Panasonic hits 24.7% cell efficiency

12. February 2013 | Markets & Trends, Research & Development | By:  Jonathan Gifford

The Panasonic Corporation has claimed what it says is a world record for a crystalline silicon-based photovoltaic cell of a "practical size" with an efficiency of 24.7%. Japan’s Institute of Advanced Industrial Science and Technology has evaluated the efficiency.

A diagram of Panasonic's cell.

Panasonic's HIT cell efficiency trumps former equivallent cell record held by SunPower.

While photovoltaic cells produced for CPV applications have pushed efficiencies north of 40%, c-Si cells of a "practical size" are also continuing to increase efficiencies.

In the latest result, Japan’s Panasonic has produced a cell with a conversion efficiency of 24.7%. The cell utilizes Panasonic’s HIT technology and is 98 μm thick. Panasonic reports that such a thickness also has "significant implications" in terms of cost reduction.

The Panasonic HIT solar cell has a surface area of 101.8cm².

Panasonic applies a stack cell approach, where an amorphous silicon (a-Si) layer is in place on top of a monocrystalline silicon (c-Si) substrate. Key to Panasonic’s technology, the company claims, is that it's a-Si application is done so without damaging the c-Si substrate. The result is an open voltage improvement from 0.748 V to 0.750 V, according to the company statement.

A reduction in light loss has also been claimed as delivering the high efficiency cell, reports Panasonic, through developments with the conductive coating technology and the transparent a-Si layer. Shading is additionally minimized by reduction of the grid electrode surface area.

Resistive loss has further been reduced in the Panasonic cell, with a higher aspect ratio being achieved, increasing the fill factor from 0.822 to 0.832. The aspect ratio refers to the grid electrodes’, or bus bars’, height to line width ratio.

Panasonic says it will focus on applying this laboratory technology in mass production. The Wall Street Journal’s Market Watch reports Panasonic’s mass-market cells can reach efficiencies of up to 21.6%. It continues that Panasonic has commenced photovoltaic cell production in Malaysia, where it hopes to reduce costs by 20%.

The previous record for an applicable c-Si cell was 24.2% achieved by SunPower, as reported by SolarPlaza.


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