Current-Voltage Enhancement of a Single Coaxial Nanowire Solar Cell

We show that the absorption cross-section of a single absorbing nanowire can be significantly enhanced over a broad bandwidth by coating the nanowire with a transparent dielectric to create a coaxial nanowire. The coating, while by itself is not absorbing, increases the number of resonances supported by the wire and also enhances the coupling to incident light, resulting in the enhancement of absorption cross-section. When operating as a solar cell, we show that the short-circuit current of a GaAs nanowire coated with Al2O3 is strongly enhanced over that of the bare GaAs nanowire with the same absorbing volume. This addition of the transparent dielectric layer maintains the open-circuit voltage enhancement of the bare nanowire over that of a bulk GaAs cell. Similar large current-voltage enhancements are also presented for a Si nanowire coated with SiO2.