Conventional self-assembled monolayer (SAM) hole transporters in organic solar cells (OSCs) generally suffer from poor uniformity and limited thickness tolerance, hindering their large-scale production. To overcome these limitations, we introduce a novel polymeric hole transporter synthesized by polymerizing carbazole phosphonic acid (PACz). The resultant Poly-2PACz material exhibits exceptional conductivity, high tolerance for variations in layer thickness, and improved film uniformity compared with conventional SAMs. Consequently, the OSCs utilizing Poly-2PACz achieve a remarkable power conversion efficiency of 19.1% and a high fill factor of 81.2%, surpassing the devices based on 2PACz. Moreover, Poly-2PACz-based OSCs demonstrate excellent operational stability, retaining over 80% of their initial efficiency after 1,400 h of continuous light exposure in ambient conditions. This work presents a novel strategy for designing hole transporters, paving the way for more efficient and stable OSCs.