Control of Recombination Pathways in TiO2 Nanowire Hybrid Solar Cells Using Sn4+ Dopants

Hybrid nanostructures have shown increasing potential as a replacement for Si solar cells due to the availability of low-cost material combinations. However, up to now, hybrid solar cells, where photon absorption occurs in a semiconducting polymer and charge separation occurs at a metal oxide-polymer interface, show limited efficiencies. One limitation is caused by a relative low charge carrier mobility in the metal oxide. Here we addressed this issue and describe the use of a Sn:TiO2|TiO2 core–shell nanowire array to increase the charge-carrier mobility in the core of the nanowires while decreasing the charge-carrier recombination at the metal oxide–polymer interface due to fast electron extraction from this interface, driven by a cascaded conduction band energy from shell to core of the nanowires. These doped cores with an undoped shell structure resulted in impressive efficiency improvement in hybrid solar cells of 33% over the reference TiO2-based device. Additionally, this device structure resulted i...