The UNSW team created a cell able to capture light at the red and infrared ends of the spectrum, converting 46% of this into electricity. This cell was combined with four others, developed by the National Renewable Energy Laboratory and Emcore Corporation, also optimised for different parts of the spectrum, and which consisted of combinations of gallium, indium, phosphorus and arsenic.
These four cells had set a previous conversion efficiency record of 42.7% in another cell from the University of Delaware. However, UNSW’s five-cell combination resulted in a 0.3% increase on this record, converting 43% of sunlight into electricity.
Professor Martin Green, research director at the UNSW ARC Photovoltaics Centre of Excellence, explained that because sunlight is made up of many colours of different energy - ranging from the high energy ultraviolet to the low energy infrared - a combination of solar cells of different materials converts sunlight more efficiently than a single cell.
The result is not directly comparable to the 25% efficiency record for an individual solar cell, set by UNSW in 2008. And Professor Green explained that last year’s result has more immediate relevance to commercial manufacturing because the progress made there can be readily transferred into current production technologies: “Because it was a laboratory result it was very expensive to put together that combination of cells but this research shows the potential of what will be feasible in the future.”