# Growth mechanism of oleylammonium-based tin and lead bromide perovskite nanostructures

## TL;DR

This paper explores how tin and lead bromide perovskite nanostructures grow, showing that tin bromide tends to form more complex 2D or 3D structures than lead bromide.

## Contribution

The study reveals that tin bromide is more prone to forming higher-order 2D or 3D nanostructures compared to lead bromide, using combined experimental and theoretical approaches.

## Key findings

- Tin bromide is more inclined to form higher-order 2D Ruddlesden–Popper or 3D nanostructures than lead bromide.
- Precisely tuned CsSnBr3 3D nanocrystals (7 and 10 nm) were synthesized using standard surface ligands.
- Residual 2D RP nanostructures preferentially position at the interface with the substrate in coexisting 3D and 2D suspensions.

## Abstract

Metal halide perovskites, particularly using tin and lead as bivalent cations, are well known for their synthetic versatility and ion mobility. These materials possess intriguing ionic properties that allow the formation of 2D Ruddlesden–Popper (RP) and 3D metal halide perovskite nanocrystals (NCs) under similar synthetic conditions. We studied the synthesis mechanism of oleylammonium-based Sn and Pb bromide perovskites 2D Ruddlesden–Popper (RP) in comparison with the 3D CsPbBr3 and CsSnBr3 NCs. Using experimental techniques in combination with theoretical calculations, we studied the interactions of the long-chain organic cations with the inorganic layers and between each other to assess their stability. Our findings suggest that tin bromide is more inclined toward forming higher-order RP phases or 3D NCs than lead bromide. Furthermore, we demonstrate the synthesis of precisely tuned CsSnBr3 3D NCs (7 and 10 nm) using standard surface ligands. When the 3D and 2D tin halide perovskite nanostructures coexist in suspension, the obtained drop-cast thin films showed the preferential positioning of residual RP nanostructures at the interface with the substrate. This study encourages further exploration of low-dimensional hybrid materials and emphasizes the need for understanding mechanisms to develop efficient synthetic routes for high-quality tin-halide perovskite NCs.

Our experimental and theoretical studies have inferred that tin bromide is more susceptible to form higher order 2D Ruddlesden-Popper or 3D perovskite nanostructures than lead bromide.