Solar Cells Can be Built Using Any Semiconductor

Researchers at the Berkeley Lab and the University of California (UC) Berkeley found that inexpensive semiconductors can be used to create photovoltaic devices via a gate field, as long as a certain geometric shape of the electrode is maintained.

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Solar cells could be seeing much more widespread use and application as a result of research results announced by the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley. The technology is called screening-engineered field-effect photovoltaics, short SFPV. The approach utilizes the electric field effect as well as a "carefully designed partially screening top electrode" that "lets the gate electric field sufficiently penetrate the electrode and more uniformly modulate the semiconductor carrier concentration and type to induce a p-n junction."

"Our technology requires only electrode and gate deposition, without the need for high-temperature chemical doping, ion implantation, or other expensive or damaging processes," said William Regan, lead author of the study. "The key to our success is the minimal screening of the gate field which is achieved through geometric structuring of the top electrode. This makes it possible for electrical contact to and carrier modulation of the semiconductor to be performed simultaneously."

The Berkeley scientists said that they shaped the electrode contact into narrow fingers using copper oxide in one configuration and, in another configuration, they created a single-layer graphene surface. "With sufficiently narrow fingers, the gate field creates a low electrical resistance inversion layer between the fingers and a potential barrier beneath them," the researchers said. "A uniformly thin top contact allows gate fields to penetrate and deplete/invert the underlying semiconductor. This results in both configurations are high quality p-n junctions."

"Our demonstrations show that a stable, electrically contacted p-n junction can be achieved with nearly any semiconductor and any electrode material through the application of a gate field provided that the electrode is appropriately geometrically structured," Feng Wang, co-author of the study, noted.