|Brendel, J.; Lu, Y.; Thelakkat, M.: Polymer templated nanocrystalline titania network for solid state dye sensitized solar cells, Journal of Materials Chemistry, 20, 7255-7265 (2010) -- DOI: 10.1039/C0JM00916D|
We report a novel preparation method for nanocrystalline TiO2 networks with controlled pore sizes using spherical polyelectrolyte brushes (SPB) as templates. The SPB consists of a solid polystyrene core from which anionic polyelectrolytes are densely grafted. The SPB templates are synthesized via conventional photoemulsion polymerization with efficient control of core size and brush length. Subsequently, the TiO2 precursor is hydrolyzed at room temperature within the anionic brush to obtain anatase nanocrystals of 1220 nm size. These stable and form-persistent composite particles of SPB decorated with anatase nanocrystals are then assembled on a conductive substrate. The subsequent calcination of this composite layer leads to a robust nanocrystalline TiO2 network, in which the pores and the wall thickness are directly correlated to the polystyrene core size and the amount of TiO2 hydrolyzed within the brush respectively. In this study, we optimized different thin-film preparation methods and characterized the resulting nanocrystalline TiO2 networks using SEM and XRD. Moreover, the applicability of these nanocrystalline networks as electron transport layers are tested in solid-state dye-sensitized solar cells (SDSCs). The first test devices exhibited efficiencies up to 0.8%. The precise and individual control of parameters such as porosity, thickness and crystallinity makes this concept highly attractive for the realization of efficient solid-state hybrid devices.