42.8% Efficiency: A New Record for Solar Cells
Narrowly edging out the previous record set by Spectrolab late last year, two scientists at the University of Delaware have just created a new device that can convert 42.8% of the light striking it into electricity. The solar cell, built by Christina Honsberg and Allan Barnett, splits light into three components — high, medium and low energy light — and directs it to several different materials which can then extract electrons out of its photons.
One of the device's key elements is an optical concentrator — a lens-type component that increases the cell's efficiency by directing more sunlight to it than would happen naturally (a boost that contributed in great measure to its record-setting performance). It measures in at just below 1 cm thick, a major improvement over the Spectrolab model which featured a concentrating lens about 1 foot thick. Unlike most concentrators that use a two-axis tracking system to follow the sun, this optical concentrator is also stationary — a major feat.The Defense Advanced Research Projects Agency (DARPA) — which has been funding this and similar efforts through its Very High Efficiency Solar Cell (VHESC) program — hopes to eventually incorporate this technology into portable solar cell battery chargers for American troops. It will now fund a newly formed DuPont-University of Delaware VHESC Consortium to shift production from a lab-scale model to a full-on manufacturing prototype model.
UPDATE: A reader wanted us to clarify an important point — namely the fact that the concentrator itself doesn't increase the efficiency (it actually increases the power output by intensifying the beam of sunlight), the spectrum splitting optics and solar cells accomplish that.