Figure 3.

Instability origin of (a) SnPb- and (b) SnGe-alloyed perovskites. Here, the red, green, and purple octahedral units represent [PbI₆]^4–, [SnI₆]^4–, and [GeI₆]^4–, respectively. Dashed circles in (a) denote Sn vacancies. In (b), the shell with blue-red molecules indicates the native oxide surface, and the yellow arrows indicate Ge filling into Sn vacancies. Possible strategies to improve stability involve (c) 0D nanocrystals surrounded with ligands, (d) complex surface lattice with 2D/hollow-3D structure, and (e) minimizing surface area using single crystals.