Self-Assembled Structures of Semiconductor Nanocrystals and Polymers for Photovoltaics. 2. Multilayers of CdSe Nanocrystals and Oligo(poly)thiophene-Based Molecules. Optical, Electrochemical, Photoelectrochemical and Photoconductive Properties.

A series of terthiophene and sexithiophene alpha,omega-dicarboxylic and -diphosphonic acids and some poly(thiophene-carboxylate)s and -sulfonate)s were reacted with hexadecylamine-capped CdSe nanoparticles (6 or 7.5 nm diameter) in CHCl3 to form regular polymeric structures on ITO-glass surfaces via layer-by-layer (LBL) alternation. The new materials were investigated by cyclic voltammetry, UV-vis, FTIR and PL spectroscopy, photoelectrochemistry, and photoconductivity. The LBL structures, constituted by quantum dots linked by hole-transporting conjugated chains, display optical and electronic properties useful in photovoltaic devices. The conjugated linker chains ease in fact charge transport between dots but transport of photogenerated carriers is dominated by interdot distance.