"The maximum voltage conventional solid-state photovoltaic devices can produce is equal to the energy of their electronic bandgap," Seidel says. "Even for so called tandem-cells, in which several semiconductor p-n junctions are stacked, photovoltages are still limited because of the finite penetration depth of light into the material."
Working through Berkeley Lab's Helios Solar Energy Research Center, Seidel and his collaborators discovered that by applying white light to bismuth ferrite, a material that is both ferroelectric and antiferromagnetic, they could generate photovoltages within submicroscopic areas between one and two nanometers across. These photovoltages were significantly higher than bismuth ferrite's electronic bandgap.
"The bandgap energy of the bismuth ferrite is equivalent to 2.7 volts. From our measurements we know that with our mechanism we can get approximately 16 volts over a distance of 200 microns. Furthermore, this voltage is in principle linear scalable, which means that larger distances should lead to higher voltages."
Behind this new mechanism for photovoltage generation are domain walls two-dimensional sheets that run through a multiferroic and serve as transition zones, separating regions of different ferromagnetic or ferroelectric properties. In their study, Seidel and his collaborators found that these domain walls can serve the same electron-hole separation purpose as depletio
|Contact: Lynn Yarris|
DOE/Lawrence Berkeley National Laboratory