Instruments SP-2300i spectrometer fitted with an Andor iDus 401 CCD detector. The PL maps were measured at 405 nm excitation with a fluence of 15 W cm -2 . The Raman measurements were carried out using Renishaw inVia Raman confocal microscope with a 532 nm excitation source. Transient absorption was performed on a setup described previously. Details can be found in Supplementary Note 1. The X-ray Photoelectron Spectroscopy (XPS) measurement was employed using a Al-Kα radiation source at photon energy 1486.6 eV. For the HAXPES measurement, a Ga-Kα radiation source at 9252.8 eV photon energy was used. Details can be found in Supplementary Note 1.