Synthesis and characterization of ZnO nano-plant-like electrodes.

Abstract

Dye-sensitized solar cells (DSSCs) have received considerable attention as a cost-effective alternative to conventional inorganic solar cells. These cells operate on a process similar to photosynthesis, the process by which green plants generate chemical energy from sunlight. A thick semiconductor nanoparticle film provides a large surface area for the adsorption of energy by light harvesting organic dye molecules which then "inject" electrons into the nanostructured semiconductor electrode. This process is accompanied by a charge transfer to the dye from an electron donor mediator supplied by an electrolyte, resetting the cycle. A significant increase in the long-term stability and the efficiency of DSSCs has been realized during the last few years. However, still the current nanoparticle-based DSSCs suffer from the trap-limited diffusion transport mechanism of electrons, a slow mechanism that limits the device efficiency, especially at longer wavelengths. Recently we have developed a new version of the dye-sensitized cells in which the traditional electrode (sintered nanoparticle film) is replaced by a specially designed ZnO electrode possessing an exotic 'nanoplant-like' morphology. This advance fixes a major efficiency limiting factor in current nanoparticle-based DSSCs. The direct electrical pathway, provided by the interconnected nanoplants, provides rapid collection of carriers generated throughout the device, and significantly enhances the conversion efficiency of the system over that of sintered nanoparticle based solar cells.