Winchester, UK - Sharp Corporation (Osaka, Japan) is claiming to have achieved the world's highest solar cell conversion efficiency of 35.8 percent using a triple-junction compound solar cell.
Sharp is developing a triple-junction compound solar cell that achieves high conversion efficiency by stacking three photo-absorption layers.
To boost the efficiency of triple-junction compound solar cells, it is important to improve the crystallinity in each photo-absorption layer. Conventionally, germanium is used as the bottom layer due to its ease of manufacturing. However, in terms of performance, although germanium generates a large amount of current, the majority of the current is wasted, without being used effectively for electrical energy. The key to solving the problem has been to form the bottom layer from InGaAs (indium gallium arsenide), a material with high light utilization efficiency. The process to make high-quality InGaAs with high crystallinity is difficult but Sharp claims to have succeeded in forming an InGaAs layer with high crystallinity by using its proprietary technology for forming layers. The new development has minimized the amount of wasted current, and the conversion efficiency, which had been 31.5 percent in Sharp's previous cells, has been successfully increased to 35.8 percent.
Sharp's breakthrough is part of a research and development initiative promoted by Japan's New Energy and Industrial Technology Development Organization (NEDO).
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