Try to imagine the best way to power nanoscale electronics; for consistency and practicality, a nanoscale battery would be ideal. To that end, scientists at Harvard University have developed the first self-contained nanoscale solar cell, in the form of a coaxial silicon nanowire. Constructed from concentric layers of crystalline silicon doped with boron or phosphorus, the nanowire has an approximate diametre of 200 nm. When struck by sunlight, electrons and positively-charged molecular ‘holes’ move inversely between the layers of the nanowire, creating enough current to power an electric circuit. While still quite inefficient (the nanowire converts only 3% of sunlight into power, whereas conventional solar cells operate at 20-25% efficiency), the development is exciting in that offers an entirely new geometry for photovoltaic cells. Improved efficiency should eventually see the nanowire offering reliable and harvestable energy for nanoelectronics. I wonder if a nanoscale solar battery for my laptop is out of the question…..?
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