Well-defined all-conducting block copolymer bilayer hybrid nanostructure: selective positioning of lithium ions and efficient charge collection.

A block copolymerization of nonfunctionalized conducting monomers was developed to enable the successful synthesis of a highly insoluble 3,4-(ethylenedioxy)thienyl-based all-conducting block copolymer (PEDOT-b-PEDOT-TB) that could encapsulate nanocrystalline dyed TiO2 particles, resulting in the formation of an all-conducting block copolymer bilayer hybrid nanostructure (TiO2/Dye/PEDOT-b-PEDOT-TB). Lithium ions were selectively positioned on the outer PEDOT-TB surface. The distances through which the positively charged dye and PEDOT-TB(Li(+)) interacted physically or through which the TiO2 electrode and the Li(+) centers on PEDOT-TB(Li(+)) interacted ionically were precisely tuned and optimized within ca. 1 nm by controlling the thickness of the PEDOT blocking layer (the block length). The optimized structure provided efficient charge collection in an iodine-free dye-sensitized solar cell (DSC) due to negligible recombination of photoinduced electrons with cationic species and rapid charge transport, which improved the photovoltaic performance (η = 2.1 → 6.5%).