By anchoring the perovskite sites with the functional groups of CzBP (P = O···Pb, N–H···I and P = O···N–H), the bulk nonradiative recombination is suppressed and ion migration is inhibited. Doping perovskite films with CzBP led to enhanced intercrystallite interactions in the bulk and improved photoluminescence quantum yield. Using a typical electron-rich moiety as the π-linker to replace the classic alkyl spacer in CzBP facilitated the charge-carrier transport processes and the passivation effect of carbazole further contributed to high V_OC. The optimized 2,7-CzBP-treated device achieves the highest power conversion efficiency (PCE) of 25.88%, with V_OC of 1.189 V for 0.090 cm² and the perovskite solar cell module with a PCE of 21.04% for 14 cm². For 2,7-CzBP, the more extended conjugation and the more linear molecular geometry result in a more effective improvement in the performance. © The Author(s) 2025.