Integrated blocking layers for hybrid organic solar cells

In hybrid organic solar cells a blocking layer between transparent electrode and nanocrystalline titania particles is essential to prevent short-circuiting and current loss through recombination at the electrode interface. Here we report the preparation of a thin, uniform and crack free hybrid blocking layer composed of conducting titania nanoparticles embedded in an insulating polymer derived ceramic. To do so we combine sol-gel chemistry with novel poly(dimethylsiloxane) containing amphiphilic block copolymer, poly(ethyleneglycol) methyl ether methacrylate-block-poly(dimethylsiloxane)- block-poly(ethyleneglycol) methyl ether methacrylate as the templating agent. Conductive probe scanning force microscopy proved that the existing percolating titania networks are separated by an insulating ceramic matrix. The structural uniformity of the percolating structures was investigated by microbeam grazing incidence small angle X-ray scattering making the integrated blocking layer suitable for hybrid organic solar device applications. Preliminary tests with the integrated blocking layer showed reasonable comparison to conventional TiO₂ blocking layer containing devices mentioned in the literature.