This study introduces an innovative method for functionalizing polychiral single-walled carbon nanotubes (f-SWCNTs) by depositing thin films onto n-type crystalline silicon (n-Si), thereby creating efficient heterojunction solar cells. The approach capitalizes on the effective charge separation facilitated by the built-in potential resulting from the functionalization of polychiral SWCNTs, leading to enhanced electron transfer from f-SWCNTs to Si driven by functional groups. The resulting f-SWCNT/Si heterojunction device demonstrates remarkable performance, attributed to the high optical absorption and improved charge separation and transfer mechanisms of the f-SWCNT film. Moreover, by adjusting the concentration of f-SWCNTs, the film properties and overall device performance have been customized, achieving a notable power conversion efficiency of 12 %. These discoveries serve as a foundation for the advancement of highly desirable, efficient, cost-effective, and broadband high-performance f-SWCNT/Si heterojunction solar cells