Mixing of Spacer Cations in 2D Halide Perovskites

. Our findings show that mixing spacers can lead to higher symmetry, significantly suppress out-of-plane tilting, and give rise to a unique rippling structure in some systems. The optical bandgaps of the mixed-spacer 2D perovskites are typically located between those of the two parent phases. Finally, we extend this approach to systems incorporating up to five spacers in a single system, with phase purity confirmed through powder and single-crystal X-ray diffraction characterizations. This work offers simple yet practical indicators for selecting compatible spacer cations, providing a pathway to better understand how spacer mixing influences the structural, physical, and optical properties of 2D perovskites.