On the other hand, it is very interesting to observe the impressive stability of the corresponding bromide samples. After one month of air exposure, both the XRD data and the UV-Vis absorption spectroscopy measurements are practically unchanged. This result confirms some previous evidences provided by our group highlighting the possible role of very thin surface passivation (and protective) oxide layers on Sn-and Ge-containing perovskites as well as the e) f) g) h)