Conjugated photophysics

The chapter is organized as follows the second section will discuss the photophysics of conjugated polymer/fullerene composites as a standard model for a charge-generating layer in plastic solar cells. Pristine polymer devices will be discussed in the third section while bilayer and interpenetrating network devices are presented in Sections 4 and 5. Section 6 contains some remarks on large area plastic solar cells and Section 7 conclusions. 

The role of disorder in the photophysics of conjugated polymers has been extensively described by the work carried out in Marburg by H. Bassler and coworkers. Based on ultrafast photoluminescence (PL) (15], field-induced luminescence quenching [16J and site-selective PL excitation [17], a model for excited state thermalizalion was proposed, which considers interchain exciton migration within the inhomogenously broadened density of states. We will base part of the interpretation of our results in m-LPPP on this model, which will be discussed in some detail in Sections 8.4 and 8.6. 

Gygax R, Wirz J, Sprague JT, Allinger NL. Electronic structure and photophysical properties of planar conjugated hydrocarbons with a 4n-membered ring. Part III. Conjugative stabilization in an antiaromatic system The conformational mobility of l,5-bisdehydro[12]annulene. Helv Chim Acta 1977 60 2522-9. 

When the reaction of [AujCgFsjjtht)] is carried out with C6F4NCSPPh2 the complex [56] shovm in Figure 3.5 was obtained and its structure was determined by X-ray diffraction. The benzothiazole ligands are known to display photophysical properties vdth an improvement of the photostability and emission intensity in conjugated systems as well as in the complexes that contain them, and the presence of... 

Zigmantas, D., R. G. Hiller, F. P. Sharpies, H. A. Frank, V. Sundstrom, andT. Poltvka. 2004. Effect of conjugated carbonyl group on photophysical properties of carotenoids. Phys. Chem. Chem. Phys. 6 3009-3016. 

On the other hand, the introduction of halide substituents at the C-2 and C-6 position decreases fluorescence quantum yields and gives a bathochromic shift of emission maxima. For example, bromine at the C-2 and C-6 position in compound 14b deteriorates fluorescence quantum yields from 0.95 (14a) to 0.45 and the emission maximum is red-shifted by 42 nm. Moreover, iodine at the C-2,6 position in compound 14d gives the similar bathochromic shift to bromine (14b, 44 nm) and more dramatic reduction in quantum yields (almost nonfluorescent, photophysical properties were interpreted as the heavy atom effect of halides on a BODIPY core skeleton. The bathochromic shift of BODIPY dyes without dramatic decrease in quantum yield was observed by the introduction of vinyl substituents at the C-2 and C-6 position. The extension of conjugation... 

Smith, S. N. and Steer, R. P. (2001). The photophysics of Lissamine rhodamine-B sulphonyl chloride in aqueous solution implications for fluorescent protein-dye conjugates. J. Photochem. Photobiol. A Chem. 139, 151-156. 

Even larger, conjugated systems were synthesized by employing both difunctional isocyanides and difunctional alkynes. In all the cases, the components have structural rigidity, which lends rigid-rod character to the complexes prepared from them. Many of the complexes are associated via intermolecular aurophilic contacts, which appear to have a distinct influence on the photophysical behavior, but are as yet not a necessary condition for luminescence (Scheme 51).196... 

Because of the great importance of PF as a class of conjugated polymers with excellent optical and electronic properties, several theoretical studies were performed to better understand the electronic structure and the photophysical processes, which occur in these materials [260-265],... 

---