Structural, optical, and electronic properties of single crystals of 4H lead-based hexagonal hybrid perovskite

Lead halide hybrid perovskite single crystals have been grown using antisolvent vapor-assisted crystallization. The chemical composition and structural model of the crystals have been established using nuclear magnetic resonance and single crystal x-ray diffraction, leading to the formula FA0.9MA0.1PbI2.23Br0.77. The hexagonal crystallographic structure with P63/mmc space group has been confirmed by transmission electron microscope study. Through a detailed analysis of the single crystal XRD data, the locations of FA+ and MA+ in the unit cell have been identified, and the off-centering of Pb2+ on the octahedral sites has been unveiled, probably due to the Pauli repulsion of the lone pair. This material is a wide-gap semiconductor with Eg = 2.27 eV and demonstrates photoluminescence activity. The thermal conductivity is disorder-dominated with an extremely low value of 0.17Wm-1K-1 from about 75 K up to 325 K. The present investigation on FA0.9MA0.1PbI2.23Br0.77 single crystal demonstrates that low values of thermal conductivities are obtained in this hexagonal family of hybrid halide perovskites, with mixed cationic and anionic disorder. © 2024 American Physical Society.