The XPS data was analyzed using CasaXPS processing software. All MAPbBr3 XPS spectra were calibrated to the adventitious carbon on the sample surface used as a charge correction reference peak region with peak centered adjusted to 284.8 eV. The O 1s, C 1s, and Br 3d5/2 3d3/2 high-resolution spectra backgrounds were treated with Tougaard function, a linear function was used for N 1s, and the core level Pb 4f7/2 4f5/2 background was modeled with a Shirley function.