Sharp was able to boost efficiency of the 1 square centimetre solar cell by improving the crystallinity (the regularity of the atomic arrangement) in each of the three photo-absorption layers.
Conventionally, Ge (germanium) is used as the bottom layer due to its ease of manufacturing. However, in terms of performance, although Ge generates a large amount of current, the majority of the current is wasted, without being used effectively for electrical energy. The key to solving this problem was to form the bottom layer from InGaAs (indium gallium arsenide), a material with high light utilization efficiency. However, the process to make high-quality InGaAs with high crystallinity was difficult.
Nevertheless, Sharp succeeded in forming an InGaAs layer with high crystallinity by using its proprietary technology for forming layers. As a result, the amount of wasted current has been minimized, and the conversion efficiency, which had been 31.5% in Sharp’s previous cells, has been successfully increased to 35.8%.
Sharp achieved this breakthrough as part of a research and development initiative promoted by Japan’s New Energy and Industrial Technology Development Organization (NEDO) on the theme of “R&D on Innovative Solar Cells”.
In light of these results, Sharp plans to “continue its efforts toward even greater improvements in solar cell conversion efficiency” in the future.
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