PbI2

Lead(II) iodide, PbI2, is an inorganic compound composed of lead(II) cations and iodide anions. It forms bright yellow crystals that are relatively insensitive to light and can be obtained in a range of morphologies. It is sparingly soluble in water, with solubility increasing in iodide-rich solutions due to the formation of polyiodide complexes.

PbI2 adopts a layered crystal structure in which PbI6 octahedra connect to form sheets; these sheets stack with weak van der Waals forces between them. This structure contributes to its anisotropic properties and low water solubility.

Preparation commonly involves mixing a soluble lead(II) salt, such as lead nitrate, with potassium iodide to precipitate PbI2: Pb(NO3)2 + 2 KI → PbI2(s) + 2 KNO3. The solid is typically washed and dried to yield the yellow crystals. It can also be prepared by direct reaction of lead salts with iodine-containing sources under appropriate conditions.

In modern research, PbI2 is a key precursor for lead halide perovskites used in solar cells and light-emitting devices. It is also studied for photodetector and scintillator applications. Its optical absorption in the visible range and ease of conversion to other lead halide phases underpins its utility, though commercial use is constrained by toxicity.

PbI2, like other lead compounds, is toxic and should be handled with care, using appropriate personal protective equipment and proper disposal procedures in accordance with hazardous-materials regulations.