InN p-i-n Nanowire Solar Cells on Si

In this paper, we report the first experimental demonstration of InN nanowire solar cells. By employing an in situ deposited In seeding layer, we have achieved electronically pure, nearly intrinsic InN nanowires directly on Si(1 1 1) substrates by molecular beam epitaxy. The growth and characterization of Si- and Mg-doped InN nanowires is also investigated, which can exhibit superior structural and optical properties. We have further studied the epitaxial growth, fabrication, and characterization of InN:Si/i-InN and InN:Mg/i-InN/InN:Si axial nanowire structures on p-type and n-type Si(1 1 1) substrates, respectively. With the use of a CdS surface passivation, InN:Mg/i-InN/InN:Si nanowire homojunction solar cells exhibit a promising short-circuit current density of ~14.4 mA/cm² and power-conversion efficiency of ~0.68% under simulated one-sun (AM 1.5G) illumination. This work suggests the first successful demonstration of p-type doping in InN nanowires and also constitutes important progress for the development of InGaN-based, full-solar-spectrum photovoltaics.