Octahedral connectivity: Corner-shared in all 3-dimensions where smaller A-site cations reside among the empty spaces of corner-shared octahedra.

Example & Structure: ASnX3 (Cubic structure is rare and orthorhombic and tetragonal are common).

Octahedral connectivity: Same as ABX3 perovskites but the B-site bi-cation is replaced with a couple of monovalent and trivalent cations to maintain charge neutrality.

Example & Structure: A2BiAgX6; (Cubic)

Octahedral connectivity: A-site cation is replaced with longer chained organic cations, splitting the 3D octahedral network into 2D sheets.

Example & Structure: a). (RNH3)2An-1PbnX3n+1 b). (BA)4AgBiBr8 & Cs8Ag3Bi3Br20

Substituting the A-site cation with smaller ones, e.g., K+, Rb+, and NH4+.

Modification in the A- and X-site cations and anions.

Octahedral connectivity: Edge-shared, forms a 1-D chain where the empty spaces between the chains are filled by the bigger A-site cations.

Example & Structure: LiBiI4⋅5H2O (Monoclinic crystal structure with space group C2/c)

Octahedral connectivity: Corner-shared (via cis-halogen bridges) octahedral network leading to the formation of a 1D-zigzag structure

Example & Structure: (H2AETH)BiI5 (Orthorhombic crystal system)