In 2002, Wladek Walukiewicz and Kin Man Yu of the Lawrence Berkeley National Laboratory’s Material Sciences Division stacked crystalline layers with closely matched but slightly different levels of indium content, and made a photovoltaic device that was sensitive to the full solar spectrum. Had they conquered the longstanding challenge of finding a way to make more of the sun’s light available for conduction? Not quite. Their complex solar cell wasn’t viable for manufacture.
So the work went on, and on, and on … until now. Now, according to the Berkeley Lab, Walukiewicz and his team have hit on a new design that “promises highly efficient solar cells that are practical to produce.”
This work on capturing more of the light spectrum is all about the band gaps, also known as energy gaps. The nature of these gaps determines which of the sun’s varying wavelengths are conducted by the semiconductor.
Walukiewicz and his team worked with RoseStreet Labs Energy and Sumika Electronics Materials in Phoenix, Ariz., to come up with a multiband semiconductor made from a highly mismatched alloy – gallium arsenide nitride. It gives the semiconductor the ability to respond to virtually the entire spectrum.
And – here’s the real breakthrough – making gallium arsenide nitride isn’t difficult: The alloy, the Berkeley Lab said, “can be made by metalorganic chemical vapor deposition (MOCVD), one of the most common methods of fabricating compound semiconductors.”