This study investigates the effect of surface passivation on the optoelectronic and structural properties of Cs0.1FA0.9PbI3 perovskite, with additional focus on the interface between the perovskite absorber and the hole transport material (HTM). Antioxidant based passivation agents, including gallic acid and L-ascorbic acid, were applied to the perovskite surface prior to HTM deposition using Spiro-OMeTAD. The films were characterized using Time Resolved Photoluminescence (TRPL) to evaluate charge carrier recombination dynamics, as well as UV-Visible absorption spectroscopy and X-ray diffraction (XRD) to assess optical properties and crystallinity. TRPL results showed that surface passivation alone led to only slight improvements in carrier lifetime, likely due to the dominant role of bulk defects. However, passivated samples combined with HTM showed noticeable lifetime enhancement, indicating improved interfacial charge dynamics. Interestingly, the standard perovskite with HTM (without additional passivation) exhibited the longest carrier lifetime, potentially due to Spiro-OMeTAD’s intrinsic passivation effect or interference from the added passivation layers. UV-Vis and XRD analyses confirmed that the treatments did not affect the material’s bandgap (1.55 eV) or crystal structure. These findings emphasize the importance of interface optimization in perovskite devices and highlight the complex interactions between surface treatments and charge transport layers.