German solar technology specialist Heliatek has set a new benchmark for the efficiency of organic solar cells. In independent tests, a new world record efficiency of 10.7 percent was achieved for the company's latest tandem organic photovoltaic (OPV) cells ... and 15 percent may be just a few years away.
Organic solar cells are cheaper to produce, lighter and more flexible than traditional silicon-based solar cells, and therefore have a wider range of applications.
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The downside is that the efficiency rate of OPV cells is still much lower than inorganic solar cells, which are around 15 - 20 percent efficient (though that number is growing).
The organic solar tandem cells developed by Heliatek incorporate small organic molecules called oligomers, which are deposited into the thin layers of solar film using a low temperature, roll-to-roll vacuum process.
“This enables us to literally engineer the cell architecture to systematically improve efficiency and lifetime.” Says Dr. Martin Pfeiffer, co-founder and CTO of Heliatek.
In tests conducted by accredited testing facility SGS, the efficiency of the OPV cell was measured in standard testing conditions which resulted in the record 10.7 percent efficiency on 1.1 cm².
The technology also performed well in low light and high temperatures of up to 80 degrees Celsius. The results at low light showed that the OPV cell’s efficiency not only remained constant, but actually increased. The efficiency was 15% higher at an irradiation of 100 W/m², compared with the efficiency measured at 1000 W/m². The tests also found that when efficiency was measured at high temperatures it remained constant.
These measurements are surprising when compared to inorganic solar cells, which lose 15 to 20 percent efficiency when exposed to elevated temperatures.
Heliatek says these findings add up to a higher harvesting factor under real life conditions than crystalline and thin film solar technologies.
“Thanks to the close cooperation between our research teams in chemistry and physics, we are now on our path to achieving 15 percent efficiency within the next few years,” says CEO of Heliatek, Thibaud Le Séguillon.
The company’s first roll-to-roll manufacturing line in Dresden which is due to go into production in late 2012.