Topic
Pentacene
About: Pentacene is a research topic. Over the lifetime, 5051 publications have been published within this topic receiving 161481 citations. The topic is also known as: 2,3:6,7-dibenzanthracene & benzo[b]naphthacene.
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TL;DR: In this article, the average electron-hole distance and the degree of charge-transfer character within low-energy optical excitations in solid-state pentacene have been quantified using first-principles calculations based on density functional theory and manybody perturbation theory.
Abstract: The nature of low energy optical excitations, or excitons, in organic solids is of central relevance to many optoelectronic applications, including solar energy conversion. Excitons in solid pentacene, a prototypical organic semiconductor, have been the subject of many experimental and theoretical studies, with differing conclusions as to the degree of their charge-transfer character. Using first-principles calculations based on density functional theory and many-body perturbation theory, we compute the average electron–hole distance and quantify the degree of charge-transfer character within optical excitations in solid-state pentacene. We show that several low-energy singlet excitations are characterized by a weak overlap between electron and hole and an average electron–hole distance greater than 6 A. Additionally, we show that the character of the lowest-lying singlet and triplet excitons is well-described with a simple analytic envelope function of the electron–hole distance.
177 citations
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TL;DR: Finite regions of high conductivity were observed in both n- and p-channel organic thin film transistors based on polycrystalline organic semiconductor films and a solution-processed, solid polymer electrolyte gate dielectric.
Abstract: Finite regions of high conductivity were observed in both n- and p-channel organic thin film transistors based on polycrystalline organic semiconductor films and a solution-processed, solid polymer electrolyte gate dielectric The transition from a highly conductive state to a more insulating state with increasing gate bias may be attributed to the realization of carrier densities greater than 1014 charges/cm2 in the semiconductor film
177 citations
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TL;DR: In this paper, several methods are used in order to extract the mobility and threshold voltage from the transfer characteristic of organic field-effect transistors, which are found to depend on the gate voltage.
Abstract: Organic field-effect transistors were fabricated with vapor-deposited pentacene on aluminum oxide insulating layers. Several methods are used in order to extract the mobility and threshold voltage from the transfer characteristic of the devices. In all cases, the mobility is found to depend on the gate voltage. The first method consists of deriving the drain current as a function of gate voltage (transconductance), leading to the so-called field-effect mobility. In the second method, we assume a power-law dependence of the mobility with gate voltage together with a constant contact resistance. The third method is the so-called transfer line method, in which several devices with various channel length are used. It is shown that the mobility is significantly enhanced by modifying the aluminum oxide layer with carboxylic acid self-assembled monolayers prior to pentacene deposition. The methods used to extract parameters yield threshold voltages with an absolute value of less than 2 V. It is also shown that there is a shift of the threshold voltage after modification of the aluminum oxide layer. These features seem to confirm the validity of the parameter-extraction methods.
175 citations
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TL;DR: In this article, the authors used density functional theory and many-body perturbation theory to calculate the spectroscopic properties of two prototypical organic semiconductors, pentacene, and 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA), quantitatively comparing with measured PES, IPES, and optical absorption spectra.
Abstract: The broad use of organic semiconductors for optoelectronic applications relies on quantitative understanding and control of their spectroscopic properties. Of paramount importance are the transport gap---the difference between ionization potential and electron affinity---and the exciton binding energy---inferred from the difference between the transport and optical absorption gaps. Transport gaps are commonly established via photoemission and inverse photoemission spectroscopy (PES/IPES). However, PES and IPES are surface-sensitive, average over a dynamic lattice, and are subject to extrinsic effects, leading to significant uncertainty in gaps. Here, we use density functional theory and many-body perturbation theory to calculate the spectroscopic properties of two prototypical organic semiconductors, pentacene, and 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA), quantitatively comparing with measured PES, IPES, and optical absorption spectra. For bulk pentacene and PTCDA, the computed transport gaps are 2.4 and 3.0 eV, and optical gaps are 1.7 and 2.1 eV, respectively. Computed bulk quasiparticle spectra are in excellent agreement with surface-sensitive photoemission measurements over several eV only if the measured gap is reduced by 0.6 eV for pentacene and 0.6--0.9 eV for PTCDA. We attribute this redshift to several physical effects, including incomplete charge screening at the surface, static and dynamical disorder, and experimental resolution. Optical gaps are in excellent agreement with experiment with solid-state exciton binding energies of \ensuremath{\sim}0.5 eV for both systems; for pentacene the exciton is delocalized over several molecules and exhibits significant charge transfer character. Our parameter-free calculations provide new interpretation of spectroscopic properties of organic semiconductors critical to optoelectronics.
175 citations
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TL;DR: In this paper, the authors used polyimide gate dielectric layers to fabricate high-quality pentacene field effect transistors on polyethylenenaphthalate-based films.
Abstract: Polyimide gate dielectric layers cured at 180 °C have been employed to fabricate high-quality pentacene field-effect transistors on polyethylenenaphthalate-based films. The surface roughness (root-mean square) of gate dielectric layers characterized by atomic force microscopy is only 0.2 nm, while that of the base film is 1 nm. The transistors with pentacene channel layers deposited on 990 nm polyimide gate dielectric layers attain the on/off ratio of 106 and mobility of 0.3 cm2/V s. Furthermore, by decreasing the thickness of polyimide gate dielectric layers down to 540 nm, the mobility is enhanced up to 1 cm2/V s.
175 citations