The May/June edition of Technology Review lists super efficient solar power as one of its ten breakthrough technologies. Solar panels on the market today consist of cells made from a single semiconducting material, usually silicon. Since the material absorbs only a narrow band of the solar spectrum, much of sunlight’s energy is lost as heat: these panels typically convert less than 20% of that energy into electricity.
In contrast, a technology being developed by Harry Atwater and his colleagues at CalTech would have an efficiency of at least 50%. It would use a design that efficiently splits sunlight, as a prism does, into six to eight component wavelengths—each one of which produces a different color of light. Each color would then be dispersed to a cell made of a semiconductor that can absorb it. Another design would employ nanoscale optical filters that could filter light coming from all angles. And a third would use a hologram instead of filters to split the spectrum. While the designs are different, the basic idea is the same: combine conventionally designed cells with optical techniques to efficiently harness sunlight’s broad spectrum and waste much less of its energy.
Atwater argues that achieving ultrahigh efficient designs should be a primary goal of the solar industry, as it is “the best lever we have” for reducing the cost of solar power.
