Organic Field-Effect Transistors, Inverters, and Logic Circuits on Gate Electrets

2005 ◽  
Vol 889 ◽  
Author(s):  
Cheng Huang ◽  
James E. West ◽  
Howard E. Katz

ABSTRACTBy incorporating dielectrics with stored electric fields and organic semiconductors, new organic electronic components such as circuits with controlling voltages “restored” for transistor tuning can be developed. We have successfully used excellent electret materials including charged and surface-treated silicon dioxide (SiO2) and silsesquioxane (SSQ) polymers as the dielectric layer in organic field-effect transistors (OFETs). Charge injection and quasipermanent charge storage induce threshold voltage shifts and current modulation, which results from the built-in electric fields in the conduction channels. Static and dynamic characteristics of organic thin-film transistors (OTFTs) such as charging conditions and voltage/current retention were evaluated. In addition, self-assembled monolayers (SAMs) of dipolar molecules have been utilized in the dielectric layer, with different mechanisms but similar effects compared to charged dielectrics. We also present new OFET unipolar inverters, comprised of only two simple OTFTs with enhancement-mode driver and depletion-mode load to implement full-swing organic logic circuits for process simplification of electronic components in organic electronics.

2021 ◽  
Author(s):  
Suman Yadav ◽  
Shivani Sharma ◽  
Satinder K Sharma ◽  
Chullikkattil P. Pradeep

Solution-processable organic semiconductors capable of functioning at low operating voltages (~5 V) are in demand for organic field-effect transistor (OFET) applications. Exploration of new classes of compounds as organic thin-film...


2019 ◽  
Author(s):  
◽  
Amrit Prasad Laudari

In this research we study the role of ferroelectric dielectrics in organic field-effect transistors (FETs) to understand the mechanism of charge transport in organic semiconductors. The ferroelectric nature of the polymer, poly(vinylidene fluoride) (PVDF)), has been known for over 45 years. However, its role in interfacial transport in organic/polymeric FETs is not that well understood. PVDF and its copolymer, polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), as a dielectric in organic FETs is a perfect test-bed for conducting transport studies where a systematic tuning of the dielectric constant with temperature may be achieved. By choosing small molecule organic semiconductors -- pentacene and 6,13 bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) -- along with a copolymer PVDF-TrFE as the dielectric layer, the FET characteristics are monitored as a function of temperature. Pentacene FETs show a weak temperature dependence of the charge carrier mobility in the ferroelectric phase of PVDF-TrFE, which is attributed to polarization fluctuation driven transport resulting from a coupling of the charge carriers to the surface phonons of the dielectric layer. A negative coefficient of carrier mobility is observed in TIPS-pentacene upwards of 200 K with the ferroelectric dielectric, while an activated transport is observed with non-ferroelectric dielectrics. We show that this behavior is correlated with the nature of the trap states in TIPS-pentacene. We also developed the method of dipole engineering of the PVDF-TrFE films to enhance the properties of organic FETs. PVDF-TrFE, despite its applications in a vast range of work (including as a gate dielectric in organic FET and sensing applications) poses concerns such as higher conductivity compared to other polymer non-ferroelectric dielectrics. We have come up with new methods of electrical poling the dielectric layer to enhance FET performance as well as reduce gate leakage issues. We demonstrate the effect of polarization rotation in PVDF-TrFE on the performance of small-molecule-based organic FETs. The subthreshold swing and other transistor parameters in organic FETs can be controlled in a reversible fashion by switching the polarization direction in the PVDF-TrFE layer. We further demonstrate a novel method of selective poling of the dielectric layer. By using solution processed TIPS-pentacene as the organic semiconductor, it is shown that textured poling of the PVDF-TrFE layer dramatically improves FET properties compared to unpoled or uniformly poled ferroelectric films. The texturing is achieved by first vertically poling the PVDF-TrFE film and then laterally poling the dielectric layer close to the gate electrode. TIPS-pentacene FETs show on/off ratios of 105 and hole mobilities of 1 cm2/Vs under ambient conditions with operating voltages well below-4 V. This research opens prospects of achieving low-operating FETs without any expensive patterning techniques.


2016 ◽  
Vol 851 ◽  
pp. 189-193
Author(s):  
Stanislav Stříteský ◽  
Jozef Krajčovič ◽  
Martin Vala ◽  
Martin Weiter

Organic semiconductors are suitable for application in biosensors and sensors based on transistors. The influence of soluble group modifications on the performance of diketopyrrolopyrrole-based organic field-effect transistors (OFETs) is studied. The lowest mobility 1·10-9 cm2/Vs was observed for non-symmetric substitution O,N. Measurable charge carrier mobility was observed due to reduction of the density charge trapping states after application of organosilane self-assembled monolayers (SAMs) on thinner gate-dielectrics (90 nm). We report similar drift mobility 1·10-7 cm2/Vs for smallest soluble group “butyl” as for biggest group “EthylAdamantyl” in N,N and O,O substitution prepared by spin-coating.


2008 ◽  
Vol 92 (18) ◽  
pp. 183302 ◽  
Author(s):  
Kunjithapatham Sethuraman ◽  
Shizuyasu Ochiai ◽  
Kenzo Kojima ◽  
Teruyoshi Mizutani

2016 ◽  
Vol 2 (7) ◽  
pp. 1600046 ◽  
Author(s):  
Jimin Kwon ◽  
Yasunori Takeda ◽  
Kenjiro Fukuda ◽  
Kilwon Cho ◽  
Shizuo Tokito ◽  
...  

2020 ◽  
Vol 8 (44) ◽  
pp. 15759-15770
Author(s):  
Alexandra Harbuzaru ◽  
Iratxe Arrechea-Marcos ◽  
Alberto D. Scaccabarozzi ◽  
Yingfeng Wang ◽  
Xugang Guo ◽  
...  

Different charge transport mechanisms at the device interface are found for a series of ladder-type semiconductors with increasing chain length.


2019 ◽  
Vol 31 (1) ◽  
pp. 265-273 ◽  
Author(s):  
Seema Barard ◽  
Debdyuti Mukherjee ◽  
Sujoy Sarkar ◽  
T. Kreouzis ◽  
I. Chambrier ◽  
...  

AbstractSpin-coated 52-nm-thick films of newly synthesised gadolinium liquid crystalline bisphthalocyanine sandwich (GdPc2) complexes with octyl chains non-peripheral positions have been successfully employed as active layers for bottom-gate organic field effect transistors having both short $$(5\,\upmu {\text{m}})$$(5μm) and long $$( 20\,\upmu {\text{m}})$$(20μm) channels. The scaling down of the channel length $$( L )$$(L) decreases the field effect mobility due to the increase in the contact resistance between the gold electrodes and the GdPc2 semiconducting layer. Values of on–off ratio and sub-threshold voltage swing are higher nearly one order of magnitude for $$L = 5 \,\upmu{\text{ m}}$$L=5μm than those for $$L = 20\;\upmu m$$L=20μm.


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