Solar energy breakthrough creates electricity from invisible light

Two major breakthroughs in solar cell technology could vastly improve the way energy is harvested from the sun.

The two studies, published in Nature Energy and Nature Photonics, will transform the efficiency and significantly reduce the cost of producing solar cells, scientists say.

The first breakthrough involves “upconverting” low energy, non-visible light into high energy light in order to generate more electricity from the same amount of sunlight.

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Researchers at RMIT University and UNSW University in Australia and the University of Kentucky in the US discovered that oxygen could be used to transfer low energy light into molecules that can be converted into electricity.

“The energy from the sun is not just visible light. The spectrum is broad, including infrared light which gives us heat and ultraviolet light which can burn our skin,” said Professor Tim Schmidt from UNSW Sydney.

“Most solar cells... are made from silicon, which cannot respond to light less energetic than the near infrared. This means that some parts of the light spectrum are going unused by many of our current devices and technologies.”

The technique involves using tiny semiconductors known as quantum dots to absorb the low energy light and turn it into visible light to capture the energy.

Shape Created with Sketch. New roof for Notre Dame would harness solar power Show all 12 left Created with Sketch. right Created with Sketch. Shape Created with Sketch. New roof for Notre Dame would harness solar power 1/12 A truly modern design for the refurbishment of Notre Dame Cathedral would see a new roof that harnesses solar energy to provide enough energy to power nearby buildings Vincent Callebaut Architectures 2/12 Paris-based Vincent Callebaut Architectures have designed a roof consisting of diamond-shaped glass panels propped up with laminated wooden beams Vincent Callebaut Architectures 3/12 The architects claim that the panels would store solar power in hydrogen fuel cells, turning Notre Dame into an energy-positive building. As more than enough energy would be stored to power the Cathedral, the excess could be channelled to nearby buildings Vincent Callebaut Architectures 4/12 The roof would also house a garden in which the fruit and vegetables grown would be distributed for free to poor and homeless Parisians Vincent Callebaut Architectures 5/12 The west facade of Notre Dame Cathedral with the proposed roof Vincent Callebaut Architectures 6/12 The east facade of Notre Dame Cathedral with the proposed roof Vincent Callebaut Architectures 7/12 The north facade of Notre Dame Cathedral with the proposed roof Vincent Callebaut Architectures 8/12 Vincent Callebaut Architectures 9/12 Alternative designs This earlier design is described by Italian architect duo Studio Fuksas as "a crystal, spiral symbol of the fragility of history and spirituality" Studio Fuksas 10/12 Alternative designs In this design from Slovakian architect Vizum Atelier, the replacement spire would shoot a beam of light up towards the sky Vizum Atelier 11/12 Alternative designs Alexandre Fantozzi thinks that the stained glass windows are the best feature of Notre Dame therefore he proposes that the roof should consist solely of stained glass Alexandre Fantozzi 12/12 Alternative designs Another earlier design from Studio NAB design for the restoration of Notre Dame Cathedral proposes that a greenhouse be built in place of the old, wooden roof Studio NAB 1/12 A truly modern design for the refurbishment of Notre Dame Cathedral would see a new roof that harnesses solar energy to provide enough energy to power nearby buildings Vincent Callebaut Architectures 2/12 Paris-based Vincent Callebaut Architectures have designed a roof consisting of diamond-shaped glass panels propped up with laminated wooden beams Vincent Callebaut Architectures 3/12 The architects claim that the panels would store solar power in hydrogen fuel cells, turning Notre Dame into an energy-positive building. As more than enough energy would be stored to power the Cathedral, the excess could be channelled to nearby buildings Vincent Callebaut Architectures 4/12 The roof would also house a garden in which the fruit and vegetables grown would be distributed for free to poor and homeless Parisians Vincent Callebaut Architectures 5/12 The west facade of Notre Dame Cathedral with the proposed roof Vincent Callebaut Architectures 6/12 The east facade of Notre Dame Cathedral with the proposed roof Vincent Callebaut Architectures 7/12 The north facade of Notre Dame Cathedral with the proposed roof Vincent Callebaut Architectures 8/12 Vincent Callebaut Architectures 9/12 Alternative designs This earlier design is described by Italian architect duo Studio Fuksas as "a crystal, spiral symbol of the fragility of history and spirituality" Studio Fuksas 10/12 Alternative designs In this design from Slovakian architect Vizum Atelier, the replacement spire would shoot a beam of light up towards the sky Vizum Atelier 11/12 Alternative designs Alexandre Fantozzi thinks that the stained glass windows are the best feature of Notre Dame therefore he proposes that the roof should consist solely of stained glass Alexandre Fantozzi 12/12 Alternative designs Another earlier design from Studio NAB design for the restoration of Notre Dame Cathedral proposes that a greenhouse be built in place of the old, wooden roof Studio NAB

The second breakthrough makes use of a type of material called perovskites to create next-generation solar modules that are more efficient and stable than current commercial solar cells made of silicon.

Solar cells made from perovskites are also cheaper to produce, as well as being flexible and lightweight. Until now, the main issue with the material is that it is difficult to scale up to create solar panels several metres in length.

“Scaling up is very demanding,” said Dr Luis Ono, a co-author of the study. “Any defects in the material become more pronounced so you need high-quality materials and better fabrication techniques.”

A new approach makes use of multiple layers to prevent energy being lost or toxic chemicals from leaking as it degrades.

A module measuring 22.4cm achieved an efficiency of 16.6 per cent – a very high efficiency for a module of that size – and maintain a high performance level even after 2,000 hours of constant use.

The researchers now plan to test their techniques on larger solar modules, with the hope of commercialising the technology in the future.