Molecular dyes

The aim of this chapter is to give a state-of-the-art report on the plastic solar cells based on conjugated polymers. Results from other organic solar cells like pristine fullerene cells [7, 8], dye-sensitized liquid electrolyte [9], or solid state polymer electrolyte cells [10], pure dye cells [11, 12], or small molecule cells [13], mostly based on heterojunctions between phthaocyanines and perylenes [14], will not be discussed. Extensive literature exists on the fabrication of solar cells based on small molecular dyes with donor-acceptor systems (see for example [2, 3] and references therein). 

Stokes shift decreases with larger chain length (from 0.29 to 0.16 eV) [134], For one of the oligophenylenevinylenes, it was demonstrated that the presence of metal electrodes, even if evaporated in submonolayers, strongly quenches the photoluminescence of molecular dye layers [135]. 

Some low-molecular dyes also have been investigated in inactive polymer matrices. For stilbene compounds in polystyrene, peak wavelengths in the green spectral region are obtained, with net optical gain coefficients of g = 15-20 cm-1 [187],... 

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