Nanowires may increase solar cell efficiency

Ars Technica : Nanowires are being experimented with for use in solar cells because they use less material and are potentially less expensive than conventional materials. Jesper Wallentin of Lund University in Sweden and his colleagues have found that two characteristics of nanowires are important for determining their efficiencyâmdash;the diameter of the wire and the superconducting characteristics of the material. Their model showed that if the wire’s diameter was less than the sunlight’s wavelength, the wires resonated, which increased the amount of energy absorbed. They found the optimum diameter to be 180 nm. They also determined that layering doped and undoped material significantly increased the absorption of the wires. Wallentin’s team tested the models using indium phosphide (InP), also commonly used in conventional solar cells. They more than doubled previous nanowire-cell efficiency to 13.8%, still significantly less than the 22.1% of conventional InP cells. However, the new cells used only 12% of the surface area required by conventional cells. Although the nanowire cells didn’t match current capabilities, they represent a significant step forward and could be the key to reducing solar cell cost.