Pentacene structure

Fig. 3.1. Pentacene structure, crystalline order, and thin-film orientation.

Figure 1.13. Crystal structure of solution-grown pentacene along (a) the c-axis and (b) the fe-axis. Pl,a = 0.790 nm, b = 0.606 nm, c = 1.601 nm, a = 101.9°, P = 112.6°, y = 85.8°. Crystallographic data from Campbell et al, 1961. See Table 1.10 for comments on the values of the lattice parameters. Crystal structure of p-6P (c) c-planes along their long molecular axis and (d) along the fe-axis. P2i /c, a = 2.624 nm, b = 0.557 nm, c = 0.809 nm, p = 98.17°. Crystallographic data from Baker et al, 1993. Crystal stmcture of o -6T (e) fee-plane and (f) projection along the c-axis. P2ifn,a = 4.471 nm,fe = 0.785 nm,c = 0.603 nm,jS = 90.76°. Crystallographic data from Horowitz et al, 1995.

In an attempt to combine band-Uke charge carrier motion realized in an -inevitably fragile - crystalline FET structure with structural robustness and flexibility, Sakanoue and Sirringhaus [167] prepared FETs using spin coated films of 6,13-bis(triisopropylsilylethynyl)(TIPS)-pentacene films in contact with a perfluorinated, low dielectric-constant polymer gate electrode. The (linear) hole mobility at room temperature is 0.8 cm /V s with tendency of an apparent band-like negative temperature coefficient of the mobility (d/i/dT < 0). 

The several methods of energy dissipation, including fluorescence, are strongly dependent on the structure of the excited molecule. The existence of rigid planar aromatic structures is usually favourable to fluorescence. The size of the aromatic system also directly affects the fluorescence intensity and the excitation and emission wavelengths. For the series benzene, naphthalene, anthracene, tetracene and pentacene the emission and excitation wavelengths increase from SOS to S80 nm and from 278 to 640 nm, respectively [28]. 

T-type chromophores 37 (j-tum structure 418 twisting power 55 two-level system (TLS) pentacene 3 perylene 3 terrylene 3... 

An overcrowded PAH, 9,10,ll,20,21,22-hexaphenyltetrabenzo[a,c,I,n]pentacene (55), showed an interesting screw-type helicity (Fig. 15.21) [97]. An end-to-end twist of 144° was estimated from the X-ray structure of 55. Pentacene 55 was prepared by the reaction of l,3-diphenylphenanthro[9,10-c]furan 54 with the bisaryne equivalent generated from l,2,4,5-tetrabromo-3,6-diphenylbenzene in the presence of n-butyllithium, followed by deoxygenation of the double adduct with low-valent titanium. Pentacene 55 could be resolved by chromatography on a chiral support, but it racemized slowly at room temperature (t1/2 9 h at 25 °C). 

Fig. 1.4. Output (a) and transfer (b) characteristics of a typical OTFT. The inset shows the molecular structure of pentacene, which serves as semiconductor in the device.

Fig. 2.4. The often dramatic effects bottom contacts can have on molecular ordering in organic semiconductors like pentacene. A. Schematic diagram of the type of disorder introduced in pentacene s lamellar structure as thin-film growth encounters a step, for example...

Fig. 2.8. Normal (left) and side views (center, right) of the ab planes of bulk pentacene and the proposed monolayer structures. The monolayer views were constructed from a model based on grazing-incidence X-ray diffraction data [24].

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