New Material for Ultra-Thin Solar Cells
They say 'thin is in' for electronics, but actually achieving that can be very difficult, depending on what it is you are trying to do. For solar cells, making something thin requires the right material and the right connections to keep the energy from being lost before it is used. Tungsten diselenide would work for converting light to electricity, but actually using it to harvest power would have been very difficult, but researchers at the Vienna University of Technology have recently found a way to do it.
Tungsten diselenide is a semiconductor just three atoms thick, with a layer of tungsten between two layers of selenium. It has previously been shown that it can convert light into electricity and back, but for use in a solar cell, it would need electrodes to be attached to it every few micrometers. Without these electrodes, the electrons excited by the light would just fall back into their holes, losing their energy. The researchers found that if a layer of molybdenum disulphide were placed on top though, the electron-hole pairs would not recombine, because the holes would remain in the semiconducting tungsten diselenide while the electons would migrate to the molybdenum disulphide. Electrodes would then be able to pull the electrons away, to be put to use.
As these materials are just atoms thick, the resulting solar cell is considered ultra-thin and is so light weight that 300 m2 of it would come it at one gram. It is also thin enough to make it transparent and very flexible, though the former may change as the researchers try adding more layers to generate more electricity.
Source: Vienna University of Technology