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Findings from University of California Provide New Insights into Materials Science

February 11, 2014

By a News Reporter-Staff News Editor at Journal of Technology -- Investigators publish new report on Materials Science. According to news reporting originating from Santa Barbara, California, by VerticalNews editors, the research stated, "The status of understanding of the operation of bulk heterojunction (BHJ) solar cells is reviewed. Because the carrier photoexcitation recombination lengths are typically 10 nm in these disordered materials, the length scale for self-assembly must be of order 10-20 nm."

Our news editors obtained a quote from the research from the University of California, "Experiments have verified the existence of the BHJ nanostructure, but the morphology remains complex and a limiting factor. Three steps are required for generation of electrical power: i) absorption of photons from the sun; ii) photoinduced charge separation and the generation of mobile carriers; iii) collection of electrons and holes at opposite electrodes. The ultrafast charge transfer process arises from fundamental quantum uncertainty; mobile carriers are directly generated (electrons in the acceptor domains and holes in the donor domains) by the ultrafast charge transfer (approximate to 70%) with approximate to 30% generated by exciton diffusion to a charge separating heterojunction. Sweep-out of the mobile carriers by the internal field prior to recombination is essential for high performance. Bimolecular recombination dominates in materials where the donor and acceptor phases are pure. Impurities degrade performance by introducing Shockly-Read-Hall decay."

According to the news editors, the research concluded: "The review concludes with a summary of the problems to be solved to achieve the predicted power conversion efficiencies of >20% for a single cell."

For more information on this research see: 25th Anniversary Article: Bulk Heterojunction Solar Cells: Understanding the Mechanism of Operation. Advanced Materials, 2014;26(1):10-28. Advanced Materials can be contacted at: Wiley-V C H Verlag Gmbh, Boschstrasse 12, D-69469 Weinheim, Germany. (Wiley-Blackwell -; Advanced Materials -

The news editors report that additional information may be obtained by contacting A.J. Heeger, University of California, Center Polymers & Organ Solids, Santa Barbara, CA 93106, United States.

Keywords for this news article include: California, Santa Barbara, United States, Materials Science, North and Central America

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Source: Journal of Technology

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