Interface engineering through atomic layer deposition towards highly improved performance of dye-sensitized solar cells

Abstract

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°C followed by annealing at 500°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.