eliminating the need for field applied wearing surfaces. Standard Channel Beam sizes are listed below in 20", 24", 28", 32" and 36" depths, but custom sizes and adaptations such as extended flanges or 2nd cast curbs are easily attainable. While the Channel Beam section was originally developed for bridges, it is also popular for marine pier, building and garage applications.
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Delocalization and Dielectric Shedding of Charge Transfer States in Organic Photovoltaic Cells
Researchers from the University of Pennsylvania have made a breakthrough in understanding the fundamental science behind charge separation, paving the way for more affordable organic solar cells. Their findings could lead to improved designs and manufacturing processes for highly efficient solar panels. The study was recently published in *Nature Communications*, offering new insights into how these devices work at the molecular level.
Currently, the highest efficiency of lab-scale organic solar cells is around 10%, which is significantly lower than that of inorganic silicon-based solar cells. One major challenge in improving this efficiency lies in the separation of electron-hole pairs—also known as excitons. These pairs must be separated to generate electricity, but achieving this efficiently has proven difficult.
Traditionally, scientists have used a heterojunction structure, where two different organic semiconductors are placed next to each other. This setup allows one material to donate an electron while the other accepts it, breaking apart the excitons. However, a long-standing issue has been how to fully separate the charges to maximize current output, which limits the overall efficiency of most solar cells.
In recent years, a new theory has emerged suggesting that quantum effects play a key role in this process. According to this idea, electrons and holes can exist in a wave-like state across several nearby molecules, making it easier for them to separate. Researchers at Penn have now provided strong evidence supporting this concept, showing that nanocrystals—specifically C60 fullerenes, also known as buckyballs—are essential in enabling this delocalization effect.
This discovery is crucial for the effective generation of photocurrent in organic solar cells. Previously, it was believed that a large energy difference between donor and acceptor materials was necessary to split excitons, which often reduced the voltage of the cell. The new research shows that by leveraging the delocalization and local crystallinity of the wave function, this energy offset can be eliminated. This advancement opens the door for designing better molecules and optimizing the structure of donor and acceptor materials, ultimately increasing the voltage and efficiency of solar cells.
To arrive at their conclusions, the team used advanced techniques such as photoluminescence and electro-absorption spectroscopy, along with X-ray diffraction. Their findings are helping other researchers gain a deeper understanding of charge separation mechanisms, which will be vital in developing more efficient and cost-effective organic solar technologies in the future.