Papers by Keyword: OTFT

Abstract: Global warming is a concern nowadays due to excessive release of harmful gasses to the environment, leading to greenhouse effect phenomena worldwide. Based on the data provided by global pollution agencies, the release of greenhouse gasses to the atmosphere is the main cause of pollution and the increase in atmospheric temperature due to warming. Greenhouse gasses (GHGs) contents released to the environment is worrying, with carbon dioxide (CO₂) is reported at the highest concentration compared to other gasses. There are many studies conducted to develop and evaluate the performance of harmful gas sensors incorporating inorganic and organic semiconductive materials. Organic semiconductors (OSCs) are environmentally friendly materials, relatively cheaper technology, and comprised of a wide range of materials with good carrier mobility. Therefore, in this work, Organic Thin Film Transistor (OTFT) is developed for gas sensor application. As global warming is becoming more serious, this solution is instead a sustainable solution to the environment, as organic molecules which are held together via Van der Waals bond are easily processed via low-temperature deposition and solution processing as compared to more complicated processes involved in conventional inorganic counterpart. In addition, the developed sensor is generally robust due to the ability to withstand high humidity conditions and can be fabricated on flexible substrates. In this work, suitable materials are identified in basic OTFT construction, which are the electrodes, dielectric and substrate. The scope is mainly focusing on the development of bottom gate OTFT construction, incorporating p-type active material which are Trisisopropylsilylethynyl Pentacene (TIPS Pentacene), Aluminium (Al) as drain and source electrodes, PEDOT: PSS as gate electrode and Polyvinyl alcohol (PVA) as gate dielectric. The materials in bottom gate bottom contact (BGBC) configuration, fabricated via screen printing technique is experimentally tested towards CO₂ detection. CO₂ is initially detected at 1618 ppm with contact resistance of 15 kΩ, and at 10 ml/minute flow rate, the developed configuration is demonstrated able to achieve sensitivity of 2.069 Ω/ppm. In conclusion, the studied BGBC OTFT has demonstrated suitability and applicability in CO₂ gas sensing for sustainable environmental condition monitoring, that could lead to safer environment for the living things on earth. With the proposed dimensions, in the future it is possible to proceed with this work to be fabricated by using more advanced techniques such as photolithography and many others.

Abstract: In order to detect OTFT small signal dynamic characteristics of weak current, we designed the detection circuit. The current detection range of the circuit is 10^-9～10^-6A, circuit bandwidth reaches 10kHz.According to the data tested by copper pthalocyanine thin organic static induction transistor we prepared, an equivalent circuit for simulating its dynamic performances was built and the factors influencing the performance of the device was investigated. The simulation results and actual test results are basically identical,which show the reliability of organic thin film transistor equivalent circuit model. In addition, through analyzing the model structure and the simulation results, the grid schottky junction capacitance and the device current intensity are the important factors in determining the dynamic properties of organic thin film transistor.

Abstract: The bottom contact heterojunction organic thin film transistors (OTFTs) based on n-type hexadecafluorophthalocyaninatocopper (F₁₆CuPc) and p-type copper phthalocyanine (CuPc) bilayer were developed by the vacuum evaporation, which were applied to detect nitrogen dioxide (NO₂). The sensors with different thickness (5nm, 10nm, 15nm and 20nm) of CuPc were prepared to investigate the influence of CuPc film thickness on the properties of devices. The results showed that four parameters including the source-drain current (I_DS), grid current (I_GS), threshold voltage (V_T) and carrier mobility (μ) changed in a few seconds when the sensors were exposed to the atmosphere of NO₂. Further more, I_DS and I_GS presented extremely similar variation trend. So the grid current would be taken as a new parameter to reveal the response characteristic of OTFT gas sensor. By comparison, the device with 15nm CuPc thin film exhibited the optimum electronic and gas sensing properties.

Abstract: The pure conducting polymer P3HT film is less sensitive to the formaldehyde (HCHO), and the pure ZnO film needs a high temperature to militate the HCHO, as a result, the P3HT/ZnO composite was fabricated on the organic thin film transistor (OTFT) by spraying to detect the HCHO at room temperature, the electrical properties and sensing properties of all the prepared OTFT devices were measured by Keithley 4200-SCS source measurement unit. What is more, the effect of different P3HT/ZnO composite masses on the response of sensors were tested, all the sensors showed a remarkable response to HCHO, and the optimized composite mass of 1.0ml was obtained. Since most detecting methods for the HCHO vapor require an high temperature, the experiments and results in this paper showed the important significance for the field of HCHO detecting.

Abstract: P-channel pentacene field effect transistorswith a Si/SiO₂/pentacene/Au structure were fabricated, and were gamma-ray irradiated with a Co⁶⁰ source. The changes of the drain current I_D vs. source/drain voltage V_SD (I_D - V_SD) characteristics were measured after every 200 Gy in silicon (Gy_Si) irradiations up to the total dose of 1200 Gy_Si. The drain current I_D continuously decreased to less than 10 % of that before irradiation after 1200 Gy_Si irradiation. The threshold voltage V_th continuously decreased up to 800 Gy_Si, started to saturate above 800 Gy_Si, and recovered above 1000 Gy_Si. The mobility m continued to decrease up to 1200 Gy_Si. Those behaviors were explained by accumulation of positive trapped charge within the gate insulator SiO₂ near the interface, continuous increase of interface traps near the interface between the SiO₂ and pentacene, and build up of electrons in the channel regions. These behaviors were discussed in comparisons with previously reported results on ultraviolet (UV) light irradiation experiments on similarly structured pentacene-based transistors.

Abstract: The manufacture of display device is a complex technology. To reach the flexible display like E-paper, many manufacture process such as driving electrode circuit and transistor must be combined with printing technology. From the information reported, the application of gravure prints technology in organic electronics; off-set printing in EMI film and screen technology in circuit are summarized. The study was more about ink jet print technology. It was described that ink jet was used in OLED (Organic light-emitting diode), OTFT (organic thin film transistor), polymer solar cell/ Flexible organic photovoltaic cell and so on. An OE-A (organic electronics application) roadmap for the charge carrier mobility of semiconductors for organic electronics applications was given. To achieve the printed circuit, the nano silver conductive ink was applied and the ink jet circuit surface was tested by microscopy, the conductive and flexible silver film was with many advantages than screen circuit. It was concluded that the printing electronic will play important roll in the display development.

Abstract: The gate, source, and drain electrodes of organic thin-film transistor(OTFT) to use as a switching device for a flexible display was fabricated in microcontact printing process with hard poly(dimethylsiloxane)(h-PDMS) stamp. The OTFT with thin-film dielectric layer of parylene-C(4300Å, 5000Å, 6500Å, 7500Å, and 9000Å) were formed using special coating system, and organic semiconductor layer was ink-jet printing process at room temperature. The microcontact printing process using self-assembled monolayer(SAM) and h-PDMS stamp made it possible to fabricate OTFT with channel length down to 600nm, fabricated thin film electrode of Au/Cr (100nm/5nm), and reduced the fabrication process by 20steps compared with photolithography process. Since the fabrication process was done in room temperature, there was no appeared such as pattern shrinkage, pattern transformation and bending problem.

Abstract: We report the effects of instability with gate dielectrics of pentacene thin film transistors (OTFTs) inverter circuits. We used to the UV sensitive curable resin and poly-4-vinylphenol(PVP) by gate dielectrics. The inverter supply bias is VDD= -40 V. For a given dielectric thickness and applied voltage, pentacene OTFTs with inverter circuits measurements field effect mobility, on-off current ratio, Vth. The field effect mobility 0.03~0.07 cm2/Vs, and the threshold voltage is -3.3 V ~ -8.8 V. The on- and off-state currents ratio is about 103~106. From the OTFT device and inverter circuit measurement, we observed hysteresis behavior was caused by interface states of between the gate insulator and the pentacene semiconductor layer.

Abstract: Using a thermally-crosslinkable organosiloxane-based organic-inorganic hybrid material, solution-processable gate dielectric layer for organic thin-film transistors (OTFTs) have been fabricated. The hybrid dielectric was synthesized by the sol-gel process. The surface of the prepared dielectric was modified by self-assembled monolayers (SAMs) treatment using wet chemical method. Prior to surface modification, the chemical inertness of prepared dielectric was investigated by immersing into various solvents such as toluene, acetone, isopropyl alcohol, and DI-water. The existence of SAMs on the surface of dielectric was confirmed by measuring current density-electric field characteristics and it was observed that surface morphology of SAMs-treated hybrid dielectric was very smooth.

Abstract: Pentacene channel for organic thin film transistor was deposited on the SiOC film by thermal evaporation. The growth of pentacene is related with the Diels-Alder reaction and the nucleophilic reaction by the thermal induction. The surface is an important factor to control the recursive Diels-Alder reaction for growing of pentacene on SiOC film. The terminal C=C double bond of pentacene molecule was broken easily as a result of attack of the nucleophilic reagents on the surface of SiOC film. The nucleophilic reaction can be accelerated by increasing temperature on surface, and it making pentacene to grow hardly on the SiOC film with a flow rate ratio of O2/(BTMSM+O2)=0.5 due to its inorganic property. The nucleophlic reaction mechanism is SN2 (bimolecular nucleophilic substitution) type.