A waferscale Si wire solar cell using radial and bulk p-n junctions

Silicon nanowires (NWs) and microwires (MWs) are cost-effectively integrated on a 4-inch wafer using metal-assisted electroless etching for solar cell applications. MWs are periodically positioned using low-level optical patterning in between a dense array of NWs. A spin-on-doping technique is found to be effective for the formation of heavily doped, thin n-type shells of MWs in which the radial doping profile is easily delineated by low voltage scanning electron microscopy. Controlled tapering of the NWs results in additional optical enhancement via optimization of the tradeoff between increased light trapping (by a graded-refractive-index) and increased reflectance (by decreasing areal density of NWs). Compared to single NW (or MW) arrayed cells, the co-integrated solar cells demonstrate improved photovoltaic characteristics, i.e. a short circuit current of 20.59 mA cm(-2) and a cell conversion efficiency of similar to 7.19% at AM 1.5G illumination.This work was supported by the New & Renewable Energy R&D Program (no. 2009T100100614) of the Ministry of Knowledge Economy, Korea, and the Pioneer Research Center Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (grant no. 2009-0082820). H-DU, S-WJ and K-TP acknowledge financial support from the sixth-stage Brain Korea 21 Project in 2010