[C5H12N]CdCl3: an ABX3 perovskite-type semiconducting switchable dielectric phase transition material

Abstract

A new organic–inorganic ABX₃ perovskite-type semiconducting hybrid, N-methylpyrrolidinium trichlorocadmate (MPCC), has been synthesized. It is found that MPCC exhibits semiconducting behaviour with an optical bandgap of ∼4.65 eV, as well as remarkable dielectric switching properties. It displays a structural phase transition (SPT) at T_c = 254 K, being confirmed by DSC and specific heat measurements. Dielectric measurements display distinct step-like anomalies around T_c, suggesting MPCC as a switchable dielectric material. Variable temperature single-crystal X-ray diffraction reveals that symmetry-breaking occurs from Pnma (at 280 K, >T_c) to P2₁/c (at 230 K, <T_c), which is attributed to the ordering of the disordered N-methylpyrrolidinium (MP) cation. The most distinct difference between its low- and high-temperature structures is the order–disorder dynamics of the MP cation, which mainly contribute to the SPT and switchable dielectric activities of MPCC. This finding paves a new way for designing multi-featured ABX₃-type SPT hybrids by choosing disordered cationic moieties.