'Fill 'er up with cool, clear, water, please'

Come on, you must be kidding, I can hear you say. But in recent months, the U.S. Department of Energy (DOE; www.energy.gov) has selected more than three dozen projects to receive some $75 million in funding for research that could speed up the development of hydrogen-fueled vehicles with water-based fuel cells. Some of the winners in this highly competitive field of research are such giants as GE Global Research, Science Applications International, and the BOC Group. But tucked away in the list was a tiny optoelectronics startup based in Toledo, OH.

The researchers at MidWest OptoElectronics (or MWOE, for short) are predicting the rapid advance of their novel, highly efficient fuel cells that may provide sufficient power to recharge a compact car’s batteries overnight. Together with its partners, MWOE is in the process of developing hydrogen-based fuel-cell powered devices that would be virtually pollution free. To do so, MWOE will need to advance its optoelectronic devices in a couple of areas to get costs down to a practical level.

MWOE was founded by professors from the University of Toledo (UT) and midwestern business leaders to commercialize technologies developed at UT, particularly those developed in its Amorphous Silicon Research Laboratory. Leading the group is Prof. Xungming Deng.

The current methods used to produce hydrogen for fuel-cell applications still rely on oil and often produce significant amounts of carbon dioxide. Researchers at MWOE are committed to the development of a new renewable hydrogen-generation process; the UT group is one of only two teams with this capability in the United States, and is currently the only team that is working on direct PEC generation of hydrogen.

The amorphous silicon-based solar cells being developed at MWOE and the University of Toledo will have two different device structures: single-junction solar cells using amorphous silicon germanium as the active light-absorbing layer and triple-junction solar cells using amorphous silicon and amorphous silicon germanium. The latter devices have semiconductor bandgaps that are different from the active absorber layers. These single- and triple-junction solar cells are fabricated using lower-cost fabrication processes and exhibit higher sunlight-to-electricity conversion efficiency of on the order of 13% for both single and triple-junction solar cells. The 13% efficiency is the highest conversion efficiency in the world for single-junction amorphous silicon-based solar cells, says Deng.

Deng’s amorphous silicon-based solar cells with the triple-junction structure were tested recently by National Renewable Energy Laboratory and received the highest efficiency achieved by an academic group for this type of device. “UT clearly bested other universities in this area,” Deng said. “We really have a niche.” That niche is built in the lab by placing three solar cells stacked on top of each other on one 4 × 4-in. foil-like substrate. “The three solar cells absorb different colors of sunlight-one absorbs blue, one absorbs green, and one absorbs red,” Deng said. “In this way, they make the best use of the whole spectrum of sunlight, and the efficiency is higher.”

In addition to military interest, Deng also has received considerable attention from the auto industry. He is working with the University of Hawaii to fabricate solar cells with enough voltage to split water under sunlight to generate hydrogen, a possible future fuel. “This is one of the cleanest ways to produce hydrogen,” Deng explained. “There’s no pollution in the entire process.” Both General Motors and Ford have expressed an interest in this work. In fact, General Motors gave UT $40,000 toward the project and sent research representatives to visit Deng’s labs twice.

Meanwhile, Deng also is developing a method to make amorphous-silicon solar cells faster and cheaper with the hot wire-deposition process. “Our goal is to make high-efficiency solar cells at a higher rate,” he said. “Once we accomplish that, we hope to transfer that technology to industry for mass production of amorphous-silicon solar panels at low cost.” Ah, yes, cost is going to be a stumbling block en route to the fuel-cell automobile.