The first example for thienoacene derivatives with selective growth of different crystal polymorphs is simply achieved by solution-phase self-assembly. Compared with platelet-shaped α-phase crystals, organic field-effect transistors (OFETs) based on microribbon-shaped β-phase crystals show a hole mobility up to 18.9 cm(2) V(-1) s(-1), which is one of the highest values for p-type organic semiconductors measured under ambient conditions.
Obvious differentiated response of organic phototransistors (OPTs) to the lights with different wavelengths is a challenge but a prerequisite for wavelength‐selective applications. In this manuscript, highly UV‐sensitive OPTs are fabricated based on benzo[1,2‐ b :4,5‐ b′ ]dithiophene dimers (BBDT, BBDTE, and BBDTY). The BBDTE‐based organic single‐crystal transistors (OSCTs), which show carrier mobility up to 1.62 cm 2 V −1 s −1 , exhibit a maximum photoresponsivity up to 9821 A W −1 and a maximum photosensitivity up to 10 5 towards UV light (37 μW cm −2 ), and the photosensitivity observed within tested light intensity range is unexpectedly stable. The BBDTY‐based OPTs also exhibit differentiated response between UV and visible lights, even with thin‐film state of organic semiconductor, and the highest photoresponsivity and photosensitivity to UV light reached 9336 A W −1 and 4429, respectively. This selective and highly sensitive performance enables unsaturated bond‐linked benzo[1,2‐ b :4,5‐ b′ ]dithiophene dimers promising candidates for UV detectors.
Flexible electronics have attracted considerable attention recently given their potential to revolutionize human lives. High-performance organic crystalline materials (OCMs) are considered strong candidates for next-generation flexible electronics such as displays, image sensors, and artificial skin. They not only have great advantages in terms of flexibility, molecular diversity, low-cost, solution processability, and inherent compatibility with flexible substrates, but also show less grain boundaries with minimal defects, ensuring excellent and uniform electronic characteristics. Meanwhile, OCMs also serve as a powerful tool to probe the intrinsic electronic and mechanical properties of organics and reveal the flexible device physics for further guidance for flexible materials and device design. While the past decades have witnessed huge advances in OCM-based flexible electronics, this review is intended to provide a timely overview of this fascinating field. First, the crystal packing, charge transport, and assembly protocols of OCMs are introduced. State-of-the-art construction strategies for aligned/patterned OCM on/into flexible substrates are then discussed in detail. Following this, advanced OCM-based flexible devices and their potential applications are highlighted. Finally, future directions and opportunities for this field are proposed, in the hope of providing guidance for future research.
A comprehensive summary and deep insights into the synthesis, characterization and multi-functional device applications of n-type and ambipolar organic semiconductors are provided in this study.
Efficient charge transport in organic semiconductors is essential for construction of high performance optoelectronic devices. Herein, for the first time, we demonstrate that poly(amic acid) (PAA), a facilely deposited and annealing-free dielectric layer, can tailor the growth of organic semiconductor films with large area and high crystallinity toward efficient charge transport and high mobility in their thin film transistors. Pentacene is used as a model system to demonstrate the concept with mobility up to 30.6 cm2 V–1 s–1, comparable to its high quality single crystal devices. The structure of PAA has corrugations with OH groups pointing out of the surface, and the presence of an amide bond further allows adjacent polymer strands to interact via hydrogen bonding, leading to a self-rippled surface perpendicular to the corrugation. On the other hand, the strong polar groups (−COOH/–CONH) of PAA could provide repulsive forces between PAA and pentacene, which results in the vertical orientation of pentacene on the dielectric surface. Indeed, in comparison with its imidized counterpart polyimide (PI), PAA dielectric significantly enhances the film crystallinity, drastically increases the domain size, and decreases the interface trap density, giving rise to superior device performance with high mobility. This concept can be extended to more organic semiconducting systems, e.g., 2,6-diphenylanthracene (DPA), tetracene, copper phthalocyanine (CuPc), and copper hexadecafluorophthalocyanine (F16CuPc), demonstrating the general applicability. The results show the importance of combining surface nanogrooves with the strong polarity in orienting the molecular arrangement for high crystallinity toward efficient charge transport in organic semiconductors.
Recently, organic semiconductors have received remarkable attention in both of fundamental studies and application science. Nevertheless, charge carrier mobilities of organic field-effect transistors (OFETs) are generally very low due to the poor molecular packing and lack of macroscopic order in solid state. So, it is crucial for controlling molecular orders/orientation to understand the charge carrier transport mechanism as well as fabricate high performance OFETs. In this paper, we will highlight the representative and effective processing approaches for ordering molecular orders/orientation in organic thin films, in order to valuable guideline and perspectives for high organic thin film transistors.
Abstract Traditionally, it is believed that three‐dimensional transport networks are preferable to those of lower dimensions. We demonstrate that inter‐layer electronic couplings may result in a drastic decrease of charge mobilities by utilizing field‐effect transistors (FET) based on two phases of titanyl phthalocyanine (TiOPc) crystals. The α‐phase crystals with electronic couplings along two dimensions show a maximum mobility up to 26.8 cm 2 V −1 s −1 . In sharp contrast, the β‐phase crystals with extra significant inter‐layer electronic couplings show a maximum mobility of only 0.1 cm 2 V −1 s −1 . Theoretical calculations on the bulk crystals and model slabs reveal that the inter‐layer electronic couplings for the β‐phase devices will diminish remarkably the device charge transport abilities owing to the coupling direction perpendicular to the current direction. This work provides new insights into the impact of the dimensionality and directionality of the packing arrangements on charge transport in organic semiconductors.
High-mobility and color-tunable highly emissive organic semiconductors (OSCs) are highly promising for various optoelectronic device applications and novel structure–property relationship investigations. However, such OSCs have never been reported because of the great trade-off between mobility, emission color, and emission efficiency. Here, we report a novel strategy of molecular conformation-induced unique crystalline polymorphism to realize the high mobility and color-tunable high emission in a novel OSC, 2,7-di(anthracen-2-yl) naphthalene (2,7-DAN). Interestingly, 2,7-DAN has unique crystalline polymorphism, which has an almost identical packing motif but slightly different molecular conformation enabled by the small bond rotation angle variation between anthracene and naphthalene units. More remarkably, the subtle covalent bond rotation angle change leads to a big change in color emission (from blue to green) but does not significantly modify the mobility and emission efficiency. The carrier mobility of 2,7-DAN crystals can reach up to a reliable 17 cm2 V–1 s–1, which is rare for the reported high-mobility OSCs. Based on the unique phenomenon, high-performance light-emitting transistors with blue to green emission are simultaneously demonstrated in an OSC crystal. These results open a new way for designing emerging multifunctional organic semiconductors toward next-generation advanced molecular (atomic)-scale optoelectronics devices.
This chapter focuses on the development of organic semiconductors, with particular emphasis on the design strategy of novel semiconductors with a high mobility and stability. The organic semiconductor is a key component of an organic field-effect transistor (OFET). In terms of molecular weight, organic semiconductors can be subdivided into small molecules and polymers while, on the basis of the main charge carriers transporting in OFET channels, organic semiconductors can be further divided into p-type, n-type, and bipolar semiconducting materials. The details of some polymer semiconductors are described in the chapter. As most organic semiconductors possess symmetrical molecular structures, the general synthetic techniques employed in this field will not involve complicated chiral syntheses. The organic semiconductors obtained from multistep syntheses always require to be further purified, using a variety of techniques include recrystallization, column chromatography, physical vapor deposition (PVD) and soxhlet extraction. Controlled Vocabulary Terms OFETs; organic semiconductors; semiconductor doped polymers
Abstract A cocrystal strategy with a simple preparation process is developed to prepare novel materials for near‐infrared photothermal (PT) conversion and imaging. DBTTF and TCNB are selected as electron donor (D) and electron acceptor (A) to self‐assemble into new cocrystals through non‐covalent interactions. The strong D–A interaction leads to a narrow band gap with NIR absorption and that both the ground state and lowest‐lying excited state are charge transfer states. Under the NIR laser illumination, the temperature of the cocrystal sharply increases in a short time with high PT conversion efficiency ( η =18.8 %), which is due to the active non‐radiative pathways and inhibition of radiative transition process, as revealed by femtosecond transient absorption spectroscopy. This is the first PT conversion cocrystal, which not only provides insights for the development of novel PT materials, but also paves the way of designing functional materials with appealing applications.
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