Panasonic is reporting a 25.6 percent conversion efficiency for its HIT (Heterojunction with Intrinsic Thin layer) solar cells. This is an improvement of 0.9 percentage points over the 24.7 percent conversion efficiency Panasonic achieved in February 2013, with the company claiming it as a world record for crystalline silicon-based solar cells of a "practical size."
Panasonic classifies a "practical size" as cells with an area of over 100 cm2 (15.5 in2). The February 2013 record was achieved on a solar cell with an area of 101.8 cm2 (15.7 in2), while this new 25.6 percent efficiency was achieved on a solar cell measuring 143 cm2 (22.1 in2).
However, Panasonic says the latest achievement is also an improvement over the previous record of 25 percent for small area crystalline silicon-based solar cells accomplished on solar cells measuring 4 cm2 (0.6 in2). This is still short of the efficiencies seen in multi-junction solar cells and concentrator triple-junction compound solar cells that have reached conversion efficiencies of 38.8 percent and 44.4 percent, respectively.
The company says the new record was made possible through further development of its proprietary heterojunction technology, which involves laminating layers of high-quality amorphous silicon onto a monocrystalline silicon substrate. This results in a solar cell that Panasonic claims can maintain efficiency at higher temperatures.
Additionally, unlike the 24.7 percent efficiency solar cells, the new record holders have the electrodes placed on the reverse of the panel as back contacts, allowing the light hitting the cell's surface to be more efficiently directed to the monocrystalline silicon substrate where power is generated. Placing the electrodes on the reverse side has also allowed the resistive loss when the current is fed to the grid electrodes to be reduced.
Panasonic says it will work towards mass production of its high efficiency HIT solar cells, as it continues to aim for higher efficiency, lower costs and more efficient use of resources.
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