Engineers from the University of Illinois at Urbana-Champaign have developed a new type of solar cell that uses multiple junctions instead of single subcells to gather the full spectrum of light. The panels are able to capture different wavelengths of sunlight, so they can achieve power conversion efficiencies of 44% as compared to the 29% of standard panels.
The solar cell project is headed by Professor John Rogers, who worked in collaboration with Semprius and Solar Junction. The team was able to use a printing technique to lay extremely small and thin layers of semiconductor elements on top of one another. The high-speed process yields quadruple junction, four terminal solar cells that can harvest a greater diversity of sunlight. Semprius incorporated the invention into their dual-stage optics, which are able to concentrate incident light more than one thousand times. Semiconductor materials were used for the top three layers, while germanium comprised the bottom.
The solar panels’ lattice-like composition requires the junctions to be matched exactly. As the number of junctions increase, the precision becomes more difficult to obtain. Rogers and his team have created methods that help avoid interface reflections, poor heat flow, and thermomechanical stress. As they progress, the group expects to manufacture cells with five or six junctions, making them even more powerful.
Images via University of Illinois at Urbana Champaign