Nanowires are the key to making the solar cells of the future much more efficient. Nanotechnology researchers in Lund have spent a couple of billion Swedish crowns over the past 10-15 years on academic and industrial research and development of nanowires. The wires are semiconductor rods developed with specialised technology in research laboratories in Skåne.
The efficiency of an ordinary solar cell is currently around 15 per cent, but the vision is to use nanowires to eventually produce solar cells with an efficiency of up to 50 per cent. In practice, this means that the solar cells of the future could produce three times as much electricity from the same surface area as the ones we have today.
The brain behind the nanowire research is mainly that of Lars Samuelson, a physics researcher at the Faculty of Engineering who created the nanometer consortium at Lund University. During his time as a visiting researcher in Japan during the 1990s, he realised that it would be possible to produce nanowires and use them in advanced electronics and optoelectronics. Since then, his research has been almost exclusively focused on nanowires.
To enter the lab at the nanometer consortium, you have to wear protective clothing in the form of a blue lab coat, shoe protectors and a chic cloth bag on your head. No particles can be permitted to contaminate the superclean research spaces. Lars Samuelson puts on his protective gear with a practised air – the lab is his home turf. Visitors unfamiliar with the environment can easily feel that they have ended up in a UFO, full of devices, tubes and various weird contraptions.
Lars Samuelson is one of the founders of and research leaders of two companies, Glo and Sol Voltaics, located in the Ideon research park in Lund. Both companies are working on nanowires; Glo for light-emitting diodes and Sol Voltaics for solar cells. In the first case, the aim is to make electricity into light; in the second, to make light into electricity.
Usually, nanowires are produced on a semiconductor plate using so-called epitaxy, a process which resembles growing a lawn formed of nanoblades. A few years ago, however, the Lund researchers were able to show that nanowires can also be produced through aerotaxy, in which the threads are formed while freely floating in nitrogen gas, for example. Currently, Sol Voltaics is building up a pilot facility in a factory, with the aim of producing enough nanowires for solar cells with an annual capacity of 5 megawatts – approximately a quarter of those installed in Sweden last year.
“Sol Voltaics has a twofold aim. One is to create a flexible thin film in which the nanowires are integrated, which reduces the cost and has the same properties as an ordinary semiconductor with a crystalline structure, but with the advantage of flexibility. The other is to produce nanowires in a gas environment, which makes production 100 times cheaper than normal”, says Lars Samuelson.
Currently, 90 per cent of the solar cell market consists of silicon cells, but if the thin film is applied over a normal standard solar cell, its efficiency increases dramatically, for example from 15 to 25 per cent.
A large part of the research into nanowires thus deals with increasing efficiency and reducing costs. But Lars Samuelson is also passionate about ensuring that the research also benefits developing countries, for example in the form of energy-efficient electricity generation and lighting.
“The light can be used in everything from giving schoolchildren the chance to do their homework in the evenings to creating a better lit local environment, or for communication purposes. For example, the technology can also be used to improve water purification processes, and I am very happy that our research is able to contribute this type of societal benefit” he says, removing his protective clothing. The day’s visit to the nanolab is over, but he will be back here tomorrow.