Innovative ‘step cell’ design promises significant boost in global solar power generation
Dubai: A highly-efficient yet low-cost solar cell invented and designed in the UAE in collaboration with US engineers may soon revolutionise and even boost global solar power generation, proponents said.
A team of researchers from the Abu Dhabi-based Masdar Institute and the Massachusetts Institute of Technology (MIT) said they may have found a way to produce high-efficiency solar panels at a fraction of the cost of traditional photovoltaic (PV) panels in what they call the “step” solar cell.
The step solar cell combines two different layers of sunlight-absorbing material to harvest a broader range of the sun’s energy while using a new and cheaper manufacturing process. The institute exhibited the step-cell during the first Dubai Solar Show last week.
“We are trying to solve two problems. First, getting high-efficiency cells at a low cost. Our technology solves this problem,” Dr Ammar Nayfeh, Associate Professor of Electrical Engineering and Computer Science and a principal investigator of the step cell, told Gulf News.
Current silicon-based solar cells are relatively cheap to manufacture. But their efficiency in converting sunlight into electricity is poor at about 15 per cent to 20 per cent. To strive for high efficiency means increasing the cost because manufacturers use very expensive materials and expensive processes.
The team’s solution is to use silicon layered together with another semiconductor that could improve efficiency without compromising on costs.
“We’ve solved the problem of growing new materials on silicon by a novel approach where we have a template called silicon germanium. In addition, we invented what we call the ‘step cell’ that allows more of the solar light to hit your solar cell to give you even higher efficiency. At the same time, the step cell design allows for a cheaper fabrication,” Dr Nayfeh said.
The innovative step cell is made by layering gallium arsenide phosphide, a semiconductor material that absorbs higher energy photons on a layer of silicon. The two layers work together as a powerful solar cell that could ultimately achieve a power efficiency of 45 per cent, which is double the current technology’s output.
The idea of the step cell came from the doctoral dissertation of Bosnian student Sabina Abdul Hadi, who recently did her doctoral degree at Masdar Institute. Abdul Hadi worked under the supervision of Dr Nayfeh in testing the efficiency of their technology.
“By etching away the top layer and exposing some of the silicon layer, we were able to increase the efficiency considerably,” Abdul Hadi, who continues to support the step cell’s technological development as a post-doctoral research at the institute, said.
Dr Eugene Fitzgerald, from the Merton C. Flemings — SMA Professor of Materials Science and Engineering at MIT, is also one of the principal investigators of the project. He contributed to the project by developing the gallium arsenide phosphide. Through his innovative process, he is able to grow the silicon wafers that can be used and re-used, which reduces manufacturing cost.
Dr Nayfeh said they have made the laboratory-based prototype of the step-cell at the institute. They’re in the process of getting a patent and developing a larger scale prototype to demonstrate the higher-efficiency, low-cost panels on a larger scale.
The team is currently seeking investments to make the technology commercially available through a start-up company. He hopes to produce solar cells for space agencies for their unmanned vehicles and satellites, and the military in the future.
“There are companies who sell high-efficiency, low-cost panels to space agencies at $17 [Dh62.39] per watt. Our technology, theoretically, could see that price drop to maybe $3 per watt. There’s a huge cost reduction,” Dr Nayfeh said.
HOW IT WORKS:
1) To make the innovative “step cell”, gallium arsenide phosphide, a semiconductor material that absorbs higher energy photons, is placed on a layer of silicon. This tandem solar cell could ultimately achieve a power efficiency of more than 45 per cent.
2) The step cell creates a literal “step” between the top gallium arsenide phosphide layer and the bottom silicon layer.
3) The silicon layer juts outwards, appearing like a bottom step. This intentional step design allows the top gallium arsenide phosphide layer to absorb the high energy photons (from blue, green and yellow light) leaving the bottom silicon layer free to absorb the lower energy photons (from red light and infrared light) without any losses.
4) The unique design ensures that a greater share of the electromagnetic spectrum is absorbed, increasing the solar cell’s efficiency.
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