Revealing the Crystallization and Thermal-Induced Phase Evolution in Aromatic-Based Quasi-2D Perovskites Using a Robot-Based Platform

Abstract

Introducing large organic cations to form reduced-dimensional (quasi-2D) perovskites has proven to be effective in stabilizing three-dimensional perovskites. In this study, we synthesized 28 Ruddlesden–Popper-type quasi-2D perovskites using four aromatic-based cations (phenylmethylammonium (PMA), phenethylammonium (PEA), phenylpropylammonium (PPA), and phenylbutanammonium (PBA)) and systematically investigated their optoelectronic and structural properties and thermal stability. A counterintuitive finding that longer-chain PPA-based films exhibited relatively poorer stability compared to films with shorter-chain cations has been found. This instability in PPA-based samples is attributed to significant lattice distortion and a mismatched phase between face-sharing trimers, causing intense configurational strain. On the other hand, PBA-containing films maintained robust structural stability due to distinctive crystallization kinetics and a gradual phase-transformation process (from larger-n to lower-n phases) induced by a stronger steric-hindrance effect. Our study sheds light on the complex impact of aromatic-based cations on optoelectronic properties and stability of perovskites, providing guidelines for the rational compositional design engineering of highly stable perovskite materials.