Polyacetylenes photosensitivity

Photoelectrochemical cells with polythiophene film as an active electrode and a lead plate as a counter electrode in Pb (C104) acetonitrile electrolyte has an open circuit voltage of 0.8 V, short circuit current of 2 x 10 4 A cm-2, efficiency coefficient of 0.03%, fill factor of 15% [194]. The absorption and photosensitivity spectra of such a cell are shown in Fig. 24. The small bathochromic shift in the longwave region for photosensitivity may be related to the photogeneration of the charge carriers via surface states. The photosensitivity maximum is close to the maximum solar intensity. The parameters exceed the ones obtained with polyacetylene. 

As explained in the introduction, the polysilanes (and related polygermanes and poly-stannanes) are different from all other high polymers, in that they exhibit sigma-electron delocalization. This phenomenon leads to special physical properties strong electronic absorption, conductivity, photoconductivity, photosensitivity, and so on, which are crucial for many of the technological applications of polysilanes. Other polymers, such as polyacetylene and polythiophene, display electron delocalization, but in these materials the delocalization involves pi-electrons. 

Charge-transfer initiator systems are attracting increased interest, as is cationic photopolymerization. Photopolymers of acetylenes and polyacetylenes are of potential importance as conductors and semiconductors, for example in solar cell applications (Fouassier et al., Yee, Day, et al., inter alia). Fouassier et al. report that vinyl polymerization photosensitized by aromatic ketones can proceed faster in a micellar system through enhanced initiation rather than propagation. 

McLachlan, D., T. Arnason, and J. Lam The Role of Oxygen in Photosensitizations with Polyacetylenes and Thiophene Derivatives. Photochem. Photobiol. 39, 177 (1984). 

McRae, D.G., E. Yamamoto, and G.H.N. Towers The Mode of Action of Polyacetylene and Thiophene Photosensitizers on Liposome Permeability to Glucose. Biochim. Biophys. Acta 821, 488 (1985). 

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