What is Dye Sensitized Solar Cell (DSSC)?
The electrochemical dye solar cell was invented in 1988 by Professor Graetzel of Lausanne Polytechnique, Switzerland. The ˇ°Graetzelˇ± dye cell is based on a layer of nano-sized titanium dioxide particles impregnated with dye. Dye cells have been a subject of intense academic interest as more than 50 university research teams around the world have worked to enhance their lifetime, size and efficiency.
Dye cells generate electricity from solar energy using nano-sized titanium dioxide particles impregnated with dye, rather than silicon or similar semiconductors. Using DSSCs will result in unprecedented low costs, both manufacturing line capital cost and module cost per peak watt (ppw). Other solar cell technologies (silicon, thin film) rely on complex vacuum deposition techniques for cell active layer preparation. Not only is the production line for these systems large, complex and very expensive, but the raw materials (such as silicon) are costly and undersupplied. By comparison, dye requires simple equipment (screen printing, air ovens) and benign materials like Titania powder available at low cost.
Competitive Market Advantages
The production of DSSCs incur relatively low cost: new patented technologies will result in less than $1.5 ppw for module manufacturing cost at initial production, dropping to about half this figure ($0.7 ppw) on the basis of economy of scale from multiple plants as opposed to more than $3 ppw today.
DSSCs have an additional advantage in that they are particularly suited to warmer climates. When hot, crystalline silicon modules lose efficiency far more than do dye cells.
DSSCs also work well in a wide range of lighting conditions and orientation, and they are less sensitive to partial shadowing and low-level illumination compared to silicon.
This is a schematic depiction of the components and operating mechanism of a typical PV dye cell.
The photoanode (facing the light source) is a glass plate whose inner surface has been coated with a thin layer (0.5 micron) of transparent conducting tin oxide (TCO). Onto this layer is coated (e.g. by sintering, other low temperature methods are available such as Electrophoresis) a several micron thick porous layer of nanocrystalline titanium dioxide (particle size about 20 nanometers) on which a monolayer of sensitizer dye is absorbed (ruthenium complex). The cell also comprises electrolyte containing a redox species based on iodide/tri-iodide, and a counter electrode (cathode) consisting of a glass plate also with a conducting tin oxide layer, coated with a few mono-layers of catalyst (platinum was originally used and can be replaced with carbon-based alternatives). In our approach the carbon layer can be applied directly on the Titania. This eliminates the need for a second sheet of FTO glass in the cell.
Courtesy of 3GSolar.
Manufacturing Line and Processes
Screen printing, which is a known thick-film processing tool and will be used to apply Titania and other layers to the FTO glass.
Wet processing such as glass cleaning and the dye staining process, which is done from solution.
Anode side application of proprietary current collectors. Automated current collector application to the titania coated FTO glass (anode) by a fully automated and efficient assembly machine set is one of the goals of the joint 3GSolar ¨C G Tech project.
Assembly, sealing and filling steps. This is where the FTO glass with the completed Titania layer is mated to the cathode current collector, protective glass plate, sealed, busbar attached to the cell and where the cell is filled with electrolyte.
Assembly of 32 cells into a module frame
Wiring the 32 cells in series including protective diodes
Apply encapsulation materials that protect the module wiring and provide a second level of sealing to the cells.