A lot of people are excited about solar energy, and with good reason: It’s clean, renewable, and as manufacturing capabilities ramp up, an increasingly realistic way to power our world. On April 30th, 2017, Germany met 85. Still, solar cells currently capture only about 25 of the available solar energy. Now a team from GW School of Engineering and Applied Science has produced a remarkably designed solar cell that collects nearly half of it. It’s been believed that the upper limit for the efficiency of conventional solar cells is about 30%, so this could be a big deal.
Scientists at GW School of Engineering and Applied Science have designed a multi-layered, stacked cell that operates as a sort of “solar sieve.” Each layer grabs a portion of the light spectrum as sunlight passes through on its way to the next layer down.
As lead author of the just-published research Matthew Lumb explains, “Around 99 percent of the power contained in direct sunlight reaching the surface of Earth falls between wavelengths of 250nm (Editor’s note: nm = nanometers) and 2500nm, but conventional materials for high-efficiency multi-junction solar cells cannot capture this entire spectral range. Our new device is able to unlock the energy stored in the long-wavelength photons, which are lost in conventional solar cells, and therefore provides a pathway to realizing the ultimate multi-junction solar cell.”
The GW team’s solar cell works with concentrator photovoltaic panels that focus sunlight onto micro-scale solar cells of about one millimeter square. Being so small opens up the possibilities for using them in sophisticated structures that can eventually be manufactured at a reasonable cost.
Aside from its stacking aspect, the GW solar cell incorporates a couple of other innovative touches.
What allows a GW panel to collect longer wavelengths is a material more commonly used with infrared lasers and photodetectors called gallium antimonide (GaSb). Cells made of this complement standard high-efficiency solar cells grown on conventional substrates.
The manner in which the GW solar cell is constructed is also a bit different. Its layers are stacked with extreme precision using a method called “transfer printing” that allows tiny three-dimensional structures to be assembled.
The GW solar cell is a one-off built to demonstrate the potential for far greater efficiency in solar energy collection.