Isaac B. Ogunniranye, Haoran Chen, Kshitiz Dolia, Scott L. Wenner, Kiran Lamichhane, Michael J. Heben, Randy J. Ellingson, Yanfa Yan, Zhaoning Song, University of Toledo, Toledo, OH Voltage losses from interfacial recombination remain a limiting factor for the performance of perovskite solar cells (PSCs), despite achieving unprecedented power conversion efficiencies (PCEs) of 27%. This study examines the processing damages induced by vacuum-based deposition processes when functional layers are applied directly onto perovskite surfaces. We employ time-resolved and steady-state photoluminescence (TRPL and PL) to evaluate carrier dynamics and processing-induced defects, external radiative efficiency (ERE) measurements to quantify non-radiative losses at the perovskite interface, and a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) for structural characterization to systematically assess the impacts of different vacuum coating strategies on perovskite film quality. Our investigation reveals that high-energy magnetron sputtering causes substantial degradation of perovskite films and induces voltage deficits exceeding 250 mV. In contrast, both atomic layer deposition (ALD) and thermal evaporation methods maintain the crystallinity and morphology of the films. An Al2O3 layer deposited via ALD directly onto the perovskite surface delivers exceptional passivation performance, yielding an external radiative efficiency of 2.26%, quasi-Fermi level splitting of 1.157 eV, and a suppression of non-radiative recombination losses by ~100 mV. These results establish ALD as the optimal damage-free method for direct functional coating and minimizing voltage losses in PSCs and present critical processing guidelines for perovskite device fabrication.