PTCDA

TCNQ icliucyanorjuinodimcihuiic TDAE iclrukis dimclhylaminoclhanc NTCDA naphlhalenc letracarboxylic dianhydridc PTCDA pciylenc lelracarbuxylic dianhydridc... 

Figure 14-20. Molecular structure of naphthalene tctracarboxylic dianliydridc (NTCDA) and perylene letracarboxylic dianhydridc (PTCDA).

Fluorescent nanotubes of polyethyleneimine (PEI) and 3,4,9,10-perylenetetra-carboxylicdianhydride (PTCDA) have been prepared through the alternating deposition of polymers and small functional molecules that form covalent bonds (Figure 7.10) [ 120]. The nanotube synthesis starts with the deposition of P EI in the pores of an AAO membrane as the first layer. The PTCDA solutionis then used to bind to the PEI via covalent bonding (Figure 7.10). The electro-optical properties of the small molecule (PTCDA) are retained in the multilayer films of PEI/PTCDA. The prepared nanotubes retain their fluorescent properties for up to 10 months without... 

Fig. 7.10 Schematic representation of fluorescent nanotubes prepared through the alternate deposition of PEI and PTCDA in AAO membrane templates. (Reproduced from [119] with permission of the American Chemical Society, Copyright 2006 American Chemical Society).

Tsiper EV, Soos Z, Gao W, Kahn A (2002) Electronic polarization at surfaces and thin films of organic molecular crystals PTCDA. Chem Phys Lett 360 47-52... 

Fig. 13.11 (a) The molecular absorbance MNF sensor (inset PTCDA molecule) (b) Evolution of spectrum of submonolayer deposition at 1,2, 4, and 8 s after beginning of molecule exposure (c) Subsequent evolution of the spectral absorption at constant molecule number at 13, 53, 413, and 2,393 s after beginning of molecule exposure. Reprinted from Ref. 19 with permis sion. 2008 Optical Society of America... 

PTCDA represents a further example of non-planarity. When chemisorbed on an Ag(l 11) surface the carboxylic oxygen atoms become 0.018 nm closer to the... 

Dlh TTF, TCNQ, TMTTF, TMTSF, BEDT-TTF, PTCDA, Ni(dmit)2, BEDT-TSF, BDA-TTP, pentacene... 

Two modifications, a and are known for PTCDA. Eigure 1.25 shows a projection onto the (102) plane of a-PTCDA. The major difference between both crystallographic phases is the angle between the fc-axis and the longer axis of the... 

Figure 1.25. Projection onto the (102) plane of a-PTCDA. C and O atoms are represented by black and medium grey balls, respectively. H atoms are omitted for clarity. Crystallographic data from Ogawa et al, 1999.

The study of vapour-deposited organic films has been applied to a large number of molecular systems. However, most of the work has concentrated on the study of the growth and optoelectronic characteristics of planar stacking molecules such as the Pc and polycyclic aromatic compounds based on naphthalene, and perylene. In particular, PTCDA has become extensively studied. 

A ML can be simply defined as a one-molecule thick 2D film, but the molecular surface density has to be defined for each molecule-substrate system because it depends on the shape, size and relative orientation of the molecules. To clarify this point let us consider the examples of PTCDA and Ceo on the Ag(l 11) surface. The surface density of the substrate is 1.4 x 10 atoms cm , which is usually defined as 1 ML as a reference limit. The surface density of the (102) plane of PTCDA, the cleavage plane, is 8.4 x 10 and 8.3 x 10 cm (molecules cm ) for the monocliiuc a and polymorphs, respectively. Therefore, full coverage corresponds to 0.02 ML according to this definition. On the other hand, the surface density of a full hexagonal layer of closed-packed Ceo molecules corresponding to the (111) plane in the fcc-Ceo crystal is 1.2 x 10 " cm . Thus, Ceo would fully cover the Ag(l 11) surface at a coverage of 0.09 ML. However, other authors define 1 ML as... 

The comparison of PTCDA with its parent perylene molecule is extremely interesting. For perylene MLs on Ag(l 11), electron diffraction suggests an orientational liquid, in which the molecules are positionally ordered in an incommensurate close-packed superlattice but orientationally disordered and mobile. The same activated Raman peaks as for PTCDA are observed but they are, however, orders of magnitude weaker, indicating that, while a molecular reaction centre may still exist in the perylene backbone, its residual activity would be too small for the molecule to recognize a preferred site. 

Figure 4.32. Band diagrams of PTCDA/a-NPD, a-NPD/Alqs and Alqs/PTCDA. The experimental error, 0.2 eV, is indicated. Adapted from Rajagopal et al, 1998.

The luminance (cd m ) depends on the applied bias voltage and can achieve values of 10 with external quantum efficiencies (percentage of photons per electron) of 2-3%. The PTCDA/Alqs discussed above (Pig. 4.32) exhibits a low luminescence efficiency because the relative position of the LUMOs is inadequate to confine electrons in the emissive Alqs layer. 

PTCDA films OMBD-grown on Ag(lll) single crystals show a transition from layer-by-layer growth with smooth and small-grained morphology towards the... 

Hirose Y, Kahn A, Aristov V, Soukiassian P, Bulovic V, Forrest SR (1996) Chemistry and electronic properties of metal-organic semiconductor interfaces Al, Ti, In, Sn, Ag, and Au on PTCDA. Phys Rev B 54 13748... 

---