Organic Field-effect Transistors Devices Research Articles

Charge Carrier Inversion in a Doped Thin Film Organic Semiconductor Island.

Inducing an inversion layer in organic semiconductors is a highly nontrivial, but critical, achievement for producing organic field-effect transistor (OFET) devices, which rely on the generation of inversion, accumulation, and depletion regimes for successful operation. Here, we develop a pulsed bias technique to characterize the dopant type of any organic material system, without prior knowledge or characterization of the material in question. We use this technique on a pentacene/PTCDI heterostructure and thus deduce that pentacene is exhibiting n-doped like response. The source of the additional charges in the pentacene island can be identified by charging rings in the dissipation channel of the noncontact atomic force microscopy (AFM) signal, a typical signature for localized charge transfer from the AFM tip to the sample. Additionally, through tip-induced band-bending, we generate inversion, depletion, and accumulation regimes over a 20 nm radius, three monolayer thick n-doped pentacene island. Our findings demonstrate that nanometer-scale lateral extent and thickness are sufficient for an OFET device to operate in the inversion regime.

Acridino[2,1,9,8-klmna]acridine Bisimides: An Electron-Deficient π-System for Robust Radical Anions and n-Type Organic Semiconductors.

We report the synthesis and properties of acridino[2,1,9,8-klmna]acridine bisimide (AABI), a nitrogen-doped anthanthrene with two imide functionalities. AABI exhibits excellent electron affinity as evident by its low-lying LUMO level (-4.1 eV vs. vacuum). Single-electron reduction of one AABI derivative afforded the corresponding radical anion, which was stable under ambient conditions. Photoconductivity measurements suggest that the intrinsic electron mobility of an N-phenethyl AABI derivative obeys a band-transport model. Accordingly, an electron mobility of 0.90 cm2 V-1 s-1 was attained with the corresponding single-crystal organic field-effect transistor (OFET) device. The vacuum-deposited OFET device consisting of a polycrystalline sample exhibited high electron mobility of up to 0.27 cm2 V-1 s-1 even in air. This study demonstrates that dual incorporation of both imide substituents and imine-type nitrogen atoms is an effective strategy to create novel electron-deficient π-systems.

Acridino[2,1,9,8‐klmna]acridine Bisimides: An Electron‐Deficient π‐System for Robust Radical Anions and n‐Type Organic Semiconductors

AbstractWe report the synthesis and properties of acridino[2,1,9,8‐klmna]acridine bisimide (AABI), a nitrogen‐doped anthanthrene with two imide functionalities. AABI exhibits excellent electron affinity as evident by its low‐lying LUMO level (−4.1 eV vs. vacuum). Single‐electron reduction of one AABI derivative afforded the corresponding radical anion, which was stable under ambient conditions. Photoconductivity measurements suggest that the intrinsic electron mobility of an N‐phenethyl AABI derivative obeys a band‐transport model. Accordingly, an electron mobility of 0.90 cm2 V−1 s−1 was attained with the corresponding single‐crystal organic field‐effect transistor (OFET) device. The vacuum‐deposited OFET device consisting of a polycrystalline sample exhibited high electron mobility of up to 0.27 cm2 V−1 s−1 even in air. This study demonstrates that dual incorporation of both imide substituents and imine‐type nitrogen atoms is an effective strategy to create novel electron‐deficient π‐systems.

Photocontrollable Modulation of Frontier Molecular Orbital Energy Levels of Cyclopentenone-Based Diarylethenes

Photoswitchable diarylethenes provide a unique opportunity to optically modulate frontier molecular orbital energy levels, thereby opening an avenue for the design of electronic devices such as photocontrollable organic field-effect transistors (OFETs). In the present work, the absolute position of the frontier orbital levels of nonsymmetrical diarylethenes based on a cyclopentenone bridge has been studied using cyclic voltammetry and density functional theory (DFT) calculations. It has been shown that varying heteroaromatic substituents make it possible to change the absolute positions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of both diarylethene photoisomers. The data obtained are used to refine the operation mechanism of the previously developed OFET devices, employing the cyclopentenone-derived diarylethenes at the dielectric/semiconductor interface.

Utilizing the Diffusion of Fluorinated Polymers to Modify the Semiconductor/Dielectric Interface in Solution-Processed Conjugated Polymer Field-Effect Transistors.

It has been demonstrated that tailoring the properties of semiconductor/dielectric interfaces with fluorinated polymers yields better performance for organic field-effect transistors (OFETs). However, it remains a challenge to fabricate bottom-gate OFET devices on fluorinated dielectrics using solution-processed methods due to the poor wettability of fluorinated dielectrics. Here, we utilized the diffusion of fluorinated poly(methyl methacrylate) (PMMA) to construct the fluorine-rich semiconductor/dielectric interface to achieve the fabrication of bottom-gate OFETs with a solution-processed poly(3-hexylthiophene) (P3HT) semiconductor layer. The consequences indicate that the fluorinated dielectrics can effectively decrease the charge traps density at the semiconductor/dielectric interface and promote the edge-on orientation of P3HT on the dielectric surface. Thus, the devices based on fluorinated PMMA modified dielectrics exhibit higher carrier mobility and electrical stability than those of the fluorine-free devices. Our investigation affords a new strategy for the design and interface optimization of devices, which may further advance the performance of OFET devices.

Strategy for Selective Printing of Gate Insulators Customized for Practical Application in Organic Integrated Devices.

Direct drawing techniques have contributed to the ease of patterning soft electronic materials, which are the building blocks of analog and digital integrated circuits. In parallel with the printing of semiconductors and electrodes, selective deposition of gate insulators (GI) is an equally important factor in simplifying the fabrication of integrated devices, such as NAND and NOR gates, and memory devices. This study demonstrates the fabrication of six types of printed GI layers (high/low-k polymer and organic-inorganic hybrid material), which are utilized as GIs in organic field-effect transistors (OFETs), using the electrostatic-force-assisted dispensing printing technique. The selective printing of GIs on the gate electrodes enables us to develop practical integrated devices that go beyond unit OFET devices, exhibiting robust switching performances, non-destructive operations, and high gain values. Moreover, the flexible integrated devices fabricated using this technique exhibit excellent operational behavior. Therefore, this facile fabrication technique can pave a new path for the production of practical integrated device arrays for next-generation devices.

Electrode and dielectric layer interface device engineering study using furan flanked diketopyrrolopyrrole\u2013dithienothiophene polymer based organic transistors

We successfully demonstrated a detailed and systematic enhancement of organic field effect transistors (OFETs) performance using dithienothiophene (DTT) and furan-flanked diketopyrrolopyrrole based donor–acceptor conjugated polymer semiconductor namely PDPPF-DTT as an active semiconductor. The self-assembled monolayers (SAMs) treatments at interface junctions of the semiconductor–dielectric and at the semiconductor–metal electrodes has been implemented using bottom gate bottom contact device geometry. Due to SAM treatment at the interface using tailored approach, the significant reduction of threshold voltage (Vth) from − 15.42 to + 5.74 V has been observed. In addition to tuning effect of Vth, simultaneously charge carrier mobility (µFET) has been also enhanced the from 9.94 × 10−4 cm2/Vs to 0.18 cm2/Vs. In order to calculate the trap density in each OFET device, the hysteresis in transfer characteristics has been studied in detail for bare and SAM treated devices. Higher trap density in Penta-fluoro-benzene-thiol (PFBT) treated OFET devices enhances the gate field, which in turn controls the charge carrier density in the channel, and hence gives lower Vth = + 5.74 V. Also, PFBT treatment enhances the trapped interface electrons, which helps to enhance the mobility in this OFET architecture. The overall effect has led to possibility of reduction in the Vth with simultaneous enhancements of µFET in OFETs, following systematic device engineering methodology.

Synthesis of SnO<sub>2</sub> Nanoparticles Using <i>Ficus religiosa </i>Leaf Extract and their Application in Fabrication of OFETs for Glucose Monitoring

Organic field effect transistors (OFETs) as a sensor have gained interest of researchers due to its portable size and less expensive design in the field of medical diagnostic, food monitoring, chemical detection, wearable sensors, etc. In this present research work, we demonstrate the fabrication of OFETs from organic-inorganic SnO2 nanoparticles tailored pentacenefor glucose detection. SnO2 nanoparticles were synthesized bygreen method using Ficus religiosa leaf extract. The as-synthesized SnO2 NPs with cassiterite crystal structure was analysed using X-Ray Diffraction (XRD) and the energy bandgap of ~3.8 eV was calculated using Tauc relation with absorption spectra so obtained from UV-vis spectroscopy (UV-vis). The structure and morphological analysis of SnO2 NPs with size of ~15 nm was confirmed by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) analysis. The sensor characteristics of OFET device fabricated using pentacene layer (soluble pentacene precursor of DMP) and as-synthesized SnO2 nanoparticles confirmed the aqueous glucose (glucose in water) detection at room temperature (27 °C). The extracted electrical parameters such as mobility (μ), On-current (Ion), saturation current (IDsat) and the sensor response were discussed to support the sensor characteristics.

Efficient Synthesis of π-Conjugated Organic Molecules Utilizing Cross-Coupling Reactions and Application to Electronic Devices

The development of efficient synthetic methods of π-conjugated compounds by means of cross-coupling reactions are reported. Tetraarylethenes with four different substituents are synthetic targets. The Pt-catalyzed addition of diboron to alkynylsilanes to yield 1-aryl-1-silyl-2,2-diborylethenes with perfect stereoselectivity. Step by step chemoselective Suzuki-Miyaura couplings with aryl halides were performed to give a triarylsilylethene with perfect chemoselectivity. The silyl group was transformed to the aryl group with desilybromination, followed by Suzuki-Miyaura coupling, leading to the successful synthesis of the desired tetraarylated olefin. On the other hand, novel and versatile methods for the synthesis of various phenacene and thienophenacene derivatives by cross-coupling reactions were elucidated for application to organic field-effect transistors (OFETs) and organic photovoltaics (OPVs). As one of representative phenacenes, picene is a polycyclic aromatic hydrocarbon consisting of five fused benzene rings with a W-shape structure, which exhibits high hole mobility. We successfully found the synthetic route of various substituted picenes. In addition, the synthesis of phenanthro [1,2-b : 8,7-b’] dithiophene (PDT) was achieved by replacing two terminal phenyl rings in picene with thiophene rings. The fabricated OFET devices based on C12-PDT-2 displayed a quite high mobility of up to 5.6 cm2 V−1 s−1. In regard to OPV devices, PDT-fluorinated benzothiadiazole (BT) polymers possessing alkyl side chains showed the highest power conversion efficiencies (PCE) of 9.0%.

Eco-friendly collagen-based bio-organic field effect transistor with improved memory characteristics

Abstract With the miniaturization race, organic field-effect transistor (OFET) devices have gained much attention in recent years due to their advantages of flexibility, light weight, solution processability and low manufacturing cost. However, some inorganic or organic materials are eco-unfriendly. Therefore, in this study, the natural biological proteins collagen hydrolysate acts as dielectric material due to the presence of hydroxyl groups. Cationic surfactant hexadecyltrimethylammonium chloride (CTMA) is added into collagen hydrolysate to form a dielectric layer in bio thin film transistor (BioTFT) device. Experimental results highlight that the collagen-CTMA mixture at 3 wt% (Col-CTMA3) has shown an average mobility of 3.36 × 10−2 cm2V−1s−1 and an on/off ratio up to 2.7 × 106.1-aminopyrene is embedded into Col-CTMA3 mixture to form Col-CTMA3-1-aminopyrene (Col-CTMA3-AP) mixture to fabricate bio field-effect transistor (BioFET) type memory device. Furthermore, the optimized addition of 1-aminopyrene in the Col-CTMA3-AP mixture for memory device has provided enhanced performances associated to an average mobility of 1.23 × 10−2 cm2V−1s−1, an on/off ratio up to 5.22 × 105 and a memory window of 13.6 V, as the proportion of 1-aminopyrene increased, the charge-trapping ability of collagen strengthened. Environment effect studies have shown that BioFET memory devices placed under water environment highlight the role of the hydroxyl group for the improved BioFET performance.

A-D-A Type Semiconducting Small Molecules with Bis(alkylsulfanyl)methylene Substituents and Control of Charge Polarity for Organic Field-Effect Transistors.

In this study, we synthesize four different kinds of bis(alkylsulfanyl)methylene-substituted 4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene (IDT)-based acceptor-donor-acceptor (A-D-A) type small molecules (IDSIC, IDSIC-4F, IDSIC-4Cl, and IDSTIC) by incorporating electron-withdrawing halogen atoms or electron-releasing thiophene spacers. Herein, enhanced structural planarity and crystalline intermolecular packing are induced by the sp2-hybridized C═C double bond side chains and sulfur-sulfur chalcogen interactions. The fine control of intramolecular charge transfer modulates the electrochemical characteristics and the resulting carrier polarity in organic field-effect transistors (OFETs). Well-balanced ambipolar, n-dominant, and p-dominant charge transport properties are successfully demonstrated in OFETs by modulating the electron-donating or withdrawing strength based on the A-D-A structural motif, resulting in hole/electron mobilities of 0.599/0.553, 0.003/0.019, 0.092/0.897, and 0.683/0.103 cm2/V·s for IDSIC, IDSIC-4F, IDSIC-4Cl, and IDSTIC respectively, after thermal annealing at 200 °C. Thermal annealing of the as-cast films improves the intermolecular packing in an edge-on fashion, which is investigated in detail by grazing incidence X-ray scattering. Finally, complementary logic circuits, i.e., NOT, NAND, and NOR, are fabricated by assembling p-dominant IDSTIC and n-dominant IDSIC-4Cl OFETs. Therefore, a simple and efficient molecular design strategy for fine tuning the charge polarity and charge transport properties of OFET devices is presented.

Developing molecular-level models for organic field-effect transistors.

Organic field-effect transistors (OFETs) are not only functional devices but also represent an important tool for measuring the charge-transport properties of organic semiconductors (OSs). Thus, efforts to understand the performance and characteristics of OFET devices are not only useful in helping achieve higher device efficiencies but also critical to ensuring accuracy in the evaluations of OS charge mobilities. These studies rely on OFET device models, which connect the measured current characteristics to the properties of the OSs. Developing such OFET models requires good knowledge of the charge-transport processes in OSs. In device active layers, the OS thin films are either amorphous (e.g. in organic light-emitting diodes and organic solar cells) or crystalline (e.g. those optimized for charge transport in OFETs). When the electronic couplings between adjacent OS molecules or polymer chain segments are weak, the charge-transport mechanism is dominated by hopping processes, which is the context in which we frame the discussion in this Review. Factors such as disorder, mobility anisotropy, traps, grain boundaries or film morphology all impact charge transport. To take these features fully into account in an OFET device model requires considering a nano-scale, molecular-level resolution. Here, we discuss the recent development of such molecular-resolution OFET models based on a kinetic Monte Carlo approach relevant to the hopping regime. We also briefly describe the applicability of these models to high-mobility OFETs, where we underline the need to extend them to incorporate aspects related to charge delocalization.

Tuning Interfacial Properties by Spontaneously Generated Organic Interlayers in Top‐Contact‐Structured Organic Transistors

AbstractControlling the interfacial properties between the electrode and active layer in organic field‐effect transistors (OFETs) can significantly affect their contact properties, resulting in improvements in device performance. However, it is difficult to apply to top‐contact‐structured OFETs (one of the most useful device structures) because of serious damage to the organic active layer by exposing solvent. Here, a spontaneously controlled approach is explored for optimizing the interface between the top‐contacted source/drain electrode and the polymer active layer to improve the contact resistance (RC). To achieve this goal, a small amount of interface‐functionalizing species is blended with the p‐type polymer semiconductor and functionalized at the interface region at once through a thermal process. The RC values dramatically decrease after introduction of the interfacial functionalization to 15.9 kΩ cm, compared to the 113.4 kΩ cm for the pristine case. In addition, the average field‐effect mobilities of the OFET devices increase more than three times, to a maximum value of 0.25 cm2 V−1 s−1 compared to the pristine case (0.041 cm2 V−1 s−1), and the threshold voltages also converge to zero. This study overcomes all the shortcomings observed in the existing results related to controlling the interface of top‐contact OFETs by solving the discomfort of the interface optimization process.

Effect of Block Sequence in All-Conjugated Triblock Copoly(3-alkylthiophene)s on Control of the Crystallization and Field-Effect Mobility

Despite recent impressive advances in synthesis of all-conjugated diblock copolymers via facile quasi-living Grignard metathesis (GRIM) polymerization, it remains challenging to achieve well-defined all-conjugated triblock copolymers of interest. Herein, we report the judicious design and synthesis of a series of all-conjugated triblock copoly(3-alkylthiophene)s consisting of poly(3-butylthiophene) (P3BT), poly(3-hexylthiophene) (P3HT), poly(3-octylthiophene) (P3OT), or poly(3-dodecylthiophene) (P3DDT) in all 12 possible combinations. The effects of block sequences and the length of alkyl side chains on their cocrystallization and microphase-separated structures are investigated. Moreover, the correlation between different crystalline structures and charge mobilities in organic field-effect transistors (OFETs) is scrutinized. These rationally synthesized triblock copoly(3-alkylthiophene)s self-assemble into cocrystals with an edge-on orientation in as-cast and 150 °C-annealed samples. Remarkably, the combinations with the shortest alkyl side chains placed as the central block (i.e., P3HT-b-P3BT-b-P3OT, P3HT-b-P3BT-b-P3DDT, P3OT-b-P3BT-b-P3DDT, and P3OT-b-P3HT-b-P3DDT) exhibit higher film crystallinity and charge mobilities than the other two combinations where the blocks with shortest alkyl side chains are located at two terminals. Intriguingly, upon thermal annealing near the melting temperature of these combinations, P3BT-b-P3OT-b-P3HT, P3BT-b-P3DDT-b-P3OT, and P3HT-b-P3DDT-b-P3OT can retain their cocrystalline structure while the other combinations are found to microphase separate. Finally, the all-conjugated triblock copoly(3-alkylthiophene)s with proper block sequence demonstrate stable charge mobilities at high temperatures and good flexibility in OFET devices. Taken together, this study elucidates that the block sequence is of key importance on control of the crystallization and charge transport behavior of poly(3-alkylthiophene)-based triblock copolymers.

Synergistic Use of Pyridine and Selenophene in a Diketopyrrolopyrrole‐Based Conjugated Polymer Enhances the Electron Mobility in Organic Transistors

AbstractTo achieve semiconducting materials with high electron mobility in organic field‐effect transistors (OFETs), low‐lying energy levels (the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)) and favorable molecular packing and ordering are two crucial factors. Here, it is reported that the incorporation of pyridine and selenophene into the backbone of a diketopyrrolopyrrole (DPP)‐based copolymer produces a high‐electron‐mobility semiconductor, PDPPy‐Se. Compared with analogous polymers based on other DPP derivatives and selenophene, PDPPy‐Se features a lower LUMO that can decrease the electron transfer barrier for more effective electron injection, and simultaneously a lower HOMO that, however, can increase the hole transfer barrier to suppress the hole injection. Combined with thermal annealing at 240 °C for thin film morphology optimization to achieve large‐scale crystallite domains with tight molecular packing for effective charge transport along the conducting channel, OFET devices fabricated with PDPPy‐Se exhibit an n‐type‐dominant performance with an electron mobility (μe) as high as 2.22 cm2 V−1 s−1 and a hole/electron mobility ratio (μh/μe) of 0.26. Overall, this study demonstrates a simple yet effective approach to boost the electron mobility in organic transistors by synergistic use of pyridine and selenophene in the backbone of a DPP‐based copolymer.

Energy-efficient, fully flexible, high-performance tactile sensor based on piezotronic effect: Piezoelectric signal amplified with organic field-effect transistors

Abstract Fully flexible piezoelectric tactile sensors with low power consumption and high sensitivity play an important role in artificial intelligence, advanced manufacturing, and smart wearable devices. Herein, we constructed a high-performance, energy-efficient, and fully flexible piezoelectric tactile sensor based on piezotronic effect through the integration of piezoelectric materials with the mechanical-to-electrical conversion function of β polyvinylidene fluoride (PVDF) nanorod arrays and the signal amplification function of organic field-effect transistor (OFET) devices. PVDF nanorod arrays, which considerably improve the piezoelectric properties of materials, transform the external mechanical force into piezoelectric voltage to drive the OFET. Further, the piezoelectric voltage can be effectively amplified using an OFET to improve the sensitivity of the tactile sensor. Enabled by the unique structure of sensing devices and well-defined active materials, the fabricated tactile sensor exhibited excellent pressure sensitivity, detection limit, and response time of 5.17 kPa⁻1, 175 Pa, and 150 ms, respectively. In addition, using a sophisticated fabrication process, we demonstrated a flexible integrated tactile sensor array with a 3 × 3 cell on a polyethylene terephthalate (PET) substrate to detect the bending angle of the user's wrist on which the fabricated device was mounted. This study uses piezotronic transistors to convert pressure into electrical signals without applying a gate voltage, which can substantially simplify circuit models and sensor distribution; additionally, the fabricated device provides technical support for flexible electronic skin (e-skin).

Aptamer-Enhanced Organic Electrolyte-Gated FET Biosensor for High-Specificity Detection of Cortisol

Organic field-effect transistor (FET) devices offer a low-cost manufacturing and simple integration of biorecognition molecules for biosensory applications. In electrolyte-gated organic FET (EGOFET) biosensors, a biofluid is directly integrated as the OFET gate dielectric for label-free bioelectronic sensing. The critical constraints of these devices are biofouling and the organic polymer's susceptibility to environmental effects. In this letter, we solve these issues by implementing a multilayered gate dielectric system in our low-cost OFET biosensor, encompassing the bioelectrolyte and an aptamer-enhanced top gate surface for the rapid high-sensitivity detection of cortisol in synthetic buffer solutions. To emphasize the crucial architectural and operational differences to EGOFETs, we have termed these devices as organic electrolyte-gated FET (OEGFETs). We also reported a numerical model that can be fitted to predict the behavior of the cortisol-specific OEGFET biosensors and highlighted the distinct advantages of our system, compared with the more traditional EGOFET sensors. The specificity of our cortisol biosensor is rigorously tested using two negative control biomolecules, i.e., progesterone and cortisone. Molecules that structurally resemble cortisol and like cortisols are present in detectable concentrations in the saliva. The detectable cortisol concentration range of our OEGFET biosensor is currently identified as 27.3 pM-27.3 μM.

On the Nature of Charge-Injecting Contacts in Organic Field-Effect Transistors.

Organic field-effect transistors (OFETs) are key enabling devices for plastic electronics technology, which has a potentially disruptive impact on a variety of application fields, such as health, safety, and communication. Despite the tremendous advancements in understanding the OFET working mechanisms and device performance, further insights into the complex correlation between the nature of the charge-injecting contacts and the electrical characteristics of devices are still necessary. Here, an in-depth study of the metal-organic interfaces that provides a direct correlation to the performance of OFET devices is reported. The combination of synchrotron X-ray spectroscopy, atomic force microscopy, electron microscopy, and theoretical simulations on two selected electron transport organic semiconductors with tailored chemical structures allows us to gain insights into the nature of the injecting contacts. This multiple analysis repeated at the different stages of contact formation provides a clear picture on the synergy between organic/metal interactions, interfacial morphology, and structural organization of the electrode. The simultaneous synchrotron X-ray experiments and electrical measurements of OFETs in operando uncovers how the nature of the charge-injecting contacts has a direct impact on the injection potential of OFETs.

The Critical Role of Materials' Interaction in Realizing Organic Field-Effect Transistors Via High-Dilution Blending with Insulating Polymers.

High-performance low-band-gap polymer semiconductors are visibly colored, making them unsuitable for transparent and imperceptible electronics without reducing film thickness to the nanoscale range. Herein, we demonstrate polymer/insulator blends exhibiting favorable miscibility that improves the transparency and carrier transport in an organic field-effect transistor (OFET) device. The mesoscale structures leading to more efficient charge transport in ultrathin films relevant to the realization of transparent and flexible electronic applications are explored based on thermodynamic material interaction principles in conjunction with optical and morphological studies. By blending the commodity polymer polystyrene (PS) with two high-performing polymers, PDPP3T and P (NDI2OD-T2) (known as N2200), a drastic difference in morphology and fiber network are observed due to considerable differences in the degree of thermodynamic interaction between the conjugated polymers and PS. Intrinsic material interaction behavior establishes a long-range intermolecular interaction in the PDPP3T polymer fibrillar network dispersed in the majority (80%) PS matrix resulting in a ca. 3-fold increased transistor hole mobility of 1.15 cm2 V-1 s-1 (highest = 1.5 cm2 V-1 s-1) as compared to the pristine material, while PS barely affects the electron mobility in N2200. These basic findings provide important guidelines to achieve high mobility in transparent OFETs.

Preparation of Nanocomposite-based High Performance Organic Field Effect Transistor via Solution Floating Method and Mechanical Property Evaluation.

We demonstrate that using nanocomposite thin films consisting of semiconducting polymer, poly(3-hexylthiophene) (P3HT), and electrochemically exfoliated graphene (EEG) for the active channel layer of organic field-effect transistors (OFETs) improves both device performances and mechanical properties. The nanocomposite film was developed by directly blending P3HT solution with a dispersion of EEG at various weight proportions and simply transferring to an Si/SiO2 substrate by the solution floating method. The OFET based on P3HT/EEG nanocomposite film showed approximately twice higher field-effect mobility of 0.0391 cm2·V−1·s−1 and one order of magnitude greater on/off ratio of ~104 compared with the OFET based on pristine P3HT. We also measured the mechanical properties of P3HT/EEG nanocomposite film via film-on-elastomer methods, which confirms that the P3HT/EEG nanocomposite film exhibited approximately 2.4 times higher modulus (3.29 GPa) than that of the P3HT film (1.38 GPa), while maintaining the good bending flexibility and durability over 10.0% of bending strain and bending cycles (1000 cycles). It was proved that the polymer hybridization technique, which involves adding EEG to a conjugated polymer, is a powerful route for enhancing both device performances and mechanical properties while maintaining the flexible characteristics of OFET devices.