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University Park, Pa. -- A greener, less expensive method to produce hydrogen for fuel may eventually be possible with the help of water, solar energy and nanotube diodes that use the entire spectrum of the sun's energy, according to Penn State researchers. "Other researchers have developed ways to produce hydrogen with mind-boggling efficiency, but their approaches are very high cost," says Craig A. Grimes, professor of electrical engineering. "We are working toward something that is cost effective."

"The new material provides a "stepping-stone" for electrons to move from one energy level to another as they absorb photons, allowing more photons of different energy levels (and thus different parts of the light spectrum) to be utilized. So while some efficiency research goes into breaking down what is absorbed into specific wavelengths or trapping light for greater absorption, this technology basically casts a really wide net in order to increase how much light can be captured and turned into energy."

Semiconductor solar cells absorb sunlight from the visible spectrum, ignoring ultraviolet and infrared rays, which limits how much energy a solar cell can create from sunlight. But a new material made by researchers in Spain throws titanium and vanadium into the mix so it can utilize infrared and potentially boost efficiency of solar cells.