Opportunities in nanometer sized Si wires for PV applications

Quantum-confined silicon material has been a very active field of research in the years 1990–2000 with the rapid development of opto-electronics. The main application targeted by this research was a light-emitting device (either LED, or laser). In the years 2000–2010, with the emerging need for efficient and cheap photovoltaic devices, new materials, and in particular new silicon-based materials trigger again a special interest. In particular, all-crystalline-Si tandem solar cells where the high-bandgap material is provided by the 2D confinement of excitons in nm-sized nanowires could provide the high-efficiency potential of a tandem device, while taking benefit of the decade-long buildup of knowhow of crystalline silicon material technology (both science and processing). In a first part of this review, we summarize the features described in the relevant literature for the functioning of a photovoltaic device based on Si NWs. This literature shows that from the conceptual point of view such an all-crystalline-Si-tandem solar cell using quantum confined nanowires should be feasible to produce in order to achieve the goal of inexpensive high efficiency (>30%) Si-based solar cells. Keeping the fabrication of efficient photovoltaic devices as driving theme, we review the dense literature of Si nanowires. The literature on the fabrication of nanometer-sized Si nanowires is reviewed in the second part.