Wan-Ying Zhang

Rapid dielectric bistable switching materials without a time/temperature responsive blind area in the linarite-like type molecular large-size single crystals

Molecular bistable switches (electrical switch “ON” and “OFF” bistable states) are a class of highly desirable intelligent materials due to their sensitive switchable physical and/or chemical response, easy and environmentally-friendly processing, light weight and mechanical flexibility. In particular, those switches with a rapid response are rarely reported. In this work, it is found that the supramolecular large-size crystal [H2DABCO][CdCl2(SO4)] (1) possesses a superior rapid switching performance for disordered oxygen atoms and swaying DABCO cations, displaying remarkably high sensitive and rapid dielectric bistable switching between high (switch ON) and low (switch OFF) dielectric states. This electrical switch reveals fatigue resistance and remarkable switching reversibility. Owing to obvious disordered oxygen atoms and swaying DABCO cations compared with the compound [H2DABCO][CdBr2(SO4)] (2), the permittivity of 1, jumping from 4 to ∼10, exhibits an almost vertical gradient in a relatively wide frequency range (responding time/temperature t = 0, which means that there is no responsive blind area), indicating a relatively more rapid electrical response compared with other reported molecular compounds. Therefore, compound 1 can be an excellent stimuli-responsive electrical switch, and its application in molecular/flexible electronic devices will have a profound significance.

Red-light emission and dielectric reversible duple opto-electronic switches in a hybrid multifunctional material: (2-methylimidazolium)MnCl3(H2O)

Optoelectronic duple-functional organic–inorganic materials are capable of imparting multiple desirable properties in one device cell for ultra-encrypted and highly integrated data storage, communication, signal processing and sensing. However, multifunctional switchable materials, especially those with bistable photoluminescent/dielectric switching properties, are rarely reported. The exceptional compatibility of optoelectronic duple switching is much superior to the current predominant multifunctional devices. Here, a new organic–inorganic hybrid compound, (2-methylimidazolium)MnCl3(H2O) (1), was found to behave as a potential optical–electrical duple bistable switch (with both optical and electrical switching “ON” and “OFF”), which undergoes a reversible order–disorder structural phase transition, then triggering an extraordinary photoluminescent/dielectric transformation. This compound provides a concrete example of optoelectronic multifunctional switching materials and may promote the development of desirable devices.

Fast and slow integrated single-molecule dual dielectric switch based on a crystal/flexible thin film

Smart plastic crystals/films based on organic–inorganic hybrid materials are rarely reported in the form of highly-integrated intelligent controllable dielectric switches (switching between ON/OFF or “1”/“0”), especially tunable switches with dual ON/OFF effects that are integrated in a single molecule. Herein, two superior plastic crystals, [C6H15ClNO]2[MCl4] (M = Cd for 1, Mn for 2), which are able to exhibit tunable and dual dielectric switching characteristics between three stages triggered by temperature (LTP, RTP and HTP) in a single molecule, were successfully synthesized and prepared as ultraflexible and monodirectional thin films. Such excellent features lay the foundation for their applications in temperature-adjustable multifunctional single-molecule sensors and memory devices. Specifically, through control of the operating temperature, the fast dielectric switch (high temperature phase transition stage) and the slow/delayed dielectric switch (low temperature phase transition stage) can be integrated in a single molecular device cell. As well as the superior stability/fatigue resistance of the crystals, the facile/environmentally-friendly fabrication of the thin films makes 1 and 2 excellent candidates for single-molecule intelligent devices and highly-integrated dual-switching devices in the modern electronic information industry.

Lead-free Single-molecule Switching Material with Electric, Optical, Thermal Triple Controllable Multifunction Based on Perovskite-like Crystal and Flexible Thin Film

With the flourishing development of star molecule (CH3NH3)PbI3, organic-inorganic perovskites with multifunction and flexibility have become a worldwide focus. However, the controllable photoelectric switchable material (especially electric, optical, thermal multifunctional switches) still face great challenges, and most of them are ceramic and toxic lead-based series. Herein a lead-free perovskite-like crystal and flexible thin film, ImMC (ImMC = (HIm)6∙[MnCl4∙MnCl6]) (1), with many advantages over inorganic ceramics and lead-based perovskites, performs ideal optical and dielectric duple switching properties simultaneously. The order-disordered HIm (Im = imidazole) cations of α-type occupy two lattice sites corresponding to “Switch-ON/0” and “Switch-OFF/1” states, respectively. Interestingly, the optical and dielectric “ON/OFF or 0/1” switches can be integrated into one single-molecule single/duple channel module with high signal-noise ratio, in which the “ON/OFF” response can be precisely controlled by temperature or/and light wavelength signal to realize automatically multiple switching. In brief, the lead-free multifunctional switch opens up a brand new route and shows the mark of its real genius as a highly desirable material for its advanced applications in highly integrated circuit and ultrahigh-encrypted storage in flexible photoelectric devices.

Multifunctional Material with Efficient Optoelectronic Integrated Molecular Switches Based on a Flexible Thin Film/Crystal

Switchable materials, due to their potential applications in the fields of sensors, photonic devices, digital processing, etc., have been developed drastically. However, they still face great challenges in effectively inducing multiple molecular switching. Herein organic-inorganic hybrid compounds, an emerging class of hydrosoluble optoelectronic-active materials, welcome a new member with smart unique optical/electrical (fluorescence/dielectric) dual switches (switching ON/OFF), that is, [C5H13NBr][Cd3Br7] (1) in the form of both a bulk crystal and an ultraflexible monodirectional thin film, which simultaneously exhibits fast dielectric/fluorescent dual switching triggered by an optical/thermal/electric signal with a high signal-to-noise ratio of 35 (the highest one in the known optical/dielectric dual molecular switches). Additionally, the exceptional stability/fatigue resistance as well as the fantastic extensibility/compactness of thin films (more than 10000 times folding over 90°), makes 1 an ideal candidate for single-molecule intelligent wearable devices and seamlessly integrated optoelectronic multiswitchable devices. This opens up a new route toward advanced light/electric high-performance switches/memories based on organic-inorganic hybrid compounds.

Heat-sensitive structural phase transitions of hybrid halide perovskite with double dielectric ON/OFF switches

A research domain on the ferroelectric and dielectric switching characteristics of hybrid perovskites has been opened because of their excellent physical/chemical features upon exposure to CH3NH3PbI3. To promote the development of applications, designing novel systems with superior performances is crucial. Here, we found [(CH3)3NOH][CdCl3], a hybrid perovskite, could be considered to be a multi-stable switchable dielectric material at high temperatures. The temperature-dependent crystal structure and differential scanning calorimetry studies revealed that it underwent three phases at low, intermediate and high temperature. Moreover, the origin of the phase transitions could be ascribed mainly to the order–disorder of trimethylamine N-oxide cations. When the temperature increased from low to high, [(CH3)3NOH][CdCl3] displayed a sequential switching effect with the dynamic change of organic cations. These findings provide an excellent model to develop molecule-based compounds as multi-switch materials.

Switchable Dielectric Phase Transition Triggered by Pendulum-Like Motion in an Ionic Co-crystal

Molecular-based ionic co-crystals, which have the merits of low-cost/easy fabrication processes and flexible structure and functionality, have already exhibited tremendous potential in molecular memory switches and other electric devices. However, dipole (ON/OFF switching) triggering is a huge challenge. Here, we introduce a pendulum-like dynamic strategy to induce the order-disorder transition of a co-crystal [C5 H7 N3 Cl]3 [Sb2 Br9 ] (compound 1). Here, the anion and cation act as a stator and a pendulum-like rotor (the source of the dielectric switch), respectively. The temperature-dependent dielectric and differential scanning calorimetry (DSC) analyses reveal that 1 undergoes a reversible phase transition, which stems from the order-disorder transition of the cations. The thermal ON/OFF switchable motions make 1 a promising candidate to promote the development of bulk crystals as artificial intelligent dielectric materials. In addition, the pendulum-like molecular dynamics and distinct arrangements of two coexisting ions with a notable offset effect promotes/hinders dipolar reorientation after dielectric transition and provides a rarely observed but fairly useful and feasible strategy for understanding and modulating the dipole motion in crystalline electrically polarizable materials.