Ferroelectric field effect transistors (FeFETs) have attracted attention as next-generation devices as they can serve as a synaptic device for neuromorphic implementation and a one-transistor (1T) for achieving high integration Since the discovery of hafnium–zirconium oxide (HZO) with high ferroelectricity (even at a thickness of several nanometers) that can be fabricated by a complementary metal–oxide–semiconductor-compatible process, FeFETs have emerged as devices with great potential In this article, the basic principles of the FeFET and the design strategies for state-of-the-art FeFETs will be discussed FeFETs using Pb(ZrxTi1−x)O3, polyvinylidene fluoride, HZO, and two-dimensional materials are emphasized FeFETs, ferroelectric semiconductor field effect transistors, and metal–ferroelectric–insulator–semiconductor structures to which those materials can be applied are introduced, and their exotic performances are investigated Finally, the limitations of these devices’ current performance and the potential of these materials are presented

Ferroelectric field effect transistors: Progress and perspective

In this paper, Lead Zirconate-Titanate (PZT)/Poly-dimethylsiloxane (PDMS) based composite is fabricated and characterized for its potential application as a flexible piezoelectric material. Thin films of the composite are prepared by dispersing different volume percentage of PZT particles in cross-linked PDMS matrix. Corona poling of the films is performed to increase the piezoelectric charge constant. X-ray diffraction results indicate that poling aligns the randomly oriented ferroelectric domains in the PZT particles along the poling axis. Piezoelectric voltage response and piezoelectric charge constant values before and after the poling show the improvement in piezoelectricity due to poling. The piezoelectric charge constant, d33 and magnitude of relative permittivity of the films increase and flexibility of the films decrease with the increase of PZT particle volume percentage in the composite. Results show that for 28 v% PZT composite poled film a d33 of 78.33 pC/N was achieved with a Young’s modulus of around 10 MPa and magnitude of relative permittivity of 10. The film demonstrates effectiveness for tactile sensing by generating charges across the film proportional to the finger pressure applied on them. The easy fabrication process makes the composite a promising candidate to build flexible low cost tactile sensing devices.

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Flexible Piezoelectric 0–3 PZT-PDMS Thin Film for Tactile Sensing

From single molecule to molecular aggregation science

Dynamically tunable room‐temperature phosphorescence (RTP) organic materials have attracted considerable attention in recent years due to their great potential over a wide variety of advanced applications. However, the precise regulation of the intersystem crossing (ISC) process for efficient RTP materials with dynamically modulated properties in a rigid environment is challenging. Herein, an effective strategy for RTP material preparation with controllably regulated properties is developed via the construction of dynamic metal‐ligand coordination in a host‐guest doped system. The coordination interaction promotes ISC and phosphorescence emission of the guest, thus allowing the modulation of the photophysical properties of doped materials by changing the doping ratio and Zn2+ counterions. By taking advantage of the reversible metal‐ligand coordination interaction, the coordination‐activated, and dissociation‐deactivated RTP is dynamically manipulated. With the unique Zn2+‐responsible RTP enhancement materials, the anti‐counterfeiting applications of thermal development, and color inversion have been constructed for inkjet printing of high‐resolution patterns with high reversibility for many write/erase cycles. The results show that dynamic metal‐ligand coordination strategy is a promising approach for achieving efficient RTP materials with controllably modulated properties.

Controllable Modulation of Efficient Phosphorescence Through Dynamic Metal‐Ligand Coordination for Reversible Anti‐Counterfeiting Printing of Thermal Development

Organic room-temperature phosphorescent (RTP) materials routinely incorporate polymeric components, which usually act as non-functional or "inert" media to protect excited-state phosphors from thermal and collisional quenching, but are lesser explored for other influences. Here, we report some exemplary "active roles" of polymer matrices played in organic RTP materials, including: 1) color modulation of total delayed emissions via balancing the population ratio between thermally-activated delayed fluorescence (TADF) and RTP due to dielectric-dependent intersystem crossing; 2) altered air sensitivity of RTP materials by generating various surface morphologies such as nano-sized granules; 3) enhanced bacterial elimination for enhanced electrostatic interactions with negatively charged bio-membranes. These active roles demonstrated that the vast library of polymeric structures and functionalities can be married to organic phosphors to broaden new application horizons for RTP materials.

Functional Roles of Polymers in Room-Temperature Phosphorescent Materials: Modulation of Intersystem Crossing, Air Sensitivity and Biological Activity.

Abstract Intermolecular interactions, including attractive and repulsive interactions, play a vital role in manipulating functionalization of the materials from micro to macro dimensions. Despite great success in generation of ultralong organic phosphorescence (UOP) by suppressing non-radiative transitions through attractive interactions recently, there is still no consideration of repulsive interactions on UOP. Herein, we proposed a feasible approach by introducing carboxyl groups into organic phosphors, enabling formation of the intense repulsive interactions between the isolated molecules and the matrix in rigid environment. Our experimental results show a phosphor with a record lifetime and quantum efficiency up to 3.16 s and 50.0% simultaneously in film under ambient conditions. Considering the multiple functions of the flexible films, the potential applications in anti-counterfeiting, afterglow display and visual frequency indicators were demonstrated. This finding not only outlines a fundamental principle to achieve bright organic phosphorescence in film, but also expands the potential applications of UOP materials. 

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Ultralong organic phosphorescence from isolated molecules with repulsive interactions for multifunctional applications

X-ray-induced photodynamic therapy utilizes penetrating X-rays to activate reactive oxygen species in deep tissues for cancer treatment, which combines the advantages of photodynamic therapy and radiotherapy. Conventional therapy usually requires heavy-metal-containing inorganic scintillators and organic photosensitizers to generate singlet oxygen. Here, we report a more convenient strategy for X-ray-induced photodynamic therapy based on a class of organic phosphorescence nanoscintillators, that act in a dual capacity as scintillators and photosensitizers. The resulting low dose of 0.4 Gy and negligible adverse effects demonstrate the great potential for the treatment of deep tumours. These findings provide an optional route that leverages the optical properties of purely organic scintillators for deep-tissue photodynamic therapy. Furthermore, these organic nanoscintillators offer an opportunity to expand applications in the fields of biomaterials and nanobiotechnology. 

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Organic phosphorescent nanoscintillator for low-dose X-ray-induced photodynamic therapy

Dynamic room-temperature phosphorescence by reversible transformation of photo-induced free radicals

Room temperature phosphorescence (RTP) in metal‐free organic materials has attracted considerable attention due to its rich excited state properties, high quantum efficiency, long luminescence lifetimes, etc., showing great potential in organic optoelectronic devices, bioimaging, information anti‐counterfeiting, and so forth. The crystals have excellent rigidity and clear molecular packing patterns, which can effectively avoid non‐radiative transitions of excitons for phosphorescence enhancement. In the early stages, researchers paid great attention to the regulation of RTP performance in crystalline states. However, due to the complex preparation and poor processability of crystals, amorphous materials with RTP features have become a new research topic recently. This perspective aims to summarize the recent advances of RTP materials from crystalline to amorphous states, and analyze their molecular design strategies and luminescence mechanisms in detail. Finally, we prospect the future research directions of amorphous RTP materials. This perspective will provide a guideline for the future study of advanced RTP materials.

Yixiao He

Papers

Ultralong organic phosphorescence from isolated molecules with repulsive interactions for multifunctional applications

Organic phosphorescent nanoscintillator for low-dose X-ray-induced photodynamic therapy

Dynamic room-temperature phosphorescence by reversible transformation of photo-induced free radicals

Room‐temperature phosphorescence materials from crystalline to amorphous state

In situ polarization and dielectric property measurements of Pb(Zr0.52Ti0.48)O3 ferroelectric nanocrystals