Why III-V nanowires can challenge high-efficiency photovoltaic solar cells

Photovoltaic solar cells (SCs) based on dense arrays of III-V nanowires are believed to possess huge potentials for further improvement of their solar power conversion efficiency. A strategy to achieve this goal requires the exploitation of light wave-guiding mechanism and novel physical concepts. The former mechanism is demonstrated for GaAs-AlGaAs core-shell NWs: large enhancement (up to 200x that of homogeneous - only core - nanowires) of the GaAs near band-edge absorption have been experimentally estimated and ascribed to a wave-guiding of incident light by the surrounding AlGaAs shell. Optimization of such absorption enhancement requires careful design and control of the AlGaAs shell thickness during nanowire self-assembly. Adoption of an intermediate-band gap semiconductor (IBGS) as the SC active material allows to combine the multiband absorption functionality of IBGS with advantages associated to nanowire-based SCs; the use of dilute nitrides III-V alloys within core-multishell NW-based SCs is a very promising solution. Advantages are briefly discussed, along with major challenges in self-assembling such nanowire by MOVPE.