Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049, Madrid, Spain.
Instituto de Investigaciones en Tecnología Química (INTEQUI), UNS, L-CONICET and Fac. de Qca., Bqca. y Far., UNSL, Ejercito de los Andes 950, 5700, San Luis, Argentine.
Chemistry. 2019 Mar 21;25(17):4496-4500. doi: 10.1002/chem.201806246. Epub 2019 Mar 4.
The hybrid methylammonium (MA) lead halide MAPbX perovskites present an appealing optoelectronic behavior with applications in high-efficiency solar cells. The orientation of the organic MA units may play an important role in the properties, given the degrees of freedom for internal motion of MA groups within the PbX network. The present neutron powder diffraction study reveals the dynamic features of the MA units in the hybrid perovskite series MAPb(Br Cl ) , with x=0, 0.33, 0.5, 0.67, and 1. From difference Fourier maps, the H and C/N positions were located within the PbX lattice; the refinement of the crystal structures unveiled the MA conformations. Three different orientations were found to exist as a function of the chlorine content (x) and, therefore, of the cubic unit-cell size. These conformations are stabilized by H-bond interactions with the halide ions, and were found to agree with those reported from theoretical calculations.
混合的甲基铵（MA）铅卤化物 MAPbX 钙钛矿具有吸引人的光电行为，可应用于高效太阳能电池。考虑到 MA 基团在 PbX 网络内的内部运动的自由度，有机 MA 单元的取向可能在性质中起重要作用。本中子粉末衍射研究揭示了混合钙钛矿系列 MAPb(Br Cl ) 中 MA 单元的动态特征，其中 x=0、0.33、0.5、0.67 和 1。从差分傅立叶图中，可以确定 H 和 C/N 位置在 PbX 晶格内；晶体结构的精修揭示了 MA 构象。发现随着氯含量（x）和因此，随着立方晶胞尺寸的增加，存在三种不同的取向。这些构象通过与卤化物离子的氢键相互作用稳定，并与理论计算报告的结果一致。
