The effects of geometry and horizontal positioning of ultrathin triangular silicon nanowires (SiNWs) on the function of solar cells (SCs) have been investigated. Two differentiated methods have been presented to improve the current density of SiNW-SCs. First, a semiperiodic array is used for better utilization of the optical antenna effect. In the second method, several NWs with different geometries are used to achieve broadband absorption. The key to increase absorption is irregularity. Therefore, maximum light absorption is achieved by introducing irregular NWs. A set of optimized irregular NWs have better properties compared to other broadband structures. Using irregular NW arrays, the increase in the absorption of SCs can be improved without applying more absorbent materials. Optimization processes are used to obtain the maximum current density of SCs.