Highly stable fluorine-rich polymer treated dielectric surface for the preparation of solution-processed organic field-effect transistors

Highly stable fluorine-rich polymer dielectrics were fabricated using cross-linked poly(3-(hexafluoro-2-hydroxyl) propyl) styrene (PFS), which shows excellent electrical stability, good adhesive surface properties, and good wettability on deposited solution-processed materials. Solution-processed triethylsilylethynyl anthradithiophene (TES-ADT) could be deposited onto the cross-linked PFS dielectrics to yield highly ordered crystalline structured films that did not delaminate. The field-effect mobilities were as high as 0.56 cm(2) V-1 s(-1), and negligible hysteresis was observed in the organic field-effect transistors (OFETs). The threshold voltage, the ON/OFF ratio, and the subthreshold slope were -0.043 V, similar to 10(7), and -0.3 V per decade, respectively. The OFETs demonstrated excellent device reliability under gate-bias stress conditions due to the presence of highly stable fluorine groups in the cross-linked PFS dielectrics.X112523sciescopu

Reduced water vapor transmission rates of low-temperature-processed and sol-gel-derived titanium oxide thin films on flexible substrates

Sol-gel-derived, crack-free, and condensed TiOx thin films with improved barrier properties were successfully fabricated on polymeric substrates with a simple two-step heat treatment at low temperatures. To assess the barrier properties of the TiOx thin films, Ca corrosion tests were conducted and their water vapor transmission rates (WVTRs) were measured. We found that the two-step heat treatment (at 45 degrees C for 90 min and 110 degrees C for 60 min) produces a close-packed TiOx structure that substantially reduces the WVTRs of the coated polymeric substrates. The WVTRs of 86 nm thick TiOx thin films on polyethylene naphthalate (PEN) substrates at a relative humidity (RH) of 90% were found to be 0.133 g m(-2) day(-1) at 38 degrees C and 0.0387 g m(-2) day(-1) at 25 degrees C. In addition, the WVTR value of the TiOx thin films on PEN substrates are stable with respect to bending: it was found to increase by only similar to 13% after 100 repetitions of bending with a 20 mm radius. (C) 2016 Elsevier B.V. All rights reserved.1153sciescopu

Synthesis and characterization of a fluorinated oligosiloxane-containing encapsulation material for organic field-effect transistors, prepared via a non-hydrolytic sol–gel process

The operation of stable organic field-effect transistors (FETs) over long periods of time requires that organic FETs are encapsulated. We synthesized an inorganic-organic hybrid non-hydrolytic sol-gel material (TPDt) containing fluoroalkyl functional groups to encapsulate organic FETs. Fourier-transform infrared spectroscopy, atomic force microscopy, UV-Visible spectroscopy, and water contact angle measurements demonstrated that the TPDt films displayed smooth surfaces, good hydrophobicity, and optical transparency. The gas barrier properties of the TPDt films were tested by fabricating FETs using an organic semiconductor, poly[9,9-dioctylfluorenyl-2,7-diyl]-co-(bithiophene)]. The organic FETs were operated at 38 degrees C in the presence of a 90% relative humidity air atmosphere. The field-effect mobility of the organic FET decreased only negligibly, even after 2500 h operation under these conditions. (C) 2012 Elsevier B.V. All rights reserved.X111110sciescopu

A composite of a graphene oxide derivative as a novel sensing layer in an organic field-effect transistor

We report the fabrication of a gas sensor with an oleylamine-modified graphene oxide (OA-GO)/poly(9-9???-dioctyl-fluorene-co-bithiophene) (F8T2) composite as an active layer and demonstrate that it has better sensing ability than a comparable device with an F8T2-only active layer. OA-GO was chosen as the receptor material because of its enhanced interaction with gas analytes and its easy mixing with F8T2. OA-GO was synthesized by a simple condensation reaction between GO and oleylamine (9-octadecylamine), and characterized by Fourier transform infrared spectroscopy. The sensitivities of the gas sensors with respect to acetone and ethanol analytes were investigated by measuring the electrical parameters of the corresponding organic field effect transistor at room temperature. The sensitivity of the OA-GO/F8T2 composite device was up to 34 times that of the F8T2 device for the mobility change of acetone.close2

Light-responsive spiropyran based polymer thin films for use in organic field-effect transistor memories

Light-responsive spirotype compounds have been receiving attention as attractive smart materials because of their various potential applications in organic optoelectronic devices, based on organic field-effect transistors (OFETs). However, it still remains a challenge to apply the organic flash memory devices using spirotype compounds due to the relatively poor development of new photosensitive electret materials. Here, we report the synthesis of a novel photosensitive polymer electret material, spiropyran, containing poly(3,5-benzoic acid hexafluoroisopropylidene diphthalimide) (6FDA-DBA-SP), and the development of light-responsive flexible memory devices using the 6FDA-DBA-SP electret layer. The charge trapping properties of 6FDA-DBA-SP under light illumination were enhanced by the electron withdrawing properties and lowering energetic barrier of charge trapping between 6FDA-DBA-SP and pentacene analysed by measuring the electronic structures at the pentacene/6FDA-DBA-SP interfaces. The resulting OFETs showed enlarged hysteresis under white-light illumination and exhibited bi-stable current states after the light-assisted programing and erasing processes, and they were utilized in non-volatile flexible memory device applications.11105sciescopu

Al2O3/TiO2 nanolaminate gate dielectric films with enhanced electrical performances for organic field-effect transistors

Nanolamination has entered the spotlight as a novel process for fabricating highly dense nanoscale inorganic alloy films. OFET commercialization requires, above all, excellent dielectric properties of gate dielectric layer. Here, we describe the fabrication and characterization of Al-O-Ti (AT) nanolaminate gate dielectric films using a PEALD process, and their OFET applications. The AT films exhibited a very smooth surface (R-q < 0.3 nm), a high dielectric constant (17.8), and a low leakage current (8.6 x 10(-9) A/cm(2) at 2 MV/cm) compared to single Al2O3 or TiO2 films. Importantly, a 50 nm thick AT film dramatically enhanced the value of mu(FET) (0.96 cm(2)/V) on a pentacene device, and the high off-current level in a single TiO2 film was effectively reduced. The nanolamination process removes the drawbacks inherent in each single layer so that the AT film provides excellent dielectric properties suitable for fabricating high-performance OFETs. Triethylsilylethynyl anthradithiophene (TES-ADT), a solution-processable semiconductor, was combined with the AT film in an OFET, and the electrical properties of the device were characterized. The excellent dielectric properties of the AT film render nanolamination a powerful strategy for practical OFET applications. (C) 2015 Elsevier B.V. All rights reserved.112014sciescopu

Al₂O₃/TiO₂ Nanolaminate Thin Film Encapsulation for Organic Thin Film Transistors via Plasma-Enhanced Atomic Layer Deposition

Organic electronic devices require a passivation layer that protects the active layers from moisture and oxygen because most organic materials are very sensitive to such gases. Passivation films for the encapsulation of organic electronic devices need excellent stability and mechanical properties. Although Al₂O₃ films obtained with plasma enhanced atomic layer deposition (PEALD) have been tested as passivation layers because of their excellent gas barrier properties, amorphous Al₂O₃ films are significantly corroded by water. In this study, we examined the deformation of PEALD Al₂O₃ films when immersed in water and attempted to fabricate a corrosion-resistant passivation film by using a PEALD-based Al₂O₃/TiO₂ nanolamination (NL) technique. Our Al₂O₃/TiO₂ NL films were found to exhibit excellent water anticorrosion and low gas permeation and require only low-temperature processing (<100 °C). Organic thin film transistors with excellent air-stability (52 days under high humidity (a relative humidity of 90% and a temperature of 38 °C)) were fabricated