A collaboration between scientists at the University of Oxford and Wuhan University has made a major breakthrough in solar energy efficiency.
Researchers found that bismuth sulphide can absorb light strongly without losing the electrical charge it produces, making it a promising material for semiconductors, the part of a solar cell which converts sunlight into energy.
When a semiconductor absorbs sunlight, it uses its energy to free electrons and leaves tiny, positively charged ‘holes’ in their place. To produce electricity, these positive and negative charges must be rapidly harvested before they meet and cancel each other out. However, laws of physics state that a good absorber of light must also be a good emitter, and therefore the semiconductors that absorb light most strongly are also the ones that lose their charges most quickly.
Solar energy research has long been slowed by the difficulty of finding materials that balance semiconductor absorbency and efficiency.
The discovery of bismuth sulphide, published in Nature in October, unlocks a solution. The researchers discovered it has a rare quantum arrangement that allows it to absorb light efficiently while also making it harder for excited electrons and holes to recombine.
Solar energy constitutes only 6% of Britain’s electricity. Primarily because of Chinese investment, 91% of new global solar and wind facilities are cheaper than the cheapest available fossil-fuel power. However, weather, grid infrastructure, and technological limitations have created a firm ceiling on the UK’s solar energy harvesting. This comes as Prime Minister Andy Burnham has announced the launch of a new government body to invest in the national electricity grid, as concerns mount over the durability and capacity of the UK’s energy infrastructure.
The government projects that the solar sector will support 35,000 jobs by 2030. This includes roles within the solar technology company Oxford Photovoltaics, which contributed to the study. The company was founded in 2010 as a spin-out from the University and now claims to be “commercialising the world’s most efficient solar technology to power the next generation of clean energy”.
Solar energy is also expected to play a major role in the government’s plans for an Oxford-Cambridge ‘growth corridor’. A recent report suggests the UK’s premier innovation zone is falling behind its global rivals, as China continues to build as much as 74% of all solar and wind projects worldwide.
This discovery of the bismuth sulphide semiconductor may trigger changes in the renewable energy sector. To do so, however, requires rapid commercial implementation of the technology. Researchers have yet to establish whether the increased energy savings of bismuth sulphide are enough for it to turn a profit.
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