In 1999, D. B. Mitzi has proposed a very convenient description of 2D hybrid perovskites from the 3D ABX3 mother structure by the dimensionnal reduction concept, leading to the well known &lt;100&gt;, &lt;110&gt; and &lt;111&gt; series. Such a process, however, cannot define all perovskite networks. Here, a new way to describe any perovskite network from the 3D mother structure through an elimination or a substitution process is proposed. Examples of 2D perovskites (B and X vacancies in planes) or B and X deficient 3D perovskites will be described. In the field of perovskite solar cells (PSC), several chemical approaches have been considered in order to improve the air stability of the well-known (CH3NH3)PbI3 (MAPI, MA+ = methylammonium) active material, this perovskite showing a fast degradation under air exposure: partial or full substitution of MA+ by one or several cations, 2D layered perovskites,... In this context, we have discovered an unprecedented family of lead and iodide deficient 3D hybrid perovskites (d-HP family), owning a general formulation (A’)3.48x(A)1-2.48x[Pb1-xI3-x], where A= MA+ , FA+, and A’= H+ (hydroxyethylammonium) or T+ (thioethylammonium). Such (A’,A)1+x[Pb1-xI3-x] perovskites result from the substitution of x (PbI)+ units by x organic cations, while keeping a 3D network of corner-sharing octahedra. In the structure, Pb2+ and I- vacancies are ordered leading to an unusual tetragonal unit cell (14/14/6). DFT investigations show that a direct band gap is kept in these materials while Eg values increases as x is increasing. These d-HP can be prepared as pure crystallized powders as well as thin films in the 0&lt;x&lt;0.20 range. The more interesting phases are those based on FA+, called d-α-FAPI-H and d-α-FAPI-T. In contrast with α-FAPI, the synthesis of these d-α-FAPI phases are carried out at room temperature. Moreover, we show that the stability of the α phase at room temperature and under ambient condition is exceptionally improved compared to both α-FAPI and α-Cs0.15FA0.85PbI3 reference materials.

Lead and halide deficient three-dimensional hybrid perovksites

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.