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A new and exciting pattern transfer method is presented to enhance the photoconductivity of Ag/CSA-PANI/PMMA/ITO, organic field effect transistor (OFET) by employing soft-lithography based grating over the channel region. The light is diffracted by the 265 nm gratings to enhance the UV (365 nm) activity of the channel material. The electrical characteristics of the grating-based OFET exhibited p-channel properties with the saturated hole mobility and the threshold voltage of ∼9.5 × 10 −5 cm 2 /V-s and ∼ −1.72 V respectively. The photo-generated charge carriers strongly influence the drain current in comparison to the dark condition. The External Quantum Efficiency of ∼2.45 × 10 5 establishes the photo-multiplication as a dominant factor for enhancement of the drain current. Moreover, the fabricated grating based OFET exhibited high photo-sensitivity and photo-responsivity of ∼1.16 × 10 2 and ∼7.33 × 10 4 A/W, respectively. Thus, the proposed soft-lithography grating based Ag/CSA-PANI/PMMA/ITO, OFET is an exceptional candidate for phototransistor applications. [ABSTRACT FROM AUTHOR]

High-quality rubrene crystals were directly grown on a polymeric gate dielectric-coated ITO/glass substrate by a simple solution process. Organic field-effect transistors were fabricated based on these rubrene crystals, and their electrical performance was investigated. Atomic force micrographs of the rubrene crystal reveal that its surface has a conventional terrace structure, confirming the well-ordered rubrene molecules. The organic transistor with the rubrene crystal shows the highest charge carrier hole mobility of 3.74 cm 2 /V·s that can be attributed to the strong π-π overlap between the adjacent rubrene molecules. The device shows a stable static and dynamic electrical stress response under ambient conditions. For evaluating the applicability of the transistor in a logic circuit, a simple load-type inverter is fabricated by combining the rubrene transistor and a 10 MΩ load-resistor, to achieve a clear dynamic switching response up to 100 Hz. [ABSTRACT FROM AUTHOR]

In this paper, organic light-emitting field effect transistors (OLEFETs) operating at low voltages | V op | below 10 V were first produced and characterized. n -Dodecylphosphonic acid (PA-C12)-self-assembled monolayer (SAM)-passivated HfO x dielectrics prepared using sol-gel chemistry decreased the device-operating voltages. Crystalline organic active layers of pentacene and N,N ′-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (P13) acted as p -and n -type materials, respectively. 4-(dicyanomethylene)-2-methyl-6-( p -dimethylaminostyryl)-4H-pyran doped onto a tris(8-hydroxyquinoline) aluminum (Alq 3 :DCM) layer was used as a light-emitting medium to enhance the luminescence efficiency. Based on a tri-layered structure with balanced ambipolar transports and the combined high capacitance-low leakage current of the PA-C12-SAM-treated HfO x dielectrics, the OLEFETs demonstrated good device performance with light emission at | V op | < 10 V. The transistor characteristics and operating light-emission mechanisms were discussed based on the EL images acquired using a charge-coupled device (CCD) camera under ambient conditions. [ABSTRACT FROM AUTHOR]

Environmental stability is one of the most important parameters for high-performance organic field-effect transistors (OFETs). Hydrophobic insulators usually possess much better air stability than some conventional inorganic and hydrophilic organic insulators. However, fabrication of devices with high integration by photolithography method cannot be directly performed on hydrophobic insulators due to their photoresist-unwettable properties. In this work, a simple yet efficient metal-assisted photolithography method is developed to achieve large-scale fabrication of highly integrated organic electronic devices on photoresist-unwettable insulators. By using copper (Cu) as sacrificial layer, photolithography can be performed on these insulators with nearly the same resolution, uniformity, and reproducibility as the conventional photolithography. This method shows excellent flexibility and is capable of fabricating high-integrated devices on a variety of hydrophobic insulators including hydrophobic amorphous fluoropolymer (CYTOP), poly(dimethylsiloxane) (PDMS), and octadecyltrichlorosilane (OTS)-modified SiO 2 . OFETs based on 6,13-dichloropentacene (DCP) microwires (MWs) with CYTOP as the insulator layer were fabricated, which exhibited excellent device performance. Much improved device stability with very low mobility degradation (less than 9%) was observed after 24 days. While devices fabricated on hydrophilic insulators of poly-(vinyl phenol) (PVP) and bare SiO 2 experienced dramatic performances decay within 24 days. Furthermore, by using metal-assisted photolithography method, flexible OFETs arrays could be further fabricated on polyethylene naphthalate (PEN) substrate, which showed excellent mechanical bending flexibility and stability. This work unveils the great potential of metal-assisted photolithography method for long-term stable high-integration organic electronic devices. [ABSTRACT FROM AUTHOR]

Flexible organic field-effect transistors (OFETs) with TIPS-pentacene: polystyrene (PS) blend are demonstrated to exhibit enhanced mobility and significantly improved electrical stability compared to neat TIPS-pentacene on poly(4-vinylphenol) (PVP) dielectric (bi-layer OFETs), along with high mechanical stability. Due to merit of high quality dielectric-semiconductor interface, pristine TIPS-pentacene: PS blend OFETs exhibited maximum mobility of 0.93 cm 2 V −1 s −1 with average of 0.44(±0.25) cm 2 V −1 s −1 compared to 0.14(±0.10) cm 2 V −1 s −1 for bi-layer OFETs with high current on-off ratios on the order 10 5 for both. Both types of devices exhibited high electrical stability upon bending with increasing magnitude of strain or its duration up to 5 days. However, significant differences in electrical stability of devices were observed upon applying constant bias-stress for 40 min to 1 h. Pristine blend devices exhibited outstanding electrical stability with very low drain current decay of <5% compared to ∼30% for bi-layer devices. Even upon bias-stress after 5 days of bending, the drain current decay levels were only changed to <10% and ∼50% for blend and bi-layer devices respectively. [ABSTRACT FROM AUTHOR]

Organic molecular crystals (OMCs) are of significant interest due to their potential use in transistors, photovoltaic devices, light emitting diodes, and other applications. However, conventional vacuum-based methods of growing crystalline OMC films are costly and provide limited control over crystal growth. In this study, we present a new method for preparing high performance single-crystal tetracene field-effect transistors under near-ambient conditions using organic vapor-liquid-solid (OVLS) deposition. We find that the mobility of OVLS-grown tetracene is comparable to high quality crystalline films prepared by physical vapor deposition. These results establish OVLS deposition as a relatively low cost, low substrate temperature, and ambient pressure method for growing high quality OMC films for device applications. [ABSTRACT FROM AUTHOR]

In this paper, we used the low and high density porous structure of polymethylmethacrylate (PMMA) film as tunneling dielectric layer in the floating-gate organic field-effect transistor (OFET) memory devices. Compared to the thin/thick nonporous structure of PMMA tunneling layer, the porous structure of PMMA tunneling layer had positive impacts on the device performance of the floating-gate OFET memory devices. Moreover, it was found that the memory performance was also increased as pore density of PMMA film increased. The atomic force microscopy (AFM) results of both porous structure of PMMA film and pentacene film on porous structure of PMMA film revealed that high density porous structure of PMMA tunneling layer can produce larger tunneling area and more electron transfer paths between pentacene film and PMMA film, which resulted in high electron capture and release efficiency of the floating-gate OFET memory devices with porous structure of PMMA tunneling layer. In addition, our porous structure of PMMA tunneling layer as well as nonporous PMMA film has high electrical insulating property due to their semi-hollow structure film, which is favourable to maintain stable retention property. Eventually, the floating-gate OFET memory devices with high density porous structure of PMMA tunneling layer showed good nonvolatile memory properties with a large memory window of about 43 V, a high ON/OFF current ratio of about 10 4 , and stable endurance and retention properties. Our results provided a new strategy to achieve the high performance floating-gate OFET memory devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] Aligned organic field-effect transistors were fabricated on flexible substrate. [•] Flexible OFETs exhibited mobility up to 2.0cm2 V−1 s−1. [•] The flexible OFETs showed excellent bend stability with bending radius of 3mm. [Copyright &y& Elsevier]

Highlights: [•] We investigated these effects of the interface on the top channel established by Cytop™ and poly(3-hexylthiophene) (P3HT). [•] Controlling roughness of P3HT film renders the transistor to have the mobility of 0.12cm2/Vs in top-gate device. [•] The control of channel roughness and interfacial properties is a critical key in organic transistors. [Copyright &y& Elsevier]