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news digest ♦ Solar current across molecules.


In some cases they designed the material, an array of gold nanoparticles, using a technique Bonnell’s group invented, known as ferroelectric nanolithography.


The discovery was potentially powerful, but the scientists couldn’t prove that the improved transduction of optical radiation to an electrical current was due to the “hot electrons” produced by the excited plasmons. Other possibilities included that the porphyin molecule itself was excited or that the electric field could focus the incoming light.


“We hypothesised that, when plasmons are excited to a high energy state, we should be able to harvest the electrons out of the material,” Bonnell explains. “If we could do that, we could use them for molecular electronics device applications, such as circuit components or solar energy extraction.”


To examine the mechanism of the plasmon-induced current, the researchers systematically varied the different components of the plasmonic nanostructure, changing the size of the gold nanoparticles, the size of the porphyin molecules and the spacing of those components. They designed specific structures that ruled out the other possibilities so that the only contribution to enhanced photocurrent could be from the hot electrons harvested from the plasmons.


“In our measurements, compared to conventional photoexcitation, we saw increases of three to 10 times in the efficiency of our process,” Bonnell comments. “And we didn’t even optimise the system. In principle you can envision huge increases in efficiency.”


Devices incorporating this process of harvesting plasmon-induced hot electrons could be customized for different applications by changing the size and spacing of nanoparticles, which would alter the wavelength of light to which the plasmon responds.


“You could imagine having a paint on your laptop that acted like a solar cell to power it using only sunlight,” Bonnell says. “These materials could also improve communications devices, becoming part of efficient molecular circuits.”


This work is described further in the paper, «Plasmon- Induced Electrical Conduction in Molecular Devices,» by Parag Banerjee et al in ACS Nano, 2010, 4 (2), pp 1019 - 1025. DOI: 10.1021/nn901148m


The research was supported by the U.S. Department of Energy and the National Science Foundation.


CdTe innovator First Solar and Belectric form joint venture


The solar industry innovators have launched a JV to fulfil projects in Europe, North Africa and US


First Solar and Belectric Holding, GmbH have announced the launch of a Joint Venture (JV) that will realise solar energy projects on three continents.


The JV - PV Projects GmbH & Co. KG - is based in Germany and will be tasked with developing selected photovoltaic (PV) power projects independently acquired or developed by either of the two companies in Europe, North Africa, as well as projects of fewer than 20 megawatts (MW), in the United States.


Under the terms of the JV - which is subject to approval from the relevant governmental merger control authorities - First Solar will supply its advanced cadmium telluride thin-film modules, selected components such as the First Solar Tracker and value-added services; while Belectric will provide its advanced Balance of Systems (BoS) and a range of service capabilities.


Both companies’ engineering, procurement and construction (EPC) contributions will vary by project and geography. The JV’s emphasis on the sub-20MW segment in the United States will include Belectric’s existing 280MWp pipeline in the country, along with other opportunities. The non-exclusive agreement will also allow both companies to independently and competitively pursue development prospects and corresponding EPC work.


The announcement is the latest milestone in a longstanding partnership that spans over a decade: the two companies recently marked the inauguration of the 128MWp Templin solar power plant in Germany, the largest deployment of First Solar modules in Europe. An estimated 80 percent of the 1,400 MWp of solar electricity generation capacity installed by Belectric, is powered by First Solar modules.


“With its industry-leading capabilities, this joint venture will ensure that our individual project obligations are delivered to the highest standards,” says Jim Hughes, First Solar’s Chief Executive Officer. “First Solar and Belectric share a long history of excellence and we are confident about the future of this initiative, which is based on a firm foundation of mutual trust, expertise and a track record that is unrivalled in the solar energy industry.”


“We are happy to celebrate this important new milestone in our long-term partnership with First Solar,” comments


106 www.compoundsemiconductor.net October 2013


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