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Graphical abstract Highlights • Poly(vinyl alcohol) (PVA) dielectric films were cross-linked with N,N' -methylene bisacrylamide (MBA) at 100 ℃. • Cross-link significantly improved the dielectric properties of the thin-films. • Surface passivation with a cross-linked PMMA film reduced surface hydrophilicity of PVA dielectrics. • Average mobility of 0.43 cm2V−1s−1 were achieved in solution processed OFET devices with TIPS-pentacene as active layer. Abstract Poly(vinyl alcohol) (PVA) thin-films were cross-linked by N,N' -methylene bisacrylamide (MBA) in a thermal induced radical process at 100℃. The cross-link improved the dielectric properties of PVA thin-films. The effect of surface passivation by cross-linked polymethyl methacrylate (PMMA) thin-films on the electrical properties and the surface characteristics of the PVA gate dielectrics were also investigated. The surface passivation layer significantly reduced surface hydrophilicity and improved the morphology of semiconductor layers. The bilayer dielectrics were applied in solution processed OFET devices with a bottom-gate bottom-contact structure. [ABSTRACT FROM AUTHOR]

This letter realizes both large gate dielectric capacitance and reduced sub-gap density of states at the channel in the same organic field effect transistor (OFET) structure by adopting optimized low-k/high-k bilayer gate dielectric. Subthreshold swing (SS) as small as 64 mV dec ^-1 can be achieved with a thick (>360 nm) gate dielectric layer. This is the smallest SS value reported so far for all reported low voltage OFETs, and is even comparable with that of 22 nm technology node Si-FETs. The device can thus be switched within a very small voltage swing of 0.8 V, while having an ON/OFF ratio larger than 105. The device also shows excellent operational and storage stabilities. [ABSTRACT FROM PUBLISHER]

Low-voltage organic-field effect transi-stors (OFETs) using relaxor ferroelectric polymer poly (vinylidene fluoridetrifluoroethylene-chlorofloroethylene) P (VDF-TrFE-CFE)) were fabricated. The measured hysteresis loop and the threshold voltage shift under negative bias stress (NBS) are opposite to that of the reference device using low- k CYTOP gate dielectric layer, in which the hysteresis and NBS-induced instabilities are explained by gate bias-induced charge trapping. The anomalous behaviors in the P (VDF-TrFE-CFE) OFETs are attributed to the stress-induced remnant polarization in P (VDF-TrFE-CFE), which induces additional mobile charges into the channel. By adding a thin CYTOP layer between the P (VDF-TrFE-CFE) layer and the semiconductor layer, the two effects of charge trapping and remnant polarization under gate bias are found to be neutralized with each other, resulting in low-voltage OFETs of negligible hysteresis and excellent NBS stability. [ABSTRACT FROM PUBLISHER]

Attributed to its advantages of super mechanical flexibility, very low-temperature processing, and compatibility with low cost and high throughput manufacturing, organic thin-film transistor (OTFT) technology is able to bring electrical, mechanical, and industrial benefits to a wide range of new applications by activating nonflat surfaces with flexible displays, sensors, and other electronic functions. Despite both strong application demand and these significant technological advances, there is still a gap to be filled for OTFT technology to be widely commercially adopted. This paper provides a comprehensive review of the current status of OTFT technologies ranging from material, device, process, and integration, to design and system applications, and clarifies the real challenges behind to be addressed. [ABSTRACT FROM AUTHOR]

By reducing the sub-gap density of states at the channel, an all solution processed low-voltage organic field-effect transistor (OFET) was realized on a micrometer-thick SU8 gate dielectric layer. The device exhibits excellent operational stability under continuous bias stress. An integrated pH sensor tag was fabricated based on this low-voltage OFET, using an extended gate OFET for sensing and the other OFET as the load to convert the current signal to a voltage output for easy design of the subsequent readout circuit. With the low-voltage operation behavior and excellent operational stability of the OFET, the sensor tag was demonstrated to be operated in a 3.3 V battery powered electronic system for reliable pH sensing. [ABSTRACT FROM PUBLISHER]

To achieve low-voltage organic thin-film transistors (OTFTs) with printing or coating processes over large area, a thick gate dielectric layer is preferred. Taking this into consideration, a common solution for low-voltage OTFTs is using large-permittivity (high-k) dielectric material to enlarge the gate dielectric capacitance. Our recent work shows that reducing the subgap density of states (DOS) at the channel can also help to achieve low-voltage OTFTs. This approach does not need large gate dielectric capacitance, and thus a low-k and thick gate dielectric layer can be used. In this work, device/circuit mixed-mode simulations are carried out to compare the performance of the two type low-voltage OTFTs as switches in active-matrix backplanes. It is shown that the low-voltage OTFT with reduced subgap DOS can achieve faster charging and discharging. The less parasitic and storage capacitance with the low-k dielectric layer would also reduce the required dynamic power. [ABSTRACT FROM PUBLISHER]

Threshold voltage (Vth) control using different metal gates (aluminum and gold) was applied to realize dual- Vth low-voltage solution processed organic thin film transistors (OTFTs). In the devices, the low-operation voltage was realized based on a channel engineering approach instead of using large gate dielectric capacitance, therefore, a relatively thick and low-dielectric constant polymer dielectric layer can be used. The devices present a mobility about 1.0 cm^2/(V\cdots) , ON/OFF ratio of 10^5 and small subthreshold swing of 100 mV/decade with the maximum processing temperature not exceeding 100 ^\circC . It was found that, even with a 400-nm thick polymer dielectric layer, since possible charge trapping effects was effectively suppressed by the crosslinking processes, well controlled Vth was achieved. Both unipolar single- Vth and dual- Vth inverters were fabricated, clearly showing the influence of Vth on the circuit operation and improved performance with the dual- Vth OTFT technology. [ABSTRACT FROM AUTHOR]

In this paper, all-solution-processed low-voltage (<3~V) organic thin-film transistor inverters on polyethylene naphthalate plastic substrate were achieved in the bottom-gate bottom-contact device configuration. In the devices, 6,13-bis(triisopropylsilylethynyl)-pentacene blended with polystyrene was used as the channel layer, and ultraviolet cross-linked polyvinyl alcohol was used as the gate dielectric layer. With optimized inkjet jetting process parameters and a proper polymer dielectric substrate surface, fine silver electrodes were formed as the source, drain, and gate electrodes. The maximum processing temperature was 150^\circC. The devices show promising performance with a mobility of 0.8 cm^2/(V\cdots), a subthreshold swing of 100 mV/decade and an ON/OFF ratio of about 10^4. The fabricated diode-load inverter has a high dc voltage gain up to 67.3 at a supply voltage of 3 V. [ABSTRACT FROM AUTHOR]

Solution-processed low-voltage organic thin-film transistors (OTFTs) were fabricated using the high-mobility donor–acceptor copolymer semiconductor indacenodithiophene-co-benzothiadiazole (IDTBT) and large permittivity (high- k ) relaxor ferroelectric polymer poly (vinylidene fluoride-trifluoroethylene-chlorofloroethylene). It is shown that, with the face-on molecule packing in as-deposited IDTBT films, the close interfacing between the backbone and the dielectric layer causes significant mobility degradation of the fabricated OTFTs due to dipole effects. By inserting a thin, low-polar dielectric layer between the high- k one and the channel, the dipole field can be effectively screened and the devices present a high mobility similar to that of previously reported high-voltage IDTBT OTFTs. With the bilayer gate dielectric and the IDTBT semiconductor, low-voltage OTFTs are achieved with the average mobility of 1.4 cm ^\mathrm \mathbf 2/\textV\,\cdot s and ON/OFF-current ratio larger than 10^6 , which is among the best reported performance so far for solution processed low-voltage OTFTs. [ABSTRACT FROM AUTHOR]

Photolithographic and dry-etching processes are developed to pattern the organic semiconductor (OSC) layer for top-gate organic thin-film transistors (OTFTs). A fluorine polymer layer is used to protect the OSC surface from the patterning processes so that the common photoresist can be used. The ON/OFF-current ratios of the patterned OTFTs are improved by about one order of magnitude compared with that of unpatterned devices. However, it is shown that removing the polymer protective layer can cause degraded subthreshold behavior due to increased interface trap density at the semiconductor/dielectric interface. A process without removing the polymer protective layer is thus developed to address this issue, and is shown to be able to provide a reliable route to achieve patterned top-gate OTFTs with high ON/OFF-current ratio, small subthreshold swing, and negligible hysteresis. [ABSTRACT FROM PUBLISHER]