Low-band gap polymeric cyanine dyes absorbing in the NIR region

Two new, fully conjugated polymeric cyanine dyes based on trimethine and heptamethine moieties have been synthesized. Both polymers were characterized by gel permeation chromatography, UV-vis and IR spectroscopy, elementary analysis and cyclic voltammetry. The structure of one material could be confirmed with NMR spectroscopy. Upon head-to-tail coupling of the dye moieties distinct bathochromic shifts up to 159 nm were observed for the polymers which absorb solely in the near infrared (NIR) region with maxima up to 1002 nm and very high molar absorption coefficients. This highly efficient absorption in the NIR spectral domain combined with the strong electron accepting properties makes these dyes interesting candidates for many optical applications; investigations on photovoltaic devices based on polymeric cyanine dye/C(60) heterojunctions identify one of these possibilities.