The University of Cambridge team have harvested the energy of triplet excitons, an excited electron state whose energy in harvested in solar cells, and transferred it from organic to inorganic semiconductors. In the natural world, excitons are a key part of photosynthesis: light photons are absorbed by pigments and generate excitons, which then carry the associated energy throughout the plant. In conventional semiconductors such as silicon, when one photon is absorbed it leads to the formation of one free electron that can be extracted as current.
Using state-of-art femtosecond laser spectroscopy techniques, the team discovered that triplet excitons could be transferred directly into inorganic semiconductors, with a transfer efficiency of more than 95%.
In this photo made Thursday, April 23, 2015, Mansfield Mayor David Cook speaks about drilling operations in his city during an interview in Mansfield, Texas. In this photo made Thursday, April 16, 2015, a worker examines components of a hydraulic fracturing well in Mansfield, Texas.
In this photo made Thursday, April 16, 2015, components of a hydraulic fracturing operation are seen behind a gated and bricked wall well site in Mansfield, Texas. In this photo made Thursday, April 16, 2015, tanks at a hydraulic fracturing well are separated from homes by a brick wall in Mansfield, Texas. In this photo made Thursday, April 16, 2015, a marker warns of an underground pipeline running next to a hydraulic fracturing well in Mansfield, Texas.
In this photo made Thursday, April 23, 2015, homes sit next to hydraulic fracturing well infrastructure pipe lines in Mansfield, Texas. In this photo made Thursday, April 23, 2015, community activist Lance Irwin talks about the wells in his city as he stands next to a hydraulic fracturing well that sits next to a community center in Mansfield, Texas. MANSFIELD, Texas (AP) — Lawmakers in Texas and energy producing states across the nation are rushing to stop local communities from imposing limits on oil and gas drilling despite growing public concern about the health and environmental toll of such activities in urban areas.
The slump in oil prices that has led to job losses in the oil patch has only added to the urgency of squelching local drilling bans and other restrictions the industry views as onerous.


In Mansfield, a wealthy suburb about 30 miles southeast of Dallas, Tamara Bounds said the loud whir of fracking a few hundred feet from her backyard kept her awake at night for nine months. Hundreds of natural gas wells dot the hilly landscape, and pipelines snake behind housing cul-de-sacs. Drilling is forging ahead in energy rich states despite growing evidence that the practices are effecting the environment.
Earthquake activity in 2013 was 70 times greater than it was before 2008, Oklahoma geologists reported. When a single Texas community, the university town of Denton near Dallas, voted last fall to impose a ban on fracking within its boundaries, lawmakers in the Republican-controlled Texas Legislature sprang into action to ensure others wouldn’t follow suit. There are no fewer than 11 Texas bills designed to ban future local limits on energy production.
The state’s energy industry lobbied heavily to ensure passage of the Texas legislation, which allows communities to have a say in things above the surface of the ground such as noise, lighting and traffic. In Mansfield, the looming law is throwing into doubt an ordinance passed in March that includes notifying potential home buyers if a gas well has been permitted within 300 feet of their property. However, in pentacene, a type of organic semiconductor, the absorption of a photon leads to the formation of two electrons. Spin-singlet excitons are ‘bright’ and their energy is relatively straightforward to harvest in solar cells. Oil and gas companies in states where hydraulic fracturing has unlocked vast shale reserves are lobbying hard to keep cities and counties from approving local ordinances that could stymie drilling and exploration activities before they’ve fully tapped potential bonanzas. The number of jobs nationwide in the sector that includes energy production has fallen 3.5 percent since December, and Texas alone lost about 25,000 jobs in March, according to federal data.
And two of the biggest energy producers in the nation, Texas and Oklahoma, are poised to ban cities and towns enacting any ordinances considered unreasonable to energy exploration, including limits on fracking, water disposal, well maintenance and other activities.


I had to barricade my windows with mattresses,” said Bounds, who is running for the city council on a platform that includes tighter control of oil and gas activities.
A 16-well pad site and compressor station hums behind the city’s performing arts center.
Drilling operations contributed more than $12 billion to state coffers in 2013, accounting for about 4.5 percent of the budget.
But these electrons are not free and they are difficult to pin down, as they are bound up within ‘dark’ triplet exciton states.
Triplet-spin excitons, in contrast, are ‘dark’, and the way in which the electrons spin makes it difficult to harvest the energy they carry.
In the last decade, fracking spawned a massive expansion in drilling that pushed the United States to the number one oil and gas producer in the world. Mayor David Cook is an example of the fine line some public officials try to walk in Texas between protecting their communities and supporting the oil and gas industry.
After that, you do everything you can do to develop the economy of the state of Texas,” Cook said. He backs the natural gas drilling in the area but opposes efforts by the state Legislature to prohibit communities from setting some rules.
Now, state lawmakers are stepping in to shut down the groundswell of local activism in order to keep the energy expansion rolling.



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