Organic Thin-film Transistors Devices Research Articles

Towards sustainable, direct printed, organic transistors with biocompatible copolymer gate dielectrics

Towards sustainable, direct printed, organic transistors with biocompatible copolymer gate dielectrics

Analysis of electrical and hysteresis characteristics of flexible OTFT using solution-processable DPP-DTT polymer and Parylene-C

Organic thin-film transistors (OTFTs) fabricated on Parylene-C substrates have the advantages of a simple process, low cost, and flexible characteristics. This study introduces the manufacturing method and electrical characteristics of an OTFT using organic materials as the substrate, gate dielectric, and channel material. PDPP2T-TT-OD(DPP-DTT) is used as the channel material, which is a highly mobile p-type polymer with good air stability. The proposed OTFT device has flexible characteristics because it is fabricated on a Parylene-C substrate and can be used even in a curved state. Furthermore, the manufacturing process was largely achieved via a simple, low-cost solution process using spin-coating and photolithography with a photo-curable material. Under flat conditions, the threshold voltage (VTH) is approximately –3 V, the average ION/IOFF ratio is approximately 105, and the mobility is 0.84 cm2/Vs.

Stretchable Semiconducting Polymers with Hydrogen-Bonding-Capable Conjugation Breakers: Synthesis and Application in Organic Thin-Film Transistors.

Diketopyrrolopyrrole (DPP)-based conjugated copolymers are important organic semiconductors for applications in high-efficiency organic thin-film transistors (OTFTs). However, the direct application of these polymers with rigid backbones in stretchable devices has limitations. In this study, we designed and synthesized three kinds of DPPBT-based copolymers, DPPBT-A1, DPPBT-A3, and DPPBT-A5, which have amide-coupled alkylene conjugation breakers capable of hydrogen bonding. Linkers with different segment lengths were copolymerized with DPP and bithiophene (BT) backbone units. A DPP-based copolymer with alternating BT moieties, DPPBT, was synthesized as a reference fully conjugated copolymer. The synthesized polymers with freely rotational backbone linkers have sufficient flexibility to develop ordered phase domains, even in thin films, in comparison to the reference copolymer. However, the introduction of the conjugation breakers, which disconnect the intramolecular π-π overlapping, tends to decrease the hole mobility (μ) from 0.76 to 0.20 cm2 V-1 s-1 in the corresponding OTFT devices. The TFT fabricated using DPPBT-A3 showed a mobility of 0.50 cm2 V-1 s-1, and the mobility value did not show a significant change even when elongated by more than 50%. Therefore, the molecular design strategy of introducing amide-coupled alkylene conjugation breakers into conjugated polymer chains can contribute significantly to the development of high-mobility stretchable conjugated polymers in future.

Preparation of Novel Organic Polymer Semiconductor and Its Properties in Transistors through Collaborative Theoretical and Experimental Approaches.

Conjugated polymer semiconductors based on donor-acceptor structures are commonly employed as core materials for optoelectronic devices in the field of organic electronics. In this study, we designed and synthesized a novel acceptor unit thiophene-vinyl-diketopyrrolopyrrole, named TVDPP, based on a four-step organic synthesis procedure. Stille coupling reactions were applied with high yields of polymerization of TVDPP with fluorinated thiophene (FT) monomer. The molecular weight and thermal stability of the polymers were tested and showed high molecular weight and good thermal stability. Theoretical simulation calculations and 2D grazing-incidence wide-angle X-ray scattering (GIWAXS) tests verified the planarity of the material and excellent stacking properties, which are favorable for achieving high carrier mobility. Measurements based on the polymer as an organic thin film transistor (OTFT) device were carried out, and the mobility and on/off current ratio reached 0.383 cm2 V-1 s-1 and 104, respectively, showing its great potential in organic optoelectronics.

High-speed, low-voltage, small-pitch and robust OTFT-based integrated gate driver for active-matrix displays

We design and fabricate a high-speed, low-voltage, small-pitch, and robust integrated gate driver with organic thin-film transistors (OTFTs). The dual-gate OTFT devices have a field effect mobility of 0.78 cm2/Vs, and on/off current ratio above 108. A single stage of the gate driver consists of ten TFTs and two capacitors, with small pitch of 244 μm. The fabricated circuit has a minimum pulse width of 5μs, which is compatible with full-high definition (FHD, 1920 × 1080) active-matrix displays with 60Hz frame rate. It can work at input swing of as low as 10V, with VGH2, VGH1, and VGL of 5V, 0V, and −10V respectively. With the threshold voltage shift under positive and negative bias stress, the gate driver shows output signals without significant degradation and demonstrates its high reliability through simulation.

Role of the Alkylation Patterning in the Performance of OTFTs: The Case of Thiophene-Functionalized Triindoles

Organic semiconductors have emerged as potential alternatives to conventional inorganic materials due to their numerous assets and applications. In this context, the star-shaped triindole core stands as a promising system to design new organic materials with enticing charge-transporting properties. Herein, we present the synthesis of three thiophene-containing triindole derivatives that feature N-alkyl chains of different lengths, from methyl to decyl. The impact of the alkylation patterning on the crystallinity of the thin films and their resultant performance as semiconductor have been analyzed. All derivatives displayed p-type semiconductor properties, as demonstrated via both TOF measurements and integration in organic thin-film transistor (OTFT) devices. The attachment of longer alkyl chains and the functionalization of the silicon substrate with octadecyltrichlorosilane (OTS) prompted better OTFT characteristics, with a hole mobility value up to 5 × 10−4 cm2 V−1 s−1. As elucidated from the single crystal, this core is arranged in a convenient cofacial packing that maximizes the π-overlapping. The analysis of the thin films also corroborates that derivatives possessing longer N-alkyl chains confer a higher degree of order and a more adequate morphology.

From P‐type to N‐type: Peripheral fluorination of axially substituted silicon phthalocyanines enables fine tuning of charge transport

AbstractSilicon phthalocyanines (R2‐SiPcs) are a family of promising tunable materials for organic electronic applications. We report the chemistry of the synthesis of axially substituted fluorinated SiPcs (tb‐Ph)2‐FxSiPc (where X = 0, 4, 8, or 16) and explore how the degree of fluorination effects optical and electronic properties. A new treatment with boron trichloride was included to obtain Cl2‐FXSiPcs from F2‐FXSiPcs, activating the axial position for further functionalization. We observed that as the degree of fluorination increased, so did the electron affinity of the compounds, leading to a drop in frontier orbital levels, as measured by electrochemistry and ultraviolet photoelectron spectroscopy (UPS). The deeper energy levels enabled successful (tb‐Ph)2‐F4SiPc and poly [[6,7‐difluoro[(2‐hexyldecyl)oxy]‐[5,8‐quinoxalinediyl]‐2,5‐thiophenediyl]] (PTQ10) blends for organic photovoltaics and photodetectors. All four compounds were incorporated in organic thin‐film transistors (OTFTs), where the degree of fluorination influenced device operation, changing it from p‐type conduction for (tb‐Ph)2‐F0SiPc, to ambipolar for (tb‐Ph)2‐F4SiPc, and n‐type for (tb‐Ph)2‐F8SiPc and (tb‐Ph)2‐F16SiPc. The OTFT devices made with (tb‐Ph)2‐F16SiPc achieved a low average threshold voltage of 7.0 V in N2 and retained its n‐type mobility when exposed to air.

Self-Assembled Au/P3HT, High-k Bilayer Dielectric-Based Solution Processed Low Voltage OTFT for Multiparametric Ammonia Sensor at Room Temperature

A self-assembled, fully solution-processed, bilayer (TiO2/HfO2) dielectric-based thin film transistor (TFT) has been fabricated and explored for highly sensitive ammonia gas at room temperature (RT—25 °C). The bilayer dielectric film has been grown over a heavily boron-doped silicon substrate (p++ Si), and the thickness of each layer has been optimized by spin coating rotation speed and spin time to find a high-quality gate oxide. The obtained dielectric has a high areal capacitance of 0.926 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{F}$ </tex-math></inline-formula> /cm2, low rms roughness of 0.914 nm, and low leakage current density of ~1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> /cm2, high dielectric constant of ~42, which are much more favorable for the high-performance organic TFT (OTFT). The incorporation of the TiO2 layer in between the p++ Si and HfO2 layer enhances the areal capacitance and minimizes the rms roughness (TiO2 minimizes the no. of interface trap states at the dielectric/semiconductor interface) of the bilayer dielectric film, thereby improving the charge transfer mechanism. The developed high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> bilayer solution-processed dielectric layer has been utilized to develop a low voltage operated (−1.5 V) OTFT for ammonia (NH3) gas at RT. The fabricated OTFT device utilized the solution-processed floating film transfer method (FTM) to grow the Au(gold) doped P3HT film as a sensing/organic semiconductor channel (OSC) layer. The Au/P3HT sensing layer shows a quick response/recovery time (5/17 s), with a high sensing response of 55% (5 ppm) toward the NH3 analyte. The study aims to find a low-voltage, solution-processed, cost-efficient OTFT device for a high-performance gas sensor at RT.

Synthesis of thieno[3,4-c] pyrrole-4,6-dione-based small molecules for application in organic thin-film transistors

The synthesis of two alternating donor-acceptor (D-A) small molecules revolving around thieno[3,4-c]pyrrole-4,6-dione (TPD) as the main acceptor building block is reported herein. The materials are synthesized using a robust Stille coupling to attach the TPD core with thiophene donors on either of its side, and completed with an aldol condensation under mild conditions for the addition of terminal secondary acceptor building blocks, representing a sought out A2-D-A1-D-A2 structure. The two newly synthesized materials are set to be used as organic semiconductors in organic thin-film transistor (OTFT) devices. Comparative optical, computational, and electrochemical studies were carried out on these new materials to investigate their ability to act as potential n-type organic semiconductors. The materials were then incorporated into bottom-gate bottom-contact OTFT devices, and subsequent thin-film engineering studies were done to probe the effects that solvent and post-deposition annealing conditions had on device performance. From these conditions, the rhodanine-derived D-A material exhibited the greatest electron field-effect mobility (0.011 cm2 V−1 s−1), and a threshold voltage of 20.1 V under vacuum.

(Digital Presentation) Effect of Active Layer Thickness on Organic Thin-Film Transistors

ABSTRACT: Thin-Film Transistors (TFTs) are a substantial technological advancement in recent decades for various applications. The source/drain electrode layer and organic active layer thicknesses of Organic Thin-Film Transistors (OTFTs) should be optimized for better device performance. Organic electronics have been used for a wide range of applications, including flexible screens, smart digital devices, and photovoltaic cells, because of their flexibility and environmental sensitivity. The OTFT has the capability to match the efficiency of thin-film amorphous Silicon transistors, while also being companionable with low-temperature solution/printing-processed fabrication on flexible coupling substrates. The OTFTs are a valuable tool for determining unipolar carrier transport parameters in various situations.In this present research work, authors have utilized the concept of OTFTs in the assessment of bipolar transport properties in active layer blends. It offers a strategy to improve the precision of the assessment. Thereafter, in this this research work, impacts of active layer thickness on physical parameters of OTFT device performance have been realized. The 2D numerical device simulators have been used to examine the proposed OTFT structures. The discussion focuses on the various characteristics and parameters of OTFTs. The OTFTs are transistors that manage electric current flow using organic semiconductors as an active layer. The output and transfer characteristics of various OTFT structures have been used to calculate the performance characteristics of OTFTs. Optimizing the OTFT's organic active layer thickness is critical for high device performance. Both photo-current and photo-responsivity exhibit the same variation trend with increasing organic active layer thicknesses, increasing rapidly for a while and then tending to saturate at high values. The research findings demonstrate the impact of these parameters on device performance and temperature and the need to optimize these variables in the device. The carrier mobility of the high-performance P3HT: PCBM-based OTFT structure was approximately 10 cm2/Vs, and an ON/OFF current ratio of ~103. These results are compatible with those OTFTs fabricated previously. Research Methodology, Results, and Discussions A schematic structure is shown in Figure 1(a) proposed structure top view, and 1(b) a side view of the proposed structure used for simulation. Top-gate OTFT and bottom-gate OTFT geometrical structures have been used in this OTFT. The device's contact resistance, field mobility, and threshold voltage degrade subjected to bias stress. Since top-gate OTFT has a higher device degradation, the authors used bottom-gate OTFT. Due to the distinct properties here in this work the authors utilized conventional materials such as a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as the active layer. A P3HT: PCBM mix is simulated with an electronic device simulator and analyses the variation in active layer thickness that affects the device's performance and the factors that influence the performance of the device in this research work. The output and transfer characteristics of OTFTs have been realized using proper boundary conditions and OTFT physics. The proposed OTFT structures' output and transfer characteristics have been evaluated, and the simulated results show that the optimized structure's drain current (Id, max) is ~2.85 μA. The obtained results show that the device has good transfer and output characteristics at lower gate voltages. With increasing organic active layer thicknesses, both photo-current and photo-responsivity exhibit the same variation trend of increasing sharply at first and then tending to saturate at high values. Conclusion The simulation results examined the performance of devices built with bottom-gate OTFTs. A detailed analysis of the influence of active layer thickness on the OTFT configuration was realized. The device has the advantage of operating at a lower gate voltage, transforming it into a gate efficient control device. The operation at a lower voltage improves electrical stability. The electric field of the OTFT is 1.4x106 V/cm is obtained. The ON/OFF current ratio is higher. The outcomes of this analysis have been optimized and extracted after being tested in various contexts. The findings demonstrated that the suggested concept might be used to make rollable active-matrix displays, nonvolatile memory, sensors, and printed electronic devices. This work also reduces the SCEs and shows more efficient performance than traditional MOSFETs. Together with all application areas, the most important research area has been argued to be the simple manufacturing technique of OTFT with low production cost and non-breakable impacts that can be bent and folded. This device will be optimized with fabrication using these materials in the future, and thereafter, its characteristic will be verified with the simulated results. Figure 1

26.1: Invited Paper: Organic TFTs for Biaxially formed Active Surfaces

The most common transistor technologies for making active matrix displays and sensors use hard ceramic materials for the semiconducting active layer [1]. To enable flexible displays and electronics, FlexEnable has pioneered an alternative manufacturing approach which uses soft, flexible organic materials as the active layers [2–4]. Organic thin film transistor (OTFT) backplanes using FlexiOMTM materials can be fabricated in standard flat panel display factories which are repurposed for the novel material set. A primary benefit for using OTFT is the inherent durability that comes from removing the brittle ceramic layers. This feature can be further exploited by proactively stretching the devices to conform to more attractive form factor products. This paper will discuss the electrical performance of a state-of-the-art OTFT device and impact of a thermoforming process on switching characteristics.

(Digital Presentation) Effect of Active Layer Thickness on Organic Thin-Film Transistors

Thin-Film Transistors (TFTs) are a substantial technological advancement in recent decades for various applications. The source/drain electrode layer and organic active layer thicknesses of Organic Thin-Film Transistors (OTFTs) should be optimized for better device performance. In the current study, the authors have utilized the concept of OTFTs in the assessment of bipolar transport properties in active layer blends. It offers a strategy to improve the precision of the assessment. Thereafter, in this research work, impacts of active layer thickness on physical parameters of OTFT device performance have been realized. The study's findings show how these characteristics affect device performance and the need to optimize these variables in the device. The drain current of the high-performance P3HT: PCBM-based OTFT structure was approximately 4.3 µA for the thickness of 200 nm active layer, which has the highest performance.

Bottom gate top contact organic transistors using thiophene and furan flanked diketopyrrolopyrrole polymers and its comparative study

Herein, two donor–acceptor conjugated polymers based on dithieno[3,2-b:2′,3′-d]thiophene (DTT) and thiophene-flanked diketopyrrolopyrrole (DPP) or furan-flanked DPP, namely PDPPT-DTT and PDPPF-DTT were synthesised, characterised and evaluated for their electrical performance in transistor devices for comparison. The influence of the heteroatoms (thiophene and furan) flanked DPP on their thermal, optical, electronic structure and charge carrier transport properties were investigated. The absorption spectra of polymer PDPPT-DTT are broader and red-shifted (26–30 nm) compared with that of polymer PDPPF-DTT, indicating the resonance energy of thiophene is greater than furan, which may allow for different electron localization and result in the difference of optical properties. In addition, energy levels of polymers were slightly affected by the aromatic remote end-groups (thiophene to furan) in DPP-based molecule. Hole transport properties of copolymers were investigated by fabricating the field-effect transistors in the bottom gate top contact (BGTC) configurations for three different self-assembled monolayers (SAMs)/gate dielectric interfaces and different annealing temperatures of polymeric active layer. The BGTC organic thin film transistor (OFET) devices having PDPPT-DTT and PDPPF-DTT thin film annealed at 200 °C exhibit the hole mobility of 0.18 and 0.20 cm2 V−1 s−1, respectively. The OFET devices with trichloro(octyl)silane SAM, fabricated and characterized in ambient environment (temperature ∼25 °C, humidity ∼50%), were found to retain 90% of their performance up to 1000 h.

Design Strategies and Prospects in Developing Wearable Glucose Monitoring System Using Printable Organic Transistor and Microneedle: A Review

Diabetes mellitus is a worldwide leading disease that brings about fatal complications due to poor body glucose management which requires regular screening. With progressive evolution of healthcare monitoring system, high demand for wearable biosensors has efficiently bridged the gap between organic semiconductor devices and biological systems due to their flexibility and biocompatibility as enzyme-based transducing mechanism. In this work, significant features of existing glucose monitoring systems and integration components are evaluated to extend the fully integrated sensing platform with exciting potentials of organic thin-film transistor (OTFT) as electrochemical glucose sensor at low manufacturing process <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&lt; 200 ^{\circ }\text{C}$ </tex-math></inline-formula> . This review highlights the design strategies and challenges in developing printable OTFT devices with low voltage and high on/off-current ratio <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt; 10^{6}$ </tex-math></inline-formula> by considering material configuration including nanomaterials, advanced printing techniques and functionalization for highly sensitive performance based on amperometric or potentiometric measurements. For sample extraction, the role of microneedle is critically discussed with their prospects to provide real-time diagnosis of interstitial fluid through correlation with blood glucose for long wear period. It can be concluded that this paper accentuates the potentials of printable OTFT biosensors and ISF sampling system based on microneedle by adapting the key design requirements and characteristics presented here for novel breakthrough of cost-effective, minimally invasive and self-monitoring flexible integrated glucose sensor system that conform to skin.

Evolution of solution-based organic thin-film transistor for healthcare monitoring– from device to circuit integration: A review

Demand for organic electronics has growth tremendously for the past decade, owing to their high flexibility and low processing cost attributes. As part of the important elements in organic electronics, a solution processable organic thin film transistor (OTFT) has been center of discussion among researchers. The OTFT is recognized to bring electrical, mechanical, and industrial benefits to a broad range of new applications such as flexible displays, radio frequency identification (RFID) tags, as well as biosensors specifically for healthcare monitoring system. Despite of their great application demand and significant technology advancement, the OTFT devices demonstrate unstable electrical performances especially in their mobilities and threshold voltages. These drawbacks will hold the fully commercialization of the OTFT in the market. Thus, this paper comprehensively reviews the current status of the OTFT technologies, ranging from material, device, process, and integration, including improvement that have been done on mobilities and operating voltages. Besides that, this work discusses on the applicability of the OTFT in the biosensor applications dedicated for real-time healthcare monitoring purposes. This review paper therefore is expected to provide a critical analysis on OTFT developments, as well as recognize their research gaps to allow their fully commercialization in the near future.

Powder X-ray diffraction as a powerful tool to exploit in organic electronics: shedding light on the first N,N',N''-trialkyldiindolocarbazole.

The first crystal structure of a fully N-alkylated diindolocarbazole derivative, namely, 5,8,14-tributyldiindolo[3,2-b;2',3'-h]carbazole (1, C36H39N3), has been determined from laboratory powder X-ray diffraction (PXRD) data. A complex trigonal structure with a high-volume unit cell of 12987 Å3 was found, with a very long a(=b) [52.8790 (14) Å] and a very short c [5.36308 (13) Å] unit-cell parameter (hexagonal setting). The detailed analysis of the intermolecular interactions observed in the crystal structure of 1 highlights its potential towards the implementation of this core as a semiconductor in organic thin-film transistor (OTFT) devices. Since the molecule has a flat configuration reflecting its π-conjugated system, neighbouring molecules are found to stack atop each other in a slipped parallel fashion via π-π stacking interactions between planes of ca 3.30 Å, with a centroid-centroid distance between the aromatic rings corresponding to the shortest axis of the unit cell (i.e. c). The alkylation of the three N atoms proves to be a decisive feature since it favours the presence of C-H...π interactions in all directions, which strengthens the crystal packing. As a whole, PXRD proves to be a valuable option for the resolution of otherwise inaccessible organic crystal structures of interest in different areas.

Benchmarking contact quality in N-type organic thin film transistors through an improved virtual-source emission-diffusion model

Due to nonideal behavior, current organic thin film transistor technologies lack the proper models for essential characterization and thus suffer from a poorly estimated parameter extraction critical for circuit design and integration. Organic thin film transistors are often plagued by contact resistance, which is often less problematic in inorganic transistors; consequently, common models used for describing inorganic devices do not properly work with organic thin film transistors. In this work, we fabricate poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} based organic thin film transistors with reduced contact resistance through the introduction of metallic interlayers between the semiconductor and gold contacts. The addition of 10 nm thick manganese interlayer provides optimal organic thin film transistor device performance with the lowest level of contact resistance. Improved organic thin film transistors were characterized using an improved organic virtual-source emission diffusion model, which provides a simple and effective method to extract the critical device parameters. The organic virtual-source emission diffusion model led to nearly perfect prediction using effective gate voltages and a gate dependant contact resistance, providing a significant improvement over common metal–oxide–semiconductor field-effect transistor models such as the Shichman–Hodges model.

Negative Differential Resistance Behavior in n‐Channel Organic Thin‐Film Transistors Based on C 60 and PTCDI‐C8: Electrical Characterization and Parameter Extraction

Organic thin-film transistors (OTFTs), based on two n-type structures of fullerene (C60) and N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8), are investigated. The two OTFT devices reveal a negative differential resistance (NDR) behavior in the saturation region of the output curves. The OTFT based on C60 shows a more pronounced NDR than that based on PTCDI-C8. The main origin of the NDR is ascribed to the trapping states. In addition, the contact resistance (Rc) of the two devices, extracted using the developed voltage transition method (Vtr method), as well as the obtained values of Rc, are in fair agreement with the experimental values extracted using the total resistance. The device based on C60 exhibits a higher Rc than that based on PTCDI-C8. OTFT parameters, such as transconductance (gm), mobility (μmax), threshold voltage (Vth,), turn-on voltage (Von), ratio current Ion/Ioff, and subthreshold slope (SS), are obtained in the linear and saturation regimes. The extracted value of SS for the OTFT based on C60 is very small compared with that of the device based on PTCDI-C8, which indicates an increase in the density of trapping states in the C60 film.

Advances in environmentally-friendly organic thermoelectric and organic thin-film transistor materials

<p indent=0mm>Organic semiconductors (OSCs) are significant systems of next-generation optoelectronic materials, which are widely applied in flexible devices, power generation and sensors. However, most of the organic semiconductors are prepared in chlorinated solvents which are harmful to human health and ecological environment. Nowadays, accompanied with the trends of environmentally-friendly optoelectronics, the OSCs processed with green solvents attracted extensive attention and developed rapidly. In this article, we reviewed the advances in environmentally-friendly OSCs in molecular design, solvent selection and processing method. The application of those materials in organic thin-film transistor and organic thermoelectric devices was highlighted. Finally, challenges and perspectives of the environmentally-friendly OSCs are also summarized.

Electrohydrodynamic-Jet-Printed Cinnamate-Fluorinated Cross-Linked Polymeric Dielectrics for Flexible and Electrically Stable Operating Organic Thin-Film Transistors and Integrated Devices.

Herein, printable polymer series containing different portions of cinnamate and perfluorinated phenyl functionalities, namely, polyperfluorostyrene-co-poly(vinylbenzyl cinnamates) (PFS-co-PVBCi (x:y)) copolymers, were synthesized and applied as gate dielectrics for organic thin-film transistors (OTFTs). The polymeric dielectrics were successfully printed via electrostatic force-assisted dispensing mode of electrohydrodynamic jet printing. The dielectric characteristics of the printed polymers, such as surface energy, dielectric constant, leakage current, atomic depth profiles, and deposited semiconducting layer characteristics, were clearly identified. In particular, the difference in driving stability of OTFTs according to the type of polymer was analyzed in detail and a possible mechanism was proposed. Results suggested that PFS-co-PVBCi (3:7) led to optimized consequences, yielding an almost negligible Vth shift under continuous bias stress. Through this, we successfully implemented flexible OTFT and logic devices using printed PFS-co-PVBCi (3:7) dielectrics with stable operation properties. Therefore, we believe that this study will facilitate the printing and synthesis of polymer dielectrics to produce printed and flexible OTFTs.