Dependence of the mobility on charge carrier density and electric field in poly(3-hexylthiophene) based thin film transistors: Effect of the molecular weight

Fumagalli, Luca; Binda, Maddalena; Natali, Dario; Sampietro, Marco; Salmoiraghi, E.; Gianvincenzo, Paolo Di

doi:10.1063/1.3003526

Cited by 43 publications

(30 citation statements)

References 28 publications

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“…This phenomenon is a consequence of: (1) a reduction in grain boundaries as channel length is reduced and approaches the size of microcrystals; and (2) a shorter trapping time by a reduction in barrier height. 24 The latter is a result of the Poole-Frenkel effect, which is generated by an increase on the planar electric field from source to drain. Charge carrier mobility in these TFTs are comparable to previously reported results, 10,11,25 but the low operating voltage indicates a possibility to function in aqueous media for sensing applications such as medical diagnosis and beverage evaluation by electronic tongues.…”

Section: Thin-film Transistor Performance Analysismentioning

confidence: 99%

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Cavallari

Zanchin

Pojar

et al. 2014

Journal of Elec Materi

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A low-cost patterning of electrodes was investigated looking forward to replacing conventional photolithography for the processing of low-operating voltage polymeric thin-film transistors. Hard silicon, etched by sulfur hexafluoride and oxygen gas mixture, and flexible polydimethylsiloxane imprinting molds were studied through atomic force microscopy (AFM) and field emission gun scanning electron microscopy. The higher the concentration of oxygen in reactive ion etching, the lower the etch rate, sidewall angle, and surface roughness. A concentration around 30 % at 100 mTorr, 65 W and 70 sccm was demonstrated as adequate for submicrometric channels, presenting a reduced etch rate of 176 nm/min. Imprinting with positive photoresist AZ1518 was compared to negative SU-8 2002 by optical microscopy and AFM. Conformal results were obtained only with the last resist by hot embossing at 120°C and 1 kgf/cm 2 for 2 min, followed by a 10 min post-baking at 100°C. The patterning procedure was applied to define gold source and drain electrodes on oxide-covered substrates to produce bottom-gate bottom-contact transistors. Poly(3-hexylthiophene) (P3HT) devices were processed on high-j titanium oxynitride (TiO x N y ) deposited by radiofrequency magnetron sputtering over indium tin oxide-covered glass to achieve low-voltage operation. Hole mobility on micrometric imprinted channels may approach amorphous silicon ($0.01 cm 2 /V s) and, since these devices operated at less than 5 V, they are not only suitable for electronic applications but also as sensors in aqueous media.

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Section: Thin-film Transistor Performance Analysismentioning

confidence: 99%

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Cavallari

Zanchin

Pojar

et al. 2014

Journal of Elec Materi

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“…[62] , which showed that by careful design and measurement procedures it is possible to extract both charge density and electric-field dependence of the mobility. In this paper, they used the model by Roichman et al [24] or its concepts, which account also for electric-field dependence, to explain the physical picture.…”

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confidence: 99%

Charge Transport in Disordered Organic Materials and Its Relevance to Thin‐Film Devices: A Tutorial Review

et al. 2009

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In this review, we describe a variety of models or theoretical approaches to transport in disordered media and discuss the implication to modern organic devices. There are far too many models or variations, so our aim is not to try to cover them all. Instead, we show that when the different models are presented along with the assumptions included while being developed, they can all teach us and help us to develop some intuition regarding what goes on in nonordered materials. One may encounter debates regarding a model being wrong, but it is our belief that only when the models are used out of context (not within their basic assumptions) the obtained results could be false.One of the things one encounters while starting to study organic semiconductors is that the textbook models taught in semiconductor-device courses have to be revisited, and one has to look for ''old'' books that were written before silicon technology took over. With this spirit, we start a few years back, or a century ago. In 1900, three years after the discovery of the electron by Thomson, Drude proposed a model that explained the known conductivity phenomenon in metals and other types of materials.[1] This model was based on the assumption that electrons classically accelerate under an applied electric field and collide with the lattice's heavy positive ions. Upon collision, the electrons were assumed to scatter into a random angle and at a speed that was on average consistent with the local temperature. It would then go on accelerating until the next scattering event. This model, although erroneous in the assumption that the basic scattering centers were the lattice ions, was able to physically explain the already known Ohm's law and the Joule heating effect. Along with the debut of quantum mechanics came the quantum mechanical description of matter and the realization that in a well-ordered lattice electrons should be mathematically described as Bloch waves, and that the scattering was not the result of collisions with any lattice ion but rather scattering from defects, contaminations, and phonons. Nevertheless, the Drude model, under the semiclassical approximation, is conceptually appropriate for describing electron transport through crystal lattices, that is, freely roaming charge carriers that scatter upon collisions with defects, contaminations, and phonons. The carriers earn the name ''free'' whenever the material properties are such that the mean free path between collisions, L, is much longer than the typical carrier's Bloch wavelength, thus the carriers have very broad wavefunctions extending over many lattice units.However, as was historically elucidated by Anderson, [2] introducing disorder into the lattice and breaking the crystal symmetry results in the wavefunctions becoming localized and in the formation of energy states in the forbidden band-gap. The Drude concepts, and others deriving on its intuitive approach, can no longer serve us in explaining transport under such circumstances. Since the materials we are interested in a...

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“…These studies indicate that the DOS takes a more complicated form than a simple Gaussian but are in substantial agreement with the experimental fitting (see Figure 2). [29,32,33] The evaluation of the DOS using computational chemistry methods involves the evaluation of the nuclear conformations visited by the system at a given temperature [obtained from molecular dynamics (MD) simulations] and the evaluation of the orbital energy from quantum chemistry (QC) calculations of MD snapshots. In addition to the DOS, the diagonalization of the electronic Hamiltonian for different MD snapshots provides a direct estimate of the localization length and the analysis of the states in the band gap provides a chemical description of the states occupied by the carrier.…”

Section: Density Of Statesmentioning

confidence: 99%

Organic Semiconductors: Impact of Disorder at Different Timescales

McMahon

Troisi

2010

ChemPhysChem

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The charge transport in organic materials, from molecular crystals to polymers, is determined by their degree of disorder. The dynamic disorder in ideal molecular crystals at room temperature and the static disorder in disordered polymers are just two limiting cases of the timescale of the fluctuations in the electronic Hamiltonian caused by nuclear motions. In fact, a very large number of important materials (e.g. liquid crystalline semiconductors) are actually in an intermediate regime where the disorder is neither purely static nor purely dynamic. This Minireview discusses the recent contribution of computational chemistry (molecular dynamics and quantum chemistry) to the characterization of these transport regimes and outlines the theoretical methods that can be used to relate the system characteristics to the measurable mobility.

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Dependence of the mobility on charge carrier density and electric field in poly(3-hexylthiophene) based thin film transistors: Effect of the molecular weight

Cited by 43 publications

References 28 publications

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Molds and Resists Studies for Nanoimprint Lithography of Electrodes in Low-Voltage Polymer Thin-Film Transistors

Charge Transport in Disordered Organic Materials and Its Relevance to Thin‐Film Devices: A Tutorial Review

Organic Semiconductors: Impact of Disorder at Different Timescales

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