Abstract: Two-dimensional metal halide perovskites (TMHPs) have emerged as prominent semiconductor materials in optoelectronic devices due to their composition-dependent properties. While previous research has concentrated on the types and the lengths of cations affecting TMHPs, our study systematically explores a new series of Dion-Jacobson (DJ)-phase TMHP structures featuring dithioketal-containing organic cations. Through X-ray crystallography and spectroscopy analyses, we demonstrate that steric hindrance from longer-branched groups distorts the structures and influences the photophysical behaviors of TMHPs. Additionally, we observe thermodynamically driven transitions from the DJ phase to the Ruddlesden-Popper (RP) phase when incorporating cations with extended branches, further impacting their structural and optoelectronic characteristics. Understanding and controlling these structural changes enable the design of TMHPs with tailored properties, opening avenues for advanced materials that enhance device performance.

Paper Link: https://doi.org/10.1016/j.xcrp.2025.102509