Panasonic HIT Solar Cell Achieves World’s Highest Conversion Efficiency of 24.7% at Research Level
Panasonic Corporation today announced it has achieved a record conversion efficiency of 24.7% at the research level, using its HIT solar cell at 98 micro-m thickness. The rate is the world’s highest for any crystalline silicon-based solar cell of practical size (100 cm2 and above).
This record conversion rate demonstrates superb efficiency of Panasonic HIT solar cells to convert sunlight into electricity. The latest figure is 0.8 percentage points higher than the previous record (23.9%) for HIT solar cells, and 0.5 percentage points higher than the previously published record for any monocrystalline silicon-based solar cell of practical size (100 cm2 and above).
Further, achieving this high efficiency at the very thin thickness of 98 micro-m has significant implications in terms of cost reduction as Panasonic continues to improve efficiency of its solar cells while lowering costs, with the aim to set itself apart from other companies in the industry.
Core technologies behind the record efficiency rating:
Reduction in recombination loss. A key feature of HIT solar cells is the lamination of a high-quality amorphous silicon layer onto the surface of the monocrystalline silicon substrate that serves as the power-generating layer. This leads to a reduction in recombination loss within the electrical elements, known as carriers. To further enhance this unique property of HIT solar cells, Panasonic has developed a new technology that enables an amorphous silicon layer of even higher quality to form on the monocrystalline silicon substrate while limiting damage to the surface of the substrate. This has enabled a further reduction of recombination losses within the carrier. As a result, the open voltage (Voc) has been improved from 0.748 V to 0.750 V.
Reduction in optical loss. In order to achieve a high electrical current from solar cells, it is necessary to induce the solar rays arriving at the cell surface into the monocrystalline silicon substrate that serves as the power-generating layer with as little loss as possible. This time, using an HIT solar cell, Panasonic has successfully reduced absorption loss of light in the transparent conductive coatings and the amorphous silicon layer covering the monocrystalline silicon substrate. At the same time, shading loss has also been decreased by reducing the surface area of the grid electrode on the cell surface. As a result, density of the short-circuit current (Jsc)(7) has been improved from 38.9 mA/cm2 to 39.5 mA/cm2.
Reduction in resistive loss. In solar cells, the electrical current generated is accumulated within the grid electrode on the cell surface and then delivered outside. This time, Panasonic has succeeded in cutting down resistive loss that occurs when an electric current passes through the grid electrode by improving the grid electrode, including the development of an electrode with a higher aspect ratio. As a result, the fill factor (FF) has been improved from 0.822 to 0.832.
Panasonic will focus on applying this newly developed high-efficiency technology to mass production products, and will continue to develop technologies that improve efficiency, reduce costs, and save resources further.
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