The chemical composition of a ~1 cm 2 cleaved piece of as-grown MAPbBr3 was analyzed using a Thermo Scientific Escalab xi + X-ray Photoemission Spectrometer (XPS) equipped with a monochromatic X-ray source with an Al anode producing characteristic X-rays with photon energy of 1487 eV. The XPS spectrum was measured at the crystal surface that was in contact with the glass substrate during growth propagation. A survey scan was measured along with high resolution scans of Pb 4f, O 1s, N 1s, Br 3d, and C 1s core levels to evaluate the MAPbBr3 chemical composition on the sample surface. All spectra were collected without the use of a flood gun to neutralize the sample.