Carbon-based perovskite solar cells (C-PSCs) are garnering considerable attention in the photovoltaic realm due to their cost-effectiveness, simplified fabrication processes, and improved long-term durability. Nonetheless, their efficiency often suffers from notable non-radiative recombination at the interface of the carbon electrode and the perovskite layer, as well as inherent film defects. This investigation adopts additive engineering to address these challenges by introducing propylammonium chloride (PACl) into FA0.1MA0.9PbI3 perovskite films. The resultant films exhibit larger grain sizes and smoother surface morphology, mitigating grain boundary defects and enhancing interface quality. Additionally, PACl-treated films demonstrate heightened photoluminescence intensity and prolonged carrier lifetimes, effectively suppressing non-radiative recombination. Comparative analysis with control devices showcases a noteworthy efficiency boost in PACl-treated devices, rising from 14.74 % to 16.57 %, alongside minimal hysteresis effects and exemplary long-term stability. This study presents a simple yet highly efficient approach to enhance film morphology and rectify defects in perovskite films, leading to superior efficiency and stability in hole transport layer free C-PSCs.