The average solar cell that you might see on the roof of a house has an efficiency of about 10 to 15% and usually made of silicon. One class of semiconductor frequently used in efficient solar cells is the III-Vs, where efficiencies of over 40% are possible when the cells are coupled with external optical concentrators. In addition, by making clever use of nanotechnology and quantum engineering, the device performance can be further enhanced. One technique is the use of quantum dots where due to quantum confinement effect, they are able to absorb the spectrum of light which cannot be absorbed by conventional silicon solar cells. Quantum dots also have a few unique properties that could be advantageous for solar cell applications, such as multi-photocarrier-generation effect, longer carrier life-time, flexibility in bandgap engineering. Another technique is using the intrinsic properties of nanowires such as (i) the large surface area, (ii) high aspect ratios (iii) the intrinsic antireflection effect that increases light absorption and (iv) more importantly, they provide a paradigm shift in photovoltaics by decoupling light absorption from carrier collection paths, which lead to more efficient charge extraction. In addition by embedding the nanowires in polymers that can be peeled off, the nanowire cell layer can be separated from the underlying wafer, in effect creating a flexible nanowire solar cell that you can wear.