Centimeter-Sized Single Crystals of Dion-Jacobson Phase Lead-Free Double Perovskite for Efficient X-ray Detection

2D Dion–Jacobson (DJ) phase hybrid perovskites have shown great promise in the photoelectronic field owing to their outstanding optoelectronic performance and superior structural rigidity. However, DJ phase lead-free double perovskites are still a virgin land with direct X-ray detection. Herein, we have designed and synthesized a new DJ phase lead-free layered double perovskite of (HIS)₂AgSbBr₈ ( 1 , HIS²⁺ = histammonium). Centimeter-sized (18 × 10 × 5 mm³) single crystals of 1 are successfully grown via the temperature cooling technique, exhibiting remarkable semiconductive characteristics such as a high resistivity (2.2 × 10¹¹ Ω cm), a low trap state density (3.56 × 10¹⁰ cm⁻³), and a large mobility-lifetime product (1.72 × 10⁻³ cm² V⁻¹). Strikingly, its single-crystal-based X-ray detector shows a high sensitivity of 223 µC Gy⁻¹_air cm⁻² under 33.3 V mm⁻¹, a low detection limit (84.2 nGy_airs⁻¹) and superior anti-fatigue. As far as we know, we firstly demonstrates the potential of 2D DJ phase lead-free hybrid double perovskite in X-ray detection, showing excellent photoelectric response and operational stability. This work will pave a promising pathway to the innovative application of hybrid perovskites for eco-friendly and efficient X-ray detection.     

Flexible Porous Organic Polymer Membranes for Protonic Field-Effect Transistors

Artificial transistors represent an ideal means for meeting the requirements in interfacing with biological systems. It is pivotal to develop new proton-conductive materials for the transduction between biochemical events and electronic signals. Herein, the first demonstration of a porous organic polymer membrane (POPM) as a proton-conductive material for protonic field-effect transistors is presented. The POPM is readily prepared through a thiourea-formation condensation reaction. Under hydrated conditions and at room temperature, the POPM delivers a proton mobility of 5.7 × 10⁻³ cm² V⁻¹ s⁻¹; the charge carrier densities are successfully modulated from 4.3 × 10¹⁷ to 14.1 × 10¹⁷ cm⁻³ by the gate voltage. This study provides a type of promising modular proton-conductive materials for bioelectronics application.     

Relieving the Photosensitivity of Organic Field-Effect Transistors

It is generally believed that the photoresponse behavior of organic field-effect transistors (OFETs) reflects the intrinsic property of organic semiconductors. However, this photoresponse hinders the application of OFETs in transparent displays as driven circuits due to the current instability resulting from the threshold voltage shift under light illumination. It is necessary to relieve the photosensitivity of OFETs to keep the devices stable. 2,6-diphenyl anthracene thin-film and single-crystal OFETs are fabricated on different substrates, and it is found that the degree of molecular order in the conducting channels and the defects at the dielectric/semiconductor interface play important roles in determining the phototransistor performance. When highly ordered single-crystal OFETs are fabricated on polymeric substrates with low defects, the photosensitivity (P) decreases by more than 10⁵ times and the threshold voltage shift (ΔV_T) is almost eliminated compared with the corresponding thin-film OFETs. This phenomenon is further verified by using another three organic semiconductors for similar characterizations. The decreased P and ΔV_T of OFETs ensure a good current stability for OFETs to drive organic light-emitting diodes efficiently, which is essential to the application of OFETs in flexible and transparent displays.     

Bioinspired Multifunctional Organic Transistors Based on Natural Chlorophyll/Organic Semiconductors

Inspired by the photosynthesis process of natural plants, multifunctional transistors based on natural biomaterial chlorophyll and organic semiconductors (OSCs) are reported. Functions as photodetectors (PDs) and light-stimulated synaptic transistors (LSSTs) can be switched by gate voltage. As PDs, the devices exhibit ultrahigh photoresponsivity up to 2 × 10⁶ A W⁻¹, detectivity of 6 × 10¹⁵ Jones, and I_photo/I_dark ratio of 2.7 × 10⁶, which make them among the best reported organic PDs. As LSSTs, important synaptic functions similar to biological synapses are demonstrated, together with a dynamic learning and forgetting process and image-processing function. Significantly, benefiting from the ultrahigh photosensitivity of chlorophyll, the lowest operating voltage and energy consumption of the LSSTs can be 10⁻⁵ V and 0.25 fJ, respectively. The devices also exhibit high flexibility and long-term air stability. This work provides a new guide for developing organic electronics based on natural biomaterials.     

含氟有机场效应晶体管材料的研究进展

在空气中稳定的n型有机半导体材料是当前有机场效应晶体管(OFET)研究的重要方向.分子中引入氟取代基和三氟甲基/全氟烷基可能会将有机半导体材料从p型转变成n型,同时还可提高有机半导体材料的稳定性.从分子结构的角度出发介绍了含氟类有机半导体材料的最新进展及其在场效应晶体管中的应用,并进一步提出了该领域的研究前景.     

N‐Type 2D Organic Single Crystals for High‐Performance Organic Field‐Effect Transistors and Near‐Infrared Phototransistors

Organic field‐effect transistors and near‐infrared (NIR) organic phototransistors (OPTs) have attracted world's attention in many fields in the past decades. In general, the sensitivity, distinguishing the signal from noise, is the key parameter to evaluate the performance of NIR OPTs, which is decided by responsivity and dark current. 2D single crystal films of organic semiconductors (2DCOS) are promising functional materials due to their long‐range order in spite of only few molecular layers. Herein, for the first time, air‐stable 2DCOS of n‐type organic semiconductors (a furan‐thiophene quinoidal compound, TFT‐CN) with strong absorbance around 830 nm, by the facile drop‐casting method on the surface of water are successfully prepared. Almost millimeter‐sized TFT‐CN 2DCOS are obtained and their thickness is below 5 nm. A competitive field‐effect electron mobility (1.36 cm² V^?1 s^?1) and high on/off ratio (up to 10⁸) are obtained in air. Impressively, the ultrasensitive NIR phototransistors operating at the off‐state exhibit a very low dark current of ≈0.3 pA and an ultrahigh detectivity (D*) exceeding 6 × 10¹⁴ Jones because the devices can operate in full depletion at the off‐state, superior to the majority of the reported organic‐based NIR phototransistors.     

Organic Semiconductor Growth and Morphology Considerations for Organic Thin‐Film Transistors

Analogous to conventional inorganic semiconductors, the performance of organic semiconductors is directly related to their molecular packing, crystallinity, growth mode, and purity. In order to achieve the best possible performance, it is critical to understand how organic semiconductors nucleate and grow. Clever use of surface and dielectric modification chemistry can allow one to control the growth and morphology, which greatly influence the electrical properties of the organic transistor. In this Review, the nucleation and growth of organic semiconductors on dielectric surfaces is addressed. The first part of the Review concentrates on small‐molecule organic semiconductors. The role of deposition conditions on film formation is described. The modification of the dielectric interface using polymers or self‐assembled mono­layers and their effect on organic‐semiconductor growth and performance is also discussed. The goal of this Review is primarily to discuss the thin‐film formation of organic semiconducting species. The patterning of single crystals is discussed, while their nucleation and growth has been described elsewhere (see the Review by Liu et. al). 1 The second part of the Review focuses on polymeric semiconductors. The dependence of physico‐chemical properties, such as chain length (i.e., molecular weight) of the constituting macromolecule, and the influence of small molecular species on, e.g., melting temperature, as well as routes to induce order in such macromolecules, are described.     

Precise Patterning of Organic Semiconductor Crystals for Integrated Device Applications

Development of high‐performance organic electronic and optoelectronic devices relies on high‐quality semiconducting crystals that have outstanding charge transport properties and long exciton diffusion length and lifetime. To achieve integrated device applications, it is a prerequisite to precisely locate the organic semiconductor crystals (OSCCs) to form a specifically patterned structure. Well‐patterned OSCCs can not only reduce leakage current and cross‐talk between neighboring devices, but also facilely integrate with other device elements and their corresponding interconnects. In this Review, general strategies for the patterning of OSCCs are summarized, and the advantages and limitations of different patterning methods are discussed. Discussion is focused on an advanced strategy for the high‐resolution and wafer‐scale patterning of OSCC by a surface microstructure‐assisted patterning method. Furthermore, the recent progress on OSCC pattern‐based integrated circuities is highlighted. Finally, the research challenges and directions of this young field are also presented.     

When Flexible Organic Field-Effect Transistors Meet Biomimetics: A Prospective View of the Internet of Things

The emergence of flexible organic electronics that span the fields of physics and biomimetics creates the possibility for increasingly simple and intelligent products for use in everyday life. Organic field-effect transistors (OFETs), with their inherent flexibility, light weight, and biocompatibility, have shown great promise in the field of biomimicry. By applying such biomimetic OFETs for the internet of things (IoT) makes it possible to imagine novel products and use cases for the future. Recent advances in flexible OFETs and their applications in biomimetic systems are reviewed. Strategies to achieve flexible OFETs are individually discussed and recent progress in biomimetic sensory systems and nervous systems is reviewed in detail. OFETs are revealed to be one of the best systems for mimicking sensory and nervous systems. Additionally, a brief discussion of information storage based on OFETs is presented. Finally, a personal view of the utilization of biomimetic OFETs in the IoT and future challenges in this research area are provided.     

Impact of Narrowing Density of States in Semiconducting Polymers on Performance of Organic Field-Effect Transistors

To improve the performance of organic field-effect transistors (OFETs) employing π-conjugated polymers, a basic understanding of the relationships between the material properties and device characteristics is crucial. Although the density of states (DOS) distribution is one of the essential material properties of semiconducting polymers, insights into how the DOS shape affects the mobility (µ), subthreshold swing (S), and contact resistance (R_C) in OFETs remain lacking. In this study, by combining sensitive DOS measurements and multilayered OFET structures, it is experimentally demonstrated that narrower DOS widths in the polymer channels lead to higher µ, smaller S, and lower R_C. By contrast, variation of the DOS in the bulk layer does not affect the performance. These results demonstrate a direct relationship between the polymer properties and OFET performance and highlight the importance of controlling the DOS width in π-conjugated polymers.     

Meniscus-Guided Deposition of Organic Semiconductor Thin Films: Materials,Mechanism, and Application in Organic Field-Effect Transistors

Solution-processable organic semiconductors are one of the promising materials for the next generation of organic electronic products, which call for high-performance materials and mature processing technologies. Among many solution processing methods, meniscus-guided coating (MGC) techniques have the advantages of large-area, low-cost, adjustable film aggregation, and good compatibility with the roll-to-roll process, showing good research results in the preparation of high-performance organic field-effect transistors. In this review, the types of MGC techniques are first listed and the relevant mechanisms (wetting mechanism, fluid mechanism, and deposition mechanism) are introduced. The MGC processes are focused and the effect of the key coating parameters on the thin film morphology and performance with examples is illustrated. Then, the performance of transistors based on small molecule semiconductors and polymer semiconductor thin films prepared by various MGC techniques is summarized. In the third section, various recent thin film morphology control strategies combined with the MGCs are introduced. Finally, the advanced progress of large-area transistor arrays and the challenges for roll-to-roll processes are presented using MGCs. Nowadays, the application of MGCs is still in the exploration stage, its mechanism is still unclear, and the precise control of film deposition still needs experience accumulation.     

Ultrafast Self‐Limited Growth of Strictly Monolayer WSe2 Crystals

The controllable synthesis of uniform tungsten diselenide (WSe₂) is crucial for its emerging applications due to the high sensitivity of its extraordinary physicochemical properties to its layer numbers. However, undesirable multilayer regions inevitably form during the fabrication of WSe₂ via the traditional chemical vapor deposition process resulted from the lack of significantly energetically favorable competition between layer accumulation and size expansion. This work innovatively introduces Cu to occupy the hexagonal site positioned at the center of the six membered ring of the WSe₂ surface, thus filtrates the undesired reaction path through precisely thermodynamical control and achieves self‐limited growth WSe₂ crystals. The as‐obtained WSe₂ crystals are characterized as strictly single‐layer over the entire wafer. Furthermore, the strictly self‐limited growth behavior can achieve the “win–win” cooperation with the synthesis efficiency. The fastest growth (≈15 times of the growth rate in the previous work) of strictly monolayer WSe₂ crystals thus far is realized due to the high‐efficiency simultaneous selenization process. The as‐proposed ultrafast Cu‐assisted self‐limited growth method opens a new avenue to fabricate strictly monolayer transition metal dichalcogenides crystals and further promotes their practical applications in the future industrial applications.     

General Spatial Confinement Recrystallization Method for Rapid Preparation of Thickness-Controllable and Uniform Organic Semiconductor Single Crystals

Organic semiconductor single crystals (OSSCs) are ideal materials for studying the intrinsic properties of organic semiconductors (OSCs) and constructing high-performance organic field-effect transistors (OFETs). However, there is no general method to rapidly prepare thickness-controllable and uniform single crystals for various OSCs. Here, inspired by the recrystallization (a spontaneous morphological instability phenomenon) of polycrystalline films, a spatial confinement recrystallization (SCR) method is developed to rapidly (even at several second timescales) grow thickness-controllable and uniform OSSCs in a well-controlled way by applying longitudinal pressure to tailor the growth direction of grains in OSCs polycrystalline films. The relationship between growth parameters including the growth time, temperature, longitudinal pressure, and thickness is comprehensively investigated. Remarkably, this method is applicable for various OSCs including insoluble and soluble small molecules and polymers, and can realize the high-quality crystal array growth. The corresponding 50 dinaphtho[2,3-b:2″,3″-f]thieno[3,2-b]thiophene (DNTT) single crystals coplanar OFETs prepared by the same batch have the mobility of 4.1 ± 0.4 cm² V⁻¹ s⁻¹, showing excellent uniformity. The overall performance of the method is superior to the reported methods in term of growth rate, generality, thickness controllability, and uniformity, indicating its broad application prospects in organic electronic and optoelectronic devices.