Semiconductor amphiphilic block copolymers for hybrid donor-acceptor nanocomposites

Block copolymers feature unique properties for organizing in a well-defined pattern on length scales of several tenths of nanometers. This special attribute enables the formation of ideal donor and acceptor domains for photovoltaic devices in the size of the exciton diffusion length. Thus we designed an amphiphilic block copolymer, able to act as a hole conductor and to coordinate inorganic semiconductor nanoparticles as electron acceptors. Utilizing controlled radical polymerization techniques, defined polymers were synthesized consisting of triphenylamine pendant groups in the hole conductor block and a hydrophilic polystyrene sulfonate block. This particular combination creates narrowly distributed micelles in aqueous solution exhibiting domain sizes suitable for photovoltaic applications. The strong anionic sulfonate groups offer high loading capacities for modified cationic nanoparticles. To guarantee a broad absorption and good conductivity, we synthesized cationic CdSe nanorods and combined them with our hole conductor micelles. The advantage of high loading combined with the processability from aqueous dispersions promises a novel "green" alternative for preparation of hybrid solar cells with controlled domain sizes in the desired length scale.