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AUSTRALIAN scientists say phosphorene could open the door to ultrathin and ultralight solar cells and LEDs.
Taking inspiration from the Nobel-prize winning method of discovering graphene, the scientists at ANU used sticky tape to peel thin layers of crystals from the black crystalline form of phosphorus, eventually creating single-atom thick layers called phosphorene.
While graphene is a great conductor, phosphorene, like silicon, is a semiconductor – but much lighter and thinner than silicon. It also has promising light emission properties, which vary widely with the thickness of the layers, enabling new flexibilities for manufacturing.
The semiconducting properties means phosphorene could be the basis for a new generation of thinner and lighter electronics, while the never-before-reported light emission properties means that changing the number of layers will allow manufacturers to tightly control the band gap, and by extension properties such as the colour of LED it would make.
The team found the optical gap for monolayer phosphorene was 1.75 electron volts, corresponding to red light of a wavelength of 700 nanometers. As more layers were added, the optical gap decreased. For instance, for five layers, the optical gap value was 0.8 electron volts, a infrared wavelength of 1550 nanometres. For very thick layers, the value was around 0.3 electron volts, a mid-infrared wavelength of around 3.5 microns.
The behaviour of phosphorene in thin layers is superior to silicon, claim the researchers, because the materials’ surface states are minimised, unlike silicon, whose surface states are serious and prevent it being used in such a thin state.