Efficient broadband light absorption enhancement in InP/ZnO core-shell nanocone arrays for photovoltaic application

Nanowire solar cells are of great interests due to their promising prospects as nano-electronic power sources. Here, we propose a standing semiconductor-dielectric core-shell nanocone array (CSNCA). We find that the CSNCA structure can not only concentrate the incident light into the structure, but also confine most of the concentrated light to the semiconductor (InP) core region, which enhances remarkably the light absorption of the more material-saving semiconductor core. Thanks to the gradient of diameter size along the axial in cone, incident light of different wavelengths can be maximally coupled into the core. We find guided resonance features along the radial and FP-resonant features along the axial by analyzing the electric field patterns at the absorption spectrum peaks. The CSNCA can support multiple higher-order HE modes, in comparison to the bare nanocone array (BNCA). Interaction of the adjacent higher-order HE modes results in broadband light absorption enhancement in the solar radiation spectrum. Carrier generation rates (G) have also been studied when the electrical part is discussed. CSNCAs show a unique advantage in G distribution. Results based on detailed balance analysis demonstrate that the core-shell design gives rise to higher short-circuit current and open-circuit voltage, and thus higher power conversion efficiency. This advantage is more apparent in thin structures compared with the thick ones. Detailed research is focused on the 1 mu m high CSNCAs, and a remarkable enhancement (42.2%) is gained compared with the BNCAs. Our study shows that the CSNCAs can be promising candidates for application in super miniature photodetectors, nanometer power sources and ultra-thin film solar cells.