Figure 4

Peak-fitted XPS spectra of Cs1–xFAxPbBr3 QDs showing (a) N 1s core level and (b) Br 3d core level. (c) Relative ratio of elements including Cs, FA, Pb, and Br. (d) The changes of the anion to cation ratio [Br/(Cs + FA + Pb)] and the inner Br to surface Br ratio [(inner Br)/(surface Br)] in Cs1–xFAxPbBr3 QDs as a function of FA doping content.