Solar cells seem to be everywhere these days, capturing photons from the sun's rays and converting them into electricity. Traditional designs use expensive silicon semiconductors while new technologies rely on less-efficient thin films that could eventually be fabricated at much lower costs. But they all work essentially the same way; they try to trap photons from sunlight and use these to raise the energy levels of the electrons in the solar cell. This energy is captured as electricity, and can be used as a power source. Unfortunately, these solar cells are only sensitive to a portion of the sunlight's spectrum, and much of the energy is lost.
Scientists at Tel Aviv University have taken a different approach to the problem. They have developed a technology that uses the fact that sunlight is a form of electromagnetic radiation. Depending on the wavelength, these emissions can appear as visible light or may be infrared or ultraviolet light, or even radio-frequency waves. An antenna tuned to the right wavelength can capture the energy from the waves and convert it into electricity (which is exactly what your television, radio, or cell phone antenna does).
There are two problems. First, sunlight contains a wide range of wavelengths, so one single antenna won't do the job. Also, the antenna has to be tuned to the size of the waves, and the wavelengths for visible light are incredibly short: on the order of 400 to 700 nm. The scientists have come up with a way to create a variety of microscopic antennas in simple plastic films using nano-imprinting lithography, then coating the material with a thin layer of aluminum or some other metal. According to Professor Koby Scheuer, "Our antenna ... has the potential to be more efficient and less expensive" than tradition solar cell designs.
The result could be a solar panel that eliminates the need for complex and expensive semiconductor structures and materials, and any surface could become a source of electricity simply by adhering a simple plastic film.
