Solar ♦ news digest
provides through our vertically integrated capabilities,” says Tim Rebhorn, First Solar’s Senior Vice President of Business Development for the Americas. “We have an unmatched ability to offer industry-leading module technology, best-in-class design and construction that includes single-axis tracker and proven balance of system components.”
“We are pleased to have completed the acquisition of the Silver State South solar project,” comments NextEra Energy Resources Senior Vice President of Development Mike O’Sullivan. “This is another important milestone as we continue to build our solar business, and we look forward to working with the First Solar team to make this project a reality.”
Pre-construction activity has begun at the site, and the project is expected to be complete in late 2016. At construction peak, the project will create approximately 500 local full-time jobs.
Advancing quantum dot solar cells
ZnO/PbS quantum dot solar cells have set a new record for efficiency in devices, which could unlock new uses. The solar cell has been added to the NREL’s listing of record-high efficiencies for each kind of solar-cell technology
Solar-cell technology has advanced rapidly, as hundreds of groups around the world pursue more than two dozen approaches using different materials, technologies, and approaches to improve efficiency and reduce costs.
Now a team at MIT says it has set a new record for the most efficient quantum-dot cells - a type of solar cell that is seen as especially promising because of its inherently low cost, versatility, and light weight.
While the overall efficiency of these ZnO/PbScells is still low compared to other types - about 9 percent of the energy of sunlight is converted to electricity - the rate of improvement of this technology is claimed, by the researchers, to be one of the most rapid seen for a solar technology.
Brown.
The new process is an extension of work by Bawendi, the Lester Wolfe Professor of Chemistry, to produce quantum dots with precisely controllable characteristics - and as uniform thin coatings that can be applied to other materials. These minuscule particles are very effective at turning light into electricity, and vice versa.
Since the first progress toward the use of quantum dots to make solar cells, Bawendi says, “The community, in the last few years, has started to understand better how these cells operate, and what the limitations are.”
The new work represents a significant leap in overcoming those limitations, increasing the current flow in the cells and thus boosting their overall efficiency in converting sunlight into electricity.
Many approaches to creating low-cost, large-area flexible and lightweight solar cells suffer from serious limitations - such as short operating lifetimes when exposed to air, or the need for high temperatures and vacuum chambers during production.
By contrast, the new process does not require an inert atmosphere or high temperatures to grow the active device layers, and the resulting cells show no degradation after more than five months of storage in air.
Bulović, the Fariborz Maseeh Professor of Emerging Technology and associate dean for innovation in MIT’s School of Engineering, explains that thin coatings of quantum dots “allow them to do what they do as individuals - to absorb light very well - but also work as a group, to transport charges.” This allows those charges to be collected at the edge of the film, where they can be harnessed to provide an electric current.
The solar cell produced by the team has now been added to the National Renewable Energy Laboratories’ listing of record- high efficiencies for each kind of solar-cell technology.
The overall efficiency of the cell is still lower than for most other types of solar cells. But Bulović points out, “Silicon had six decades to get where it is today, and even silicon hasn’t reached the theoretical limit yet. You can’t hope to have an entirely new technology beat an incumbent in just four years of development.” And the new technology has important advantages, notably a manufacturing process that is far less energy-intensive than other types.
Chuang adds, “Every part of the cell, except the electrodes for now, can be deposited at room temperature, in air, out of solution. It’s really unprecedented.”
Researcher displays a sample of the record-setting new solar cell on the MIT campus (Photo courtesy of Chia-Hao Chen)
The development is described in a paper in the journal Nature Materials, by MIT professors Moungi Bawendi and Vladimir Bulović and graduate students Chia-Hao Chuang and Patrick
The system is so new that it also has potential as a tool for basic research. “There’s a lot to learn about why it is so stable. There’s a lot more to be done, to use it as a testbed for physics, to see why the results are sometimes better than we expect,” Bulović says.
A companion paper, written by three members of the same team along with MIT’s Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power Engineering, and three others, appears this month in the journal ACS Nano, explaining in greater detail the science behind the strategy
June 2014
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