Minority carrier lifetime and surface effects in VLS-grown axial p-n junction silicon nanowires.

High aspect ratio p–n junction semiconductors have displayed great potential for emerging photovoltaics owing to enhanced properties such as improved light absorption or trapping effi ciency and facile carrier collection. [ 1–4 ] In the case of bottomup synthesized p–n junction nanowires, additional advantages come from their single-crystalline structure and reduced materials usage, coupled with the fl exibility of non-conventional device substrates. [ 1–3 ] The current rectifi cation in p–n junction semiconductors is based on the transport of minority carriers as opposed to the majority carrier-driven metal–semiconductor Schottky diodes with similar rectifi cation. [ 4 ] The minority carrier lifetime affects both the illuminated and dark characteristics of the photovoltaic cell and directly determines its effi ciency; therefore, its reliable characterization is critical for assessing and optimizing p–n junction nanowire-based photovoltaic devices. Moreover, the electrical and optical properties of p–n junction nanowires depend on the p–n junction geometry, for example, radial vs axial heterostructures, [ 5 ] implying the possible correlation of the nanowire geometry with the minority carrier dynamics and the resulting rectifi cation characteristics. The carrier lifetimes of bottom-up nanowires have been characterized with various techniques, including electron-beam induced current (EBIC), [ 6 , 7 ] photoluminescence (PL) decay, [ 8 ]