Phase Transition, Dielectric Properties, and Ionic Transport in the [(CH3)2NH2]PbI3 Organic–Inorganic Hybrid with 2H-Hexagonal Perovskite Structure

• DOI: 10.1021/acs.inorgchem.6b03095
• Publication Date: 2017-04-05T10:58:39Z
• Authors: A. García-Fernández; J. M. Bermúdez-Ga...; S. Castro-García; A. L. Llamas-Saiz; R. Artiaga; J. López-Beceiro; S. Hu; W. Ren; A. Stroppa; M. Sánchez-Andújar; M. A. Señarís-Rod...
• Keywords: Monoclinic crystal system; Hexagonal phase

In this work, we focus on [(CH3)2NH2]PbI3, a member of the [AmineH]PbI3 series hybrid organic-inorganic compounds, reporting very easy mechanosynthesis route for its preparation at room temperature. We report that [(CH3)2NH2]PbI3 compound with 2H-perovskite structure experiences first-order transition ≈250 K from hexagonal symmetry P63/mmc (HT phase) to monoclinic P21/c (LT phase), which involves two cooperative processes: an off-center shift Pb2+ cations and order-disorder process N atoms DMA cations. Very interestingly, shows dielectric anomaly associated structural phase transition. Additionally, displays large values constant temperature because appearance certain conductivity activation extrinsic contributions, as demonstrated by impedance spectroscopy. The optical band gap displayed material (Eg = 2.59 eV) rules out possibility observed can be electronic points ionic conductivity, confirmed density functional theory calculations indicate lowest energy 0.68 eV corresponds iodine anions, suggests most favorable diffusion paths these anions. obtained results thus is insulator conductor, where disfavored low dimensionality structure.