On the wave of the success of hybrid halide ABX3 perovskites, their related dimensional 2D layered A2MX4 analogues are also currently the object of renovated interest by the scientific community. These materials can be ideally derived from their parental 3D analogues by considering extended corner-shared MX6 sheets as progressively separated, with the interlayer space filled by bulky organic spacers, and have been object of intense studies in the early 90ies because of their unique optical properties, consisting in sharp excitonic absorption and emission, bi-excitonic features, etc. These materials are currently enjoying a second golden era, because of, among the other things, their huge structural and chemical versatility, compared to their 3D analogues. On the other hand, such chemical complexity directly calls for a deep understanding of the properties of layered 2D perovskites, aiming to direct the choice of the organic spacer on a rational base. In this contribution, recent results achieved by our group in understanding the electronic and optical properties of layered hybrid halide perovskites will be illustrated. The quantum-well-like electronic structure of 2D layered perovskites is studied on the basis of advanced Density Functional Theory calculations and of composite approaches, with the properties of the organic spacers and of the inorganic sheet investigated both separately and in the composite material. Then, the various mechanisms through which the spacer can affect the electronic properties are explained and quantified, with specific focus on quantum and dielectric confinement and structural effects. Finally, the electronic properties of lead-deficient halide perovskites are discussed. In these materials, lead vacancies are found to self-organize in ordered fashion, with profound consequences on electronic quantum confinement, potentially bridging 3D halide perovskites and their dimensionally reduced 2D and 1D analogues.

Understanding electronic structure and quantum confinement in layered and deficient hybrid metal halide perovskites

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.