Non-monotonic near-surface chemistry, surface energetics, and photoluminescence in CSS-grown MAPbBr3 films after post-deposition pressure treatment

Post-deposition pressure was used to examine how the near-surface state of MAPbBr 3 films evolves under conditions that preserve the main crystalline framework. X-ray diffraction shows that all films, from the untreated NA condition to the HP and 1–5 kPsi treatments, retain the characteristic cubic perovskite structure, while cross-sectional scanning electron microscopy (SEM) reveals continuous micrometric layers with thicknesses in the ∼ 2.6–3.8 µm range. In contrast, high-resolution XPS shows non-monotonic variations in the near-surface chemical environment across the processing conditions, particularly in the Pb- and Br-related regions, without altering the elemental identity of the films. Kelvin probe and PESA measurements further reveal a non-monotonic reconfiguration of the surface energetic landscape, with the work function varying from 4.63 to 5.00 eV and the E F − E V B M separation ranging from 0.28 to 0.68 eV. Photoluminescence measurements show a broad emission band around 547 nm and a strongly non-monotonic variation in integrated intensity across the processing conditions. These measurements show that the main crystalline phase remains preserved while condition-dependent variations are observed independently in near-surface chemistry, surface energetics, and photoluminescence. Post-deposition pressure processing is associated with measurable variations in the near-surface properties of MAPbBr 3 films.