Interface Engineering through Atomic Layer Deposition towards Highly Improved Performance of Dye-Sensitized Solar Cells

A composite photoanode comprising ultralong ZnO nanobelts and TiO(2) nanoparticles was prepared and its performance in dye-sensitized solar cells (DSSCs) was optimized and compared to the photoanode consisting of conventional TiO(2) nanoparticles. The ultralong ZnO nanobelts were synthesized in high yield by a facile solution approach at 90 (o)C followed by annealing at 500 (o)C. The effect of the ratio of ZnO nanobelts to TiO(2) nanoparticles on the light scattering, specific surface area, and interface recombination were investigated. An optimum amount of ZnO nanobelts enhanced the photon-conversion efficiency by 61.4% compared to that of the conventional TiO(2) nanoparticles. To further reduce the recombination rate and increase the carrier lifetime, Atomic Layer Deposition (ALD) technique was utilized to coat a continuous TiO(2) film surrounding the ZnO nanobelts and TiO(2) nanoparticles, functioning as a barrier-free access of all electrons to conductive electrodes. This ALD treatment improved the interface contact within the whole photoanode system, finally leading to significant enhancement (137%) in the conversion efficiency of DSSCs.