Harvard University researchers have made solar cells that are a small fraction of the width of a human hair. The cells, each made from a single nanowire just 300 nanometers wide, could be useful for powering tiny sensors or robots for environmental monitoring or military applications. Moreover, the basic design of the solar cells could be useful in large-scale power production, potentially lowering the cost of generating solar power.

Each of the new solar cells is a nanowire with a core of crystalline silicon and several concentric layers of silicon with different electronic properties. These layers perform the same functions that the semiconductor layers in conventional solar cells do, absorbing light and capturing electrons to create electricity. To make the cells, Charles Lieber,a professor of chemistry at Harvard University, modified methods previously used to make nanowires that could serve as sensors or transistors. He then demonstrated that his solar cells can power two of his earlier nanowire devices, a pH sensor and a set of transistors.

At first, the nanowire solar cells will most likely be useful in niche applications requiring small size, such as tiny sensors, or robots whose sensors and electronics might benefit from an integrated power source. The ultimate goal would be to build electronic components that can self-assemble into devices that might not be possible to make otherwise. In addition to powering tiny machines, solar cells made from microscopic wires might eventually be bundled together into large arrays to replace conventional rooftop solar panels.

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