Breaking performance records with tandem solar cells

• Oxford PV layers perovskite over silicon to capture a wider wavelength range

Chris Case, primary modern technology officer at Oxford PV, firmly believes that solar needs to be 50% of the international power mix by 2050 if we are going to have a possibility to conserve this planet. 'There is no real rational factor to increase power infrastructure aside from solar,' says Case. 'There is no better power resource.'

A look at the energy industry shows he is not alone in this belief. Solar is the fastest-growing power resource in the EU-- during the summer of 2021, solar panels created a record 10% of EU electricity. This is, however, far from 50%.

The largest hurdle to solar taking a larger share of the marketplace hinges on improving the efficiency of panels (the proportion of event solar power that can be transformed to power). The fundamental cap on efficiency for single-junction cells-- the Shockley-- Queisser limit-- is around 30% for silicon-based cells. While some scientists and business owners have been trying to find methods around the trouble, others have actually turned to multiple junctions.

This is the strategy Oxford PV, a spin-out from the University of Oxford, UK, has taken. Its tandem cells have a coating of a perovskite material in addition to silicon. Perovskites can be tuned to absorb more short-wavelength, blue-green light, leaving the silicon to absorb the longer-wavelength, redder light.

The firm has actually been able to establish brand-new records for solar cell effectiveness. In 2020, Oxford PV revealed its cells can convert 29.52% of solar energy right into power. Commercial silicon panels float at 15-- 20%, with a maximum conversion rate around 26%.

At these efficiency degrees, perovskite-based tandem cells unlock to a rapid shift to solar, Case thinks. 'As we raise the efficiency, the expense of the power is reduced, which permits us to embrace something faster, which then reduces prices even more,' he states. 'And the quicker we speed up the adoption of solar, the better opportunity we need to arrest environment change.'

Oxford PV was spun out of Oxford University in 2010 by physicist Henry Snaith and Kevin Arthur-- a serial entrepreneur in high modern technology business. Case was worked with in 2014 to commercialise the item-- initially intended for building-integrated photovoltaic applications, before the focus moved to tandem solar cells.

Commercial production of the cells was due to start in 2021 at Oxford PV's commercial site in Germany-- Europe's most significant solar market. After a hold-up as a result of Covid-19 and related supply chain issues, it's currently geared up to begin later on this year. It will be the world's first volume manufacturing line for perovskite-on-silicon tandem solar cells.

The 100 megawatt/year capacity manufacturing facility will provide residential consumers initially, before branching out to commercial customers and, ultimately, the very price-sensitive utility industry.

While silicon photovoltaic panels with efficiencies over 20% are available to property owners at competitive costs currently, and improvements in silicon cell innovation are being made continuously, Case insists that it will certainly be essential to move beyond silicon if solar energy is to fulfil its capacity.

Silicon is an indirect bandgap semiconductor, so some power is constantly going to be lost in the transfer in between photons and also electrons. Silicon additionally requires to be meticulously detoxified, and also extracting and also refining it into excellent quality solar cells is a resource-intensive process. 'It takes 7 tonnes of silicon to make a million watts of solar cells however just 35kg of perovskite for the same outcome,' says Case.

Oxford PV says that the lower ecological footprint associated with generating perovskite cells rather offsets the materials' unsolved problems. One of the most prominent of these is that they consist of lead. Alternatives, such as tin, have been tried and evaluated but the performance of the cells degrades quickly.

A life-cycle evaluation of Oxford PV's tandem cells suggests that the percentage of lead they contain wouldn't have much effect on environmental toxicity if it ran away. There are strict occupational exposure limits for the degrees of lead employees can be exposed to, yet EU regulations allows for utilizing lead in solar cells. 'That doesn't indicate it's not desirable to reduce or eliminate it in the long-lasting,' claims Case, and also Oxford PV is attempting to terminate the lead that is used to attach the cables and ports in the solar panels.

Overall, Oxford PV claims generating cells with its perovskite materials is sustainable. The business released an evaluation last year revealing that there are sufficient raw materials readily available to make perovskite solar cells that would certainly create greater than 30 terawatts of power at peak effectiveness. That suffices for all the solar capacity projected to be constructed in between now and also 2050.

The company prepares to expand its existing, 100 megawatt/year capacity manufacturing facility to two gigawatts/year by 2024 and to develop extra factories every two years afterwards. By the end of the decade, Oxford PV ought to have at the very least 10 gigawatts/year of high performance solar cells in manufacturing, claims Case. 'Demand for a high effectiveness solar item is significant and there is no commercially viable choice to this item. You can make as much silicon as you desire however you can not make [solar cells] any more reliable without some multijunction method.'