Thermal, ferroelastic, and structural properties near phase transitions of organic–inorganic perovskite type [NH3(CH2)3NH3]CdBr4 crystals

Abstract

Hybrid perovskites have potential applications in several electrochemical devices such as supercapacitors, batteries, and fuel cells. Therefore, we studied the thermal behavior and structural dynamics of organic–inorganic hybrid perovskite [(NH₃)(CH₂)₃(NH₃)]CdBr₄ crystals near phase transition temperatures, T_C2 (=328 K) and T_C1 (=363 K), which are correlated to the structural dynamics of cations and anions. The structural geometry and molecular dynamics with emphasis on the role of the [(NH₃)(CH₂)₃(NH₃)] cation and CdBr₆ anion were discussed in terms of MAS ¹H NMR, MAS ¹³C NMR, ¹⁴N NMR, and ¹¹³Cd NMR as a function of the temperature. The environments surrounding ¹H, ¹³C, ¹⁴N, and ¹¹³Cd are investigated near T_C1 and T_C2 using these results. Spin–lattice relaxation times T_1ρ were discussed in terms of the change in temperature. The discontinuous changes of ¹H T_1ρ and ¹³C T_1ρ near T_C1 are consistent with the change of the lattice constant. Shorter T_1ρ values at high temperature indicate that ¹H and ¹³C in the organic chains are more flexible at these temperatures. Based on these results, the physicochemical properties of the cation and anion during the III–II–I phase transitions were discussed. This study was conducted to improve the relatively weak thermal stability compared to the high efficiency for a variety of applications.