Core-Shell Heterojunction Solar Cells Based on Disordered Silicon Nanowire Arrays

Heterojunction with intrinsic thin layer (HIT) solar cells are still costly due to the use of silicon wafers that contribute to ∼30% of the final module cost. To reduce the costs, thinner wafers can be used but to the detriment of the optical absorption. This loss has to be compensated by an efficient light trapping scheme. In this paper we study HIT devices based on Si nanowire (SiNW) core-shell structures to enhance light absorption. The SiNWs are fabricated by a wet etching technique, and the heterojunction is formed using an optimized low-temperature plasma enhanced chemical vapor deposition (PECVD) process at 200 °C. The solar cells are characterized via carrier lifetime and electron beam induced current (EBIC) measurements to understand their electrical properties at nanoscale. The impact of the SiNW length on the cell performance is also investigated. The solar cells show a good performance reaching average fill factor of 81%, V_oc of 0.525 V, and J_sc of 29.27 mA/cm² giving rise to an average efficiency of 12.43%. Finally, the fabrication procedure is applied to epitaxial Si thin films, and the performance of such devices is discussed.