Synthesis and characterization of novel poly(aryleneethynylene)s derived from squaraines for photovoltaic applications

Two novel π-conjugated polymers composed of alkyl carbazole/dialkoxyphenylene and squaraine units were synthesized by Sonogashira cross-coupling reactions. The structures and properties of these copolymers were characterized using FT-IR, NMR, UV–Vis, gel permeation chromatography and cyclic voltammetry (CV). Both polymers possess adequate thermal stability and exhibit good solubility in common organic solvents such as chloroform, THF, and toluene. The polymer films show intense and broad visible and near IR absorption with the long wavelength absorption maximum peaks of 796 and 851 nm for P₁ and P₂, respectively, which are apparently red-shifted compared with poly(phenyleneethynylene). CV studies reveal that the band gaps of these copolymers are about 1.45 eV, implying that the resulted polymers may be promising candidates for solar cells.