Characterization on Lead-Free Hybrid Perovskite [NH3(CH2)5NH3]CuCl4: Thermodynamic Properties and Molecular Dynamics.

It is essential to develop novel zero- and two-dimensional hybrid perovskites to facilitate the development of eco-friendly solar cells. In this study, we investigated the structure and dynamics of [NH3(CH2)5NH3]CuCl4 via various characterization techniques. Nuclear magnetic resonance (NMR) results indicated that the crystallographic environments of 1H in NH3 and 13C on C3, located close to NH3 at both ends of the cation, were changed, indicating a large structural change of CuCl6 connected to N-H···Cl. The thermal properties and structural dynamics of the [NH3(CH2)nNH3] cation in [NH3(CH2)nNH3]CuCl4 (n = 2, 3, 4, and 5) crystals were compared using thermogravimetric analysis (TGA) and NMR results for the methylene chain. The 1H and 13C spin-lattice relaxation times (T1ρ) exhibited similar trends upon the variation of the methylene chain length, with n = 2 exhibiting shorter T1ρ values than n = 3, 4, and 5. The difference in T1ρ values was related to the length of the cation, and the shorter chain length (n = 2) exhibited a shorter T1ρ owing to the one closest to the paramagnetic Cu2+ ions.