The National Renewable Energy Laboratory has confirmed results for a record-breaking conversion efficiency in solar cell technology. Oerlikon Solar and Corning Incorporated have combined technologies to produce a tandem solar cell using thin-film silicon. Oerlikon’s proprietary Micromorph® solar cells and Corning’s specialty, advanced light-capturing glass combined to achieve 11.9-percent stabilized conversion efficiency in NREL tests.
That efficiency beats out the previous record of 11.7 percent in 2004. This is the latest advancement in Oerlikon’s ThinFab line of solar panels, which, according to the company, have also achieved a world record in production cost per watt at 50 euro cents per watt-peak (about $0.64 USD).
Micromorph technology is itself an advancement on amorphous silicon solar cells (a-Si cells). Put simply, a-Si cells consist of a thin layer of silicon deposited onto a transparent conductive oxide (TCO). Oerlikon’s Micromorph technology adds another layer in tandem with the first. This added microcrystalline absorber enables the solar cell to absorb a wider spectrum of light, edging into the red and near-infrared spectrum which conventional silicon solar cells cannot do. According to Germany-based Oerlikon this extra absorption increases cell conversion efficiency (the rate at which sunlight is converted into electricity), by 30 percent.
Corning Inc.’s proprietary glass, or glazing, technology ensures that a higher amount of light is available for absorption by the solar cells beneath it. It is in this way that the two companies continue to make advancements in thin-film silicon.
Low production costs have long been a point of pride for thin-film technologies. Last year, American firm First Solar broke the coveted $1.00/watt barrier (now residing at about $0.76/watt) for its cadmium telluride solar cells (CdTe). Yet low conversion efficiency has been the only factor preventing thin-film products from surpassing their crystalline silicon predecessors, which still dominate more than 90 percent of the global solar market.
However, with efficiencies nearing 12 percent and production costs approaching a half dollar, the gap continues to close between first- and second-generation technologies. Most crystalline silicon (c-Si) modules on the market produce at efficiencies between 15 and 20 percent, but cost well over $1.00 per watt to manufacture. a-Si products use much less silicon and are cheaper to produce than conventional panels. It’s for this reason — and based on advancements such as Oerlikon and Corning’s — that thin-film solar cells are expected to take over dominance of the solar market within the next decade, depending on a variety of technological and commercial factors.
Oerlikon Solar is presenting its record-breaking Micromorph technology this week at the 25th Annual European Photovoltaics Solar Energy Conference in Valencia, Spain.