Cation dynamics by 1H and 13C MAS NMR in hybrid organic-inorganic (CH3CH2NH3)2CuCl4.

Ae Ran Lim,Yong Lak Joo

doi:10.1039/c8ra06268d

Abstract

To understand the dynamics of the cation in layered perovskite-type (CH3CH2NH3)2CuCl4, the temperature-dependent chemical shifts and spin–lattice relaxation times T1ρ in the rotating frame have been measured using 1H magic angle spinning nuclear magnetic resonance (MAS NMR) and 13C cross-polarization (CP)/MAS NMR techniques. Each proton and carbon in the (CH3CH2NH3)+ cation is distinguished in MAS NMR spectra. The Bloembergen–Purcell–Pound (BPP) curves for 1H T1ρ in CH3CH2 and NH3, and for the 13C T1ρ in CH3 and CH2 are revealed to have minima at low temperatures. This implies that the curves represent the CH3 and NH3+ rotational motions. The amplitude of the cationic motion is enhanced at the C-end, that is, the N-end of the organic cation is fixed to the inorganic layer through N–H⋯Cl hydrogen bonds, and T1ρ becomes short with larger-amplitude molecular motions.

Highlights

Metal–organic hybrids, which consist of organic and inorganic components, have recently attracted much attention because these materials have many possibilities for the tailoring of their functionalities and physical properties including optical, electrical and magnetic properties by adjusting the organic and/or metal building blocks
We discuss the molecular motions for cation of Cu-based hybrid materials, where we replace Pb with nontoxic Cu metal for leadfree perovskite solar cells, and investigate their potential toward solar cell applications based on ionic dynamics of the cation in hybrid organic–inorganic (CH3CH2NH3)2CuCl4 by NMR studies
The cation dynamics in a layered perovskite-type (CH3CH2NH3)2CuCl4 were investigated as a function of temperature by 1H magic angle spinning nuclear magnetic resonance (MAS NMR) and 13C CP/MAS NMR experiments

Summary

Introduction

Metal–organic hybrids, which consist of organic and inorganic components, have recently attracted much attention because these materials have many possibilities for the tailoring of their functionalities and physical properties including optical, electrical and magnetic properties by adjusting the organic and/or metal building blocks. M represents divalent metals (M 1⁄4 Cu, Cd, .), may be described as a sequence of alternating organic–inorganic layers.[3,4,5,6] Many compounds in this family have been extensively investigated and have demonstrated successive phase transitions. This family of materials crystallizes in the layered perovskite structure, which consists of in nite, staggered layers of corner-sharing MCl6 octahedra interleaved by alkylammonium cations.[7] Because of the layered character of their structure, these crystals become appropriate substances for investigations of two-dimensional electronic systems. The chemical shi s and T1r were measured over a temperature range of 180–430 K

Experimental results

Experimental method

Conclusion