A group of nanoengineering researchers at Lund University working on solar cells made a breakthrough last year when they succeeded in building photovoltaic nanowires with three different band gaps. This, in other words, means that one and the same nanowire consists of three different materials that react to different parts of solar light. The results have been published in Materials Today Energy and subsequently in more detail in Nano Research.
“The big challenge was to get the current to transfer between the materials. It took more than ten years, but it worked in the end,” says NanoLund principal investigator Magnus Borgström, professor of solid state physics, who wrote the articles with Lukas Hrachowina, Yang Chen, Enrique Barrigóna, and Reine Wallenberg.
There are some ten research teams around the world who are actively focusing on nanowire solar cells.
“The challenge has been to combine different band gaps in the solar cells and that door has thus now opened at last,” says Magnus Borgström.
Alternative to silicon in the future
Solar cells with different band gaps, known as tandem solar cells, are so far mainly found on satellites and are the subject of intensive research. The aim of the research is to considerably increase efficiency, to perhaps double that of today’s commercial silicon solar cells (around 20 percent).
“Silicon solar cells have soon reached their maximum limit for efficiency. Therefore, the focus has now shifted to developing tandem solar cells instead. The variants fitted on satellites are too expensive to put on a roof,” says Magnus Borgström.