Dynamic Motion of Organic Spacer Cations in 2D Ruddlesden-Popper Perovskites Probed by ssNMR
Clayton Dahlman a, Rhys Kennard a, Piotr Paluch b, Naveen Venkatesan a, Michael Chabinyc a, Manjunatha Reddy c
a Materials Department, University of California, Santa Barbara, United States
b Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences
c University of Lille, CNRS, Centrale Lille Institut, Univ. Artois, UMR 8181-UCCS-Unité de Catalyse et Chimie du Solide, F-59000, France
Proceedings of Atomic-level characterization of hybrid perovskites (HPATOM)
Online, Spain, 2021 January 26th - 28th
Organizers: Dominik Kubicki and Amita Ummadisingu
Oral, Clayton Dahlman, presentation 024
Publication date: 14th January 2021

Layered hybrid organic-inorganic perovskites, such as the lead halide Ruddlesden-Popper (RP) series, are solution-processable 2D materials with tunable quantum confinement and long carrier lifetimes. 2D hybrid perovskites are formed from an ionic perovskite sub-phase (e.g. methylammonium lead iodide) and cation ‘spacer’ molecules that separate the material into layers. The soft ionic structure of layered perovskites can be influenced by static and dynamic interactions with spacer molecules, with significant impacts on optoelectronic properties relevant for device applications. In this work, dynamic motions of spacer molecules in lead iodide RP phases (n = 1) are characterized using multinuclear solid-state NMR spectroscopy at room-temperature. The site-specific rigidity of different prototypical spacers is compared using dynamic cross-polarization measurements. We find that short spacers (e.g. butylammonium and phenethylammonium) are relatively rigid near the octahedral surface, and more flexible in the interlayer. However, longer alkylammonium spacers (e.g. octylammonium and dodecylammonium) show an opposite trend, with greater rigidity deeper in the interlayer. Spacer motions observed by these measurements are too slow to couple with photogenerated carrier dynamics, but correlate with time-averaged octahedral tilting observed by XRD. These ssNMR results indicate that the interplay between spacer interactions with lead iodide octahedra (Coulombic and hydrogen-bonding) and van der Waals forces between spacers is responsible for the variety of site-specific dynamics and local structural distortions at intermediate timescales (µs-ms). This study demonstrates a general method to characterize nanoscale structures and site-specific dynamics that contribute to structural and electronic disorder in functional optoelectronic low-dimensional perovskites.

© Fundació Scito
We use our own and third party cookies for analysing and measuring usage of our website to improve our services. If you continue browsing, we consider accepting its use. You can check our Cookies Policy in which you will also find how to configure your web browser for the use of cookies. More info