It is rather hard for the existing solar battery to achieve a conversion efficiency of 40%. A research team led by Akira Ishibashi of Hokkaido University developed a technology to increase the conversion efficiency, theoretically to 85%, by converting most of sunlight to electricity using many kinds of semiconductors made of different materials. By lining up plural semiconductor thin films to the direction of travel of light, the technology absorbs ultraviolet, optical wavelength, infrared in this order. The research team has only confirmed the principle at present, and it plans to commercialize the technology at an early date.
In this principle, light thrusts into not from the surface of the thin film but from the cross section. To increase the area on which light shines, the research team built a structure that folds the thin film as a roll and allows light to irradiate the cross section of the roll to let light get inside the film. Existing studies focus on increasing the conversion efficiency by stacking particles of different sizes in quantum dot. The new technology is hard to materialize because of the difficulty to get suitable semiconductor materials, but it is easier to handle than the quantum dot, the research team said.
Trend of the conversion efficiency of a solar battery