Figure 2.

Synchrotron XRD pattern (λ = 0.565 666 Å) and its Rietveld fit for ∼12 nm FAPbBr₃ NCs, containing an impurity of NH₄Pb₂Br₅ (∼6 wt %). Black, experimental data; green, calculated total trace that combines Pm3m model of FAPbBr₃ and the I4/mcm model of NH₄Pb₂Br₅;¹⁰ red, difference plot; black and magenta vertical bars indicate Bragg peak locations for FAPbBr₃ and NH₄Pb₂Br₅, respectively. Stars highlight minor peaks of an unknown contaminant. The inset illustrates the crystal structure of FAPbBr₃ and disorder of Br-anions.