Figure 1.

Survey of the reported formabilities of the 3D and 1D polymorphs of nearly all known inorganic and hybrid ABX₃ compounds, where A is an alkali metal, organic cation (MA⁺ or FA⁺), or other single-charged metal ion (Ag⁺, Tl⁺, or Cu⁺); B = Pb, Sn, Mg, Ca, Sr Ba, Ti, V, Cd, Hg, Mn, Cu, Co, Zn, Tm, Dy, or Yb; and X = F, Cl, Br, of I. The tolerance and octahedral factors were mainly taken from the recent report of Travis etal.¹¹⁴ (a) Ideal 3D cubic interconnection of PbX₆ octahedra, as observed in α-FAPbI₃; (b) orthorhombically distorted 3D polymorph, which is commonly reported for CsPbBr₃ and was observed in FA-doped CsPbI₃ NCs in this study; (c) 1D hexagonal lattice found in the yellow FAPbI₃; and (d) 1D orthorhombic lattice found in the yellow CsPbI₃.