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.

Potential mapping of pentacene thin-film transistors using purely electric atomic-force-microscope potentiometry

Abstract: Potential mapping of organic thin-film transistors (TFTs) has been carried out using originally developed atomic-force-microscope potentiometry (AFMP). The technique is suitable for the accurate measurement at metal–semiconductor boundaries of working TFTs. Potential drops near metal–organic boundaries are observed for both source and drain Au top contacts of a pentacene TFT. The approximate width of the steeper potential slope is 400 nm, which is larger than the spatial resolution of AFMP. The potential drop is considered to be due to a damaged area with low carrier mobility caused by the Au evaporation, which is also reproduced by device simulation.

Absorption spectra of disordered solid tetracene and pentacene

Abstract: Absorption spectra of tetracene and pentacene layers prepared by vapor deposition onto cooled substrates were measured as a function of sample formation temperature Tf, evaporation rate and recording temperature. Profile-analysis indicates that the main absorption peak is of gaussian shape. The width varies between 300 cm−1 and 650 cm−1, higher values referring to lower formation temperatures and/or higher evaporation rates and reflecting larger fluctuation of the site-energies. Appearance of a second electronic band equivalent to the upper Davydov component in the crystal spectrum indicates presence of short-range order. The low-energy behavior is dominated by a structural defect. No Urbacht-tail is observed. It is concluded that tetracene and pentacene layers represent examples for intermediate structural disorder.

A modular synthetic approach to conjugated pentacene di-, tri-, and tetramers.

Abstract: Pentacene and functionalized pentacenes are leading candidates for small-molecule semiconductor applications and have been widely explored over the past decade. On the other hand, examples of pentacene polymers 3a–c] and oligomers remain scarce, even though they present obvious opportunities for discovery. In comparison to polymers, monodisperse oligomers provide the added benefit of structural homogeneity. Furthermore, oligomers allow for the systematic study of structure–property relationships, in which a property of interest (e.g., HOMO–LUMO gap (HOMO = highest occupied molecular orbital, LUMO = lowest unoccupied molecular orbital)) is examined as a function of oligomer length. If oligomers of sufficient length are accessible, the effective conjugation length can be determined by observing saturation of a property; that is, when the oligomer starts to behave like the polymer. To date, the synthesis of functionalized pentacenes has relied, to a large extent, on the addition of nucleophiles to acenequinones such as 6,13-pentacenequinone, followed by reduction to form the aromatic pentacene framework. This methodology cannot, however, easily be adapted to the synthesis of conjugated oligomers. Such synthetic limitations are due, in part, to the reactive nature of the pentacene core and to the limits of current methodology for desymmetrizing the pentacene chromophore. It is unlikely that this issue can be effectively addressed by condensation and cycloaddition reactions to form acenes, since such methods often produce isomeric mixtures. Oxidative acetylenic homoand cross-coupling reactions of terminal and/or haloacetylenes (e.g., Hay and Cadiot–Chodkiewicz reactions) are a well-established means of assembling carbon-rich materials. These reactions, when paired with recently developed methods to form unsymmetrical pentacenes, would serve as the foundation for the synthesis of a homologous series of pentacene oligomers. Pentacenes that bear a terminal acetylene functionality, such as 1 or 2 (Scheme 1), are quite reactive, and have been ineffective to date when isolated and used as precursors for

Crystal Engineering for π−π Stacking via Interaction between Electron-Rich and Electron-Deficient Heteroaromatics

Abstract: New dipolar compounds containing alternating electron-rich thieno[3,2-b]thiophene units and electron deficient units have been synthesized. Compounds with 5-pyrimidinyl (compound 2) or benzothiazole (compound 5) as the electron-deficient unit were structurally characterized by the single-crystal X-ray diffraction method. The arrangement of the molecules is found to be one-dimensional slipped-π-stack for 2. That of 5 is of slipped-π-stack, albeit with a tilt angle between neighboring π-stacks. The π−π interfacial distances of the molecules in the crystal lattice are 3.47 and 3.59 A for 2 and 5, respectively. On the basis of the crystal structure, compound 2, with negligible π−π slip along the short axis of the molecules, has a calculated electronic coupling value (0.153 eV) twice as large as that of the largest coupling of pentacene. Accordingly, the theoretically estimated hole mobility (μ+) for 2 (2.32 cm2 s−1 V−1) compares favorably with that of pentacene (1.93−5.43 cm2 s−1 V−1), despite of the larger r...