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Rolling an atom-thick semiconductor layer into a nanoscale tube allows it to convert solar energy into electricity without the need for semiconductor junctions — prerequisite features of conventional solar cells.
For decades, the development of a cheap and efficient way to convert sunlight into electricity has been at the forefront of research, from the physical sciences to engineering. Usually, devices for harvesting solar energy, called solar cells, are made of semiconductors such as silicon. In these devices, electrical power is generated at the junction between two types of semiconductor material. However, the efficiency of junction-based solar cells has almost reached its theoretical limit, and it is therefore imperative to explore methods for converting sunlight into electricity that do not require semiconductor junctions. Writing in Nature, Zhang et al.1 report a key advance in this direction. They demonstrate a junction-free solar cell that is produced by curling an atom-thick semiconductor layer into a nanoscale tube.