Growth mode transition of atomic layer deposited Al 2O 3 on porous TiO 2 electrodes of dye-sensitized solar cells

Abstract

This study investigates the growth behavior of atomic-layer-deposited (ALD) Al 2O 3 overlayers on porous TiO 2 electrodes, which comprise an anatase nanoparticle layer and a rutile particle layer, for optimizing dye-sensitized solar cells. The growth mode of the ALD Al 2O 3 overlayers changes from island growth to layer-by-layer growth during the first few ALD reaction cycles, and the growth mode transition is much more pronounced for the anatase electrode layer. The transition is likely a result of the reduction in the contractive lattice strain of the TiO 2 nanoparticles. The lattice strain in the hydroxylated TiO 2 nanoparticles is progressively reduced during the ALD Al 2O 3 deposition, resulting in the growth mode transition.