Technical advantages and challenges for core-shell micro/ nanowire large area PV devices

A promising field for future low cost, medium efficiency solar cell devices is the use of vapor-liquid-solid (VLS) grown nanowires or micropillars (NWs referring to both) as the active region of large scale (greater than 1 mm2 area) photovoltaic devices. There are several advantages of using NWs. The NWs can be doped as grown, helping with formation of a PV structure. NW-based PV structures require shorter carrier diffusion distances than are needed for a similarly thick planar absorber layer. At the same time, due to scattering and other optical phenomena the NW structure is able to trap more light and improve the overall light absorption. This, combined with the ability to grow nanowires on cheap substrates or reuse the growth substrate multiple times, makes NWs promising for future generation PV devices. In order for NWs to perform to their full potential several technical challenges need to be overcome. In this paper we will discuss these technical challenges in conjunction with the advantages of using NWs in large scale PV devices. We will also outline the progress that we and others have made in overcoming these challenges on the way to making nanowires a viable PV technology.