Five-ring OPVs

Shifts between the film photoluminescence spectra of the various oligomers follow the same trend as found for the solution spectra, but the film spectrum is strongly red-shifted relative to the solution spectrum in each case (Tables 16-2 and 16-5). The photoluminescence spectra are strongly influenced by intermole- 

In the absorption spectra of the thin films, the low-energy shoulder is red-shifted and slightly more pronounced for the annealed film. The emission spectra 

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Crystal Structures of Five-Ring OPVs 16.3.1.2.1 Ooct-OPV5... 

Figure 16-36 shows the absorption spectra of thin films of four differently substituted five-ring OPVs. in contrast to the solution spectra, which show structureless low-energy absorption bands, the absorption bands of the films are structured. In the solid slate, the molecules are spatially constrained, whereas in solution different conformers exist, resulting in a distribution of accessible levels. As a consequence, some details appear in the absorption spectrum of the films which can be attributed to vibronic coupling, while, in dilute solution, the spectrum is a broad featureless band. For oct-OPV5 and Ooci-OPV5 films, the absorption maxima are red-shifted over approximately 0.1 eV relative to the solution (see Fig. 16-12). The low-energy absorption band of a thin film of Ooct-OPV5-CN" displays an appreciably larger...

The substituted five-ring OPVs have been processed into poly crystal line thin films by vacuum deposition onto a substrate from the vapor phase. Optical absorption and photolumincscence of the films are significantly different from dilute solution spectra, which indicates that intermolecular interactions play an important role in the solid-state spectra. The molecular orientation and crystal domain size can be increased by thermal annealing of the films. This control of the microstruc-ture is essential for the use of such films in photonic devices. 

A nice example of an orthogonal approach was published by Yu et al. [28]. A sequence of Heck and Horner reactions furnishes an OPV series with alternating substituted and unsubstituted benzene rings. A start segment 15 and two bifunctional extension reagents 16 and 17 were used as shown in Scheme 11.8. The yields of the five steps are good some disadvantages of the method are due to the... 

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