Creating a low-dimensional (LD) perovskite passivation layer on 3D perovskite using bulky cations is a well-established approach to achieving high-performance perovskite solar cells (PSCs). However, 2D/3D interfaces are prone to degrade under thermal stress. It is crucial to understand the formation and crystallization mechanisms of different LD structures.

A direct understanding of the formation and crystallization of LD perovskites with varying dimensionalities employing the same bulky cations can offer valuable insights into LD perovskites and their heterostructures with 3D perovskites.

In a study published in Advanced Materials, a research group led by Prof. GAO Peng from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences explored the formation dynamics of LD perovskites derived from an achiral cation and their integration with 3D perovskites to enhance thermal stability and efficiency in PSCs.

Researchers investigated the secondary amine cation of N-methyl-1-(naphthalen-1-yl)methylammonium (M-NMA⁺) and the formation dynamics of its corresponding LD perovskite. 

They found that the intermolecular π-π stacking of M-NMA⁺ and their connection with inorganic PbI₆ octahedrons within the product structures control the formation of LD perovskite. Both 1D and 2D products could be obtained in an N,N-dimethylformamide (DMF) precursor solution. The formation of 2D perovskites was uniquely dependent on heterogeneous nucleation due to the strong interaction between M-NMA⁺ and the DMF solvent, which is first reported in Ruddlesden–Popper 2D perovskites.

Besides, researchers found that the post-treatment of 3D perovskite films with an isopropanol solution of M-NMAI leads to the exclusive formation of thermally stable 1D phases on the surface. They showed that the resulting 1D/3D heterostructure facilitates PSCs to not only achieve a record efficiency of 25.51% through 1D perovskite passivation but also significantly enhance the thermal stability of unencapsulated devices at 85 °C.

This study deepens the understanding of the formation dynamics of LD perovskites, reveals the atypical crystallization kinetics of organic-inorganic hybrid perovskite, and provides an efficient strategy for fabricating stable and high-performance PSCs.