Enhanced photoabsorption in front-tapered single-nanowire solar cells

Vertically aligned single-nanowire is verified to be a unique building block to realize the high-efficiency solar cell beyond Schockley-Queisser limit. We proposed a front-tapered vertically aligned single-nanowire solar cell (V-SNSC) and investigated numerically the possibility of this configuration to improve the photoabsorption efficiency compared to the conventional designs, by using 2.5D full-wave finite-element method. The influences of the feature sizes of aspect ratio, bottom radius, and nanowire length on the light-trapping properties were explored; the detailed field distribution and carrier generation rate were revealed as well based on the theory of dielectric resonant antenna, in order to elucidate the underlying physical mechanism. Results showed that, compared with the cylindrical counterparts, the absorption capability of V-SNSCs could be greatly enhanced by using a front-tapered configuration with less material utilized, and that such a positive effect can be further strengthened by increasing the nanowire length. The proposed configuration provides a promising approach to engineer the photoabsorption in the photovoltaic and other optoelectronic devices.