Electrical characteristics of modified conical-frustum nanowires solar cell

Abstract

The optoelectronic characteristics of modified Si conical nanowires (CNW_S) solar cells are studied and analyzed. The proposed structure unit cell consists of a 2 × 2 CNWs structures with different top diameters. The electrical performance is investigated via the finite element method where all recombination losses are taken into consideration. The optical results reveal that the suggested structure with optimized CNWs diameters can support broad Mie resonances with improved optical generation rate. Further, the generated carriers are confined inside the large CNWs size with reduced surface recombination. Therefore, the modified CNWs design significantly reduces the recombination losses and enhances the electrical performance. Using ideal surface passivation, the conversion efficiency (CE) of the modified CNWs reaches 19.5% with an enhancement of 11.4%, 14%, and 18.9% compared to the conventional conical NWs with diameters of 100 nm, 240 nm, and 400 nm, respectively. This is due to the asymmetry of the reported CNWs which widens the optical absorption and increases the CE. Further, the different diameters improve the index matching between the CNWs with enhanced light confinement and absorption within the large CNWs’ diameters. Therefore, the generated carriers are extracted with low sidewalls recombination rate associated with the large CNWs structure. The CE is strongly diminished to 1.2% that is lower than 1.7% of the conventional design with 400 nm diameter without surface passivation. Hence, effective sidewall passivation for the proposed CNWs design is essential to transform the efficient optical performance into a high electrical output.