Precise Design of Molecular Ferroelectrics with High T_C and Tunable Band Gap by Molecular Modification

Abstract

Molecular ferroelectric materials are widely applied in piezoelectric converters, non-volatile memorizers, and photovoltaic devices due to their advantages of adjustable structure, lightweight, easy processing, and environmental friendliness. However, designing multifunctional molecular ferroelectrics with excellent properties has always been a great challenge. Herein, a multiaxial molecular ferroelectric is successfully designed by modifying the quasi-spherical cation dabco with CuBr 2 to obtain halogenated [Bretdabco]CuBr 4 (Bretdabco = N-bromoethyl-N′diazabicyclo [2.2.2]octane), which crystallizes in polar point groups (C 6 ). Typical ferroelectric behaviors featured by the P−E hysteresis loop and switched ferroelectric domain are exhibited. Notably, the molecular ferroelectric shows a high T C of 460 K, which is rare in the field and could greatly expand the application range of this material. In addition, the band gap is adjustable through the regulation of halogen. Both the UV absorption spectra and theoretical calculations indicate that the molecular ferroelectrics belong to a direct band gap (2.14 eV) semiconductor. This tunable and narrow band gap semiconductor molecular ferroelectric material with high T C can be utilized more effectively in the study of optoelectronics and sensors, including piezoelectric energy harvesters. This research may provide a promising approach for the development of multiaxial molecular ferroelectrics with a tiny band gap and high T C .

Comprehensively understanding the distinct properties of crystal structure, phase transition and dielectrics in [M(crown)n]ReO4 (M+ = Na+, K+, NH4+; crown = 15-crown-5, 18-crown-6; n = 1 or 2)

“…These transitions often result in significant alterations in crystal structures and various physical properties such as thermal, optical, dielectric, and magnetic characteristics. 1–11 Due to their broad applications in fields such as data storage, signal processing, and switchable dielectric devices, phase transition materials (PTMs) have garnered considerable interest in recent years. 12–18 Consequently, the design and controllable synthesis of novel PTMs remain important focal points in the realms of chemistry and materials science.…”

Crown‐Ether‐Ring Size Dependent Crystal Structures, Phase Transition and Dielectric Properties of [M(crown)]BF4⋅xH2O (M+=Na+, K+; crown=15‐crown‐5, 18‐crown‐6; x=0 or 1)

“…The significant variations in crystal structure and physical properties, including the thermal, optical, electrical, dielectric, ferroelectric and magnetic properties, are usually accompanied the phase transition. [1][2][3][4][5][6][7][8][9] The combination of these unique characteristics has resulted in the exploration of numerous applications, such as information storage, sensing, and other promising domains, [10][11][12][13] making solid-solid phase transition materials a subject of keen interest among researchers.…”

Dehydration Induced a Structural Transformation into a One-Dimensional Hybrid Perovskite with Second Harmonic Generation and Dual Dielectric Switching

“…The possibility of generating novel functional materials with wonderful electronic and optical properties gives a substantial impetus for the research of hybrid organic–inorganic halide perovskites. − Given the structural diversity and tunability, these kinds of materials have garnered considerable attention in recent years due to prospective applications in solar cells, detectors, scintillators, etc. − Also, a number of hybrid halide perovskites with stimuli-responsive structural transformation have been considered promising candidates and have promoted the prosperous development of intelligent switchable materials. − This crystalline state transformation mainly involves changes in the arrangement, orientation, or size of atoms, molecules, or components within the system, leading to noticeable changes in the properties of hybrid halide perovskites, such as conductivity, magnetism, optical properties, and so on. − …”