The newest solar energy discovery out of Switzerland, via Chinese researcher Peng Wang, reports on thin-film solar cells that have been dye-sensitized to trap more of the sun’s energy.Called Grätzel cells, these photovoltaic cells are composed of titanium dioxide tinted with light-harvesting dyes. Not only are they less expensive than silicon solar cells, but they can be made into flexible sheets or coatings which can be applied directly to a roof or other surface to harvest the sun’s energy.
Grätzel cells were first invented in 1991. The semiconductor portion of the solar unit is formed by a photo-sensitized anode and an electrolyte, and operates as a photo-electrochemical system. This new generation of dye-enhanced, thin film solar is predicted to be as cost-effective as fossil fuel energy because it uses low-cost materials, and is easier to manufacture and install than traditional, silicon-based photovoltaic systems. The drawback is a tendency for the dyes to degrade in the presence of ultraviolet (UV) light, but the addition of UV stabilizers and absorbent chromophores promises to remove that obstacle and make Grätzel cell solar technology commercially feasible in a decade.
Though still in the development phase, these dyed cells, treated with ruthenium (RU 44, a transition metal in the platinum group), have surpassed their predecessors in both efficiency (as high as 10 percent) and stability. The degradation factor has also been virtually eliminated, allowing the new cells to retain more than 90 percent of their original output even after 1,000 hours of exposure. The new formulation also increases stability at higher temperatures, another factor that caused first-generation Grätzel cells to fail so rapidly.
Currently available silicon-based solar energy systems boast a maximum efficiency of about 12 percent, and newer hybrids still in development suggest efficiencies may soon reach 18-19 percent. Grätzel cell advances may soon offer nearly the same efficiency at reduced cost. Either way, solar energy is making huge leaps forward, and promises homeowners a ‘green’ alternative to conventional, fossil-fueled electricity.