High efficiency III-V nanowire solar cells: the road ahead

Solar cells (SCs) based on dense arrays of III–V nanowires have long been considered strong candidates for the fabrication of stable, high power conversion efficiency (PCE) photovoltaic devices at reduced costs. Over the last two decades intense research has been devoted worldwide to the field; however, the nanowire SCs (NWSCs) reported so far in the literature have not confirmed theoretical expectations, their PCE figures remaining well below 18% under 1-sun illumination. The present work proposes an innovative strategy to overcome this limitation, i.e. through the use of intermediate-band gap semiconductors (IBGSs), namely GaNAs and related dilute-nitride III–V (III-N-V) compounds, as nanowire absorbing materials in substitution of the most common GaAs and InP. This allows us to combine the multi-band absorption functionality of IBGSs with the advantages associated with NWSCs, i.e. the super-absorptive properties of dense nanowire arrays and reduced volumes of active materials. Very high PCEs are expected for such nanowire-based intermediate band SCs. However, their practical realization requires suitably designed core-multishell radial junction nanowire heterostructures; an example of a perspective nano-device architectures is described herein. The potential and possible limitations/challenges facing current nanowire self-assembly technologies for the fabrication of the proposed III-N-V based nanowire IBSCs are discussed.