A Sn-Based Hybrid Ferroelastic Semiconductor with High-Temperature Dielectric Switching

Organic-inorganic halide hybrids have been extensively developed and used in optoelectronic devices because of their superior performance such as ease of assembly, flexible structural tunability, and excellent optoelectronic properties. Ferroelastic strain might be used to modulate and control photoelectric properties such as photovoltaic voltage, while organic-inorganic hybrid ferroelastic semiconductors remain relatively unexplored. Herein, we successfully design a new Sn-base, lead-free hybrid ferroelastic semiconductor, [TPMA]2[SnCl6] (TPMA = benzyl trimethylammonium). It undergoes a high-temperature -3mF-1-type ferroelastic phase transition at 408 K, and intriguingly, its ferroelastic domains can be simultaneously switched under the stimulation of external heat and stress. The ferroelastic phase transition might be derived from the order-disorder transition of organic cations during heating and cooling. Moreover, [TPMA]2[SnCl6] also demonstrates a high-temperature dielectric switching property around 408 K, which has good stability and reproducibility. With those benefits, [TPMA]2[SnCl6] shows great potential in applications such as energy storage devices, optoelectronic devices, shape memory, intelligent switches, and so on.

Exceptional structural phase transition near room temperature in an organic-inorganic hybrid ferroelectric

An organic-inorganic hybrid ferroelectric, (C6H5CH2CH2NH3)2[HgI4], undergoes an exceptional structural phase transition near room temperature, triggered by a flip of half the organic cations and an order-disorder transition of the inorganic anions, and may be regarded as a displacive-type ferroelectric. This finding provides a new structural phase transition mechanism in molecule-based ferroelectrics.

Excellent Switchable Properties, Broad-Band Emission, Ferroelectricity, and High Tc in a Two-Dimensional Hybrid Perovskite: (4,4-DCA)2PbBr4 Exploited by H/F Substitution

Switchable materials have gained significant attention due to their potential applications in data storage, sensors, and switching devices. Two-dimensional (2D) hybrid perovskites have demonstrated promising prospects for designing switchable materials, where the dynamic motion of the organic components coupled with the distortion of the inorganic framework provides the driving force for triggering multifunctional switchable properties. Herein, through the H/F substitution strategy, we report a polar 2D hybrid lead-based perovskite, (4,4-DCA)₂PbBr₄ (4,4-DCA = 4,4-difluorocyclohexylammonium) (1), which exhibits dual-stable behavior in a dielectric and second harmonic generation (SHG) response during the reversible phase transition process near the high Curie temperature T_c ∼ 409 K. The phase transition temperature is significantly increased by 41 K compared to the corresponding non-fluorinated (CHA)₂PbBr₄ (CHA = cyclohexylammonium). Remarkably, the material shows rare broad-band yellow emission under UV excitation, attributed to the induction of self-trapped exciton emission by the distortion of the [PbBr_6]^4- octahedra, as confirmed by the first-principles analysis. 1 also exhibited ferroelectricity with a saturation polarization value and a small coercive field. This study provides a new insight into the modification of multifunctional switchable materials through the H/F substitution strategy.

High-Tc 1D Phase-Transition Semiconductor Photoluminescent Material with Broadband Emission

One dimensional (1D) organic-inorganic halide hybrid perovskites have the advantages of excellent organic cation modifiability and diversity of inorganic framework structures, which cannot be ignored in the development of multi-functional phase-transition materials in photoelectric and photovoltaic devices. Here, we have successfully modified and synthesized an organic-inorganic hybrid perovskite photoelectric multifunctional phase-transition material: [C₇ H₁₃ ONCH₂ F]⋅PbBr₃ (1). The synergistic effect of the order double disorder transition of organic cations and the change of the degree of distortion of the inorganic framework leads to its high temperature reversible phase-transition point of T_c =374 K/346 K and its ultra-low loss high-quality dielectric switch response. Through in-depth research and calculation, compound 1 also has excellent semiconductor characteristics with a band gap of 3.06 eV and the photoluminescence characteristics of self-trapped exciton (STE) broadband emission. Undoubtedly, this modification strategy provides a new choice for the research field of organic-inorganic hybrid perovskite reversible phase-transition photoelectric multifunctional materials with rich coupling properties.

Dual-channel control of ferroelastic domains in a host–guest inclusion compound

By replacing [PF6]− with the larger [TFSA]−, the phase transition temperature is increased from 305 K to 342 K in a host–guest inclusion ferroelastic crystal, [(3,4-DFA)(18-crown-6)][TFSA], which can realize dual-channel (thermal and stress) control of ferroelastic domains.