An original design and photolithographic fabrication process for Poly (3-hexylthiophene-2, 5-diyl) (P3HT) based Organic thin-film transistors (OTFTs) is presented. The structure of the transistors was based on the bottom gate bottom contact OTFT. The fabrication process was efficient, cost-effective, and relatively straightforward to implement. Most of the fabrication steps were performed at room temperature and atmospheric pressure, with the only exceptions being the high temperatures used for annealing the films and the low pressures used for depositing the metal contacts. More than 226 transistors were fabricated on a single wafer. The electrical characteristics and the geometry of the transistors were consistent across the wafer. Current–voltage (I–V) and atomic force microscopy (AFM) measurements were performed to characterize the primary electronic properties of the transistors and morphology of the P3HT, respectively. Two key performance parameters were extracted from these measurements, the threshold voltage and the field-effect mobility of the transistors. The measured mobility of these transistors was significantly higher than most results reported in the literature for other similar bottom gate bottom contact P3HT OTFTs. The higher mobility is explained primarily by the effectiveness of the fabrication process in keeping the interfacial layers free from contamination, as well as the annealing of the P3HT.

Stability of Polymer Tantalum capacitors with pre-polymerized PEDOT (slurry PEDOT) cathodes were investigated under different environmental conditions. Capacitance dependence on temperature, frequency, and dc bias voltage were investigated in humid and dry capacitors with different dielectric thicknesses. Electrical measurements and scanning electron microscopy (SEM) were used to characterize the capacitors. Humid capacitors were observed to have higher capacitance than dry capacitors for all dielectric thicknesses. The capacitance for all dielectric thicknesses was observed to increase with temperature in both humid and dry capacitors. Humid capacitors showed a strong temperature dependence at lower temperatures while dry capacitors showed a strong temperature dependence at higher temperatures. These temperature effects were more pronounced in thinner dielectric capacitors, and the results were explained by the integrity of the dielectric-polymer interface. The capacitance for all dielectric thicknesses was also observed to decrease with an increase in frequency, both in humid and dry capacitors. The frequency effect was more pronounced in humid capacitors with thinner dielectrics. These results were explained by a distributed capacitance model, secondary transitions of the polar segments of the polymer cathode, and lower reactance and lower self-resonance frequency of the thinner dielectric capacitors. The technological principles of improving environmental stability of Polymer Tantalum capacitors are also discussed.

The effects of adding a copolymer interfacial layer on the performance of Poly (3-hexylthiophene-2, 5-diyl) (P3HT) based organic thin-film transistors (OTFT) were investigated. Poly (oligo (ethylene glycol) methyl ether methacrylate- glycidyl methacrylate- lauryl methacrylate), which is referred to as POGL, was used as an interfacial layer between P3HT and the dielectric. OTFTs with and without a POGL interfacial layer were fabricated. The field-effect mobility and the threshold voltage were extracted for all the devices. The OTFTs with a POGL interfacial layer were observed to have a smaller threshold voltage than the OTFTs without an interfacial layer, which makes the POGL devices attractive for low power applications. The POGL OTFTs were also observed to have much more ideal drain current saturation characteristics with very small I-V curve slope. This is explained by the deep trap states on the POGL surface and the reduction of the contact resistance at the electrode/organic semiconductor interface. However, the POGL OTFTs were observed to have a smaller drain current and a slightly smaller mobility than the non-POGL OTFTs. This is explained by the surface roughness of the POGL, which affects the charge transport in the channel of the device.

No abstract

We fabricated and characterized poly(3-hexylthiophene-2, 5-diyl) (P3HT)-based Organic thin-film transistors (OTFTs) containing an interfacial layer made from virgin Graphene Oxide (GO). Previously chemically modified GO and reduced GO (RGO) were used to modify OTFT interfaces. However, to our knowledge, there are no published reports where virgin GO was employed for this purpose. For the sake of comparison, OTFTs without modification were also manufactured. The structure of the devices was based on the Bottom Gate Bottom Contact (BGBC) OTFT. We show that the presence of the GO monolayer on the surface of the OTFT's SiO2 dielectric and Au electrode surface noticeably improves their performance. Namely, the drain current and the field-effect mobility of OTFTs are considerably increased by modifying the interfaces with the virgin GO deposition. It is suggested that the observed enhancement is connected to a decrease in the contact resistance of GO-covered Au electrodes and the particular structure of the P3HT layer on the dielectric surface. Namely, we found a specific morphology of the organic semiconductor P3HT layer, where larger interconnecting polymer grains are formed on the surface of the GO-modified SiO2. It is proposed that this specific morphology is formed due to the increased mobility of the P3HT segments near the solid boundary, which was confirmed via Differential Scanning Calorimetry measurements.