Perovskite solar cells (PSCs) have attracted extensive attention due to their higher power conversion efficiency (PCE) and simple fabrication process. However, the open-circuit voltage (VOC) loss remainsasignificant impediment to enhancedevice performance. Here, a facile strategy to boost the VOC to 95.5% of the Shockley-Queisser (S-Q) limit through the introduction of a universal multifunctional polymer additive is demonstrated. Thisadditiveeffectively passivates the cation and anion defects simultaneously, thereby leading to the transformation from the strong n-type to weak n-type of perovskite films. Benefitting from the energy level alignment and the suppression of bulk non-radiative recombination, the quasi-Fermi level splitting (QFLS) is enhanced. Consequently, the champion devices with 1.59eV-based perovskite reach the highest VOC value of 1.24V and a PCE of 23.86%. Furthermore, this strategy boosts the VOC by at least 0.07V across five different perovskite systems, a PCE of 25.04% is achieved for 1.57eV-based PSCs, and the corresponding module (14 cm2) also obtained a high PCE of 21.95%. This work provides an effective and universal strategy to promote the VOC approach to the detailed balance theoretical limit.