Correction: A review of polytypism in lead iodide

Abstract

Lead Iodide (PbI 2 ) is an important inorganic solid for both basic scientific research and possible technological applications and in this brief review we discuss the structure of PbI 2 . Although the basic structure is a simple I-Pb-I layered structure with a [PbI 6 ] 4-near-octahedron being the basic building block, there are many ways of stacking the layers which results in many polytypes. We present 20 of the 23 entries for the structure of PbI 2 from the Inorganic Structural Database and order them by polytype. This represents more than 80 years of crystallographic research in the structure of this compound. We present a simple way to view the 2H, 4H, 6H, and 6R polytypes and extend the procedure to higher-order polytypes. We note a relationship, not generally appreciated, between the distortion of the near [PbI 6 ] 4-octahedrons and the polytype. We suggest that the significance of vacancies has only recently been appreciated. We suggest that small discrepancies in structure determination are probably due to different distributions of vacancies and that there are, in practice, very many structures for macroscopic or even mesoscopic samples of a given polytype when vacancies are considered.

Comparative Study of Vapor- and Solution-Crystallized Perovskite for Planar Heterojunction Solar Cells

“…Because the c-TiO 2 blocking layer presents a smooth surface, we thus prepared CH 3 NH 3 PbI 3 on noncrystal glass and the patterns are shown in Figure . According to the literature, spin-coated PbI 2 from DMF solution at room temperature demonstrated 2H polytype, with the most intense (001) diffraction peak at 12.65° . CH 3 NH 3 PbI 3 showed characteristic peak of (110) at 14.08° .…”

“…According to the literature, spin-coated PbI 2 from DMF solution at room temperature demonstrated 2H polytype, with the most intense (001) diffraction peak at 12.65°. 32 CH 3 NH 3 PbI 3 showed characteristic peak of (110) at 14.08°. 33 In solution-crystallized method, the conversion of PbI 2 to CH 3 NH 3 PbI 3 was incomplete after 2 min of dipping, with (001) peak of PbI 2 still remaining.…”

“…This could be attributed to the drastic chemical reaction when dipping PbI 2 -coated substrates into CH 3 NH 3 I solution, where the yellow color changed into dark brown immediately after dipping. The crystallization process of CH 3 NH 3 PbI 3 perovskite featured the insertion of CH 3 NH 3 I into layered PbI 2 crystals . Drastic crystallization of perovskite might break the layered structure of PbI 2 and distorted the smooth morphology, resulted in perovskite crystals with disordered alignment.…”

“…Figure 1b, d, and f showed the corresponding cross-view SEM images. In Figure 1a, PbI 2 smoothly covered almost the entire area of 32 Drastic crystallization of perovskite might break the layered structure of PbI 2 and distorted the smooth morphology, resulted in perovskite crystals with disordered alignment. However, the vapor-crystallization method was featured with a much more moderate chemical reaction, and the color changed slowly from yellow to dark brown.…”